ObjCARC: Don't look at users of ConstantData
Stop looking at users of UndefValue and ConstantPointerNull in the
objective C ARC optimizers. The other users aren't actually
interesting, since they're not pointing at a particular object. I
imagine these calls could be optimized through -instcombine... maybe
they already are?
These early returns will be required at some point in the future, with a
WIP patch that asserts when someone accesses a use-list on ConstantData.
llvm-svn: 282338
diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
index a6907b5..ed5063c 100644
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
+++ b/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
@@ -53,6 +53,11 @@
/// \brief This is similar to GetRCIdentityRoot but it stops as soon
/// as it finds a value with multiple uses.
static const Value *FindSingleUseIdentifiedObject(const Value *Arg) {
+ // ConstantData (like ConstantPointerNull and UndefValue) is used across
+ // modules. It's never a single-use value.
+ if (isa<ConstantData>(Arg))
+ return nullptr;
+
if (Arg->hasOneUse()) {
if (const BitCastInst *BC = dyn_cast<BitCastInst>(Arg))
return FindSingleUseIdentifiedObject(BC->getOperand(0));
@@ -644,6 +649,12 @@
ARCInstKind &Class) {
// Check for a return of the pointer value.
const Value *Ptr = GetArgRCIdentityRoot(AutoreleaseRV);
+
+ // If the argument is ConstantPointerNull or UndefValue, its other users
+ // aren't actually interesting to look at.
+ if (isa<ConstantData>(Ptr))
+ return;
+
SmallVector<const Value *, 2> Users;
Users.push_back(Ptr);
do {