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implement Transforms/InstCombine/cast2.ll:test3 and PR1263

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35341 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-03-25 20:43:09 +00:00
parent 7d4d6b8615
commit db9654e284
1 changed files with 21 additions and 1 deletions
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22
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -7896,10 +7896,22 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
return ReplaceInstUsesWith(GEP, PtrOp);
// Keep track of whether all indices are zero constants integers.
bool AllZeroIndices = true;
// Eliminate unneeded casts for indices.
bool MadeChange = false;
gep_type_iterator GTI = gep_type_begin(GEP);
for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i, ++GTI)
for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i, ++GTI) {
// Track whether this GEP has all zero indices, if so, it doesn't move the
// input pointer, it just changes its type.
if (AllZeroIndices) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP.getOperand(i)))
AllZeroIndices = CI->isNullValue();
else
AllZeroIndices = false;
}
if (isa<SequentialType>(*GTI)) {
if (CastInst *CI = dyn_cast<CastInst>(GEP.getOperand(i))) {
if (CI->getOpcode() == Instruction::ZExt ||
@ -7929,8 +7941,16 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
MadeChange = true;
}
}
}
if (MadeChange) return &GEP;
// If this GEP instruction doesn't move the pointer, and if the input operand
// is a bitcast of another pointer, just replace the GEP with a bitcast of the
// real input to the dest type.
if (AllZeroIndices && isa<BitCastInst>(GEP.getOperand(0)))
return new BitCastInst(cast<BitCastInst>(GEP.getOperand(0))->getOperand(0),
GEP.getType());
// Combine Indices - If the source pointer to this getelementptr instruction
// is a getelementptr instruction, combine the indices of the two
// getelementptr instructions into a single instruction.