Re: MIPS tests (nan-legacy.c and nans-legacy.c) failing

["Maciej W. Rozycki" <macro@codesourcery.com>]

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" } } */