On Mon, Nov 23, 2020 at 5:38 AM Ranier Vilela <ranier.vf@gmail.com> wrote:
>
> Em dom., 22 de nov. de 2020 às 18:13, Kyle Evans <kevans@freebsd.org> escreveu:
>> Note that any optimizing compiler worth its salt should be able
>> to identify that it can eliminate the strlen() call at the call sites
>> where it's a literal, providing a less-redundant interface that's
>> "optimal" (not that I think it's necessarily
>> worth it).
>
> I come from the old school, from the days of the MSDOS.
> From my first C course, one of the lessons was: don't leave anything behind.
> Indeed, compilers have evolved a lot.
> But the one who knows the code and the data best is the programmer, not the compiler.
> Then give permission to optimize and the compiler will do a better job.
> It is the same principle of using const, many do not, because the code is less readable.
>
Sure, I'll bow out here.
I would like, at least, once again, your opinion, in this example below, if you don't mind.
When the programmer knows the data, better than the compiler.
LUA API luaS_newshortstr
1. Avoid "if test" when the size of string is <
LUAI_MAXSHORTLEN.
lstring.c
@@ -185,15 +185,15 @@ static void growstrtab (lua_State *L, stringtable *tb) {
/*
** Checks whether short string exists and reuses it or creates a new one.
*/
-static TString *internshrstr (lua_State *L, const char *str, size_t l) {
+TString *luaS_newshortstr (lua_State *L, const char * const str, size_t l) {
@@ -218,9 +217,9 @@ static TString *internshrstr (lua_State *L, const char *str, size_t l) {
/*
** new string (with explicit length)
*/
- return internshrstr(L, str, l);
+ return luaS_newshortstr(L, str, l);
lapi.c
@@ -1256,7 +1256,7 @@ LUA_API void lua_concat (lua_State *L, int n) {
if (n > 0)
luaV_concat(L, n);
else { /* nothing to concatenate */
- setsvalue2s(L, L->top, luaS_newlstr(L, "", 0)); /* push empty string */
+ setsvalue2s(L, L->top, luaS_newshortstr(L, "", 0)); /* push empty string */
+++ b/lobject.c
@@ -372,9 +372,9 @@ static int tostringbuff (TValue *obj, char *buff) {
** Convert a number object to a Lua string, replacing the value at 'obj'
*/
void luaO_tostring (lua_State *L, TValue *obj) {
- char buff[MAXNUMBER2STR];
+ char buff[LUAI_MAXSHORTLEN];
int len = tostringbuff(obj, buff);
- setsvalue(L, obj, luaS_newlstr(L, buff, len));
+ setsvalue(L, obj, luaS_newshortstr(L, buff, len));
+++ b/lvm.c
/* copy strings in stack from top - n up to top - 1 to buffer */
static void copy2buff (StkId top, int n, char *buff) {
@@ -661,7 +661,7 @@ void luaV_concat (lua_State *L, int total) {
if (tl <= LUAI_MAXSHORTLEN) { /* is result a short string? */
char buff[LUAI_MAXSHORTLEN];
copy2buff(top, n, buff); /* copy strings to buffer */
- ts = luaS_newlstr(L, buff, tl);
+ ts = luaS_newshortstr(L, buff, tl);
diff --git a/lundump.c b/lundump.c
index 5aa55c44..b763d0fa 100644
--- a/lundump.c
+++ b/lundump.c
@@ -116,7 +116,7 @@ static TString *loadStringN (LoadState *S, Proto *p) {
else if (--size <= LUAI_MAXSHORTLEN) { /* short string? */
char buff[LUAI_MAXSHORTLEN];
loadVector(S, buff, size); /* load string into buffer */
- ts = luaS_newlstr(L, buff, size); /* create string */
+ ts = luaS_newshortstr(L, buff, size); /* create string */
}
else { /* long string */
ts = luaS_createlngstrobj(L, size); /* create string */
What do you think?
regards,
Ranier Vilela
