[PATCH] D157263: [NewGVN] Unreachable if block in performSymbolicLoadEvaluation (NFC)

[Manuel Brito via Phabricator via llvm-commits]

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When performing symbolic load evaluation we currently check if the defining instruction is unreachable. AFAICT this is not possible because the defining access is a clobber of the load, therefore the defining instruction dominates the load. In NewGVN if we are processing an instruction its because we have deemed it reachable so it's not possible to have an unreachable dominator.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D157263

Files:
  llvm/lib/Transforms/Scalar/NewGVN.cpp


Index: llvm/lib/Transforms/Scalar/NewGVN.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/NewGVN.cpp
+++ llvm/lib/Transforms/Scalar/NewGVN.cpp
@@ -1534,9 +1534,7 @@
   if (!MSSA->isLiveOnEntryDef(DefiningAccess)) {
     if (auto *MD = dyn_cast<MemoryDef>(DefiningAccess)) {
       Instruction *DefiningInst = MD->getMemoryInst();
-      // If the defining instruction is not reachable, replace with poison.
-      if (!ReachableBlocks.count(DefiningInst->getParent()))
-        return createConstantExpression(PoisonValue::get(LI->getType()));
+      
       // This will handle stores and memory insts.  We only do if it the
       // defining access has a different type, or it is a pointer produced by
       // certain memory operations that cause the memory to have a fixed value


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