[InstCombine] Use replaceOperand() in a few more places

To make sure the old operands get DCEd.

NFC apart from worklist order changes.

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -5963,16 +5963,15 @@ static Instruction *foldFCmpReciprocalAndZero(FCmpInst &I, Instruction *LHSI,
 }
 
 /// Optimize fabs(X) compared with zero.
-static Instruction *foldFabsWithFcmpZero(FCmpInst &I) {
+static Instruction *foldFabsWithFcmpZero(FCmpInst &I, InstCombiner &IC) {
   Value *X;
   if (!match(I.getOperand(0), m_Intrinsic<Intrinsic::fabs>(m_Value(X))) ||
       !match(I.getOperand(1), m_PosZeroFP()))
     return nullptr;
 
-  auto replacePredAndOp0 = [](FCmpInst *I, FCmpInst::Predicate P, Value *X) {
+  auto replacePredAndOp0 = [&IC](FCmpInst *I, FCmpInst::Predicate P, Value *X) {
     I->setPredicate(P);
-    I->setOperand(0, X);
-    return I;
+    return IC.replaceOperand(*I, 0, X);
   };
 
   switch (I.getPredicate()) {
@@ -6137,7 +6136,7 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
   }
   }
 
-  if (Instruction *R = foldFabsWithFcmpZero(I))
+  if (Instruction *R = foldFabsWithFcmpZero(I, *this))
     return R;
 
   if (match(Op0, m_FNeg(m_Value(X)))) {

llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp

@@ -682,10 +682,8 @@ Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
   Type *Ty = I.getType();
 
   // The RHS is known non-zero.
-  if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, I)) {
-    I.setOperand(1, V);
-    return &I;
-  }
+  if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, I))
+    return replaceOperand(I, 1, V);
 
   // Handle cases involving: [su]div X, (select Cond, Y, Z)
   // This does not apply for fdiv.
@@ -799,8 +797,8 @@ Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
     bool HasNSW = cast<OverflowingBinaryOperator>(Op1)->hasNoSignedWrap();
     bool HasNUW = cast<OverflowingBinaryOperator>(Op1)->hasNoUnsignedWrap();
     if ((IsSigned && HasNSW) || (!IsSigned && HasNUW)) {
-      I.setOperand(0, ConstantInt::get(Ty, 1));
-      I.setOperand(1, Y);
+      replaceOperand(I, 0, ConstantInt::get(Ty, 1));
+      replaceOperand(I, 1, Y);
       return &I;
     }
   }
@@ -1276,8 +1274,8 @@ Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
   // -X / -Y -> X / Y
   Value *X, *Y;
   if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_FNeg(m_Value(Y)))) {
-    I.setOperand(0, X);
-    I.setOperand(1, Y);
+    replaceOperand(I, 0, X);
+    replaceOperand(I, 1, Y);
     return &I;
   }
 
@@ -1286,8 +1284,8 @@ Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
   // We can ignore the possibility that X is infinity because INF/INF is NaN.
   if (I.hasNoNaNs() && I.hasAllowReassoc() &&
       match(Op1, m_c_FMul(m_Specific(Op0), m_Value(Y)))) {
-    I.setOperand(0, ConstantFP::get(I.getType(), 1.0));
-    I.setOperand(1, Y);
+    replaceOperand(I, 0, ConstantFP::get(I.getType(), 1.0));
+    replaceOperand(I, 1, Y);
     return &I;
   }
 
@@ -1313,10 +1311,8 @@ Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
 
   // The RHS is known non-zero.
-  if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, I)) {
-    I.setOperand(1, V);
-    return &I;
-  }
+  if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, I))
+    return replaceOperand(I, 1, V);
 
   // Handle cases involving: rem X, (select Cond, Y, Z)
   if (simplifyDivRemOfSelectWithZeroOp(I))

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -1036,7 +1036,7 @@ canonicalizeMinMaxWithConstant(SelectInst &Sel, ICmpInst &Cmp,
 /// Canonicalize all these variants to 1 pattern.
 /// This makes CSE more likely.
 static Instruction *canonicalizeAbsNabs(SelectInst &Sel, ICmpInst &Cmp,
-                                        InstCombiner::BuilderTy &Builder) {
+                                        InstCombiner &IC) {
   if (!Cmp.hasOneUse() || !isa<Constant>(Cmp.getOperand(1)))
     return nullptr;
 
@@ -1085,12 +1085,14 @@ static Instruction *canonicalizeAbsNabs(SelectInst &Sel, ICmpInst &Cmp,
   // Create the canonical RHS: RHS = sub (0, LHS).
   if (!RHSCanonicalized) {
     assert(RHS->hasOneUse() && "RHS use number is not right");
-    RHS = Builder.CreateNeg(LHS);
+    RHS = IC.Builder.CreateNeg(LHS);
     if (TVal == LHS) {
-      Sel.setFalseValue(RHS);
+      // Replace false value.
+      IC.replaceOperand(Sel, 2, RHS);
       FVal = RHS;
     } else {
-      Sel.setTrueValue(RHS);
+      // Replace true value.
+      IC.replaceOperand(Sel, 1, RHS);
       TVal = RHS;
     }
   }
@@ -1398,7 +1400,7 @@ Instruction *InstCombiner::foldSelectInstWithICmp(SelectInst &SI,
   if (Instruction *NewSel = canonicalizeMinMaxWithConstant(SI, *ICI, *this))
     return NewSel;
 
-  if (Instruction *NewAbs = canonicalizeAbsNabs(SI, *ICI, Builder))
+  if (Instruction *NewAbs = canonicalizeAbsNabs(SI, *ICI, *this))
     return NewAbs;
 
   if (Instruction *NewAbs = canonicalizeClampLike(SI, *ICI, Builder))