Fix ldbl-96 lroundl just below powers of 2 (bug 19071).

The ldbl-96 version of lroundl is incorrect for systems with 64-bit
long when the argument's absolute value is just below a power of 2,
2^32 or more, and rounds up to the next integer; in such cases, it
returns 0.  The problem is incrementing the high part of the mantissa
loses the high bit of the value (which is not an issue for any other
floating-point format, and is handled specially in lround when the bit
corresponding to 0.5 was in the high part rather than the low part).

This patch fixes this in a similar way to that used in llroundl:
storing the high part in an unsigned long variable before incrementing
it, so problems cannot occur in the case when this code is reachable.
I improved test coverage for both lround and llround by making them
use the same test inputs (appropriately conditioned on the size of
long in the lround case) - complete with the same comments, to make
comparison as easy as possible.  (This test coverage improvement was
how I found the lroundl bug.)

Tested for x86_64 and x86.

	[BZ #19071]
	* sysdeps/ieee754/ldbl-96/s_lroundl.c (__lroundl): Use unsigned
	long int variable to store possibly incremented high part of
	mantissa.
	* math/libm-test.inc (lround_test_data): Add tests used for
	llround.  Use [LONG_MAX > 0x7fffffff] consistently as condition
	for tests requiring 64-bit long.  Do not condition tests on
	[TEST_FLOAT] unnecessarily.
	(llround_test_data): Add tests used for lround.  Add another
	expectation for the "inexact" exception.  Do not condition tests
	on [TEST_FLOAT] unnecessarily.
This commit is contained in:
Joseph Myers 2015-10-05 22:53:50 +00:00
parent a8133e197e
commit cec7d28af8
4 changed files with 178 additions and 15 deletions

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@ -1,5 +1,17 @@
2015-10-05 Joseph Myers <joseph@codesourcery.com>
[BZ #19071]
* sysdeps/ieee754/ldbl-96/s_lroundl.c (__lroundl): Use unsigned
long int variable to store possibly incremented high part of
mantissa.
* math/libm-test.inc (lround_test_data): Add tests used for
llround. Use [LONG_MAX > 0x7fffffff] consistently as condition
for tests requiring 64-bit long. Do not condition tests on
[TEST_FLOAT] unnecessarily.
(llround_test_data): Add tests used for lround. Add another
expectation for the "inexact" exception. Do not condition tests
on [TEST_FLOAT] unnecessarily.
[BZ #887]
[BZ #19049]
[BZ #19050]

3
NEWS
View File

@ -17,7 +17,8 @@ Version 2.23
18757, 18778, 18781, 18787, 18789, 18790, 18795, 18796, 18803, 18820,
18823, 18824, 18825, 18857, 18863, 18870, 18872, 18873, 18875, 18887,
18921, 18951, 18952, 18956, 18961, 18966, 18967, 18969, 18970, 18977,
18980, 18981, 18985, 19003, 19016, 19032, 19046, 19049, 19050, 19059.
18980, 18981, 18985, 19003, 19016, 19032, 19046, 19049, 19050, 19059,
19071.
* The obsolete header <regexp.h> has been removed. Programs that require
this header must be updated to use <regex.h> instead.

