[Bug target/56309] conditional moves instead of compare and branch result in almost 2x slower code

ubizjak at gmail dot com gcc-bugzilla@gcc.gnu.org
Fri Oct 18 10:06:00 GMT 2013


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56309

--- Comment #30 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Jakub Jelinek from comment #29)

> On the by-ref-O3.ii testcase there is no change, but by-val-O3.ii seems to
> be consistently faster, around 20% on AMD 8354 and 35% on Intel 2600.

According to detailed analysis in Comment 26, perhaps a new tuning flag or
target hook could be used for if-conversion of scalars. Also, I think that -Os
can still use cmoves due to smaller code size.


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