diff options
author | Richard Sandiford <rdsandiford@googlemail.com> | 2012-04-17 17:01:02 +0000 |
---|---|---|
committer | Richard Sandiford <rsandifo@gcc.gnu.org> | 2012-04-17 17:01:02 +0000 |
commit | 9fc37b2b7bd36846fa166fe8f9911a9ec8c6978a (patch) | |
tree | 0484afa16b93c9b332431c182e386302b377eccc /gcc/alias.c | |
parent | ac9ce934ed56bc46b865adb396adbf35a1e5a7a1 (diff) | |
download | gcc-9fc37b2b7bd36846fa166fe8f9911a9ec8c6978a.zip gcc-9fc37b2b7bd36846fa166fe8f9911a9ec8c6978a.tar.gz gcc-9fc37b2b7bd36846fa166fe8f9911a9ec8c6978a.tar.bz2 |
rtl.def (ADDRESS): Turn operand into a HOST_WIDE_INT.
gcc/
* rtl.def (ADDRESS): Turn operand into a HOST_WIDE_INT.
* alias.c (reg_base_value): Expand and update comment.
(arg_base_value): New variable.
(unique_id): Move up file.
(unique_base_value, unique_base_value_p, known_base_value_p): New.
(find_base_value): Use arg_base_value and known_base_value_p.
(record_set): Document REG_NOALIAS handling. Use unique_base_value.
(find_base_term): Use known_base_value_p.
(base_alias_check): Use unique_base_value_p.
(init_alias_target): Initialize arg_base_value. Use unique_base_value.
(init_alias_analysis): Use 1 as the first id for REG_NOALIAS bases.
From-SVN: r186540
Diffstat (limited to 'gcc/alias.c')
-rw-r--r-- | gcc/alias.c | 145 |
1 files changed, 89 insertions, 56 deletions
diff --git a/gcc/alias.c b/gcc/alias.c index e9d701f..80c8759 100644 --- a/gcc/alias.c +++ b/gcc/alias.c @@ -187,21 +187,42 @@ static void memory_modified_1 (rtx, const_rtx, void *); of the first set. A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS - expressions represent certain special values: function arguments and - the stack, frame, and argument pointers. + expressions represent three types of base: - The contents of an ADDRESS is not normally used, the mode of the - ADDRESS determines whether the ADDRESS is a function argument or some - other special value. Pointer equality, not rtx_equal_p, determines whether - two ADDRESS expressions refer to the same base address. + 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. - The only use of the contents of an ADDRESS is for determining if the - current function performs nonlocal memory memory references for the - purposes of marking the function as a constant function. */ + 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(rtx,gc) *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. */ @@ -993,6 +1014,43 @@ get_frame_alias_set (void) 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 @@ -1049,7 +1107,7 @@ find_base_value (rtx src) && (XEXP (src, 0) == arg_pointer_rtx || (GET_CODE (XEXP (src, 0)) == PLUS && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx))) - return gen_rtx_ADDRESS (VOIDmode, src); + return arg_base_value; return 0; case CONST: @@ -1090,18 +1148,10 @@ find_base_value (rtx src) /* 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 - && (GET_CODE (src_0) == SYMBOL_REF - || GET_CODE (src_0) == LABEL_REF - || (GET_CODE (src_0) == ADDRESS - && GET_MODE (src_0) != VOIDmode))) + if (src_0 != 0 && known_base_value_p (src_0)) return src_0; - if (src_1 != 0 - && (GET_CODE (src_1) == SYMBOL_REF - || GET_CODE (src_1) == LABEL_REF - || (GET_CODE (src_1) == ADDRESS - && GET_MODE (src_1) != VOIDmode))) + if (src_1 != 0 && known_base_value_p (src_1)) return src_1; /* Guess which operand is the base address: @@ -1169,16 +1219,14 @@ find_base_value (rtx src) return 0; } -/* Called from init_alias_analysis indirectly through note_stores. */ +/* 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 char *reg_seen; -/* Addresses which are known not to alias anything else are identified - by a unique integer. */ -static int unique_id; - static void record_set (rtx dest, const_rtx set, void *data ATTRIBUTE_UNUSED) { @@ -1223,14 +1271,14 @@ record_set (rtx dest, const_rtx set, void *data ATTRIBUTE_UNUSED) } else { + /* There's a REG_NOALIAS note against DEST. */ if (reg_seen[regno]) { new_reg_base_value[regno] = 0; return; } reg_seen[regno] = 1; - new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode, - GEN_INT (unique_id++)); + new_reg_base_value[regno] = unique_base_value (unique_id++); return; } @@ -1666,18 +1714,10 @@ find_base_term (rtx x) /* If either base term is named object or a special address (like an argument or stack reference), then use it for the base term. */ - if (tmp1 != 0 - && (GET_CODE (tmp1) == SYMBOL_REF - || GET_CODE (tmp1) == LABEL_REF - || (GET_CODE (tmp1) == ADDRESS - && GET_MODE (tmp1) != VOIDmode))) + if (tmp1 != 0 && known_base_value_p (tmp1)) return tmp1; - if (tmp2 != 0 - && (GET_CODE (tmp2) == SYMBOL_REF - || GET_CODE (tmp2) == LABEL_REF - || (GET_CODE (tmp2) == ADDRESS - && GET_MODE (tmp2) != VOIDmode))) + if (tmp2 != 0 && known_base_value_p (tmp2)) return tmp2; /* We could not determine which of the two operands was the @@ -1762,12 +1802,7 @@ base_alias_check (rtx x, rtx y, enum machine_mode x_mode, if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS) return 0; - /* If one address is a stack reference there can be no alias: - stack references using different base registers do not alias, - a stack reference can not alias a parameter, and a stack reference - can not alias a global. */ - if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode) - || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode)) + if (unique_base_value_p (x_base) || unique_base_value_p (y_base)) return 0; return 1; @@ -2686,6 +2721,9 @@ 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++) @@ -2694,18 +2732,13 @@ init_alias_target (void) 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] - = gen_rtx_ADDRESS (VOIDmode, gen_rtx_REG (Pmode, i)); - - static_reg_base_value[STACK_POINTER_REGNUM] - = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx); - static_reg_base_value[ARG_POINTER_REGNUM] - = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx); - static_reg_base_value[FRAME_POINTER_REGNUM] - = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx); + static_reg_base_value[i] = arg_base_value; + + static_reg_base_value[STACK_POINTER_REGNUM] = unique_base_value (-1); + static_reg_base_value[ARG_POINTER_REGNUM] = unique_base_value (-2); + static_reg_base_value[FRAME_POINTER_REGNUM] = unique_base_value (-3); #if !HARD_FRAME_POINTER_IS_FRAME_POINTER - static_reg_base_value[HARD_FRAME_POINTER_REGNUM] - = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx); + static_reg_base_value[HARD_FRAME_POINTER_REGNUM] = unique_base_value (-4); #endif } @@ -2791,8 +2824,8 @@ init_alias_analysis (void) changed = 0; /* We want to assign the same IDs each iteration of this loop, so - start counting from zero each iteration of the loop. */ - unique_id = 0; + 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. */ |