;; Copyright (C) 2001-2021 Free Software Foundation, Inc. | |

;; | |

;; This file is part of GCC. | |

;; | |

;; GCC is free software; you can redistribute it and/or modify it under | |

;; the terms of the GNU General Public License as published by the Free | |

;; Software Foundation; either version 3, or (at your option) any later | |

;; version. | |

;; | |

;; GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |

;; WARRANTY; without even the implied warranty of MERCHANTABILITY or | |

;; FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |

;; for more details. | |

;; | |

;; Under Section 7 of GPL version 3, you are granted additional | |

;; permissions described in the GCC Runtime Library Exception, version | |

;; 3.1, as published by the Free Software Foundation. | |

;; | |

;; You should have received a copy of the GNU General Public License and | |

;; a copy of the GCC Runtime Library Exception along with this program; | |

;; see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |

;; <http://www.gnu.org/licenses/>. | |

;; | |

;; This code used to be expanded through interesting expansions in | |

;; the machine description, compiled from this code: | |

;; | |

;; #ifdef L_mulsi3 | |

;; long __Mul (unsigned long a, unsigned long b) __attribute__ ((__const__)); | |

;; | |

;; /* This must be compiled with the -mexpand-mul flag, to synthesize the | |

;; multiplication from the mstep instructions. The check for | |

;; smaller-size multiplication pays off in the order of .5-10%; | |

;; estimated median 1%, depending on application. | |

;; FIXME: It can be further optimized if we go to assembler code, as | |

;; gcc 2.7.2 adds a few unnecessary instructions and does not put the | |

;; basic blocks in optimal order. */ | |

;; long | |

;; __Mul (unsigned long a, unsigned long b) | |

;; { | |

;; #if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10 | |

;; /* In case other code is compiled without -march=v10, they will | |

;; contain calls to __Mul, regardless of flags at link-time. The | |

;; "else"-code below will work, but is unnecessarily slow. This | |

;; sometimes cuts a few minutes off from simulation time by just | |

;; returning a "mulu.d". */ | |

;; return a * b; | |

;; #else | |

;; unsigned long min; | |

;; | |

;; /* Get minimum via the bound insn. */ | |

;; min = a < b ? a : b; | |

;; | |

;; /* Can we omit computation of the high part? */ | |

;; if (min > 65535) | |

;; /* No. Perform full multiplication. */ | |

;; return a * b; | |

;; else | |

;; { | |

;; /* Check if both operands are within 16 bits. */ | |

;; unsigned long max; | |

;; | |

;; /* Get maximum, by knowing the minimum. | |

;; This will partition a and b into max and min. | |

;; This is not currently something GCC understands, | |

;; so do this trick by asm. */ | |

;; __asm__ ("xor %1,%0\n\txor %2,%0" | |

;; : "=r" (max) | |

;; : "r" (b), "r" (a), "0" (min)); | |

;; | |

;; if (max > 65535) | |

;; /* Make GCC understand that only the low part of "min" will be | |

;; used. */ | |

;; return max * (unsigned short) min; | |

;; else | |

;; /* Only the low parts of both operands are necessary. */ | |

;; return ((unsigned short) max) * (unsigned short) min; | |

;; } | |

;; #endif /* not __CRIS_arch_version >= 10 */ | |

;; } | |

;; #endif /* L_mulsi3 */ | |

;; | |

;; That approach was abandoned since the caveats outweighted the | |

;; benefits. The expand-multiplication machinery is also removed, so you | |

;; can't do this anymore. | |

;; | |

;; For doubters of there being any benefits, some where: insensitivity to: | |

;; - ABI changes (mostly for experimentation) | |

;; - assembler syntax differences (mostly debug format). | |

;; - insn scheduling issues. | |

;; Most ABI experiments will presumably happen with arches with mul insns, | |

;; so that argument doesn't really hold anymore, and it's unlikely there | |

;; being new arch variants needing insn scheduling and not having mul | |

;; insns. | |

;; ELF and a.out have different syntax for local labels: the "wrong" | |

;; one may not be omitted from the object. | |

#undef L | |

#ifdef __AOUT__ | |

# define L(x) x | |

#else | |

# define L(x) .x | |

#endif | |

.global ___Mul | |

.type ___Mul,@function | |

___Mul: | |

#if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10 | |

;; Can't have the mulu.d last on a cache-line (in the delay-slot of the | |

;; "ret"), due to hardware bug. See documentation for -mmul-bug-workaround. | |

;; Not worthwhile to conditionalize here. | |

.p2alignw 2,0x050f | |

mulu.d $r11,$r10 | |

ret | |

nop | |

#else | |

;; See if we can avoid multiplying some of the parts, knowing | |

;; they're zero. | |

move.d $r11,$r9 | |

bound.d $r10,$r9 | |

cmpu.w 65535,$r9 | |

bls L(L3) | |

move.d $r10,$r12 | |

;; Nope, have to do all the parts of a 32-bit multiplication. | |

;; See head comment in optabs.c:expand_doubleword_mult. | |

move.d $r10,$r13 | |

movu.w $r11,$r9 ; ab*cd = (a*d + b*c)<<16 + b*d | |

lslq 16,$r13 | |

mstep $r9,$r13 ; d*b | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

mstep $r9,$r13 | |

clear.w $r10 | |

test.d $r10 | |

mstep $r9,$r10 ; d*a | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

mstep $r9,$r10 | |

movu.w $r12,$r12 | |

clear.w $r11 | |

move.d $r11,$r9 ; Doubles as a "test.d" preparing for the mstep. | |

mstep $r12,$r9 ; b*c | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

mstep $r12,$r9 | |

add.w $r9,$r10 | |

lslq 16,$r10 | |

ret | |

add.d $r13,$r10 | |

L(L3): | |

;; Form the maximum in $r10, by knowing the minimum, $r9. | |

;; (We don't know which one of $r10 or $r11 it is.) | |

;; Check if the largest operand is still just 16 bits. | |

xor $r9,$r10 | |

xor $r11,$r10 | |

cmpu.w 65535,$r10 | |

bls L(L5) | |

movu.w $r9,$r13 | |

;; We have ab*cd = (a*c)<<32 + (a*d + b*c)<<16 + b*d, but c==0 | |

;; so we only need (a*d)<<16 + b*d with d = $r13, ab = $r10. | |

;; We drop the upper part of (a*d)<<16 as we're only doing a | |

;; 32-bit-result multiplication. | |

move.d $r10,$r9 | |

lslq 16,$r9 | |

mstep $r13,$r9 ; b*d | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

mstep $r13,$r9 | |

clear.w $r10 | |

test.d $r10 | |

mstep $r13,$r10 ; a*d | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

lslq 16,$r10 | |

ret | |

add.d $r9,$r10 | |

L(L5): | |

;; We have ab*cd = (a*c)<<32 + (a*d + b*c)<<16 + b*d, but a and c==0 | |

;; so b*d (with b=$r13, a=$r10) it is. | |

lslq 16,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

mstep $r13,$r10 | |

ret | |

mstep $r13,$r10 | |

#endif | |

L(Lfe1): | |

.size ___Mul,L(Lfe1)-___Mul |