yroux added a comment.

In D57054#1811486 <https://reviews.llvm.org/D57054#1811486>, @samparker wrote:

> This, and the fact that LowOverheadLoops is dependent upon block sizes and 
> placement (I need to add a comment in the header on that pass....). So, 
> ConstantIslands would have to guarantee not to change branch targets or 
> change the distance between blocks around the low-overhead loop constructs. I 
> think updating liveness information would be the easier option.


I can add liveness info into the outlined function, but we will need to do the 
same on AArch64 even if is not necessary.  On the other hand isn't it the same 
for the ConstantIslands pass, I mean isn't the size of blocks modified by the 
LowOverheadLoops pass which can potentially break the accesses to some constant 
? The experiment also shows that the optmization of cmp/beq into cbz made by 
ConstantIsland place is unleashed when the LowOverheadLoops is made before.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D57054/new/

https://reviews.llvm.org/D57054



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