1;; Copyright (C) 2001-2013 Free Software Foundation, Inc. 2;; 3;; This file is part of GCC. 4;; 5;; GCC is free software; you can redistribute it and/or modify it under 6;; the terms of the GNU General Public License as published by the Free 7;; Software Foundation; either version 3, or (at your option) any later 8;; version. 9;; 10;; GCC is distributed in the hope that it will be useful, but WITHOUT ANY 11;; WARRANTY; without even the implied warranty of MERCHANTABILITY or 12;; FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 13;; for more details. 14;; 15;; Under Section 7 of GPL version 3, you are granted additional 16;; permissions described in the GCC Runtime Library Exception, version 17;; 3.1, as published by the Free Software Foundation. 18;; 19;; You should have received a copy of the GNU General Public License and 20;; a copy of the GCC Runtime Library Exception along with this program; 21;; see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 22;; <http://www.gnu.org/licenses/>. 23;; 24;; This code used to be expanded through interesting expansions in 25;; the machine description, compiled from this code: 26;; 27;; #ifdef L_mulsi3 28;; long __Mul (unsigned long a, unsigned long b) __attribute__ ((__const__)); 29;; 30;; /* This must be compiled with the -mexpand-mul flag, to synthesize the 31;; multiplication from the mstep instructions. The check for 32;; smaller-size multiplication pays off in the order of .5-10%; 33;; estimated median 1%, depending on application. 34;; FIXME: It can be further optimized if we go to assembler code, as 35;; gcc 2.7.2 adds a few unnecessary instructions and does not put the 36;; basic blocks in optimal order. */ 37;; long 38;; __Mul (unsigned long a, unsigned long b) 39;; { 40;; #if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10 41;; /* In case other code is compiled without -march=v10, they will 42;; contain calls to __Mul, regardless of flags at link-time. The 43;; "else"-code below will work, but is unnecessarily slow. This 44;; sometimes cuts a few minutes off from simulation time by just 45;; returning a "mulu.d". */ 46;; return a * b; 47;; #else 48;; unsigned long min; 49;; 50;; /* Get minimum via the bound insn. */ 51;; min = a < b ? a : b; 52;; 53;; /* Can we omit computation of the high part? */ 54;; if (min > 65535) 55;; /* No. Perform full multiplication. */ 56;; return a * b; 57;; else 58;; { 59;; /* Check if both operands are within 16 bits. */ 60;; unsigned long max; 61;; 62;; /* Get maximum, by knowing the minimum. 63;; This will partition a and b into max and min. 64;; This is not currently something GCC understands, 65;; so do this trick by asm. */ 66;; __asm__ ("xor %1,%0\n\txor %2,%0" 67;; : "=r" (max) 68;; : "r" (b), "r" (a), "0" (min)); 69;; 70;; if (max > 65535) 71;; /* Make GCC understand that only the low part of "min" will be 72;; used. */ 73;; return max * (unsigned short) min; 74;; else 75;; /* Only the low parts of both operands are necessary. */ 76;; return ((unsigned short) max) * (unsigned short) min; 77;; } 78;; #endif /* not __CRIS_arch_version >= 10 */ 79;; } 80;; #endif /* L_mulsi3 */ 81;; 82;; That approach was abandoned since the caveats outweighted the 83;; benefits. The expand-multiplication machinery is also removed, so you 84;; can't do this anymore. 85;; 86;; For doubters of there being any benefits, some where: insensitivity to: 87;; - ABI changes (mostly for experimentation) 88;; - assembler syntax differences (mostly debug format). 