[Bug debug/104753] New: Sporadic '-fcompare-debug' failure w/ -mcpu=phecda -O2 -funroll-all-loops -fno-tree-reassoc

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104753

            Bug ID: 104753
           Summary: Sporadic '-fcompare-debug' failure w/ -mcpu=phecda -O2
                    -funroll-all-loops -fno-tree-reassoc
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: compare-debug-failure
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---
            Target: aarch64-linux-gnu

Created attachment 52544
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52544&action=edit
Testcase

gfortran 12.0.1 20220227 snapshot (g:d1574a9b820f17adb9004255e2018967e9be063b)
sporadically fails -fcompare-debug check when compiling the attached testcase
w/ -mcpu=phecda -O2 -funroll-all-loops -fno-tree-reassoc:

% for i in {1..10}; do aarch64-linux-gnu-gfortran-12.0.1 -mcpu=phecda -O2
-fcompare-debug -funroll-all-loops -fno-tree-reassoc -c l9imhim5.f; done
aarch64-linux-gnu-gfortran-12.0.1: error: l9imhim5.f: '-fcompare-debug' failure
aarch64-linux-gnu-gfortran-12.0.1: error: l9imhim5.f: '-fcompare-debug' failure
aarch64-linux-gnu-gfortran-12.0.1: error: l9imhim5.f: '-fcompare-debug' failure
aarch64-linux-gnu-gfortran-12.0.1: error: l9imhim5.f: '-fcompare-debug' failure
aarch64-linux-gnu-gfortran-12.0.1: error: l9imhim5.f: '-fcompare-debug' failure
aarch64-linux-gnu-gfortran-12.0.1: error: l9imhim5.f: '-fcompare-debug' failure
aarch64-linux-gnu-gfortran-12.0.1: error: l9imhim5.f: '-fcompare-debug' failure
aarch64-linux-gnu-gfortran-12.0.1: error: l9imhim5.f: '-fcompare-debug' failure

-fno-rename-registers "fixes" the error.