3 files changed, 11 insertions, 17 deletions
diff --git a/llvm/lib/Analysis/CmpInstAnalysis.cpp b/llvm/lib/Analysis/CmpInstAnalysis.cpp
index c879b8729dc..159c1a2d135 100644
--- a/llvm/lib/Analysis/CmpInstAnalysis.cpp
+++ b/llvm/lib/Analysis/CmpInstAnalysis.cpp
@@ -66,9 +66,11 @@ bool llvm::PredicatesFoldable(ICmpInst::Predicate p1, ICmpInst::Predicate p2) {
 
 bool llvm::decomposeBitTestICmp(Value *LHS, Value *RHS,
                                 CmpInst::Predicate &Pred,
-                                Value *&X, APInt &Mask) {
+                                Value *&X, APInt &Mask, bool LookThruTrunc) {
+  using namespace PatternMatch;
+
   const APInt *C;
-  if (!match(RHS, PatternMatch::m_APInt(C)))
+  if (!match(RHS, m_APInt(C)))
     return false;
 
   switch (Pred) {
@@ -132,6 +134,11 @@ bool llvm::decomposeBitTestICmp(Value *LHS, Value *RHS,
     break;
   }
 
-  X = LHS;
+  if (LookThruTrunc && match(LHS, m_Trunc(m_Value(X)))) {
+    Mask = Mask.zext(X->getType()->getScalarSizeInBits());
+  } else {
+    X = LHS;
+  }
+
   return true;
 }
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index d155f6b4803..94d71817049 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -3629,19 +3629,6 @@ static Value *simplifySelectWithFakeICmpEq(Value *CmpLHS, Value *CmpRHS,
   if (!decomposeBitTestICmp(CmpLHS, CmpRHS, Pred, X, Mask))
     return nullptr;
 
-  unsigned BitWidth = TrueVal->getType()->getScalarSizeInBits();
-  if (!BitWidth)
-    return nullptr;
-
-  Value *ExtX;
-  if (match(X, m_Trunc(m_Value(ExtX))) &&
-      (ExtX == TrueVal || ExtX == FalseVal)) {
-    // icmp slt (trunc X), 0  <--> icmp ne (and X, C), 0
-    // icmp sgt (trunc X), -1 <--> icmp eq (and X, C), 0
-    X = ExtX;
-    Mask = Mask.zext(BitWidth);
-  }
-
   return simplifySelectBitTest(TrueVal, FalseVal, X, &Mask,
                                Pred == ICmpInst::ICMP_EQ);
 }
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 11602ab101e..83aeda5935e 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -724,7 +724,7 @@ Instruction *InstCombiner::foldSelectInstWithICmp(SelectInst &SI,
       ICmpInst::Predicate Pred = ICI->getPredicate();
       Value *X;
       APInt Mask;
-      if (decomposeBitTestICmp(CmpLHS, CmpRHS, Pred, X, Mask)) {
+      if (decomposeBitTestICmp(CmpLHS, CmpRHS, Pred, X, Mask, false)) {
         if (Mask.isSignMask()) {
           assert(X == CmpLHS && "Expected to use the compare input directly");
           assert(ICmpInst::isEquality(Pred) && "Expected equality predicate");