* [PATCH] Fix strtold with IBM long double
@ 2007-06-05 15:40 Jakub Jelinek
0 siblings, 0 replies; only message in thread
From: Jakub Jelinek @ 2007-06-05 15:40 UTC (permalink / raw)
To: Ulrich Drepper, Steven Munroe; +Cc: Glibc hackers
Hi!
As the adjusted tst-sprintf2 testcase shows there were a bunch of bugs
in strtold/*scanf %La on ppc{,64}.
2007-06-05 Jakub Jelinek <jakub@redhat.com>
* sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c
(__mpn_construct_long_double): Fix conversion where result ought
to be smaller than __LDBL_MIN__, or the low double should be
denormal. Fix decision where to negate low double - honor round
to even rules.
* stdio-common/tst-sprintf2.c: Include string.h.
(COMPARE_LDBL): Define.
(TEST): Also test whether a string hexadecimal float representation
can be parsed back to the number.
(main): Add a couple of further tests.
--- libc/sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c.jj 2006-01-28 01:07:25.000000000 +0100
+++ libc/sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c 2007-06-05 15:37:15.000000000 +0200
@@ -1,4 +1,4 @@
-/* Copyright (C) 1995, 1996, 1997, 1998, 1999, 2002, 2003, 2004, 2006
+/* Copyright (C) 1995, 1996, 1997, 1998, 1999, 2002, 2003, 2004, 2006, 2007
Free Software Foundation, Inc.
This file is part of the GNU C Library.
@@ -31,19 +31,20 @@ long double
__mpn_construct_long_double (mp_srcptr frac_ptr, int expt, int sign)
{
union ibm_extended_long_double u;
- unsigned long hidden2, lzcount;
+ unsigned long lzcount;
unsigned long long hi, lo;
+ int exponent2;
u.ieee.negative = sign;
u.ieee.negative2 = sign;
u.ieee.exponent = expt + IBM_EXTENDED_LONG_DOUBLE_BIAS;
- u.ieee.exponent2 = expt - 53 + IBM_EXTENDED_LONG_DOUBLE_BIAS;
+ u.ieee.exponent2 = 0;
+ exponent2 = expt - 53 + IBM_EXTENDED_LONG_DOUBLE_BIAS;
#if BITS_PER_MP_LIMB == 32
/* The low order 53 bits (52 + hidden) go into the lower double */
lo = frac_ptr[0];
lo |= (frac_ptr[1] & ((1LL << (53 - 32)) - 1)) << 32;
- hidden2 = (frac_ptr[1] >> (52 - 32)) & ((mp_limb_t) 1);
/* The high order 53 bits (52 + hidden) go into the upper double */
hi = (frac_ptr[1] >> (53 - 32)) & ((1 << 11) - 1);
hi |= ((unsigned long long) frac_ptr[2]) << 11;
@@ -51,7 +52,6 @@ __mpn_construct_long_double (mp_srcptr f
#elif BITS_PER_MP_LIMB == 64
/* The low order 53 bits (52 + hidden) go into the lower double */
lo = frac_ptr[0] & (((mp_limb_t) 1 << 53) - 1);
- hidden2 = (frac_ptr[0] >> 52) & ((mp_limb_t) 1);
/* The high order 53 bits (52 + hidden) go into the upper double */
hi = (frac_ptr[0] >> 53) & (((mp_limb_t) 1 << 11) - 1);
hi |= (frac_ptr[1] << 11);
@@ -59,14 +59,62 @@ __mpn_construct_long_double (mp_srcptr f
#error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
#endif
+ if ((hi & (1LL << 52)) == 0 && (hi | lo) != 0)
+ {
+ /* denormal number */
+ unsigned long long val = hi ? hi : lo;
+
+ if (sizeof (val) == sizeof (long))
+ lzcount = __builtin_clzl (val);
+ else if ((val >> 32) != 0)
+ lzcount = __builtin_clzl ((long) (val >> 32));
+ else
+ lzcount = __builtin_clzl ((long) val) + 32;
+ if (hi)
+ lzcount = lzcount - 11;
+ else
+ lzcount = lzcount + 42;
+
+ if (lzcount > u.ieee.exponent)
+ {
+ lzcount = u.ieee.exponent;
+ u.ieee.exponent = 0;
+ exponent2 -= lzcount;
+ }
+ else
+ {
+ u.ieee.exponent -= (lzcount - 1);
+ exponent2 -= (lzcount - 1);
+ }
+
+ if (lzcount <= 53)
+ {
+ hi = (hi << lzcount) | (lo >> (53 - lzcount));
+ lo = (lo << lzcount) & ((1LL << 53) - 1);
+ }
+ else
+ {
+ hi = lo << (lzcount - 53);
+ lo = 0;
+ }
+ }
+
if (lo != 0L)
{
/* hidden2 bit of low double controls rounding of the high double.
