From: Richard Sandiford <rdsandiford@googlemail.com>
To: "Maciej W. Rozycki" <macro@codesourcery.com>
Cc: Steve Ellcey <sellcey@mips.com>, <gcc-patches@gcc.gnu.org>
Subject: Re: MIPS tests (nan-legacy.c and nans-legacy.c) failing
Date: Tue, 13 Aug 2013 17:25:00 -0000 [thread overview]
Message-ID: <87ioz9iju3.fsf@talisman.default> (raw)
In-Reply-To: <alpine.DEB.1.10.1308130002260.8514@tp.orcam.me.uk> (Maciej W. Rozycki's message of "Tue, 13 Aug 2013 14:28:34 +0100")
"Maciej W. Rozycki" <macro@codesourcery.com> writes:
> I've had a look now and that is related to the width of `long' on the
> host -- encode_ieee_double returns its output 32-bit bit patterns in a
> buffer of signed longs. The arithmetic value of these patterns therefore
> depends on whether the width of `long' is 32 bits or wider.
>
> Here, in the case of nan-legacy.c, we have:
>
> image_hi <- 0x7ff7ffff
> image_lo <- 0xffffffff
>
> so the returned pair of long values will be:
>
> 2146959359, -1
>
> on a host where the width of `long' is 32 bits and:
>
> 2146959359, 4294967295
>
> on a host where the width of `long' is 64 bits. Then when supplied as the
> argument to the assembly-language .word pseudo-op, the two sets of values
> produce the same bit patterns in the object file produced.
>
> It's not clear to me if this dependency on the width of `long' is a bug
> or feature, but a path-of-least-resistance fix is as follows.
IMO a bug. If we're sure 32 bits is enough then we should use "int".
If we're not sure we should use HOST_WIDE_INT. The only thing using
"long" is going to do is create this kind of weird host dependence.
I can't argue with the path of least resistance though.
> 2013-08-13 Maciej W. Rozycki <macro@codesourcery.com>
>
> gcc/testsuite/
> * gcc.target/mips/nan-legacy.c: Accept 4294967295 as an
> alternative to -1.
> * gcc.target/mips/nans-legacy.c: Likewise.
OK, thanks.
Richard
next prev parent reply other threads:[~2013-08-13 17:25 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-30 23:27 Steve Ellcey
2013-08-07 20:20 ` Richard Sandiford
2013-08-13 13:28 ` Maciej W. Rozycki
2013-08-13 16:49 ` Steve Ellcey
2013-08-13 17:25 ` Richard Sandiford [this message]
2013-08-13 21:53 ` Maciej W. Rozycki
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