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Avoid computing strlen() inside loops

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Compiling with -O0 (no proper optimizations), strlen() call
in loops for comparing the size, isn't being called/initialized
before the actual loop gets started, which causes n-numbers of
strlen() calls (as long as the string is). Keeping the length
before entering in the loop is a good idea.

On some places, even with -O2, both GCC and Clang can't
recognize this pattern, which seem to happen in an array
of char pointer.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: rilysh <nightquick@proton.me>
Closes #16584
This commit is contained in:
rilysh 2024-10-02 21:40:06 +05:30 committed by GitHub
parent e8cbb5952d
commit 86737c5927
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
6 changed files with 28 additions and 17 deletions
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12
cmd/zdb/zdb.c
View File

@ -8800,7 +8800,7 @@ zdb_read_block(char *thing, spa_t *spa)
void *lbuf, *buf;
char *s, *p, *dup, *flagstr, *sizes, *tmp = NULL;
const char *vdev, *errmsg = NULL;
int i, error;
int i, len, error;
boolean_t borrowed = B_FALSE, found = B_FALSE;
dup = strdup(thing);
@ -8828,7 +8828,8 @@ zdb_read_block(char *thing, spa_t *spa)
for (s = strtok_r(flagstr, ":", &tmp);
s != NULL;
s = strtok_r(NULL, ":", &tmp)) {
for (i = 0; i < strlen(flagstr); i++) {
len = strlen(flagstr);
for (i = 0; i < len; i++) {
int bit = flagbits[(uchar_t)flagstr[i]];
if (bit == 0) {
@ -9098,13 +9099,14 @@ zdb_embedded_block(char *thing)
static boolean_t
zdb_numeric(char *str)
{
int i = 0;
int i = 0, len;
if (strlen(str) == 0)
len = strlen(str);
if (len == 0)
return (B_FALSE);
if (strncmp(str, "0x", 2) == 0 || strncmp(str, "0X", 2) == 0)
i = 2;
for (; i < strlen(str); i++) {
for (; i < len; i++) {
if (!isxdigit(str[i]))
return (B_FALSE);
}

8
cmd/ztest.c
View File

@ -685,15 +685,17 @@ static int
str2shift(const char *buf)
{
const char *ends = "BKMGTPEZ";
int i;
int i, len;
if (buf[0] == '\0')
return (0);
for (i = 0; i < strlen(ends); i++) {
len = strlen(ends);
for (i = 0; i < len; i++) {
if (toupper(buf[0]) == ends[i])
break;
}
if (i == strlen(ends)) {
if (i == len) {
(void) fprintf(stderr, "ztest: invalid bytes suffix: %s\n",
buf);
usage(B_FALSE);

8
lib/libzfs/libzfs_util.c
View File

@ -1618,15 +1618,17 @@ static int
str2shift(libzfs_handle_t *hdl, const char *buf)
{
const char *ends = "BKMGTPEZ";
int i;
int i, len;
if (buf[0] == '\0')
return (0);
for (i = 0; i < strlen(ends); i++) {
len = strlen(ends);
for (i = 0; i < len; i++) {
if (toupper(buf[0]) == ends[i])
break;
}
if (i == strlen(ends)) {
if (i == len) {
if (hdl)
zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
"invalid numeric suffix '%s'"), buf);

5
module/zcommon/zfs_prop.c
View File

@ -808,11 +808,12 @@ zfs_name_to_prop(const char *propname)
boolean_t
zfs_prop_user(const char *name)
{
int i;
int i, len;
char c;
boolean_t foundsep = B_FALSE;
for (i = 0; i < strlen(name); i++) {
len = strlen(name);
for (i = 0; i < len; i++) {
c = name[i];
if (!zprop_valid_char(c))
return (B_FALSE);

5
module/zcommon/zpool_prop.c
View File

@ -494,11 +494,12 @@ vdev_name_to_prop(const char *propname)
boolean_t
vdev_prop_user(const char *name)
{
int i;
int i, len;
char c;
boolean_t foundsep = B_FALSE;
for (i = 0; i < strlen(name); i++) {
len = strlen(name);
for (i = 0; i < len; i++) {
c = name[i];
if (!zprop_valid_char(c))
return (B_FALSE);

7
udev/zvol_id.c
View File

@ -56,6 +56,7 @@ main(int argc, const char *const *argv)
return (1);
}
const char *dev_name = argv[1];
size_t i, len;
int fd;
struct stat sb;
@ -73,11 +74,13 @@ main(int argc, const char *const *argv)
}
const char *dev_part = strrchr(dev_name, 'p');
len = strlen(zvol_name);
if (dev_part != NULL) {
sprintf(zvol_name + strlen(zvol_name), "-part%s", dev_part + 1);
sprintf(zvol_name + len, "-part%s", dev_part + 1);
len = strlen(zvol_name);
}
for (size_t i = 0; i < strlen(zvol_name); ++i)
for (i = 0; i < len; ++i)
if (isblank(zvol_name[i]))
zvol_name[i] = '+';