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[BasicAA] Extract linear expression multiplication (NFC) 

Extract a common method for multiplying a linear expression by a
factor.
This commit is contained in:
Nikita Popov 2021-10-29 22:40:16 +02:00
parent a43d1aa852
commit cdf45f98ca
1 changed files with 14 additions and 13 deletions
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27
llvm/lib/Analysis/BasicAliasAnalysis.cpp
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@ -358,6 +358,11 @@ struct LinearExpression {
Scale = APInt(BitWidth, 1); Scale = APInt(BitWidth, 1);
Offset = APInt(BitWidth, 0); Offset = APInt(BitWidth, 0);
} }
LinearExpression mul(const APInt &Other, bool MulIsNSW) const {
return LinearExpression(Val, Scale * Other, Offset * Other,
IsNSW && (Other.isOne() || MulIsNSW));
}
}; };
} }
@ -420,14 +425,11 @@ static LinearExpression GetLinearExpression(
E.IsNSW &= NSW; E.IsNSW &= NSW;
break; break;
} }
case Instruction::Mul: { case Instruction::Mul:
E = GetLinearExpression(Val.withValue(BOp->getOperand(0)), DL, E = GetLinearExpression(Val.withValue(BOp->getOperand(0)), DL,
Depth + 1, AC, DT); Depth + 1, AC, DT)
E.Offset *= RHS; .mul(RHS, NSW);
E.Scale *= RHS;
E.IsNSW &= NSW;
break; break;
}
case Instruction::Shl: case Instruction::Shl:
// We're trying to linearize an expression of the kind: // We're trying to linearize an expression of the kind:
// shl i8 -128, 36 // shl i8 -128, 36
@ -645,8 +647,6 @@ BasicAAResult::DecomposeGEPExpression(const Value *V, const DataLayout &DL,
GepHasConstantOffset = false; GepHasConstantOffset = false;
APInt Scale(MaxPointerSize,
DL.getTypeAllocSize(GTI.getIndexedType()).getFixedSize());
// If the integer type is smaller than the pointer size, it is implicitly // If the integer type is smaller than the pointer size, it is implicitly
// sign extended to pointer size. // sign extended to pointer size.
unsigned Width = Index->getType()->getIntegerBitWidth(); unsigned Width = Index->getType()->getIntegerBitWidth();
@ -655,11 +655,12 @@ BasicAAResult::DecomposeGEPExpression(const Value *V, const DataLayout &DL,
LinearExpression LE = GetLinearExpression( LinearExpression LE = GetLinearExpression(
CastedValue(Index, 0, SExtBits, TruncBits), DL, 0, AC, DT); CastedValue(Index, 0, SExtBits, TruncBits), DL, 0, AC, DT);
// The GEP index scale ("Scale") scales C1*V+C2, yielding (C1*V+C2)*Scale. // Scale by the type size.
// This gives us an aggregate computation of (C1*Scale)*V + C2*Scale. unsigned TypeSize =
LE.IsNSW &= GEPOp->isInBounds() || Scale.isOne(); DL.getTypeAllocSize(GTI.getIndexedType()).getFixedSize();
Decomposed.Offset += LE.Offset.sextOrTrunc(MaxPointerSize) * Scale; LE = LE.mul(APInt(PointerSize, TypeSize), GEPOp->isInBounds());
Scale *= LE.Scale.sextOrTrunc(MaxPointerSize); Decomposed.Offset += LE.Offset.sextOrSelf(MaxPointerSize);
APInt Scale = LE.Scale.sextOrSelf(MaxPointerSize);
// If we already had an occurrence of this index variable, merge this // If we already had an occurrence of this index variable, merge this
// scale into it. For example, we want to handle: // scale into it. For example, we want to handle: