diff options
Diffstat (limited to 'gcc/tree-loop-distribution.c')
| -rw-r--r-- | gcc/tree-loop-distribution.c | 518 |
1 files changed, 489 insertions, 29 deletions
diff --git a/gcc/tree-loop-distribution.c b/gcc/tree-loop-distribution.c index 2df762c..fb92500 100644 --- a/gcc/tree-loop-distribution.c +++ b/gcc/tree-loop-distribution.c @@ -116,6 +116,10 @@ along with GCC; see the file COPYING3. If not see #include "tree-eh.h" #include "gimple-fold.h" #include "tree-affine.h" +#include "intl.h" +#include "rtl.h" +#include "memmodel.h" +#include "optabs.h" #define MAX_DATAREFS_NUM \ @@ -651,6 +655,10 @@ class loop_distribution control_dependences *cd, int *nb_calls, bool *destroy_p, bool only_patterns_p); + /* Transform loops which mimic the effects of builtins rawmemchr or strlen and + replace them accordingly. */ + bool transform_reduction_loop (loop_p loop); + /* Compute topological order for basic blocks. Topological order is needed because data dependence is computed for data references in lexicographical order. */ @@ -1492,14 +1500,14 @@ loop_distribution::build_rdg_partition_for_vertex (struct graph *rdg, int v) data references. */ static bool -find_single_drs (class loop *loop, struct graph *rdg, partition *partition, +find_single_drs (class loop *loop, struct graph *rdg, const bitmap &partition_stmts, data_reference_p *dst_dr, data_reference_p *src_dr) { unsigned i; data_reference_p single_ld = NULL, single_st = NULL; bitmap_iterator bi; - EXECUTE_IF_SET_IN_BITMAP (partition->stmts, 0, i, bi) + EXECUTE_IF_SET_IN_BITMAP (partition_stmts, 0, i, bi) { gimple *stmt = RDG_STMT (rdg, i); data_reference_p dr; @@ -1540,44 +1548,47 @@ find_single_drs (class loop *loop, struct graph *rdg, partition *partition, } } - if (!single_st) - return false; - - /* Bail out if this is a bitfield memory reference. */ - if (TREE_CODE (DR_REF (single_st)) == COMPONENT_REF - && DECL_BIT_FIELD (TREE_OPERAND (DR_REF (single_st), 1))) + if (!single_ld && !single_st) return false; - /* Data reference must be executed exactly once per iteration of each - loop in the loop nest. We only need to check dominance information - against the outermost one in a perfect loop nest because a bb can't - dominate outermost loop's latch without dominating inner loop's. */ - basic_block bb_st = gimple_bb (DR_STMT (single_st)); - if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb_st)) - return false; + basic_block bb_ld = NULL; + basic_block bb_st = NULL; if (single_ld) { - gimple *store = DR_STMT (single_st), *load = DR_STMT (single_ld); - /* Direct aggregate copy or via an SSA name temporary. */ - if (load != store - && gimple_assign_lhs (load) != gimple_assign_rhs1 (store)) - return false; - /* Bail out if this is a bitfield memory reference. */ if (TREE_CODE (DR_REF (single_ld)) == COMPONENT_REF && DECL_BIT_FIELD (TREE_OPERAND (DR_REF (single_ld), 1))) return false; - /* Load and store must be in the same loop nest. */ - basic_block bb_ld = gimple_bb (DR_STMT (single_ld)); - if (bb_st->loop_father != bb_ld->loop_father) + /* Data reference must be executed exactly once per iteration of each + loop in the loop nest. We only need to check dominance information + against the outermost one in a perfect loop nest because a bb can't + dominate outermost loop's latch without dominating inner loop's. */ + bb_ld = gimple_bb (DR_STMT (single_ld)); + if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb_ld)) + return false; + } + + if (single_st) + { + /* Bail out if this is a bitfield memory reference. */ + if (TREE_CODE (DR_REF (single_st)) == COMPONENT_REF + && DECL_BIT_FIELD (TREE_OPERAND (DR_REF (single_st), 1))) return false; /* Data reference must be executed exactly once per iteration. - Same as single_st, we only need to check against the outermost + Same as single_ld, we only need to check against the outermost loop. */ - if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb_ld)) + bb_st = gimple_bb (DR_STMT (single_st)); + if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb_st)) + return false; + } + + if (single_ld && single_st) + { + /* Load and store must be in the same loop