[LLVMdev] __float128 (f128) calling convention bug on x86_64

[Reid Kleckner]

On Mon, Jul 13, 2015 at 12:33 PM, Chih-hung Hsieh <chh at google.com> wrote:
>
> I found that long double complex (with two f128 values) also have calling
> convention compatibility problem with gcc and can be fixed similarly.
> My current patch does change quite a few places in type legalizing pass
> and some other optimizations related to f128 or i128 values. A few changes
> in the softening of floating point types to keep some f128 typed IR and
> convert some f128 opcode to library function calls.
>
> Has anyone tried this approach or have other solution?
>

It sounds like you're on the right track for the low-level part of this.

The responsibility of matching platform ABI calling conventions is sort of
split across clang and LLVM. I think the way to get the calling convention
right is to change Clang to use x86_fp80 as the LLVM type for parameter and
return types, with some extra coercions inserted before calls and in
function prologues.

The mangling will need a separate change as it doesn't look at LLVM IR.
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