[InstCombine] Use replaceOperand() in more places

[nikic]

Summary

Followup to D73919 with another batch of replacements of setOperand -> replaceOperand, to make sure the old operand gets DCEd right away.

[spatel]

LGTM

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

case Intrinsic::fshr: {
     Type *Ty = II->getType();
     unsigned BitWidth = Ty->getScalarSizeInBits();
     Constant *ShAmtC;
     if (match(II->getArgOperand(2), m_Constant(ShAmtC)) &&
         !isa<ConstantExpr>(ShAmtC) && !ShAmtC->containsConstantExpression()) {
       // Canonicalize a shift amount constant operand to modulo the bit-width.
       Constant *WidthC = ConstantInt::get(Ty, BitWidth);
       Constant *ModuloC = ConstantExpr::getURem(ShAmtC, WidthC);
-      if (ModuloC != ShAmtC) {
-        II->setArgOperand(2, ModuloC);
-        return II;
-      }
+      if (ModuloC != ShAmtC)
+        return replaceOperand(*II, 2, ModuloC);
+
       assert(ConstantExpr::getICmp(ICmpInst::ICMP_UGT, WidthC, ShAmtC) ==
                  ConstantInt::getTrue(CmpInst::makeCmpResultType(Ty)) &&
              "Shift amount expected to be modulo bitwidth");
 
       // Canonicalize funnel shift right by constant to funnel shift left. This
       // is not entirely arbitrary. For historical reasons, the backend may
       // recognize rotate left patterns but miss rotate right patterns.
       if (IID == Intrinsic::fshr) {
case Intrinsic::fma: {
     if (Instruction *I = canonicalizeConstantArg0ToArg1(CI))
       return I;
 
     // fma fneg(x), fneg(y), z -> fma x, y, z
     Value *Src0 = II->getArgOperand(0);
     Value *Src1 = II->getArgOperand(1);
     Value *X, *Y;
     if (match(Src0, m_FNeg(m_Value(X))) && match(Src1, m_FNeg(m_Value(Y)))) {
-      II->setArgOperand(0, X);
-      II->setArgOperand(1, Y);
+      replaceOperand(*II, 0, X);
+      replaceOperand(*II, 1, Y);
       return II;
     }
 
     // fma fabs(x), fabs(x), z -> fma x, x, z
     if (match(Src0, m_FAbs(m_Value(X))) &&
         match(Src1, m_FAbs(m_Specific(X)))) {
-      II->setArgOperand(0, X);
-      II->setArgOperand(1, X);
+      replaceOperand(*II, 0, X);
+      replaceOperand(*II, 1, X);
       return II;
     }
 
     // Try to simplify the underlying FMul. We can only apply simplifications
     // that do not require rounding.
     if (Value *V = SimplifyFMAFMul(II->getArgOperand(0), II->getArgOperand(1),
                                    II->getFastMathFlags(),
                                    SQ.getWithInstruction(II))) {
if (match(II->getArgOperand(1), m_APFloat(C)) && C->isNegative()) {
                                                  II->getArgOperand(0), II);
       return replaceInstUsesWith(*II, Builder.CreateFNegFMF(Fabs, II));
     }
 
     // Propagate sign argument through nested calls:
     // copysign X, (copysign ?, SignArg) --> copysign X, SignArg
     Value *SignArg;
     if (match(II->getArgOperand(1),
-              m_Intrinsic<Intrinsic::copysign>(m_Value(), m_Value(SignArg)))) {
-      II->setArgOperand(1, SignArg);
-      return II;
-    }
+              m_Intrinsic<Intrinsic::copysign>(m_Value(), m_Value(SignArg))))
+      return replaceOperand(*II, 1, SignArg);
 
