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re PR tree-optimization/85757 (tree optimizers fail to fully clean up fixed-size memcpy)

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2018-05-17  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/85757
	* tree-ssa-dse.c (dse_classify_store): Record a PHI def and
	remove defs that only feed that PHI from further processing.

	* gcc.dg/tree-ssa/ssa-dse-34.c: New testcase.

From-SVN: r260306
This commit is contained in:
Richard Biener 2018-05-17 06:57:45 +00:00 committed by Richard Biener
parent 8ee520219f
commit 773d0331f7
4 changed files with 54 additions and 8 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2018-05-17 Richard Biener <rguenther@suse.de>
PR tree-optimization/85757
* tree-ssa-dse.c (dse_classify_store): Record a PHI def and
remove defs that only feed that PHI from further processing.
2018-05-16 Jim Wilson <jimw@sifive.com>
* config/riscv/riscv.md (<optab>si3_mask, <optab>si3_mask_1): Prepend

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2018-05-17 Richard Biener <rguenther@suse.de>
PR tree-optimization/85757
* gcc.dg/tree-ssa/ssa-dse-34.c: New testcase.
2018-05-16 Marek Polacek <polacek@redhat.com>
PR c++/85363

15
gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-34.c Normal file
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@ -0,0 +1,15 @@
/* { dg-do compile } */
/* { dg-options "-O -fdump-tree-dse1-details" } */
void f(int n, char *p0, char *p1, char *p2, char *o)
{
int t0, t1;
__builtin_memcpy(&t0, p0, 1);
__builtin_memcpy(&t1, p1, 1);
if (n==3)
__builtin_memcpy(o+2, p2, 1);
__builtin_memcpy(o+0, &t0, 1);
__builtin_memcpy(o+1, &t1, 1);
}
/* { dg-final { scan-tree-dump-times "Deleted dead store" 2 "dse1" } } */

36
gcc/tree-ssa-dse.c
View File

@ -577,6 +577,7 @@ dse_classify_store (ao_ref *ref, gimple *stmt,
else
defvar = gimple_vdef (temp);
auto_vec<gimple *, 10> defs;
gimple *phi_def = NULL;
FOR_EACH_IMM_USE_STMT (use_stmt, ui, defvar)
{
/* Limit stmt walking. */
@ -600,7 +601,10 @@ dse_classify_store (ao_ref *ref, gimple *stmt,
processing. */
if (!bitmap_bit_p (visited,
SSA_NAME_VERSION (PHI_RESULT (use_stmt))))
defs.safe_push (use_stmt);
{
defs.safe_push (use_stmt);
phi_def = use_stmt;
}
}
/* If the statement is a use the store is not dead. */
else if (ref_maybe_used_by_stmt_p (use_stmt, ref))
@ -657,15 +661,31 @@ dse_classify_store (ao_ref *ref, gimple *stmt,
return DSE_STORE_DEAD;
}
/* Process defs and remove paths starting with a kill from further
processing. */
/* Process defs and remove those we need not process further. */
for (unsigned i = 0; i < defs.length (); ++i)
if (stmt_kills_ref_p (defs[i], ref))
{
if (by_clobber_p && !gimple_clobber_p (defs[i]))
*by_clobber_p = false;
{
gimple *def = defs[i];
gimple *use_stmt;
use_operand_p use_p;
/* If the path to check starts with a kill we do not need to
process it further.
??? With byte tracking we need only kill the bytes currently
live. */
if (stmt_kills_ref_p (def, ref))
{
if (by_clobber_p && !gimple_clobber_p (def))
*by_clobber_p = false;
defs.unordered_remove (i);
}
/* In addition to kills we can remove defs whose only use
is another def in defs. That can only ever be PHIs of which
we track a single for simplicity reasons (we fail for multiple
PHIs anyways). */
else if (gimple_code (def) != GIMPLE_PHI
&& single_imm_use (gimple_vdef (def), &use_p, &use_stmt)
&& use_stmt == phi_def)
defs.unordered_remove (i);
}
}
/* If all defs kill the ref we are done. */
if (defs.is_empty ())