[PATCH] D93065: [InstCombine] Disable optimizations of select instructions that causes propagation of poison values

[Congzhe Cao via Phabricator via llvm-commits]

congzhe updated this revision to Diff 311362.
congzhe added a comment.

Updated to address comments.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D93065/new/

https://reviews.llvm.org/D93065

Files:
  llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp


Index: llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -2612,50 +2612,26 @@
 
   CmpInst::Predicate Pred;
 
-  if (SelType->isIntOrIntVectorTy(1) &&
-      TrueVal->getType() == CondVal->getType()) {
-    if (match(TrueVal, m_One())) {
-      // Change: A = select B, true, C --> A = or B, C
-      return BinaryOperator::CreateOr(CondVal, FalseVal);
-    }
-    if (match(TrueVal, m_Zero())) {
-      // Change: A = select B, false, C --> A = and !B, C
-      Value *NotCond = Builder.CreateNot(CondVal, "not." + CondVal->getName());
-      return BinaryOperator::CreateAnd(NotCond, FalseVal);
-    }
-    if (match(FalseVal, m_Zero())) {
-      // Change: A = select B, C, false --> A = and B, C
-      return BinaryOperator::CreateAnd(CondVal, TrueVal);
-    }
-    if (match(FalseVal, m_One())) {
-      // Change: A = select B, C, true --> A = or !B, C
-      Value *NotCond = Builder.CreateNot(CondVal, "not." + CondVal->getName());
-      return BinaryOperator::CreateOr(NotCond, TrueVal);
-    }
-
-    // select a, a, b  -> a | b
-    // select a, b, a  -> a & b
-    if (CondVal == TrueVal)
-      return BinaryOperator::CreateOr(CondVal, FalseVal);
-    if (CondVal == FalseVal)
-      return BinaryOperator::CreateAnd(CondVal, TrueVal);
-
-    // select a, ~a, b -> (~a) & b
-    // select a, b, ~a -> (~a) | b
-    if (match(TrueVal, m_Not(m_Specific(CondVal))))
-      return BinaryOperator::CreateAnd(TrueVal, FalseVal);
-    if (match(FalseVal, m_Not(m_Specific(CondVal))))
-      return BinaryOperator::CreateOr(TrueVal, FalseVal);
-  }
-
   // Selecting between two integer or vector splat integer constants?
   //
   // Note that we don't handle a scalar select of vectors:
   // select i1 %c, <2 x i8> <1, 1>, <2 x i8> <0, 0>
   // because that may need 3 instructions to splat the condition value:
   // extend, insertelement, shufflevector.
+
+  // Do not handle i1 TrueVal and FalseVal otherwise would result in
+  // zext i1 to i1.
+  auto checkValWidth = [&](Value* val) -> bool {
+    Type *t= val->getType();
+    if (t->isIntegerTy())
+      return t->getIntegerBitWidth() != 1;
+    if (t->isVectorTy())
+      return t->getScalarSizeInBits() != 1;
+    return false;
+  };
   if (SelType->isIntOrIntVectorTy() &&
-      CondVal->getType()->isVectorTy() == SelType->isVectorTy()) {
+      CondVal->getType()->isVectorTy() == SelType->isVectorTy() &&
+      checkValWidth(TrueVal) && checkValWidth(FalseVal)) {
     // select C, 1, 0 -> zext C to int
     if (match(TrueVal, m_One()) && match(FalseVal, m_Zero()))
       return new ZExtInst(CondVal, SelType);


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