[Bug target/63661] New: -O2 miscompiles on OSX 10.10 Yosemite

[vbraun.name at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63661

            Bug ID: 63661
           Summary: -O2 miscompiles on OSX 10.10 Yosemite
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vbraun.name at gmail dot com

Created attachment 33821
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33821&action=edit
Testcase that yields wrong answer when compiled with -O2

The attached selfcontained test_mathieu.c is based on the GSL testsuite. I
tried to make it shorter but simple changes like adding printf tend to "fix"
it. Compilation fails on OSX 10.10 Yosemite when compiled with -O2:

$ gcc -O0 -o test_mathieu test_mathieu.c -lm && ./test_mathieu
loop -2.35802
loop 2
loop 2
loop 2
loop 2

$ gcc -O1 -o test_mathieu test_mathieu.c -lm && ./test_mathieu
loop -2.35802
loop 2
loop 2
loop 2
loop 2

$ gcc -O2 -o test_mathieu test_mathieu.c -lm && ./test_mathieu
loop -2.35802
loop 2.35802
loop 2.35802
loop 2.35802
loop 2.35802

Notes:
* The non-optimized values are the correct ones.
* Works on linux x86_64 with gcc 4.9.1 (Fedora 21 alpha)
* Works with Apple clang