[PATCH] D47988: [CodeGen] Emit MSVC funclet IR for Obj-C exceptions

[Shoaib Meenai via Phabricator via cfe-commits]

smeenai added a comment.

@rnk remember how I was asking you about inlining into catchpads on IRC a few days back? It was in relation to this change.

If I have a file `finally1.m`:

  void f(void);
  void g() {
    @try {
      f();
    } @finally {
      f();
    }
  }

and compile it with:

  clang -cc1 -triple i686-windows-msvc -fobjc-runtime=ios-6.0 -fexceptions -fobjc-exceptions -Os -emit-llvm -o - finally1.m

the @finally calls out to the captured statement instead of inlining it:

  finally.catchall:                                 ; preds = %catch.dispatch
    %1 = catchpad within %0 [i8* null, i32 64, i8* null]
    call fastcc void @__captured_stmt() [ "funclet"(token %1) ]
    call void @_CxxThrowException(i8* null, %eh.ThrowInfo* null) #3 [ "funclet"(token %1) ]
    unreachable

If I add an outer try-catch scope, as in `finally2.m`:

  void f(void);
  void g() {
    @try {
      @try {
        f();
      } @finally {
        f();
      }
    } @catch (...) {
    }
  }

and run the same compilation command:

  clang -cc1 -triple i686-windows-msvc -fobjc-runtime=ios-6.0 -fexceptions -fobjc-exceptions -Os -emit-llvm -o - finally2.m

the @finally inlines the captured statement:

  finally.catchall:                                 ; preds = %catch.dispatch
    %2 = catchpad within %0 [i8* null, i32 64, i8* null]
    invoke void @f() #2 [ "funclet"(token %2) ]
            to label %invoke.cont1 unwind label %catch.dispatch4
  
  invoke.cont1:                                     ; preds = %finally.catchall
    invoke void @_CxxThrowException(i8* null, %eh.ThrowInfo* null) #3 [ "funclet"(token %2) ]
            to label %unreachable unwind label %catch.dispatch4

Any idea why we would see inlining in one case and not the other? i686 vs. x86-64 doesn't make any difference, and neither does -Os vs. -O1 vs. -O2.


Repository:
  rC Clang

https://reviews.llvm.org/D47988