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Re: MIPS tests (nan-legacy.c and nans-legacy.c) failing
- From: Richard Sandiford <rdsandiford at googlemail dot com>
- To: "Maciej W. Rozycki" <macro at codesourcery dot com>
- Cc: Steve Ellcey <sellcey at mips dot com>, <gcc-patches at gcc dot gnu dot org>
- Date: Tue, 13 Aug 2013 18:25:40 +0100
- Subject: Re: MIPS tests (nan-legacy.c and nans-legacy.c) failing
- References: <9f69a43f-c31f-4c49-aaa0-b022fd602f52 at BAMAIL02 dot ba dot imgtec dot org> <87fvul5k37 dot fsf at talisman dot default> <alpine dot DEB dot 1 dot 10 dot 1308130002260 dot 8514 at tp dot orcam dot me dot uk>
"Maciej W. Rozycki" <firstname.lastname@example.org> 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 <email@example.com>
> * gcc.target/mips/nan-legacy.c: Accept 4294967295 as an
> alternative to -1.
> * gcc.target/mips/nans-legacy.c: Likewise.