     break;
   }
   case Intrinsic::fabs: {
     Value *Cond;
     Constant *LHS, *RHS;
     if (match(II->getArgOperand(0),
               m_Select(m_Value(Cond), m_Constant(LHS), m_Constant(RHS)))) {
Instruction *InstCombiner::visitCallInst(CallInst &CI) {
   }
   case Intrinsic::cos:
   case Intrinsic::amdgcn_cos: {
     Value *X;
     Value *Src = II->getArgOperand(0);
     if (match(Src, m_FNeg(m_Value(X))) || match(Src, m_FAbs(m_Value(X)))) {
       // cos(-x) -> cos(x)
       // cos(fabs(x)) -> cos(x)
-      II->setArgOperand(0, X);
-      return II;
+      return replaceOperand(*II, 0, X);
     }
     break;
   }
   case Intrinsic::sin: {
     Value *X;
     if (match(II->getArgOperand(0), m_OneUse(m_FNeg(m_Value(X))))) {
       // sin(-x) --> -sin(x)
       Value *NewSin = Builder.CreateUnaryIntrinsic(Intrinsic::sin, X, II);
case Intrinsic::x86_avx512_cmp_ps_512: {
     // NNAN is not needed because nans compare the same for both compares.
     // The compare intrinsic uses the above assumptions and therefore
     // doesn't require additional flags.
     if ((match(Arg0, m_OneUse(m_FSub(m_Value(A), m_Value(B)))) &&
          match(Arg1, m_PosZeroFP()) && isa<Instruction>(Arg0) &&
          cast<Instruction>(Arg0)->getFastMathFlags().noInfs())) {
       if (Arg0IsZero)
         std::swap(A, B);
-      II->setArgOperand(0, A);
-      II->setArgOperand(1, B);
+      replaceOperand(*II, 0, A);
+      replaceOperand(*II, 1, B);
       return II;
     }
     break;
   }
 
   case Intrinsic::x86_avx512_add_ps_512:
   case Intrinsic::x86_avx512_div_ps_512:
   case Intrinsic::x86_avx512_mul_ps_512:

   case Intrinsic::arm_neon_vst4:
   case Intrinsic::arm_neon_vst2lane:
   case Intrinsic::arm_neon_vst3lane:
   case Intrinsic::arm_neon_vst4lane: {
     unsigned MemAlign =
         getKnownAlignment(II->getArgOperand(0), DL, II, &AC, &DT);
     unsigned AlignArg = II->getNumArgOperands() - 1;
     ConstantInt *IntrAlign = dyn_cast<ConstantInt>(II->getArgOperand(AlignArg));
-    if (IntrAlign && IntrAlign->getZExtValue() < MemAlign) {
-      II->setArgOperand(AlignArg,
+    if (IntrAlign && IntrAlign->getZExtValue() < MemAlign)
+      return replaceOperand(*II, AlignArg,
                             ConstantInt::get(Type::getInt32Ty(II->getContext()),
                                              MemAlign, false));
-      return II;
-    }
     break;
   }
 
   case Intrinsic::arm_neon_vtbl1:
   case Intrinsic::aarch64_neon_tbl1:
     if (Value *V = simplifyNeonTbl1(*II, Builder))
       return replaceInstUsesWith(*II, V);
     break;

   case Intrinsic::aarch64_crypto_aese: {
     Value *DataArg = II->getArgOperand(0);
     Value *KeyArg  = II->getArgOperand(1);
 
     // Try to use the builtin XOR in AESE and AESD to eliminate a prior XOR
     Value *Data, *Key;
     if (match(KeyArg, m_ZeroInt()) &&
         match(DataArg, m_Xor(m_Value(Data), m_Value(Key)))) {
-      II->setArgOperand(0, Data);
-      II->setArgOperand(1, Key);
+      replaceOperand(*II, 0, Data);
+      replaceOperand(*II, 1, Key);
       return II;
     }
     break;
   }
   case Intrinsic::arm_mve_pred_i2v: {
     Value *Arg = II->getArgOperand(0);
     Value *ArgArg;
     if (match(Arg, m_Intrinsic<Intrinsic::arm_mve_pred_v2i>(m_Value(ArgArg))) &&
if (Mask == (N_ZERO | P_ZERO)) {
       Value *FCmp = Builder.CreateFCmpOEQ(
         Src0, ConstantFP::get(Src0->getType(), 0.0));
 
