[llvm] ec37ecb - [LCSSA] Skip updating users in unreachable blocks.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2022-08-26T15:09:46+01:00
New Revision: ec37ecbc6299781ebafeaa8a41413d08578577dd

URL: https://github.com/llvm/llvm-project/commit/ec37ecbc6299781ebafeaa8a41413d08578577dd
DIFF: https://github.com/llvm/llvm-project/commit/ec37ecbc6299781ebafeaa8a41413d08578577dd.diff

LOG: [LCSSA] Skip updating users in unreachable blocks.

Don't waste time trying to update users in unreachable blocks.

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/LCSSA.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Utils/LCSSA.cpp b/llvm/lib/Transforms/Utils/LCSSA.cpp
index 6de59f9eb533..020a40b229f7 100644
--- a/llvm/lib/Transforms/Utils/LCSSA.cpp
+++ b/llvm/lib/Transforms/Utils/LCSSA.cpp
@@ -111,6 +111,10 @@ bool llvm::formLCSSAForInstructions(SmallVectorImpl<Instruction *> &Worklist,
       Instruction *User = cast<Instruction>(U.getUser());
       BasicBlock *UserBB = User->getParent();
 
+      // Skip uses in unreachable blocks.
+      if (!DT.isReachableFromEntry(UserBB))
+        continue;
+
       // For practical purposes, we consider that the use in a PHI
       // occurs in the respective predecessor block. For more info,
       // see the `phi` doc in LangRef and the LCSSA doc.