[llvm] f3d4166 - [InstCombine] Report change in non zero phi transform

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2020-03-31T21:52:40+02:00
New Revision: f3d4166368b0449baea1e7d8e043d0fe76930179

URL: https://github.com/llvm/llvm-project/commit/f3d4166368b0449baea1e7d8e043d0fe76930179
DIFF: https://github.com/llvm/llvm-project/commit/f3d4166368b0449baea1e7d8e043d0fe76930179.diff

LOG: [InstCombine] Report change in non zero phi transform

We need to inform InstCombine (and transitively the pass manager)
that we changed an instruction.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp b/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
index 6c2aead5a754..9cdb68d07aa1 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
@@ -1194,15 +1194,22 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) {
     if (CmpInst && isa<IntegerType>(PN.getType()) && CmpInst->isEquality() &&
         match(CmpInst->getOperand(1), m_Zero())) {
       ConstantInt *NonZeroConst = nullptr;
+      bool MadeChange = false;
       for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
         Instruction *CtxI = PN.getIncomingBlock(i)->getTerminator();
         Value *VA = PN.getIncomingValue(i);
         if (isKnownNonZero(VA, DL, 0, &AC, CtxI, &DT)) {
           if (!NonZeroConst)
             NonZeroConst = GetAnyNonZeroConstInt(PN);
-          PN.setIncomingValue(i, NonZeroConst);
+
+          if (NonZeroConst != VA) {
+            PN.setIncomingValue(i, NonZeroConst);
+            MadeChange = true;
+          }
         }
       }
+      if (MadeChange)
+        return &PN;
     }
   }