refactor: add pure attribute to pure functions (#18165)

This will allow the compilers that support the pure attribute to make
further optimizations.

src/nvim/buffer.c

@@ -357,6 +357,7 @@ void set_bufref(bufref_T *bufref, buf_T *buf)
 ///
 /// @param bufref Buffer reference to check for.
 bool bufref_valid(bufref_T *bufref)
+  FUNC_ATTR_PURE
 {
   return bufref->br_buf_free_count == buf_free_count
     ? true
@@ -2100,6 +2101,7 @@ buf_T *buflist_findname(char_u *ffname)
 ///
 /// @return  buffer or NULL if not found
 static buf_T *buflist_findname_file_id(char_u *ffname, FileID *file_id, bool file_id_valid)
+  FUNC_ATTR_PURE
 {
   // Start at the last buffer, expect to find a match sooner.
   FOR_ALL_BUFFERS_BACKWARDS(buf) {
@@ -2531,7 +2533,7 @@ static bool wininfo_other_tab_diff(wininfo_T *wip)
 ///
 /// @return  NULL when there isn't any info.
 static wininfo_T *find_wininfo(buf_T *buf, bool need_options, bool skip_diff_buffer)
-  FUNC_ATTR_NONNULL_ALL
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
 {
   wininfo_T *wip;
 
@@ -2609,6 +2611,7 @@ void get_winopts(buf_T *buf)
 ///
 /// @return  a pointer to no_position if no position is found.
 pos_T *buflist_findfpos(buf_T *buf)
+  FUNC_ATTR_PURE
 {
   static pos_T no_position = { 1, 0, 0 };
 
@@ -2618,6 +2621,7 @@ pos_T *buflist_findfpos(buf_T *buf)
 
 /// Find the lnum for the buffer 'buf' for the current window.
 linenr_T buflist_findlnum(buf_T *buf)
+  FUNC_ATTR_PURE
 {
   return buflist_findfpos(buf)->lnum;
 }
@@ -4928,6 +4932,7 @@ void do_arg_all(int count, int forceit, int keep_tabs)
 
 /// @return  true if "buf" is a prompt buffer.
 bool bt_prompt(buf_T *buf)
+  FUNC_ATTR_PURE
 {
   return buf != NULL && buf->b_p_bt[0] == 'p';
 }
@@ -5339,6 +5344,7 @@ bool bt_dontwrite_msg(const buf_T *const buf)
 /// @return  true if the buffer should be hidden, according to 'hidden', ":hide"
 ///          and 'bufhidden'.
 bool buf_hide(const buf_T *const buf)
+  FUNC_ATTR_PURE
 {
   // 'bufhidden' overrules 'hidden' and ":hide", check it first
   switch (buf->b_p_bh[0]) {

src/nvim/charset.c

@@ -654,6 +654,7 @@ static inline unsigned nr2hex(unsigned n)
 ///
 /// @reeturn Number of display cells.
 int byte2cells(int b)
+  FUNC_ATTR_PURE
 {
   if (b >= 0x80) {
     return 0;
@@ -1176,6 +1177,7 @@ intptr_t getwhitecols_curline(void)
 }
 
