[llvm-dev] LLVM + MASM (llvm-ml)

[Martin Storsjö via llvm-dev]

Hi,

On Fri, 23 Oct 2020, Eric Astor via llvm-dev wrote:

> Just a quick update on the llvm-ml project. As a refresher, this was a
> proposal to add native [MASM][1] support to LLVM's assembly capabilities, as
> part of supporting cross-platform Windows compilation.
> 
>    [1]: https://docs.microsoft.com/en-us/cpp/assembler/masm/microsoft-macro-as
> sembler-reference?view=vs-2019
> 
> A large set of directives are now supported, with a growing suite of tests.
> After the next outstanding chain of commits ([tip][2]) adds macro procedures
> and macro functions (including local symbols), this will include most of the
> headline features for the language. (STRUCTs have been in place for some
> time now, including type inference for size-checking.) Features not yet in
> place include:
>  *  RECORDs,
>  *  ASSUME,
>  *  the ALIGN/ORG/EVEN directives,
>  *  the GOTO directive (within macros),
>  *  anonymous labels, and
>  *  built-in macros (and the string-manipulation directives).
>     [2]: https://reviews.llvm.org/D89741
> 
> Anyone else interested in reviewing some of the commits around this project?

I just recently got an interest in this project, when I tried building the 
OpenMP runtimes for windows - and they contain one source file in MASM 
format.

>From very brief attempts at assembling the source file [1] with llvm-ml 
noticed that it lacked some sort of preprocessing that the source used, 
among a few other issues.

CMake also ends up adding a few parameters using forward slashes, while it 
seems like llvm-ml currently only accepts parameters with dashes. Handling 
both (like clang-cl and lld/COFF do, among others) probably would require 
rewriting the option handling using the llvm/Option framework, like those 
tools do.

An example command for building it looks like this (in 
llvm-project/openmp/build):

<tool> -Domp_EXPORTS -Iruntime/src -I../runtime/src -I../runtime/src/i18n 
-I../runtime/src/include -I../runtime/src/thirdparty/ittnotify -D 
_CRT_SECURE_NO_WARNINGS -D _CRT_SECURE_NO_DEPRECATE -D _WINDOWS -D _WINNT 
-D _WIN32_WINNT=0x0501 -D _USRDLL -win64 -D_M_AMD64 -DOMPT_SUPPORT=0 /c 
/Fo runtime/src/CMakeFiles/omp.dir/z_Windows_NT-586_asm.asm.obj 
../runtime/src/z_Windows_NT-586_asm.asm

When building for i386, you'd also see the parameters "/coff" and 
"/safeseh" added on the command line [2].

[1] https://github.com/llvm/llvm-project/blob/master/openmp/runtime/src/z_Windows_NT-586_asm.asm

[2] https://github.com/llvm/llvm-project/blob/master/openmp/runtime/cmake/LibompHandleFlags.cmake#L74-L82

// Martin