/* $OpenBSD: impyu.S,v 1.7 2002/05/07 22:19:30 mickey Exp $ */ /* (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. */ /* @(#)impyu.s: Revision: 1.11.88.1 Date: 93/12/07 15:06:31 */ #include ;**************************************************************************** ; ;Implement an integer multiply routine for 32-bit operands and 64-bit product ; with operand values of zero (multiplicand only) and 2**32reated specially. ; The algorithm uses 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 saveop2 .equ 8 ; save op2 if high bit of multiplicand ; is set pc .equ 9 ; carry bit of product, = 00...01 pm .equ 10 ; value of -1 used in shifting temp .equ 6 ;**************************************************************************** .text LEAF_ENTRY(impyu) 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 saveop2,4(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(arg0),op1 ; get multiplicand ldws 0(arg1),op2 ; get multiplier addib,= 0,op1,fini0 ; op1 = 0, product = 0 addi 0,gr0,pu ; clear product bb,>= op1,0,mpy1 ; test msb of multiplicand addi 0,gr0,saveop2 ; clear saveop2 ; ; msb of multiplicand is set so will save multiplier for a final ; addition into the result ; extru,= op1,31,31,op1 ; clear msb of multiplicand b mpy1 ; if op1 < 2**32, start multiply add op2,gr0,saveop2 ; save op2 in saveop2 shd gr0,op2,1,pu ; shift op2 left 31 for result b fini ; go to finish shd op2,gr0,1,pl ; mpy1 addi -1,gr0,pm ; initialize pm to 111...1 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,nuv 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,> -1,cnt,mloop ; decrement count, loop if > 0 shd pm,pu,4,pu ; shift 4, minus signed addb,tr op1,pu,lastadd ; do one more add, then finish addb,=,n saveop2,gr0,fini ; check saveop2 ; sh4c addib,> -1,cnt,mloop ; decrement count, loop if > 0 shd pc,pu,4,pu ; shift 4 with overflow b lastadd ; end of multiply addb,=,n saveop2,gr0,fini ; check saveop2 ; 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 lastadd ; end of multiply addb,=,n saveop2,gr0,fini ; check saveop2 ; 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,> -1,cnt,mloop ; decrement count, loop if > 0 shd pm,pu,2,pu ; shift with minus sign addb,tr op1,pu,lastadd ; do one more add, then finish addb,=,n saveop2,gr0,fini ; check saveop2 ; 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,> -1,cnt,mloop ; decrement count, loop if > 0 shd pm,pu,2,pu ; shift with minus sign addb,tr op1,pu,lastadd ; do one more add, then finish addb,=,n saveop2,gr0,fini ; check saveop2 ; 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,> -1,cnt,mloop ; decrement count, loop if >0 shd pm,pu,3,pu addb,tr op1,pu,lastadd ; do one more add, then finish addb,=,n saveop2,gr0,fini ; check saveop2 ; fini0 movib,tr 0,pl,fini ; product = 0 as op1 = 0 stws pu,0(arg2) ; save high part of result ; 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 addb,=,n saveop2,gr0,fini ; check saveop2 lastadd shd saveop2,gr0,1,temp ; if saveop2 <> 0, shift it shd gr0,saveop2,1,saveop2 ; left 31 and add to result add pl,temp,pl addc pu,saveop2,pu ; ; 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),saveop2 ; 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(impu) .end