[Bug tree-optimization/91491] [9 Regression] glib2.0 build not working when built with -O2 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

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

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2019-08-20
   Target Milestone|---                         |9.3
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
The testcase needs -std=gnu89 to work.

If you compile test_run_seed() with -O1 PRE is already disabled, so you
mean that if you compile the file with -O2 but disable PRE on just
test_run_seed() the testcase works?  But Simon says it's broken when
compilng test_run_seed with -O1 ...

What is true?

There's also a debug counter treepre_insert you could use to further
track down which PRE transform is guilty.  Also try -fno-tree-tail-merge.

The only loop I see in test_run_seed is

  while (strchr (" \t\v\r\n\f", *rseed))
    rseed++;

so where does it actually hang?