1 files changed, 38 insertions, 11 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 993c095dc6f..33951e66497 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -317,19 +317,44 @@ static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal,
                                   Value *FalseVal,
                                   InstCombiner::BuilderTy *Builder) {
   const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
-  if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy())
+  if (!IC || !SI.getType()->isIntegerTy())
     return nullptr;
 
   Value *CmpLHS = IC->getOperand(0);
   Value *CmpRHS = IC->getOperand(1);
 
-  if (!match(CmpRHS, m_Zero()))
-    return nullptr;
+  Value *V;
+  unsigned C1Log;
+  bool IsEqualZero;
+  bool NeedAnd = false;
+  if (IC->isEquality()) {
+    if (!match(CmpRHS, m_Zero()))
+      return nullptr;
+
+    const APInt *C1;
+    if (!match(CmpLHS, m_And(m_Value(), m_Power2(C1))))
+      return nullptr;
+
+    V = CmpLHS;
+    C1Log = C1->logBase2();
+    IsEqualZero = IC->getPredicate() == ICmpInst::ICMP_EQ;
+  } else if (IC->getPredicate() == ICmpInst::ICMP_SLT ||
+             IC->getPredicate() == ICmpInst::ICMP_SGT) {
+    // We also need to recognize (icmp slt (trunc (X)), 0) and
+    // (icmp sgt (trunc (X)), -1).
+    IsEqualZero = IC->getPredicate() == ICmpInst::ICMP_SGT;
+    if ((IsEqualZero && !match(CmpRHS, m_AllOnes())) ||
+        (!IsEqualZero && !match(CmpRHS, m_Zero())))
+      return nullptr;
 
-  Value *X;
-  const APInt *C1;
-  if (!match(CmpLHS, m_And(m_Value(X), m_Power2(C1))))
+    if (!match(CmpLHS, m_OneUse(m_Trunc(m_Value(V)))))
+      return nullptr;
+
+    C1Log = CmpLHS->getType()->getScalarSizeInBits() - 1;
+    NeedAnd = true;
+  } else {
     return nullptr;
+  }
 
   const APInt *C2;
   bool OrOnTrueVal = false;
@@ -340,15 +365,11 @@ static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal,
   if (!OrOnFalseVal && !OrOnTrueVal)
     return nullptr;
 
-  Value *V = CmpLHS;
   Value *Y = OrOnFalseVal ? TrueVal : FalseVal;
 
-  unsigned C1Log = C1->logBase2();
   unsigned C2Log = C2->logBase2();
 
-  ICmpInst::Predicate Pred = IC->getPredicate();
-  bool NeedXor = (Pred == ICmpInst::ICMP_NE && OrOnFalseVal) ||
-                 (Pred == ICmpInst::ICMP_EQ && OrOnTrueVal);
+  bool NeedXor = (!IsEqualZero && OrOnFalseVal) || (IsEqualZero && OrOnTrueVal);
   bool NeedShift = C1Log != C2Log;
   bool NeedZExtTrunc = Y->getType()->getIntegerBitWidth() !=
                        V->getType()->getIntegerBitWidth();
@@ -359,6 +380,12 @@ static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal,
       (IC->hasOneUse() + Or->hasOneUse()))
     return nullptr;
 
+  if (NeedAnd) {
+    // Insert the AND instruction on the input to the truncate.
+    APInt C1 = APInt::getOneBitSet(V->getType()->getScalarSizeInBits(), C1Log);
+    V = Builder->CreateAnd(V, ConstantInt::get(V->getType(), C1));
+  }
+
   if (C2Log > C1Log) {
     V = Builder->CreateZExtOrTrunc(V, Y->getType());
     V = Builder->CreateShl(V, C2Log - C1Log);