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factor some instcombine simplifications for getelementptr out to a new
SimplifyGEPInst method in InstructionSimplify.h. No functionality change. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89980 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -42,6 +42,11 @@ namespace llvm {
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const TargetData *TD = 0);
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/// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can
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/// fold the result. If not, this returns null.
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Value *SimplifyGEPInst(Value * const *Ops, unsigned NumOps,
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const TargetData *TD = 0);
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//=== Helper functions for higher up the class hierarchy.
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@ -264,6 +264,34 @@ Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
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return 0;
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}
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/// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can
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/// fold the result. If not, this returns null.
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Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps,
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const TargetData *TD) {
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// getelementptr P -> P.
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if (NumOps == 1)
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return Ops[0];
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// TODO.
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//if (isa<UndefValue>(Ops[0]))
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// return UndefValue::get(GEP.getType());
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// getelementptr P, 0 -> P.
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if (NumOps == 2)
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if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1]))
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if (C->isZero())
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return Ops[0];
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// Check to see if this is constant foldable.
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for (unsigned i = 0; i != NumOps; ++i)
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if (!isa<Constant>(Ops[i]))
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return 0;
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return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]),
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(Constant *const*)Ops+1, NumOps-1);
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}
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//=== Helper functions for higher up the class hierarchy.
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/// SimplifyBinOp - Given operands for a BinaryOperator, see if we can
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@ -309,6 +337,10 @@ Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD) {
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case Instruction::FCmp:
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return SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
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I->getOperand(0), I->getOperand(1), TD);
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case Instruction::GetElementPtr: {
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SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
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return SimplifyGEPInst(&Ops[0], Ops.size(), TD);
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}
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}
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}
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@ -11429,21 +11429,16 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) {
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}
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Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
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SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end());
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if (Value *V = SimplifyGEPInst(&Ops[0], Ops.size(), TD))
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return ReplaceInstUsesWith(GEP, V);
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Value *PtrOp = GEP.getOperand(0);
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// Eliminate 'getelementptr %P, i32 0' and 'getelementptr %P', they are noops.
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if (GEP.getNumOperands() == 1)
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return ReplaceInstUsesWith(GEP, PtrOp);
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if (isa<UndefValue>(GEP.getOperand(0)))
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return ReplaceInstUsesWith(GEP, UndefValue::get(GEP.getType()));
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bool HasZeroPointerIndex = false;
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if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
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HasZeroPointerIndex = C->isNullValue();
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if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
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return ReplaceInstUsesWith(GEP, PtrOp);
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// Eliminate unneeded casts for indices.
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if (TD) {
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bool MadeChange = false;
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@ -11548,6 +11543,10 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
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return 0;
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}
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bool HasZeroPointerIndex = false;
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if (ConstantInt *C = dyn_cast<ConstantInt>(GEP.getOperand(1)))
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HasZeroPointerIndex = C->isZero();
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// Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ...
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// into : GEP [10 x i8]* X, i32 0, ...
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//
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