From: Joseph Myers Date: Mon, 12 Jan 2015 22:34:58 +0000 (+0000) Subject: Fix ldbl-96 scalblnl for subnormal arguments (bug 17834). X-Git-Tag: glibc-2.21~58 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=34e93d6c76b7a6eaf94697a172b958704fd33396;p=thirdparty%2Fglibc.git Fix ldbl-96 scalblnl for subnormal arguments (bug 17834). The ldbl-96 implementation of scalblnl (used for x86_64 and ia64) is incorrect for subnormal arguments (this is a separate bug from bug 17803, which is about underflowing results). There are two problems with the adjustments of subnormal arguments: the "two63" variable multiplied by is actually 0x1p52L not 0x1p63L, so is insufficient to make values normal, and then GET_LDOUBLE_EXP(es,x), used to extract the new exponent, extracts it into a variable that isn't used, while the value taken to by the new exponent is wrongly taken from the high part of the mantissa before the adjustment (hx). This patch fixes both those problems and adds appropriate tests. Tested for x86_64. [BZ #17834] * sysdeps/ieee754/ldbl-96/s_scalblnl.c (two63): Change value to 0x1p63L. (__scalblnl): Get new exponent of adjusted subnormal value from ES not HX. * math/libm-test.inc (scalbn_test_data): Add more tests. (scalbln_test_data): Likewise. --- diff --git a/ChangeLog b/ChangeLog index d671b11533f..081e0b5f0f9 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,13 @@ +2015-01-12 Joseph Myers + + [BZ #17834] + * sysdeps/ieee754/ldbl-96/s_scalblnl.c (two63): Change value to + 0x1p63L. + (__scalblnl): Get new exponent of adjusted subnormal value from ES + not HX. + * math/libm-test.inc (scalbn_test_data): Add more tests. + (scalbln_test_data): Likewise. + 2015-01-12 Adhemerval Zanella Stefani Seibold diff --git a/NEWS b/NEWS index 35d397d1516..e5fb0a0c43f 100644 --- a/NEWS +++ b/NEWS @@ -17,7 +17,7 @@ Version 2.21 17633, 17634, 17635, 17647, 17653, 17657, 17658, 17664, 17665, 17668, 17682, 17717, 17719, 17722, 17723, 17724, 17725, 17732, 17733, 17744, 17745, 17746, 17747, 17748, 17775, 17777, 17780, 17781, 17782, 17791, - 17793, 17796, 17797, 17806 + 17793, 17796, 17797, 17806, 17834 * Added support for TSX lock elision of pthread mutexes on powerpc32, powerpc64 and powerpc64le. This may improve lock scaling of existing programs on diff --git a/math/libm-test.inc b/math/libm-test.inc index 8db1dd00a32..34f83c64f6e 100644 --- a/math/libm-test.inc +++ b/math/libm-test.inc @@ -9124,6 +9124,17 @@ static const struct test_fi_f_data scalbn_test_data[] = TEST_fi_f (scalbn, 1, 0L, 1, NO_INEXACT_EXCEPTION), + TEST_fi_f (scalbn, min_value / 2, 0, min_value / 2, NO_INEXACT_EXCEPTION), + TEST_fi_f (scalbn, -min_value / 2, 0, -min_value / 2, NO_INEXACT_EXCEPTION), + TEST_fi_f (scalbn, min_value / 2, 1, min_value, NO_INEXACT_EXCEPTION), + TEST_fi_f (scalbn, -min_value / 2, 