https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91491

            Bug ID: 91491
           Summary: [9 Regression] glib2.0 build not working when built
                    with -O2 on x86_64-linux-gnu
           Product: gcc
           Version: 9.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: doko at debian dot org
  Target Milestone: ---

Created attachment 46731
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46731&action=edit
preprocessed source

[forwarded from https://bugs.debian.org/931921]

Seen with 9.2.0 on x86_64-linux-gnu, works with GCC 8, or with GCC 9 -O1.

Further tracked down to:

On Fri, 02 Aug 2019 at 19:49:20 +0100, Simon McVittie wrote:
> If you compile test_run_seed() with -O1, and the rest of gtestutils.c
> with -O2, the clutter test hangs.

Binary-searching through the extra optimizations enabled by -O2 [1]
led me to the minimal change being: if you modify test_run_seed() to add

    __attribute__((optimize("no-tree-pre")))

then the clutter test passes. Without that attribute it fails.


Attaching the preprocessed gtestutils source.

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