[PATCH] Avoid generating SHLD/SHRD for architectures that are known to have poor latency for these instructions.

[Nadav Rotem]

Katya, 

>From your earlier description it sounds like neither Intel nor AMD processors benefit from this transformation.  Why don’t we enable it only for Oz? What is the point of adding FeatureSlowSHLD?

Thanks,
Nadav 
 

On Nov 17, 2013, at 11:37 PM, Katya Romanova <Katya_Romanova at playstation.sony.com> wrote:

>  Made the corrections based on Eric's comments.
> 
> http://llvm-reviews.chandlerc.com/D2177
> 
> CHANGE SINCE LAST DIFF
>  http://llvm-reviews.chandlerc.com/D2177?vs=5537&id=5620#toc
> 
> Files:
>  test/CodeGen/X86/x86-64-double-shifts-var.ll
>  test/CodeGen/X86/x86-64-double-precision-shift-left.ll
>  test/CodeGen/X86/x86-64-double-precision-shift-right.ll
>  test/CodeGen/X86/x86-64-double-shifts-Oz-Os-O2.ll
>  lib/Target/X86/X86ISelLowering.cpp
>  lib/Target/X86/X86.td
>  lib/Target/X86/X86Subtarget.cpp
>  lib/Target/X86/X86Subtarget.h
> <D2177.2.patch>