[llvm] [utils][filecheck-lint]: speedup filecheck_lint by caching edit distance (PR #94191)

[via llvm-commits]

https://github.com/klensy created https://github.com/llvm/llvm-project/pull/94191

For example:
clang\test\OpenMP\task_codegen.cpp:  0m29.570s -> 0m2.698s
clang\test\Driver: 4m55.917s -> 1m53.789s

Most win from big files.

>From faeba1e67bfb7822fd30f0cab6e129d28c985485 Mon Sep 17 00:00:00 2001
From: klensy <nightouser at gmail.com>
Date: Mon, 3 Jun 2024 11:08:52 +0300
Subject: [PATCH] [utils][filecheck-lint]: speedup filecheck_lint by caching
 edit_distance calculations

---
 llvm/utils/filecheck_lint/filecheck_lint.py | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/llvm/utils/filecheck_lint/filecheck_lint.py b/llvm/utils/filecheck_lint/filecheck_lint.py
index 837846db83321..d238277c9e01b 100755
--- a/llvm/utils/filecheck_lint/filecheck_lint.py
+++ b/llvm/utils/filecheck_lint/filecheck_lint.py
@@ -228,7 +228,8 @@ def find_best_match(typo):
         )
 
     potential_directives = find_potential_directives(content)
-
+    # cache score and best_match to skip recalculating
+    checked_potential_directives = dict()
     for filerange, potential_directive in potential_directives:
         # TODO(bchetioui): match count directives more finely. We skip directives
         # starting with 'CHECK-COUNT-' for the moment as they require more complex
@@ -244,7 +245,11 @@ def find_best_match(typo):
         if len(potential_directive) > max(map(len, all_directives)) + threshold:
             continue
 
-        score, best_match = find_best_match(potential_directive)
+        if potential_directive not in checked_potential_directives:
+            score, best_match = find_best_match(potential_directive)
+            checked_potential_directives[potential_directive] = (score, best_match)
+        else:
+            score, best_match = checked_potential_directives[potential_directive]
         if score == 0:  # This is an actual directive, ignore.
             continue
         elif score <= threshold and best_match not in _ignore: