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VN: Lookup val != 0 if we got back val when looking up the predicate for GIMPLE_COND [PR117414]

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Sometimes we get back a full ssa name when looking up the comparison of the GIMPLE_COND
rather than a predicate. We then want to lookup the `val != 0` for the predicate.

Note this might happen with other boolean assignments and COND_EXPR but I am not sure
if it is as important; I have not found a testcase yet.

Bootstrapped and tested on x86_64-linux-gnu.

	PR tree-optimization/117414

gcc/ChangeLog:

	* tree-ssa-sccvn.cc (process_bb): Lookup
	`val != 0` if got back a ssa name when looking the comparison.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/fre-predicated-4.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
This commit is contained in:
Andrew Pinski 2024-11-01 23:20:22 -07:00
parent add4bb9445
commit 684e5ae90b
2 changed files with 48 additions and 0 deletions
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38
gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-4.c Normal file
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@ -0,0 +1,38 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
/* PR tree-optimization/117414 */
/* Fre1 should figure out that `*aaa != 0`
For f0 and f1. */
void foo();
int f0(int *aaa, int j, int t)
{
int b = *aaa;
if (b == 0 || t == 1)
return 0;
for(int i = 0; i < j; i++)
{
if (!*aaa) foo();
}
return 0;
}
int f1(int *aaa, int j, int t)
{
int b = *aaa;
if (b == 0)
return 0;
if (t == 1)
return 0;
for(int i = 0; i < j; i++)
{
if (!*aaa) foo();
}
return 0;
}
/* { dg-final { scan-tree-dump-not "foo " "optimized" } } */
/* { dg-final { scan-tree-dump "return 0;" "optimized" } } */

10
gcc/tree-ssa-sccvn.cc
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@ -8159,6 +8159,16 @@ process_bb (rpo_elim &avail, basic_block bb,
val = vn_nary_op_lookup_pieces (2, gimple_cond_code (last),
boolean_type_node, ops,
&vnresult);
/* Got back a ssa name, then try looking up `val != 0`
as it might have been recorded that way. */
if (val && TREE_CODE (val) == SSA_NAME)
{
ops[0] = val;
ops[1] = build_zero_cst (TREE_TYPE (val));
val = vn_nary_op_lookup_pieces (2, NE_EXPR,
boolean_type_node, ops,
&vnresult);
}
/* Did we get a predicated value? */
if (! val && vnresult && vnresult->predicated_values)
{