View File

@ -8099,25 +8099,168 @@ static const struct test_f_l_data lround_test_data[] =
TEST_f_l (lround, 22514.5, 22515, ERRNO_UNCHANGED),
TEST_f_l (lround, -22514.5, -22515, ERRNO_UNCHANGED),
TEST_f_l (lround, 1071930.0008, 1071930, ERRNO_UNCHANGED),
TEST_f_l (lround, 2097152.5, 2097153, ERRNO_UNCHANGED),
TEST_f_l (lround, -2097152.5, -2097153, ERRNO_UNCHANGED),
#ifndef TEST_FLOAT
TEST_f_l (lround, 1073741824.01, 1073741824, ERRNO_UNCHANGED),
# if LONG_MAX > 281474976710656
# if LONG_MAX > 0x7fffffff
TEST_f_l (lround, 34359738368.5, 34359738369ll, ERRNO_UNCHANGED),
TEST_f_l (lround, -34359738368.5, -34359738369ll, ERRNO_UNCHANGED),
TEST_f_l (lround, -3.65309740835E17, -365309740835000000LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_l (lround, 281474976710656.025, 281474976710656, ERRNO_UNCHANGED),
TEST_f_l (lround, 18014398509481974, 18014398509481974, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
# endif
TEST_f_l (lround, 2097152.5, 2097153, ERRNO_UNCHANGED),
TEST_f_l (lround, -2097152.5, -2097153, ERRNO_UNCHANGED),
#endif
/* Test boundary conditions. */
/* 0x1FFFFF */
TEST_f_l (lround, 2097151.0, 2097151LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
/* 0x800000 */
TEST_f_l (lround, 8388608.0, 8388608LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
/* 0x1000000 */
TEST_f_l (lround, 16777216.0, 16777216LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
#if LONG_MAX > 0x7fffffff
/* 0x20000000000 */
TEST_f_l (lround, 2199023255552.0, 2199023255552LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
/* 0x40000000000 */
TEST_f_l (lround, 4398046511104.0, 4398046511104LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
/* 0x1000000000000 */
TEST_f_l (lround, 281474976710656.0, 281474976710656LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
/* 0x10000000000000 */
TEST_f_l (lround, 4503599627370496.0, 4503599627370496LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
/* 0x10000080000000 */
TEST_f_l (lround, 4503601774854144.0, 4503601774854144LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
/* 0x20000000000000 */
TEST_f_l (lround, 9007199254740992.0, 9007199254740992LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
/* 0x80000000000000 */
TEST_f_l (lround, 36028797018963968.0, 36028797018963968LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
/* 0x100000000000000 */
TEST_f_l (lround, 72057594037927936.0, 72057594037927936LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
#endif
#ifndef TEST_FLOAT
# if LONG_MAX > 0x7fffffff
/* 0x100000000 */
TEST_f_l (lround, 4294967295.5, 4294967296LL, ERRNO_UNCHANGED),
/* 0x200000000 */
TEST_f_l (lround, 8589934591.5, 8589934592LL, ERRNO_UNCHANGED),
# endif
/* nextafter(0.5,-1) */
TEST_f_l (lround, 0x1.fffffffffffffp-2, 0, ERRNO_UNCHANGED),
/* nextafter(-0.5,1) */
TEST_f_l (lround, -0x1.fffffffffffffp-2, 0, ERRNO_UNCHANGED),
#else
/* nextafter(0.5,-1) */
# if LONG_MAX > 0x7fffffff
/* On PowerPC an exponent of '52' is the largest incrementally
* representable sequence of whole-numbers in the 'double' range. We test
* lround to make sure that a guard bit set during the lround operation
* hasn't forced an erroneous shift giving us an incorrect result. The odd
* numbers between +-(2^52+1 and 2^53-1) are affected since they have the
* rightmost bit set. */
/* +-(2^52+1) */
TEST_f_l (lround, 0x1.0000000000001p+52,4503599627370497LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_l (lround, -0x1.0000000000001p+52,-4503599627370497LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
/* +-(2^53-1): Input is the last (positive and negative) incrementally
* representable whole-number in the 'double' range that might round
* erroneously. */
TEST_f_l (lround, 0x1.fffffffffffffp+52, 9007199254740991LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_l (lround, -0x1.fffffffffffffp+52, -9007199254740991LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
# endif
#endif
TEST_f_l (lround, 0x1.fffffp-2, 0, ERRNO_UNCHANGED),
/* nextafter(-0.5,1) */
/* nextafter(0.5,-1) */
TEST_f_l (lround, 0x1.fffffep-2, 0, ERRNO_UNCHANGED),
TEST_f_l (lround, -0x1.fffffp-2, 0, ERRNO_UNCHANGED),
/* nextafter(-0.5,1) */
TEST_f_l (lround, -0x1.fffffep-2, 0, ERRNO_UNCHANGED),
TEST_f_l (lround, 0x1.fffffep+23, 16777215, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_l (lround, -0x1.fffffep+23, -16777215, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
/* As above, on PowerPC an exponent of '23' is the largest incrementally
* representable sequence of whole-numbers in the 'float' range.
* Likewise, numbers between +-(2^23+1 and 2^24-1) are affected. */
