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Diffstat (limited to 'arch/sparc/lib/M7memset.S')
| -rw-r--r-- | arch/sparc/lib/M7memset.S | 352 |
1 files changed, 352 insertions, 0 deletions
diff --git a/arch/sparc/lib/M7memset.S b/arch/sparc/lib/M7memset.S new file mode 100644 index 0000000000..62ea91b3a6 --- /dev/null +++ b/arch/sparc/lib/M7memset.S @@ -0,0 +1,352 @@ +/* + * M7memset.S: SPARC M7 optimized memset. + * + * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved. + */ + +/* + * M7memset.S: M7 optimized memset. + * + * char *memset(sp, c, n) + * + * Set an array of n chars starting at sp to the character c. + * Return sp. + * + * Fast assembler language version of the following C-program for memset + * which represents the `standard' for the C-library. + * + * void * + * memset(void *sp1, int c, size_t n) + * { + * if (n != 0) { + * char *sp = sp1; + * do { + * *sp++ = (char)c; + * } while (--n != 0); + * } + * return (sp1); + * } + * + * The algorithm is as follows : + * + * For small 6 or fewer bytes stores, bytes will be stored. + * + * For less than 32 bytes stores, align the address on 4 byte boundary. + * Then store as many 4-byte chunks, followed by trailing bytes. + * + * For sizes greater than 32 bytes, align the address on 8 byte boundary. + * if (count >= 64) { + * store 8-bytes chunks to align the address on 64 byte boundary + * if (value to be set is zero && count >= MIN_ZERO) { + * Using BIS stores, set the first long word of each + * 64-byte cache line to zero which will also clear the + * other seven long words of the cache line. + * } + * else if (count >= MIN_LOOP) { + * Using BIS stores, set the first long word of each of + * ST_CHUNK cache lines (64 bytes each) before the main + * loop is entered. + * In the main loop, continue pre-setting the first long + * word of each cache line ST_CHUNK lines in advance while + * setting the other seven long words (56 bytes) of each + * cache line until fewer than ST_CHUNK*64 bytes remain. + * Then set the remaining seven long words of each cache + * line that has already had its first long word set. + * } + * store remaining data in 64-byte chunks until less than + * 64 bytes remain. + * } + * Store as many 8-byte chunks, followed by trailing bytes. + * + * BIS = Block Init Store + * Doing the advance store of the first element of the cache line + * initiates the displacement of a cache line while only using a single + * instruction in the pipeline. That avoids various pipeline delays, + * such as filling the miss buffer. The performance effect is + * similar to prefetching for normal stores. + * The special case for zero fills runs faster and uses fewer instruction + * cycles than the normal memset loop. + * + * We only use BIS for memset of greater than MIN_LOOP bytes because a sequence + * BIS stores must be followed by a membar #StoreStore. The benefit of + * the BIS store must be balanced against the cost of the membar operation. + */ + +/* + * ASI_STBI_P marks the cache line as "least recently used" + * which means if many threads are active, it has a high chance + * of being pushed out of the cache between the first initializing + * store and the final stores. + * Thus, we