89;; - insn scheduling issues. 90;; Most ABI experiments will presumably happen with arches with mul insns, 91;; so that argument doesn't really hold anymore, and it's unlikely there 92;; being new arch variants needing insn scheduling and not having mul 93;; insns. 94 95;; ELF and a.out have different syntax for local labels: the "wrong" 96;; one may not be omitted from the object. 97#undef L 98#ifdef __AOUT__ 99# define L(x) x 100#else 101# define L(x) .x 102#endif 103 104 .global ___Mul 105 .type ___Mul,@function 106___Mul: 107#if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10 108;; Can't have the mulu.d last on a cache-line (in the delay-slot of the 109;; "ret"), due to hardware bug. See documentation for -mmul-bug-workaround. 110;; Not worthwhile to conditionalize here. 111 .p2alignw 2,0x050f 112 mulu.d $r11,$r10 113 ret 114 nop 115#else 116 move.d $r10,$r12 117 move.d $r11,$r9 118 bound.d $r12,$r9 119 cmpu.w 65535,$r9 120 bls L(L3) 121 move.d $r12,$r13 122 123 movu.w $r11,$r9 124 lslq 16,$r13 125 mstep $r9,$r13 126 mstep $r9,$r13 127 mstep $r9,$r13 128 mstep $r9,$r13 129 mstep $r9,$r13 130 mstep $r9,$r13 131 mstep $r9,$r13 132 mstep $r9,$r13 133 mstep $r9,$r13 134 mstep $r9,$r13 135 mstep $r9,$r13 136 mstep $r9,$r13 137 mstep $r9,$r13 138 mstep $r9,$r13 139 mstep $r9,$r13 140 mstep $r9,$r13 141 clear.w $r10 142 test.d $r10 143 mstep $r9,$r10 144 mstep $r9,$r10 145 mstep $r9,$r10 146 mstep $r9,$r10 147 mstep $r9,$r10 148 mstep $r9,$r10 149 mstep $r9,$r10 150 mstep $r9,$r10 151 mstep $r9,$r10 152 mstep $r9,$r10 153 mstep $r9,$r10 154 mstep $r9,$r10 155 mstep $r9,$r10 156 mstep $r9,$r10 157 mstep $r9,$r10 158 mstep $r9,$r10 159 movu.w $r12,$r12 160 move.d $r11,$r9 161 clear.w $r9 162 test.d $r9 163 mstep $r12,$r9 164 mstep $r12,$r9 165 mstep $r12,$r9 166 mstep $r12,$r9 167 mstep $r12,$r9 168 mstep $r12,$r9 169 mstep $r12,$r9 170 mstep $r12,$r9 171 mstep $r12,$r9 172 mstep $r12,$r9 173 mstep $r12,$r9 174 mstep $r12,$r9 175 mstep $r12,$r9 176 mstep $r12,$r9 177 mstep $r12,$r9 178 mstep $r12,$r9 179 add.w $r9,$r10 180 lslq 16,$r10 181 ret 182 add.d $r13,$r10 183 184L(L3): 185 move.d $r9,$r10 186 xor $r11,$r10 187 xor $r12,$r10 188 cmpu.w 65535,$r10 189 bls L(L5) 190 movu.w $r9,$r13 191 192 movu.w $r13,$r13 193 move.d $r10,$r9 194 lslq 16,$r9 195 mstep $r13,$r9 196 mstep $r13,$r9 197 mstep $r13,$r9 198 mstep $r13,$r9 199 mstep $r13,$r9 200 mstep $r13,$r9 201 mstep $r13,$r9 202 mstep $r13,$r9 203 mstep $r13,$r9 204 mstep $r13,$r9 205 mstep $r13,$r9 206 mstep $r13,$r9 207 mstep $r13,$r9 208 mstep $r13,$r9 209 mstep $r13,$r9 210 mstep $r13,$r9 211 clear.w $r10 212 test.d $r10 213 mstep $r13,$r10 214 mstep $r13,$r10 215 mstep $r13,$r10 216 mstep $r13,$r10 217 mstep $r13,$r10 218 mstep $r13,$r10 219 mstep $r13,$r10 220 mstep $r13,$r10 221 mstep $r13,$r10 222 mstep $r13,$r10 223 mstep $r13,$r10 224 mstep $r13,$r10 225 mstep $r13,$r10 226 mstep $r13,$r10 227 mstep $r13,$r10 228 mstep $r13,$r10 229 lslq 16,$r10 230 ret 231 add.d $r9,$r10 232 233L(L5): 234 movu.w $r9,$r9 235 lslq 16,$r10 236 mstep $r9,$r10 237 mstep $r9,$r10 238 mstep $r9,$r10 239 mstep $r9,$r10 240 mstep $r9,$r10 241 mstep $r9,$r10 242 mstep $r9,$r10 243 mstep $r9,$r10 244 mstep $r9,$r10 245 mstep $r9,$r10 246 mstep $r9,$r10 247 mstep $r9,$r10 248 mstep $r9,$r10 249 mstep $r9,$r10 250 mstep $r9,$r10 251 ret 252 mstep $r9,$r10 253#endif 254L(Lfe1): 255 .size ___Mul,L(Lfe1)-___Mul 256