[llvm] r204076 - Use range metadata instead of introducing selects.

Dan Gohman dan433584 at gmail.com
Tue Mar 25 10:50:18 PDT 2014

On Tue, Mar 25, 2014 at 7:24 AM, Rafael EspĂ­ndola <
rafael.espindola at gmail.com> wrote:

> On 25 March 2014 09:49, Dan Gohman <dan433584 at gmail.com> wrote:
> > Hi Lang,
> >
> > I can reproduce the performance regression on fourinarow, at least. With
> the
> > patch, the code size and static instruction count of the benchmark's one
> > embarassingly-hot function is lower, the dynamic instruction count is
> lower,
> > and the stack frame is smaller, but it still runs slower. Instruction
> > selection is basically the same, except that there are fewer cmovs. There
> > appears to be a minor difference in instruction scheduling in the hot
> > function. The regression disappeared when I experimented with non-default
> > values for -pre-RA-sched. However, I'm not prepared for the adventure of
> > changing the instruction scheduler's heuristics at this time, so I'll
> just
> > let this patch go for now.
> Do you have a small .ll testcase?

Not handy anymore, but it's just MultiSource/Benchmarks/
FreeBench/fourinarow/fourinarow with -O3 -flto on x86-64.

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