       FCmp->takeName(II);
       return replaceInstUsesWith(*II, FCmp);
     }
 
     // fp_class (nnan x), qnan|snan|other -> fp_class (nnan x), other
-    if (((Mask & S_NAN) || (Mask & Q_NAN)) && isKnownNeverNaN(Src0, &TLI)) {
-      II->setArgOperand(1, ConstantInt::get(Src1->getType(),
+    if (((Mask & S_NAN) || (Mask & Q_NAN)) && isKnownNeverNaN(Src0, &TLI))
+      return replaceOperand(*II, 1, ConstantInt::get(Src1->getType(),
                                                      Mask & ~(S_NAN | Q_NAN)));
-      return II;
-    }
 
     const ConstantFP *CVal = dyn_cast<ConstantFP>(Src0);
     if (!CVal) {
       if (isa<UndefValue>(Src0))
         return replaceInstUsesWith(*II, UndefValue::get(II->getType()));
 
       // Clamp mask to used bits
       if ((Mask & FullMask) != Mask) {
case Intrinsic::amdgcn_sbfe: {
     unsigned IntSize = Ty->getIntegerBitWidth();
 
     ConstantInt *CWidth = dyn_cast<ConstantInt>(II->getArgOperand(2));
     if (CWidth) {
       Width = CWidth->getZExtValue();
       if ((Width & (IntSize - 1)) == 0)
         return replaceInstUsesWith(*II, ConstantInt::getNullValue(Ty));
 
-      if (Width >= IntSize) {
-        // Hardware ignores high bits, so remove those.
-        II->setArgOperand(2, ConstantInt::get(CWidth->getType(),
+      if (Width >= IntSize)
+        return replaceOperand(*II, 2, ConstantInt::get(CWidth->getType(),
                                                        Width & (IntSize - 1)));
-        return II;
-      }
     }
 
     unsigned Offset;
     ConstantInt *COffset = dyn_cast<ConstantInt>(II->getArgOperand(1));
     if (COffset) {
       Offset = COffset->getZExtValue();
-      if (Offset >= IntSize) {
-        II->setArgOperand(1, ConstantInt::get(COffset->getType(),
+      if (Offset >= IntSize)
+        return replaceOperand(*II, 1, ConstantInt::get(COffset->getType(),
                                                        Offset & (IntSize - 1)));
-        return II;
-      }
     }
 
     bool Signed = IID == Intrinsic::amdgcn_sbfe;
 
     if (!CWidth || !COffset)
       break;
 
     // The case of Width == 0 is handled above, which makes this tranformation
case Intrinsic::amdgcn_exp_compr: {
 
     bool IsCompr = IID == Intrinsic::amdgcn_exp_compr;
     bool Changed = false;
     for (int I = 0; I < (IsCompr ? 2 : 4); ++I) {
       if ((!IsCompr && (EnBits & (1 << I)) == 0) ||
           (IsCompr && ((EnBits & (0x3 << (2 * I))) == 0))) {
         Value *Src = II->getArgOperand(I + 2);
         if (!isa<UndefValue>(Src)) {
-          II->setArgOperand(I + 2, UndefValue::get(Src->getType()));
+          replaceOperand(*II, I + 2, UndefValue::get(Src->getType()));
           Changed = true;
         }
       }
     }
 
     if (Changed)
       return II;
 
case Intrinsic::amdgcn_fcmp: {
     //   -> llvm.amdgcn.icmp(zext (i1 x), 0, ne)
     // llvm.amdgcn.icmp(sext (i1 x), -1, eq)
     //   -> llvm.amdgcn.icmp(sext (i1 x), 0, ne)
     Value *ExtSrc;
     if (CCVal == CmpInst::ICMP_EQ &&
         ((match(Src1, m_One()) && match(Src0, m_ZExt(m_Value(ExtSrc)))) ||
          (match(Src1, m_AllOnes()) && match(Src0, m_SExt(m_Value(ExtSrc))))) &&
         ExtSrc->getType()->isIntegerTy(1)) {
-      II->setArgOperand(1, ConstantInt::getNullValue(Src1->getType()));
-      II->setArgOperand(2, ConstantInt::get(CC->getType(), CmpInst::ICMP_NE));
+      replaceOperand(*II, 1, ConstantInt::getNullValue(Src1->getType()));
+      replaceOperand(*II, 2, ConstantInt::get(CC->getType(), CmpInst::ICMP_NE));
       return II;
     }
 
     CmpInst::Predicate SrcPred;
     Value *SrcLHS;
     Value *SrcRHS;
 