 intptr_t getwhitecols(const char_u *p)
+  FUNC_ATTR_PURE
 {
   return skipwhite(p) - p;
 }
@@ -1222,6 +1224,7 @@ const char *skipbin(const char *q)
 /// @return Pointer to the character after the skipped digits and hex
 ///         characters.
 char_u *skiphex(char_u *q)
+  FUNC_ATTR_PURE
 {
   char_u *p = q;
   while (ascii_isxdigit(*p)) {
@@ -1237,6 +1240,7 @@ char_u *skiphex(char_u *q)
 ///
 /// @return Pointer to the digit or (NUL after the string).
 char_u *skiptodigit(char_u *q)
+  FUNC_ATTR_PURE
 {
   char_u *p = q;
   while (*p != NUL && !ascii_isdigit(*p)) {
@@ -1270,6 +1274,7 @@ const char *skiptobin(const char *q)
 ///
 /// @return Pointer to the hex character or (NUL after the string).
 char_u *skiptohex(char_u *q)
+  FUNC_ATTR_PURE
 {
   char_u *p = q;
   while (*p != NUL && !ascii_isxdigit(*p)) {
@@ -1285,7 +1290,7 @@ char_u *skiptohex(char_u *q)
 ///
 /// @return Pointer to the next whitespace or NUL character.
 char_u *skiptowhite(const char_u *p)
-  FUNC_ATTR_NONNULL_ALL
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE
 {
   while (*p != ' ' && *p != '\t' && *p != NUL) {
     p++;
@@ -1299,6 +1304,7 @@ char_u *skiptowhite(const char_u *p)
 ///
 /// @return Pointer to the next whitespace character.
 char_u *skiptowhite_esc(char_u *p)
+  FUNC_ATTR_PURE
 {
   while (*p != ' ' && *p != '\t' && *p != NUL) {
     if (((*p == '\\') || (*p == Ctrl_V)) && (*(p + 1) != NUL)) {
@@ -1392,6 +1398,7 @@ long getdigits_long(char_u **pp, bool strict, long def)
 ///
 /// @param  lbuf  line buffer to check
 bool vim_isblankline(char_u *lbuf)
+  FUNC_ATTR_PURE
 {
   char_u *p = skipwhite(lbuf);
   return *p == NUL || *p == '\r' || *p == '\n';
@@ -1618,6 +1625,7 @@ vim_str2nr_proceed:
 ///
 /// @return The value of the hex character.
 int hex2nr(int c)
+  FUNC_ATTR_CONST
 {
   if ((c >= 'a') && (c <= 'f')) {
     return c - 'a' + 10;
@@ -1632,6 +1640,7 @@ int hex2nr(int c)
 /// Convert two hex characters to a byte.
 /// Return -1 if one of the characters is not hex.
 int hexhex2nr(char_u *p)
+  FUNC_ATTR_PURE
 {
   if (!ascii_isxdigit(p[0]) || !ascii_isxdigit(p[1])) {
     return -1;

src/nvim/edit.c

@@ -846,6 +846,7 @@ static int insert_execute(VimState *state, int key)
 /// Don't do this when still processing a command or a mapping.
 /// Don't do this when inside a ":normal" command.
 bool goto_im(void)
+  FUNC_ATTR_PURE
 {
   return p_im && stuff_empty() && typebuf_typed();
 }
@@ -1654,7 +1655,7 @@ void edit_putchar(int c, bool highlight)
 
 /// Return the effective prompt for the specified buffer.
 char_u *buf_prompt_text(const buf_T *const buf)
-    FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
+    FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_PURE
 {
   if (buf->b_prompt_text == NULL) {
     return (char_u *)"% ";
@@ -1663,7 +1664,8 @@ char_u *buf_prompt_text(const buf_T *const buf)
 }
 
 // Return the effective prompt for the current buffer.
-char_u *prompt_text(void) FUNC_ATTR_WARN_UNUSED_RESULT
+char_u *prompt_text(void)
+  FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_PURE
 {
   return buf_prompt_text(curbuf);
 }
@@ -1711,6 +1713,7 @@ static void init_prompt(int cmdchar_todo)
 
 /// @return  true if the cursor is in the editable position of the prompt line.
 bool prompt_curpos_editable(void)
+  FUNC_ATTR_PURE
 {
   return curwin->w_cursor.lnum == curbuf->b_ml.ml_line_count
          && curwin->w_cursor.col >= (int)STRLEN(prompt_text());
@@ -2101,6 +2104,7 @@ static void ins_ctrl_x(void)
 
 // Whether other than default completion has been selected.
 bool ctrl_x_mode_not_default(void)
+  FUNC_ATTR_PURE
 {
   return ctrl_x_mode != CTRL_X_NORMAL;
 }
@@ -2108,6 +2112,7 @@ bool ctrl_x_mode_not_default(void)
 // Whether CTRL-X was typed without a following character,
 // not including when in CTRL-X CTRL-V mode.
 bool ctrl_x_mode_not_defined_yet(void)
+  FUNC_ATTR_PURE
 {
   return ctrl_x_mode == CTRL_X_NOT_DEFINED_YET;
 }
@@ -3140,6 +3145,7 @@ static void ins_compl_files(int count, char_u **files, int thesaurus, int flags,
  * Returns a pointer to the first char of the word.  Also stops at a NUL.
  */
 char_u *find_word_start(char_u *ptr)
+  FUNC_ATTR_PURE
 {
   while (*ptr != NUL && *ptr != '\n' && mb_get_class(ptr) <= 1) {
     ptr += utfc_ptr2len(ptr);
@@ -3152,6 +3158,7 @@ char_u *find_word_start(char_u *ptr)
  * Returns a pointer to just after the word.
  */
 char_u *find_word_end(char_u *ptr)
+  FUNC_ATTR_PURE
 {
   const int start_class = mb_get_class(ptr);
   if (start_class > 1) {
@@ -7144,6 +7151,7 @@ int stuff_inserted(int c, long count, int no_esc)
 }
 
