/* Alias analysis for GNU C Copyright (C) 1997-2015 Free Software Foundation, Inc. Contributed by John Carr (jfc@mit.edu). This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see . */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "rtl.h" #include "input.h" #include "alias.h" #include "symtab.h" #include "tree.h" #include "fold-const.h" #include "varasm.h" #include "hard-reg-set.h" #include "function.h" #include "flags.h" #include "insn-config.h" #include "expmed.h" #include "dojump.h" #include "explow.h" #include "calls.h" #include "emit-rtl.h" #include "stmt.h" #include "expr.h" #include "tm_p.h" #include "regs.h" #include "diagnostic-core.h" #include "alloc-pool.h" #include "cselib.h" #include "langhooks.h" #include "timevar.h" #include "dumpfile.h" #include "target.h" #include "dominance.h" #include "cfg.h" #include "cfganal.h" #include "predict.h" #include "basic-block.h" #include "df.h" #include "tree-ssa-alias.h" #include "internal-fn.h" #include "gimple-expr.h" #include "is-a.h" #include "gimple.h" #include "gimple-ssa.h" #include "rtl-iter.h" /* The aliasing API provided here solves related but different problems: Say there exists (in c) struct X { struct Y y1; struct Z z2; } x1, *px1, *px2; struct Y y2, *py; struct Z z2, *pz; py = &x1.y1; px2 = &x1; Consider the four questions: Can a store to x1 interfere with px2->y1? Can a store to x1 interfere with px2->z2? Can a store to x1 change the value pointed to by with py? Can a store to x1 change the value pointed to by with pz? The answer to these questions can be yes, yes, yes, and maybe. The first two questions can be answered with a simple examination of the type system. If structure X contains a field of type Y then a store through a pointer to an X can overwrite any field that is contained (recursively) in an X (unless we know that px1 != px2). The last two questions can be solved in the same way as the first two questions but this is too conservative. The observation is that in some cases we can know which (if any) fields are addressed and if those addresses are used in bad ways. This analysis may be language specific. In C, arbitrary operations may be applied to pointers. However, there is some indication that this may be too conservative for some C++ types. The pass ipa-type-escape does this analysis for the types whose instances do not escape across the compilation boundary. Historically in GCC, these two problems were combined and a single data structure that was used to represent the solution to these problems. We now have two similar but different data structures, The data structure to solve the last two questions is similar to the first, but does not contain the fields whose address are never taken. For types that do escape the compilation unit, the data structures will have identical information. */ /* The alias sets assigned to MEMs assist the back-end in determining which MEMs can alias which other MEMs. In general, two MEMs in different alias sets cannot alias each other, with one important exception. Consider something like: struct S { int i; double d; }; a store to an `S' can alias something of either type `int' or type `double'. (However, a store to an `int' cannot alias a `double' and vice versa.) We indicate this via a tree structure that looks like: struct S / \ / \ |/_ _\| int double (The arrows are directed and point downwards.) In this situation we say the alias set for `struct S' is the `superset' and that those for `int' and `double' are `subsets'. To see whether two alias sets can point to the same memory, we must see if either alias set is a subset of the other. We need not trace past immediate descendants, however, since we propagate all grandchildren up one level. Alias set zero is implicitly a superset of all other alias sets. However, this is no actual entry for alias set zero. It is an error to attempt to explicitly construct a subset of zero. */ struct alias_set_traits : default_hashmap_traits { template static bool is_empty (T &e) { return e.m_key == INT_MIN; } template static bool is_deleted (T &e) { return e.m_key == (INT_MIN + 1); } template static void mark_empty (T &e) { e.m_key = INT_MIN; } template static void mark_deleted (T &e) { e.m_key = INT_MIN + 1; } }; struct GTY(()) alias_set_entry_d { /* The alias set number, as stored in MEM_ALIAS_SET. */ alias_set_type alias_set; /* The children of the alias set. These are not just the immediate children, but, in fact, all descendants. So, if we have: struct T { struct S s; float f; } continuing our example above, the children here will be all of `int', `double', `float', and `struct S'. */ hash_map *children; /* Nonzero if would have a child of zero: this effectively makes this alias set the same as alias set zero. */ bool has_zero_child; /* Nonzero if alias set corresponds to pointer type itself (i.e. not to aggregate contaiing pointer. This is used for a special case where we need an universal pointer type compatible with all other pointer types. */ bool is_pointer; /* Nonzero if is_pointer or if one of childs have has_pointer set. */ bool has_pointer; }; typedef struct alias_set_entry_d *alias_set_entry; static int rtx_equal_for_memref_p (const_rtx, const_rtx); static int memrefs_conflict_p (int, rtx, int, rtx, HOST_WIDE_INT); static void record_set (rtx, const_rtx, void *); static int base_alias_check (rtx, rtx, rtx, rtx, machine_mode, machine_mode); static rtx find_base_value (rtx); static int mems_in_disjoint_alias_sets_p (const_rtx, const_rtx); static alias_set_entry get_alias_set_entry (alias_set_type); static tree decl_for_component_ref (tree); static int write_dependence_p (const_rtx, const_rtx, machine_mode, rtx, bool, bool, bool); static void memory_modified_1 (rtx, const_rtx, void *); /* Query statistics for the different low-level disambiguators. A high-level query may trigger multiple of them. */ static struct { unsigned long long num_alias_zero; unsigned long long num_same_alias_set; unsigned long long num_same_objects; unsigned long long num_volatile; unsigned long long num_dag; unsigned long long num_universal; unsigned long long num_disambiguated; } alias_stats; /* Set up all info needed to perform alias analysis on memory references. */ /* Returns the size in bytes of the mode of X. */ #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X))) /* Cap the number of passes we make over the insns propagating alias information through set chains. ??? 10 is a completely arbitrary choice. This should be based on the maximum loop depth in the CFG, but we do not have this information available (even if current_loops _is_ available). */ #define MAX_ALIAS_LOOP_PASSES 10 /* reg_base_value[N] gives an address to which register N is related. If all sets after the first add or subtract to the current value or otherwise modify it so it does not point to a different top level object, reg_base_value[N] is equal to the address part of the source of the first set. A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS expressions represent three types of base: 1. incoming arguments. There is just one ADDRESS to represent all arguments, since we do not know at this level whether accesses based on different arguments can alias. The ADDRESS has id 0. 2. stack_pointer_rtx, frame_pointer_rtx, hard_frame_pointer_rtx (if distinct from frame_pointer_rtx) and arg_pointer_rtx. Each of these rtxes has a separate ADDRESS associated with it, each with a negative id. GCC is (and is required to be) precise in which register it chooses to access a particular region of stack. We can therefore assume that accesses based on one of these rtxes do not alias accesses based on another of these rtxes. 3. bases that are derived from malloc()ed memory (REG_NOALIAS). Each such piece of memory has a separate ADDRESS associated with it, each with an id greater than 0. Accesses based on one ADDRESS do not alias accesses based on other ADDRESSes. Accesses based on ADDRESSes in groups (2) and (3) do not alias globals either; the ADDRESSes have Pmode to indicate this. The ADDRESS in group (1) _may_ alias globals; it has VOIDmode to indicate this. */ static GTY(()) vec *reg_base_value; static rtx *new_reg_base_value; /* The single VOIDmode ADDRESS that represents all argument bases. It has id 0. */ static GTY(()) rtx arg_base_value; /* Used to allocate unique ids to each REG_NOALIAS ADDRESS. */ static int unique_id; /* We preserve the copy of old array around to avoid amount of garbage produced. About 8% of garbage produced were attributed to this array. */ static GTY((deletable)) vec *old_reg_base_value; /* Values of XINT (address, 0) of Pmode ADDRESS rtxes for special registers. */ #define UNIQUE_BASE_VALUE_SP -1 #define UNIQUE_BASE_VALUE_ARGP -2 #define UNIQUE_BASE_VALUE_FP -3 #define UNIQUE_BASE_VALUE_HFP -4 #define static_reg_base_value \ (this_target_rtl->x_static_reg_base_value) #define REG_BASE_VALUE(X) \ (REGNO (X) < vec_safe_length (reg_base_value) \ ? (*reg_base_value)[REGNO (X)] : 0) /* Vector indexed by N giving the initial (unchanging) value known for pseudo-register N. This vector is initialized in init_alias_analysis, and does not change until end_alias_analysis is called. */ static GTY(()) vec *reg_known_value; /* Vector recording for each reg_known_value whether it is due to a REG_EQUIV note. Future passes (viz., reload) may replace the pseudo with the equivalent expression and so we account for the dependences that would be introduced if that happens. The REG_EQUIV notes created in assign_parms may mention the arg pointer, and there are explicit insns in the RTL that modify the arg pointer. Thus we must ensure that such insns don't get scheduled across each other because that would invalidate the REG_EQUIV notes. One could argue that the REG_EQUIV notes are wrong, but solving the problem in the scheduler will likely give better code, so we do it here. */ static sbitmap reg_known_equiv_p; /* True when scanning insns from the start of the rtl to the NOTE_INSN_FUNCTION_BEG note. */ static bool copying_arguments; /* The splay-tree used to store the various alias set entries. */ static GTY (()) vec *alias_sets; /* Build a decomposed reference object for querying the alias-oracle from the MEM rtx and store it in *REF. Returns false if MEM is not suitable for the alias-oracle. */ static bool ao_ref_from_mem (ao_ref *ref, const_rtx mem) { tree expr = MEM_EXPR (mem); tree base; if (!expr) return false; ao_ref_init (ref, expr); /* Get the base of the reference and see if we have to reject or adjust it. */ base = ao_ref_base (ref); if (base == NULL_TREE) return false; /* The tree oracle doesn't like bases that are neither decls nor indirect references of SSA names. */ if (!