/* $OpenBSD: bzero.S,v 1.4 2022/12/06 18:51:00 guenther Exp $ */ /* * Mach Operating System * Copyright (c) 1993-1992 Carnegie Mellon University * Copyright (c) 1991 OMRON Corporation * Copyright (c) 1996 Nivas Madhur * Copyright (c) 1998 Steve Murphree, Jr. * All Rights Reserved. * * Permission to use, copy, modify and distribute this software and its * documentation is hereby granted, provided that both the copyright * notice and this permission notice appear in all copies of the * software, derivative works or modified versions, and any portions * thereof, and that both notices appear in supporting documentation. * * CARNEGIE MELLON AND OMRON ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS IS" * CONDITION. CARNEGIE MELLON AND OMRON DISCLAIM ANY LIABILITY OF ANY KIND * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. * * Carnegie Mellon requests users of this software to return to * * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU * School of Computer Science * Carnegie Mellon University * Pittsburgh PA 15213-3890 * * any improvements or extensions that they make and grant Carnegie the * rights to redistribute these changes. */ #include <machine/asm.h> /*######################################################################*/ /* * April 1990, Omron Corporation * jfriedl@nff.ncl.omron.co.jp * * void bzero(destination, length) * * Clear (set to zero) LENGTH bytes of memory starting at DESTINATION. * Note that there is no return value. * * This is fast. Really fast. Especially for long lengths. */ #define R_dest %r2 #define R_len %r3 #define R_bytes %r4 #define R_mark_address %r5 #define R_addr %r6 /* R_addr && R_temp SHARE */ #define R_temp %r6 /* R_addr && R_temp SHARE */ ENTRY(bzero) /* * If the destination is not word aligned, we'll word align * it first to make things easier. * * We'll check to see first if bit #0 is set and then bit #1 * (of the destination address). If either are set, it's * not word aligned. */ bb1 0, R_dest, not_initially_word_aligned bb1 1, R_dest, not_initially_word_aligned ASLOCAL(now_word_aligned) /* * before we get into the main loop, grab the * address of the label "mark" below. */ or.u R_mark_address, %r0, %hi16(mark) or R_mark_address, R_mark_address, %lo16(mark) ASLOCAL(top_of_main_loop) #define MAX_AT_ONE_TIME 128 /* * Now we find out how many words we can zero-fill in a row. * We do this by doing something like: * * bytes &= 0xfffffffc; * if (bytes > MAX_AT_ONE_TIME) * bytes = MAX_AT_ONE_TIME; */ /* * Clear lower two bits of length to give us the number of bytes * ALIGNED TO THE WORD LENGTH remaining to move. */ clr R_bytes, R_len, 2<0> /* if we're done clearing WORDS, jump out */ bcnd eq0, R_bytes, done_doing_words /* if the number of bytes > MAX_AT_ONE_TIME, do only the max */ cmp R_temp, R_bytes, MAX_AT_ONE_TIME bb1 lt, R_temp, 1f /* * Since we're doing the max, we know exactly where we're * jumping (the first one in the list!), so we can jump * right there. However, we've still got to adjust * the length, so we'll jump to where we adjust the length * which just happens to fall through to the first store zero * in the list. * * Note, however, that we're jumping to an instruction that * would be in the delay slot for the jump in front of it, * so if you change things here, WATCH OUT. */ br.n do_max or R_bytes, %r0, MAX_AT_ONE_TIME 1: /* * Now we have the number of bytes to zero during this iteration, * (which, as it happens, is the last iteration if we're here). * We'll calculate the proper place to jump and then jump there, * after adjusting the length. NOTE that there is a label between * the "jmp.n" and the "subu" below... the "subu" is NOT always * executed in the delay slot of the "jmp.n". */ subu R_addr, R_mark_address, R_bytes /* and go there (after adjusting the length via ".n") */ jmp.n R_addr ASLOCAL(do_max) subu R_len, R_len, R_bytes /* NOTE: this is in the delay slot! */ st %r0, R_dest, 0x7c /* 128 */ st %r0, R_dest, 0x78 /* 124 */ st %r0, R_dest, 0x74 /* 120 */ st %r0, R_dest, 0x70 /* 116 */ st %r0, R_dest, 0x6c /* 112 */ st %r0, R_dest, 0x68 /* 108 */ st %r0, R_dest, 0x64 /* 104 */ st %r0, R_dest, 0x60 /* 100 */ st %r0, R_dest, 0x5c /* 96 */ st %r0, R_dest, 0x58 /* 92 */ st %r0, R_dest, 0x54 /* 88 */ st %r0, R_dest, 0x50 /* 84 */ st %r0, R_dest, 0x4c /* 80 */ st %r0, R_dest, 0x48 /* 76 */ st %r0, R_dest, 0x44 /* 72 */ st %r0, R_dest, 0x40 /* 68 */ st %r0, R_dest, 0x3c /* 64 */ st %r0, R_dest, 0x38 /* 60 */ st %r0, R_dest, 0x34 /* 56 */ st %r0, R_dest, 0x30 /* 52 */ st %r0, R_dest, 0x2c /* 44 */ st %r0, R_dest, 0x28 /* 40 */ st %r0, R_dest, 0x24 /* 36 */ st %r0, R_dest, 0x20 /* 32 */ st %r0, R_dest, 0x1c /* 28 */ st %r0, R_dest, 0x18 /* 24 */ st %r0, R_dest, 0x14 /* 20 */ st %r0, R_dest, 0x10 /* 16 */ st %r0, R_dest, 0x0c /* 12 */ st %r0, R_dest, 0x08 /* 8 */ st %r0, R_dest, 0x04 /* 4 */ st %r0, R_dest, 0x00 /* 0 */ ASLOCAL(mark) br.n top_of_main_loop addu R_dest, R_dest, R_bytes /* bump up the dest address */ ASLOCAL(done_doing_words) bcnd ne0, R_len, 1f jmp %r1 1: subu R_len, R_len, 1 bcnd.n ne0, R_len, 1b st.b %r0, R_dest, R_len 1: jmp %r1 ASLOCAL(not_initially_word_aligned) /* * Bzero to word-align the address (at least if the length allows it). */ bcnd eq0, R_len, 1b st.b %r0, R_dest, 0 addu R_dest, R_dest, 1 mask R_temp, R_dest, 0x3 bcnd.n eq0, R_temp, now_word_aligned subu R_len, R_len, 1 br not_initially_word_aligned #undef R_dest #undef R_len #undef R_bytes #undef R_mark_address #undef R_addr #undef R_temp #undef MAX_AT_ONE_TIME
