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Fix spurious underflows from pow with results close to 1 (bug 14811).
This commit is contained in:
Joseph Myers
parent
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commit
60e235ee2a
16
ChangeLog
16
ChangeLog
@ -1,3 +1,19 @@
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2012-11-07 Joseph Myers <joseph@codesourcery.com>
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[BZ #14811]
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* sysdeps/i386/fpu/e_powl.S (pm79): New object.
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(__ieee754_powl): Saturate nonzero exponents with absolute value
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below 0x1p-79 to +/- 0x1p-79.
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* sysdeps/ieee754/dbl-64/e_pow.c (__ieee754_pow): Saturate nonzero
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exponents with absolute value below 0x1p-64 to +/- 0x1p-64.
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* sysdeps/ieee754/flt-32/e_powf.c (__ieee754_powf): Saturate
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nonzero exponents with absolute value below 0x1p-32 to +/-
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0x1p-32.
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* sysdeps/x86_64/fpu/e_powl.S (pm79): New object.
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(__ieee754_powl): Saturate nonzero exponents with absolute value
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below 0x1p-79 to +/- 0x1p-79.
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* math/libm-test.inc (pow_test): Add more tests.
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2012-11-07 Andreas Krebbel <Andreas.Krebbel@de.ibm.com>
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* sysdeps/s390/dl-procinfo.c (_dl_s390_cap_flags): Sync
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2
NEWS
2
NEWS
@ -18,7 +18,7 @@ Version 2.17
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14518, 14519, 14530, 14532, 14538, 14543, 14544, 14545, 14557, 14562,
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14568, 14576, 14579, 14583, 14587, 14595, 14602, 14610, 14621, 14638,
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14645, 14648, 14652, 14660, 14661, 14669, 14683, 14694, 14716, 14743,
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14767, 14783, 14784, 14785, 14793, 14796, 14797, 14801, 14805.
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14767, 14783, 14784, 14785, 14793, 14796, 14797, 14801, 14805, 14811.
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* Support for STT_GNU_IFUNC symbols added for s390 and s390x.
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Optimized versions of memcpy, memset, and memcmp added for System z10 and
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@ -7743,10 +7743,12 @@ pow_test (void)
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TEST_ff_f (pow, plus_infty, 1e-7L, plus_infty);
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TEST_ff_f (pow, plus_infty, 1, plus_infty);
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TEST_ff_f (pow, plus_infty, 1e7L, plus_infty);
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TEST_ff_f (pow, plus_infty, min_subnorm_value, plus_infty);
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TEST_ff_f (pow, plus_infty, -1e-7L, 0);
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TEST_ff_f (pow, plus_infty, -1, 0);
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TEST_ff_f (pow, plus_infty, -1e7L, 0);
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TEST_ff_f (pow, plus_infty, -min_subnorm_value, 0);
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TEST_ff_f (pow, minus_infty, 1, minus_infty);
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TEST_ff_f (pow, minus_infty, 11, minus_infty);
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@ -7759,6 +7761,7 @@ pow_test (void)
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TEST_ff_f (pow, minus_infty, 1.1L, plus_infty);
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TEST_ff_f (pow, minus_infty, 11.1L, plus_infty);
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TEST_ff_f (pow, minus_infty, 1001.1L, plus_infty);
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TEST_ff_f (pow, minus_infty, min_subnorm_value, plus_infty);
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TEST_ff_f (pow, minus_infty, -1, minus_zero);
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TEST_ff_f (pow, minus_infty, -11, minus_zero);
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@ -7771,6 +7774,7 @@ pow_test (void)
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TEST_ff_f (pow, minus_infty, -1.1L, 0);
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TEST_ff_f (pow, minus_infty, -11.1L, 0);
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TEST_ff_f (pow, minus_infty, -1001.1L, 0);
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TEST_ff_f (pow, minus_infty, -min_subnorm_value, 0);
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#endif
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TEST_ff_f (pow, nan_value, nan_value, nan_value);
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@ -7793,6 +7797,8 @@ pow_test (void)
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TEST_ff_f (pow, nan_value, minus_infty, nan_value);
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TEST_ff_f (pow, nan_value, 2.5, nan_value);
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TEST_ff_f (pow, nan_value, -2.5, nan_value);
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TEST_ff_f (pow, nan_value, min_subnorm_value, nan_value);
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TEST_ff_f (pow, nan_value, -min_subnorm_value, nan_value);
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TEST_ff_f (pow, 1, plus_infty, 1);
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TEST_ff_f (pow, -1, plus_infty, 1);
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@ -7806,6 +7812,8 @@ pow_test (void)
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TEST_ff_f (pow, 1, 0x1p63L, 1);
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TEST_ff_f (pow, 1, 0x1p64L, 1);
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TEST_ff_f (pow, 1, 0x1p72L, 1);
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TEST_ff_f (pow, 1, min_subnorm_value, 1);
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TEST_ff_f (pow, 1, -min_subnorm_value, 1);
