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

[David Majnemer]

On Wed, Jul 15, 2015 at 9:01 AM, Reid Kleckner <rnk at google.com> wrote:

> 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.
>

I think you'll want to implement "useFloat128ManglingForLongDouble" for the
mangling change.


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