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teach basicaa that A[i] != A[i+1].

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89951 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2009-11-26 16:18:10 +00:00
parent 61d2462400
commit f6ac4d9dad
3 changed files with 48 additions and 2 deletions
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32
lib/Analysis/BasicAliasAnalysis.cpp
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@ -378,6 +378,30 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS1, CallSite CS2) {
return NoAA::getModRefInfo(CS1, CS2);
}
/// GetLinearExpression - Analyze the specified value as a linear expression:
/// "A*V + B". Return the scale and offset values as APInts and return V as a
/// Value*. The incoming Value is known to be a scalar integer.
static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset) {
assert(isa<IntegerType>(V->getType()) && "Not an integer value");
if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(V)) {
if (ConstantInt *RHSC = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
switch (BOp->getOpcode()) {
default: break;
case Instruction::Add:
V = GetLinearExpression(BOp->getOperand(0), Scale, Offset);
Offset += RHSC->getValue();
return V;
// TODO: SHL, MUL, OR.
}
}
}
Scale = 1;
Offset = 0;
return V;
}
/// DecomposeGEPExpression - If V is a symbolic pointer expression, decompose it
/// into a base pointer with a constant offset and a number of scaled symbolic
/// offsets.
@ -456,6 +480,14 @@ static const Value *DecomposeGEPExpression(const Value *V, int64_t &BaseOffs,
// TODO: Could handle linear expressions here like A[X+1], also A[X*4|1].
uint64_t Scale = TD->getTypeAllocSize(*GTI);
unsigned Width = cast<IntegerType>(Index->getType())->getBitWidth();
APInt IndexScale(Width, 0), IndexOffset(Width, 0);
Index = GetLinearExpression(Index, IndexScale, IndexOffset);
Scale *= IndexScale.getZExtValue();
BaseOffs += IndexOffset.getZExtValue()*Scale;
// If we already had an occurrance of this index variable, merge this
// scale into it. For example, we want to handle:
// A[x][x] -> x*16 + x*4 -> x*20