[CodeGen][ObjC] Emit invoke instead of call to call `objc_release` when necessary.

[ahatanak]

Summary

Prior to r349952, clang used to call objc_msgSend when sending a release messages, emitting an invoke instruction instead of a call instruction when it was necessary to catch an exception. That changed in r349952 because runtime function objc_release is called as a nounwind function, which broke programs that were overriding the dealloc method and throwing an exception from it. This patch restores the behavior prior to r349952.

rdar://problem/50253394

[erik.pilkington]

lib/CodeGen/CGObjC.cpp

2634–2635

Can't you just write EmitCallOrInvoke(fn, value)? See what we do in emitObjCValueOperation, which can handle this case.

[ahatanak]

Just call EmitCallOrInvoke.

[erik.pilkington]

LGTM, thanks!

lib/CodeGen/CGObjC.cpp

if (!fn) {
     if (llvm::Function *f = dyn_cast<llvm::Function>(fn.getCallee()))
       f->addFnAttr(llvm::Attribute::NonLazyBind);
   }
 
   // Cast the argument to 'id'.
   value = Builder.CreateBitCast(value, Int8PtrTy);
 
   // Call objc_release.
-  llvm::CallInst *call = EmitNounwindRuntimeCall(fn, value);
+  llvm::CallBase *call = EmitCallOrInvoke(fn, value);
 
   if (precise == ARCImpreciseLifetime) {
     call->setMetadata("clang.imprecise_release",
                       llvm::MDNode::get(Builder.getContext(), None));
   }
 }
 
 namespace {
   struct CallObjCAutoreleasePoolObject final : EHScopeStack::Cleanup {

test/CodeGenObjC/convert-messages-to-runtime-calls.m

 - (void)retain_super {
   // MSGS: {{call.*@objc_msgSend}}
   // CALLS: {{call.*@objc_msgSend}}
   [super retain];
 }
 
 @end
 
+@class Ety;
+
+// CHECK-LABEL: define {{.*}}void @testException
+void testException(NSObject *a) {
+  // MSGS: {{invoke.*@objc_msgSend}}
+  // CALLS: invoke{{.*}}void @objc_release(i8* %
+  @try {
+    [a release];
+  } @catch (Ety *e) {
+  }
+}