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