1, -min_value, NO_INEXACT_EXCEPTION), + TEST_fi_f (scalbn, min_value * 0x0.ffffp0, 0, min_value * 0x0.ffffp0, NO_INEXACT_EXCEPTION), + TEST_fi_f (scalbn, -min_value * 0x0.ffffp0, 0, -min_value * 0x0.ffffp0, NO_INEXACT_EXCEPTION), + TEST_fi_f (scalbn, min_subnorm_value, 0, min_subnorm_value, NO_INEXACT_EXCEPTION), + TEST_fi_f (scalbn, -min_subnorm_value, 0, -min_subnorm_value, NO_INEXACT_EXCEPTION), + TEST_fi_f (scalbn, min_subnorm_value, MANT_DIG, min_value, NO_INEXACT_EXCEPTION), + TEST_fi_f (scalbn, -min_subnorm_value, MANT_DIG, -min_value, NO_INEXACT_EXCEPTION), + TEST_fi_f (scalbn, 1, INT_MAX, plus_oflow, INEXACT_EXCEPTION|OVERFLOW_EXCEPTION), TEST_fi_f (scalbn, 1, INT_MIN, plus_uflow, INEXACT_EXCEPTION|UNDERFLOW_EXCEPTION), TEST_fi_f (scalbn, max_value, INT_MAX, plus_oflow, INEXACT_EXCEPTION|OVERFLOW_EXCEPTION), @@ -9171,6 +9182,17 @@ static const struct test_fl_f_data scalbln_test_data[] = TEST_fl_f (scalbln, 1, 0L, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED), + TEST_fl_f (scalbln, min_value / 2, 0, min_value / 2, NO_INEXACT_EXCEPTION), + TEST_fl_f (scalbln, -min_value / 2, 0, -min_value / 2, NO_INEXACT_EXCEPTION), + TEST_fl_f (scalbln, min_value / 2, 1, min_value, NO_INEXACT_EXCEPTION), + TEST_fl_f (scalbln, -min_value / 2, 1, -min_value, NO_INEXACT_EXCEPTION), + TEST_fl_f (scalbln, min_value * 0x0.ffffp0, 0, min_value * 0x0.ffffp0, NO_INEXACT_EXCEPTION), + TEST_fl_f (scalbln, -min_value * 0x0.ffffp0, 0, -min_value * 0x0.ffffp0, NO_INEXACT_EXCEPTION), + TEST_fl_f (scalbln, min_subnorm_value, 0, min_subnorm_value, NO_INEXACT_EXCEPTION), + TEST_fl_f (scalbln, -min_subnorm_value, 0, -min_subnorm_value, NO_INEXACT_EXCEPTION), + TEST_fl_f (scalbln, min_subnorm_value, MANT_DIG, min_value, NO_INEXACT_EXCEPTION), + TEST_fl_f (scalbln, -min_subnorm_value, MANT_DIG, -min_value, NO_INEXACT_EXCEPTION), + TEST_fl_f (scalbln, 1, INT_MAX, plus_oflow, INEXACT_EXCEPTION|OVERFLOW_EXCEPTION|ERRNO_PLUS_OFLOW), TEST_fl_f (scalbln, 1, INT_MIN, plus_uflow, INEXACT_EXCEPTION|UNDERFLOW_EXCEPTION|ERRNO_PLUS_UFLOW), TEST_fl_f (scalbln, max_value, INT_MAX, plus_oflow, INEXACT_EXCEPTION|OVERFLOW_EXCEPTION|ERRNO_PLUS_OFLOW), diff --git a/sysdeps/ieee754/ldbl-96/s_scalblnl.c b/sysdeps/ieee754/ldbl-96/s_scalblnl.c index fca8470cdcf..5c2f38eafd3 100644 --- a/sysdeps/ieee754/ldbl-96/s_scalblnl.c +++ b/sysdeps/ieee754/ldbl-96/s_scalblnl.c @@ -25,7 +25,7 @@ #include static const long double -two63 = 4.50359962737049600000e+15, +two63 = 0x1p63L, twom63 = 1.08420217248550443400e-19, huge = 1.0e+4900L, tiny = 1.0e-4900L; @@ -40,7 +40,7 @@ __scalblnl (long double x, long int n) if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */ x *= two63; GET_LDOUBLE_EXP(es,x); - k = (hx&0x7fff) - 63; + k = (es&0x7fff) - 63; } if (__builtin_expect(k==0x7fff, 0)) return x+x; /* NaN or Inf */ if (__builtin_expect(n< -50000, 0))