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pointer" (r204174)
> For functions where esi is used as base pointer, we would previously fall ba
> from lowering memcpy with "rep movs" because that clobbers esi.
>
> With this patch, we just store esi in another physical register, and restore
> it afterwards. This adds a little bit of register preassure, but the more
> efficient memcpy should be worth it.
>
> Differential Revision: http://llvm-reviews.chandlerc.com/D2968
This didn't work. I was ending up with code like this:
lea edi,[esi+38h]
mov ecx,0Fh
mov edx,esi
mov esi,ebx
rep movs dword ptr es:[edi],dword ptr [esi]
lea ecx,[esi+74h] <-- Ooops, we're now using esi before restoring it from edx.
add ebx,3Ch
mov esi,edx
I guess if we want to do this we need stronger glue or something, or doing the expansion
much later.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204829 91177308-0d34-0410-b5e6-96231b3b80d8
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For functions where esi is used as base pointer, we would previously fall back
from lowering memcpy with "rep movs" because that clobbers esi.
With this patch, we just store esi in another physical register, and restore
it afterwards. This adds a little bit of register preassure, but the more
efficient memcpy should be worth it.
Differential Revision: http://llvm-reviews.chandlerc.com/D2968
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204174 91177308-0d34-0410-b5e6-96231b3b80d8
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