TEST_f_l (lround, 0x1.000002p+23,8388609, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_l (lround, -0x1.000002p+23,-8388609, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_l (lround, 0x1.fffffep+23, 16777215, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_l (lround, -0x1.fffffep+23, -16777215, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
#if LONG_MAX > 0x7fffffff
# ifdef TEST_LDOUBLE
/* The input can only be represented in long double. */
TEST_f_l (lround, 4503599627370495.5L, 4503599627370496LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 4503599627370496.25L, 4503599627370496LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 4503599627370496.5L, 4503599627370497LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 4503599627370496.75L, 4503599627370497LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 4503599627370497.5L, 4503599627370498LL, ERRNO_UNCHANGED),
# if LDBL_MANT_DIG > 100
TEST_f_l (lround, 4503599627370495.4999999999999L, 4503599627370495LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 4503599627370496.4999999999999L, 4503599627370496LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 4503599627370497.4999999999999L, 4503599627370497LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 4503599627370494.5000000000001L, 4503599627370495LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 4503599627370495.5000000000001L, 4503599627370496LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 4503599627370496.5000000000001L, 4503599627370497LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -4503599627370495.4999999999999L, -4503599627370495LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -4503599627370496.4999999999999L, -4503599627370496LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -4503599627370497.4999999999999L, -4503599627370497LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -4503599627370494.5000000000001L, -4503599627370495LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -4503599627370495.5000000000001L, -4503599627370496LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -4503599627370496.5000000000001L, -4503599627370497LL, ERRNO_UNCHANGED),
# endif
TEST_f_l (lround, -4503599627370495.5L, -4503599627370496LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -4503599627370496.25L, -4503599627370496LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -4503599627370496.5L, -4503599627370497LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -4503599627370496.75L, -4503599627370497LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -4503599627370497.5L, -4503599627370498LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9007199254740991.5L, 9007199254740992LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9007199254740992.25L, 9007199254740992LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9007199254740992.5L, 9007199254740993LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9007199254740992.75L, 9007199254740993LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9007199254740993.5L, 9007199254740994LL, ERRNO_UNCHANGED),
# if LDBL_MANT_DIG > 100
TEST_f_l (lround, 9007199254740991.4999999999999L, 9007199254740991LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9007199254740992.4999999999999L, 9007199254740992LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9007199254740993.4999999999999L, 9007199254740993LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9007199254740991.5000000000001L, 9007199254740992LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9007199254740992.5000000000001L, 9007199254740993LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9007199254740993.5000000000001L, 9007199254740994LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -9007199254740991.4999999999999L, -9007199254740991LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -9007199254740992.4999999999999L, -9007199254740992LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -9007199254740993.4999999999999L, -9007199254740993LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -9007199254740991.5000000000001L, -9007199254740992LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -9007199254740992.5000000000001L, -9007199254740993LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -9007199254740993.5000000000001L, -9007199254740994LL, ERRNO_UNCHANGED),
