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[InstCombine] Combine A->B->A BitCast
This patch enhances InstCombine to handle following case:
A -> B bitcast
PHI
B -> A bitcast
llvm-svn: 262670
This commit is contained in:
Guozhi Wei
parent
57f709ace4
commit
a7fc8e012e
@ -12,6 +12,7 @@
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//===----------------------------------------------------------------------===//
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#include "InstCombineInternal.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/Analysis/ConstantFolding.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/PatternMatch.h"
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@ -1786,6 +1787,103 @@ static Instruction *canonicalizeBitCastExtElt(BitCastInst &BitCast,
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return ExtractElementInst::Create(NewBC, ExtElt->getIndexOperand());
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}
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/// This function handles following case
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///
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/// A -> B cast
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/// PHI
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/// B -> A cast
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///
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/// All the related PHI nodes can be replaced by new PHI nodes with type A.
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/// The uses of \p CI can be changed to the new PHI node corresponding to \p PN.
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Instruction *InstCombiner::optimizeBitCastFromPhi(CastInst &CI, PHINode *PN) {
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Value *Src = CI.getOperand(0);
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Type *SrcTy = Src->getType(); // Type B
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Type *DestTy = CI.getType(); // Type A
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SmallVector<PHINode *, 4> Worklist;
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SmallSetVector<PHINode *, 4> OldPhiNodes;
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// Find all of the A->B casts and PHI nodes.
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// We need to inpect all related PHI nodes, but PHIs can be cyclic, so
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// OldPhiNodes is used to track all known PHI nodes, before adding a new
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// PHI to Worklist, it is checked against and added to OldPhiNodes first.
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Worklist.push_back(PN);
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OldPhiNodes.insert(PN);
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while (!Worklist.empty()) {
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auto *OldPN = Worklist.pop_back_val();
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for (Value *IncValue : OldPN->incoming_values()) {
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if (isa<Constant>(IncValue))
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continue;
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if (isa<LoadInst>(IncValue)) {
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if (IncValue->hasOneUse())
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continue;
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// If a LoadInst has more than one use, changing the type of loaded
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// value may create another bitcast.
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return nullptr;
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}
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auto *PNode = dyn_cast<PHINode>(IncValue);
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if (PNode) {
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if (OldPhiNodes.insert(PNode))
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Worklist.push_back(PNode);
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continue;
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}
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auto *BCI = dyn_cast<BitCastInst>(IncValue);
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// We can't handle other instructions.
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if (!BCI)
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return nullptr;
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// Verify it's a A->B cast.
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Type *TyA = BCI->getOperand(0)->getType();
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Type *TyB = BCI->getType();
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if (TyA != DestTy || TyB != SrcTy)
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return nullptr;
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}
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}
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// For each old PHI node, create a corresponding new PHI node with a type A.
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SmallDenseMap<PHINode *, PHINode *> NewPNodes;
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for (auto *OldPN : OldPhiNodes) {
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Builder->SetInsertPoint(OldPN);
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PHINode *NewPN = Builder->CreatePHI(DestTy, OldPN->getNumOperands());
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NewPNodes[OldPN] = NewPN;
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}
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// Fill in the operands of new PHI nodes.
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for (auto *OldPN : OldPhiNodes) {
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PHINode *NewPN = NewPNodes[OldPN];
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for (unsigned j = 0, e = OldPN->getNumOperands(); j != e; ++j) {
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Value *V = OldPN->getOperand(j);
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Value *NewV = nullptr;
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if (auto *C = dyn_cast<Constant>(V)) {
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NewV = Builder->CreateBitCast(C, DestTy);
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} else if (auto *LI = dyn_cast<LoadInst>(V)) {
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Builder->SetInsertPoint(OldPN->getIncomingBlock(j)->getTerminator());
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NewV = Builder->CreateBitCast(LI, DestTy);
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} else if (auto *BCI = dyn_cast<BitCastInst>(V)) {
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NewV = BCI->getOperand(0);
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} else if (auto *PrevPN = dyn_cast<PHINode>(V)) {
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NewV = NewPNodes[PrevPN];
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}
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assert(NewV);
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NewPN->addIncoming(NewV, OldPN->getIncomingBlock(j));
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}
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}
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// If there is a store with type B, change it to type A.
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for (User *U : PN->users()) {
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auto *SI = dyn_cast<StoreInst>(U);
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if (SI && SI->getOperand(0) == PN) {
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Builder->SetInsertPoint(SI);
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SI->setOperand(0, Builder->CreateBitCast(NewPNodes[PN], SrcTy));
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}
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}
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return replaceInstUsesWith(CI, NewPNodes[PN]);
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}
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Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
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// If the operands are integer typed then apply the integer transforms,
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// otherwise just apply the common ones.
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@ -1902,6 +2000,11 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
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}
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}
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// Handle the A->B->A cast, and there is an intervening PHI node.
