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[BasicAA] Remove some intermediate variables (NFC)

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Use DecompGEP1.Offset instead of GEP1BaseOffset, etc. I found the
asymmetry of modifying DecompGEP1.VarIndices, but not modifying
DecompGEP1.Offset odd here.
This commit is contained in:
Nikita Popov 2020-11-21 20:29:28 +01:00
parent ff18300427
commit 753e4ece6c
1 changed files with 18 additions and 21 deletions
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39
lib/Analysis/BasicAliasAnalysis.cpp
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@ -1233,9 +1233,6 @@ AliasResult BasicAAResult::aliasGEP(
!DecompGEP2.HasCompileTimeConstantScale)
return MayAlias;
APInt GEP1BaseOffset = DecompGEP1.Offset;
APInt GEP2BaseOffset = DecompGEP2.Offset;
assert(DecompGEP1.Base == UnderlyingV1 && DecompGEP2.Base == UnderlyingV2 &&
"DecomposeGEPExpression returned a result different from "
"getUnderlyingObject");
@ -1260,7 +1257,7 @@ AliasResult BasicAAResult::aliasGEP(
// For GEPs with identical offsets, we can preserve the size and AAInfo
// when performing the alias check on the underlying objects.
if (BaseAlias == MayAlias && GEP1BaseOffset == GEP2BaseOffset &&
if (BaseAlias == MayAlias && DecompGEP1.Offset == DecompGEP2.Offset &&
DecompGEP1.VarIndices == DecompGEP2.VarIndices) {
AliasResult PreciseBaseAlias = aliasCheck(
UnderlyingV1, V1Size, V1AAInfo, UnderlyingV2, V2Size, V2AAInfo, AAQI);
@ -1292,7 +1289,7 @@ AliasResult BasicAAResult::aliasGEP(
// Subtract the GEP2 pointer from the GEP1 pointer to find out their
// symbolic difference.
GEP1BaseOffset -= GEP2BaseOffset;
DecompGEP1.Offset -= DecompGEP2.Offset;
GetIndexDifference(DecompGEP1.VarIndices, DecompGEP2.VarIndices);
} else {
@ -1324,17 +1321,17 @@ AliasResult BasicAAResult::aliasGEP(
//
// In the other case, if we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2
// must aliases the GEP, the end result is a must alias also.
if (GEP1BaseOffset == 0 && DecompGEP1.VarIndices.empty())
if (DecompGEP1.Offset == 0 && DecompGEP1.VarIndices.empty())
return MustAlias;
// If there is a constant difference between the pointers, but the difference
// is less than the size of the associated memory object, then we know
// that the objects are partially overlapping. If the difference is
// greater, we know they do not overlap.
if (GEP1BaseOffset != 0 && DecompGEP1.VarIndices.empty()) {
if (GEP1BaseOffset.sge(0)) {
if (DecompGEP1.Offset != 0 && DecompGEP1.VarIndices.empty()) {
if (DecompGEP1.Offset.sge(0)) {
if (V2Size.hasValue()) {
if (GEP1BaseOffset.ult(V2Size.getValue()))
if (DecompGEP1.Offset.ult(V2Size.getValue()))
return PartialAlias;
return NoAlias;
}
@ -1348,7 +1345,7 @@ AliasResult BasicAAResult::aliasGEP(
// We need to know that V2Size is not unknown, otherwise we might have
// stripped a gep with negative index ('gep <ptr>, -1, ...).
if (V1Size.hasValue() && V2Size.hasValue()) {
if ((-GEP1BaseOffset).ult(V1Size.getValue()))
if ((-DecompGEP1.Offset).ult(V1Size.getValue()))
return PartialAlias;
return NoAlias;
}
@ -1357,8 +1354,8 @@ AliasResult BasicAAResult::aliasGEP(
if (!DecompGEP1.VarIndices.empty()) {
APInt GCD;
bool AllNonNegative = GEP1BaseOffset.isNonNegative();
bool AllNonPositive = GEP1BaseOffset.isNonPositive();
bool AllNonNegative = DecompGEP1.Offset.isNonNegative();
bool AllNonPositive = DecompGEP1.Offset.isNonPositive();
for (unsigned i = 0, e = DecompGEP1.VarIndices.size(); i != e; ++i) {
const APInt &Scale = DecompGEP1.VarIndices[i].Scale;
if (i == 0)
@ -1391,12 +1388,12 @@ AliasResult BasicAAResult::aliasGEP(
}
// We now have accesses at two offsets from the same base:
// 1. (...)*GCD + GEP1BaseOffset with size V1Size
// 1. (...)*GCD + DecompGEP1.Offset with size V1Size
// 2. 0 with size V2Size
// Using arithmetic modulo GCD, the accesses are at
// [ModOffset..ModOffset+V1Size) and [0..V2Size). If the first access fits
// into the range [V2Size..GCD), then we know they cannot overlap.
APInt ModOffset = GEP1BaseOffset.srem(GCD);
APInt ModOffset = DecompGEP1.Offset.srem(GCD);
if (ModOffset.isNegative())
ModOffset += GCD; // We want mod, not rem.
if (V1Size.hasValue() && V2Size.hasValue() &&
@ -1405,22 +1402,22 @@ AliasResult BasicAAResult::aliasGEP(
return NoAlias;
// If we know all the variables are non-negative, then the total offset is
// also non-negative and >= GEP1BaseOffset. We have the following layout:
// also non-negative and >= DecompGEP1.Offset. We have the following layout:
// [0, V2Size) ... [TotalOffset, TotalOffer+V1Size]
// If GEP1BaseOffset >= V2Size, the accesses don't alias.
// If DecompGEP1.Offset >= V2Size, the accesses don't alias.
if (AllNonNegative && V2Size.hasValue() &&
GEP1BaseOffset.uge(V2Size.getValue()))
DecompGEP1.Offset.uge(V2Size.getValue()))
return NoAlias;
// Similarly, if the variables are non-positive, then the total offset is
// also non-positive and <= GEP1BaseOffset. We have the following layout:
// also non-positive and <= DecompGEP1.Offset. We have the following layout:
// [TotalOffset, TotalOffset+V1Size) ... [0, V2Size)
// If -GEP1BaseOffset >= V1Size, the accesses don't alias.
// If -DecompGEP1.Offset >= V1Size, the accesses don't alias.
if (AllNonPositive && V1Size.hasValue() &&
(-GEP1BaseOffset).uge(V1Size.getValue()))
(-DecompGEP1.Offset).uge(V1Size.getValue()))
return NoAlias;
if (constantOffsetHeuristic(DecompGEP1.VarIndices, V1Size, V2Size,
GEP1BaseOffset, &AC, DT))
DecompGEP1.Offset, &AC, DT))
return NoAlias;
}