https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116185
Bug ID: 116185
Summary: [15 Regression] Comparison failure on sh4 due to debug
symbols
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: law at gcc dot gnu.org
Target Milestone: ---
Created attachment 58800
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58800&action=edit
Testcase
This patch causes a bootstrap comparison failure on sh4-linux-gnu:
commit 9f9faebb8ebfc0103461641cc49ba0b21877b2b1 (HEAD)
Author: Richard Sandiford <richard.sandif...@arm.com>
Date: Tue Jul 16 15:31:17 2024 +0100
rtl-ssa: Enforce earlyclobbers on hard-coded clobbers [PR115891]
The asm in the testcase has a memory operand and also clobbers ax.
The clobber means that ax cannot be used to hold inputs, which
extends to the address of the memory.
[ ... ]
The failure shows up as several instructions being interchanged in the final
output depending -g of ira-emit.c. So I first narrowed that down to a
"reasonable" testcase, eyeballing the assembly code changes, then narrowed it
again using -fcompare-debug with a cross compiler. Then verified that the
compare-debug failure goes away when the patch above is reverted.
So while there is some chance the reduction process has morphed the bug, it
seems unlikely as it still fails with the above patch and passes without the
above patch.
Compile with -O2 -fno-exceptions -fno-rtti -fcompare-debug -c with an
sh4-linux-gnu cross compiler. You'll also need a cross-assembler for the
compare-debug step, but you don't need a linker or any libraries.