# endif
TEST_f_l (lround, -9007199254740991.5L, -9007199254740992LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -9007199254740992.25L, -9007199254740992LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -9007199254740992.5L, -9007199254740993LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -9007199254740992.75L, -9007199254740993LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -9007199254740993.5L, -9007199254740994LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 72057594037927935.5L, 72057594037927936LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 72057594037927936.25L, 72057594037927936LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 72057594037927936.5L, 72057594037927937LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 72057594037927936.75L, 72057594037927937LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 72057594037927937.5L, 72057594037927938LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -72057594037927935.5L, -72057594037927936LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -72057594037927936.25L, -72057594037927936LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -72057594037927936.5L, -72057594037927937LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -72057594037927936.75L, -72057594037927937LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -72057594037927937.5L, -72057594037927938LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9223372036854775806.25L, 9223372036854775806LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -9223372036854775806.25L, -9223372036854775806LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9223372036854775806.5L, 9223372036854775807LL, ERRNO_UNCHANGED),
TEST_f_l (lround, -9223372036854775806.5L, -9223372036854775807LL, ERRNO_UNCHANGED),
TEST_f_l (lround, 9223372036854775807.0L, 9223372036854775807LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_l (lround, -9223372036854775807.0L, -9223372036854775807LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
# endif
#endif
};
@ -8147,12 +8290,15 @@ static const struct test_f_L_data llround_test_data[] =
TEST_f_L (llround, 22514.5, 22515, ERRNO_UNCHANGED),
TEST_f_L (llround, -22514.5, -22515, ERRNO_UNCHANGED),
TEST_f_L (llround, 1071930.0008, 1071930, ERRNO_UNCHANGED),
#ifndef TEST_FLOAT
TEST_f_L (llround, 2097152.5, 2097153, ERRNO_UNCHANGED),
TEST_f_L (llround, -2097152.5, -2097153, ERRNO_UNCHANGED),
#ifndef TEST_FLOAT
TEST_f_L (llround, 1073741824.01, 1073741824, ERRNO_UNCHANGED),
TEST_f_L (llround, 34359738368.5, 34359738369ll, ERRNO_UNCHANGED),
TEST_f_L (llround, -34359738368.5, -34359738369ll, ERRNO_UNCHANGED),
TEST_f_L (llround, -3.65309740835E17, -365309740835000000LL, ERRNO_UNCHANGED),
TEST_f_L (llround, -3.65309740835E17, -365309740835000000LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_L (llround, 281474976710656.025, 281474976710656, ERRNO_UNCHANGED),
TEST_f_L (llround, 18014398509481974, 18014398509481974, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
#endif
/* Test boundary conditions. */
@ -8203,11 +8349,15 @@ static const struct test_f_L_data llround_test_data[] =
* erroneously. */
TEST_f_L (llround, 0x1.fffffffffffffp+52, 9007199254740991LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_L (llround, -0x1.fffffffffffffp+52, -9007199254740991LL, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
#else
#endif
TEST_f_L (llround, 0x1.fffffp-2, 0, ERRNO_UNCHANGED),
/* nextafter(0.5,-1) */
TEST_f_L (llround, 0x1.fffffep-2, 0, ERRNO_UNCHANGED),
TEST_f_L (llround, -0x1.fffffp-2, 0, ERRNO_UNCHANGED),
/* nextafter(-0.5,1) */
TEST_f_L (llround, -0x1.fffffep-2, 0, ERRNO_UNCHANGED),
TEST_f_L (llround, 0x1.fffffep+23, 16777215, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_L (llround, -0x1.fffffep+23, -16777215, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
/* As above, on PowerPC an exponent of '23' is the largest incrementally
* representable sequence of whole-numbers in the 'float' range.
* Likewise, numbers between +-(2^23+1 and 2^24-1) are affected. */
@ -8215,8 +8365,6 @@ static const struct test_f_L_data llround_test_data[] =
TEST_f_L (llround, -0x1.000002p+23,-8388609, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_L (llround, 0x1.fffffep+23, 16777215, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
TEST_f_L (llround, -0x1.fffffep+23, -16777215, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
#endif
#ifdef TEST_LDOUBLE
/* The input can only be represented in long double. */

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@ -58,13 +58,15 @@ __lroundl (long double x)
else
{
u_int32_t j = i1 + (0x80000000 >> (j0 - 31));
unsigned long int ures = i0;
if (j < i1)
++i0;
++ures;
if (j0 == 31)
result = (long int) i0;
result = ures;
else
result = ((long int) i0 << (j0 - 31)) | (j >> (63 - j0));
result = (ures << (j0 - 31)) | (j >> (63 - j0));
}
}
else