nest. */ + if (bb_st->loop_father != bb_ld->loop_father) return false; edge e = single_exit (bb_st->loop_father); @@ -1852,9 +1863,19 @@ loop_distribution::classify_partition (loop_p loop, return has_reduction; /* Find single load/store data references for builtin partition. */ - if (!find_single_drs (loop, rdg, partition, &single_st, &single_ld)) + if (!find_single_drs (loop, rdg, partition->stmts, &single_st, &single_ld) + || !single_st) return has_reduction; + if (single_ld && single_st) + { + gimple *store = DR_STMT (single_st), *load = DR_STMT (single_ld); + /* Direct aggregate copy or via an SSA name temporary. */ + if (load != store + && gimple_assign_lhs (load) != gimple_assign_rhs1 (store)) + return has_reduction; + } + partition->loc = gimple_location (DR_STMT (single_st)); /* Classify the builtin kind. */ @@ -3260,6 +3281,428 @@ find_seed_stmts_for_distribution (class loop *loop, vec<gimple *> *work_list) return work_list->length () > 0; } +/* A helper function for generate_{rawmemchr,strlen}_builtin functions in order + to place new statements SEQ before LOOP and replace the old reduction + variable with the new one. */ + +static void +generate_reduction_builtin_1 (loop_p loop, gimple_seq &seq, + tree reduction_var_old, tree reduction_var_new, + const char *info, machine_mode load_mode) +{ + /* Place new statements before LOOP. */ + gimple_stmt_iterator gsi = gsi_last_bb (loop_preheader_edge (loop)->src); + gsi_insert_seq_after (&gsi, seq, GSI_CONTINUE_LINKING); + + /* Replace old reduction variable with new one. */ + imm_use_iterator iter; + gimple *stmt; + use_operand_p use_p; + FOR_EACH_IMM_USE_STMT (stmt, iter, reduction_var_old) + { + FOR_EACH_IMM_USE_ON_STMT (use_p, iter) + SET_USE (use_p, reduction_var_new); + + update_stmt (stmt); + } + + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, info, GET_MODE_NAME (load_mode)); +} + +/* Generate a call to rawmemchr and place it before LOOP. REDUCTION_VAR is + replaced with a fresh SSA name representing the result of the call. */ + +static void +generate_rawmemchr_builtin (loop_p loop, tree reduction_var, + data_reference_p store_dr, tree base, tree pattern, + location_t loc) +{ + gimple_seq seq = NULL; + + tree mem = force_gimple_operand (base, &seq, true, NULL_TREE); + gimple *fn_call = gimple_build_call_internal (IFN_RAWMEMCHR, 2, mem, pattern); + tree reduction_var_new = copy_ssa_name (reduction_var); + gimple_call_set_lhs (fn_call, reduction_var_new); + gimple_set_location (fn_call, loc); + gimple_seq_add_stmt (&seq, fn_call); + + if (store_dr) + { + gassign *g = gimple_build_assign (DR_REF (store_dr), reduction_var_new); + gimple_seq_add_stmt (&seq, g); + } + + generate_reduction_builtin_1 (loop, seq, reduction_var, reduction_var_new, + "generated rawmemchr%s\n", + TYPE_MODE (TREE_TYPE (TREE_TYPE (base)))); +} + +/* Helper function for generate_strlen_builtin(,_using_rawmemchr) */ + +static void +generate_strlen_builtin_1 (loop_p loop, gimple_seq &seq, + tree reduction_var_old, tree reduction_var_new, + machine_mode mode, tree start_len) +{ + /* REDUCTION_VAR_NEW has either size type or ptrdiff type and must be + converted if types of old and new reduction variable are not compatible. */ + reduction_var_new = gimple_convert (&seq, TREE_TYPE (reduction_var_old), + reduction_var_new); + + /* Loops of the form `for (i=42; s[i]; ++i);` have an additional start + length. */ + if (!integer_zerop (start_len)) + { + tree lhs = make_ssa_name (TREE_TYPE (reduction_var_new)); + gimple *g = gimple_build_assign (lhs, PLUS_EXPR, reduction_var_new, + start_len); + gimple_seq_add_stmt (&seq, g); + reduction_var_new = lhs; + } + + generate_reduction_builtin_1 (loop, seq, reduction_var_old, reduction_var_new, + "generated strlen%s\n", mode); +} + +/* Generate a call to strlen and place it before LOOP. REDUCTION_VAR is + replaced with a fresh SSA name representing the result of the call. */ + +static void +generate_strlen_builtin (loop_p loop, tree reduction_var, tree base, + tree start_len, location_t loc) +{ + gimple_seq seq = NULL; + + tree reduction_var_new = make_ssa_name (size_type_node); + + tree