sin, cos, other languages and DMD/LDC difference

[Walter Bright]

On 2/8/2014 6:13 AM, bearophile wrote:
> Philippe Sigaud:
>
>> Now, what I found more confusing is that, compiling with DMD or LDC, I got
>> different results. Since Phobos code defining sin and cos in std.math and
>> core.stdc.math is the same for DMD and LDC (duh!), I guess that means
>> different intrinsics are used?
>
> LDC2 optimizes this code even worse than DMD.

Even worse? Mind telling me what is bad about this code?

         fld qword ptr 4[ESP]
         fmul    qword ptr FLAT:_DATA[00h]
         fsin
         fld qword ptr 4[ESP]
         fmul    qword ptr FLAT:_DATA[08h]
         fcos
         faddp   ST(1),ST
         ret 8

BTW, the differences in results is not due to optimization, but to dmd keeping 
intermediate results to 80 bits of precision, while other compilers are doing 64 
bit precision on intermediate results.