[Bug tree-optimization/58762] New: [missed optimization] Vectorizing abs(int).

[congh at google dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58762

            Bug ID: 58762
           Summary: [missed optimization] Vectorizing abs(int).
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: congh at google dot com

pabsd in SSSE3 makes it quite straightforward to vectorize abs(int) operation.
But with only SSE2 available, GCC won't vectorize this operation. GCC
translates the abs(int) operation into three instructions: sar, xor, and sub.
Each of them can be vectorized. So I am wondering why GCC does not vectorize
abs(int) in this way? Are there any platform or safety concerns?


Thank you!

Cong