From 0a2546cdaa4284cc6ed6af06835fd858ba341838 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Thu, 15 Dec 2016 23:52:18 +0000 Subject: Fix x86, x86_64 fmax, fmin sNaN handling, add tests (bug 20947). Various fmax and fmin function implementations mishandle sNaN arguments: (a) When both arguments are NaNs, the return value should be a qNaN, but sometimes it is an sNaN if at least one argument is an sNaN. (b) Under TS 18661-1 semantics, if either argument is an sNaN then the result should be a qNaN (whereas if one argument is a qNaN and the other is not a NaN, the result should be the non-NaN argument). Various implementations treat sNaNs like qNaNs here. This patch fixes the x86 and x86_64 versions (ignoring float and double for 32-bit x86 given the inability to reliably avoid the sNaN turning into a qNaN before it gets to the called function). Tests of sNaN inputs to these functions are added. Note on architecture versions I haven't changed for this issue: AArch64 already gets this right (it uses a hardware instruction with the correct semantics for both quiet and signaling NaNs) and does not need changes. It's possible Alpha, IA64, SPARC might need changes (this would be shown by the testsuite if so). Tested for x86_64 and x86 (both i686 and i586 builds, to cover the different x86 implementations). [BZ #20947] * sysdeps/i386/fpu/s_fmaxl.S (__fmaxl): Add the arguments when either is a signaling NaN. * sysdeps/i386/fpu/s_fminl.S (__fminl): Likewise. Make code follow fmaxl more closely. * sysdeps/i386/i686/fpu/s_fmaxl.S (__fmaxl): Add the arguments when either is a signaling NaN. * sysdeps/i386/i686/fpu/s_fminl.S (__fminl): Likewise. * sysdeps/x86_64/fpu/s_fmax.S (__fmax): Likewise. * sysdeps/x86_64/fpu/s_fmaxf.S (__fmaxf): Likewise. * sysdeps/x86_64/fpu/s_fmaxl.S (__fmaxl): Likewise. * sysdeps/x86_64/fpu/s_fmin.S (__fmin): Likewise. * sysdeps/x86_64/fpu/s_fminf.S (__fminf): Likewise. * sysdeps/x86_64/fpu/s_fminl.S (__fminl): Likewise. * math/libm-test.inc (fmax_test_data): Add tests of sNaN inputs. (fmin_test_data): Likewise. --- sysdeps/x86_64/fpu/s_fmax.S | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) (limited to 'sysdeps/x86_64/fpu/s_fmax.S') diff --git a/sysdeps/x86_64/fpu/s_fmax.S b/sysdeps/x86_64/fpu/s_fmax.S index 02096c0aea..0ff326fb66 100644 --- a/sysdeps/x86_64/fpu/s_fmax.S +++ b/sysdeps/x86_64/fpu/s_fmax.S @@ -27,8 +27,25 @@ ENTRY(__fmax) jmp 2f 1: ucomisd %xmm1, %xmm1 // Is xmm1 a NaN? - jp 2f // then return xmm0 + jp 3f + // xmm0 is a NaN; xmm1 is not. Test if xmm0 is signaling. + movsd %xmm0, -8(%rsp) + testb $0x8, -2(%rsp) + jz 4f movsd %xmm1, %xmm0 // otherwise return xmm1 + ret + +3: // xmm1 is a NaN; xmm0 may or may not be. + ucomisd %xmm0, %xmm0 + jp 4f + // xmm1 is a NaN; xmm0 is not. Test if xmm1 is signaling. + movsd %xmm1, -8(%rsp) + testb $0x8, -2(%rsp) + jz 4f + ret + +4: // Both arguments are NaNs, or one is a signaling NaN. + addsd %xmm1, %xmm0 2: ret END(__fmax) -- cgit v1.2.3