Set the "tail" flag on pattern-matched objc_storeStrong calls.
rdar://10531041.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148490 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/ObjCARC.cpp b/lib/Transforms/Scalar/ObjCARC.cpp
index 410f6bc..08bb67e 100644
--- a/lib/Transforms/Scalar/ObjCARC.cpp
+++ b/lib/Transforms/Scalar/ObjCARC.cpp
@@ -3600,6 +3600,11 @@
/// RetainRV calls to make the optimization work on targets which need it.
const MDString *RetainRVMarker;
+ /// StoreStrongCalls - The set of inserted objc_storeStrong calls. If
+ /// at the end of walking the function we have found no alloca
+ /// instructions, these calls can be marked "tail".
+ DenseSet<CallInst *> StoreStrongCalls;
+
Constant *getStoreStrongCallee(Module *M);
Constant *getRetainAutoreleaseCallee(Module *M);
Constant *getRetainAutoreleaseRVCallee(Module *M);
@@ -3803,6 +3808,11 @@
StoreStrong->setDoesNotThrow();
StoreStrong->setDebugLoc(Store->getDebugLoc());
+ // We can't set the tail flag yet, because we haven't yet determined
+ // whether there are any escaping allocas. Remember this call, so that
+ // we can set the tail flag once we know it's safe.
+ StoreStrongCalls.insert(StoreStrong);
+
if (&*Iter == Store) ++Iter;
Store->eraseFromParent();
Release->eraseFromParent();
@@ -3849,6 +3859,13 @@
PA.setAA(&getAnalysis<AliasAnalysis>());
+ // Track whether it's ok to mark objc_storeStrong calls with the "tail"
+ // keyword. Be conservative if the function has variadic arguments.
+ // It seems that functions which "return twice" are also unsafe for the
+ // "tail" argument, because they are setjmp, which could need to
+ // return to an earlier stack state.
+ bool TailOkForStoreStrongs = !F.isVarArg() && !F.callsFunctionThatReturnsTwice();
+
// For ObjC library calls which return their argument, replace uses of the
// argument with uses of the call return value, if it dominates the use. This
// reduces register pressure.
@@ -3905,6 +3922,13 @@
case IC_Release:
ContractRelease(Inst, I);
continue;
+ case IC_User:
+ // Be conservative if the function has any alloca instructions.
+ // Technically we only care about escaping alloca instructions,
+ // but this is sufficient to handle some interesting cases.
+ if (isa<AllocaInst>(Inst))
+ TailOkForStoreStrongs = false;
+ continue;
default:
continue;
}
@@ -3969,5 +3993,13 @@
}
}
+ // If this function has no escaping allocas or suspicious vararg usage,
+ // objc_storeStrong calls can be marked with the "tail" keyword.
+ if (TailOkForStoreStrongs)
+ for (DenseSet<CallInst *>::iterator I = StoreStrongCalls.begin(),
+ E = StoreStrongCalls.end(); I != E; ++I)
+ (*I)->setTailCall();
+ StoreStrongCalls.clear();
+
return Changed;
}