     // Fold compare eq/ne with 0 from a compare result as the predicate to the
if (match(NextInst,
       // Otherwise canonicalize guard(a); guard(b) -> guard(a & b).
       if (CurrCond != NextCond) {
         Instruction *MoveI = II->getNextNonDebugInstruction();
         while (MoveI != NextInst) {
           auto *Temp = MoveI;
           MoveI = MoveI->getNextNonDebugInstruction();
           Temp->moveBefore(II);
         }
-        II->setArgOperand(0, Builder.CreateAnd(CurrCond, NextCond));
+        replaceOperand(*II, 0, Builder.CreateAnd(CurrCond, NextCond));
       }
       eraseInstFromFunction(*NextInst);
       return II;
     }
     break;
   }
   }
   return visitCallBase(*II);

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

if (I.isAssociative()) {
       if (Op0 && Op0->getOpcode() == Opcode) {
         Value *A = Op0->getOperand(0);
         Value *B = Op0->getOperand(1);
         Value *C = I.getOperand(1);
 
         // Does "B op C" simplify?
         if (Value *V = SimplifyBinOp(Opcode, B, C, SQ.getWithInstruction(&I))) {
           // It simplifies to V.  Form "A op V".
-          I.setOperand(0, A);
-          I.setOperand(1, V);
+          replaceOperand(I, 0, A);
+          replaceOperand(I, 1, V);
           bool IsNUW = hasNoUnsignedWrap(I) && hasNoUnsignedWrap(*Op0);
           bool IsNSW = maintainNoSignedWrap(I, B, C) && hasNoSignedWrap(*Op0);
 
           // Conservatively clear all optional flags since they may not be
           // preserved by the reassociation. Reset nsw/nuw based on the above
           // analysis.
           ClearSubclassDataAfterReassociation(I);
 
if (I.isAssociative()) {
       if (Op1 && Op1->getOpcode() == Opcode) {
         Value *A = I.getOperand(0);
         Value *B = Op1->getOperand(0);
         Value *C = Op1->getOperand(1);
 
         // Does "A op B" simplify?
         if (Value *V = SimplifyBinOp(Opcode, A, B, SQ.getWithInstruction(&I))) {
           // It simplifies to V.  Form "V op C".
-          I.setOperand(0, V);
-          I.setOperand(1, C);
+          replaceOperand(I, 0, V);
+          replaceOperand(I, 1, C);
           // Conservatively clear the optional flags, since they may not be
           // preserved by the reassociation.
           ClearSubclassDataAfterReassociation(I);
           Changed = true;
           ++NumReassoc;
           continue;
         }
       }
if (I.isAssociative() && I.isCommutative()) {
       if (Op0 && Op0->getOpcode() == Opcode) {
         Value *A = Op0->getOperand(0);
         Value *B = Op0->getOperand(1);
         Value *C = I.getOperand(1);
 
         // Does "C op A" simplify?
         if (Value *V = SimplifyBinOp(Opcode, C, A, SQ.getWithInstruction(&I))) {
           // It simplifies to V.  Form "V op B".
-          I.setOperand(0, V);
-          I.setOperand(1, B);
+          replaceOperand(I, 0, V);
+          replaceOperand(I, 1, B);
           // Conservatively clear the optional flags, since they may not be
           // preserved by the reassociation.
           ClearSubclassDataAfterReassociation(I);
           Changed = true;
           ++NumReassoc;
           continue;
         }
       }
 
       // Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies.
       if (Op1 && Op1->getOpcode() == Opcode) {
         Value *A = I.getOperand(0);
         Value *B = Op1->getOperand(0);
         Value *C = Op1->getOperand(1);
 
