zcy
/
tinyriscv-openocd
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

gdb_server: use more local variables in inner loop of fetching packetstiny refactoring to allow optimisation of inner loops 

Some profiling information for arm7 16MHz GDB load operation shows
gdb_get_packet_inner() near the very top.

Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total
 time   seconds   seconds    calls  Ts/call  Ts/call  name
 52.91      2.27     2.27                             embeddedice_write_dcc
 11.89      2.78     0.51                             gdb_get_packet_inner
  8.86      3.16     0.38                             memcpy
  3.26      3.30     0.14                             idle_thread_main(unsigned int)
  3.03      3.43     0.13                             cyg_in_cksum

Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>
__archive__
Øyvind Harboe 2009-12-10 19:14:45 +01:00
parent 1c42606aea
commit 97996214f5
1 changed files with 73 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

104
src/server/gdb_server.c
View File

@ -149,30 +149,11 @@ int check_pending(struct connection *connection, int timeout_s, int *got_data)
return ERROR_OK;
}
int gdb_get_char(struct connection *connection, int* next_char)
static int gdb_get_char_inner(struct connection *connection, int* next_char)
{
struct gdb_connection *gdb_con = connection->priv;
int retval = ERROR_OK;
#ifdef _DEBUG_GDB_IO_
char *debug_buffer;
#endif
if (gdb_con->buf_cnt-- > 0)
{
*next_char = *(gdb_con->buf_p++);
if (gdb_con->buf_cnt > 0)
connection->input_pending = 1;
else
connection->input_pending = 0;
#ifdef _DEBUG_GDB_IO_
LOG_DEBUG("returned char '%c' (0x%2.2x)", *next_char, *next_char);
#endif
return ERROR_OK;
}
for (;;)
{
if (connection->service->type == CONNECTION_PIPE)
@ -257,6 +238,50 @@ int gdb_get_char(struct connection *connection, int* next_char)
return retval;
}
/**
* The cool thing about this fn is that it allows buf_p and buf_cnt to be
* held in registers in the inner loop.
*
* For small caches and embedded systems this is important!
*/
static inline int gdb_get_char_fast(struct connection *connection, int* next_char, char **buf_p, int *buf_cnt)
{
int retval = ERROR_OK;
if ((*buf_cnt)-- > 0)
{
*next_char = **buf_p;
(*buf_p)++;
if (*buf_cnt > 0)
connection->input_pending = 1;
else
connection->input_pending = 0;
#ifdef _DEBUG_GDB_IO_
LOG_DEBUG("returned char '%c' (0x%2.2x)", *next_char, *next_char);
#endif
return ERROR_OK;
}
struct gdb_connection *gdb_con = connection->priv;
gdb_con->buf_p = *buf_p;
gdb_con->buf_cnt = *buf_cnt;
retval = gdb_get_char_inner(connection, next_char);
*buf_p = gdb_con->buf_p;
*buf_cnt = gdb_con->buf_cnt;
return retval;
}
int gdb_get_char(struct connection *connection, int* next_char)
{
struct gdb_connection *gdb_con = connection->priv;
return gdb_get_char_fast(connection, next_char, &gdb_con->buf_p, &gdb_con->buf_cnt);
}
int gdb_putback_char(struct connection *connection, int last_char)
{
struct gdb_connection *gdb_con = connection->priv;
@ -461,27 +486,33 @@ static __inline__ int fetch_packet(struct connection *connection, int *checksum_
unsigned char my_checksum = 0;
char checksum[3];
int character;
int retval;
int retval = ERROR_OK;
struct gdb_connection *gdb_con = connection->priv;
my_checksum = 0;
int count = 0;
count = 0;
/* move this over into local variables to use registers and give the
* more freedom to optimize */
char *buf_p = gdb_con->buf_p;
int buf_cnt = gdb_con->buf_cnt;
for (;;)
{
/* The common case is that we have an entire packet with no escape chars.
* We need to leave at least 2 bytes in the buffer to have
* gdb_get_char() update various bits and bobs correctly.
*/
if ((gdb_con->buf_cnt > 2) && ((gdb_con->buf_cnt + count) < *len))
if ((buf_cnt > 2) && ((buf_cnt + count) < *len))
{
/* The compiler will struggle a bit with constant propagation and
* aliasing, so we help it by showing that these values do not
* change inside the loop
*/
int i;
char *buf = gdb_con->buf_p;
int run = gdb_con->buf_cnt - 2;
char *buf = buf_p;
int run = buf_cnt - 2;
i = 0;
int done = 0;
while (i < run)
@ -513,19 +544,21 @@ static __inline__ int fetch_packet(struct connection *connection, int *checksum_
buffer[count++] = character & 0xff;
}
}
gdb_con->buf_p += i;
gdb_con->buf_cnt -= i;
buf_p += i;
buf_cnt -= i;
if (done)
break;
}
if (count > *len)
{
LOG_ERROR("packet buffer too small");
return ERROR_GDB_BUFFER_TOO_SMALL;
retval = ERROR_GDB_BUFFER_TOO_SMALL;
break;
}
if ((retval = gdb_get_char(connection, &character)) != ERROR_OK)
return retval;
retval = gdb_get_char_fast(connection, &character, &buf_p, &buf_cnt);
if (retval != ERROR_OK)
break;
if (character == '#')
break;
@ -535,8 +568,11 @@ static __inline__ int fetch_packet(struct connection *connection, int *checksum_
/* data transmitted in binary mode (X packet)
* uses 0x7d as escape character */
my_checksum += character & 0xff;
if ((retval = gdb_get_char(connection, &character)) != ERROR_OK)
return retval;
retval = gdb_get_char_fast(connection, &character, &buf_p, &buf_cnt);
if (retval != ERROR_OK)
break;
my_checksum += character & 0xff;
buffer[count++] = (character ^ 0x20) & 0xff;
}
@ -547,6 +583,12 @@ static __inline__ int fetch_packet(struct connection *connection, int *checksum_
}
}
gdb_con->buf_p = buf_p;
gdb_con->buf_cnt = buf_cnt;
if (retval != ERROR_OK)
return retval;
*len = count;
if ((retval = gdb_get_char(connection, &character)) != ERROR_OK)