/* $OpenBSD: impys.S,v 1.5 2001/03/29 03:58:18 mickey Exp $ */ /* * Copyright 1996 1995 by Open Software Foundation, Inc. * All Rights Reserved * * Permission to use, copy, modify, and distribute this software and * its documentation for any purpose and without fee is hereby granted, * provided that the above copyright notice appears in all copies and * that both the copyright notice and this permission notice appear in * supporting documentation. * * OSF DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE. * * IN NO EVENT SHALL OSF BE LIABLE FOR ANY SPECIAL, INDIRECT, OR * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM * LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT, * NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. * */ /* * pmk1.1 */ /* * (c) Copyright 1986 HEWLETT-PACKARD COMPANY * * To anyone who acknowledges that this file is provided "AS IS" * without any express or implied warranty: * permission to use, copy, modify, and distribute this file * for any purpose is hereby granted without fee, provided that * the above copyright notice and this notice appears in all * copies, and that the name of Hewlett-Packard Company not be * used in advertising or publicity pertaining to distribution * of the software without specific, written prior permission. * Hewlett-Packard Company makes no representations about the * suitability of this software for any purpose. */ #include /**************************************************************************** * * Implement an integer multiply routine for 32-bit operands and 64-bit product * with operand values of zero (multiplicand only) and -2**31 treated specially. * The algorithm uses the absolute value of the multiplier, four bits at a time, * from right to left, to generate partial product. Execution speed is more * important than program size in this implementation. * ***************************************************************************/ /* * Definitions - General registers */ gr0 .equ 0 /* General register zero */ pu .equ 3 /* upper part of product */ pl .equ 4 /* lower part of product */ op2 .equ 4 /* multiplier */ op1 .equ 5 /* multiplicand */ cnt .equ 6 /* count in multiply */ brindex .equ 7 /* index into the br. table */ sign .equ 8 /* sign of product */ pc .equ 9 /* carry bit of product, = 00...01 */ pm .equ 10 /* value of -1 used in shifting */ .text ENTRY(impys) stws,ma pu,4(sp) ; save registers on stack stws,ma pl,4(sp) ; save registers on stack stws,ma op1,4(sp) ; save registers on stack stws,ma cnt,4(sp) ; save registers on stack stws,ma brindex,4(sp) ; save registers on stack stws,ma sign,4(sp) ; save registers on stack stws,ma pc,4(sp) ; save registers on stack stws,ma pm,4(sp) ; save registers on stack ; ; Start multiply process ; ldws 0(arg1),op2 ; get multiplier ldws 0(arg0),op1 ; get multiplicand addi -1,gr0,pm ; initialize pm to 111...1 comb,< op2,gr0,mpyb ; br. if multiplier < 0 xor op2,op1,sign ; sign(0) = sign of product mpy1 comb,< op1,gr0,mpya ; br. if multiplicand < 0 addi 0,gr0,pu ; clear product addib,= 0,op1,fini0 ; op1 = 0, product = 0 mpy2 addi 1,gr0,pc ; initialize pc to 00...01 movib,tr 8,cnt,mloop ; set count for mpy loop extru