[dmd-internals] 64 bit bug: rndtol fails.

[Walter Bright]

Thanks, Brad & Don. Commit 882.

Brad Roberts wrote:
> On 1/12/2011 1:45 PM, Don Clugston wrote:
>   
>> ---
>> import std.math;
>>
>> void main()
>> {
>>       assert( rndtol(-3.0) == -3 );
>> }
>> ---
>>
>> This is the only failure in std.mathspecial.
>>     
>
> Confirmed buggy in d1 as well.
>
> The generated code:
> _Dmain:
>                 push    RBP
>                 mov     RBP,RSP
>                 sub     RSP,010h
>                 fld     tbyte ptr FLAT:.rodata[00h][RIP]
>                 fistp   long64 ptr -8[RBP]
>                 mov     EAX,-8[RBP]
>                 cmp     RAX,0FFFFFFFDh
>                 je      L25
>                 mov     EDI,7
>                 call      _D3bug8__assertFiZv at PC32
> L25:            xor     EAX,EAX
>                 leave
>                 ret
>
> Comparing it with the 32 bit version, the tbyte ptr part is fine, but the mov
> EAX is almost certainly wrong.
>
> Try this change.. tested only with this repro case so far:
>
> Index: backend/cg87.c
> ===================================================================
> --- backend/cg87.c      (revision 880)
> +++ backend/cg87.c      (working copy)
> @@ -3063,7 +3063,11 @@
>              genfltreg(c2,0x8B,findreglsw(retregs),0);
>          }
>          else
> +        {
>              c2 = genfltreg(c2,0x8B,reg,0);      // MOV reg,floatreg
> +            if (tysize(tym) == 8 && I64)
> +                code_orrex(c2, REX_W);
> +        }
>          c2 = cat(c2,fixresult(e,retregs,pretregs));
>
>          return cat(c1,c2);
>
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>