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if-to-switch: Don't skip the first condition bb when find_conditions in if-to-switch [PR105740]

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The if condition is at last of first bb, so side effect statement in first BB
doesn't matter, then the first if condition could also be folded to switch
table.

gcc/ChangeLog:

	PR target/105740
	* gimple-if-to-switch.cc (find_conditions): Don't skip the first
	condition bb.

gcc/testsuite/ChangeLog:

	PR target/105740
	* gcc.dg/tree-ssa/if-to-switch-11.c: New test.

Signed-off-by: Xionghu Luo <xionghuluo@tencent.com>
This commit is contained in:
Xionghu Luo 2022-06-09 15:46:30 +08:00
parent 70454c50b4
commit 57424087e8
2 changed files with 31 additions and 1 deletions
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4
gcc/gimple-if-to-switch.cc
View file

@ -389,7 +389,9 @@ find_conditions (basic_block bb,
if (cond == NULL)
return;
if (!no_side_effect_bb (bb))
/* An empty conditions_in_bbs indicates we are processing the first
basic-block then no need check side effect. */
if (!conditions_in_bbs->is_empty () && !no_side_effect_bb (bb))
return;
tree lhs = gimple_cond_lhs (cond);

28
gcc/testsuite/gcc.dg/tree-ssa/if-to-switch-11.c Normal file
View file

@ -0,0 +1,28 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-iftoswitch-optimized" } */
struct f {
int len;
int arr[4];
};
int
test (struct f const *const f)
{
if (f->arr[3] == 1) {
return 12;
} else if (f->arr[3] == 2) {
return 27;
} else if (f->arr[3] == 3) {
return 38;
} else if (f->arr[3] == 4) {
return 18;
} else if (f->arr[3] == 5) {
return 58;
} else if (f->arr[3] == 6) {
return 68;
}
return 0;
}
/* { dg-final { scan-tree-dump "Canonical GIMPLE case clusters: 1 2 3 4 5 6" "iftoswitch" } } */