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Avoid doing conservative phi checks in aliasSameBasePointerGEPs() if no phis have been visited yet.

Browse Source 
Reviewers: Daniel Berlin

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D34478

llvm-svn: 307581
This commit is contained in:
Farhana Aleen 2017-07-10 20:15:40 +00:00
parent e1e88bbee8
commit d5bece9f2e
3 changed files with 18 additions and 8 deletions
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6
include/llvm/Analysis/BasicAliasAnalysis.h
View File

@ -183,6 +183,12 @@ private:
uint64_t V2Size, const AAMDNodes &V2AAInfo,
const Value *UnderlyingV1, const Value *UnderlyingV2);
AliasResult aliasSameBasePointerGEPs(const GEPOperator *GEP1,
uint64_t V1Size,
const GEPOperator *GEP2,
uint64_t V2Size,
const DataLayout &DL);
AliasResult aliasPHI(const PHINode *PN, uint64_t PNSize,
const AAMDNodes &PNAAInfo, const Value *V2,
uint64_t V2Size, const AAMDNodes &V2AAInfo,

18
lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -922,11 +922,11 @@ ModRefInfo BasicAAResult::getModRefInfo(ImmutableCallSite CS1,
/// Provide ad-hoc rules to disambiguate accesses through two GEP operators,
/// both having the exact same pointer operand.
static AliasResult aliasSameBasePointerGEPs(const GEPOperator *GEP1,
uint64_t V1Size,
const GEPOperator *GEP2,
uint64_t V2Size,
const DataLayout &DL) {
AliasResult BasicAAResult::aliasSameBasePointerGEPs(const GEPOperator *GEP1,
uint64_t V1Size,
const GEPOperator *GEP2,
uint64_t V2Size,
const DataLayout &DL) {
assert(GEP1->getPointerOperand()->stripPointerCastsAndBarriers() ==
GEP2->getPointerOperand()->stripPointerCastsAndBarriers() &&
@ -1006,7 +1006,7 @@ static AliasResult aliasSameBasePointerGEPs(const GEPOperator *GEP1,
// Because they cannot partially overlap and because fields in an array
// cannot overlap, if we can prove the final indices are different between
// GEP1 and GEP2, we can conclude GEP1 and GEP2 don't alias.
// If the last indices are constants, we've already checked they don't
// equal each other so we can exit early.
if (C1 && C2)
@ -1014,11 +1014,15 @@ static AliasResult aliasSameBasePointerGEPs(const GEPOperator *GEP1,
{
Value *GEP1LastIdx = GEP1->getOperand(GEP1->getNumOperands() - 1);
Value *GEP2LastIdx = GEP2->getOperand(GEP2->getNumOperands() - 1);
if (isa<PHINode>(GEP1LastIdx) || isa<PHINode>(GEP2LastIdx)) {
if ((isa<PHINode>(GEP1LastIdx) || isa<PHINode>(GEP2LastIdx)) &&
!VisitedPhiBBs.empty()) {
// If one of the indices is a PHI node, be safe and only use
// computeKnownBits so we don't make any assumptions about the
// relationships between the two indices. This is important if we're
// asking about values from different loop iterations. See PR32314.
// But, with empty visitedPhiBBs we can guarantee that the values are
// from the same iteration. Therefore, we can avoid doing this
// conservative check.
// TODO: We may be able to change the check so we only do this when
// we definitely looked through a PHINode.
if (GEP1LastIdx != GEP2LastIdx &&

2
lib/Analysis/ValueTracking.cpp
View File

@ -1873,7 +1873,7 @@ bool isKnownNonZero(const Value *V, unsigned Depth, const Query &Q) {
if (Known.countMaxLeadingZeros() < BitWidth - ShiftVal)
return true;
// Are all the bits to be shifted out known zero?
if (Known.countMinTrailingZeros() >= ShiftVal)
if (Known.isUnknown() || Known.countMinTrailingZeros() >= ShiftVal)
return isKnownNonZero(X, Depth, Q);
}
}