op2,31,4,brindex ; 4 bits as index into table ; .align 8 ; b sh4c ; br. if sign overflow sh4n shd pu,pl,4,pl ; shift product right 4 bits addib,<= -1,cnt,mulend ; reduce count by 1, exit if extru pu,27,28,pu ; <= zero ; mloop blr brindex,gr0 ; br. into table ; entries of 2 words extru op2,27,4,brindex ; next 4 bits into index ; ; ; branch table for the multiplication process with four multiplier bits ; mtable ; two words per entry ; ; ---- bits = 0000 ---- shift product 4 bits ------------------------------- ; b sh4n+4 ; just shift partial shd pu,pl,4,pl ; product right 4 bits ; ; ---- bits = 0001 ---- add op1, then shift 4 bits ; addb,tr op1,pu,sh4n+4 ; add op1 to product, to shift shd pu,pl,4,pl ; product right 4 bits ; ; ---- bits = 0010 ---- add op1, add op1, then shift 4 bits ; addb,tr op1,pu,sh4n ; add 2*op1, to shift addb,uv op1,pu,sh4c ; product right 4 bits ; ; ---- bits = 0011 ---- add op1, add 2*op1, shift 4 bits ; addb,tr op1,pu,sh4n-4 ; add op1 & 2*op1, shift sh1add,nsv op1,pu,pu ; product right 4 bits ; ; ---- bits = 0100 ---- shift 2, add op1, shift 2 ; b sh2sa shd pu,pl,2,pl ; shift product 2 bits ; ; ---- bits = 0101 ---- add op1, shift 2, add op1, and shift 2 again ; addb,tr op1,pu,sh2us ; add op1 to product shd pu,pl,2,pl ; shift 2 bits ; ; ---- bits = 0110 ---- add op1, add op1, shift 2, add op1, and shift 2 again ; addb,tr op1,pu,sh2c ; add 2*op1, to shift 2 bits addb,nuv op1,pu,sh2us ; br. if not overflow ; ; ---- bits = 0111 ---- subtract op1, shift 3, add op1, and shift 1 ; b sh3s sub pu,op1,pu ; subtract op1, br. to sh3s ; ; ---- bits = 1000 ---- shift 3, add op1, shift 1 ; b sh3sa shd pu,pl,3,pl ; shift product right 3 bits ; ; ---- bits = 1001 ---- add op1, shift 3, add op1, shift 1 ; addb,tr op1,pu,sh3us ; add op1, to shift 3, add op1, shd pu,pl,3,pl ; and shift 1 ; ; ---- bits = 1010 ---- add op1, add op1, shift 3, add op1, shift 1 ; addb,tr op1,pu,sh3c ; add 2*op1, to shift 3 bits addb,nuv op1,pu,sh3us ; br. if no overflow ; ; ---- bits = 1011 ---- add -op1, shift 2, add -op1, shift 2, inc. next index ; addib,tr 1,brindex,sh2s ; add 1 to index, subtract op1, sub pu,op1,pu ; shift 2 with minus sign ; ; ---- bits = 1100 ---- shift 2, subtract op1, shift 2, increment next index ; addib,tr 1,brindex,sh2sb ; add 1 to index, to shift shd pu,pl,2,pl ; shift right 2 bits signed ; ; ---- bits = 1101 ---- add op1, shift 2, add -op1, shift 2 ; addb,tr op1,pu,sh2ns ; add op1, to shift 2 shd pu,pl,2,pl ; right 2 unsigned, etc. ; ; ---- bits = 1110 ---- shift 1 signed, add -op1, shift 3 signed ; addib,tr 1,brindex,sh1sa ; add 1 to index, to shift shd pu,pl,1,pl ; shift 1 bit ; ; ---- bits = 1111 ---- add -op1, shift 4 signed ; addib,tr 1,brindex,sh4s ; add 1 to index, subtract op1, sub pu,op1,pu ; to shift 4 signed ; ; ---- bits = 10000 ---- shift 4 signed ; addib,tr 1,brindex,sh4s+4 ; add 1 to index shd pu,pl,4,pl ; shift 4 signed ; ; ---- end of table --------------------------------------------------------- ; sh4s shd pu,pl,4,pl addib,tr -1,cnt,mloop ; loop (count > 0 always here) shd pm,pu,4,pu ; shift 4, minus signed ; sh4c addib,> -1,cnt,mloop ; decrement count, loop if > 0 shd pc,pu,4,pu ; shift 4 with overflow b signs ; end of