use ASI_STBIMRU_P which marks the cache line as + * "most recently used" for all but the last store to the cache line. + */ + +#include <asm/asi.h> +#include <asm/page.h> + +#define ASI_STBI_P ASI_BLK_INIT_QUAD_LDD_P +#define ASI_STBIMRU_P ASI_ST_BLKINIT_MRU_P + + +#define ST_CHUNK 24 /* multiple of 4 due to loop unrolling */ +#define MIN_LOOP 16320 +#define MIN_ZERO 512 + + .section ".text" + .align 32 + +/* + * Define clear_page(dest) as memset(dest, 0, PAGE_SIZE) + * (can create a more optimized version later.) + */ + .globl M7clear_page + .globl M7clear_user_page +M7clear_page: /* clear_page(dest) */ +M7clear_user_page: + set PAGE_SIZE, %o1 + /* fall through into bzero code */ + + .size M7clear_page,.-M7clear_page + .size M7clear_user_page,.-M7clear_user_page + +/* + * Define bzero(dest, n) as memset(dest, 0, n) + * (can create a more optimized version later.) + */ + .globl M7bzero +M7bzero: /* bzero(dest, size) */ + mov %o1, %o2 + mov 0, %o1 + /* fall through into memset code */ + + .size M7bzero,.-M7bzero + + .global M7memset + .type M7memset, #function + .register %g3, #scratch +M7memset: + mov %o0, %o5 ! copy sp1 before using it + cmp %o2, 7 ! if small counts, just write bytes + bleu,pn %xcc, .wrchar + and %o1, 0xff, %o1 ! o1 is (char)c + + sll %o1, 8, %o3 + or %o1, %o3, %o1 ! now o1 has 2 bytes of c + sll %o1, 16, %o3 + cmp %o2, 32 + blu,pn %xcc, .wdalign + or %o1, %o3, %o1 ! now o1 has 4 bytes of c + + sllx %o1, 32, %o3 + or %o1, %o3, %o1 ! now o1 has 8 bytes of c + +.dbalign: + andcc %o5, 7, %o3 ! is sp1 aligned on a 8 byte bound? + bz,pt %xcc, .blkalign ! already long word aligned + sub %o3, 8, %o3 ! -(bytes till long word aligned) + + add %o2, %o3, %o2 ! update o2 with new count + ! Set -(%o3) bytes till sp1 long word aligned +1: stb %o1, [%o5] ! there is at least 1 byte to set + inccc %o3 ! byte clearing loop + bl,pt %xcc, 1b + inc %o5 + + ! Now sp1 is long word aligned (sp1 is found in %o5) +.blkalign: + cmp %o2, 64 ! check if there are 64 bytes to set + blu,pn %xcc, .wrshort + mov %o2, %o3 + + andcc %o5, 63, %o3 ! is sp1 block aligned? + bz,pt %xcc, .blkwr ! now block aligned + sub %o3, 64, %o3 ! o3 is -(bytes till block aligned) + add %o2, %o3, %o2 ! o2 is the remainder + + ! Store -(%o3) bytes till dst is block (64 byte) aligned. + ! Use long word stores. + ! Recall that dst is already long word aligned +1: + addcc %o3, 8, %o3 + stx %o1, [%o5] + bl,pt %xcc, 1b + add %o5, 8, %o5 + + ! Now sp1 is block aligned +.blkwr: + andn %o2, 63, %o4 ! calculate size of blocks in bytes + brz,pn %o1, .wrzero ! special case if c == 0 + and %o2, 63, %o3 ! %o3 = bytes left after blk stores. + + set MIN_LOOP, %g1 + cmp %o4, %g1 ! check there are enough bytes to set + blu,pn %xcc, .short_set ! to justify cost of membar + ! must be > pre-cleared lines + nop + + ! initial cache-clearing stores + ! get store pipeline moving + rd %asi, %g3 ! save %asi to be restored later + wr %g0, ASI_STBIMRU_P, %asi + + ! Primary memset loop for large memsets +.wr_loop: + sub %o5, 8, %o5 ! adjust %o5 for ASI store alignment + mov ST_CHUNK, %g1 +.wr_loop_start: + stxa %o1, [%o5+8]%asi + subcc %g1, 4, %g1 + stxa %o1, [%o5+8+64]%asi + add %o5, 256, %o5 + stxa %o1, [%o5+8-128]%asi + bgu %xcc, .wr_loop_start + stxa %o1, [%o5+8-64]%asi + + sub %o5, ST_CHUNK*64, %o5 ! reset %o5 + mov ST_CHUNK, %g1 + +.wr_loop_rest: + stxa %o1, [%o5+8+8]%asi + sub %o4, 64, %o4 + stxa %o1, [%o5+16+8]%asi + subcc %g1, 1, %g1 + stxa %o1, [%o5+24+8]%asi + stxa %o1, [%o5+32+8]%asi + stxa %o1, [%o5+40+8]%asi + add %o5, 64, %o5 + stxa %o1, [%o5-8]%asi + bgu %xcc, .wr_loop_rest + stxa %o1, [%o5]ASI_STBI_P + + ! If more than ST_CHUNK*64 bytes remain to set, continue + ! setting the first long word of each cache line in advance + ! to keep the store pipeline moving. + + cmp %o4, ST_CHUNK*64 + bge,pt %xcc, .wr_loop_start + mov ST_CHUNK, %g1 + + brz,a,pn %o4, .asi_done + add %o5, 8, %o5 ! restore %o5 offset + +.wr_loop_small: + stxa %o1, [%o5+8]%asi + stxa %o1, [%o5+8+8]%asi + stxa %o1, [%o5+16+8]%asi + stxa %o1, [%o5+24+8]%asi + stxa %o1, [%o5+32+8]%asi + subcc %o4, 64, %o4 + stxa %o1, [%o5+40+8]%asi + add %o5, 64, %o5 + stxa %o1, [%o5-8]%asi + bgu,pt %xcc, .wr_loop_small + stxa %o1, [%o5]ASI_STBI_P + + ba .asi_done + add %o5, 8, %o5 ! restore %o5 offset + + ! Special case loop for zero fill memsets + ! For each 64 byte cache line, single STBI to first element + ! clears line +.wrzero: + cmp %o4, MIN_ZERO ! check if enough bytes to set + ! to pay %asi + membar cost + blu %xcc, .short_set + nop + sub %o4, 256, %o4 + +.wrzero_loop: + mov 64, %g3 + stxa %o1, [%o5]ASI_STBI_P + subcc %o4, 256, %o4 + stxa %o1, [%o5+%g3]ASI_STBI_P + add %o5, 256, %o5 + sub %g3, 192, %g3 + stxa %o1, [%o5+%g3]ASI_STBI_P + add %g3, 64, %g3 + bge,pt %xcc, .wrzero_loop + stxa %o1, [%o5+%g3]ASI_STBI_P + add %o4, 256, %o4 + + brz,pn %o4, .bsi_done + nop + +.wrzero_small: + stxa %o1, [%o5]ASI_STBI_P + subcc %o4, 64, %o4 + bgu,pt %xcc, .wrzero_small + add %o5, 64, %o5 + ba,a .bsi_done + +.asi_done: + wr %g3, 0x0, %asi ! restored saved %asi +.bsi_done: + membar #StoreStore ! required by use of Block Store Init + +.short_set: + cmp %o4, 64 ! check if 64 bytes to set + blu %xcc, 5f + nop +4: ! set final blocks of 64 bytes + stx %o1, [%o5] + stx %o1, [%o5+8] + stx %o1, [%o5+16] + stx %o1, [%o5+24] + subcc %o4, 64, %o4 + stx %o1, [%o5+32] + stx %o1, [%o5+40] + add %o5, 64, %o5 + stx %o1, [%o5-16] + bgu,pt %xcc, 4b + stx %o1, [%o5-8] + +5: + ! Set the remaining long words +.wrshort: + subcc %o3, 8, %o3 ! Can we store any long words? + blu,pn %xcc, .wrchars + and %o2, 7, %o2 ! calc bytes left after long words +6: + subcc %o3, 8, %o3 + stx %o1, [%o5] ! store the long words + bgeu,pt %xcc, 6b + add %o5, 8, %o5 + +.wrchars: ! check for extra chars + brnz %o2, .wrfin + nop + retl + nop + +.wdalign: + andcc %o5, 3, %o3 ! is sp1 aligned on a word boundary + bz,pn %xcc, .wrword + andn %o2, 3, %o3 ! create word sized count in %o3 + + dec %o2 ! decrement count + stb %o1, [%o5] ! clear a byte + b .wdalign + inc %o5 ! next byte + +.wrword: + subcc %o3, 4, %o3 + st %o1, [%o5] ! 4-byte writing loop + bnz,pt %xcc, .wrword + add %o5, 4, %o5 + + and %o2, 3, %o2 ! leftover count, if any + +.wrchar: + ! Set the remaining bytes, if any + brz %o2, .exit + nop +.wrfin: + deccc %o2 + stb %o1, [%o5] + bgu,pt %xcc, .wrfin + inc %o5 +.exit: + retl ! %o0 was preserved + nop + + .size M7memset,.-M7memset |