refactor(hashy): use case labels instead of TOLOWER_ASC() (#32795)

Follow-up to #32768

This is slightly faster according to the benchmark.

This also makes it a build error if hashy is used incorrectly
(generating a case-insensitive hash function from mixed-case strings),
as duplicate case labels aren't allowed.

1 files changed, 13 insertions, 7 deletions

diff --git a/src/gen/hashy.lua b/src/gen/hashy.lua
index 7fdb00699f..52cc1e64e3 100644
--- a/src/gen/hashy.lua
+++ b/src/gen/hashy.lua
@@ -54,7 +54,7 @@ function M.build_pos_hash(strings)
   return len_pos_buckets, maxlen, worst_buck_size
 end
 
-function M.switcher(put, tab, maxlen, worst_buck_size, lower)
+function M.switcher(put, tab, maxlen, worst_buck_size, icase)
   local neworder = {} --- @type string[]
   put '  switch (len) {\n'
   local bucky = worst_buck_size > 1
@@ -66,13 +66,17 @@ function M.switcher(put, tab, maxlen, worst_buck_size, lower)
       local keys = vim.tbl_keys(posbuck)
       if #keys > 1 then
         table.sort(keys)
-        put(('switch (%s(str[%s])) {\n'):format(lower and 'TOLOWER_ASC' or '', pos - 1))
+        put('switch (str[' .. (pos - 1) .. ']) {\n')
         for _, c in ipairs(keys) do
           local buck = posbuck[c]
           local startidx = #neworder
           vim.list_extend(neworder, buck)
           local endidx = #neworder
-          put("      case '" .. c .. "': ")
+          if icase and c:upper() ~= c:lower() then
+            put(("      case '%s': case '%s': "):format(c:upper(), c:lower()))
+          else
+            put(("      case '%s': "):format(c))
+          end
           if len == 1 then
             put('return ' .. startidx .. ';\n')
           else
@@ -102,7 +106,9 @@ function M.switcher(put, tab, maxlen, worst_buck_size, lower)
   return neworder
 end
 
-function M.hashy_hash(name, strings, access, lower)
+--- @param icase boolean generate a case-insensitive hash function.
+---                      `strings` must not have mixed case when using this.
+function M.hashy_hash(name, strings, access, icase)
   local stats = {}
   local put = function(str)
     table.insert(stats, str)
@@ -116,7 +122,7 @@ function M.hashy_hash(name, strings, access, lower)
   else
     put('  int low = -1;\n')
   end
-  local neworder = M.switcher(put, len_pos_buckets, maxlen, worst_buck_size, lower)
+  local neworder = M.switcher(put, len_pos_buckets, maxlen, worst_buck_size, icase)
   if maxlen == 1 then
     put([[
   return -1;
@@ -129,14 +135,14 @@ function M.hashy_hash(name, strings, access, lower)
     }
   }
   return -1;
-]]):format(lower and 'vim_strnicmp_asc' or 'memcmp', access('i')))
+]]):format(icase and 'vim_strnicmp_asc' or 'memcmp', access('i')))
   else
     put(([[
   if (low < 0 || %s(str, %s, len)) {
     return -1;
   }
   return low;
-]]):format(lower and 'vim_strnicmp_asc' or 'memcmp', access('low')))
+]]):format(icase and 'vim_strnicmp_asc' or 'memcmp', access('low')))
   end
   put '}\n\n'
   return neworder, table.concat(stats)