[libcxx-commits] [PATCH] D60417: [libunwind] Add support for ARMv7-M architecture which uses the Thumb 2 ISA (unified syntax)

Mon Apr 8 23:44:58 PDT 2019

mstorsjo added a comment.

In D60417#1459128 <https://reviews.llvm.org/D60417#1459128>, @jeremfg wrote:

> In D60417#1458778 <https://reviews.llvm.org/D60417#1458778>, @mstorsjo wrote:
>
> > The change looks sensible to me, but should we maybe even skip the `#if` altogether? If the files uses unified syntax and can't be parsed in thumb mode otherwise, there's maybe no need for conditionals at all?
>
>
> I'm no expert but I just read that UAL (Unified Assembler Language), while being backward compatible with the old ARM syntax, is **not** compatible with the previous Thumb syntax.
>  http://downloads.ti.com/docs/esd/SPNU118/unified-assembly-language-syntax-support-spnu1184444.html
>
> But again, perhaps it doesn't matter in the specific case that concerns us here? I guess it depends on whether the code in the ###if !defined(__ARM_ARCH_ISA_ARM) && __ARM_ARCH_ISA_THUMB == 1## condition that follows contains only valid UAL syntax as well. Which I am not qualified to confirm or not.

Oh, sorry, I was sloppy and didn't actually check the rest of the file to see the existing conditional alternative codepaths with `!defined(__ARM_ARCH_ISA_ARM) && __ARM_ARCH_ISA_THUMB == 1`.

Given that, the suggested form of this patch is indeed correct - sorry for the noise.

I can commit the patch for you, but I'd need approval by either of @EricWF, @ldionne or @mclow.lists first.

Repository:
  rUNW libunwind

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https://reviews.llvm.org/D60417