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diff --git a/gdb/dcache.c b/gdb/dcache.c
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-/* Caching code.
- Copyright 1992, 1993, 1995, 1996, 1998, 1999, 2000, 2001
- Free Software Foundation, Inc.
-
- This file is part of GDB.
-
- 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; either version 2 of the License, or
- (at your option) any later version.
-
- 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. See the
- GNU General Public License for more details.
-
- You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software
- Foundation, Inc., 59 Temple Place - Suite 330,
- Boston, MA 02111-1307, USA. */
-
-#include "defs.h"
-#include "dcache.h"
-#include "gdbcmd.h"
-#include "gdb_string.h"
-#include "gdbcore.h"
-#include "target.h"
-
-/* The data cache could lead to incorrect results because it doesn't
- know about volatile variables, thus making it impossible to debug
- functions which use memory mapped I/O devices. Set the nocache
- memory region attribute in those cases.
-
- In general the dcache speeds up performance, some speed improvement
- comes from the actual caching mechanism, but the major gain is in
- the reduction of the remote protocol overhead; instead of reading
- or writing a large area of memory in 4 byte requests, the cache
- bundles up the requests into 32 byte (actually LINE_SIZE) chunks.
- Reducing the overhead to an eighth of what it was. This is very
- obvious when displaying a large amount of data,
-
- eg, x/200x 0
-
- caching | no yes
- ----------------------------
- first time | 4 sec 2 sec improvement due to chunking
- second time | 4 sec 0 sec improvement due to caching
-
- The cache structure is unusual, we keep a number of cache blocks
- (DCACHE_SIZE) and each one caches a LINE_SIZEed area of memory.
- Within each line we remember the address of the line (always a
- multiple of the LINE_SIZE) and a vector of bytes over the range.
- There's another vector which contains the state of the bytes.
-
- ENTRY_BAD means that the byte is just plain wrong, and has no
- correspondence with anything else (as it would when the cache is
- turned on, but nothing has been done to it.
-
- ENTRY_DIRTY means that the byte has some data in it which should be
- written out to the remote target one day, but contains correct
- data.
-
- ENTRY_OK means that the data is the same in the cache as it is in
- remote memory.
-
-
- The ENTRY_DIRTY state is necessary because GDB likes to write large
- lumps of memory in small bits. If the caching mechanism didn't
- maintain the DIRTY information, then something like a two byte
- write would mean that the entire cache line would have to be read,
- the two bytes modified and then written out again. The alternative
- would be to not read in the cache line in the first place, and just
- write the two bytes directly into target memory. The trouble with
- that is that it really nails performance, because of the remote
- protocol overhead. This way, all those little writes are bundled
- up into an entire cache line write in one go, without having to
- read the cache line in the first place.
- */
-
-/* NOTE: Interaction of dcache and memory region attributes
-
- As there is no requirement that memory region attributes be aligned
- to or be a multiple of the dcache page size, dcache_read_line() and
- dcache_write_line() must break up the page by memory region. If a
- chunk does not have the cache attribute set, an invalid memory type
- is set, etc., then the chunk is skipped. Those chunks are handled
- in target_xfer_memory() (or target_xfer_memory_partial()).
-
- This doesn't occur very often. The most common occurance is when
- the last bit of the .text segment and the first bit of the .data
- segment fall within the same dcache page with a ro/cacheable memory
- region defined for the .text segment and a rw/non-cacheable memory
- region defined for the .data segment. */
-
-/* This value regulates the number of cache blocks stored.
