Re: [avr-llvm-devel] Inline assembly. Mostly just a stub.

[Stepan D. <stp...@na...>]

The patch. Forgot to attach it.
-Stepan.
Stepan Dyatkovskiy wrote:
> Hi Borja,
>
>  > What happens in your example above when you use a real instruction like
>> for example LDD? Does it still use GPR8 regs? To me it's weird that if
>> you use a real instruction where operands are clearly defined in the td
>> file the instruction selector uses  an invalid regclass.
>
> There are two kinds of inline asm support in LLVM:
> 1. You just support all the constraints and pastes inline-asm contents
> as-is. That's why its still allowed to use names like "some_instr".
> 2. You may expand inline-asm strings set, or in another words just parse
> it onto set of instructions. In this case you have to implement
> TargetLowering::ExpandInlineAsm method.
> I'd want to start it on this week though...
>
> But first we have to get avr-libc compilable (perhpas I read you
> thoughts ;-) )
>
> Relative to memory constrains. I implemented initial version it can
> catch simplest cases (from test-case):
>
> @a = internal global i16 0, align 4
> @b = internal global i16 0, align 4
> define void @mem() {
>    ;CHECK: some_instr Z, Y
>    call void asm "some_instr $0, $1", "=*Q,=*Q"(i16* @a, i16* @b)
>    ret void
> }
>
> The patch is attached.
>
> Its in my todo yet, to handle local variables. They could be emitted as
> Y+q expression. Hope to present this support tomorrow. So if 'a' and 'b'
> from example above would be local we could get "some_instr Y, Y+2"
>
> -Stepan.
>
>