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* [gcc r14-6210] i386: Move vzeroupper pass from after reload pass to after postreload_cse [PR112760]
@ 2023-12-06 8:59 Jakub Jelinek
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From: Jakub Jelinek @ 2023-12-06 8:59 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:e44ed92dbbe9d4e5c23f486cd2f77a6f9ee513c5
commit r14-6210-ge44ed92dbbe9d4e5c23f486cd2f77a6f9ee513c5
Author: Jakub Jelinek <jakub@redhat.com>
Date: Wed Dec 6 09:59:12 2023 +0100
i386: Move vzeroupper pass from after reload pass to after postreload_cse [PR112760]
Regardless of the outcome of the REG_UNUSED discussions, I think
it is a good idea to move the vzeroupper pass one pass later.
As can be seen in the multiple PRs and as postreload.cc documents,
reload/LRA is known to create dead statements quite often, which
is the reason why we have postreload_cse pass at all.
Doing vzeroupper pass before such cleanup means the pass including
df_analyze for it needs to process more instructions than needed
and because mode switching adds note problem, also higher chance of
having stale REG_UNUSED notes.
And, I really don't see why vzeroupper can't wait until those cleanups
are done.
2023-12-06 Jakub Jelinek <jakub@redhat.com>
PR rtl-optimization/112760
* config/i386/i386-passes.def (pass_insert_vzeroupper): Insert
after pass_postreload_cse rather than pass_reload.
* config/i386/i386-features.cc (rest_of_handle_insert_vzeroupper):
Adjust comment for it.
* gcc.dg/pr112760.c: New test.
Diff:
---
gcc/config/i386/i386-features.cc | 9 +++++----
gcc/config/i386/i386-passes.def | 2 +-
gcc/testsuite/gcc.dg/pr112760.c | 22 ++++++++++++++++++++++
3 files changed, 28 insertions(+), 5 deletions(-)
diff --git a/gcc/config/i386/i386-features.cc b/gcc/config/i386/i386-features.cc
index 6fac67e9a28..e6fc135f32f 100644
--- a/gcc/config/i386/i386-features.cc
+++ b/gcc/config/i386/i386-features.cc
@@ -2627,10 +2627,11 @@ convert_scalars_to_vector (bool timode_p)
static unsigned int
rest_of_handle_insert_vzeroupper (void)
{
- /* vzeroupper instructions are inserted immediately after reload to
- account for possible spills from 256bit or 512bit registers. The pass
- reuses mode switching infrastructure by re-running mode insertion
- pass, so disable entities that have already been processed. */
+ /* vzeroupper instructions are inserted immediately after reload and
+ postreload_cse to clean up after it a little bit to account for possible
+ spills from 256bit or 512bit registers. The pass reuses mode switching
+ infrastructure by re-running mode insertion pass, so disable entities
+ that have already been processed. */
for (int i = 0; i < MAX_386_ENTITIES; i++)
ix86_optimize_mode_switching[i] = 0;
diff --git a/gcc/config/i386/i386-passes.def b/gcc/config/i386/i386-passes.def
index 90f2234eb00..2d189810ec4 100644
--- a/gcc/config/i386/i386-passes.def
+++ b/gcc/config/i386/i386-passes.def
@@ -24,7 +24,7 @@ along with GCC; see the file COPYING3. If not see
REPLACE_PASS (PASS, INSTANCE, TGT_PASS)
*/
- INSERT_PASS_AFTER (pass_reload, 1, pass_insert_vzeroupper);
+ INSERT_PASS_AFTER (pass_postreload_cse, 1, pass_insert_vzeroupper);
INSERT_PASS_AFTER (pass_combine, 1, pass_stv, false /* timode_p */);
/* Run the 64-bit STV pass before the CSE pass so that CONST0_RTX and
CONSTM1_RTX generated by the STV pass can be CSEed. */
diff --git a/gcc/testsuite/gcc.dg/pr112760.c b/gcc/testsuite/gcc.dg/pr112760.c
new file mode 100644
index 00000000000..b4ec70e4701
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr112760.c
@@ -0,0 +1,22 @@
+/* PR rtl-optimization/112760 */
+/* { dg-do run } */
+/* { dg-options "-O2 -fno-dce -fno-guess-branch-probability --param=max-cse-insns=0" } */
+/* { dg-additional-options "-m8bit-idiv -mavx" { target i?86-*-* x86_64-*-* } } */
+
+unsigned g;
+
+__attribute__((__noipa__)) unsigned short
+foo (unsigned short a, unsigned short b)
+{
+ unsigned short x = __builtin_add_overflow_p (a, g, (unsigned short) 0);
+ g -= g / b;
+ return x;
+}
+
+int
+main ()
+{
+ unsigned short x = foo (40, 6);
+ if (x != 0)
+ __builtin_abort ();
+}
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2023-12-06 8:59 [gcc r14-6210] i386: Move vzeroupper pass from after reload pass to after postreload_cse [PR112760] Jakub Jelinek
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