[PATCH] D125582: [llvm-ml] Add support for extern proc

[Hans Wennborg via Phabricator via llvm-commits]

hans added a comment.

> Interestingly enough, under MSVC the following is allowed:
>
> extern foo:proc
>
> mov eax, foo
>
> MSVC will output:
>
> mov eax, 0
>
> while llvm-ml will currently output:
>
> mov eax, dword ptr [foo]
>
> (since foo is an extern)
>
> Arguably, llvm-ml's output makes more sense, even though it's
>  inconsistent with MSVC ml. However, since moving an extern proc symbol
>  to a register doesn't really make sense in the first place, we'll treat
>  it as undefined behavior for now.

Maybe I'm just not familiar enough with MASM, but both outputs seem odd to me. I would expect MSVC's output to be accompanied by a relocation, but it seems that's not the case?

"mov eax, foo" reads like "move the address of foo into eax" to me, which seems like it would be a sensible thing to do. What llvm-ml does is more like "load from foo into eax" which seems odd if "foo" is a function.

In any case, if we can't support it in a sensible way, can we at least error about it? And there should be a test.


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https://reviews.llvm.org/D125582