RE: [PATCH] powerpc/math-emu: Use kernel generic math-emu code
From: Liu Yu-B13201 <hidden>
Date: 2008-09-24 04:28:58
quoted hunk ↗ jump to hunk
=20diff --git a/arch/powerpc/include/asm/sfp-machine.h=20b/arch/powerpc/include/asm/sfp-machine.h new file mode 100644 index 0000000..ced34f1--- /dev/null +++ b/arch/powerpc/include/asm/sfp-machine.h@@ -0,0 +1,353 @@ +/* Machine-dependent software floating-point definitions. =20PPC version. + Copyright (C) 1997 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Library General=20 Public License as + published by the Free Software Foundation; either version 2 of the + License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will=20 be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file=20 COPYING.LIB. If + not, write to the Free Software Foundation, Inc., + 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + + Actually, this is a PPC (32bit) version, written based on the + i386, sparc, and sparc64 versions, by me, + Peter Maydell (pmaydell@chiark.greenend.org.uk). + Comments are by and large also mine, although they may be=20 inaccurate. + + In picking out asm fragments I've gone with the lowest common + denominator, which also happens to be the hardware I have :-> + That is, a SPARC without hardware multiply and divide. + */ + +/* basic word size definitions */ +#define _FP_W_TYPE_SIZE 32 +#define _FP_W_TYPE unsigned long +#define _FP_WS_TYPE signed long +#define _FP_I_TYPE long + +#define __ll_B ((UWtype) 1 <<=20 (W_TYPE_SIZE / 2)) +#define __ll_lowpart(t) ((UWtype) (t) & (__ll_B - 1)) +#define __ll_highpart(t) ((UWtype) (t) >> (W_TYPE_SIZE / 2)) + +/* You can optionally code some things like addition in asm. For + * example, i386 defines __FP_FRAC_ADD_2 as asm. If you don't + * then you get a fragment of C code [if you change an #ifdef 0 + * in op-2.h] or a call to add_ssaaaa (see below). + * Good places to look for asm fragments to use are gcc and glibc. + * gcc's longlong.h is useful. + */ + +/* We need to know how to multiply and divide. If the host word size + * is >=3D 2*fracbits you can use FP_MUL_MEAT_n_imm(t,R,X,Y) which + * codes the multiply with whatever gcc does to 'a * b'. + * _FP_MUL_MEAT_n_wide(t,R,X,Y,f) is used when you have an asm + * function that can multiply two 1W values and get a 2W result. + * Otherwise you're stuck with _FP_MUL_MEAT_n_hard(t,R,X,Y) which + * does bitshifting to avoid overflow. + * For division there is FP_DIV_MEAT_n_imm(t,R,X,Y,f) for word size + * >=3D 2*fracbits, where f is either _FP_DIV_HELP_imm or + * _FP_DIV_HELP_ldiv (see op-1.h). + * _FP_DIV_MEAT_udiv() is if you have asm to do 2W/1W =3D> (1W, 1W). + * [GCC and glibc have longlong.h which has the asm macro udiv_qrnnd + * to do this.] + * In general, 'n' is the number of words required to hold the type, + * and 't' is either S, D or Q for single/double/quad. + * -- PMM + */ +/* Example: SPARC64: + * #define _FP_MUL_MEAT_S(R,X,Y) _FP_MUL_MEAT_1_imm(S,R,X,Y) + * #define _FP_MUL_MEAT_D(R,X,Y)=09 _FP_MUL_MEAT_1_wide(D,R,X,Y,umul_ppmm) + * #define _FP_MUL_MEAT_Q(R,X,Y)=09 _FP_MUL_MEAT_2_wide(Q,R,X,Y,umul_ppmm) + * + * #define _FP_DIV_MEAT_S(R,X,Y)=09 _FP_DIV_MEAT_1_imm(S,R,X,Y,_FP_DIV_HELP_imm) + * #define _FP_DIV_MEAT_D(R,X,Y) _FP_DIV_MEAT_1_udiv(D,R,X,Y) + * #define _FP_DIV_MEAT_Q(R,X,Y) _FP_DIV_MEAT_2_udiv_64(Q,R,X,Y) + * + * Example: i386: + * #define _FP_MUL_MEAT_S(R,X,Y) =20 _FP_MUL_MEAT_1_wide(S,R,X,Y,_i386_mul_32_64) + * #define _FP_MUL_MEAT_D(R,X,Y) =20 _FP_MUL_MEAT_2_wide(D,R,X,Y,_i386_mul_32_64) + * + * #define _FP_DIV_MEAT_S(R,X,Y) =20 _FP_DIV_MEAT_1_udiv(S,R,X,Y,_i386_div_64_32) + * #define _FP_DIV_MEAT_D(R,X,Y) _FP_DIV_MEAT_2_udiv_64(D,R,X,Y) + */ + +#define _FP_MUL_MEAT_S(R,X,Y) =20 _FP_MUL_MEAT_1_wide(_FP_WFRACBITS_S,R,X,Y,umul_ppmm) +#define _FP_MUL_MEAT_D(R,X,Y) =20 _FP_MUL_MEAT_2_wide(_FP_WFRACBITS_D,R,X,Y,umul_ppmm) + +#define _FP_DIV_MEAT_S(R,X,Y) _FP_DIV_MEAT_1_udiv(S,R,X,Y)
It seems _FP_DIV_MEAT_S() should be defined to _FP_DIV_MEAT_1_udiv_norm(). I can't remember very clear, but it seems single point float need to be normalized before calling udiv_qrnnd.