[PATCH] D124762: [WinEHPrepare] Avoid truncation of EH funclets with GNUstep ObjC runtime

[Reid Kleckner via Phabricator via llvm-commits]

rnk added a comment.

Thanks!

In D124762#3485478 <https://reviews.llvm.org/D124762#3485478>, @sgraenitz wrote:

> I guess testing must be split in two:
>
> - Clang wants to make sure the "funclet" bundle operand gets emitted for ObjC ARC runtime calls on Windows. Maybe that fits into clang/test/CodeGenObjC/gnu-exceptions.m <https://github.com/llvm/llvm-project/blob/main/clang/test/CodeGenObjC/gnu-exceptions.m>?

That seems like a good template for a new test. I think it probably deserves its own file. I imagine it will grow to be a more extensive test suite covering the interaction between GNUstep Objective C exceptions and WinEH.

> - LLVM wants to check that WinEHPrepare handles these runtime calls correctly. For that maybe I can use llvm/test/CodeGen/X86/win-funclet-cfi.ll <https://github.com/llvm/llvm-project/blob/main/llvm/test/CodeGen/X86/win-funclet-cfi.ll> as a template and adjust it for the ObjC ARC case?

You could go that route, but I would probably start with simplified ObjC++ code, and iteratively modify that until you get the IR that has the funclets that you want to see. This is a decent starting template:

  void maythrow();
  void arcOpsInFunclet() {
    try {
      maythrow();
    }
    catch (...) {
      // Do things that generate ARC intrinsics, probably set up an `id` variable.
    }
  }

Maybe you could make the test plain ObjC, but I don't know it very well.

Lastly, I think the inliner needs to be taught that these intrinsics need to carry operand bundles, otherwise this problem will arise after optimization. The inliner has the same logic here:
https://github.com/llvm/llvm-project/blob/main/llvm/lib/Transforms/Utils/InlineFunction.cpp#L2311

The test case for this should be:

  struct Foo {
    inline __attribute__((always_inline)) ~Foo() { /* ARC ops to inline */ }
  };
  void maythrow();
  void bar() {
    Foo o;
    maythrow();
  }



================
Comment at: llvm/lib/CodeGen/WinEHPrepare.cpp:966
 
-        if (FuncletBundleOperand == FuncletPad)
+        if (!FuncletPad || FuncletBundleOperand == FuncletPad)
           continue;
----------------
Is this change necessary? It seems like it shouldn't be after the clang and preisel pass changes.


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