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factor some instcombine simplifications for getelementptr out to a new

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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
This commit is contained in:
Chris Lattner 2009-11-27 00:29:05 +00:00
parent 304076268a
commit c514c1f521
3 changed files with 46 additions and 10 deletions
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5
include/llvm/Analysis/InstructionSimplify.h
View File

@ -42,6 +42,11 @@ namespace llvm {
const TargetData *TD = 0);
/// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can
/// fold the result. If not, this returns null.
Value *SimplifyGEPInst(Value * const *Ops, unsigned NumOps,
const TargetData *TD = 0);
//=== Helper functions for higher up the class hierarchy.

32
lib/Analysis/InstructionSimplify.cpp
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@ -264,6 +264,34 @@ Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
return 0;
}
/// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can
/// fold the result. If not, this returns null.
Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps,
const TargetData *TD) {
// getelementptr P -> P.
if (NumOps == 1)
return Ops[0];
// TODO.
//if (isa<UndefValue>(Ops[0]))
// return UndefValue::get(GEP.getType());
// getelementptr P, 0 -> P.
if (NumOps == 2)
if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1]))
if (C->isZero())
return Ops[0];
// Check to see if this is constant foldable.
for (unsigned i = 0; i != NumOps; ++i)
if (!isa<Constant>(Ops[i]))
return 0;
return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]),
(Constant *const*)Ops+1, NumOps-1);
}
//=== Helper functions for higher up the class hierarchy.
/// SimplifyBinOp - Given operands for a BinaryOperator, see if we can
@ -309,6 +337,10 @@ Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD) {
case Instruction::FCmp:
return SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
I->getOperand(0), I->getOperand(1), TD);
case Instruction::GetElementPtr: {
SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
return SimplifyGEPInst(&Ops[0], Ops.size(), TD);
}
}
}

19
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -11429,21 +11429,16 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) {
}
Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end());
if (Value *V = SimplifyGEPInst(&Ops[0], Ops.size(), TD))
return ReplaceInstUsesWith(GEP, V);
Value *PtrOp = GEP.getOperand(0);
// Eliminate 'getelementptr %P, i32 0' and 'getelementptr %P', they are noops.
if (GEP.getNumOperands() == 1)
return ReplaceInstUsesWith(GEP, PtrOp);
if (isa<UndefValue>(GEP.getOperand(0)))
return ReplaceInstUsesWith(GEP, UndefValue::get(GEP.getType()));
bool HasZeroPointerIndex = false;
if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
HasZeroPointerIndex = C->isNullValue();
if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
return ReplaceInstUsesWith(GEP, PtrOp);
// Eliminate unneeded casts for indices.
if (TD) {
bool MadeChange = false;
@ -11548,6 +11543,10 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
return 0;
}
bool HasZeroPointerIndex = false;
if (ConstantInt *C = dyn_cast<ConstantInt>(GEP.getOperand(1)))
HasZeroPointerIndex = C->isZero();
// Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ...
// into : GEP [10 x i8]* X, i32 0, ...
//