[PATCH] D17573: [X86] PR26554: Use not all set of alternative nops in 64 bit mode, but only those which are correct

[Andrey Turetskiy via llvm-commits]

aturetsk added a comment.

I modified the patch as Simon suggested: AsmBackend now gets Triple and CPU from MCSubtargetInfo.
Note that the CPU from MCSubtargetInfo is a bit different from the CPU we used to pass as argument: if -mcpu isn't specified the CPU used to be "", but now it's "generic". I think that this is actually how it should be, however the change in behavior required to fix a couple of tests by specifying -mcpu option (the tests were expecting long nop generation but "generic" doesn't support them).

I'm planning to split this change-set into five commits into LLVM:

1. Use MCSubtargetInfo argument instead of CPU and Triple in create*AsmBackend functions
2. Replace CPU argument with MCSubtargetInfo in all AsmBackend classes in X86AsmBackend.cpp
3. Introduction of FeatureLongNop
4. Introduction of FeatureFastNop7
5. Fix for alternative long nop generation for x86-64

Also there is a small patch to be committed in clang: http://reviews.llvm.org/D21066


http://reviews.llvm.org/D17573