Re: math-emu on buildd machine?

[Paolo Bonzini <paolo.bonzini@polimi.it>]

Steve Langasek wrote:
> On Sun, Jan 13, 2008 at 02:01:41PM +0100, Paolo Bonzini wrote:
> > Is the math-emu module loaded (or compiled in the kernel) on the buildd 
> > alpha machines?  The gnu-smalltalk package is failing for 3.0 because the 
> > emulator converts erroneously a denormal float to double:
>
> > st> p:= (FloatE coerce: 1) timesTwoPower: -149.
> > 2.6524948e-315
>
> > (2^-149 is actually ~1e-44) despite the program is compiled with -mieee.
>
> > If it is, it is a bug in the emulator and the best solution is to XFAIL the 
> > test on alpha.  But if it is not loaded, maybe it should...
>
> The alpha buildd is an ev68; math-emu is not relevant on that chip.

So that might be a known errata?  The following program should yield
1.4013e-45 twice (the bug might show up only at -mieee -O0, I don't know).

float x = 1.0;
double y;

int g(float z)
{
  printf ("%g\n", z);
}

int main()
{
  x *= (1.0f / 65536.0f);
  x *= (1.0f / 65536.0f);
  x *= (1.0f / 65536.0f);
  x *= (1.0f / 65536.0f);
  x *= (1.0f / 65536.0f);
  x *= (1.0f / 65536.0f);
  x *= (1.0f / 65536.0f);
  x *= (1.0f / 65536.0f);
  x *= (1.0f / 65536.0f);
  x *= (1.0f / 32.0f);
  g(x);
  y = x;
  g(y);
}

Paolo