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| author | Dan Gohman <gohman@apple.com> | 2009-11-09 19:29:11 +0000 |
|---|---|---|
| committer | Dan Gohman <gohman@apple.com> | 2009-11-09 19:29:11 +0000 |
| commit | ccb4584eddd133ff90fc0e19929c8ce4089a33ae (patch) | |
| tree | d8871bec5abdc9646dec5704d087c5f7cc9be5b0 /llvm/lib/Analysis/BasicAliasAnalysis.cpp | |
| parent | 1bc688dc6029ffc6975378d95f6f6d95051b1c11 (diff) | |
| download | bcm5719-llvm-ccb4584eddd133ff90fc0e19929c8ce4089a33ae.tar.gz bcm5719-llvm-ccb4584eddd133ff90fc0e19929c8ce4089a33ae.zip | |
Default-addressspace null pointers don't alias anything. This allows
GVN to be more aggressive. Patch by Hans Wennborg! (with a comment added by me)
llvm-svn: 86582
Diffstat (limited to 'llvm/lib/Analysis/BasicAliasAnalysis.cpp')
| -rw-r--r-- | llvm/lib/Analysis/BasicAliasAnalysis.cpp | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp index 2f4663531ae..ea10a830547 100644 --- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp +++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp @@ -646,6 +646,15 @@ BasicAliasAnalysis::aliasCheck(const Value *V1, unsigned V1Size, const Value *O1 = V1->getUnderlyingObject(); const Value *O2 = V2->getUnderlyingObject(); + // Null values in the default address space don't point to any object, so they + // don't alias any other pointer. + if (const ConstantPointerNull *CPN = dyn_cast<ConstantPointerNull>(O1)) + if (CPN->getType()->getAddressSpace() == 0) + return NoAlias; + if (const ConstantPointerNull *CPN = dyn_cast<ConstantPointerNull>(O2)) + if (CPN->getType()->getAddressSpace() == 0) + return NoAlias; + if (O1 != O2) { // If V1/V2 point to two different objects we know that we have no alias. if (isIdentifiedObject(O1) && isIdentifiedObject(O2)) |
