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

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

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.