- Smaller values reduce the time spent searching for a cache
- line, and reduce memory requirements, but increase the risk
- of a line not being in memory */
-
-#define DCACHE_SIZE 64
-
-/* This value regulates the size of a cache line. Smaller values
- reduce the time taken to read a single byte, but reduce overall
- throughput. */
-
-#define LINE_SIZE_POWER (5)
-#define LINE_SIZE (1 << LINE_SIZE_POWER)
-
-/* Each cache block holds LINE_SIZE bytes of data
- starting at a multiple-of-LINE_SIZE address. */
-
-#define LINE_SIZE_MASK ((LINE_SIZE - 1))
-#define XFORM(x) ((x) & LINE_SIZE_MASK)
-#define MASK(x) ((x) & ~LINE_SIZE_MASK)
-
-
-#define ENTRY_BAD 0 /* data at this byte is wrong */
-#define ENTRY_DIRTY 1 /* data at this byte needs to be written back */
-#define ENTRY_OK 2 /* data at this byte is same as in memory */
-
-
-struct dcache_block
- {
- struct dcache_block *p; /* next in list */
- CORE_ADDR addr; /* Address for which data is recorded. */
- char data[LINE_SIZE]; /* bytes at given address */
- unsigned char state[LINE_SIZE]; /* what state the data is in */
-
- /* whether anything in state is dirty - used to speed up the
- dirty scan. */
- int anydirty;
-
- int refs;
- };
-
-
-/* FIXME: dcache_struct used to have a cache_has_stuff field that was
- used to record whether the cache had been accessed. This was used
- to invalidate the cache whenever caching was (re-)enabled (if the
- cache was disabled and later re-enabled, it could contain stale
- data). This was not needed because the cache is write through and
- the code that enables, disables, and deletes memory region all
- invalidate the cache.
-
- This is overkill, since it also invalidates cache lines from
- unrelated regions. One way this could be addressed by adding a
- new function that takes an address and a length and invalidates
- only those cache lines that match. */
-
-struct dcache_struct
- {
- /* free list */
- struct dcache_block *free_head;
- struct dcache_block *free_tail;
-
- /* in use list */
- struct dcache_block *valid_head;
- struct dcache_block *valid_tail;
-
- /* The cache itself. */
- struct dcache_block *the_cache;
- };
-
-static int dcache_poke_byte (DCACHE *dcache, CORE_ADDR addr, char *ptr);
-
-static int dcache_peek_byte (DCACHE *dcache, CORE_ADDR addr, char *ptr);
-
-static struct dcache_block *dcache_hit (DCACHE *dcache, CORE_ADDR addr);
-
-static int dcache_write_line (DCACHE *dcache, struct dcache_block *db);
-
-static int dcache_read_line (DCACHE *dcache, struct dcache_block *db);
-
-static struct dcache_block *dcache_alloc (DCACHE *dcache, CORE_ADDR addr);
-
-static int dcache_writeback (DCACHE *dcache);
-
-static void dcache_info (char *exp, int tty);
-
-void _initialize_dcache (void);
-
-static int dcache_enabled_p = 0;
-
-DCACHE *last_cache; /* Used by info dcache */
-
-
-/* Free all the data cache blocks, thus discarding all cached data. */
-
-void
-dcache_invalidate (DCACHE *dcache)
-{
- int i;
- dcache->valid_head = 0;
- dcache->valid_tail = 0;
-
- dcache->free_head = 0;
- dcache->free_tail = 0;
-
- for (i = 0; i < DCACHE_SIZE; i++)
- {
- struct dcache_block *db = dcache->the_cache + i;
-
- if (!dcache->free_head)
- dcache->free_head = db;
- else
- dcache->free_tail->p = db;
- dcache->free_tail = db;
- db->p = 0;
- }
-
- return;
-}
-
-/* If addr is present in the dcache, return the address of the block
- containing it. */
-
-static struct dcache_block *
-dcache_hit (DCACHE *dcache, CORE_ADDR addr)
-{
- register struct dcache_block *db;
-
- /* Search all cache blocks for one that is at this address. */
- db = dcache->valid_head;
-
- while (db)
- {
- if (MASK (addr) == db->addr)
- {
- db->refs++;
- return db;
- }
- db = db->p;
- }
-
- return NULL;
-}
-
-/* Make sure that anything in this line which needs to
- be written is. */
-
-static int
-dcache_write_line (DCACHE *dcache, register struct dcache_block *db)
