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