Make BasicAliasAnalysis recognize the fact a noalias argument cannot alias another argument, even if the other argument is not itself marked noalias.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182755 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index f8509dd..f20e83e 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -142,6 +142,17 @@
return ObjectSize != AliasAnalysis::UnknownSize && ObjectSize == Size;
}
+/// isIdentifiedFunctionLocal - Return true if V is umabigously identified
+/// at the function-level. Different IdentifiedFunctionLocals can't alias.
+/// Further, an IdentifiedFunctionLocal can not alias with any function
+/// arguments other than itself, which is not neccessarily true for
+/// IdentifiedObjects.
+static bool isIdentifiedFunctionLocal(const Value *V)
+{
+ return isa<AllocaInst>(V) || isNoAliasCall(V) || isNoAliasArgument(V);
+}
+
+
//===----------------------------------------------------------------------===//
// GetElementPtr Instruction Decomposition and Analysis
//===----------------------------------------------------------------------===//
@@ -1205,10 +1216,10 @@
(isa<Constant>(O2) && isIdentifiedObject(O1) && !isa<Constant>(O1)))
return NoAlias;
- // Arguments can't alias with local allocations or noalias calls
- // in the same function.
- if (((isa<Argument>(O1) && (isa<AllocaInst>(O2) || isNoAliasCall(O2))) ||
- (isa<Argument>(O2) && (isa<AllocaInst>(O1) || isNoAliasCall(O1)))))
+ // Function arguments can't alias with things that are known to be
+ // unambigously identified at the function level.
+ if ((isa<Argument>(O1) && isIdentifiedFunctionLocal(O2)) ||
+ (isa<Argument>(O2) && isIdentifiedFunctionLocal(O1)))
return NoAlias;
// Most objects can't alias null.