1 files changed, 138 insertions, 11 deletions

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 097b99e..ec56d88 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -3144,6 +3144,90 @@ Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
                             RecursionLimit);
 }
 
+/// SimplifyWithOpReplaced - See if V simplifies when its operand Op is
+/// replaced with RepOp.
+static const Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
+                                           const Query &Q,
+                                           unsigned MaxRecurse) {
+  // Trivial replacement.
+  if (V == Op)
+    return RepOp;
+
+  auto *I = dyn_cast<Instruction>(V);
+  if (!I)
+    return nullptr;
+
+  // If this is a binary operator, try to simplify it with the replaced op.
+  if (auto *B = dyn_cast<BinaryOperator>(I)) {
+    // Consider:
+    //   %cmp = icmp eq i32 %x, 2147483647
+    //   %add = add nsw i32 %x, 1
+    //   %sel = select i1 %cmp, i32 -2147483648, i32 %add
+    //
+    // We can't replace %sel with %add unless we strip away the flags.
+    if (isa<OverflowingBinaryOperator>(B))
+      if (B->hasNoSignedWrap() || B->hasNoUnsignedWrap())
+        return nullptr;
+    if (isa<PossiblyExactOperator>(B))
+      if (B->isExact())
+        return nullptr;
+
+    if (MaxRecurse) {
+      if (B->getOperand(0) == Op)
+        return SimplifyBinOp(B->getOpcode(), RepOp, B->getOperand(1), Q,
+                             MaxRecurse - 1);
+      if (B->getOperand(1) == Op)
+        return SimplifyBinOp(B->getOpcode(), B->getOperand(0), RepOp, Q,
+                             MaxRecurse - 1);
+    }
+  }
+
+  // Same for CmpInsts.
+  if (CmpInst *C = dyn_cast<CmpInst>(I)) {
+    if (MaxRecurse) {
+      if (C->getOperand(0) == Op)
+        return SimplifyCmpInst(C->getPredicate(), RepOp, C->getOperand(1), Q,
+                               MaxRecurse - 1);
+      if (C->getOperand(1) == Op)
+        return SimplifyCmpInst(C->getPredicate(), C->getOperand(0), RepOp, Q,
+                               MaxRecurse - 1);
+    }
+  }
+
+  // TODO: We could hand off more cases to instsimplify here.
+
+  // If all operands are constant after substituting Op for RepOp then we can
+  // constant fold the instruction.
+  if (Constant *CRepOp = dyn_cast<Constant>(RepOp)) {
+    // Build a list of all constant operands.
+    SmallVector<Constant *, 8> ConstOps;
+    for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
+      if (I->getOperand(i) == Op)
+        ConstOps.push_back(CRepOp);
+      else if (Constant *COp = dyn_cast<Constant>(I->getOperand(i)))
+        ConstOps.push_back(COp);
+      else
+        break;
+    }
+
+    // All operands were constants, fold it.
+    if (ConstOps.size() == I->getNumOperands()) {
+      if (CmpInst *C = dyn_cast<CmpInst>(I))
+        return ConstantFoldCompareInstOperands(C->getPredicate(), ConstOps[0],
+                                               ConstOps[1], Q.DL, Q.TLI);
+
+      if (LoadInst *LI = dyn_cast<LoadInst>(I))
+        if (!LI->isVolatile())
+          return ConstantFoldLoadFromConstPtr(ConstOps[0], Q.DL);
+
+      return ConstantFoldInstOperands(I->getOpcode(), I->getType(), ConstOps,
+                                      Q.DL, Q.TLI);
+    }
+  }
+
+  return nullptr;
+}
+
 /// SimplifySelectInst - Given operands for a SelectInst, see if we can fold
 /// the result.  If not, this returns null.
 static Value *SimplifySelectInst(Value *CondVal, Value *TrueVal,
@@ -3172,29 +3256,28 @@ static Value *SimplifySelectInst(Value *CondVal, Value *TrueVal,
   if (isa<UndefValue>(FalseVal))   // select C, X, undef -> X
     return TrueVal;
 
