[LLVMdev] [Shrink-Wrapping] Request For Benchmarking: X86 and AArch64

[Chandler Carruth]

I've run it across a wide variety of server benchmarks we care about. Looks
like all the changes are in the noise across sandybridge and ivybridge
architectures.

No interesting performance changes (in either direction sadly).

I saw some very minor size fluctuations and dug into it. Turns out there
was a missed easy size optimization in it that Quentin has already
implemented based on our conversation on IRC.

As far as I can see, this is pure goodness. Let's turn it on.

On Wed, May 27, 2015 at 3:17 PM Quentin Colombet <qcolombet at apple.com>
wrote:

> Hi,
>
> Shrink-wrapping capabilities, i.e., better placement of prologue and
> epilogue sequences, landed in r236507 but are not yet enabled by default.
>
> Since r236507 AArch64 is shrink-wrapping ready, meaning we can turn the
> pass on for this target.
> I’ve done the same for X86 in r 238293.
>
> Now, I need your help to test and benchmark how shrink-wrapping perform on
> those targets.
>
> The goal is to decide whether or not the support is good enough to be
> enabled by default.
>
>
> ** How Can I Test/Benchmark It? **
>
> Add (-mllvm) -enable-shrink-wrap on your command line or patch the
> XXXConfigPass to set EnableShrinkWrap to true.
> Note the -enable-shrink-wrap=<bool> takes precedence over whatever is set
> for EnableShrinkWrap.
>
> Please report any problem specific to this optimization turned on. A PR
> with a small IR to reproduce are appreciated.
>
> Note: I’ve seem up to 4% runtime improvements on the LLVM test-suite +
> specs for Os and O3.
>
>
> Thanks in advance for your help,
> -Quentin
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