diff options
| -rw-r--r-- | lib/Analysis/BasicAliasAnalysis.cpp | 69 |
1 files changed, 49 insertions, 20 deletions
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp index 875530d..3ab2744 100644 --- a/lib/Analysis/BasicAliasAnalysis.cpp +++ b/lib/Analysis/BasicAliasAnalysis.cpp @@ -265,28 +265,57 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size, const Value *O2 = getUnderlyingObject(V2); // Pointing at a discernible object? - if (O1 && O2) { - if (isa<Argument>(O1)) { - // Incoming argument cannot alias locally allocated object! - if (isa<AllocationInst>(O2)) return NoAlias; - // Otherwise, nothing is known... - } else if (isa<Argument>(O2)) { - // Incoming argument cannot alias locally allocated object! - if (isa<AllocationInst>(O1)) return NoAlias; - // Otherwise, nothing is known... - } else { - // If they are two different objects, we know that we have no alias... - if (O1 != O2) return NoAlias; + if (O1) { + if (O2) { + if (isa<Argument>(O1)) { + // Incoming argument cannot alias locally allocated object! + if (isa<AllocationInst>(O2)) return NoAlias; + // Otherwise, nothing is known... + } else if (isa<Argument>(O2)) { + // Incoming argument cannot alias locally allocated object! + if (isa<AllocationInst>(O1)) return NoAlias; + // Otherwise, nothing is known... + } else if (O1 != O2) { + // If they are two different objects, we know that we have no alias... + return NoAlias; + } + + // If they are the same object, they we can look at the indexes. If they + // index off of the object is the same for both pointers, they must alias. + // If they are provably different, they must not alias. Otherwise, we + // can't tell anything. } - // If they are the same object, they we can look at the indexes. If they - // index off of the object is the same for both pointers, they must alias. - // If they are provably different, they must not alias. Otherwise, we can't - // tell anything. - } else if (O1 && !isa<Argument>(O1) && isa<ConstantPointerNull>(V2)) { - return NoAlias; // Unique values don't alias null - } else if (O2 && !isa<Argument>(O2) && isa<ConstantPointerNull>(V1)) { - return NoAlias; // Unique values don't alias null + + if (!isa<Argument>(O1) && isa<ConstantPointerNull>(V2)) + return NoAlias; // Unique values don't alias null + + if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(O1)) + if (GV->getType()->getElementType()->isSized()) { + // If the size of the other access is larger than the total size of the + // global, it cannot be accessing the global (it's undefined to load or + // store bytes after the global). + unsigned GlobalSize = + getTargetData().getTypeSize(GV->getType()->getElementType()); + if (GlobalSize < V2Size) + return NoAlias; + } + } + + if (O2) { + if (!isa<Argument>(O2) && isa<ConstantPointerNull>(V1)) + return NoAlias; // Unique values don't alias null + + if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(O2)) + if (GV->getType()->getElementType()->isSized()) { + // If the size of the other access is larger than the total size of the + // global, it cannot be accessing the global (it's undefined to load or + // store bytes after the global). + unsigned GlobalSize = + getTargetData().getTypeSize(GV->getType()->getElementType()); + if (GlobalSize < V1Size) + return NoAlias; + } } // If we have two gep instructions with must-alias'ing base pointers, figure |