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* [gcc r11-10354] ifcvt: Don't introduce trapping or faulting reads in noce_try_sign_mask [PR106032]
@ 2022-11-04 8:30 Jakub Jelinek
0 siblings, 0 replies; only message in thread
From: Jakub Jelinek @ 2022-11-04 8:30 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:fe6e8a09a5338c0acda23ab2d3ef4433fb83637f
commit r11-10354-gfe6e8a09a5338c0acda23ab2d3ef4433fb83637f
Author: Jakub Jelinek <jakub@redhat.com>
Date: Tue Jun 21 11:40:16 2022 +0200
ifcvt: Don't introduce trapping or faulting reads in noce_try_sign_mask [PR106032]
noce_try_sign_mask as documented will optimize
if (c < 0)
x = t;
else
x = 0;
into x = (c >> bitsm1) & t;
The optimization is done if either t is unconditional
(e.g. for
x = t;
if (c >= 0)
x = 0;
) or if it is cheap. We already check that t doesn't have side-effects,
but if t is conditional, we need to punt also if it may trap or fault,
as we make it unconditional.
I've briefly skimmed other noce_try* optimizations and didn't find one that
would suffer from the same problem.
2022-06-21 Jakub Jelinek <jakub@redhat.com>
PR rtl-optimization/106032
* ifcvt.c (noce_try_sign_mask): Punt if !t_unconditional, and
t may_trap_or_fault_p, even if it is cheap.
* gcc.c-torture/execute/pr106032.c: New test.
(cherry picked from commit a0c30fe3b888f20215f3e040d21b62b603804ca9)
Diff:
---
gcc/ifcvt.c | 15 ++++++++-------
gcc/testsuite/gcc.c-torture/execute/pr106032.c | 21 +++++++++++++++++++++
2 files changed, 29 insertions(+), 7 deletions(-)
diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index 0439a8aacff..367d5c25c56 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -2814,18 +2814,19 @@ noce_try_sign_mask (struct noce_if_info *if_info)
return FALSE;
/* This is only profitable if T is unconditionally executed/evaluated in the
- original insn sequence or T is cheap. The former happens if B is the
- non-zero (T) value and if INSN_B was taken from TEST_BB, or there was no
- INSN_B which can happen for e.g. conditional stores to memory. For the
- cost computation use the block TEST_BB where the evaluation will end up
- after the transformation. */
+ original insn sequence or T is cheap and can't trap or fault. The former
+ happens if B is the non-zero (T) value and if INSN_B was taken from
+ TEST_BB, or there was no INSN_B which can happen for e.g. conditional
+ stores to memory. For the cost computation use the block TEST_BB where
+ the evaluation will end up after the transformation. */
t_unconditional
= (t == if_info->b
&& (if_info->insn_b == NULL_RTX
|| BLOCK_FOR_INSN (if_info->insn_b) == if_info->test_bb));
if (!(t_unconditional
- || (set_src_cost (t, mode, if_info->speed_p)
- < COSTS_N_INSNS (2))))
+ || ((set_src_cost (t, mode, if_info->speed_p)
+ < COSTS_N_INSNS (2))
+ && !may_trap_or_fault_p (t))))
return FALSE;
if (!noce_can_force_operand (t))
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr106032.c b/gcc/testsuite/gcc.c-torture/execute/pr106032.c
new file mode 100644
index 00000000000..d2ccf6a5b52
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr106032.c
@@ -0,0 +1,21 @@
+/* PR rtl-optimization/106032 */
+
+__attribute__((noipa)) int
+foo (int x, int *y)
+{
+ int a = 0;
+ if (x < 0)
+ a = *y;
+ return a;
+}
+
+int
+main ()
+{
+ int a = 42;
+ if (foo (0, 0) != 0 || foo (1, 0) != 0)
+ __builtin_abort ();
+ if (foo (-1, &a) != 42 || foo (-42, &a) != 42)
+ __builtin_abort ();
+ return 0;
+}
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