-  const auto *ICI = dyn_cast<ICmpInst>(CondVal);
-  unsigned BitWidth = TrueVal->getType()->getScalarSizeInBits();
-  if (ICI && BitWidth) {
+  if (const auto *ICI = dyn_cast<ICmpInst>(CondVal)) {
+    unsigned BitWidth = Q.DL.getTypeSizeInBits(TrueVal->getType());
     ICmpInst::Predicate Pred = ICI->getPredicate();
+    Value *CmpLHS = ICI->getOperand(0);
+    Value *CmpRHS = ICI->getOperand(1);
     APInt MinSignedValue = APInt::getSignBit(BitWidth);
     Value *X;
     const APInt *Y;
     bool TrueWhenUnset;
     bool IsBitTest = false;
     if (ICmpInst::isEquality(Pred) &&
-        match(ICI->getOperand(0), m_And(m_Value(X), m_APInt(Y))) &&
-        match(ICI->getOperand(1), m_Zero())) {
+        match(CmpLHS, m_And(m_Value(X), m_APInt(Y))) &&
+        match(CmpRHS, m_Zero())) {
       IsBitTest = true;
       TrueWhenUnset = Pred == ICmpInst::ICMP_EQ;
-    } else if (Pred == ICmpInst::ICMP_SLT &&
-               match(ICI->getOperand(1), m_Zero())) {
-      X = ICI->getOperand(0);
+    } else if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, m_Zero())) {
+      X = CmpLHS;
       Y = &MinSignedValue;
       IsBitTest = true;
       TrueWhenUnset = false;
-    } else if (Pred == ICmpInst::ICMP_SGT &&
-               match(ICI->getOperand(1), m_AllOnes())) {
-      X = ICI->getOperand(0);
+    } else if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, m_AllOnes())) {
+      X = CmpLHS;
       Y = &MinSignedValue;
       IsBitTest = true;
       TrueWhenUnset = true;
@@ -3225,6 +3308,50 @@ static Value *SimplifySelectInst(Value *CondVal, Value *TrueVal,
           return TrueWhenUnset ? TrueVal : FalseVal;
       }
     }
+    if (ICI->hasOneUse()) {
+      const APInt *C;
+      if (match(CmpRHS, m_APInt(C))) {
+        // X < MIN ? T : F  -->  F
+        if (Pred == ICmpInst::ICMP_SLT && C->isMinSignedValue())
+          return FalseVal;
+        // X < MIN ? T : F  -->  F
+        if (Pred == ICmpInst::ICMP_ULT && C->isMinValue())
+          return FalseVal;
+        // X > MAX ? T : F  -->  F
+        if (Pred == ICmpInst::ICMP_SGT && C->isMaxSignedValue())
+          return FalseVal;
+        // X > MAX ? T : F  -->  F
+        if (Pred == ICmpInst::ICMP_UGT && C->isMaxValue())
+          return FalseVal;
+      }
+    }
+
+    // If we have an equality comparison then we know the value in one of the
+    // arms of the select. See if substituting this value into the arm and
+    // simplifying the result yields the same value as the other arm.
+    if (Pred == ICmpInst::ICMP_EQ) {
+      if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, Q, MaxRecurse) ==
+              TrueVal ||
+          SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, Q, MaxRecurse) ==
+              TrueVal)
+        return FalseVal;
+      if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, Q, MaxRecurse) ==
+              FalseVal ||
+          SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, Q, MaxRecurse) ==
+              FalseVal)
+        return FalseVal;
+    } else if (Pred == ICmpInst::ICMP_NE) {
+      if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, Q, MaxRecurse) ==
+              FalseVal ||
+          SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, Q, MaxRecurse) ==
+              FalseVal)
+        return TrueVal;
+      if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, Q, MaxRecurse) ==
+              TrueVal ||
+          SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, Q, MaxRecurse) ==
+              TrueVal)
+        return TrueVal;
+    }
   }
 
   return nullptr;