-{
- CORE_ADDR memaddr;
- char *myaddr;
- int len;
- int res;
- int reg_len;
- struct mem_region *region;
-
- if (!db->anydirty)
- return 1;
-
- len = LINE_SIZE;
- memaddr = db->addr;
- myaddr = db->data;
-
- while (len > 0)
- {
- int s;
- int e;
- int dirty_len;
-
- region = lookup_mem_region(memaddr);
- if (memaddr + len < region->hi)
- reg_len = len;
- else
- reg_len = region->hi - memaddr;
-
- if (!region->attrib.cache || region->attrib.mode == MEM_RO)
- {
- memaddr += reg_len;
- myaddr += reg_len;
- len -= reg_len;
- continue;
- }
-
- while (reg_len > 0)
- {
- s = XFORM(memaddr);
- while (reg_len > 0) {
- if (db->state[s] == ENTRY_DIRTY)
- break;
- s++;
- reg_len--;
-
- memaddr++;
- myaddr++;
- len--;
- }
-
- e = s;
- while (reg_len > 0) {
- if (db->state[e] != ENTRY_DIRTY)
- break;
- e++;
- reg_len--;
- }
-
- dirty_len = e - s;
- while (dirty_len > 0)
- {
- res = do_xfer_memory(memaddr, myaddr, dirty_len, 1,
- &region->attrib);
- if (res <= 0)
- return 0;
-
- memset (&db->state[XFORM(memaddr)], ENTRY_OK, res);
- memaddr += res;
- myaddr += res;
- len -= res;
- dirty_len -= res;
- }
- }
- }
-
- db->anydirty = 0;
- return 1;
-}
-
-/* Read cache line */
-static int
-dcache_read_line (DCACHE *dcache, struct dcache_block *db)
-{
- CORE_ADDR memaddr;
- char *myaddr;
- int len;
- int res;
- int reg_len;
- struct mem_region *region;
-
- /* If there are any dirty bytes in the line, it must be written
- before a new line can be read */
- if (db->anydirty)
- {
- if (!dcache_write_line (dcache, db))
- return 0;
- }
-
- len = LINE_SIZE;
- memaddr = db->addr;
- myaddr = db->data;
-
- while (len > 0)
- {
- region = lookup_mem_region(memaddr);
- if (memaddr + len < region->hi)
- reg_len = len;
- else
- reg_len = region->hi - memaddr;
-
- if (!region->attrib.cache || region->attrib.mode == MEM_WO)
- {
- memaddr += reg_len;
- myaddr += reg_len;
- len -= reg_len;
- continue;
- }
-
- while (reg_len > 0)
- {
- res = do_xfer_memory (memaddr, myaddr, reg_len, 0,
- &region->attrib);
- if (res <= 0)
- return 0;
-
- memaddr += res;
- myaddr += res;
- len -= res;
- reg_len -= res;
- }
- }
-
- memset (db->state, ENTRY_OK, sizeof (db->data));
- db->anydirty = 0;
-
- return 1;
-}
-
-/* Get a free cache block, put or keep it on the valid list,
- and return its address. */
-
-static struct dcache_block *
-dcache_alloc (DCACHE *dcache, CORE_ADDR addr)
-{
- register struct dcache_block *db;
-
- /* Take something from the free list */
- db = dcache->free_head;
- if (db)
- {
- dcache->free_head = db->p;
- }
- else
- {
- /* Nothing left on free list, so grab one from the valid list */
- db = dcache->valid_head;
-
- if (!dcache_write_line (dcache, db))
- return NULL;
-
- dcache->valid_head = db->p;
- }
-
- db->addr = MASK(addr);
- db->refs = 0;
- db->anydirty = 0;
- memset (db->state, ENTRY_BAD, sizeof (db->data));
-
- /* append this line to end of valid list */
- if (!dcache->valid_head)
- dcache->valid_head = db;
- else
- dcache->valid_tail->p = db;
- dcache->valid_tail = db;
- db->p = 0;
-
- return db;
-}
-
-/* Writeback any dirty lines. */
-static int
-dcache_writeback (DCACHE *dcache)
-{
- struct dcache_block *db;
-
- db = dcache->valid_head;
-
- while (db)
- {
- if (!dcache_write_line (dcache, db))
- return 0;
- db = db->p;
- }
- return 1;
-}
-
-
-/* Using the data cache DCACHE return the contents of the byte at
- address ADDR in the remote machine.
-
- Returns 0 on error. */
-
-static int
-dcache_peek_byte (DCACHE *dcache, CORE_ADDR addr, char *ptr)
-{
- register struct dcache_block *db = dcache_hit (dcache, addr);
-
- if (!db)
- {
- db = dcache_alloc (dcache, addr);
- if (!db)
- return 0;
- }
-
- if (db->state[XFORM (addr)] == ENTRY_BAD)
- {
- if (!dcache_read_line(dcache, db))
- return 0;
- }
-
- *ptr = db->data[XFORM (addr)];
- return 1;
-}
-
-
-/* Write the byte at PTR into ADDR in the data cache.