(DECL_P (base) || (TREE_CODE (base) == MEM_REF && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME) || (TREE_CODE (base) == TARGET_MEM_REF && TREE_CODE (TMR_BASE (base)) == SSA_NAME))) return false; /* If this is a reference based on a partitioned decl replace the base with a MEM_REF of the pointer representative we created during stack slot partitioning. */ if (TREE_CODE (base) == VAR_DECL && ! is_global_var (base) && cfun->gimple_df->decls_to_pointers != NULL) { tree *namep = cfun->gimple_df->decls_to_pointers->get (base); if (namep) ref->base = build_simple_mem_ref (*namep); } ref->ref_alias_set = MEM_ALIAS_SET (mem); /* If MEM_OFFSET or MEM_SIZE are unknown what we got from MEM_EXPR is conservative, so trust it. */ if (!MEM_OFFSET_KNOWN_P (mem) || !MEM_SIZE_KNOWN_P (mem)) return true; /* If the base decl is a parameter we can have negative MEM_OFFSET in case of promoted subregs on bigendian targets. Trust the MEM_EXPR here. */ if (MEM_OFFSET (mem) < 0 && (MEM_SIZE (mem) + MEM_OFFSET (mem)) * BITS_PER_UNIT == ref->size) return true; /* Otherwise continue and refine size and offset we got from analyzing MEM_EXPR by using MEM_SIZE and MEM_OFFSET. */ ref->offset += MEM_OFFSET (mem) * BITS_PER_UNIT; ref->size = MEM_SIZE (mem) * BITS_PER_UNIT; /* The MEM may extend into adjacent fields, so adjust max_size if necessary. */ if (ref->max_size != -1 && ref->size > ref->max_size) ref->max_size = ref->size; /* If MEM_OFFSET and MEM_SIZE get us outside of the base object of the MEM_EXPR punt. This happens for STRICT_ALIGNMENT targets a lot. */ if (MEM_EXPR (mem) != get_spill_slot_decl (false) && (ref->offset < 0 || (DECL_P (ref->base) && (DECL_SIZE (ref->base) == NULL_TREE || TREE_CODE (DECL_SIZE (ref->base)) != INTEGER_CST || wi::ltu_p (wi::to_offset (DECL_SIZE (ref->base)), ref->offset + ref->size))))) return false; return true; } /* Query the alias-oracle on whether the two memory rtx X and MEM may alias. If TBAA_P is set also apply TBAA. Returns true if the two rtxen may alias, false otherwise. */ static bool rtx_refs_may_alias_p (const_rtx x, const_rtx mem, bool tbaa_p) { ao_ref ref1, ref2; if (!ao_ref_from_mem (&ref1, x) || !ao_ref_from_mem (&ref2, mem)) return true; return refs_may_alias_p_1 (&ref1, &ref2, tbaa_p && MEM_ALIAS_SET (x) != 0 && MEM_ALIAS_SET (mem) != 0); } /* Returns a pointer to the alias set entry for ALIAS_SET, if there is such an entry, or NULL otherwise. */ static inline alias_set_entry get_alias_set_entry (alias_set_type alias_set) { return (*alias_sets)[alias_set]; } /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that the two MEMs cannot alias each other. */ static inline int mems_in_disjoint_alias_sets_p (const_rtx mem1, const_rtx mem2) { return (flag_strict_aliasing && ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2))); } /* Return true if the first alias set is a subset of the second. */ bool alias_set_subset_of (alias_set_type set1, alias_set_type set2) { alias_set_entry ase2; /* Everything is a subset of the "aliases everything" set. */ if (set2 == 0) return true; /* Check if set1 is a subset of set2. */ ase2 = get_alias_set_entry (set2); if (ase2 != 0 && (ase2->has_zero_child || (ase2->children && ase2->children->get (set1)))) return true; /* As a special case we consider alias set of "void *" to be both subset and superset of every alias set of a pointer. This extra symmetry does not matter for alias_sets_conflict_p but it makes aliasing_component_refs_p to return true on the following testcase: void *ptr; char **ptr2=(char **)&ptr; *ptr2 = ... Additionally if a set contains universal pointer, we consider every pointer to be a subset of it, but we do not represent this explicitely - doing so would require us to update transitive closure each time we introduce new pointer type. This makes aliasing_component_refs_p to return true on the following testcase: struct a {void *ptr;} char **ptr = (char **)&a.ptr; ptr = ... This makes void * truly universal pointer type. See pointer handling in get_alias_set for more details. */ if (ase2 && ase2->has_pointer) { alias_set_entry ase1 = get_alias_set_entry (set1); if (ase1 && ase1->is_pointer) { alias_set_type voidptr_set = TYPE_ALIAS_SET (ptr_type_node); /* If one is ptr_type_node and other is pointer, then we consider them subset of each other. */ if (set1 == voidptr_set || set2 == voidptr_set) return true; /* If SET2 contains universal pointer's alias set, then we consdier every (non-universal) pointer. */ if (ase2->children && set1 != voidptr_set && ase2->children->get (voidptr_set)) return true; } } return false; } /* Return 1 if the two specified alias sets may conflict. */ int alias_sets_conflict_p (alias_set_type set1, alias_set_type set2) { alias_set_entry ase1; alias_set_entry ase2; /* The easy case. */ if (alias_sets_must_conflict_p (set1, set2)) return 1; /* See if the first alias set is a subset of the second. */ ase1 = get_alias_set_entry (set1); if (ase1 != 0 && ase1->children && ase1->children->get (set2)) { ++alias_stats.num_dag; return 1; } /* Now do the same, but with the alias sets reversed. */ ase2 = get_alias_set_entry (set2); if (ase2 != 0 && ase2->children && ase2->children->get (set1)) { ++alias_stats.num_dag; return 1; } /* We want void * to be compatible with any other pointer without really dropping it to alias set 0. Doing so would make it compatible with all non-pointer types too. This is not strictly necessary by the C/C++ language standards, but avoids common type punning mistakes. In addition to that, we need the existence of such universal pointer to implement Fortran's C_PTR type (which is defined as type compatible with all C pointers). */ if (ase1 && ase2 && ase1->has_pointer && ase2->has_pointer) { alias_set_type voidptr_set = TYPE_ALIAS_SET (ptr_type_node); /* If one of the sets corresponds to universal pointer, we consider it to conflict with anything that is or contains pointer. */ if (set1 == voidptr_set || set2 == voidptr_set) { ++alias_stats.num_universal; return true; } /* If one of sets is (non-universal) pointer and the other contains universal pointer, we also get conflict. */ if (ase1->is_pointer && set2 != voidptr_set && ase2->children && ase2->children->get (voidptr_set)) { ++alias_stats.num_universal; return true; } if (ase2->is_pointer && set1 != voidptr_set && ase1->children && ase1->children->get (voidptr_set)) { ++alias_stats.num_universal; return true; } } ++alias_stats.num_disambiguated; /* The two alias sets are distinct and neither one is the child of the other. Therefore, they cannot conflict. */ return 0; } /* Return 1 if the two specified alias sets will always conflict. */ int alias_sets_must_conflict_p (alias_set_type set1, alias_set_type set2) { if (set1 == 0 || set2 == 0) { ++alias_stats.num_alias_zero; return 1; } if (set1 == set2) { ++alias_stats.num_same_alias_set; return 1; } return 0; } /* Return 1 if any MEM object of type T1 will always conflict (using the dependency routines in this file) with any MEM object of type T2. This is used when allocating temporary storage. If T1 and/or T2 are NULL_TREE, it means we know nothing about the storage. */ int objects_must_conflict_p (tree t1, tree t2) { alias_set_type set1, set2; /* If neither has a type specified, we don't know if they'll conflict because we may be using them to store objects of various types, for example the argument and local variables areas of inlined functions. */ if (t1 == 0 && t2 == 0) return 0; /* If they are the same type, they must conflict. */ if (t1 == t2) { ++alias_stats.num_same_objects; return 1; } /* Likewise if both are volatile. */ if (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)) { ++alias_stats.num_volatile; return 1; } set1 = t1 ? get_alias_set (t1) : 0; set2 = t2 ? get_alias_set (t2) : 0; /* We can't use alias_sets_conflict_p because we must make sure that every subtype of t1 will conflict with every subtype of t2 for which a pair of subobjects of these respective subtypes overlaps on the stack. */ return alias_sets_must_conflict_p (set1, set2); } /* Return the outermost parent of component present in the chain of component references handled by get_inner_reference in T with the following property: - the component is non-addressable, or - the parent has alias set zero, or NULL_TREE if no such parent exists. In the former cases, the alias set of this parent is the alias set that must be used for T itself. */ tree component_uses_parent_alias_set_from (const_tree t) { const_tree found = NULL_TREE; while (handled_component_p (t)) { switch (TREE_CODE (t)) { case COMPONENT_REF: if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1))) found = t; break; case ARRAY_REF: case ARRAY_RANGE_REF: if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0)))) found = t; break; case REALPART_EXPR: case IMAGPART_EXPR: break; case BIT_FIELD_REF: case VIEW_CONVERT_EXPR: /* Bitfields and casts are never addressable. */ found = t; break; default: gcc_unreachable (); } if (get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) == 0) found = t; t = TREE_OPERAND (t, 0); } if (found) return TREE_OPERAND (found, 0); return NULL_TREE; } /* Return whether the pointer-type T effective for aliasing may access everything and thus the reference has to be assigned alias-set zero. */ static bool ref_all_alias_ptr_type_p (const_tree t) { return (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE || TYPE_REF_CAN_ALIAS_ALL (t)); } /* Return the alias set for the memory pointed to by T, which may be either a type or an expression. Return -1 if there is nothing special about dereferencing T. */ static alias_set_type get_deref_alias_set_1 (tree t) { /* All we care about is the type. */ if (! TYPE_P (t)) t = TREE_TYPE (t); /* If we have an INDIRECT_REF via a void pointer, we don't know anything about what that might alias. Likewise if the pointer is marked that way. */ if (ref_all_alias_ptr_type_p (t)) return 0; return -1; } /* Return the alias set for the memory pointed to by T, which may be either a type or an expression. */ alias_set_type get_deref_alias_set (tree t) { /* If we're not doing any alias analysis, just assume everything aliases everything else. */ if (!flag_strict_aliasing) return 0; alias_set_type set = get_deref_alias_set_1 (t); /* Fall back to the alias-set of the pointed-to type. */ if (set == -1) { if (! TYPE_P (t)) t = TREE_TYPE (t); set = get_alias_set (TREE_TYPE (t)); } return set; } /* Return the pointer-type relevant for TBAA purposes from the memory reference tree *T or NULL_TREE in which case *T is adjusted to point to the outermost component reference that can be used for assigning an alias set. */ static tree reference_alias_ptr_type_1 (tree *t) { tree inner; /* Get the base object of the reference. */ inner = *t; while (handled_component_p (inner)) { /* If there is a VIEW_CONVERT_EXPR in the chain we cannot use the type of any component references that wrap it to determine the alias-set. */ if (TREE_CODE (inner) == VIEW_CONVERT_EXPR) *t = TREE_OPERAND (inner, 0); inner = TREE_OPERAND (inner, 0); } /* Handle pointer dereferences here, they can override the alias-set. */ if (INDIRECT_REF_P (inner) && ref_all_alias_ptr_type_p (TREE_TYPE (TREE_OPERAND (inner, 0)))) return TREE_TYPE (TREE_OPERAND (inner, 0)); else if (TREE_CODE (inner) == TARGET_MEM_REF) return TREE_TYPE (TMR_OFFSET (inner)); else if (TREE_CODE (inner) == MEM_REF && ref_all_alias_ptr_type_p (TREE_TYPE (TREE_OPERAND (inner, 1)))) return TREE_TYPE (TREE_OPERAND (inner, 1)); /* If the innermost reference is a MEM_REF that has a conversion embedded treat it like a VIEW_CONVERT_EXPR above, using the memory access type for determining the alias-set. */ if (TREE_CODE (inner) == MEM_REF && (TYPE_MAIN_VARIANT (TREE_TYPE (inner)) != TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (TREE_OPERAND (inner, 1)))))) return TREE_TYPE (TREE_OPERAND (inner, 1)); /* Otherwise, pick up the outermost object that we could have a pointer to. */ tree tem = component_uses_parent_alias_set_from (*t); if (tem) *t = tem; return NULL_TREE; } /* Return the pointer-type relevant for TBAA purposes from the gimple memory reference tree T. This is the type to be used for the offset operand of MEM_REF or TARGET_MEM_REF replacements of T and guarantees that get_alias_set will return the same alias set for T and the replacement. */ tree reference_alias_ptr_type (tree t) { tree ptype = reference_alias_ptr_type_1 (&t); /* If there is a given pointer type for aliasing purposes, return it. */ if (ptype != NULL_TREE) return ptype; /* Otherwise build one from the outermost component reference we may use. */ if (TREE_CODE (t) == MEM_REF || TREE_CODE (t) == TARGET_MEM_REF) return TREE_TYPE (TREE_OPERAND (t, 1)); else return build_pointer_type (TYPE_MAIN_VARIANT (TREE_TYPE (t))); } /* Return whether the pointer-types T1 and T2 used to determine two alias sets of two references will yield the same answer from get_deref_alias_set. */ bool alias_ptr_types_compatible_p (tree t1, tree t2) { if (TYPE_MAIN_VARIANT (t1) == TYPE_MAIN_VARIANT (t2)) return true; if (ref_all_alias_ptr_type_p (t1) || ref_all_alias_ptr_type_p (t2)) return false; return (TYPE_MAIN_VARIANT (TREE_TYPE (t1)) == TYPE_MAIN_VARIANT (TREE_TYPE (t2))); } /* Create emptry alias set entry. */ alias_set_entry init_alias_set_entry (alias_set_type set) { alias_set_entry ase = ggc_alloc (); ase->alias_set = set; ase->children = NULL; ase->has_zero_child = false; ase->is_pointer = false; ase->has_pointer = false; gcc_checking_assert (!get_alias_set_entry (set)); (*alias_sets)[set] = ase; return ase; } /* Return the alias set for T, which may be either a type or an expression. Call language-specific routine for help, if needed. */ alias_set_type get_alias_set (tree t) { alias_set_type set; /* If we're not doing any alias analysis, just assume everything aliases everything else. Also return 0 if this or its type is an error. */ if (! flag_strict_aliasing || t == error_mark_node || (! TYPE_P (t) && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node))) return 0; /* We can be passed either an expression or a type. This and the language-specific routine may make mutually-recursive calls to each other to figure out what to do. At each juncture, we see if this is a tree that the language may need to handle specially. First handle things that aren't types. */ if (! TYPE_P (t)) { /* Give the language a chance to do something with this tree before we look at it. */ STRIP_NOPS (t); set = lang_hooks.get_alias_set (t); if (set != -1) return set; /* Get the alias pointer-type to use or the outermost object that we could have a pointer to. */ tree ptype = reference_alias_ptr_type_1 (&t); if (ptype != NULL) return get_deref_alias_set (ptype); /* If we've already determined the alias set for a decl, just return it. This is necessary for C++ anonymous unions, whose component variables don't look like union members (boo!). */ if (TREE_CODE (t) == VAR_DECL && DECL_RTL_SET_P (t) && MEM_P (DECL_RTL (t))) return MEM_ALIAS_SET (DECL_RTL (t)); /* Now all we care about is the type. */ t = TREE_TYPE (t); } /* Variant qualifiers don't affect the alias set, so get the main variant. */ t = TYPE_MAIN_VARIANT (t); /* Always use the canonical type as well. If this is a type that requires structural comparisons to identify compatible types use alias set zero. */ if (TYPE_STRUCTURAL_EQUALITY_P (t)) { /* Allow the language to specify another alias set for this type. */ set = lang_hooks.get_alias_set (t); if (set != -1) return set; return 0; } t = TYPE_CANONICAL (t); /* The canonical type should not require structural equality checks. */ gcc_checking_assert (!TYPE_STRUCTURAL_EQUALITY_P (t)); /* If this is a type with a known alias set, return it. */ if (TYPE_ALIAS_SET_KNOWN_P (t)) return TYPE_ALIAS_SET (t); /* We don't want to set TYPE_ALIAS_SET for incomplete types. */ if (!COMPLETE_TYPE_P (t)) { /* For arrays with unknown size the conservative answer is the alias set of the element type. */ if (TREE_CODE (t) == ARRAY_TYPE) return get_alias_set (TREE_TYPE (t)); /* But return zero as a conservative answer for incomplete types. */ return 0; } /* See if the language has special handling for this type. */ set = lang_hooks.get_alias_set (t); if (set != -1) return set; /* There are no objects of FUNCTION_TYPE, so there's no point in using up an alias set for them. (There are, of course, pointers and references to functions, but that's different.) */ else if (TREE_CODE (t) == FUNCTION_TYPE || TREE_CODE (t) == METHOD_TYPE) set = 0; /* Unless the language specifies otherwise, let vector types alias their components. This avoids some nasty type punning issues in normal usage. And indeed lets vectors be treated more like an array slice. */ else if (TREE_CODE (t) == VECTOR_TYPE) set = get_alias_set (TREE_TYPE (t)); /* Unless the language specifies otherwise, treat array types the same as their components. This avoids the asymmetry we get through recording the components. Consider accessing a character(kind=1) through a reference to a character(kind=1)[1:1]. Or consider if we want to assign integer(kind=4)[0:D.1387] and integer(kind=4)[4] the same alias set or not. Just be pragmatic here and make sure the array and its element type get the same alias set assigned. */ else if (TREE_CODE (t) == ARRAY_TYPE && !TYPE_NONALIASED_COMPONENT (t)) set = get_alias_set (TREE_TYPE (t)); /* From the former common C and C++ langhook implementation: Unfortunately, there is no canonical form of a pointer type. In particular, if we have `typedef int I', then `int *', and `I *' are different types. So, we have to pick a canonical representative. We do this below. Technically, this approach is actually more conservative that it needs to be. In particular, `const int *' and `int *' should be in different alias sets, according to the C and C++ standard, since their types are not the same, and so, technically, an `int **' and `const int **' cannot point at the same thing. But, the standard is wrong. In particular, this code is legal C++: int *ip; int **ipp = &ip; const int* const* cipp = ipp; And, it doesn't make sense for that to be legal unless you can dereference IPP and CIPP. So, we ignore cv-qualifiers on the pointed-to types. This issue has been reported to the C++ committee. For this reason go to canonical type of the unqalified pointer type. Until GCC 6 this code set all pointers sets to have alias set of ptr_type_node but that is a bad idea, because it prevents disabiguations in between pointers. For Firefox this accounts about 20% of all disambiguations in the program. */ else if (POINTER_TYPE_P (t) && t != ptr_type_node && !in_lto_p) { tree p; auto_vec reference; /* Unnest all pointers and references. We also want to make pointer to array equivalent to pointer to its element. So skip all array types, too. */ for (p = t; POINTER_TYPE_P (p) || (TREE_CODE (p) == ARRAY_TYPE && !TYPE_NONALIASED_COMPONENT (p)); p = TREE_TYPE (p)) { if (TREE_CODE (p) == REFERENCE_TYPE) reference.safe_push (true); if (TREE_CODE (p) == POINTER_TYPE) reference.safe_push (false); } p = TYPE_MAIN_VARIANT (p); /* Make void * compatible with char * and also void **. Programs are commonly violating TBAA by this. We also make void * to conflict with every pointer (see record_component_aliases) and thus it is safe it to use it for pointers to types with TYPE_STRUCTURAL_EQUALITY_P. */ if (TREE_CODE (p) == VOID_TYPE || TYPE_STRUCTURAL_EQUALITY_P (p)) set = get_alias_set (ptr_type_node); else { /* Rebuild pointer type from starting from canonical types using unqualified pointers and references only. This way all such pointers will have the same alias set and will conflict with each other. Most of time we already have pointers or references of a given type. If not we build new one just to be sure that if someone later (probably only middle-end can, as we should assign all alias classes only after finishing translation unit) builds the pointer type, the canonical type will match. */ p = TYPE_CANONICAL (p); while (!reference.is_empty ()) { if (reference.pop ()) p = build_reference_type (p); else p = build_pointer_type (p); p = TYPE_CANONICAL (TYPE_MAIN_VARIANT (p)); } gcc_checking_assert (TYPE_CANONICAL (p) == p); /* Assign the alias set to both p and t. We can not call get_alias_set (p) here as that would trigger infinite recursion when p == t. In other cases it would just trigger unnecesary legwork of rebuilding the pointer again. */ if (TYPE_ALIAS_SET_KNOWN_P (p)) set = TYPE_ALIAS_SET (p); else { set = new_alias_set (); TYPE_ALIAS_SET (p) = set; } } } /* In LTO the rules above needs to be part of canonical type machinery. For now just punt. */ else if (POINTER_TYPE_P (t) && t != TYPE_CANONICAL (ptr_type_node) && in_lto_p) set = get_alias_set (TYPE_CANONICAL (ptr_type_node)); /* Otherwise make a new alias set for this type. */ else { /* Each canonical type gets its own alias set, so canonical types shouldn't form a tree. It doesn't really matter for types we handle specially above, so only check it where it possibly would result in a bogus alias set. */ gcc_checking_assert (TYPE_CANONICAL (t) == t); set = new_alias_set (); } TYPE_ALIAS_SET (t) = set; /* If this is an aggregate type or a complex type, we must record any component aliasing information. */ if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE) record_component_aliases (t); /* We treat pointer types specially in alias_set_subset_of. */ if (POINTER_TYPE_P (t) && set) { alias_set_entry ase = get_alias_set_entry (set); if (!ase) ase = init_alias_set_entry (set); ase->is_pointer = true; ase->has_pointer = true; } return set; } /* Return a brand-new alias set. */ alias_set_type new_alias_set (void) { if (flag_strict_aliasing) { if (alias_sets == 0) vec_safe_push (alias_sets, (alias_set_entry) 0); vec_safe_push (alias_sets, (alias_set_entry) 0); return alias_sets->length () - 1; } else return 0; } /* Indicate that things in SUBSET can alias things in SUPERSET, but that not everything that aliases SUPERSET also aliases SUBSET. For example, in C, a store to an `int' can alias a load of a structure containing an `int', and vice versa. But it can't alias a load of a 'double' member of the same structure. Here, the structure would be the SUPERSET and `int' the SUBSET. This relationship is also described in the comment at the beginning of this file. This function should be called only once per SUPERSET/SUBSET pair. It is illegal