From 58307649fb51a3a6adc29a8659d3301393f24671 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Wed, 7 Dec 2016 01:16:36 +0000 Subject: Fix hypot sNaN handling (bug 20940). TS 18661-1 generally defines libm functions taking sNaN arguments to return qNaN and raise "invalid", even for the cases where a corresponding qNaN argument would not result in a qNaN return. This includes hypot with one argument being an infinity and the other being an sNaN. This patch duly fixes hypot implementatations in glibc (generic and powerpc) to ensure qNaN, computed by arithmetic on the arguments, is returned in that case. Various implementations do their checks for infinities and NaNs inline by manipulating the representations of the arguments. For simplicity, this patch just uses issignaling to check for sNaN arguments. This could be inlined like the existing code (with due care about reversed quiet NaN conventions, for implementations where that is relevant), but given that all these checks are in cases where it's already known at least one argument is not finite, which should be the uncommon case, that doesn't seem worthwhile unless performance issues are observed in practice. Tested for x86_64, x86, mips64 and powerpc. [BZ #20940] * sysdeps/ieee754/dbl-64/e_hypot.c (__ieee754_hypot): Do not return Inf for arguments Inf and sNaN. * sysdeps/ieee754/flt-32/e_hypotf.c (__ieee754_hypotf): Likewise. * sysdeps/ieee754/ldbl-128/e_hypotl.c (__ieee754_hypotl): Likewise. * sysdeps/ieee754/ldbl-128ibm/e_hypotl.c (__ieee754_hypotl): Likewise. * sysdeps/ieee754/ldbl-96/e_hypotl.c (__ieee754_hypotl): Likewise. * sysdeps/powerpc/fpu/e_hypot.c (TEST_INF_NAN): Do not return Inf for arguments Inf and sNaN. When returning a NaN, compute it by arithmetic on the arguments. * sysdeps/powerpc/fpu/e_hypotf.c (TEST_INF_NAN): Likewise. * math/libm-test.inc (pow_test_data): Add tests of sNaN arguments. --- sysdeps/ieee754/ldbl-96/e_hypotl.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'sysdeps/ieee754/ldbl-96') diff --git a/sysdeps/ieee754/ldbl-96/e_hypotl.c b/sysdeps/ieee754/ldbl-96/e_hypotl.c index ee3a07055b..6b55b6d8ee 100644 --- a/sysdeps/ieee754/ldbl-96/e_hypotl.c +++ b/sysdeps/ieee754/ldbl-96/e_hypotl.c @@ -68,6 +68,8 @@ long double __ieee754_hypotl(long double x, long double y) u_int32_t exp __attribute__ ((unused)); u_int32_t high,low; w = a+b; /* for sNaN */ + if (issignaling (a) || issignaling (b)) + return w; GET_LDOUBLE_WORDS(exp,high,low,a); if(((high&0x7fffffff)|low)==0) w = a; GET_LDOUBLE_WORDS(exp,high,low,b); -- cgit v1.2.3