bug#60953: The :match predicate with large regexp in tree-sitter font-lock seems inefficient

[Dmitry Gutov <dgutov@yandex.ru>]

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On 31/01/2023 20:16, Dmitry Gutov wrote:
> Anyway, it seems like it might be too late as an addition to Emacs 29. 
> And we can implement the match predicate using narrowing for this 
> release, to be updated later.

So here. I've installed the first patch, which didn't raise up too many 
concerns previously, and here's the new iteration on the second patch. 
Please see the attachment.

To note the numbers: the first patch does quite well to improve the 
performance of modes which use :match in queries which match a lot of 
nodes (e.g. rust-ts-mode or ruby-ts-mode). There boost in those was on 
the order of 25%.

The second one is longer, and the boost (on top of the first one) is 
around 5-6%, stable. Not as impressive, but at least it brings :match's 
performance a little above :pred's in my example.

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diff --git a/src/treesit.c b/src/treesit.c
index b163685419f..510170ca640 100644
--- a/src/treesit.c
+++ b/src/treesit.c
@@ -2466,10 +2466,41 @@ treesit_predicate_match (Lisp_Object args, struct capture_range captures)
 	      build_string ("The second argument to `match' should "
 		            "be a capture name, not a string"));
 
-  Lisp_Object text = treesit_predicate_capture_name_to_text (capture_name,
+  Lisp_Object node = treesit_predicate_capture_name_to_node (capture_name,
 							     captures);
 
-  if (fast_string_match (regexp, text) >= 0)
+  struct buffer *old_buffer = current_buffer;
+  struct buffer *buffer = XBUFFER (XTS_PARSER (XTS_NODE (node)->parser)->buffer);
+  set_buffer_internal (buffer);
+
+  TSNode treesit_node = XTS_NODE (node)->node;
+  ptrdiff_t visible_beg = XTS_PARSER (XTS_NODE (node)->parser)->visible_beg;
+  uint32_t start_byte_offset = ts_node_start_byte (treesit_node);
+  uint32_t end_byte_offset = ts_node_end_byte (treesit_node);
+  ptrdiff_t start_byte = visible_beg + start_byte_offset;
+  ptrdiff_t end_byte = visible_beg + end_byte_offset;
+  ptrdiff_t start_pos = buf_bytepos_to_charpos (buffer, start_byte);
+  ptrdiff_t end_pos = buf_bytepos_to_charpos (buffer, end_byte);
+  ptrdiff_t old_begv = BEGV;
+  ptrdiff_t old_begv_byte = BEGV_BYTE;
+  ptrdiff_t old_zv = ZV;
+  ptrdiff_t old_zv_byte = ZV_BYTE;
+
+  BEGV = start_pos;
+  BEGV_BYTE = start_byte;
+  ZV = end_pos;
+  ZV_BYTE = end_byte;
+
+  ptrdiff_t val = fast_looking_at (regexp, start_pos, start_byte, end_pos, end_byte, Qnil);
+
+  BEGV = old_begv;
+  BEGV_BYTE = old_begv_byte;
+  ZV = old_zv;
+  ZV_BYTE = old_zv_byte;
+
+  set_buffer_internal (old_buffer);
+
+  if (val > 0)
     return true;
   else
     return false;