for SUPERSET to be zero; everything is implicitly a subset of alias set zero. */ void record_alias_subset (alias_set_type superset, alias_set_type subset) { alias_set_entry superset_entry; alias_set_entry subset_entry; /* It is possible in complex type situations for both sets to be the same, in which case we can ignore this operation. */ if (superset == subset) return; gcc_assert (superset); superset_entry = get_alias_set_entry (superset); if (superset_entry == 0) { /* Create an entry for the SUPERSET, so that we have a place to attach the SUBSET. */ superset_entry = init_alias_set_entry (superset); } if (subset == 0) superset_entry->has_zero_child = 1; else { subset_entry = get_alias_set_entry (subset); if (!superset_entry->children) superset_entry->children = hash_map::create_ggc (64); /* If there is an entry for the subset, enter all of its children (if they are not already present) as children of the SUPERSET. */ if (subset_entry) { if (subset_entry->has_zero_child) superset_entry->has_zero_child = true; if (subset_entry->has_pointer) superset_entry->has_pointer = true; if (subset_entry->children) { hash_map::iterator iter = subset_entry->children->begin (); for (; iter != subset_entry->children->end (); ++iter) superset_entry->children->put ((*iter).first, (*iter).second); } } /* Enter the SUBSET itself as a child of the SUPERSET. */ superset_entry->children->put (subset, 0); } } /* Record that component types of TYPE, if any, are part of that type for aliasing purposes. For record types, we only record component types for fields that are not marked non-addressable. For array types, we only record the component type if it is not marked non-aliased. */ void record_component_aliases (tree type) { alias_set_type superset = get_alias_set (type); tree field; if (superset == 0) return; switch (TREE_CODE (type)) { case RECORD_TYPE: case UNION_TYPE: case QUAL_UNION_TYPE: for (field = TYPE_FIELDS (type); field != 0; field = DECL_CHAIN (field)) if (TREE_CODE (field) == FIELD_DECL && !DECL_NONADDRESSABLE_P (field)) record_alias_subset (superset, get_alias_set (TREE_TYPE (field))); break; case COMPLEX_TYPE: record_alias_subset (superset, get_alias_set (TREE_TYPE (type))); break; /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their element type. */ default: break; } } /* Allocate an alias set for use in storing and reading from the varargs spill area. */ static GTY(()) alias_set_type varargs_set = -1; alias_set_type get_varargs_alias_set (void) { #if 1 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the varargs alias set to an INDIRECT_REF (FIXME!), so we can't consistently use the varargs alias set for loads from the varargs area. So don't use it anywhere. */ return 0; #else if (varargs_set == -1) varargs_set = new_alias_set (); return varargs_set; #endif } /* Likewise, but used for the fixed portions of the frame, e.g., register save areas. */ static GTY(()) alias_set_type frame_set = -1; alias_set_type get_frame_alias_set (void) { if (frame_set == -1) frame_set = new_alias_set (); return frame_set; } /* Create a new, unique base with id ID. */ static rtx unique_base_value (HOST_WIDE_INT id) { return gen_rtx_ADDRESS (Pmode, id); } /* Return true if accesses based on any other base value cannot alias those based on X. */ static bool unique_base_value_p (rtx x) { return GET_CODE (x) == ADDRESS && GET_MODE (x) == Pmode; } /* Return true if X is known to be a base value. */ static bool known_base_value_p (rtx x) { switch (GET_CODE (x)) { case LABEL_REF: case SYMBOL_REF: return true; case ADDRESS: /* Arguments may or may not be bases; we don't know for sure. */ return GET_MODE (x) != VOIDmode; default: return false; } } /* Inside SRC, the source of a SET, find a base address. */ static rtx find_base_value (rtx src) { unsigned int regno; #if defined (FIND_BASE_TERM) /* Try machine-dependent ways to find the base term. */ src = FIND_BASE_TERM (src); #endif switch (GET_CODE (src)) { case SYMBOL_REF: case LABEL_REF: return src; case REG: regno = REGNO (src); /* At the start of a function, argument registers have known base values which may be lost later. Returning an ADDRESS expression here allows optimization based on argument values even when the argument registers are used for other purposes. */ if (regno < FIRST_PSEUDO_REGISTER && copying_arguments) return new_reg_base_value[regno]; /* If a pseudo has a known base value, return it. Do not do this for non-fixed hard regs since it can result in a circular dependency chain for registers which have values at function entry. The test above is not sufficient because the scheduler may move a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */ if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno]) && regno < vec_safe_length (reg_base_value)) { /* If we're inside init_alias_analysis, use new_reg_base_value to reduce the number of relaxation iterations. */ if (new_reg_base_value && new_reg_base_value[regno] && DF_REG_DEF_COUNT (regno) == 1) return new_reg_base_value[regno]; if ((*reg_base_value)[regno]) return (*reg_base_value)[regno]; } return 0; case MEM: /* Check for an argument passed in memory. Only record in the copying-arguments block; it is too hard to track changes otherwise. */ if (copying_arguments && (XEXP (src, 0) == arg_pointer_rtx || (GET_CODE (XEXP (src, 0)) == PLUS && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx))) return arg_base_value; return 0; case CONST: src = XEXP (src, 0); if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS) break; /* ... fall through ... */ case PLUS: case MINUS: { rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1); /* If either operand is a REG that is a known pointer, then it is the base. */ if (REG_P (src_0) && REG_POINTER (src_0)) return find_base_value (src_0); if (REG_P (src_1) && REG_POINTER (src_1)) return find_base_value (src_1); /* If either operand is a REG, then see if we already have a known value for it. */ if (REG_P (src_0)) { temp = find_base_value (src_0); if (temp != 0) src_0 = temp; } if (REG_P (src_1)) { temp = find_base_value (src_1); if (temp!= 0) src_1 = temp; } /* If either base is named object or a special address (like an argument or stack reference), then use it for the base term. */ if (src_0 != 0 && known_base_value_p (src_0)) return src_0; if (src_1 != 0 && known_base_value_p (src_1)) return src_1; /* Guess which operand is the base address: If either operand is a symbol, then it is the base. If either operand is a CONST_INT, then the other is the base. */ if (CONST_INT_P (src_1) || CONSTANT_P (src_0)) return find_base_value (src_0); else if (CONST_INT_P (src_0) || CONSTANT_P (src_1)) return find_base_value (src_1); return 0; } case LO_SUM: /* The standard form is (lo_sum reg sym) so look only at the second operand. */ return find_base_value (XEXP (src, 1)); case AND: /* If the second operand is constant set the base address to the first operand. */ if (CONST_INT_P (XEXP (src, 1)) && INTVAL (XEXP (src, 1)) != 0) return find_base_value (XEXP (src, 0)); return 0; case TRUNCATE: /* As we do not know which address space the pointer is referring to, we can handle this only if the target does not support different pointer or address modes depending on the address space. */ if (!target_default_pointer_address_modes_p ()) break; if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode)) break; /* Fall through. */ case HIGH: case PRE_INC: case PRE_DEC: case POST_INC: case POST_DEC: case PRE_MODIFY: case POST_MODIFY: return find_base_value (XEXP (src, 0)); case ZERO_EXTEND: case SIGN_EXTEND: /* used for NT/Alpha pointers */ /* As we do not know which address space the pointer is referring to, we can handle this only if the target does not support different pointer or address modes depending on the address space. */ if (!target_default_pointer_address_modes_p ()) break; { rtx temp = find_base_value (XEXP (src, 0)); if (temp != 0 && CONSTANT_P (temp)) temp = convert_memory_address (Pmode, temp); return temp; } default: break; } return 0; } /* Called from init_alias_analysis indirectly through note_stores, or directly if DEST is a register with a REG_NOALIAS note attached. SET is null in the latter case. */ /* While scanning insns to find base values, reg_seen[N] is nonzero if register N has been set in this function. */ static sbitmap reg_seen; static void record_set (rtx dest, const_rtx set, void *data ATTRIBUTE_UNUSED) { unsigned regno; rtx src; int n; if (!REG_P (dest)) return; regno = REGNO (dest); gcc_checking_assert (regno < reg_base_value->length ()); n = REG_NREGS (dest); if (n != 1) { while (--n >= 0) { bitmap_set_bit (reg_seen, regno + n); new_reg_base_value[regno + n] = 0; } return; } if (set) { /* A CLOBBER wipes out any old value but does not prevent a previously unset register from acquiring a base address (i.e. reg_seen is not set). */ if (GET_CODE (set) == CLOBBER) { new_reg_base_value[regno] = 0; return; } src = SET_SRC (set); } else { /* There's a REG_NOALIAS note against DEST. */ if (bitmap_bit_p (reg_seen, regno)) { new_reg_base_value[regno] = 0; return; } bitmap_set_bit (reg_seen, regno); new_reg_base_value[regno] = unique_base_value (unique_id++); return; } /* If this is not the first set of REGNO, see whether the new value is related to the old one. There are two cases of interest: (1) The register might be assigned an entirely new value that has the same base term as the original set. (2) The set might be a simple self-modification that cannot change REGNO's base value. If neither case holds, reject the original base value as invalid. Note that the following situation is not detected: extern int x, y; int *p = &x; p += (&y-&x); ANSI C does not allow computing the difference of addresses of distinct top level objects. */ if (new_reg_base_value[regno] != 0 && find_base_value (src) != new_reg_base_value[regno]) switch (GET_CODE (src)) { case LO_SUM: case MINUS: if (XEXP (src, 0) != dest && XEXP (src, 1) != dest) new_reg_base_value[regno] = 0; break; case PLUS: /* If the value we add in the PLUS is also a valid base value, this might be the actual base value, and the original value an index. */ { rtx other = NULL_RTX; if (XEXP (src, 0) == dest) other = XEXP (src, 1); else if (XEXP (src, 1) == dest) other = XEXP (src, 0); if (! other || find_base_value (other)) new_reg_base_value[regno] = 0; break; } case AND: if (XEXP (src, 0) != dest || !CONST_INT_P (XEXP (src, 1))) new_reg_base_value[regno] = 0; break; default: new_reg_base_value[regno] = 0; break; } /* If this is the first set of a register, record the value. */ else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno]) && ! bitmap_bit_p (reg_seen, regno) && new_reg_base_value[regno] == 0) new_reg_base_value[regno] = find_base_value (src); bitmap_set_bit (reg_seen, regno); } /* Return REG_BASE_VALUE for REGNO. Selective scheduler uses this to avoid using hard registers with non-null REG_BASE_VALUE for renaming. */ rtx get_reg_base_value (unsigned int regno) { return (*reg_base_value)[regno]; } /* If a value is known for REGNO, return