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* [gcc r12-1115] tree-optimization/100778 - avoid cross-BB vectorization of trapping op
@ 2021-05-28 13:18 Richard Biener
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From: Richard Biener @ 2021-05-28 13:18 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:f7a07f5a5d8065e7f11133dd1f4ad3510ab2195b
commit r12-1115-gf7a07f5a5d8065e7f11133dd1f4ad3510ab2195b
Author: Richard Biener <rguenther@suse.de>
Date: Fri May 28 14:26:06 2021 +0200
tree-optimization/100778 - avoid cross-BB vectorization of trapping op
This avoids vectorizing a possibly trapping operation when lanes
are handled in different BBs. I spotted this when working on the
originally reported issue in PR100778.
2021-05-28 Richard Biener <rguenther@suse.de>
PR tree-optimization/100778
* tree-vect-slp.c (vect_build_slp_tree_1): Prevent possibly
trapping ops in different BBs.
* gcc.dg/vect/bb-slp-pr100778-1.c: New testcase.
Diff:
---
gcc/testsuite/gcc.dg/vect/bb-slp-pr100778-1.c | 18 ++++++++++++++++++
gcc/tree-vect-slp.c | 4 ++--
2 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/gcc/testsuite/gcc.dg/vect/bb-slp-pr100778-1.c b/gcc/testsuite/gcc.dg/vect/bb-slp-pr100778-1.c
new file mode 100644
index 00000000000..9f8b7eecef1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/bb-slp-pr100778-1.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target vect_double } */
+
+double foo (int x, double *p)
+{
+ double res = p[0] + p[1];
+ double tem = p[0] / x;
+ if (x)
+ {
+ p[0] = tem;
+ p[1] /= x;
+ }
+ return res + tem;
+}
+
+/* We may not SLP vectorize the FP division because it can trap and it
+ is distributed between two basic-blocks. */
+/* { dg-final { scan-tree-dump "Build SLP failed: different BB for PHI or possibly trapping operation in _\[0-9\]+ = _\[0-9\]+ / _\[0-9\]+;" "slp2" } } */
diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index 0ec92b0f0ca..ca1539e63f2 100644
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -1214,14 +1214,14 @@ vect_build_slp_tree_1 (vec_info *vinfo, unsigned char *swap,
}
}
- if (phi_p
+ if ((phi_p || gimple_could_trap_p (stmt_info->stmt))
&& (gimple_bb (first_stmt_info->stmt)
!= gimple_bb (stmt_info->stmt)))
{
if (dump_enabled_p ())
dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
"Build SLP failed: different BB for PHI "
- "in %G", stmt);
+ "or possibly trapping operation in %G", stmt);
/* Mismatch. */
continue;
}
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