[PATCH] D117796: AMDGPU: Fix LiveVariables error after lowering SI_END_CF

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


================
Comment at: llvm/lib/Target/AMDGPU/SILowerControlFlow.cpp:531
+        if (VI.AliveBlocks.test(MBB.getNumber()))
+          VI.AliveBlocks.set(SplitBB->getNumber());
+        else {
----------------
ruiling wrote:
> arsenm wrote:
> > ruiling wrote:
> > > Is it possible that a value defined in MBB (and kept in MBB after split) and killed in successor block, now becomes alive in SplitBB?
> > That's covered by updating the Killed set, replaceKillInstruction
> It is something like below after split:
> ```
> MBB:
>   %a = PHI ... // this will be lowered into COPY after phi-elim
>  ...
> SplitBB:
>   ...
> Succ:
>   use(%a)
> ```
> 
> %a is not the source of SI_END_CF, here we need to insert SplitBB into AliveBlocks of %a.
> 
The lowered SI_END_CF is not inserted at its original position in the block. It is moved to the top of the block, moving it before the phis which were lowered


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  https://reviews.llvm.org/D117796/new/

https://reviews.llvm.org/D117796