regexp: add BenchmarkFindAllTenMatches

Add a benchmark of FindAll that has matches, to complement BenchmarkFindAllNoMatches.

Change-Id: Ie910bf4913693409fde089ce6df27b13e33f2caf
Reviewed-on: https://go-review.googlesource.com/c/go/+/742800
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/regexp/all_test.go

@@ -5,6 +5,7 @@
 package regexp
 
 import (
+	"bytes"
 	"reflect"
 	"regexp/syntax"
 	"slices"
@@ -613,6 +614,19 @@ func BenchmarkFindAllNoMatches(b *testing.B) {
 	}
 }
 
+func BenchmarkFindAllTenMatches(b *testing.B) {
+	re := MustCompile("a+b+")
+	s := bytes.Repeat([]byte("acddeeabbax"), 10)
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		all := re.FindAll(s, -1)
+		if len(all) != 10 {
+			b.Fatalf("FindAll(%q) = %q; want 10 matches", s, all)
+		}
+	}
+}
+
 func BenchmarkFindString(b *testing.B) {
 	b.StopTimer()
 	re := MustCompile("a+b+")