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/* pow (x, +-0) == 1. */
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TEST_ff_f (pow, plus_infty, 0, 1);
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@ -7825,6 +7833,10 @@ pow_test (void)
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TEST_ff_f (pow, -0.1L, -1.1L, nan_value, INVALID_EXCEPTION);
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TEST_ff_f (pow, -10.1L, 1.1L, nan_value, INVALID_EXCEPTION);
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TEST_ff_f (pow, -10.1L, -1.1L, nan_value, INVALID_EXCEPTION);
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TEST_ff_f (pow, -1.01L, min_subnorm_value, nan_value, INVALID_EXCEPTION);
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TEST_ff_f (pow, -1.01L, -min_subnorm_value, nan_value, INVALID_EXCEPTION);
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TEST_ff_f (pow, -1.0L, min_subnorm_value, nan_value, INVALID_EXCEPTION);
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TEST_ff_f (pow, -1.0L, -min_subnorm_value, nan_value, INVALID_EXCEPTION);
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errno = 0;
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TEST_ff_f (pow, 0, -1, plus_infty, DIVIDE_BY_ZERO_EXCEPTION);
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@ -7910,6 +7922,9 @@ pow_test (void)
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TEST_ff_f (pow, 0, -11.1L, plus_infty, DIVIDE_BY_ZERO_EXCEPTION);
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check_int ("errno for pow(0,-num) == ERANGE", errno, ERANGE, 0, 0, 0);
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errno = 0;
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TEST_ff_f (pow, 0, -min_subnorm_value, plus_infty, DIVIDE_BY_ZERO_EXCEPTION);
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check_int ("errno for pow(0,-num) == ERANGE", errno, ERANGE, 0, 0, 0);
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errno = 0;
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TEST_ff_f (pow, 0, -0x1p24, plus_infty, DIVIDE_BY_ZERO_EXCEPTION);
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check_int ("errno for pow(0,-num) == ERANGE", errno, ERANGE, 0, 0, 0);
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errno = 0;
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@ -7925,6 +7940,9 @@ pow_test (void)
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TEST_ff_f (pow, minus_zero, -11.1L, plus_infty, DIVIDE_BY_ZERO_EXCEPTION);
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check_int ("errno for pow(-0,-num) == ERANGE", errno, ERANGE, 0, 0, 0);
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errno = 0;
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TEST_ff_f (pow, minus_zero, -min_subnorm_value, plus_infty, DIVIDE_BY_ZERO_EXCEPTION);
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check_int ("errno for pow(-0,-num) == ERANGE", errno, ERANGE, 0, 0, 0);
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errno = 0;
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TEST_ff_f (pow, minus_zero, -0x1p24, plus_infty, DIVIDE_BY_ZERO_EXCEPTION);
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check_int ("errno for pow(-0,-num) == ERANGE", errno, ERANGE, 0, 0, 0);
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errno = 0;
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@ -8114,12 +8132,14 @@ pow_test (void)
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TEST_ff_f (pow, 0.0, 0x1p24, 0.0);
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TEST_ff_f (pow, 0.0, 0x1p127, 0.0);
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TEST_ff_f (pow, 0.0, max_value, 0.0);
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TEST_ff_f (pow, 0.0, min_subnorm_value, 0.0);
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/* pow (-0, y) == +0 for y > 0 and not an odd integer. */
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TEST_ff_f (pow, minus_zero, 4, 0.0);
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TEST_ff_f (pow, minus_zero, 0x1p24, 0.0);
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TEST_ff_f (pow, minus_zero, 0x1p127, 0.0);
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TEST_ff_f (pow, minus_zero, max_value, 0.0);
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TEST_ff_f (pow, minus_zero, min_subnorm_value, 0.0);
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TEST_ff_f (pow, 16, 0.25L, 2);
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TEST_ff_f (pow, 0x1p64L, 0.125L, 256);
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@ -8407,6 +8427,15 @@ pow_test (void)
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TEST_ff_f (pow, 0x1.0000000000001p0L, -0x1.23456789abcdfp61L, 1.0118762747828234466621210689458255908670e-253L);
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#endif
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TEST_ff_f (pow, min_subnorm_value, min_subnorm_value, 1.0L);
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TEST_ff_f (pow, min_subnorm_value, -min_subnorm_value, 1.0L);
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TEST_ff_f (pow, max_value, min_subnorm_value, 1.0L);
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TEST_ff_f (pow, max_value, -min_subnorm_value, 1.0L);
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TEST_ff_f (pow, 0.99L, min_subnorm_value, 1.0L);
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TEST_ff_f (pow, 0.99L, -min_subnorm_value, 1.0L);
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TEST_ff_f (pow, 1.01L, min_subnorm_value, 1.0L);
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TEST_ff_f (pow, 1.01L, -min_subnorm_value, 1.0L);
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TEST_ff_f (pow, 2.0L, -100000.0L, plus_zero, UNDERFLOW_EXCEPTION);
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END (pow);
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@ -38,6 +38,9 @@ p64: .byte 0, 0, 0, 0, 0, 0, 0xf0, 0x43
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.type p78,@object
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p78: .byte 0, 0, 0, 0, 0, 0, 0xd0, 0x44
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ASM_SIZE_DIRECTIVE(p78)
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.type pm79,@object
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pm79: .byte 0, 0, 0, 0, 0, 0, 0, 0x3b
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ASM_SIZE_DIRECTIVE(pm79)
