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[BasicAA] Unify struct/other offset (NFC) 

The distinction between StructOffset and OtherOffset has been
originally introduced by 82069c44ca,
which applied different reasoning to both offset kinds. However,
this distinction was not actually correct, and has been fixed by
c84e77aeae. Since then, we only ever
consider the sum StructOffset + OtherOffset, so we may as well
store it in that form directly.
This commit is contained in:
Nikita Popov 2020-11-07 18:29:47 +01:00
parent 330398052d
commit 4b860240a6
2 changed files with 12 additions and 26 deletions
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7
llvm/include/llvm/Analysis/BasicAliasAnalysis.h
View File

@ -135,11 +135,8 @@ private:
struct DecomposedGEP {
// Base pointer of the GEP
const Value *Base;
// Total constant offset w.r.t the base from indexing into structs
APInt StructOffset;
// Total constant offset w.r.t the base from indexing through
// pointers/arrays/vectors
APInt OtherOffset;
// Total constant offset from base.
APInt Offset;
// Scaled variable (non-constant) indices.
SmallVector<VariableGEPIndex, 4> VarIndices;
// Is GEP index scale compile-time constant.

31
llvm/lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -504,8 +504,7 @@ bool BasicAAResult::DecomposeGEPExpression(const Value *V,
if (FieldNo == 0)
continue;
Decomposed.StructOffset +=
DL.getStructLayout(STy)->getElementOffset(FieldNo);
Decomposed.Offset += DL.getStructLayout(STy)->getElementOffset(FieldNo);
continue;
}
@ -513,7 +512,7 @@ bool BasicAAResult::DecomposeGEPExpression(const Value *V,
if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Index)) {
if (CIdx->isZero())
continue;
Decomposed.OtherOffset +=
Decomposed.Offset +=
(DL.getTypeAllocSize(GTI.getIndexedType()).getFixedSize() *
CIdx->getValue().sextOrSelf(MaxPointerSize))
.sextOrTrunc(MaxPointerSize);
@ -561,7 +560,7 @@ bool BasicAAResult::DecomposeGEPExpression(const Value *V,
if (PointerSize > Width)
SExtBits += PointerSize - Width;
} else {
Decomposed.OtherOffset += ScaledOffset;
Decomposed.Offset += ScaledOffset;
Scale *= IndexScale.sextOrTrunc(MaxPointerSize);
}
@ -590,12 +589,8 @@ bool BasicAAResult::DecomposeGEPExpression(const Value *V,
}
// Take care of wrap-arounds
if (GepHasConstantOffset) {
Decomposed.StructOffset =
adjustToPointerSize(Decomposed.StructOffset, PointerSize);
Decomposed.OtherOffset =
adjustToPointerSize(Decomposed.OtherOffset, PointerSize);
}
if (GepHasConstantOffset)
Decomposed.Offset = adjustToPointerSize(Decomposed.Offset, PointerSize);
// Analyze the base pointer next.
V = GEPOp->getOperand(0);
@ -1237,9 +1232,6 @@ bool BasicAAResult::isGEPBaseAtNegativeOffset(const GEPOperator *GEPOp,
!DecompObject.VarIndices.empty())
return false;
APInt ObjectBaseOffset = DecompObject.StructOffset +
DecompObject.OtherOffset;
// If the GEP has no variable indices, we know the precise offset
// from the base, then use it. If the GEP has variable indices,
// we can't get exact GEP offset to identify pointer alias. So return
@ -1247,10 +1239,7 @@ bool BasicAAResult::isGEPBaseAtNegativeOffset(const GEPOperator *GEPOp,
if (!DecompGEP.VarIndices.empty())
return false;
APInt GEPBaseOffset = DecompGEP.StructOffset;
GEPBaseOffset += DecompGEP.OtherOffset;
return GEPBaseOffset.sge(ObjectBaseOffset + (int64_t)ObjectAccessSize);
return DecompGEP.Offset.sge(DecompObject.Offset + (int64_t)ObjectAccessSize);
}
/// Provides a bunch of ad-hoc rules to disambiguate a GEP instruction against
@ -1265,8 +1254,8 @@ AliasResult BasicAAResult::aliasGEP(
const Value *UnderlyingV1, const Value *UnderlyingV2, AAQueryInfo &AAQI) {
DecomposedGEP DecompGEP1, DecompGEP2;
unsigned MaxPointerSize = getMaxPointerSize(DL);
DecompGEP1.StructOffset = DecompGEP1.OtherOffset = APInt(MaxPointerSize, 0);
DecompGEP2.StructOffset = DecompGEP2.OtherOffset = APInt(MaxPointerSize, 0);
DecompGEP1.Offset = APInt(MaxPointerSize, 0);
DecompGEP2.Offset = APInt(MaxPointerSize, 0);
DecompGEP1.HasCompileTimeConstantScale =
DecompGEP2.HasCompileTimeConstantScale = true;
@ -1281,8 +1270,8 @@ AliasResult BasicAAResult::aliasGEP(
!DecompGEP2.HasCompileTimeConstantScale)
return MayAlias;
APInt GEP1BaseOffset = DecompGEP1.StructOffset + DecompGEP1.OtherOffset;
APInt GEP2BaseOffset = DecompGEP2.StructOffset + DecompGEP2.OtherOffset;
APInt GEP1BaseOffset = DecompGEP1.Offset;
APInt GEP2BaseOffset = DecompGEP2.Offset;
assert(DecompGEP1.Base == UnderlyingV1 && DecompGEP2.Base == UnderlyingV2 &&
"DecomposeGEPExpression returned a result different from "