it. */ rtx get_reg_known_value (unsigned int regno) { if (regno >= FIRST_PSEUDO_REGISTER) { regno -= FIRST_PSEUDO_REGISTER; if (regno < vec_safe_length (reg_known_value)) return (*reg_known_value)[regno]; } return NULL; } /* Set it. */ static void set_reg_known_value (unsigned int regno, rtx val) { if (regno >= FIRST_PSEUDO_REGISTER) { regno -= FIRST_PSEUDO_REGISTER; if (regno < vec_safe_length (reg_known_value)) (*reg_known_value)[regno] = val; } } /* Similarly for reg_known_equiv_p. */ bool get_reg_known_equiv_p (unsigned int regno) { if (regno >= FIRST_PSEUDO_REGISTER) { regno -= FIRST_PSEUDO_REGISTER; if (regno < vec_safe_length (reg_known_value)) return bitmap_bit_p (reg_known_equiv_p, regno); } return false; } static void set_reg_known_equiv_p (unsigned int regno, bool val) { if (regno >= FIRST_PSEUDO_REGISTER) { regno -= FIRST_PSEUDO_REGISTER; if (regno < vec_safe_length (reg_known_value)) { if (val) bitmap_set_bit (reg_known_equiv_p, regno); else bitmap_clear_bit (reg_known_equiv_p, regno); } } } /* Returns a canonical version of X, from the point of view alias analysis. (For example, if X is a MEM whose address is a register, and the register has a known value (say a SYMBOL_REF), then a MEM whose address is the SYMBOL_REF is returned.) */ rtx canon_rtx (rtx x) { /* Recursively look for equivalences. */ if (REG_P (x) && REGNO (x) >= FIRST_PSEUDO_REGISTER) { rtx t = get_reg_known_value (REGNO (x)); if (t == x) return x; if (t) return canon_rtx (t); } if (GET_CODE (x) == PLUS) { rtx x0 = canon_rtx (XEXP (x, 0)); rtx x1 = canon_rtx (XEXP (x, 1)); if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1)) { if (CONST_INT_P (x0)) return plus_constant (GET_MODE (x), x1, INTVAL (x0)); else if (CONST_INT_P (x1)) return plus_constant (GET_MODE (x), x0, INTVAL (x1)); return gen_rtx_PLUS (GET_MODE (x), x0, x1); } } /* This gives us much better alias analysis when called from the loop optimizer. Note we want to leave the original MEM alone, but need to return the canonicalized MEM with all the flags with their original values. */ else if (MEM_P (x)) x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0))); return x; } /* Return 1 if X and Y are identical-looking rtx's. Expect that X and Y has been already canonicalized. We use the data in reg_known_value above to see if two registers with different numbers are, in fact, equivalent. */ static int rtx_equal_for_memref_p (const_rtx x, const_rtx y) { int i; int j; enum rtx_code code; const char *fmt; if (x == 0 && y == 0) return 1; if (x == 0 || y == 0) return 0; if (x == y) return 1; code = GET_CODE (x); /* Rtx's of different codes cannot be equal. */ if (code != GET_CODE (y)) return 0; /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. (REG:SI x) and (REG:HI x) are NOT equivalent. */ if (GET_MODE (x) != GET_MODE (y)) return 0; /* Some RTL can be compared without a recursive examination. */ switch (code) { case REG: return REGNO (x) == REGNO (y); case LABEL_REF: return LABEL_REF_LABEL (x) == LABEL_REF_LABEL (y); case SYMBOL_REF: return XSTR (x, 0) == XSTR (y, 0); case ENTRY_VALUE: /* This is magic, don't go through canonicalization et al. */ return rtx_equal_p (ENTRY_VALUE_EXP (x), ENTRY_VALUE_EXP (y)); case VALUE: CASE_CONST_UNIQUE: /* Pointer equality guarantees equality for these nodes. */ return 0; default: break; } /* canon_rtx knows how to handle plus. No need to canonicalize. */ if (code == PLUS) return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)) && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1))) || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1)) && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0)))); /* For commutative operations, the RTX match if the operand match in any order. Also handle the simple binary and unary cases without a loop. */ if (COMMUTATIVE_P (x)) { rtx xop0 = canon_rtx (XEXP (x, 0)); rtx yop0 = canon_rtx (XEXP (y, 0)); rtx yop1 = canon_rtx (XEXP (y, 1)); return ((rtx_equal_for_memref_p (xop0, yop0) && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop1)) || (rtx_equal_for_memref_p (xop0, yop1) && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop0))); } else if (NON_COMMUTATIVE_P (x)) { return (rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)), canon_rtx (XEXP (y, 0))) && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), canon_rtx (XEXP (y, 1)))); } else if (UNARY_P (x)) return rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)), canon_rtx (XEXP (y, 0))); /* Compare the elements. If any pair of corresponding elements fail to match, return 0 for the whole things. Limit cases to types which actually appear in addresses. */ fmt = GET_RTX_FORMAT (code); for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) { switch (fmt[i]) { case 'i': if (XINT (x, i) != XINT (y, i)) return 0; break; case 'E': /* Two vectors must have the same length. */ if (XVECLEN (x, i) != XVECLEN (y, i)) return 0; /* And the corresponding elements must match. */ for (j = 0; j < XVECLEN (x, i); j++) if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x, i, j)), canon_rtx (XVECEXP (y, i, j))) == 0) return 0; break; case 'e': if (rtx_equal_for_memref_p (canon_rtx (XEXP (x, i)), canon_rtx (XEXP (y, i))) == 0) return 0; break; /* This can happen for asm operands. */ case 's': if (strcmp (XSTR (x, i), XSTR (y, i))) return 0; break; /* This can happen for an asm which clobbers memory. */ case '0': break; /* It is believed that rtx's at this level will never contain anything but integers and other rtx's, except for within LABEL_REFs and SYMBOL_REFs. */ default: gcc_unreachable (); } } return 1; } static rtx find_base_term (rtx x) { cselib_val *val; struct elt_loc_list *l, *f; rtx ret; #if defined (FIND_BASE_TERM) /* Try machine-dependent ways to find the base term. */ x = FIND_BASE_TERM (x); #endif switch (GET_CODE (x)) { case REG: return REG_BASE_VALUE (x); case TRUNCATE: /* As we do not know which address space the pointer is referring to, we can handle this only if the target does not support different pointer or address modes depending on the address space. */ if (!target_default_pointer_address_modes_p ()) return 0; if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode)) return 0; /* Fall through. */ case HIGH: case PRE_INC: case PRE_DEC: case POST_INC: case POST_DEC: case PRE_MODIFY: case POST_MODIFY: return find_base_term (XEXP (x, 0)); case ZERO_EXTEND: case SIGN_EXTEND: /* Used for Alpha/NT pointers */ /* As we do not know which address space the pointer is referring to, we can handle this only if the target does not support different pointer or address modes depending on the address space. */ if (!target_default_pointer_address_modes_p ()) return 0; { rtx temp = find_base_term (XEXP (x, 0)); if (temp != 0 && CONSTANT_P (temp)) temp = convert_memory_address (Pmode, temp); return temp; } case VALUE: val = CSELIB_VAL_PTR (x); ret = NULL_RTX; if (!val) return ret; if (cselib_sp_based_value_p (val)) return static_reg_base_value[STACK_POINTER_REGNUM]; f = val->locs; /* Temporarily reset val->locs to avoid infinite recursion. */ val->locs = NULL; for (l = f; l; l = l->next) if (GET_CODE (l->loc) == VALUE && CSELIB_VAL_PTR (l->loc)->locs && !CSELIB_VAL_PTR (l->loc)->locs->next && CSELIB_VAL_PTR (l->loc)->locs->loc == x) continue; else if ((ret = find_base_term (l->loc)) != 0) break; val->locs = f; return ret; case LO_SUM: /* The standard form is (lo_sum reg sym) so look only at the second operand. */ return find_base_term (XEXP (x, 1)); case CONST: x = XEXP (x, 0); if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS) return 0; /* Fall through. */ case PLUS: case MINUS: { rtx tmp1 = XEXP (x, 0); rtx tmp2 = XEXP (x, 1); /* This is a little bit tricky since we have to determine which of the two operands represents the real base address. Otherwise this routine may return the index register instead of the base register. That may cause us to believe no aliasing was possible, when in fact aliasing is possible. We use a few simple tests to guess the base register. Additional tests can certainly be added. For example, if one of the operands is a shift or multiply, then it must be the index register and the other operand is the base register. */ if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2)) return find_base_term (tmp2); /* If either operand is known to be a pointer, then prefer it to determine the base term. */ if (REG_P (tmp1) && REG_POINTER (tmp1)) ; else if (REG_P (tmp2) && REG_POINTER (tmp2)) std::swap (tmp1, tmp2); /* If second argument is constant which has base term, prefer it over variable tmp1. See PR64025. */ else if (CONSTANT_P (tmp2) && !CONST_INT_P (tmp2)) std::swap (tmp1, tmp2); /* Go ahead and find the base term for both operands. If either base term is from a pointer or is a named object or a special address (like an argument or stack reference), then use it for the base term. */ rtx base = find_base_term (tmp1); if (base != NULL_RTX && ((REG_P (tmp1) && REG_POINTER (tmp1)) || known_base_value_p (base))) return base; base = find_base_term (tmp2); if (base != NULL_RTX && ((REG_P (tmp2) && REG_POINTER (tmp2)) || known_base_value_p (base))) return base; /* We could not determine which of the two operands was the base register and which was the index. So we can determine nothing from the base alias check. */ return 0; } case AND: if (CONST_INT_P (XEXP (x, 1)) && INTVAL (XEXP (x, 1)) != 0) return find_base_term (XEXP (x, 0)); return 0; case SYMBOL_REF: case LABEL_REF: return x; default: return 0; } } /* Return true if accesses to address X may alias accesses based on the stack pointer. */ bool may_be_sp_based_p (rtx x) { rtx base = find_base_term (x); return !base || base == static_reg_base_value[STACK_POINTER_REGNUM]; } /* Return 0 if the addresses X and Y are known to point to different objects, 1 if they might be pointers to the same object. */ static int base_alias_check (rtx x, rtx x_base, rtx y, rtx y_base, machine_mode x_mode, machine_mode y_mode) { /* If the address itself has no known base see if a known equivalent value has one. If either address still has no known base, nothing is known about aliasing. */ if (x_base == 0) { rtx x_c; if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x) return 1; x_base = find_base_term (x_c); if (x_base == 0) return 1; } if (y_base == 0) { rtx y_c; if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y) return 1; y_base = find_base_term (y_c); if (y_base == 0) return 1; } /* If the base addresses are equal nothing is known about aliasing. */ if (rtx_equal_p (x_base, y_base)) return 1; /* The base addresses are different expressions. If they are not accessed via AND, there is no conflict. We can bring knowledge of object alignment into play here. For example, on alpha, "char a, b;" can alias one another, though "char a; long b;" cannot. AND addesses may implicitly alias surrounding objects; i.e. unaligned access in DImode via AND address can alias all surrounding object types except those with aligment 8 or higher. */ if (GET_CODE (x) == AND && GET_CODE (y) == AND) return 1; if (GET_CODE (x) == AND && (!CONST_INT_P (XEXP (x, 1)) || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1)))) return 1; if (GET_CODE (y) == AND && (!CONST_INT_P (XEXP (y, 1)) || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1)))) return 1; /* Differing symbols not accessed via AND never alias. */ if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS) return 0; if (unique_base_value_p (x_base) || unique_base_value_p (y_base)) return 0; return 1; } /* Return TRUE if EXPR refers to a VALUE whose uid is greater than that of V. */ static bool refs_newer_value_p (const_rtx expr, rtx v) { int minuid = CSELIB_VAL_PTR (v)->uid; subrtx_iterator::array_type array; FOR_EACH_SUBRTX (iter, array, expr, NONCONST) if (GET_CODE (*iter) == VALUE && CSELIB_VAL_PTR (*iter)->uid > minuid) return true; return false; } /* Convert the address X into something we can use. This is done by returning it unchanged unless it is a value; in the latter case we call cselib to get a more useful rtx. */ rtx get_addr (rtx x) { cselib_val *v; struct elt_loc_list *l; if (GET_CODE (x) != VALUE) return x; v = CSELIB_VAL_PTR (x); if (v) { bool have_equivs = cselib_have_permanent_equivalences (); if (have_equivs) v = canonical_cselib_val (v); for (l = v->locs; l; l = l->next) if (CONSTANT_P (l->loc)) return l->loc; for (l = v->locs; l; l = l->next) if (!REG_P (l->loc) && !MEM_P (l->loc) /* Avoid infinite recursion when potentially dealing with var-tracking artificial equivalences, by skipping the equivalences themselves, and not choosing expressions that refer to newer VALUEs. */ && (!have_equivs || (GET_CODE (l->loc) != VALUE && !refs_newer_value_p (l->loc, x)))) return l->loc; if (have_equivs) { for (l = v->locs; l; l = l->next) if (REG_P (l->loc) || (GET_CODE (l->loc) != VALUE && !refs_newer_value_p (l->loc, x))) return l->loc; /* Return the canonical value. */ return v->val_rtx; } if (v->locs) return v->locs->loc; } return x; } /* Return the address of the (N_REFS + 1)th memory reference to ADDR where SIZE is the size in bytes of the memory reference. If ADDR is not modified by the memory reference then ADDR is returned. */ static rtx addr_side_effect_eval (rtx addr, int size, int n_refs) { int offset = 0; switch (GET_CODE (addr)) { case PRE_INC: offset = (n_refs + 1) * size; break; case PRE_DEC: offset = -(n_refs + 1) * size; break; case POST_INC: offset = n_refs * size; break; case POST_DEC: offset = -n_refs * size; break; default: return addr; } if (offset) addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), gen_int_mode (offset, GET_MODE (addr))); else addr = XEXP (addr, 0); addr = canon_rtx (addr); return addr; } /* Return TRUE if an object X sized at XSIZE bytes and another object Y sized at YSIZE bytes, starting C bytes after X, may overlap. If any of the sizes is zero, assume an overlap, otherwise use the absolute value of the sizes as the actual sizes. */ static inline bool offset_overlap_p (HOST_WIDE_INT c, int xsize, int ysize) { return (xsize == 0 || ysize == 0 || (c >= 0 ? (abs (xsize) > c) : (abs (ysize) > -c))); } /* Return one if X and Y (memory addresses) reference the same location in memory or if the references overlap. Return zero if they do not overlap, else return minus one in which case they still might reference the same location. C is an offset accumulator. When C is nonzero, we are testing aliases between X and Y + C. XSIZE is the size in bytes of the X reference, similarly YSIZE is the size in bytes for Y. Expect that canon_rtx has been already called for X and Y. If XSIZE or YSIZE is zero, we do not know the amount of memory being referenced (the reference was BLKmode), so make the most pessimistic assumptions. If XSIZE or YSIZE is negative, we may access memory outside the object being referenced as a side effect. This can happen when using AND to align memory references, as is done on the Alpha. Nice to notice that varying addresses cannot conflict with fp if no local variables had their addresses taken, but that's too hard now. ??? Contrary to the tree alias oracle this does not return one for X + non-constant and Y + non-constant when X and Y are equal. If that is fixed the TBAA hack for union type-punning can be removed. */ static int memrefs_conflict_p (int xsize, rtx x, int ysize, rtx y, HOST_WIDE_INT c) { if (GET_CODE (x) == VALUE) { if (REG_P (y)) { struct elt_loc_list *l = NULL; if (CSELIB_VAL_PTR (x)) for (l = canonical_cselib_val (CSELIB_VAL_PTR (x))->locs; l; l = l->next) if (REG_P (l->loc) && rtx_equal_for_memref_p (l->loc, y)) break; if (l) x = y; else x = get_addr (x); } /* Don't call get_addr if y is the same VALUE. */ else if (x != y) x = get_addr (x); } if (GET_CODE (y) == VALUE) { if (REG_P (x)) { struct elt_loc_list *l = NULL; if (CSELIB_VAL_PTR (y)) for (l = canonical_cselib_val (CSELIB_VAL_PTR (y))->locs; l; l = l->next) if (REG_P (l->loc) && rtx_equal_for_memref_p (l->loc, x)) break; if (l) y = x; else y = get_addr (y); } /* Don't call get_addr if x is the same VALUE. */ else if (y != x) y = get_addr (y); } if (GET_CODE (x) == HIGH) x = XEXP (x, 0); else if (GET_CODE (x) == LO_SUM) x = XEXP (x, 1); else x = addr_side_effect_eval (x, abs (xsize), 0); if (GET_CODE (y) == HIGH) y = XEXP (y, 0); else if (GET_CODE (y) == LO_SUM) y = XEXP (y, 1); else y = addr_side_effect_eval (y, abs (ysize), 0); if (rtx_equal_for_memref_p (x, y)) { return offset_overlap_p (c, xsize, ysize); } /* This code used to check for conflicts involving stack references and globals but the base address alias code now handles these cases. */ if (GET_CODE (x) == PLUS) { /* The fact that X is canonicalized means that this PLUS rtx is canonicalized. */ rtx x0 = XEXP (x, 0); rtx x1 = XEXP (x, 1); if (GET_CODE (y) == PLUS) { /* The fact that Y is canonicalized means that this PLUS rtx is canonicalized. */ rtx y0 = XEXP (y, 0); rtx y1 = XEXP (y, 1); if (rtx_equal_for_memref_p (x1, y1)) return memrefs_conflict_p (xsize, x0, ysize, y0, c); if (rtx_equal_for_memref_p (x0, y0)) return memrefs_conflict_p (xsize, x1, ysize, y1, c); if (CONST_INT_P (x1)) { if (CONST_INT_P (y1)) return memrefs_conflict_p (xsize, x0, ysize, y0, c - INTVAL (x1) + INTVAL (y1)); else return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1)); } else if (CONST_INT_P (y1)) return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1)); return -1; } else if (CONST_INT_P (x1)) return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1)); } else if (GET_CODE (y) == PLUS) { /* The fact that Y is canonicalized means that this PLUS rtx is canonicalized. */ rtx y0 = XEXP (y, 0); rtx y1 = XEXP (y, 1); if (CONST_INT_P (y1)) return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1)); else return -1; } if (GET_CODE (x) == GET_CODE (y)) switch (GET_CODE (x)) { case MULT: { /* Handle cases where we expect the second operands to be the same, and check only whether the first operand would conflict or not. */ rtx x0, y0; rtx x1 = canon_rtx (XEXP (x, 1)); rtx y1 = canon_rtx (XEXP (y, 1)); if (! rtx_equal_for_memref_p (x1, y1)) return -1; x0 = canon_rtx (XEXP (x, 0)); y0 = canon_rtx (XEXP (y, 0)); if (rtx_equal_for_memref_p (x0, y0)) return offset_overlap_p (c, xsize, ysize); /* Can't properly adjust our sizes. */ if (!CONST_INT_P (x1)) return -1; xsize /= INTVAL (x1); ysize /= INTVAL (x1); c /= INTVAL (x1); return memrefs_conflict_p (xsize, x0, ysize, y0, c); } default: break; } /* Deal with alignment ANDs by adjusting offset and size so as to cover the maximum range, without taking any previously known alignment into account. Make a size negative after such an adjustments, so that, if we end up with e.g. two SYMBOL_REFs, we assume a potential overlap, because they may end up in contiguous memory locations and the stricter-alignment access may span over part of both. */ if (GET_CODE (x) == AND && CONST_INT_P (XEXP (x, 1))) { HOST_WIDE_INT sc = INTVAL (XEXP (x, 1)); unsigned HOST_WIDE_INT uc = sc; if (sc < 0 && -uc == (uc & -uc)) { if (xsize > 0) xsize = -xsize; if (xsize) xsize += sc + 1; c -= sc + 1; return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c); } } if (GET_CODE (y) == AND && CONST_INT_P (XEXP (y, 1))) { HOST_WIDE_INT sc = INTVAL (XEXP (y, 1)); unsigned HOST_WIDE_INT uc = sc; if (sc < 0 && -uc == (uc & -uc)) { if (ysize > 0) ysize = -ysize; if (ysize) ysize += sc + 1; c += sc + 1; return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c); } } if (CONSTANT_P (x)) { if (CONST_INT_P (x) && CONST_INT_P (y)) { c += (INTVAL (y) - INTVAL (x)); return offset_overlap_p (c, xsize, ysize); } if (GET_CODE (x) == CONST) { if (GET_CODE (y) == CONST) return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, canon_rtx (XEXP (y, 0)), c); else return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c); } if (GET_CODE (y) == CONST) return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c); /* Assume a potential overlap for symbolic addresses that went through alignment adjustments (i.e., that have negative sizes), because we can't know how far they are from each other. */ if (CONSTANT_P (y)) return (xsize < 0 || ysize < 0 || offset_overlap_p (c, xsize, ysize)); return -1; } return -1; } /* Functions to compute memory dependencies. Since we process the insns in execution order, we can build tables to keep track of what registers are fixed (and not aliased), what registers are varying in known ways, and what registers are varying in unknown ways. If both memory references are volatile, then there must always be a dependence between the two references, since their order can not be changed. A volatile and non-volatile reference can be interchanged though. We also must allow AND addresses, because they may generate accesses outside the object being referenced. This is used to generate aligned addresses from unaligned addresses, for instance, the alpha storeqi_unaligned pattern. */ /* Read dependence: X is read after read in MEM takes place. There can only be a dependence here if both reads are volatile, or if either is an explicit barrier. */ int read_dependence (const_rtx mem, const_rtx x) { if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) return true; if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER) return true; return false; } /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */ static tree decl_for_component_ref (tree x) { do { x = TREE_OPERAND (x, 0); } while (x && TREE_CODE (x) == COMPONENT_REF); return x && DECL_P (x) ? x : NULL_TREE; } /* Walk up the COMPONENT_REF list in X and adjust *OFFSET to compensate for the offset of the field reference. *KNOWN_P says whether the offset is known. */ static void adjust_offset_for_component_ref (tree x, bool *known_p, HOST_WIDE_INT *offset) { if (!