[PATCH] D133840: AMDGPU: Add a pass to rewrite certain undef in PHI

[Ruiling, Song via Phabricator via llvm-commits]

ruiling added inline comments.


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Comment at: llvm/lib/Target/AMDGPU/AMDGPURewriteUndefForPHI.cpp:116
+            HasBackedgeUndef = true;
+        } else if (Incoming != &PHI) {
+          if (!UniqueDefinedIncoming) {
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sameerds wrote:
> 
sounds good.


================
Comment at: llvm/lib/Target/AMDGPU/AMDGPURewriteUndefForPHI.cpp:122
+            // Update DominateBB if necessary.
+            if (DT->dominates(IncomingBB, DominateBB))
+              DominateBB = IncomingBB;
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sameerds wrote:
> If this is not true, then does DominateBB dominate IncomingBB?
No, this is used to handle case like with_uniform_region_inside added in this change. If IncomingBB does not dominate DominateBB, they may be successors of the same block in case their common predecessor has uniform branch.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D133840/new/

https://reviews.llvm.org/D133840