[llvm-commits] [llvm-gcc-4.0] r43134 - in /llvm-gcc-4.0/trunk/gcc/config/rs6000: darwin-ldouble.c darwin-libgcc.10.4.ver darwin-libgcc.10.5.ver darwin.h

[Chris Lattner]

On Oct 18, 2007, at 4:00 PM, Dale Johannesen wrote:

>
> On Oct 18, 2007, at 3:51 PM, Chris Lattner wrote:
>
>>
>> On Oct 18, 2007, at 2:09 PM, Dale Johannesen wrote:
>>
>>>
>>> On Oct 18, 2007, at 1:04 PM, Chris Lattner wrote:
>>>>>    /* Use fused multiply-add to get low part of a * c.  */
>>>>> -/* APPLE LOCAL begin LLVM */
>>>>> -#ifndef __llvm__  /* FIXME: no long double support! */
>>>>>    asm ("fmsub %0,%1,%2,%3" : "=f"(tau) : "f"(a), "f"(c), "f"(t));
>>>>> -#endif
>>>>
>>>> Have you tested to see if long double works with inline asm?
>>>
>>> No; there are no long double instructions, so I'm not sure how you
>>> would write such a thing in inline asm.
>>> (The asm in the fix above breaks the long double into two doubles
>>> explicitly, and I'd expect that to be the common practice).
>>
>> Yep, tha'ts what I mean: when the above gets broken into the two
>> component registers, do they come through correctly in the .s file?
>
> The above does not get broken into component registers by the  
> compiler.
> Those are double variables and double registers.   The function is
> declared
> as taking 4 double arguments.  The excuse for this in the code is
>
> /* All these routines actually take two long doubles as parameters,
>     but GCC currently generates poor code when a union is used to turn
>     a long double into a pair of doubles.  */
>
> but the inability to reference long doubles in asm's may have had
> something
> to do with it also.

Ah, ok.  Thanks Dale,

-Chris