Merge pull request #17908 from roidelapluie/roidelapluie/cpsimplify

[Backport 3.5LTS] [PERF] Regex: stop calling Simplify

model/labels/matcher_test.go

@@ -225,6 +225,13 @@ func BenchmarkNewMatcher(b *testing.B) {
 			NewMatcher(MatchRegexp, "foo", "bar")
 		}
 	})
+	b.Run("complex regex", func(b *testing.B) {
+		b.ReportAllocs()
+		b.ResetTimer()
+		for i := 0; i <= b.N; i++ {
+			NewMatcher(MatchRegexp, "foo", "((.*)(bar|b|buzz)(.+)|foo){10}")
+		}
+	})
 }
 
 func BenchmarkMatcher_String(b *testing.B) {

model/labels/regexp.go

@@ -67,8 +67,6 @@ func NewFastRegexMatcher(v string) (*FastRegexMatcher, error) {
 		if err != nil {
 			return nil, err
 		}
-		// Simplify the syntax tree to run faster.
-		parsed = parsed.Simplify()
 		m.re, err = regexp.Compile("^(?s:" + parsed.String() + ")$")
 		if err != nil {
 			return nil, err