 char_u *get_last_insert(void)
+  FUNC_ATTR_PURE
 {
   if (last_insert == NULL) {
     return NULL;
@@ -7690,6 +7698,7 @@ bool in_cinkeys(int keytyped, int when, bool line_is_empty)
  * Map Hebrew keyboard when in hkmap mode.
  */
 int hkmap(int c)
+  FUNC_ATTR_PURE
 {
   if (p_hkmapp) {   // phonetic mapping, by Ilya Dogolazky
     enum {

src/nvim/eval.c

@@ -5050,6 +5050,7 @@ static int get_lit_string_tv(char_u **arg, typval_T *rettv, int evaluate)
 
 /// @return  the function name of the partial.
 char_u *partial_name(partial_T *pt)
+  FUNC_ATTR_PURE
 {
   if (pt->pt_name != NULL) {
     return pt->pt_name;
@@ -8525,6 +8526,7 @@ static void check_vars(const char *name, size_t len)
 
 /// check if special v:lua value for calling lua functions
 bool is_luafunc(partial_T *partial)
+  FUNC_ATTR_PURE
 {
   return partial == vvlua_partial;
 }
@@ -9922,6 +9924,7 @@ void func_line_end(void *cookie)
 }
 
 static var_flavour_T var_flavour(char_u *varname)
+  FUNC_ATTR_PURE
 {
   char_u *p = varname;
 

src/nvim/ex_cmds.c

@@ -4969,6 +4969,7 @@ char_u *check_help_lang(char_u *arg)
 ///
 /// @return  a heuristic indicating how well the given string matches.
 int help_heuristic(char_u *matched_string, int offset, int wrong_case)
+  FUNC_ATTR_PURE
 {
   int num_letters;
   char_u *p;

src/nvim/ex_cmds2.c

@@ -201,6 +201,7 @@ static char *pexpand_cmds[] = {
 /// Function given to ExpandGeneric() to obtain the profile command
 /// specific expansion.
 char_u *get_profile_name(expand_T *xp, int idx)
+  FUNC_ATTR_PURE
 {
   switch (pexpand_what) {
   case PEXP_SUBCMD:
@@ -439,6 +440,7 @@ static void script_dump_profile(FILE *fd)
 /// @return  true when a function defined in the current script should be
 ///          profiled.
 bool prof_def_func(void)
+  FUNC_ATTR_PURE
 {
   if (current_sctx.sc_sid > 0) {
     return SCRIPT_ITEM(current_sctx.sc_sid).sn_pr_force;
@@ -1732,6 +1734,7 @@ int *source_dbg_tick(void *cookie)
 
 /// @return  the nesting level for a source cookie.
 int source_level(void *cookie)
+  FUNC_ATTR_PURE
 {
   return ((struct source_cookie *)cookie)->level;
 }
@@ -2288,6 +2291,7 @@ void free_scriptnames(void)
 #endif
 
 linenr_T get_sourced_lnum(LineGetter fgetline, void *cookie)
+  FUNC_ATTR_PURE
 {
   return fgetline == getsourceline
         ? ((struct source_cookie *)cookie)->sourcing_lnum

src/nvim/ex_eval.c

@@ -129,6 +129,7 @@ int should_abort(int retcode)
 /// to find finally clauses to be executed, and that some errors in skipped
 /// commands are still reported.
 int aborted_in_try(void)
+  FUNC_ATTR_PURE
 {
   // This function is only called after an error.  In this case, "force_abort"
   // determines whether searching for finally clauses is necessary.

