Use address-taken to disambiguate global variable and indirect memops.
Major steps include:
1). introduces a not-addr-taken bit-field in GlobalVariable
2). GlobalOpt pass sets "not-address-taken" if it proves a global varirable
dosen't have its address taken.
3). AA use this info for disambiguation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193251 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index bf92969..4e423a7 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -1238,6 +1238,17 @@
return NoAlias;
if (isEscapeSource(O2) && isNonEscapingLocalObject(O1))
return NoAlias;
+
+ // If one object is a global variable without address taken, the other one
+ // is a different object, they will not alias because the global variable
+ // in question cannot be indirectly accessed.
+ if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(O1))
+ if (!GV->AddressMaybeTaken())
+ return NoAlias;
+
+ if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(O2))
+ if (!GV->AddressMaybeTaken())
+ return NoAlias;
}
// If the size of one access is larger than the entire object on the other