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-rw-r--r--arch/tile/lib/memset_32.c275
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 000000000000..bfde5d864df1
--- /dev/null
+++ b/arch/tile/lib/memset_32.c
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+/*
+ * 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);