multiply bb,>=,n sign,0,fini ; test sign of procduct ; mpyb add,= op2,op2,gr0 ; if <> 0, back to main sect. b mpy1 sub 0,op2,op2 ; op2 = |multiplier| add,>= op1,gr0,gr0 ; if op1 < 0, invert sign, xor pm,sign,sign ; for correct result ; ; special case for multiplier = -2**31, op1 = signed multiplicand ; or multiplicand = -2**31, op1 = signed multiplier ; shd op1,0,1,pl ; shift op1 left 31 bits mmax extrs op1,30,31,pu b signs ; negate product (if needed) bb,>=,n sign,0,fini ; test sign of product ; mpya add,= op1,op1,gr0 ; op1 = -2**31, special case b mpy2 sub 0,op1,op1 ; op1 = |multiplicand| add,>= op2,gr0,gr0 ; if op2 < 0, invert sign, xor pm,sign,sign ; for correct result movb,tr op2,op1,mmax ; use op2 as multiplicand shd op1,0,1,pl ; shift it left 31 bits ; sh3c shd pu,pl,3,pl ; shift product 3 bits shd pc,pu,3,pu ; shift 3 signed addb,tr op1,pu,sh1 ; add op1, to shift 1 bit shd pu,pl,1,pl ; sh3us extru pu,28,29,pu ; shift 3 unsigned addb,tr op1,pu,sh1 ; add op1, to shift 1 bit shd pu,pl,1,pl ; sh3sa extrs pu,28,29,pu ; shift 3 signed addb,tr op1,pu,sh1 ; add op1, to shift 1 bit shd pu,pl,1,pl ; sh3s shd pu,pl,3,pl ; shift 3 minus signed shd pm,pu,3,pu addb,tr op1,pu,sh1 ; add op1, to shift 1 bit shd pu,pl,1,pl ; sh1 addib,> -1,cnt,mloop ; loop if count > 0 extru pu,30,31,pu b signs ; end of multiply bb,>=,n sign,0,fini ; test sign of product ; sh2ns addib,tr 1,brindex,sh2sb+4 ; increment index extru pu,29,30,pu ; shift unsigned ; sh2s shd pu,pl,2,pl ; shift with minus sign shd pm,pu,2,pu ; sub pu,op1,pu ; subtract op1 shd pu,pl,2,pl ; shift with minus sign addib,tr -1,cnt,mloop ; decrement count, loop shd pm,pu,2,pu ; shift with minus sign ; count never reaches 0 here ; sh2sb extrs pu,29,30,pu ; shift 2 signed sub pu,op1,pu ; subtract op1 from product shd pu,pl,2,pl ; shift with minus sign addib,tr -1,cnt,mloop ; decrement count, loop shd pm,pu,2,pu ; shift with minus sign ; count never reaches 0 here ; sh1sa extrs pu,30,31,pu ; signed sub pu,op1,pu ; subtract op1 from product shd pu,pl,3,pl ; shift 3 with minus sign addib,tr -1,cnt,mloop ; dec. count, to loop shd pm,pu,3,pu ; count never reaches 0 here ; fini0 movib,tr,n 0,pl,fini ; product = 0 as op1 = 0 ; sh2us extru pu,29,30,pu ; shift 2 unsigned addb,tr op1,pu,sh2a ; add op1 shd pu,pl,2,pl ; shift 2 bits ; sh2c shd pu,pl,2,pl shd pc,pu,2,pu ; shift with carry addb,tr op1,pu,sh2a ; add op1 to product shd pu,pl,2,pl ; br. to sh2 to shift pu ; sh2sa extrs pu,29,30,pu ; shift with sign addb,tr op1,pu,sh2a ; add op1 to product shd pu,pl,2,pl ; br. to sh2 to shift pu ; sh2a addib,> -1,cnt,mloop ; loop if count > 0 extru pu,29,30,pu ; mulend bb,>=,n sign,0,fini ; test sign of product signs sub 0,pl,pl ; negate product if sign subb 0,pu,pu ; is negative ; ; finish ; fini stws pu,0(arg2) ; save high part of result stws pl,4(arg2) ; save low part of result ldws,mb -4(sp),pm ; restore registers ldws,mb -4(sp),pc ; restore registers ldws,mb -4(sp),sign ; restore registers ldws,mb -4(sp),brindex ; restore registers ldws,mb -4(sp),cnt ; restore registers ldws,mb -4(sp),op1 ; restore registers ldws,mb -4(sp),pl ; restore registers bv 0(rp) ; return ldws,mb -4(sp),pu ; restore registers EXIT(impys) .end