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if (PHINode *PN = dyn_cast<PHINode>(Src))
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if (Instruction *I = optimizeBitCastFromPhi(CI, PN))
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return I;
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if (Instruction *I = canonicalizeBitCastExtElt(CI, *this, DL))
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return I;
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@ -391,6 +391,7 @@ private:
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Instruction *scalarizePHI(ExtractElementInst &EI, PHINode *PN);
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Value *EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask);
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Instruction *foldCastedBitwiseLogic(BinaryOperator &I);
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Instruction *optimizeBitCastFromPhi(CastInst &CI, PHINode *PN);
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public:
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/// \brief Inserts an instruction \p New before instruction \p Old
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93
test/Transforms/InstCombine/pr25342.ll
Normal file
93
test/Transforms/InstCombine/pr25342.ll
Normal file
@ -0,0 +1,93 @@
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; RUN: opt < %s -instcombine -S | FileCheck %s
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%"struct.std::complex" = type { { float, float } }
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@dd = external global %"struct.std::complex", align 4
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@dd2 = external global %"struct.std::complex", align 4
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define void @_Z3fooi(i32 signext %n) {
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entry:
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br label %for.cond
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for.cond:
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%ldd.sroa.0.0 = phi i32 [ 0, %entry ], [ %5, %for.body ]
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%ldd.sroa.6.0 = phi i32 [ 0, %entry ], [ %7, %for.body ]
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%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
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%cmp = icmp slt i32 %i.0, %n
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br i1 %cmp, label %for.body, label %for.end
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for.body:
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%0 = load float, float* getelementptr inbounds (%"struct.std::complex", %"struct.std::complex"* @dd, i64 0, i32 0, i32 0), align 4
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%1 = load float, float* getelementptr inbounds (%"struct.std::complex", %"struct.std::complex"* @dd, i64 0, i32 0, i32 1), align 4
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%2 = load float, float* getelementptr inbounds (%"struct.std::complex", %"struct.std::complex"* @dd2, i64 0, i32 0, i32 0), align 4
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%3 = load float, float* getelementptr inbounds (%"struct.std::complex", %"struct.std::complex"* @dd2, i64 0, i32 0, i32 1), align 4
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%mul.i = fmul float %0, %2
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%mul4.i = fmul float %1, %3
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%sub.i = fsub float %mul.i, %mul4.i
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%mul5.i = fmul float %1, %2
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%mul6.i = fmul float %0, %3
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%add.i4 = fadd float %mul5.i, %mul6.i
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%4 = bitcast i32 %ldd.sroa.0.0 to float
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%add.i = fadd float %sub.i, %4
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%5 = bitcast float %add.i to i32
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%6 = bitcast i32 %ldd.sroa.6.0 to float
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%add4.i = fadd float %add.i4, %6
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%7 = bitcast float %add4.i to i32
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%inc = add nsw i32 %i.0, 1
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br label %for.cond
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for.end:
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store i32 %ldd.sroa.0.0, i32* bitcast (%"struct.std::complex"* @dd to i32*), align 4
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store i32 %ldd.sroa.6.0, i32* bitcast (float* getelementptr inbounds (%"struct.std::complex", %"struct.std::complex"* @dd, i64 0, i32 0, i32 1) to i32*), align 4
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ret void
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; CHECK: phi float
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; CHECK: store float
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; CHECK-NOT: bitcast
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}
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define void @multi_phi(i32 signext %n) {
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entry:
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br label %for.cond
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for.cond:
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%ldd.sroa.0.0 = phi i32 [ 0, %entry ], [ %9, %odd.bb ]
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%i.0 = phi i32 [ 0, %entry ], [ %inc, %odd.bb ]
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%cmp = icmp slt i32 %i.0, %n
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br i1 %cmp, label %for.body, label %for.end
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for.body:
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%0 = load float, float* getelementptr inbounds (%"struct.std::complex", %"struct.std::complex"* @dd, i64 0, i32 0, i32 0), align 4
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%1 = load float, float* getelementptr inbounds (%"struct.std::complex", %"struct.std::complex"* @dd, i64 0, i32 0, i32 1), align 4
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%2 = load float, float* getelementptr inbounds (%"struct.std::complex", %"struct.std::complex"* @dd2, i64 0, i32 0, i32 0), align 4
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%3 = load float, float* getelementptr inbounds (%"struct.std::complex", %"struct.std::complex"* @dd2, i64 0, i32 0, i32 1), align 4
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%mul.i = fmul float %0, %2
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%mul4.i = fmul float %1, %3
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%sub.i = fsub float %mul.i, %mul4.i
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%4 = bitcast i32 %ldd.sroa.0.0 to float
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%add.i = fadd float %sub.i, %4
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%5 = bitcast float %add.i to i32
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%inc = add nsw i32 %i.0, 1
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%bit0 = and i32 %inc, 1
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%even = icmp slt i32 %bit0, 1
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br i1 %even, label %even.bb, label %odd.bb
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even.bb:
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%6 = bitcast i32 %5 to float
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%7 = fadd float %sub.i, %6
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%8 = bitcast float %7 to i32
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br label %odd.bb
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odd.bb:
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%9 = phi i32 [ %5, %for.body ], [ %8, %even.bb ]
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br label %for.cond
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for.end:
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store i32 %ldd.sroa.0.0, i32* bitcast (%"struct.std::complex"* @dd to i32*), align 4
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ret void
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; CHECK-LABEL: @multi_phi(
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; CHECK: phi float
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; CHECK: store float
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; CHECK-NOT: bitcast
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}
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