[PATCH] D87370: [llvm-readobj] [ARMWinEH] Print ARM64 packed unwind info

[Martin Storsjö via Phabricator via llvm-commits]

mstorsjo added inline comments.


================
Comment at: llvm/test/tools/llvm-readobj/COFF/arm64-packed-unwind.s:59
+// CHECK-NEXT:     Prologue [
+// CHECK-NEXT:       sub sp, sp, #0
+// CHECK-NEXT:       stp d10, d11, [sp, #24]
----------------
efriedma wrote:
> "sub sp, sp, #0" is a no-op.  Is that really the right interpretation?  
If strictly following the steps for the equivalent prologue in the docs for the packed format, the "sub sp, sp, #0" corresponds to step 5d/5e. But I guess it's a matter of taste whether to print it or not (and I don't feel strongly about it).

As this is the last instruction in the prologue/first in the epilogue, it shouldn't really matter whether it's included or not, even when unwinding. If it's considered included in the synthesized prologue, the prologue becomes one instruction longer. If unwinding from that particular location, it could consider the unwind part starting from an unfinished prologue and skip the "sub sp, sp, #0" synthesized instruction, which has no effect. Or if it's not included in the synthesized prologue, the unwind is considered originating in the body of the function, and executing the full prologue, with the same effect.

So it's just a matter of taste and/or trying to stick closely to the spec where possible.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D87370/new/

https://reviews.llvm.org/D87370