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Re: MIPS tests (nan-legacy.c and nans-legacy.c) failing
- From: "Maciej W. Rozycki" <macro at codesourcery dot com>
- To: Richard Sandiford <rdsandiford at googlemail dot com>, Steve Ellcey <sellcey at mips dot com>
- Cc: <gcc-patches at gcc dot gnu dot org>
- Date: Tue, 13 Aug 2013 14:28:34 +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>
On Wed, 7 Aug 2013, Richard Sandiford wrote:
> > When I run two of your new tests in gcc.target/mips (nan-legacy.c and
> > nans-legacy.c), they are failing because my GCC is putting out
> >
> > .word 4294967295
> >
> > instead of
> >
> > .word -1
> >
> > like the test is expecting.
> >
> > I believe they are equivalent (0xffffffff) but I am not sure what it
> > is about my targets (mips-mti-elf and mips-mti-linux-gnu) that would
> > make this different from yours. Should the tests be modified to allow
> > either output?
>
> Maciej, have you had chance to look at this yet?
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.
This has passed mips-linux-gnu regression testing on a 32-bit host, but I
can't regression-test a 64-bit host easily -- Steve, can you please verify
that this change indeed works for you? Richard, OK to apply assuming that
it does?
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.
Maciej
gcc-mips-nan2008-test-fix.diff
Index: gcc-fsf-trunk-quilt/gcc/testsuite/gcc.target/mips/nan-legacy.c
===================================================================
--- gcc-fsf-trunk-quilt.orig/gcc/testsuite/gcc.target/mips/nan-legacy.c 2013-08-13 14:18:50.008738612 +0100
+++ gcc-fsf-trunk-quilt/gcc/testsuite/gcc.target/mips/nan-legacy.c 2013-08-13 14:22:49.568772451 +0100
@@ -4,4 +4,4 @@
double d = __builtin_nan ("");
/* { dg-final { scan-assembler "\t\\.nan\tlegacy\n" } } */
-/* { dg-final { scan-assembler "\t\\.word\t2146959359\n\t\\.word\t-1\n" } } */
+/* { dg-final { scan-assembler "\t\\.word\t2146959359\n\t\\.word\t(?:-1|4294967295)\n" } } */
Index: gcc-fsf-trunk-quilt/gcc/testsuite/gcc.target/mips/nans-legacy.c
===================================================================
--- gcc-fsf-trunk-quilt.orig/gcc/testsuite/gcc.target/mips/nans-legacy.c 2013-08-13 14:18:50.008738612 +0100
+++ gcc-fsf-trunk-quilt/gcc/testsuite/gcc.target/mips/nans-legacy.c 2013-08-13 14:22:49.568772451 +0100
@@ -4,4 +4,4 @@
double ds = __builtin_nans ("");
/* { dg-final { scan-assembler "\t\\.nan\tlegacy\n" } } */
-/* { dg-final { scan-assembler "\t\\.word\t2147483647\n\t\\.word\t-1\n" } } */
+/* { dg-final { scan-assembler "\t\\.word\t2147483647\n\t\\.word\t(?:-1|4294967295)\n" } } */