*known_p) return; do { tree xoffset = component_ref_field_offset (x); tree field = TREE_OPERAND (x, 1); if (TREE_CODE (xoffset) != INTEGER_CST) { *known_p = false; return; } offset_int woffset = (wi::to_offset (xoffset) + wi::lrshift (wi::to_offset (DECL_FIELD_BIT_OFFSET (field)), LOG2_BITS_PER_UNIT)); if (!wi::fits_uhwi_p (woffset)) { *known_p = false; return; } *offset += woffset.to_uhwi (); x = TREE_OPERAND (x, 0); } while (x && TREE_CODE (x) == COMPONENT_REF); } /* Return nonzero if we can determine the exprs corresponding to memrefs X and Y and they do not overlap. If LOOP_VARIANT is set, skip offset-based disambiguation */ int nonoverlapping_memrefs_p (const_rtx x, const_rtx y, bool loop_invariant) { tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y); rtx rtlx, rtly; rtx basex, basey; bool moffsetx_known_p, moffsety_known_p; HOST_WIDE_INT moffsetx = 0, moffsety = 0; HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem; /* Unless both have exprs, we can't tell anything. */ if (exprx == 0 || expry == 0) return 0; /* For spill-slot accesses make sure we have valid offsets. */ if ((exprx == get_spill_slot_decl (false) && ! MEM_OFFSET_KNOWN_P (x)) || (expry == get_spill_slot_decl (false) && ! MEM_OFFSET_KNOWN_P (y))) return 0; /* If the field reference test failed, look at the DECLs involved. */ moffsetx_known_p = MEM_OFFSET_KNOWN_P (x); if (moffsetx_known_p) moffsetx = MEM_OFFSET (x); if (TREE_CODE (exprx) == COMPONENT_REF) { tree t = decl_for_component_ref (exprx); if (! t) return 0; adjust_offset_for_component_ref (exprx, &moffsetx_known_p, &moffsetx); exprx = t; } moffsety_known_p = MEM_OFFSET_KNOWN_P (y); if (moffsety_known_p) moffsety = MEM_OFFSET (y); if (TREE_CODE (expry) == COMPONENT_REF) { tree t = decl_for_component_ref (expry); if (! t) return 0; adjust_offset_for_component_ref (expry, &moffsety_known_p, &moffsety); expry = t; } if (! DECL_P (exprx) || ! DECL_P (expry)) return 0; /* With invalid code we can end up storing into the constant pool. Bail out to avoid ICEing when creating RTL for this. See gfortran.dg/lto/20091028-2_0.f90. */ if (TREE_CODE (exprx) == CONST_DECL || TREE_CODE (expry) == CONST_DECL) return 1; rtlx = DECL_RTL (exprx); rtly = DECL_RTL (expry); /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they can't overlap unless they are the same because we never reuse that part of the stack frame used for locals for spilled pseudos. */ if ((!MEM_P (rtlx) || !MEM_P (rtly)) && ! rtx_equal_p (rtlx, rtly)) return 1; /* If we have MEMs referring to different address spaces (which can potentially overlap), we cannot easily tell from the addresses whether the references overlap. */ if (MEM_P (rtlx) && MEM_P (rtly) && MEM_ADDR_SPACE (rtlx) != MEM_ADDR_SPACE (rtly)) return 0; /* Get the base and offsets of both decls. If either is a register, we know both are and are the same, so use that as the base. The only we can avoid overlap is if we can deduce that they are nonoverlapping pieces of that decl, which is very rare. */ basex = MEM_P (rtlx) ? XEXP (rtlx, 0) : rtlx; if (GET_CODE (basex) == PLUS && CONST_INT_P (XEXP (basex, 1))) offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0); basey = MEM_P (rtly) ? XEXP (rtly, 0) : rtly; if (GET_CODE (basey) == PLUS && CONST_INT_P (XEXP (basey, 1))) offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0); /* If the bases are different, we know they do not overlap if both are constants or if one is a constant and the other a pointer into the stack frame. Otherwise a different base means we can't tell if they overlap or not. */ if (! rtx_equal_p (basex, basey)) return ((CONSTANT_P (basex) && CONSTANT_P (basey)) || (CONSTANT_P (basex) && REG_P (basey) && REGNO_PTR_FRAME_P (REGNO (basey))) || (CONSTANT_P (basey) && REG_P (basex) && REGNO_PTR_FRAME_P (REGNO (basex)))); /* Offset based disambiguation not appropriate for loop invariant */ if (loop_invariant) return 0; sizex = (!MEM_P (rtlx) ? (int) GET_MODE_SIZE (GET_MODE (rtlx)) : MEM_SIZE_KNOWN_P (rtlx) ? MEM_SIZE (rtlx) : -1); sizey = (!MEM_P (rtly) ? (int) GET_MODE_SIZE (GET_MODE (rtly)) : MEM_SIZE_KNOWN_P (rtly) ? MEM_SIZE (rtly) : -1); /* If we have an offset for either memref, it can update the values computed above. */ if (moffsetx_known_p) offsetx += moffsetx, sizex -= moffsetx; if (moffsety_known_p) offsety += moffsety, sizey -= moffsety; /* If a memref has both a size and an offset, we can use the smaller size. We can't do this if the offset isn't known because we must view this memref as being anywhere inside the DECL's MEM. */ if (MEM_SIZE_KNOWN_P (x) && moffsetx_known_p) sizex = MEM_SIZE (x); if (MEM_SIZE_KNOWN_P (y) && moffsety_known_p) sizey = MEM_SIZE (y); /* Put the values of the memref with the lower offset in X's values. */ if (offsetx > offsety) { tem = offsetx, offsetx = offsety, offsety = tem; tem = sizex, sizex = sizey, sizey = tem; } /* If we don't know the size of the lower-offset value, we can't tell if they conflict. Otherwise, we do the test. */ return sizex >= 0 && offsety >= offsetx + sizex; } /* Helper for true_dependence and canon_true_dependence. Checks for true dependence: X is read after store in MEM takes place. If MEM_CANONICALIZED is FALSE, then X_ADDR and MEM_ADDR should be NULL_RTX, and the canonical addresses of MEM and X are both computed here. If MEM_CANONICALIZED, then MEM must be already canonicalized. If X_ADDR is non-NULL, it is used in preference of XEXP (x, 0). Returns 1 if there is a true dependence, 0 otherwise. */ static int true_dependence_1 (const_rtx mem, machine_mode mem_mode, rtx mem_addr, const_rtx x, rtx x_addr, bool mem_canonicalized) { rtx true_mem_addr; rtx base; int ret; gcc_checking_assert (mem_canonicalized ? (mem_addr != NULL_RTX) : (mem_addr == NULL_RTX && x_addr == NULL_RTX)); if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) return 1; /* (mem:BLK (scratch)) is a special mechanism to conflict with everything. This is used in epilogue deallocation functions, and in cselib. */ if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH) return 1; if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH) return 1; if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER) return 1; if (! x_addr) x_addr = XEXP (x, 0); x_addr = get_addr (x_addr); if (! mem_addr) { mem_addr = XEXP (mem, 0); if (mem_mode == VOIDmode) mem_mode = GET_MODE (mem); } true_mem_addr = get_addr (mem_addr); /* Read-only memory is by definition never modified, and therefore can't conflict with anything. However, don't assume anything when AND addresses are involved and leave to the code below to determine dependence. We don't expect to find read-only set on MEM, but stupid user tricks can produce them, so don't die. */ if (MEM_READONLY_P (x) && GET_CODE (x_addr) != AND && GET_CODE (true_mem_addr) != AND) return 0; /* If we have MEMs referring to different address spaces (which can potentially overlap), we cannot easily tell from the addresses whether the references overlap. */ if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x)) return 1; base = find_base_term (x_addr); if (base && (GET_CODE (base) == LABEL_REF || (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base)))) return 0; rtx mem_base = find_base_term (true_mem_addr); if (! base_alias_check (x_addr, base, true_mem_addr, mem_base, GET_MODE (x), mem_mode)) return 0; x_addr = canon_rtx (x_addr); if (!mem_canonicalized) mem_addr = canon_rtx (true_mem_addr); if ((ret = memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr, SIZE_FOR_MODE (x), x_addr, 0)) != -1) return ret; if (mems_in_disjoint_alias_sets_p (x, mem)) return 0; if (nonoverlapping_memrefs_p (mem, x, false)) return 0; return rtx_refs_may_alias_p (x, mem, true); } /* True dependence: X is read after store in MEM takes place. */ int true_dependence (const_rtx mem, machine_mode mem_mode, const_rtx x) { return true_dependence_1 (mem, mem_mode, NULL_RTX, x, NULL_RTX, /*mem_canonicalized=*/false); } /* Canonical true dependence: X is read after store in MEM takes place. Variant of true_dependence which assumes MEM has already been canonicalized (hence we no longer do that here). The mem_addr argument has been added, since true_dependence_1 computed this value prior to canonicalizing. */ int canon_true_dependence (const_rtx mem, machine_mode mem_mode, rtx mem_addr, const_rtx x, rtx x_addr) { return true_dependence_1 (mem, mem_mode, mem_addr, x, x_addr, /*mem_canonicalized=*/true); } /* Returns nonzero if a write to X might alias a previous read from (or, if WRITEP is true, a write to) MEM. If X_CANONCALIZED is true, then X_ADDR is the canonicalized address of X, and X_MODE the mode for that access. If MEM_CANONICALIZED is true, MEM is canonicalized. */ static int write_dependence_p (const_rtx mem, const_rtx x, machine_mode x_mode, rtx x_addr, bool mem_canonicalized, bool x_canonicalized, bool writep) { rtx mem_addr; rtx true_mem_addr, true_x_addr; rtx base; int ret; gcc_checking_assert (x_canonicalized ? (x_addr != NULL_RTX && x_mode != VOIDmode) : (x_addr == NULL_RTX && x_mode == VOIDmode)); if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) return 1; /* (mem:BLK (scratch)) is a special mechanism to conflict with everything. This is used in epilogue deallocation functions. */ if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH) return 1; if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH) return 1; if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER) return 1; if (!x_addr) x_addr = XEXP (x, 0); true_x_addr = get_addr (x_addr); mem_addr = XEXP (mem, 0); true_mem_addr = get_addr (mem_addr); /* A read from read-only memory can't conflict with read-write memory. Don't assume anything when AND addresses are involved and leave to the code below to determine dependence. */ if (!writep && MEM_READONLY_P (mem) && GET_CODE (true_x_addr) != AND && GET_CODE (true_mem_addr) != AND) return 0; /* If we have MEMs referring to different address spaces (which can potentially overlap), we cannot easily tell from the addresses whether the references overlap. */ if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x)) return 1; base = find_base_term (true_mem_addr); if (! writep && base && (GET_CODE (base) == LABEL_REF || (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base)))) return 0; rtx x_base = find_base_term (true_x_addr); if (! base_alias_check (true_x_addr, x_base, true_mem_addr, base, GET_MODE (x), GET_MODE (mem))) return 0; if (!x_canonicalized) { x_addr = canon_rtx (true_x_addr); x_mode = GET_MODE (x); } if (!mem_canonicalized) mem_addr = canon_rtx (true_mem_addr); if ((ret = memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr, GET_MODE_SIZE (x_mode), x_addr, 0)) != -1) return ret; if (nonoverlapping_memrefs_p (x, mem, false)) return 0; return rtx_refs_may_alias_p (x, mem, false); } /* Anti dependence: X is written after read in MEM takes place. */ int anti_dependence (const_rtx mem, const_rtx x) { return write_dependence_p (mem, x, VOIDmode, NULL_RTX, /*mem_canonicalized=*/false, /*x_canonicalized*/false, /*writep=*/false); } /* Likewise, but we already have a canonicalized MEM, and X_ADDR for X. Also, consider X in X_MODE (which might be from an enclosing STRICT_LOW_PART / ZERO_EXTRACT). If MEM_CANONICALIZED is true, MEM is canonicalized. */ int canon_anti_dependence (const_rtx mem, bool mem_canonicalized, const_rtx x, machine_mode x_mode, rtx x_addr) { return