- Return zero on write error.
- */
-
-static int
-dcache_poke_byte (DCACHE *dcache, CORE_ADDR addr, char *ptr)
-{
- register struct dcache_block *db = dcache_hit (dcache, addr);
-
- if (!db)
- {
- db = dcache_alloc (dcache, addr);
- if (!db)
- return 0;
- }
-
- db->data[XFORM (addr)] = *ptr;
- db->state[XFORM (addr)] = ENTRY_DIRTY;
- db->anydirty = 1;
- return 1;
-}
-
-/* Initialize the data cache. */
-DCACHE *
-dcache_init (void)
-{
- int csize = sizeof (struct dcache_block) * DCACHE_SIZE;
- DCACHE *dcache;
-
- dcache = (DCACHE *) xmalloc (sizeof (*dcache));
-
- dcache->the_cache = (struct dcache_block *) xmalloc (csize);
- memset (dcache->the_cache, 0, csize);
-
- dcache_invalidate (dcache);
-
- last_cache = dcache;
- return dcache;
-}
-
-/* Free a data cache */
-void
-dcache_free (DCACHE *dcache)
-{
- if (last_cache == dcache)
- last_cache = NULL;
-
- xfree (dcache->the_cache);
- xfree (dcache);
-}
-
-/* Read or write LEN bytes from inferior memory at MEMADDR, transferring
- to or from debugger address MYADDR. Write to inferior if SHOULD_WRITE is
- nonzero.
-
- Returns length of data written or read; 0 for error.
-
- This routine is indended to be called by remote_xfer_ functions. */
-
-int
-dcache_xfer_memory (DCACHE *dcache, CORE_ADDR memaddr, char *myaddr, int len,
- int should_write)
-{
- int i;
- int (*xfunc) (DCACHE *dcache, CORE_ADDR addr, char *ptr);
- xfunc = should_write ? dcache_poke_byte : dcache_peek_byte;
-
- for (i = 0; i < len; i++)
- {
- if (!xfunc (dcache, memaddr + i, myaddr + i))
- return 0;
- }
-
- /* FIXME: There may be some benefit from moving the cache writeback
- to a higher layer, as it could occur after a sequence of smaller
- writes have been completed (as when a stack frame is constructed
- for an inferior function call). Note that only moving it up one
- level to target_xfer_memory() (also target_xfer_memory_partial())
- is not sufficent, since we want to coalesce memory transfers that
- are "logically" connected but not actually a single call to one
- of the memory transfer functions. */
-
- if (should_write)
- dcache_writeback (dcache);
-
- return len;
-}
-
-static void
-dcache_info (char *exp, int tty)
-{
- struct dcache_block *p;
-
- printf_filtered ("Dcache line width %d, depth %d\n",
- LINE_SIZE, DCACHE_SIZE);
-
- if (last_cache)
- {
- printf_filtered ("Cache state:\n");
-
- for (p = last_cache->valid_head; p; p = p->p)
- {
- int j;
- printf_filtered ("Line at %s, referenced %d times\n",
- paddr (p->addr), p->refs);
-
- for (j = 0; j < LINE_SIZE; j++)
- printf_filtered ("%02x", p->data[j] & 0xFF);
- printf_filtered ("\n");
-
- for (j = 0; j < LINE_SIZE; j++)
- printf_filtered ("%2x", p->state[j]);
- printf_filtered ("\n");
- }
- }
-}
-
-void
-_initialize_dcache (void)
-{
- add_show_from_set
- (add_set_cmd ("remotecache", class_support, var_boolean,
- (char *) &dcache_enabled_p,
- "\
-Set cache use for remote targets.\n\
-When on, use data caching for remote targets. For many remote targets\n\
-this option can offer better throughput for reading target memory.\n\
-Unfortunately, gdb does not currently know anything about volatile\n\
-registers and thus data caching will produce incorrect results with\n\
-volatile registers are in use. By default, this option is off.",
- &setlist),
- &showlist);
-
- add_info ("dcache", dcache_info,
- "Print information on the dcache performance.");
-
-}
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