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Use ConstantRange to propagate information through value definitions.

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llvm-svn: 111425
This commit is contained in:
Owen Anderson 2010-08-18 21:11:37 +00:00
parent 2d5b6bad99
commit a57dfdac61
1 changed files with 83 additions and 4 deletions
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83
lib/Analysis/LazyValueInfo.cpp
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@ -503,15 +503,94 @@ LVILatticeVal LVIQuery::getBlockValue(BasicBlock *BB) {
// Return the merged value, which is more precise than 'overdefined'.
assert(!Result.isOverdefined());
return Cache[BB] = Result;
} else {
}
assert(Cache[BB].isOverdefined() && "Recursive query changed our cache?");
// We can only analyze the definitions of certain classes of instructions
// (integral binops and casts at the moment), so bail if this isn't one.
LVILatticeVal Result;
if ((!isa<BinaryOperator>(BBI) && !isa<CastInst>(BBI)) ||
!BBI->getType()->isIntegerTy()) {
DEBUG(dbgs() << " compute BB '" << BB->getName()
<< "' - overdefined because inst def found.\n");
Result.markOverdefined();
return Result;
}
// FIXME: We're currently limited to binops with a constant RHS. This should
// be improved.
BinaryOperator *BO = dyn_cast<BinaryOperator>(BBI);
if (BO && !isa<ConstantInt>(BO->getOperand(1))) {
DEBUG(dbgs() << " compute BB '" << BB->getName()
<< "' - overdefined because inst def found.\n");
Result.markOverdefined();
return Result;
}
// Figure out the range of the LHS. If that fails, bail.
LVILatticeVal LHSVal = Parent.getValueInBlock(BBI->getOperand(0), BB);
if (!LHSVal.isConstantRange()) {
Result.markOverdefined();
return Result;
}
ConstantInt *RHS = 0;
ConstantRange LHSRange = LHSVal.getConstantRange();
ConstantRange RHSRange(1);
const IntegerType *ResultTy = cast<IntegerType>(BBI->getType());
if (isa<BinaryOperator>(BBI)) {
RHS = cast<ConstantInt>(BBI->getOperand(1));
RHSRange = ConstantRange(RHS->getValue(), RHS->getValue()+1);
}
// NOTE: We're currently limited by the set of operations that ConstantRange
// can evaluate symbolically. Enhancing that set will allows us to analyze
// more definitions.
switch (BBI->getOpcode()) {
case Instruction::Add:
Result.markConstantRange(LHSRange.add(RHSRange));
break;
case Instruction::Sub:
Result.markConstantRange(LHSRange.sub(RHSRange));
break;
case Instruction::Mul:
Result.markConstantRange(LHSRange.multiply(RHSRange));
break;
case Instruction::UDiv:
Result.markConstantRange(LHSRange.udiv(RHSRange));
break;
case Instruction::Shl:
Result.markConstantRange(LHSRange.shl(RHSRange));
break;
case Instruction::LShr:
Result.markConstantRange(LHSRange.lshr(RHSRange));
break;
case Instruction::Trunc:
Result.markConstantRange(LHSRange.truncate(ResultTy->getBitWidth()));
break;
case Instruction::SExt:
Result.markConstantRange(LHSRange.signExtend(ResultTy->getBitWidth()));
break;
case Instruction::ZExt:
Result.markConstantRange(LHSRange.zeroExtend(ResultTy->getBitWidth()));
break;
case Instruction::BitCast:
Result.markConstantRange(LHSRange);
break;
// Unhandled instructions are overdefined.
default:
DEBUG(dbgs() << " compute BB '" << BB->getName()
<< "' - overdefined because inst def found.\n");
Result.markOverdefined();
break;
}
return Cache[BB] = Result;
}
/// getEdgeValue - This method attempts to infer more complex
LVILatticeVal LVIQuery::getEdgeValue(BasicBlock *BBFrom, BasicBlock *BBTo) {