[PATCH] AArch64: Use CMP;CCMP sequences for and/or/setcc trees.

[James Molloy]

Hi Matthias,

This actually caused a 10% regression in one of our tests on Cortex-A57
(but a 4% improvement on Cortex-A53). I think this is to do with selects
being expensive on heavily out of order architectures. Did you notice any
regressions on Typhoon/Cyclone?

It might be useful to have a heuristic determining if this is beneficial or
not - if conversion in CGP already has this
"isPredictableSelectExpensive()" hook - perhaps a similar one might be
useful here?

Cheers,

James

On Mon, 1 Jun 2015 at 23:39 Phabricator <reviews at reviews.llvm.org> wrote:

> REPOSITORY
>   rL LLVM
>
> http://reviews.llvm.org/D8232
>
> Files:
>   llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp
>   llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.h
>   llvm/trunk/lib/Target/AArch64/AArch64InstrFormats.td
>   llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.td
>   llvm/trunk/test/CodeGen/AArch64/arm64-ccmp.ll
>
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