mem = force_gimple_operand (base, &seq, true, NULL_TREE); + tree fn = build_fold_addr_expr (builtin_decl_implicit (BUILT_IN_STRLEN)); + gimple *fn_call = gimple_build_call (fn, 1, mem); + gimple_call_set_lhs (fn_call, reduction_var_new); + gimple_set_location (fn_call, loc); + gimple_seq_add_stmt (&seq, fn_call); + + generate_strlen_builtin_1 (loop, seq, reduction_var, reduction_var_new, + QImode, start_len); +} + +/* Generate code in order to mimic the behaviour of strlen but this time over + an array of elements with mode different than QI. REDUCTION_VAR is replaced + with a fresh SSA name representing the result, i.e., the length. */ + +static void +generate_strlen_builtin_using_rawmemchr (loop_p loop, tree reduction_var, + tree base, tree load_type, + tree start_len, location_t loc) +{ + gimple_seq seq = NULL; + + tree start = force_gimple_operand (base, &seq, true, NULL_TREE); + tree zero = build_zero_cst (load_type); + gimple *fn_call = gimple_build_call_internal (IFN_RAWMEMCHR, 2, start, zero); + tree end = make_ssa_name (TREE_TYPE (base)); + gimple_call_set_lhs (fn_call, end); + gimple_set_location (fn_call, loc); + gimple_seq_add_stmt (&seq, fn_call); + + /* Determine the number of elements between START and END by + evaluating (END - START) / sizeof (*START). */ + tree diff = make_ssa_name (ptrdiff_type_node); + gimple *diff_stmt = gimple_build_assign (diff, POINTER_DIFF_EXPR, end, start); + gimple_seq_add_stmt (&seq, diff_stmt); + /* Let SIZE be the size of each character. */ + tree size = gimple_convert (&seq, ptrdiff_type_node, + TYPE_SIZE_UNIT (load_type)); + tree count = make_ssa_name (ptrdiff_type_node); + gimple *count_stmt = gimple_build_assign (count, TRUNC_DIV_EXPR, diff, size); + gimple_seq_add_stmt (&seq, count_stmt); + + generate_strlen_builtin_1 (loop, seq, reduction_var, count, + TYPE_MODE (load_type), + start_len); +} + +/* Return true if we can count at least as many characters by taking pointer + difference as we can count via reduction_var without an overflow. Thus + compute 2^n < (2^(m-1) / s) where n = TYPE_PRECISION (reduction_var), + m = TYPE_PRECISION (ptrdiff_type_node), and s = size of each character. */ +static bool +reduction_var_overflows_first (tree reduction_var, tree load_type) +{ + widest_int n2 = wi::lshift (1, TYPE_PRECISION (reduction_var));; + widest_int m2 = wi::lshift (1, TYPE_PRECISION (ptrdiff_type_node) - 1); + widest_int s = wi::to_widest (TYPE_SIZE_UNIT (load_type)); + return wi::ltu_p (n2, wi::udiv_trunc (m2, s)); +} + +static gimple * +determine_reduction_stmt_1 (const loop_p loop, const basic_block *bbs) +{ + gimple *reduction_stmt = NULL; + + for (unsigned i = 0, ninsns = 0; i < loop->num_nodes; ++i) + { + basic_block bb = bbs[i]; + + for (gphi_iterator bsi = gsi_start_phis (bb); !gsi_end_p (bsi); + gsi_next_nondebug (&bsi)) + { + gphi *phi = bsi.phi (); + if (virtual_operand_p (gimple_phi_result (phi))) + continue; + if (stmt_has_scalar_dependences_outside_loop (loop, phi)) + { + if (reduction_stmt) + return NULL; + reduction_stmt = phi; + } + } + + for (gimple_stmt_iterator bsi = gsi_start_bb (bb); !gsi_end_p (bsi); + gsi_next_nondebug (&bsi), ++ninsns) + { + /* Bail out early for loops which are unlikely to match. */ + if (ninsns > 16) + return NULL; + gimple *stmt = gsi_stmt (bsi); + if (gimple_clobber_p (stmt)) + continue; + if (gimple_code (stmt) == GIMPLE_LABEL) + continue; + if (gimple_has_volatile_ops (stmt)) + return NULL; + if (stmt_has_scalar_dependences_outside_loop (loop, stmt)) + { + if (reduction_stmt) + return NULL; + reduction_stmt = stmt; + } + } + } + + return reduction_stmt; +} + +/* If LOOP has a single non-volatile reduction statement, then return a pointer + to it. Otherwise return NULL. */ +static gimple * +determine_reduction_stmt (const loop_p loop) +{ + basic_block *bbs = get_loop_body (loop); + gimple *reduction_stmt = determine_reduction_stmt_1 (loop, bbs); + XDELETEVEC (bbs); + return reduction_stmt; +} + +/* Transform loops which mimic the effects of builtins rawmemchr or strlen and + replace them accordingly. For example, a loop of the form + + for (; *p != 42; ++p); + + is