On Oct 26, 2010, at 7:30 AM, "[email protected]" <[email protected]
> wrote:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46186
--- Comment #1 from Julian Andres Klode <[email protected]>
2010-10-26 14:30:24 UTC ---
Created attachment 22162
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22162
Clang's assember
This multiplication transformation is incorrect if the loop wraps
(unsigned always wraps; never overflows). Gcc is correct in its speed.
Though -O3 is faster but not because of multiplication but rather
constant propatagtion. So this bug is invalid and some one should
report a bug to llvm folks about this.
Attaching the assembler output from clang, it should help understand
which
optimizations clang does (and improve gcc to do them as well).
