diff options
Diffstat (limited to 'arch/tile/lib/memset_32.c')
| -rw-r--r-- | arch/tile/lib/memset_32.c | 275 |
1 files changed, 275 insertions, 0 deletions
diff --git a/arch/tile/lib/memset_32.c b/arch/tile/lib/memset_32.c new file mode 100644 index 00000000000..bfde5d864df --- /dev/null +++ b/arch/tile/lib/memset_32.c @@ -0,0 +1,275 @@ +/* + * Copyright 2010 Tilera Corporation. All Rights Reserved. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation, version 2. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or + * NON INFRINGEMENT. See the GNU General Public License for + * more details. + */ + +#include <arch/chip.h> + +#include <linux/types.h> +#include <linux/string.h> +#include <linux/module.h> + + +void *memset(void *s, int c, size_t n) +{ + uint32_t *out32; + int n32; + uint32_t v16, v32; + uint8_t *out8 = s; +#if !CHIP_HAS_WH64() + int ahead32; +#else + int to_align32; +#endif + + /* Experimentation shows that a trivial tight loop is a win up until + * around a size of 20, where writing a word at a time starts to win. + */ +#define BYTE_CUTOFF 20 + +#if BYTE_CUTOFF < 3 + /* This must be at least at least this big, or some code later + * on doesn't work. + */ +#error "BYTE_CUTOFF is too small" +#endif + + if (n < BYTE_CUTOFF) { + /* Strangely, this turns out to be the tightest way to + * write this loop. + */ + if (n != 0) { + do { + /* Strangely, combining these into one line + * performs worse. + */ + *out8 = c; + out8++; + } while (--n != 0); + } + + return s; + } + +#if !CHIP_HAS_WH64() + /* Use a spare issue slot to start prefetching the first cache + * line early. This instruction is free as the store can be buried + * in otherwise idle issue slots doing ALU ops. + */ + __insn_prefetch(out8); + + /* We prefetch the end so that a short memset that spans two cache + * lines gets some prefetching benefit. Again we believe this is free + * to issue. + */ + __insn_prefetch(&out8[n - 1]); +#endif /* !CHIP_HAS_WH64() */ + + + /* Align 'out8'. We know n >= 3 so this won't write past the end. */ + while (((uintptr_t) out8 & 3) != 0) { + *out8++ = c; + --n; + } + + /* Align 'n'. */ + while (n & 3) + out8[--n] = c; + + out32 = (uint32_t *) out8; + n32 = n >> 2; + + /* Tile input byte out to 32 bits. */ + v16 = __insn_intlb(c, c); + v32 = __insn_intlh(v16, v16); + + /* This must be at least 8 or the following loop doesn't work. */ +#define CACHE_LINE_SIZE_IN_WORDS (CHIP_L2_LINE_SIZE() / 4) + +#if !CHIP_HAS_WH64() + + ahead32 = CACHE_LINE_SIZE_IN_WORDS; + + /* We already prefetched the first and last cache lines, so + * we only need to do more prefetching if we are storing + * to more than two cache lines. + */ + if (n32 > CACHE_LINE_SIZE_IN_WORDS * 2) { + int i; + + /* Prefetch the next several cache lines. + * This is the setup code for the software-pipelined + * loop below. + */ +#define MAX_PREFETCH 5 + ahead32 = n32 & -CACHE_LINE_SIZE_IN_WORDS; + if (ahead32 > MAX_PREFETCH * CACHE_LINE_SIZE_IN_WORDS) + ahead32 = MAX_PREFETCH * CACHE_LINE_SIZE_IN_WORDS; + + for (i = CACHE_LINE_SIZE_IN_WORDS; + i < ahead32; i += CACHE_LINE_SIZE_IN_WORDS) + __insn_prefetch(&out32[i]); + } + + if (n32 > ahead32) { + while (1) { + int j; + + /* Prefetch by reading one word several cache lines + * ahead. Since loads are non-blocking this will + * cause the full cache line to be read while we are + * finishing earlier cache lines. Using a store + * here causes microarchitectural performance + * problems where a victimizing store miss goes to + * the head of the retry FIFO and locks the pipe for + * a few cycles. So a few subsequent stores in this + * loop go into the retry FIFO, and then later + * stores see other stores to the same cache line + * are already in the retry FIFO and themselves go + * into the retry FIFO, filling it up and grinding + * to a halt waiting for the original miss to be + * satisfied. + */ + __insn_prefetch(&out32[ahead32]); + +#if 1 +#if CACHE_LINE_SIZE_IN_WORDS % 4 != 0 +#error "Unhandled CACHE_LINE_SIZE_IN_WORDS" +#endif + + n32 -= CACHE_LINE_SIZE_IN_WORDS; + + /* Save icache space by only partially unrolling + * this loop. + */ + for (j = CACHE_LINE_SIZE_IN_WORDS / 4; j > 0; j--) { + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + } +#else + /* Unfortunately, due to a code generator flaw this + * allocates a separate register for each of these + * stores, which requires a large number of spills, + * which makes this procedure enormously bigger + * (something like 70%) + */ + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + n32 -= 16; +#endif + + /* To save compiled code size, reuse this loop even + * when we run out of prefetching to do by dropping + * ahead32 down. + */ + if (n32 <= ahead32) { + /* Not even a full cache line left, + * so stop now. + */ + if (n32 < CACHE_LINE_SIZE_IN_WORDS) + break; + + /* Choose a small enough value that we don't + * prefetch past the end. There's no sense + * in touching cache lines we don't have to. + */ + ahead32 = CACHE_LINE_SIZE_IN_WORDS - 1; + } + } + } + +#else /* CHIP_HAS_WH64() */ + + /* Determine how many words we need to emit before the 'out32' + * pointer becomes aligned modulo the cache line size. + */ + to_align32 = + (-((uintptr_t)out32 >> 2)) & (CACHE_LINE_SIZE_IN_WORDS - 1); + + /* Only bother aligning and using wh64 if there is at least + * one full cache line to process. This check also prevents + * overrunning the end of the buffer with alignment words. + */ + if (to_align32 <= n32 - CACHE_LINE_SIZE_IN_WORDS) { + int lines_left; + + /* Align out32 mod the cache line size so we can use wh64. */ + n32 -= to_align32; + for (; to_align32 != 0; to_align32--) { + *out32 = v32; + out32++; + } + + /* Use unsigned divide to turn this into a right shift. */ + lines_left = (unsigned)n32 / CACHE_LINE_SIZE_IN_WORDS; + + do { + /* Only wh64 a few lines at a time, so we don't + * exceed the maximum number of victim lines. + */ + int x = ((lines_left < CHIP_MAX_OUTSTANDING_VICTIMS()) + ? lines_left + : CHIP_MAX_OUTSTANDING_VICTIMS()); + uint32_t *wh = out32; + int i = x; + int j; + + lines_left -= x; + + do { + __insn_wh64(wh); + wh += CACHE_LINE_SIZE_IN_WORDS; + } while (--i); + + for (j = x * (CACHE_LINE_SIZE_IN_WORDS / 4); + j != 0; j--) { + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + *out32++ = v32; + } + } while (lines_left != 0); + + /* We processed all full lines above, so only this many + * words remain to be processed. + */ + n32 &= CACHE_LINE_SIZE_IN_WORDS - 1; + } + +#endif /* CHIP_HAS_WH64() */ + + /* Now handle any leftover values. */ + if (n32 != 0) { + do { + *out32 = v32; + out32++; + } while (--n32 != 0); + } + + return s; +} +EXPORT_SYMBOL(memset); |