https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120747
Bug ID: 120747
Summary: [16 Regression] 435.gromacs miscompares since
r16-1550-g9244ea4bf55638
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pheeck at gcc dot gnu.org
CC: amacleod at redhat dot com
Blocks: 26163
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Target: x86_64-pc-linux-gnu
Running 435.gromacs SPEC CPU 2006 benchmark on a Zen4 or Zen5 machine with
-Ofast -march=native currently results in a miscompare.
0002: 3.07684e+02
3.12012e+02
^
The benchmark allows some variations but this difference is bigger than it
allows (~1.31% vs 1.25%).
I've bisected this to
9244ea4bf556381d3f7fb66154dc8944ebeb005c is the first bad commit
commit 9244ea4bf556381d3f7fb66154dc8944ebeb005c
Author: Andrew MacLeod <amacl...@redhat.com>
Date: Mon Jun 16 15:41:47 2025 -0400
Snap subrange boundries to bitmask constraints.
Ensure all subrange endpoints conform to the bitmask.
PR tree-optimization/120661
gcc/
* value-range.cc (irange::snap): New.
(irange::snap_subranges): New.
(irange::set_range_from_bitmask): Call snap_subranges.
* value-range.h (snap, snap_subranges): New prototypes.
gcc/testsuite/
* gcc.dg/pr120661-1.c: New.
* gcc.dg/pr120661-2.c: New.
gcc/testsuite/gcc.dg/pr120661-1.c | 51 ++++++++++++++++++++++
gcc/testsuite/gcc.dg/pr120661-2.c | 39 +++++++++++++++++
gcc/value-range.cc | 91 +++++++++++++++++++++++++++++++++++++++
gcc/value-range.h | 2 +
4 files changed, 183 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/pr120661-1.c
create mode 100644 gcc/testsuite/gcc.dg/pr120661-2.c
Cc-ing Andrew.
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=26163
[Bug 26163] [meta-bug] missed optimization in SPEC (2k17, 2k and 2k6 and 95)
