Teach ValueTracking how to look through GlobalAliases. GlobalAliases are
not folded in the constant folder because the constant folder doesn't
simplify ConstantExpr operands.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81864 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 1782ede..9494a2f 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -16,6 +16,7 @@
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/GlobalVariable.h"
+#include "llvm/GlobalAlias.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/LLVMContext.h"
#include "llvm/Operator.h"
@@ -105,6 +106,17 @@
KnownOne.clear();
return;
}
+ // A weak GlobalAlias is totally unknown. A non-weak GlobalAlias has
+ // the bits of its aliasee.
+ if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
+ if (GA->mayBeOverridden()) {
+ KnownZero.clear(); KnownOne.clear();
+ } else {
+ ComputeMaskedBits(GA->getAliasee(), Mask, KnownZero, KnownOne,
+ TD, Depth+1);
+ }
+ return;
+ }
KnownZero.clear(); KnownOne.clear(); // Start out not knowing anything.