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Implement Transforms/InstCombine/cast.ll:test13, a case which occurs in a

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hot 164.gzip loop.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11702 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-02-22 05:25:17 +00:00
parent 0ca4418b95
commit c6bd195336
2 changed files with 35 additions and 4 deletions
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36
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -2004,9 +2004,14 @@ Instruction *InstCombiner::visitPHINode(PHINode &PN) {
Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// Is it 'getelementptr %P, long 0' or 'getelementptr %P'
// If so, eliminate the noop.
if ((GEP.getNumOperands() == 2 &&
GEP.getOperand(1) == Constant::getNullValue(Type::LongTy)) ||
GEP.getNumOperands() == 1)
if (GEP.getNumOperands() == 1)
return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
bool HasZeroPointerIndex = false;
if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
HasZeroPointerIndex = C->isNullValue();
if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
// Combine Indices - If the source pointer to this getelementptr instruction
@ -2073,6 +2078,31 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// Replace all uses of the GEP with the new constexpr...
return ReplaceInstUsesWith(GEP, CE);
}
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
if (CE->getOpcode() == Instruction::Cast) {
if (HasZeroPointerIndex) {
// transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
// into : GEP [10 x ubyte]* X, long 0, ...
//
// This occurs when the program declares an array extern like "int X[];"
//
Constant *X = CE->getOperand(0);
const PointerType *CPTy = cast<PointerType>(CE->getType());
if (const PointerType *XTy = dyn_cast<PointerType>(X->getType()))
if (const ArrayType *XATy =
dyn_cast<ArrayType>(XTy->getElementType()))
if (const ArrayType *CATy =
dyn_cast<ArrayType>(CPTy->getElementType()))
if (CATy->getElementType() == XATy->getElementType()) {
// At this point, we know that the cast source type is a pointer
// to an array of the same type as the destination pointer
// array. Because the array type is never stepped over (there
// is a leading zero) we can fold the cast into this GEP.
GEP.setOperand(0, X);
return &GEP;
}
}
}
}
return 0;

3
lib/Transforms/Scalar/TailDuplication.cpp
View File

@ -126,7 +126,8 @@ bool TailDup::canEliminateUnconditionalBranch(TerminatorInst *TI) {
// Basically, we refuse to make the transformation if any of the values
// computed in the 'tail' are used in any other basic blocks.
BasicBlock *Tail = TI->getSuccessor(0);
assert(isa<BranchInst>(TI) && cast<BranchInst>(TI)->isUnconditional());
for (BasicBlock::iterator I = Tail->begin(), E = Tail->end(); I != E; ++I)
for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
++UI) {