Message ID | Pine.LNX.4.64.1406041735120.3719@digraph.polyomino.org.uk |
---|---|
State | New |
Headers | show |
Ping. This patch <https://sourceware.org/ml/libc-alpha/2014-06/msg00076.html> is pending review.
Ping^2. This patch <https://sourceware.org/ml/libc-alpha/2014-06/msg00076.html> is still pending review.
On Wed, Jun 04, 2014 at 05:35:42PM +0000, Joseph S. Myers wrote: > This patch fixes __ieee754_logl (-LDBL_MAX) on x86_64 and x86 not to > subtract 1 from its argument and so cause spurious overflow in > FE_DOWNWARD mode. (For any argument strictly less than -1, it doesn't > matter whether or not 1 is subtracted before computing log1p, as long > as the result doesn't overflow to -Inf.) > > Tested x86_64 and x86. (This particular case lacks test coverage, > since the testsuite doesn't cover -lieee, but it will be covered by > tests after the following patch to test pow in all rounding modes, > which was the context in which this bug was found.) > > 2014-06-04 Joseph Myers <joseph@codesourcery.com> > > [BZ #17022] > * sysdeps/i386/fpu/e_logl.S (__ieee754_logl): Do not subtract 1 > from arguments -2 or below. > * sysdeps/i386/i686/fpu/e_logl.S (__ieee754_logl): Likewise. > * sysdeps/x86_64/fpu/e_logl.S (__ieee754_logl): Likewise. Looks good to me. Siddhesh > > diff --git a/sysdeps/i386/fpu/e_logl.S b/sysdeps/i386/fpu/e_logl.S > index edae1d7..828e98a 100644 > --- a/sysdeps/i386/fpu/e_logl.S > +++ b/sysdeps/i386/fpu/e_logl.S > @@ -40,8 +40,11 @@ ENTRY(__ieee754_logl) > fld %st // x : x : log(2) > sahf > jc 3f // in case x is NaN or +-Inf > + movzwl 4+8(%esp), %eax > + cmpl $0xc000, %eax > + jae 6f // x <= -2, avoid overflow from -LDBL_MAX - 1. > 4: fsubl MO(one) // x-1 : x : log(2) > - fld %st // x-1 : x-1 : x : log(2) > +6: fld %st // x-1 : x-1 : x : log(2) > fabs // |x-1| : x-1 : x : log(2) > fcompl MO(limit) // x-1 : x : log(2) > fnstsw // x-1 : x : log(2) > diff --git a/sysdeps/i386/i686/fpu/e_logl.S b/sysdeps/i386/i686/fpu/e_logl.S > index a0d1107..0ccc8fc 100644 > --- a/sysdeps/i386/i686/fpu/e_logl.S > +++ b/sysdeps/i386/i686/fpu/e_logl.S > @@ -39,8 +39,11 @@ ENTRY(__ieee754_logl) > LOAD_PIC_REG (dx) > #endif > fld %st // x : x : log(2) > + movzwl 4+8(%esp), %eax > + cmpl $0xc000, %eax > + jae 5f // x <= -2, avoid overflow from -LDBL_MAX - 1. > fsubl MO(one) // x-1 : x : log(2) > - fld %st // x-1 : x-1 : x : log(2) > +5: fld %st // x-1 : x-1 : x : log(2) > fabs // |x-1| : x-1 : x : log(2) > fld MO(limit) // 0.29 : |x-1| : x-1 : x : log(2) > fcomip %st(1) // |x-1| : x-1 : x : log(2) > diff --git a/sysdeps/x86_64/fpu/e_logl.S b/sysdeps/x86_64/fpu/e_logl.S > index 315afc0..047b8db 100644 > --- a/sysdeps/x86_64/fpu/e_logl.S > +++ b/sysdeps/x86_64/fpu/e_logl.S > @@ -38,8 +38,11 @@ ENTRY(__ieee754_logl) > fld %st // x : x : log(2) > testb $1, %ah > jnz 3f // in case x is NaN or +-Inf > + movzwl 8+8(%rsp), %eax > + cmpl $0xc000, %eax > + jae 6f // x <= -2, avoid overflow from -LDBL_MAX - 1. > 4: fsubl MO(one) // x-1 : x : log(2) > - fld %st // x-1 : x-1 : x : log(2) > +6: fld %st // x-1 : x-1 : x : log(2) > fabs // |x-1| : x-1 : x : log(2) > fcompl MO(limit) // x-1 : x : log(2) > fnstsw // x-1 : x : log(2) > > -- > Joseph S. Myers > joseph@codesourcery.com
diff --git a/sysdeps/i386/fpu/e_logl.S b/sysdeps/i386/fpu/e_logl.S index edae1d7..828e98a 100644 --- a/sysdeps/i386/fpu/e_logl.S +++ b/sysdeps/i386/fpu/e_logl.S @@ -40,8 +40,11 @@ ENTRY(__ieee754_logl) fld %st // x : x : log(2) sahf jc 3f // in case x is NaN or +-Inf + movzwl 4+8(%esp), %eax + cmpl $0xc000, %eax + jae 6f // x <= -2, avoid overflow from -LDBL_MAX - 1. 4: fsubl MO(one) // x-1 : x : log(2) - fld %st // x-1 : x-1 : x : log(2) +6: fld %st // x-1 : x-1 : x : log(2) fabs // |x-1| : x-1 : x : log(2) fcompl MO(limit) // x-1 : x : log(2) fnstsw // x-1 : x : log(2) diff --git a/sysdeps/i386/i686/fpu/e_logl.S b/sysdeps/i386/i686/fpu/e_logl.S index a0d1107..0ccc8fc 100644 --- a/sysdeps/i386/i686/fpu/e_logl.S +++ b/sysdeps/i386/i686/fpu/e_logl.S @@ -39,8 +39,11 @@ ENTRY(__ieee754_logl) LOAD_PIC_REG (dx) #endif fld %st // x : x : log(2) + movzwl 4+8(%esp), %eax + cmpl $0xc000, %eax + jae 5f // x <= -2, avoid overflow from -LDBL_MAX - 1. fsubl MO(one) // x-1 : x : log(2) - fld %st // x-1 : x-1 : x : log(2) +5: fld %st // x-1 : x-1 : x : log(2) fabs // |x-1| : x-1 : x : log(2) fld MO(limit) // 0.29 : |x-1| : x-1 : x : log(2) fcomip %st(1) // |x-1| : x-1 : x : log(2) diff --git a/sysdeps/x86_64/fpu/e_logl.S b/sysdeps/x86_64/fpu/e_logl.S index 315afc0..047b8db 100644 --- a/sysdeps/x86_64/fpu/e_logl.S +++ b/sysdeps/x86_64/fpu/e_logl.S @@ -38,8 +38,11 @@ ENTRY(__ieee754_logl) fld %st // x : x : log(2) testb $1, %ah jnz 3f // in case x is NaN or +-Inf + movzwl 8+8(%rsp), %eax + cmpl $0xc000, %eax + jae 6f // x <= -2, avoid overflow from -LDBL_MAX - 1. 4: fsubl MO(one) // x-1 : x : log(2) - fld %st // x-1 : x-1 : x : log(2) +6: fld %st // x-1 : x-1 : x : log(2) fabs // |x-1| : x-1 : x : log(2) fcompl MO(limit) // x-1 : x : log(2) fnstsw // x-1 : x : log(2)