[Bug c++/66520] New: bad code generated code for branches with single &

["fkastrati at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66520

            Bug ID: 66520
           Summary: bad code generated code for branches with single &
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fkastrati at gmail dot com
  Target Milestone: ---

consider the following code snippet (c++):

void ampamp(int x, int y) {
  if (x < 3 && y > 10 ) 
    printf("%d%d", x, y);
}

void amp(int x, int y) {
  if ((x < 3) & (y > 10) ) 
    printf("%d%d", x, y);
}


the assembly code generated by g++ (all versions I tested with  optimization
flag `-O3'), is not optimal (see the link on the bottom of this message).
Basically, for both methods, the generated assembly code is identical. For the
method "amp" (with single `&') there should be generated only one jump, as
branch misprediction penalty is very high otherwise!

As a side note: the code by intel's  compiler (ICC) is however generating
optimal code for such scenarios, at least for versions icc13, and icc15 that
I've tested.

See: http://goo.gl/oiTPX5