replaced by + + p = rawmemchr<MODE> (p, 42); + + under the assumption that rawmemchr is available for a particular MODE. + Another example is + + int i; + for (i = 42; s[i]; ++i); + + which is replaced by + + i = (int)strlen (&s[42]) + 42; + + for some character array S. In case array S is not of type character array + we end up with + + i = (int)(rawmemchr<MODE> (&s[42], 0) - &s[42]) + 42; + + assuming that rawmemchr is available for a particular MODE. */ + +bool +loop_distribution::transform_reduction_loop (loop_p loop) +{ + gimple *reduction_stmt; + data_reference_p load_dr = NULL, store_dr = NULL; + + edge e = single_exit (loop); + gcond *cond = safe_dyn_cast <gcond *> (last_stmt (e->src)); + if (!cond) + return false; + /* Ensure loop condition is an (in)equality test and loop is exited either if + the inequality test fails or the equality test succeeds. */ + if (!(e->flags & EDGE_FALSE_VALUE && gimple_cond_code (cond) == NE_EXPR) + && !(e->flags & EDGE_TRUE_VALUE && gimple_cond_code (cond) == EQ_EXPR)) + return false; + /* A limitation of the current implementation is that we only support + constant patterns in (in)equality tests. */ + tree pattern = gimple_cond_rhs (cond); + if (TREE_CODE (pattern) != INTEGER_CST) + return false; + + reduction_stmt = determine_reduction_stmt (loop); + + /* A limitation of the current implementation is that we require a reduction + statement. Therefore, loops without a reduction statement as in the + following are not recognized: + int *p; + void foo (void) { for (; *p; ++p); } */ + if (reduction_stmt == NULL) + return false; + + /* Reduction variables are guaranteed to be SSA names. */ + tree reduction_var; + switch (gimple_code (reduction_stmt)) + { + case GIMPLE_ASSIGN: + case GIMPLE_PHI: + reduction_var = gimple_get_lhs (reduction_stmt); + break; + default: + /* Bail out e.g. for GIMPLE_CALL. */ + return false; + } + + struct graph *rdg = build_rdg (loop, NULL); + if (rdg == NULL) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, + "Loop %d not transformed: failed to build the RDG.\n", + loop->num); + + return false; + } + auto_bitmap partition_stmts; + bitmap_set_range (partition_stmts, 0, rdg->n_vertices); + find_single_drs (loop, rdg, partition_stmts, &store_dr, &load_dr); + free_rdg (rdg); + + /* Bail out if there is no single load. */ + if (load_dr == NULL) + return false; + + /* Reaching this point we have a loop with a single reduction variable, + a single load, and an optional single store. */ + + tree load_ref = DR_REF (load_dr); + tree load_type = TREE_TYPE (load_ref); + tree load_access_base = build_fold_addr_expr (load_ref); + tree load_access_size = TYPE_SIZE_UNIT (load_type); + affine_iv load_iv, reduction_iv; + + if (!INTEGRAL_TYPE_P (load_type) + || !type_has_mode_precision_p (load_type)) + return false; + + /* We already ensured that the loop condition tests for (in)equality where the + rhs is a constant pattern. Now ensure that the lhs is the result of the + load. */ + if (gimple_cond_lhs (cond) != gimple_assign_lhs (DR_STMT (load_dr))) + return false; + + /* Bail out if no affine induction variable with constant step can be + determined. */ + if (!simple_iv (loop, loop, load_access_base, &load_iv, false)) + return false; + + /* Bail out if memory accesses are not consecutive or not growing. */ + if (!operand_equal_p (load_iv.step, load_access_size, 0)) + return false; + + if (!simple_iv (loop, loop, reduction_var, &reduction_iv, false)) + return false; + + /* Handle rawmemchr like loops. */ + if (operand_equal_p (load_iv.base, reduction_iv.base) + && operand_equal_p (load_iv.step, reduction_iv.step)) + { + if (store_dr) + { + /* Ensure that we store to X and load from X+I where I>0. */ + if (TREE_CODE (load_iv.base) != POINTER_PLUS_EXPR + || !integer_onep (TREE_OPERAND (load_iv.base, 1))) + return false; + tree ptr_base = TREE_OPERAND (load_iv.base, 0); + if (TREE_CODE (ptr_base) != SSA_NAME) + return false; + gimple *def = SSA_NAME_DEF_STMT (ptr_base); + if (!gimple_assign_single_p (def) + || gimple_assign_rhs1 (def) != DR_REF (store_dr)) + return false; + /* Ensure that the reduction