[PATCH] D86529: [5/5] [AArch64] Generate and parse SEH assembly directives

Wed Aug 26 14:10:46 PDT 2020

mstorsjo added inline comments.

================
Comment at: llvm/test/CodeGen/AArch64/lrint-conv-fp16-win.ll:7
+; CHECK-NEXT:  .seh_startepilogue
+; CHECK-NEXT:  .seh_endepilogue
 ; CHECK-NEXT:  ret
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efriedma wrote:
> mstorsjo wrote:
> > efriedma wrote:
> > > I think this indicates a bug somewhere else: we shouldn't be emitting seh_startepilogue in functions that don't have any other unwind info.
> > No, we do generate full proper directives for start/endproc, prologue and all that. It's just that the current testcase doesn't break if there's changes in the prologue of the function, but the sequence of `CHECK-NEXT` from `fcvtzs` to `ret` requires including these directives here in order not to break the test.
> > 
> > So for these testcases, that focus on testing some other aspect, I did the minimal changes to include the new directives only where they're needed in `CHECK-NEXT` sequences, but didn't go full out and added checks for all the generated directives. But I'll include one such case as well.
> > 
> > Alternatively, one could add `nounwind` attributes to the tested functions, to avoid the noise from the added directives. (Is it possible to achieve the same with some llc flag? I tried looking for one but didn't find any.)
> Should we be generating any .seh_* directives in this case?  If I'm not mistaken, we don't generate any actual unwind data in the object file.
The llc command in this testcase does generate unwind data in the generated object file, if it's written to an object file instead of output as asm.

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  https://reviews.llvm.org/D86529/new/

https://reviews.llvm.org/D86529