[dmd-internals] 64bit bad codegen from ulong pointers.

[Walter Bright]

Good, I can reproduce this one.

BTW, you'll need a 64 bit machine sooner or later! I bought one for 
about $300 last month (recycling keyboard, mouse, display, and hard disk 
from an older machine).

Don Clugston wrote:
> Aargh, it was an incorrect reduction. Here's an larger case which
> fails with the latest DMD, Phobos, and druntime.
> (Reducing test cases is a bit painful through a remote connection).
> -------------
> double nextUpw(double x) @trusted nothrow
> {
>     ulong *ps = cast(ulong *)&x;
>
>     if ((*ps & 0x7FF0_0000_0000_0000) == 0x7FF0_0000_0000_0000) {
>         if (x == -x.infinity) return  -x.max;
>         return x;
>     }
>     if (!(*ps & 0x8000_0000_0000_0000L))  {
>          assert(x>=0);
>     }
>     return x;
> }
>
> void main()
> {
>   nextUpw(-double.min_normal*(1.0 - double.epsilon));
> }
> =========
>
> On 3 January 2011 23:37, Walter Bright <walter at digitalmars.com> wrote:
>   
>> Works when I try it. Do you have the latest dmd?
>>
>> Don Clugston wrote:
>>     
>>> Reduced test case  from std.math. *ps is 0x800F_FFFF_FFFF_FFFF, yet
>>> the if() branch is not taken.
>>> This one looks as though it might be the root cause of many failures.
>>>
>>> void check(double x)
>>> {
>>> ulong *ps = cast(ulong *)&x;
>>> if (*ps & 0x8000_0000_0000_0000) {}
>>> else assert(x>=0);
>>> }
>>>
>>> void main()
>>> {
>>>  check(-double.min_normal*double.epsilon);
>>> }
>>>
>>>
>>>       
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>>     
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