[cfe-dev] Where is the unknown token when using the Integrated Assembler (Intel syntax, neg instruction)?

[Reid Kleckner]

I think it's complaining about the % in %rcx. Intel assembly syntax doesn't
use the % prefix on registers.

I don't think our backend knows how to expand operands using anything other
than AT&T syntax. If this is the case, using .intel_syntax directives in
inline assembly won't work very well until something changes.

If you need intel syntax, what you could try doing is passing -fasm-blocks
and writing MSVC / Intel style inline assembly, which looks like:

int SomeFunction(int* ptr, int val1, int val2) {
  __asm {
    neg val1
  };
}

I would only recommend doing this if you already have ifdefs to support
inline asm in MSVC.

On Wed, Jul 22, 2015 at 11:42 PM, Jeffrey Walton <noloader at gmail.com> wrote:

> I'm part of an existing project, and I'm working on support for
> Clang's Integrated Assembler. The project has copious amounts of
> inline assembly (both stand alone one-liners for shift and rotates;
> and blocks for things like AES and GCM mode). Even better (maybe
> worse?), it mixes AT&T and Intel because it supports Microsoft and GNU
> platforms.
>
> I'm having trouble understanding an error message from the assembler.
> The message is on the use of 'neg' under the Intel dialect:
>
> <inline asm>:3:7: note: instantiated into assembly here
>          neg %rcx;
>              ^
>
> The code looks like:
>
> int SomeFunction(int* ptr, int val1, int val2)
> {
>     int ret;
>     __asm__ __volatile (
>         ".intel_syntax" "\n"
>         neg %1;
>         ...
>     )
>
>    return ret;
> }
>
> I'm testing on x86_64, so I tried changing to 'negq %1;' with no joy.
> (Taking a hint from
> http://clang.llvm.org/compatibility.html#inline-asm):
>
> <inline asm>:3:8: note: instantiated into assembly here
>          negq %rcx;
>              ^
>
> I'm experiencing it with both Apple's Clang 3.2, and LLVM's Clang
> 3.6.0 built from sources (http://llvm.org/releases/).
>
> Naively (and I stress naively), “unknown token in expression” appears
> to be a bogus message since the assembly instruction its complaining
> about does not seem to have a problem. So I suspect there is something
> else the integrated assembler finds offensive.
>
> Could anyone help me understand what the issue is?
>
> Thanks in advance. Jeff.
>
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