         // Does "C op A" simplify?
         if (Value *V = SimplifyBinOp(Opcode, C, A, SQ.getWithInstruction(&I))) {
           // It simplifies to V.  Form "B op V".
-          I.setOperand(0, B);
-          I.setOperand(1, V);
+          replaceOperand(I, 0, B);
+          replaceOperand(I, 1, V);
           // Conservatively clear the optional flags, since they may not be
           // preserved by the reassociation.
           ClearSubclassDataAfterReassociation(I);
           Changed = true;
           ++NumReassoc;
           continue;
         }
       }
if (I.isAssociative() && I.isCommutative()) {
          if (isa<FPMathOperator>(NewBO)) {
           FastMathFlags Flags = I.getFastMathFlags();
           Flags &= Op0->getFastMathFlags();
           Flags &= Op1->getFastMathFlags();
           NewBO->setFastMathFlags(Flags);
         }
         InsertNewInstWith(NewBO, I);
         NewBO->takeName(Op1);
-        I.setOperand(0, NewBO);
-        I.setOperand(1, ConstantExpr::get(Opcode, C1, C2));
+        replaceOperand(I, 0, NewBO);
+        replaceOperand(I, 1, ConstantExpr::get(Opcode, C1, C2));
         // Conservatively clear the optional flags, since they may not be
         // preserved by the reassociation.
         ClearSubclassDataAfterReassociation(I);
         if (IsNUW)
           I.setHasNoUnsignedWrap(true);
 
         Changed = true;
         continue;

 }
 
 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
   // Change br (not X), label True, label False to: br X, label False, True
   Value *X = nullptr;
   if (match(&BI, m_Br(m_Not(m_Value(X)), m_BasicBlock(), m_BasicBlock())) &&
       !isa<Constant>(X)) {
     // Swap Destinations and condition...
-    BI.setCondition(X);
     BI.swapSuccessors();
-    return &BI;
+    return replaceOperand(BI, 0, X);
   }
 
   // If the condition is irrelevant, remove the use so that other
   // transforms on the condition become more effective.
   if (BI.isConditional() && !isa<ConstantInt>(BI.getCondition()) &&
-      BI.getSuccessor(0) == BI.getSuccessor(1)) {
-    BI.setCondition(ConstantInt::getFalse(BI.getCondition()->getType()));
-    return &BI;
-  }
+      BI.getSuccessor(0) == BI.getSuccessor(1))
+    return replaceOperand(
+        BI, 0, ConstantInt::getFalse(BI.getCondition()->getType()));
 
   // Canonicalize, for example, icmp_ne -> icmp_eq or fcmp_one -> fcmp_oeq.
   CmpInst::Predicate Pred;
   if (match(&BI, m_Br(m_OneUse(m_Cmp(Pred, m_Value(), m_Value())),
                       m_BasicBlock(), m_BasicBlock())) &&
       !isCanonicalPredicate(Pred)) {
     // Swap destinations and condition.
     CmpInst *Cond = cast<CmpInst>(BI.getCondition());
Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
   if (match(Cond, m_Add(m_Value(Op0), m_ConstantInt(AddRHS)))) {
     // Change 'switch (X+4) case 1:' into 'switch (X) case -3'.
     for (auto Case : SI.cases()) {
       Constant *NewCase = ConstantExpr::getSub(Case.getCaseValue(), AddRHS);
       assert(isa<ConstantInt>(NewCase) &&
              "Result of expression should be constant");
       Case.setValue(cast<ConstantInt>(NewCase));
     }
-    SI.setCondition(Op0);
-    return &SI;
+    return replaceOperand(SI, 0, Op0);
   }
 
   KnownBits Known = computeKnownBits(Cond, 0, &SI);
   unsigned LeadingKnownZeros = Known.countMinLeadingZeros();
   unsigned LeadingKnownOnes = Known.countMinLeadingOnes();
 
   // Compute the number of leading bits we can ignore.
   // TODO: A better way to determine this would use ComputeNumSignBits().
Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
   // But do not shrink to a non-standard type, because backend can't generate 
   // good code for that yet.
   // TODO: We can make it aggressive again after fixing PR39569.
   if (NewWidth > 0 && NewWidth < Known.getBitWidth() &&
       shouldChangeType(Known.getBitWidth(), NewWidth)) {
     IntegerType *Ty = IntegerType::get(SI.getContext(), NewWidth);
     Builder.SetInsertPoint(&SI);
     Value *NewCond = Builder.CreateTrunc(Cond, Ty, "trunc");
-    SI.setCondition(NewCond);
 
     for (auto Case : SI.cases()) {
       APInt TruncatedCase = Case.getCaseValue()->getValue().trunc(NewWidth);
       Case.setValue(ConstantInt::get(SI.getContext(), TruncatedCase));
     }
-    return &SI;
+    return replaceOperand(SI, 0, NewCond);
   }
 
   return nullptr;
 }
 
 Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) {
   Value *Agg = EV.getAggregateOperand();