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When merging to alias sets, if they are both must alias, the result is not

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a must alias set unless all of the pointers in the resultant set are must
aliased together.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18275 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-11-27 18:37:42 +00:00
parent 276636c93b
commit cc8d524a24
1 changed files with 22 additions and 8 deletions
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30
lib/Analysis/AliasSetTracker.cpp
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@ -21,9 +21,9 @@
#include <iostream>
using namespace llvm;
/// mergeSetIn - Merge the specified alias set into this alias set...
/// mergeSetIn - Merge the specified alias set into this alias set.
///
void AliasSet::mergeSetIn(AliasSet &AS) {
void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) {
assert(!AS.Forward && "Alias set is already forwarding!");
assert(!Forward && "This set is a forwarding set!!");
@ -31,6 +31,20 @@ void AliasSet::mergeSetIn(AliasSet &AS) {
AccessTy |= AS.AccessTy;
AliasTy |= AS.AliasTy;
if (AliasTy == MustAlias) {
// Check that these two merged sets really are must aliases. Since both
// used to be must-alias sets, we can just check any pointer from each set
// for aliasing.
AliasAnalysis &AA = AST.getAliasAnalysis();
HashNodePair *L = getSomePointer();
HashNodePair *R = AS.getSomePointer();
// If the pointers are not a must-alias pair, this set becomes a may alias.
if (AA.alias(L->first, L->second.getSize(), R->first, R->second.getSize())
!= AliasAnalysis::MustAlias)
AliasTy = MayAlias;
}
if (CallSites.empty()) { // Merge call sites...
if (!AS.CallSites.empty())
std::swap(CallSites, AS.CallSites);
@ -179,10 +193,10 @@ AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr,
AliasSet *FoundSet = 0;
for (iterator I = begin(), E = end(); I != E; ++I)
if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) {
if (FoundSet == 0) { // If this is the first alias set ptr can go into...
if (FoundSet == 0) { // If this is the first alias set ptr can go into.
FoundSet = I; // Remember it.
} else { // Otherwise, we must merge the sets...
FoundSet->mergeSetIn(*I); // Merge in contents...
} else { // Otherwise, we must merge the sets.
FoundSet->mergeSetIn(*I, *this); // Merge in contents.
}
}
@ -205,10 +219,10 @@ AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) {
AliasSet *FoundSet = 0;
for (iterator I = begin(), E = end(); I != E; ++I)
if (!I->Forward && I->aliasesCallSite(CS, AA)) {
if (FoundSet == 0) { // If this is the first alias set ptr can go into...
if (FoundSet == 0) { // If this is the first alias set ptr can go into.
FoundSet = I; // Remember it.
} else if (!I->Forward) { // Otherwise, we must merge the sets...
FoundSet->mergeSetIn(*I); // Merge in contents...
} else if (!I->Forward) { // Otherwise, we must merge the sets.
FoundSet->mergeSetIn(*I, *this); // Merge in contents.
}
}