value is stored. */ + if (gimple_assign_rhs1 (DR_STMT (store_dr)) != reduction_var) + return false; + } + /* Bail out if target does not provide rawmemchr for a certain mode. */ + machine_mode mode = TYPE_MODE (load_type); + if (direct_optab_handler (rawmemchr_optab, mode) == CODE_FOR_nothing) + return false; + location_t loc = gimple_location (DR_STMT (load_dr)); + generate_rawmemchr_builtin (loop, reduction_var, store_dr, load_iv.base, + pattern, loc); + return true; + } + + /* Handle strlen like loops. */ + if (store_dr == NULL + && integer_zerop (pattern) + && TREE_CODE (reduction_iv.base) == INTEGER_CST + && TREE_CODE (reduction_iv.step) == INTEGER_CST + && integer_onep (reduction_iv.step)) + { + location_t loc = gimple_location (DR_STMT (load_dr)); + /* While determining the length of a string an overflow might occur. + If an overflow only occurs in the loop implementation and not in the + strlen implementation, then either the overflow is undefined or the + truncated result of strlen equals the one of the loop. Otherwise if + an overflow may also occur in the strlen implementation, then + replacing a loop by a call to strlen is sound whenever we ensure that + if an overflow occurs in the strlen implementation, then also an + overflow occurs in the loop implementation which is undefined. It + seems reasonable to relax this and assume that the strlen + implementation cannot overflow in case sizetype is big enough in the + sense that an overflow can only happen for string objects which are + bigger than half of the address space; at least for 32-bit targets and + up. + + For strlen which makes use of rawmemchr the maximal length of a string + which can be determined without an overflow is PTRDIFF_MAX / S where + each character has size S. Since an overflow for ptrdiff type is + undefined we have to make sure that if an overflow occurs, then an + overflow occurs in the loop implementation, too, and this is + undefined, too. Similar as before we relax this and assume that no + string object is larger than half of the address space; at least for + 32-bit targets and up. */ + if (TYPE_MODE (load_type) == TYPE_MODE (char_type_node) + && TYPE_PRECISION (load_type) == TYPE_PRECISION (char_type_node) + && ((TYPE_PRECISION (sizetype) >= TYPE_PRECISION (ptr_type_node) - 1 + && TYPE_PRECISION (ptr_type_node) >= 32) + || (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (reduction_var)) + && TYPE_PRECISION (reduction_var) <= TYPE_PRECISION (sizetype))) + && builtin_decl_implicit (BUILT_IN_STRLEN)) + generate_strlen_builtin (loop, reduction_var, load_iv.base, + reduction_iv.base, loc); + else if (direct_optab_handler (rawmemchr_optab, TYPE_MODE (load_type)) + != CODE_FOR_nothing + && ((TYPE_PRECISION (ptrdiff_type_node) == TYPE_PRECISION (ptr_type_node) + && TYPE_PRECISION (ptrdiff_type_node) >= 32) + || (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (reduction_var)) + && reduction_var_overflows_first (reduction_var, load_type)))) + generate_strlen_builtin_using_rawmemchr (loop, reduction_var, + load_iv.base, + load_type, + reduction_iv.base, loc); + else + return false; + return true; + } + + return false; +} + /* Given innermost LOOP, return the outermost enclosing loop that forms a perfect loop nest. */ @@ -3324,10 +3767,27 @@ loop_distribution::execute (function *fun) && !optimize_loop_for_speed_p (loop))) continue; - /* Don't distribute loop if niters is unknown. */ + /* If niters is unknown don't distribute loop but rather try to transform + it to a call to a builtin. */ tree niters = number_of_latch_executions (loop); if (niters == NULL_TREE || niters == chrec_dont_know) - continue; + { + datarefs_vec.create (20); + if (transform_reduction_loop (loop)) + { + changed = true; + loops_to_be_destroyed.safe_push (loop); + if (dump_enabled_p ()) + { + dump_user_location_t loc = find_loop_location (loop); + dump_printf_loc (MSG_OPTIMIZED_LOCATIONS, + loc, "Loop %d transformed into a builtin.\n", + loop->num); + } + } + free_data_refs (datarefs_vec); + continue; + } /* Get the perfect loop nest for distribution. */ loop = prepare_perfect_loop_nest (loop); |