[llvm-dev] MS assembly integer literal question

[Eric Astor via llvm-dev]

Hi all,

I've got an interesting AsmLexer failure (originally found as a breakage
post-D87400 <https://reviews.llvm.org/D87400>, now reverted).
ms-inline-asm-avx512.c
<https://github.com/llvm/llvm-project/blob/a36ddf0aa9db5c1086e04f56b5f077b761712eb5/clang/test/CodeGen/ms-inline-asm-avx512.c#L26-L27>
includes
the line:
__asm vaddps xmm1, xmm2, [c]{1to4}

The trouble is: MASM doesn't use the {1toX} syntax for the AVX-512
instructions. Instead, they implemented a "bcst" keyword, which would
roughly apply as:
__asm vaddps xmm1, xmm2, dword bcst [c]
See
https://devblogs.microsoft.com/cppblog/microsoft-visual-studio-2017-supports-intel-avx-512/#embedded-broadcast

Can we remove support for the {1toX} syntax in MASM contexts, or do we need
to keep it until we can implement "bcst" support?

Context:

The current implementation (before my change) doesn't support this "bcst"
keyword, so it isn't actually following MASM - but no one noticed. x64 MSVC
doesn't allow inline assembly, so there's nothing to compare to in that
context.

The problem: I'm trying to add support for full MASM-style integer literals
in our inline assembly when targeting MSVC compatibility (or at least in
the upcoming LLVM-ML project). The "1to4" syntax conflicts with that, as
"1t" gets lexed as an integer literal, with the "t" recognized as a decimal
radix specifier. We can special-case that away by checking for an "o"
following the "t", but that might have false positives.

Thanks,
- Eric
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20200923/b37ce543/attachment.html>