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.section .rodata.cst16,"aM",@progbits,16
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@ -120,9 +123,25 @@ ENTRY(__ieee754_powl)
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fucomp %st(1) // y : x
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fnstsw
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sahf
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jne 3f
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je 9f
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/* OK, we have an integer value for y. */
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// If y has absolute value at most 0x1p-79, then any finite
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// nonzero x will result in 1. Saturate y to those bounds to
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// avoid underflow in the calculation of y*log2(x).
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fld %st // y : y : x
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fabs // |y| : y : x
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fcompl MO(pm79) // y : x
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fnstsw
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sahf
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jnc 3f
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fstp %st(0) // pop y
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fldl MO(pm79) // 0x1p-79 : x
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testb $2, %dl
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jnz 3f // y > 0
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fchs // -0x1p-79 : x
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jmp 3f
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9: /* OK, we have an integer value for y. */
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popl %eax
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cfi_adjust_cfa_offset (-4)
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popl %edx
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@ -90,6 +90,10 @@ __ieee754_pow(double x, double y) {
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SET_RESTORE_ROUND (FE_TONEAREST);
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/* Avoid internal underflow for tiny y. The exact value of y does
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not matter if |y| <= 2**-64. */
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if (ABS (y) < 0x1p-64)
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y = y < 0 ? -0x1p-64 : 0x1p-64;
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z = log1(x,&aa,&error); /* x^y =e^(y log (X)) */
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t = y*134217729.0;
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y1 = t - (t-y);
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@ -141,6 +141,10 @@ __ieee754_powf(float x, float y)
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t2 = v-(t1-u);
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} else {
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float s2,s_h,s_l,t_h,t_l;
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/* Avoid internal underflow for tiny y. The exact value
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of y does not matter if |y| <= 2**-32. */
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if (iy < 0x2f800000)
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SET_FLOAT_WORD (y, (hy & 0x80000000) | 0x2f800000);
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n = 0;
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/* take care subnormal number */
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if(ix<0x00800000)
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@ -38,6 +38,9 @@ p64: .byte 0, 0, 0, 0, 0, 0, 0xf0, 0x43
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.type p78,@object
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p78: .byte 0, 0, 0, 0, 0, 0, 0xd0, 0x44
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ASM_SIZE_DIRECTIVE(p78)
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.type pm79,@object
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pm79: .byte 0, 0, 0, 0, 0, 0, 0, 0x3b
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ASM_SIZE_DIRECTIVE(pm79)
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.section .rodata.cst16,"aM",@progbits,16
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@ -110,9 +113,25 @@ ENTRY(__ieee754_powl)
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fistpll -8(%rsp) // y : x
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fildll -8(%rsp) // int(y) : y : x
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fucomip %st(1),%st // y : x
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jne 3f
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je 9f
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/* OK, we have an integer value for y. */
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// If y has absolute value at most 0x1p-79, then any finite
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// nonzero x will result in 1. Saturate y to those bounds to
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// avoid underflow in the calculation of y*log2(x).
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fldl MO(pm79) // 0x1p-79 : y : x
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fld %st(1) // y : 0x1p-79 : y : x
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fabs // |y| : 0x1p-79 : y : x
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fcomip %st(1), %st // 0x1p-79 : y : x
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fstp %st(0) // y : x
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jnc 3f
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fstp %st(0) // pop y
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fldl MO(pm79) // 0x1p-79 : x
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testb $2, %dl
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jnz 3f // y > 0
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fchs // -0x1p-79 : x
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jmp 3f
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9: /* OK, we have an integer value for y. */
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mov -8(%rsp),%eax
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mov -4(%rsp),%edx
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orl $0, %edx
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