src/nvim/getchar.c

@@ -397,6 +397,7 @@ static void start_stuff(void)
  * Return TRUE if the stuff buffer is empty.
  */
 int stuff_empty(void)
+  FUNC_ATTR_PURE
 {
   return (readbuf1.bh_first.b_next == NULL && readbuf2.bh_first.b_next == NULL);
 }
@@ -406,6 +407,7 @@ int stuff_empty(void)
  * redbuf2.
  */
 int readbuf1_empty(void)
+  FUNC_ATTR_PURE
 {
   return (readbuf1.bh_first.b_next == NULL);
 }
@@ -1025,10 +1027,10 @@ int ins_char_typebuf(int c, int modifier)
 ///
 /// @param tb_change_cnt  old value of typebuf.tb_change_cnt
 bool typebuf_changed(int tb_change_cnt)
+  FUNC_ATTR_PURE
 {
   return tb_change_cnt != 0 && (typebuf.tb_change_cnt != tb_change_cnt
-                                || typebuf_was_filled
+                                || typebuf_was_filled);
-                                );
 }
 
 /*
@@ -1036,6 +1038,7 @@ bool typebuf_changed(int tb_change_cnt)
  * not been typed (result from a mapping or come from ":normal").
  */
 int typebuf_typed(void)
+  FUNC_ATTR_PURE
 {
   return typebuf.tb_maplen == 0;
 }
@@ -1044,6 +1047,7 @@ int typebuf_typed(void)
  * Return the number of characters that are mapped (or not typed).
  */
 int typebuf_maplen(void)
+  FUNC_ATTR_PURE
 {
   return typebuf.tb_maplen;
 }
@@ -1403,6 +1407,7 @@ void close_all_scripts(void)
  * Return TRUE when reading keys from a script file.
  */
 int using_script(void)
+  FUNC_ATTR_PURE
 {
   return scriptin[curscript] != NULL;
 }

src/nvim/mbyte.c

@@ -334,10 +334,9 @@ enc_alias_table[] =
  * Returns -1 if not found.
  */
 static int enc_canon_search(const char_u *name)
+  FUNC_ATTR_PURE
 {
-  int i;
+  for (int i = 0; i < IDX_COUNT; i++) {
-
-  for (i = 0; i < IDX_COUNT; ++i) {
     if (STRCMP(name, enc_canon_table[i].name) == 0) {
       return i;
     }
@@ -351,10 +350,9 @@ static int enc_canon_search(const char_u *name)
  * Returns 0 if not found.
  */
 int enc_canon_props(const char_u *name)
+  FUNC_ATTR_PURE
 {
-  int i;
+  int i = enc_canon_search(name);
-
-  i = enc_canon_search(name);
   if (i >= 0) {
     return enc_canon_table[i].prop;
   } else if (STRNCMP(name, "2byte-", 6) == 0) {
@@ -373,6 +371,7 @@ int enc_canon_props(const char_u *name)
  * 3 - UTF-8 BOM
  */
 int bomb_size(void)
+  FUNC_ATTR_PURE
 {
   int n = 0;
 
@@ -414,11 +413,13 @@ void remove_bom(char_u *s)
  * >2 for other word characters
  */
 int mb_get_class(const char_u *p)
+  FUNC_ATTR_PURE
 {
   return mb_get_class_tab(p, curbuf->b_chartab);
 }
 
 int mb_get_class_tab(const char_u *p, const uint64_t *const chartab)
+  FUNC_ATTR_PURE
 {
   if (MB_BYTE2LEN(p[0]) == 1) {
     if (p[0] == NUL || ascii_iswhite(p[0])) {
@@ -436,6 +437,7 @@ int mb_get_class_tab(const char_u *p, const uint64_t *const chartab)
  * Return true if "c" is in "table".
  */
 static bool intable(const struct interval *table, size_t n_items, int c)
+  FUNC_ATTR_PURE
 {
   int mid, bot, top;
 
@@ -1087,6 +1089,7 @@ int utf_class(const int c)
 }
 
 int utf_class_tab(const int c, const uint64_t *const chartab)
+  FUNC_ATTR_PURE
 {
   // sorted list of non-overlapping intervals
   static struct clinterval {