write_dependence_p (mem, x, x_mode, x_addr, mem_canonicalized, /*x_canonicalized=*/true, /*writep=*/false); } /* Output dependence: X is written after store in MEM takes place. */ int output_dependence (const_rtx mem, const_rtx x) { return write_dependence_p (mem, x, VOIDmode, NULL_RTX, /*mem_canonicalized=*/false, /*x_canonicalized*/false, /*writep=*/true); } /* Check whether X may be aliased with MEM. Don't do offset-based memory disambiguation & TBAA. */ int may_alias_p (const_rtx mem, const_rtx x) { rtx x_addr, mem_addr; if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) return 1; /* (mem:BLK (scratch)) is a special mechanism to conflict with everything. This is used in epilogue deallocation functions. */ if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH) return 1; if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH) return 1; if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER) return 1; x_addr = XEXP (x, 0); x_addr = get_addr (x_addr); mem_addr = XEXP (mem, 0); mem_addr = get_addr (mem_addr); /* Read-only memory is by definition never modified, and therefore can't conflict with anything. However, don't assume anything when AND addresses are involved and leave to the code below to determine dependence. We don't expect to find read-only set on MEM, but stupid user tricks can produce them, so don't die. */ if (MEM_READONLY_P (x) && GET_CODE (x_addr) != AND && GET_CODE (mem_addr) != AND) return 0; /* If we have MEMs referring to different address spaces (which can potentially overlap), we cannot easily tell from the addresses whether the references overlap. */ if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x)) return 1; rtx x_base = find_base_term (x_addr); rtx mem_base = find_base_term (mem_addr); if (! base_alias_check (x_addr, x_base, mem_addr, mem_base, GET_MODE (x), GET_MODE (mem_addr))) return 0; if (nonoverlapping_memrefs_p (mem, x, true)) return 0; /* TBAA not valid for loop_invarint */ return rtx_refs_may_alias_p (x, mem, false); } void init_alias_target (void) { int i; if (!arg_base_value) arg_base_value = gen_rtx_ADDRESS (VOIDmode, 0); memset (static_reg_base_value, 0, sizeof static_reg_base_value); for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) /* Check whether this register can hold an incoming pointer argument. FUNCTION_ARG_REGNO_P tests outgoing register numbers, so translate if necessary due to register windows. */ if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i)) && HARD_REGNO_MODE_OK (i, Pmode)) static_reg_base_value[i] = arg_base_value; static_reg_base_value[STACK_POINTER_REGNUM] = unique_base_value (UNIQUE_BASE_VALUE_SP); static_reg_base_value[ARG_POINTER_REGNUM] = unique_base_value (UNIQUE_BASE_VALUE_ARGP); static_reg_base_value[FRAME_POINTER_REGNUM] = unique_base_value (UNIQUE_BASE_VALUE_FP); if (!HARD_FRAME_POINTER_IS_FRAME_POINTER) static_reg_base_value[HARD_FRAME_POINTER_REGNUM] = unique_base_value (UNIQUE_BASE_VALUE_HFP); } /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed to be memory reference. */ static bool memory_modified; static void memory_modified_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED, void *data) { if (MEM_P (x)) { if (anti_dependence (x, (const_rtx)data) || output_dependence (x, (const_rtx)data)) memory_modified = true; } } /* Return true when INSN possibly modify memory contents of MEM (i.e. address can be modified). */ bool memory_modified_in_insn_p (const_rtx mem, const_rtx insn) { if (!INSN_P (insn)) return false; memory_modified = false; note_stores (PATTERN (insn), memory_modified_1, CONST_CAST_RTX(mem)); return memory_modified; } /* Return TRUE if the destination of a set is rtx identical to ITEM. */ static inline bool set_dest_equal_p (const_rtx set, const_rtx item) { rtx dest = SET_DEST (set); return rtx_equal_p (dest, item); } /* Like memory_modified_in_insn_p, but return TRUE if INSN will *DEFINITELY* modify the memory contents of MEM. */ bool memory_must_be_modified_in_insn_p (const_rtx mem, const_rtx insn) { if (!INSN_P (insn)) return false; insn = PATTERN (insn); if (GET_CODE (insn) == SET) return set_dest_equal_p (insn, mem); else if (GET_CODE (insn) == PARALLEL) { int i; for (i = 0; i < XVECLEN (insn, 0); i++) { rtx sub = XVECEXP (insn, 0, i); if (GET_CODE (sub) == SET && set_dest_equal_p (sub, mem)) return true; } } return false; } /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE array. */ void init_alias_analysis (void) { unsigned int maxreg = max_reg_num (); int changed, pass; int i; unsigned int ui; rtx_insn *insn; rtx val; int rpo_cnt; int *rpo; timevar_push (TV_ALIAS_ANALYSIS); vec_safe_grow_cleared (reg_known_value, maxreg - FIRST_PSEUDO_REGISTER); reg_known_equiv_p = sbitmap_alloc (maxreg - FIRST_PSEUDO_REGISTER); bitmap_clear (reg_known_equiv_p); /* If we have memory allocated from the previous run, use it. */ if (old_reg_base_value) reg_base_value = old_reg_base_value; if (reg_base_value) reg_base_value->truncate (0); vec_safe_grow_cleared (reg_base_value, maxreg); new_reg_base_value = XNEWVEC (rtx, maxreg); reg_seen = sbitmap_alloc (maxreg); /* The basic idea is that each pass through this loop will use the "constant" information from the previous pass to propagate alias information through another level of assignments. The propagation is done on the CFG in reverse post-order, to propagate things forward as far as possible in each iteration. This could get expensive if the assignment chains are long. Maybe we should throttle the number of iterations, possibly based on the optimization level or flag_expensive_optimizations. We could propagate more information in the first pass by making use of DF_REG_DEF_COUNT to determine immediately that the alias information for a pseudo is "constant". A program with an uninitialized variable can cause an infinite loop here. Instead of doing a full dataflow analysis to detect such problems we just cap the number of iterations for the loop. The state of the arrays for the set chain in question does not matter since the program has undefined behavior. */ rpo = XNEWVEC (int, n_basic_blocks_for_fn (cfun)); rpo_cnt = pre_and_rev_post_order_compute (NULL, rpo, false); pass = 0; do { /* Assume nothing will change this iteration of the loop. */ changed = 0; /* We want to assign the same IDs each iteration of this loop, so start counting from one each iteration of the loop. */ unique_id = 1; /* We're at the start of the function each iteration through the loop, so we're copying arguments. */ copying_arguments = true; /* Wipe the potential alias information clean for this pass. */ memset (new_reg_base_value, 0, maxreg * sizeof (rtx)); /* Wipe the reg_seen array clean. */ bitmap_clear (reg_seen); /* Initialize the alias information for this pass. */ for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) if (static_reg_base_value[i]) { new_reg_base_value[i] = static_reg_base_value[i]; bitmap_set_bit (reg_seen, i); } /* Walk the insns adding values to the new_reg_base_value array. */ for (i = 0; i < rpo_cnt; i++) { basic_block bb = BASIC_BLOCK_FOR_FN (cfun, rpo[i]); FOR_BB_INSNS (bb, insn) { if (NONDEBUG_INSN_P (insn)) { rtx note, set; #if defined (HAVE_prologue) static const bool prologue = true; #else static const bool prologue = false; #endif /* The prologue/epilogue insns are not threaded onto the insn chain until after reload has completed. Thus, there is no sense wasting time checking if INSN is in the prologue/epilogue until after reload has completed. */ if ((prologue || HAVE_epilogue) && reload_completed && prologue_epilogue_contains (insn)) continue; /* If this insn has a noalias note, process it, Otherwise, scan for sets. A simple set will have no side effects which could change the base value of any other register. */ if (GET_CODE (PATTERN (insn)) == SET && REG_NOTES (insn) != 0 && find_reg_note (insn, REG_NOALIAS, NULL_RTX)) record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL); else note_stores (PATTERN (insn), record_set, NULL); set = single_set (insn); if (set != 0 && REG_P (SET_DEST (set)) && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER) { unsigned int regno = REGNO (SET_DEST (set)); rtx src = SET_SRC (set); rtx t; note = find_reg_equal_equiv_note (insn); if (note && REG_NOTE_KIND (note) == REG_EQUAL && DF_REG_DEF_COUNT (regno) != 1) note = NULL_RTX; if (note != NULL_RTX && GET_CODE (XEXP (note, 0)) != EXPR_LIST && ! rtx_varies_p (XEXP (note, 0), 1) && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0))) { set_reg_known_value (regno, XEXP (note, 0)); set_reg_known_equiv_p (regno, REG_NOTE_KIND (note) == REG_EQUIV); } else if (DF_REG_DEF_COUNT (regno) == 1 && GET_CODE (src) == PLUS && REG_P (XEXP (src, 0)) && (t = get_reg_known_value (REGNO (XEXP (src, 0)))) && CONST_INT_P (XEXP (src, 1))) { t = plus_constant (GET_MODE (src), t, INTVAL (XEXP (src, 1))); set_reg_known_value (regno, t); set_reg_known_equiv_p (regno, false); } else if (DF_REG_DEF_COUNT (regno) == 1 && ! rtx_varies_p (src, 1)) { set_reg_known_value (regno, src); set_reg_known_equiv_p (regno, false); } } } else if (NOTE_P (insn) && NOTE_KIND (insn) == NOTE_INSN_FUNCTION_BEG) copying_arguments = false; } } /* Now propagate values from new_reg_base_value to reg_base_value. */ gcc_assert (maxreg == (unsigned int) max_reg_num ()); for (ui = 0; ui < maxreg; ui++) { if (new_reg_base_value[ui] && new_reg_base_value[ui] != (*reg_base_value)[ui] && ! rtx_equal_p (new_reg_base_value[ui], (*reg_base_value)[ui])) { (*reg_base_value)[ui] = new_reg_base_value[ui]; changed = 1; } } } while (changed && ++pass < MAX_ALIAS_LOOP_PASSES); XDELETEVEC (rpo); /* Fill in the remaining entries. */ FOR_EACH_VEC_ELT (*reg_known_value, i, val) { int regno = i + FIRST_PSEUDO_REGISTER; if (! val) set_reg_known_value (regno, regno_reg_rtx[regno]); } /* Clean up. */ free (new_reg_base_value); new_reg_base_value = 0; sbitmap_free (reg_seen); reg_seen = 0; timevar_pop (TV_ALIAS_ANALYSIS); } /* Equate REG_BASE_VALUE (reg1) to REG_BASE_VALUE (reg2). Special API for var-tracking pass purposes. */ void vt_equate_reg_base_value (const_rtx reg1, const_rtx reg2) { (*reg_base_value)[REGNO (reg1)] = REG_BASE_VALUE (reg2); } void end_alias_analysis (void) { old_reg_base_value = reg_base_value; vec_free (reg_known_value); sbitmap_free (reg_known_equiv_p); } void dump_alias_stats_in_alias_c (FILE *s) { fprintf (s, " TBAA oracle: %llu disambiguations %llu queries\n" " %llu are in alias set 0\n" " %llu queries asked about the same object\n" " %llu queries asked about the same alias set\n" " %llu access volatile\n" " %llu are dependent in the DAG\n" " %llu are aritificially in conflict with void *\n", alias_stats.num_disambiguated, alias_stats.num_alias_zero + alias_stats.num_same_alias_set + alias_stats.num_same_objects + alias_stats.num_volatile + alias_stats.num_dag + alias_stats.num_disambiguated + alias_stats.num_universal, alias_stats.num_alias_zero, alias_stats.num_same_alias_set, alias_stats.num_same_objects, alias_stats.num_volatile, alias_stats.num_dag, alias_stats.num_universal); } #include "gt-alias.h"