- If hidden2 is '1' then round up hi and adjust lo (2nd mantissa)
+ If hidden2 is '1' and either the explicit mantissa is non-zero
+ or hi is odd, then round up hi and adjust lo (2nd mantissa)
plus change the sign of the low double to compensate. */
- if (hidden2)
+ if ((lo & (1LL << 52)) != 0
+ && ((hi & 1) != 0 || (lo & ((1LL << 52) - 1))))
{
hi++;
+ if ((hi & ((1LL << 52) - 1)) == 0)
+ {
+ if ((hi & (1LL << 53)) != 0)
+ hi -= 1LL << 52;
+ u.ieee.exponent++;
+ }
u.ieee.negative2 = !sign;
lo = (1LL << 53) - lo;
}
@@ -85,17 +133,18 @@ __mpn_construct_long_double (mp_srcptr f
if (lzcount > 0)
{
lo = lo << lzcount;
- u.ieee.exponent2 = u.ieee.exponent2 - lzcount;
+ exponent2 = exponent2 - lzcount;
}
+ if (exponent2 > 0)
+ u.ieee.exponent2 = exponent2;
+ else
+ lo >>= 1 - exponent2;
}
else
- {
- u.ieee.negative2 = 0;
- u.ieee.exponent2 = 0;
- }
+ u.ieee.negative2 = 0;
u.ieee.mantissa3 = lo & 0xffffffffLL;
- u.ieee.mantissa2 = (lo >> 32) & 0xffffff;
+ u.ieee.mantissa2 = (lo >> 32) & 0xfffff;
u.ieee.mantissa1 = hi & 0xffffffffLL;
u.ieee.mantissa0 = (hi >> 32) & ((1LL << (LDBL_MANT_DIG - 86)) - 1);
--- libc/stdio-common/tst-sprintf2.c.jj 2007-06-04 14:04:35.000000000 +0200
+++ libc/stdio-common/tst-sprintf2.c 2007-06-05 15:56:55.000000000 +0200
@@ -1,14 +1,22 @@
#include <float.h>
#include <math.h>
#include <stdio.h>
+#include <string.h>
int
main (void)
{
- volatile union { long double l; long long x[2]; } u;
+ volatile union { long double l; long long x[2]; } u, v;
char buf[64];
int result = 0;
+#if LDBL_MANT_DIG == 106 || LDBL_MANT_DIG == 113
+# define COMPARE_LDBL(u, v) \
+ ((u).l == (v).l && (u).x[0] == (v).x[0] && (u).x[1] == (v).x[1])
+#else
+# define COMPARE_LDBL(u, v) ((u).l == (v).l)
+#endif
+
#define TEST(val) \
do \
{ \
@@ -19,6 +27,12 @@ main (void)
printf ("Error on line %d: %s != %s\n", __LINE__, buf, #val); \
result = 1; \
} \
+ if (sscanf (#val, "%La", &v.l) != 1 || !COMPARE_LDBL (u, v)) \
+ { \
+ printf ("Error sscanf on line %d: %La != %La\n", __LINE__, \
+ u.l, v.l); \
+ result = 1; \
+ } \
/* printf ("%s %La %016Lx %016Lx\n", #val, u.l, u.x[0], u.x[1]); */ \
} \
while (0)
@@ -54,6 +68,15 @@ main (void)
TEST (0x1.23456789abcdef123456789abc8p+64L);
TEST (0x1.23456789abcde7123456789abc8p+64L);
TEST (0x1.123456789abcdef123456789p-969L);
+# if LDBL_MANT_DIG == 106
+ TEST (-0x1.2d71957cc1263bbbeb1d365f1e8p-969L);
+ TEST (0x1.23456789abcdef0123456789abp-970L);
+ TEST (0x1.579bde02468acp-1001L);
+ TEST (0x0.abcdef0123456p-1022L);
+ TEST (0x1.abcdef0123456p-1022L);
+ TEST (0x1.abcdef012345678p-1014L);
+ TEST (0x1.abcdef0123456f8p-1014L);
+# endif
#endif
return result;
}
Jakub
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2007-06-05 15:40 [PATCH] Fix strtold with IBM long double Jakub Jelinek
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