[cfe-dev] invalid instruction mnemonic with Clang-Cl and FA flag

[Reid Kleckner via cfe-dev]

Clang's Intel assembler parser isn't as robustly tested as the GNU
assembler parser. This has been a recurring issue ever since we switched
clang-cl's assembly output to the Intel dialect:
https://bugs.llvm.org/show_bug.cgi?id=36676

I see the string repmovsdi here:
https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/X86/X86InstrCompiler.td#L383

I think it's just a typo, let me see if I can fix it...

On Wed, Mar 24, 2021 at 4:06 AM Gaier, Bjoern via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> Hello Clang-Devs,
>
>
>
> I run into a strange error with Clang-Cl - I hope I can explain it. We use
> Clang-Cl via the LLVM extension in Visual Studio and use it to compile our
> source code. One of the flags we set for the compiler is "/FA" which gives
> us assembly output. Everything fine so far, no problems.
>
>
>
> I then add a simple copy loop to our code, that is copying int32 values
> from one address to another one. When compiling this construct Clang-Cl
> suddenly exited with: "error: invalid instruction mnemonic 'movsdi'".
>
> However, when I remove the "/FA" flag everything compiles fine and runs
> fine in the end... Strangely, I couldn't figure out what the "movsdi"
> mnemonic is...
>
>
>
> The Assembly code looks like this:
>
> .LBB15_31:                              #   in Loop: Header=BB15_17 Depth=1
>
>                 mov       ecx, 32
>
>                 mov       edx, 4
>
>                 call         calloc
>
>                 mov       qword ptr [r12 + rbp + 96], rax
>
>                 mov       qword ptr [r12 + rbp + 88], rax
>
>                 mov       ecx, 32
>
>                 mov       rdi, rax
>
>                 rep movsdi es:[rdi], [rsi]
>
>                 jmp        .LBB15_33
>
>
>
> My Clang-Cl version is:
>
> clang version 11.0.0 (https://github.com/llvm/llvm-project.git
> 176249bd6732a8044d457092ed932768724a6f06)
>
> Target: x86_64-pc-windows-msvc
>
> Thread model: posix
>
>
>
> The target is the same as in the version (x86_64-pc-windows-msvc).
>
>
>
> Does anyone know what is going on?
>
>
>
> Kind greetings
>
> Björn
> Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816,
> USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert
> Plank, Markus Bode, Takashi Nagano, Junichi Tajika, Ergin Cansiz.
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