std.math.frexp wrong on ARM

Johannes Pfau nospam at example.com
Thu Sep 27 00:57:52 PDT 2012


Am Wed, 26 Sep 2012 17:35:18 +0200
schrieb Don Clugston <dac at nospam.com>:

> On 26/09/12 17:13, Johannes Pfau wrote:
> > The frexp test fails on ARM. I think the mask in line 1491 is
> > wrong:
> >
> > https://github.com/D-Programming-Language/phobos/blob/master/std/math.d#L1491
> > For doubles, the 63 bit is sign, 62-52 are exponent and 51-0 are
> > mantissa.
> > The mask manipulates the bits 63-48 (ushort, 16bit)
> > 0x8000 is 0b1000000000000000
> > so it preserves the sign, but not the 4 bits of the mantissa? I
> > think it should be
> > 0b1000000000001111 (0x800F)?
> > This also fixes the test case on ARM.
> >
> > But I don't know much about this stuff, so I wonder if this is
> > correct?
> 
> You are correct. I will fix.
> 
> At least, it's good that the tests caught that.

OK, thanks.
Maybe we could also enhance the tests to test NaN, -NaN, +infinity,
-infinity, +0,-0 and probably a denormal?


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