[Bug tree-optimization/37868] New: code that doesn't breaks TBAA is misoptimized even with -fno-strict-aliasing

["edwintorok at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

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+++ This bug was initially created as a clone of Bug #37867 +++

Cloning bug on Chris's request.

Running gcc-4.3 -O2 on PR1386.c I get different results than with -O1.

$ gcc-4.3 -O1 PR1386.c && ./a.out
PR1386.c: In function ‘main’:
PR1386.c:15: warning: large integer implicitly truncated to unsigned type
PR1386.c:17: warning: large integer implicitly truncated to unsigned type
bad bits: 0

$ gcc-4.3 -O2 PR1386.c && ./a.out
PR1386.c: In function ‘main’:
PR1386.c:15: warning: large integer implicitly truncated to unsigned type
PR1386.c:17: warning: large integer implicitly truncated to unsigned type
bad bits: fffffffffffffff0

$ g++-4.3 -O2 -fno-strict-aliasing x.c
x.c: In function ‘int main()’:
x.c:15: warning: large integer implicitly truncated to unsigned type
x.c:17: warning: large integer implicitly truncated to unsigned type
edwin@debian:~$ ./a.out
bad bits: fffffffffffffff0


-- 
           Summary: code that doesn't breaks TBAA is misoptimized even with
                    -fno-strict-aliasing
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: edwintorok at gmail dot com
 GCC build triplet: x86_64-linux-gnu
  GCC host triplet: x86_64-linux-gnu
GCC target triplet: x86_64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37868