[llvm] r308986 - [X86][CGP] Reduce memcmp() expansion to 2 load pairs (PR33914)

[Hans Wennborg via llvm-commits]

Merged together with r308963 in r309127.

On Tue, Jul 25, 2017 at 10:04 AM, Simon Pilgrim via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: rksimon
> Date: Tue Jul 25 10:04:37 2017
> New Revision: 308986
>
> URL: http://llvm.org/viewvc/llvm-project?rev=308986&view=rev
> Log:
> [X86][CGP] Reduce memcmp() expansion to 2 load pairs (PR33914)
>
> D35067/rL308322 attempted to support up to 4 load pairs for memcmp inlining which resulted in regressions for some optimized libc memcmp implementations (PR33914).
>
> Until we can match these more optimal cases, this patch reduces the memcmp expansion to a maximum of 2 load pairs (which matches what we do for -Os).
>
> This patch should be considered for the 5.0.0 release branch as well
>
> Differential Revision: https://reviews.llvm.org/D35830
>
> Modified:
>     llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
>     llvm/trunk/test/CodeGen/X86/memcmp.ll
>     llvm/trunk/test/Transforms/CodeGenPrepare/X86/memcmp.ll