gcc code generation problems

Marius Strobl marius at alchemy.franken.de
Wed Mar 10 20:05:06 UTC 2010

On Wed, Mar 10, 2010 at 09:14:20PM +1100, Peter Jeremy wrote:
> On 2010-Mar-10 08:18:07 +1100, Peter Jeremy <peterjeremy at acm.org> wrote:
> >My patch to fix all three problems is attached - it's slightly
> >different to yours (and doesn't include any of the constification).
> >We both seem to basically agree.  I think my approach to RN_DECODE()
> >should be somewhat faster (since it does less testing), though it
> >meant re-defining FTYPE_LNG.
> I've revised my previous patch to remove two now-unused variables as
> well as include the constification in your patch.

Thanks, I've committed a merged version.

> After rebuilding libc, the eval.s program I posted a few days ago now
> works correctly as posted and with the following modifications to the
> two !!! blocks:
> ((1 << 53) - 1) => %f34; fxtos %f34,%f20
> ((1 << 53) - 1) => %f34; fxtod %f34,%f40
> ((1 << 53) - 1) => %f34; fxtoq %f34,%f40
> 0x5a000000 => %f31; fstox %f31,%f32
> 0x433fffffffffffff => %f34; fdtox %f34,%f40
> (The above are all emulated according to the US-IIIi databook).
> Unfortunately, the following code:
> 0x4033ffffffffffff => %f40; 0xf000000000000000 => %f42; fqtox %f40,%f30
> gives a result of 0x001ffffffffffff0 instead of 0x001fffffffffffff.
> The low order bits (those in %f42) appear to be ignored.  A similar
> problem occurs with fqtod.  faddq %f40,%f40,%f32 has the low
> destination (%f34) shifted one bit right - which implies that the low
> order register is ignored in only one argument.  I don't see any
> obvious issue anywhere and have elected to leave this problem for now.
> fmovq does work but uses a different code-path.
> > (and have been
> >thinking about how to create regression tests for the emulator).
> Two possibilities here are UCBTEST and TestFloat (note that SoftFloat
> is already in the FreeBSD tree).  I have copies of both but haven't
> actually converted either into a suitable test harness.

FYI, the OpenSolaris source also includes a SPARC centric test suite
in src/cmd/fps/fptest.


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