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PHIOPT: Don't transform minmax if middle bb contains a phi [PR115143]

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The problem here is even if last_and_only_stmt returns a statement,
the bb might still contain a phi node which defines a ssa name
which is used in that statement so we need to add a check to make sure
that the phi nodes are empty for the middle bbs in both the
`CMP?MINMAX:MINMAX` case and the `CMP?MINMAX:B` cases.

Bootstrapped and tested on x86_64_linux-gnu with no regressions.

	PR tree-optimization/115143

gcc/ChangeLog:

	* tree-ssa-phiopt.cc (minmax_replacement): Check for empty
	phi nodes for middle bbs for the case where middle bb is not empty.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/compile/pr115143-1.c: New test.
	* gcc.c-torture/compile/pr115143-2.c: New test.
	* gcc.c-torture/compile/pr115143-3.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
(cherry picked from commit 9ff8f041331ef8b56007fb3c4d41d76f9850010d)
This commit is contained in:
Andrew Pinski 2024-05-18 11:55:58 -07:00
parent a983793420
commit 89ab128656
4 changed files with 92 additions and 0 deletions
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21
gcc/testsuite/gcc.c-torture/compile/pr115143-1.c Normal file
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@ -0,0 +1,21 @@
/* PR tree-optimization/115143 */
/* This used to ICE.
minmax part of phiopt would transform,
would transform `a!=0?min(a, b) : 0` into `min(a,b)`
which was correct except b was defined by a phi in the inner
bb which was not handled. */
short a, d;
char b;
long c;
unsigned long e, f;
void g(unsigned long h) {
if (c ? e : b)
if (e)
if (d) {
a = f ? ({
unsigned long i = d ? f : 0, j = e ? h : 0;
i < j ? i : j;
}) : 0;
}
}

30
gcc/testsuite/gcc.c-torture/compile/pr115143-2.c Normal file
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@ -0,0 +1,30 @@
/* { dg-options "-fgimple" } */
/* PR tree-optimization/115143 */
/* This used to ICE.
minmax part of phiopt would transform,
would transform `a!=0?min(a, b) : 0` into `min(a,b)`
which was correct except b was defined by a phi in the inner
bb which was not handled. */
unsigned __GIMPLE (ssa,startwith("phiopt"))
foo (unsigned a, unsigned b)
{
unsigned j;
unsigned _23;
unsigned _12;
__BB(2):
if (a_6(D) != 0u)
goto __BB3;
else
goto __BB4;
__BB(3):
j_10 = __PHI (__BB2: b_11(D));
_23 = __MIN (a_6(D), j_10);
goto __BB4;
__BB(4):
_12 = __PHI (__BB3: _23, __BB2: 0u);
return _12;
}

29
gcc/testsuite/gcc.c-torture/compile/pr115143-3.c Normal file
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@ -0,0 +1,29 @@
/* { dg-options "-fgimple" } */
/* PR tree-optimization/115143 */
/* This used to ICE.
minmax part of phiopt would transform,
would transform `a!=0?min(a, b) : 0` into `min(a,b)`
which was correct except b was defined by a phi in the inner
bb which was not handled. */
unsigned __GIMPLE (ssa,startwith("phiopt"))
foo (unsigned a, unsigned b)
{
unsigned j;
unsigned _23;
unsigned _12;
__BB(2):
if (a_6(D) > 0u)
goto __BB3;
else
goto __BB4;
__BB(3):
j_10 = __PHI (__BB2: b_7(D));
_23 = __MIN (a_6(D), j_10);
goto __BB4;
__BB(4):
_12 = __PHI (__BB3: _23, __BB2: 0u);
return _12;
}

12
gcc/tree-ssa-phiopt.cc
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@ -1918,6 +1918,10 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb, basic_block alt_
|| gimple_code (assign) != GIMPLE_ASSIGN)
return false;
/* There cannot be any phi nodes in the middle bb. */
if (!gimple_seq_empty_p (phi_nodes (middle_bb)))
return false;
lhs = gimple_assign_lhs (assign);
ass_code = gimple_assign_rhs_code (assign);
if (ass_code != MAX_EXPR && ass_code != MIN_EXPR)
@ -1931,6 +1935,10 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb, basic_block alt_
|| gimple_code (assign) != GIMPLE_ASSIGN)
return false;
/* There cannot be any phi nodes in the alt middle bb. */
if (!gimple_seq_empty_p (phi_nodes (alt_middle_bb)))
return false;
alt_lhs = gimple_assign_lhs (assign);
if (ass_code != gimple_assign_rhs_code (assign))
return false;
@ -2042,6 +2050,10 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb, basic_block alt_
|| gimple_code (assign) != GIMPLE_ASSIGN)
return false;
/* There cannot be any phi nodes in the middle bb. */
if (!gimple_seq_empty_p (phi_nodes (middle_bb)))
return false;
lhs = gimple_assign_lhs (assign);
ass_code = gimple_assign_rhs_code (assign);
if (ass_code != MAX_EXPR && ass_code != MIN_EXPR)