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ssa-dce.c (note_inherently_necessary_set): New function.

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* ssa-dce.c (note_inherently_necessary_set): New function.
        (find_inherently_necessary): Use it.  Do not consider
        NOTEs, CODE_LABELs or BARRIERS are necessary.  Improve
        handling of asms and unspecs.
        (delete_insn_bb): Only delete INSNs, CALL_INSNs or JUMP_INSNs.

From-SVN: r43656
This commit is contained in:
Jeffrey A Law 2001-06-29 18:26:21 +00:00 committed by Jeff Law
parent 8d8e52be8a
commit 8f2f6da110
2 changed files with 59 additions and 25 deletions
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8
gcc/ChangeLog
View File

@ -1,3 +1,11 @@
Fri Jun 29 12:27:24 2001 Jeffrey A Law (law@cygnus.com)
* ssa-dce.c (note_inherently_necessary_set): New function.
(find_inherently_necessary): Use it. Do not consider
NOTEs, CODE_LABELs or BARRIERS are necessary. Improve
handling of asms and unspecs.
(delete_insn_bb): Only delete INSNs, CALL_INSNs or JUMP_INSNs.
2001-06-29 Joseph S. Myers <jsm28@cam.ac.uk>
* target.h (struct gcc_target): Add comp_type_attributes and

76
gcc/ssa-dce.c
View File

@ -113,6 +113,8 @@ static int find_inherently_necessary
PARAMS ((rtx current_rtx));
static int propagate_necessity_through_operand
PARAMS ((rtx *current_rtx, void *data));
static void note_inherently_necessary_set
PARAMS ((rtx, rtx, void *));
/* Unnecessary insns are indicated using insns' in_struct bit. */
@ -328,6 +330,31 @@ inherently_necessary_register (current_rtx)
&inherently_necessary_register_1, NULL);
}
/* Called via note_stores for each store in an insn. Note whether
or not a particular store is inherently necessary. Store a
nonzero value in inherently_necessary_p if such a storeis found. */
static void
note_inherently_necessary_set (dest, set, data)
rtx set;
rtx dest;
void *data;
{
int *inherently_necessary_set_p = (int *)data;
while (GET_CODE (dest) == SUBREG
|| GET_CODE (dest) == STRICT_LOW_PART
|| GET_CODE (dest) == ZERO_EXTRACT
|| GET_CODE (dest) == SIGN_EXTRACT)
dest = XEXP (dest, 0);
if (GET_CODE (dest) == MEM
|| GET_CODE (dest) == UNSPEC
|| GET_CODE (dest) == UNSPEC_VOLATILE)
*inherently_necessary_set_p = 1;
}
/* Mark X as inherently necessary if appropriate. For example,
function calls and storing values into memory are inherently
necessary. This function is to be used with for_each_rtx ().
@ -346,39 +373,29 @@ find_inherently_necessary (x)
switch (GET_CODE (x))
{
case CALL_INSN:
return !0;
case CODE_LABEL:
case NOTE:
case BARRIER:
return !0;
return 0;
break;
case JUMP_INSN:
return JUMP_TABLE_DATA_P (x) || computed_jump_p (x) != 0;
break;
case INSN:
pattern = PATTERN (x);
switch (GET_CODE (pattern))
{
case SET:
case PRE_DEC:
case PRE_INC:
case POST_DEC:
case POST_INC:
return GET_CODE (SET_DEST (pattern)) == MEM;
case CALL:
case RETURN:
case USE:
case CLOBBER:
return !0;
break;
case ASM_INPUT:
/* We treat assembler instructions as inherently
necessary, and we hope that its operands do not need to
be propagated. */
return !0;
break;
default:
return 0;
}
{
int inherently_necessary_set = 0;
note_stores (PATTERN (x),
note_inherently_necessary_set,
&inherently_necessary_set);
/* If we found an inherently necessary set or an asm
instruction, then we consider this insn inherently
necessary. */
return (inherently_necessary_set
|| GET_CODE (PATTERN (x)) == ASM_INPUT
|| asm_noperands (PATTERN (x)) >= 0);
}
default:
/* Found an impossible insn type. */
abort();
@ -457,6 +474,15 @@ delete_insn_bb (insn)
basic_block bb;
if (!insn)
abort ();
/* Do not actually delete anything that is not an INSN.
We can get here because we only consider INSNs as
potentially necessary. We leave it to later passes
to remove unnecessary notes, unused labels, etc. */
if (! INSN_P (insn))
return;
bb = BLOCK_FOR_INSN (insn);
if (!bb)
abort ();