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t_fenv: Use volatile intermediate to force rounding to double. 

See comment for details about why this is necessary.

Should fix these tests on i386 (and perhaps m68k too).

PR port-mips/57680

XXX pullup-10
This commit is contained in:
riastradh 2023-11-06 13:48:00 +00:00
parent 6307b04a74
commit 519833e0d7
1 changed files with 15 additions and 4 deletions
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19
tests/lib/libm/t_fenv.c
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@ -1,4 +1,4 @@
/* $NetBSD: t_fenv.c,v 1.11 2023/11/05 21:13:06 riastradh Exp $ */
/* $NetBSD: t_fenv.c,v 1.12 2023/11/06 13:48:00 riastradh Exp $ */
/*-
* Copyright (c) 2014 The NetBSD Foundation, Inc.
@ -29,7 +29,7 @@
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: t_fenv.c,v 1.11 2023/11/05 21:13:06 riastradh Exp $");
__RCSID("$NetBSD: t_fenv.c,v 1.12 2023/11/06 13:48:00 riastradh Exp $");
#include <atf-c.h>
@ -114,8 +114,19 @@ static void
checkrounding(int feround, const char *name)
{
volatile double ulp1 = DBL_EPSILON;
double y1 = -1 + ulp1/4;
double y2 = 1 + 3*(ulp1/2);
/*
* XXX These must be volatile to force rounding to double when
* the intermediate quantities are evaluated in long double
* precision, e.g. on 32-bit x86 with x87 long double. Under
* the C standard (C99, C11, C17, &c.), cast and assignment
* operators are required to remove all extra range and
* precision, i.e., round double to long double. But we build
* this code with -std=gnu99, which diverges from this
* requirement -- unless you add a volatile qualifier.
*/
volatile double y1 = -1 + ulp1/4;
volatile double y2 = 1 + 3*(ulp1/2);
switch (feround) {
case FE_TONEAREST: {