https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123111
Bug ID: 123111
Summary: [16 Regression] gcc.target/sh/pr51244-9.c fails after
recent change
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: law at gcc dot gnu.org
Target Milestone: ---
sh3-linux-gnu regresses on pr51244-9.c after this change:
fae0c626250563c1619cc10c6af18a0c4cae5a97 is the first bad commit
commit fae0c626250563c1619cc10c6af18a0c4cae5a97 (HEAD)
Author: Andrew Pinski <[email protected]>
Date: Sat Dec 6 01:11:29 2025 -0800
final_cleanup: Call make_forwarders_with_degenerate_phis [PR46555]
This fixes a regression introduced with r16-5258-g1d8e2d51e5c5cb.
With GCC 12+, we would not merge forwarders (with phis, vops included),
this meant that after the last cddce, degenerate phis would stay not
merged which allowed for better expansion. Now after my patch, the
forwarder
block would be removed and get worse expansion. This fixes the problem
by creating the forwarder blocks in "optimized" and no other cleanupcfg
is called afterwards.
Oh this also fixes the problem at -O1 which was missed because the
agressive
version of dce was not done at -O1.
Bootstrapped and tested on x86_64-linux-gnu.
PR tree-optimization/46555
gcc/ChangeLog:
* tree-cfgcleanup.cc (execute_cleanup_cfg_post_optimizing):
Don't set todo to include cleanupcfg; do it manually.
Call make_forwarders_with_degenerate_phis if optimizing.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/pr46555.c: New test.
Signed-off-by: Andrew Pinski <[email protected]>
It's a scan-asm test, so you don't need a full toolchain.
>From looking at the testcase it's pretty clearly in my mind a regression. We
failed to convert a comparison where one argument was 0 into a tst insn. I'm
inclined to believe this is a target specific issue. Assuming further
investigation shows that to be true, then I'd fully support pushing to P4 given
it'd be an SH specific problem at that point.
