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Pull some code out into a function, give it the ability to see through +.

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This allows us to turn code like malloc(4*x+4) -> malloc int, (x+1)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24081 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-10-29 04:36:15 +00:00
parent 274ecfb782
commit cfd65100c4
1 changed files with 59 additions and 24 deletions
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83
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -3770,6 +3770,53 @@ Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
return CI;
}
/// DecomposeSimpleLinearExpr - Analyze 'Val', seeing if it is a simple linear
/// expression. If so, decompose it, returning some value X, such that Val is
/// X*Scale+Offset.
///
static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale,
unsigned &Offset) {
assert(Val->getType() == Type::UIntTy && "Unexpected allocation size type!");
if (ConstantUInt *CI = dyn_cast<ConstantUInt>(Val)) {
Offset = CI->getValue();
Scale = 1;
return ConstantUInt::get(Type::UIntTy, 0);
} else if (Instruction *I = dyn_cast<Instruction>(Val)) {
if (I->getNumOperands() == 2) {
if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(I->getOperand(1))) {
if (I->getOpcode() == Instruction::Shl) {
// This is a value scaled by '1 << the shift amt'.
Scale = 1U << CUI->getValue();
Offset = 0;
return I->getOperand(0);
} else if (I->getOpcode() == Instruction::Mul) {
// This value is scaled by 'CUI'.
Scale = CUI->getValue();
Offset = 0;
return I->getOperand(0);
} else if (I->getOpcode() == Instruction::Add) {
// We have X+C. Check to see if we really have (X*C2)+C1, where C1 is
// divisible by C2.
unsigned SubScale;
Value *SubVal = DecomposeSimpleLinearExpr(I->getOperand(0), SubScale,
Offset);
Offset += CUI->getValue();
if (SubScale > 1 && (Offset % SubScale == 0)) {
Scale = SubScale;
return SubVal;
}
}
}
}
}
// Otherwise, we can't look past this.
Scale = 1;
Offset = 0;
return Val;
}
/// PromoteCastOfAllocation - If we find a cast of an allocation instruction,
/// try to eliminate the cast by moving the type information into the alloc.
Instruction *InstCombiner::PromoteCastOfAllocation(CastInst &CI,
@ -3816,32 +3863,14 @@ Instruction *InstCombiner::PromoteCastOfAllocation(CastInst &CI,
// See if we can satisfy the modulus by pulling a scale out of the array
// size argument.
unsigned ArraySizeScale = 1;
Value *NumElements = AI.getOperand(0);
if (ConstantUInt *CI = dyn_cast<ConstantUInt>(NumElements)) {
ArraySizeScale = CI->getValue();
NumElements = ConstantUInt::get(Type::UIntTy, 1);
} else if (ShiftInst *SI = dyn_cast<ShiftInst>(NumElements)) {
if (SI->getOpcode() == Instruction::Shl)
if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(SI->getOperand(1))) {
// This is a value scaled by '1 << the shift amt'.
NumElements = SI->getOperand(0);
ArraySizeScale = 1U << CUI->getValue();
}
} else if (isa<Instruction>(NumElements) &&
cast<Instruction>(NumElements)->getOpcode() == Instruction::Mul){
BinaryOperator *BO = cast<BinaryOperator>(NumElements);
if (ConstantUInt *Scale = dyn_cast<ConstantUInt>(BO->getOperand(1))) {
// This value is scaled by 'Scale'.
NumElements = BO->getOperand(0);
ArraySizeScale = Scale->getValue();
}
}
unsigned ArraySizeScale, ArrayOffset;
Value *NumElements = // See if the array size is a decomposable linear expr.
DecomposeSimpleLinearExpr(AI.getOperand(0), ArraySizeScale, ArrayOffset);
// If we can now satisfy the modulus, by using a non-1 scale, we really can
// do the xform.
if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0) return 0;
if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0 ||
(AllocElTySize*ArrayOffset ) % CastElTySize != 0) return 0;
unsigned Scale = (AllocElTySize*ArraySizeScale)/CastElTySize;
Value *Amt = 0;
@ -3857,6 +3886,12 @@ Instruction *InstCombiner::PromoteCastOfAllocation(CastInst &CI,
}
}
if (unsigned Offset = (AllocElTySize*ArrayOffset)/CastElTySize) {
Value *Off = ConstantUInt::get(Type::UIntTy, Offset);
Instruction *Tmp = BinaryOperator::createAdd(Amt, Off, "tmp");
Amt = InsertNewInstBefore(Tmp, AI);
}
std::string Name = AI.getName(); AI.setName("");
AllocationInst *New;
if (isa<MallocInst>(AI))