runtime: replace index and contains with bytealg calls

The runtime has its own implementation of string indexing. To reduce
code duplication and cognitive load, replace this with calls to the
internal/bytealg package. We can't do this on Plan 9 because it needs
string indexing in a note handler (which isn't allowed to use the
optimized bytealg version because it uses SSE), so we can't just
eliminate the index function, but this CL does down-scope it so make
it clear it's only for note handlers on Plan 9.

Change-Id: Ie1a142678262048515c481e8c26313b80c5875df
Reviewed-on: https://go-review.googlesource.com/c/go/+/244537
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

1 files changed, 0 insertions, 16 deletions

diff --git a/src/runtime/string.go b/src/runtime/string.go
index 251044231e..9a601f0094 100644
--- a/src/runtime/string.go
+++ b/src/runtime/string.go
@@ -335,22 +335,6 @@ func gostringn(p *byte, l int) string {
 	return s
 }
 
-func index(s, t string) int {
-	if len(t) == 0 {
-		return 0
-	}
-	for i := 0; i < len(s); i++ {
-		if s[i] == t[0] && hasPrefix(s[i:], t) {
-			return i
-		}
-	}
-	return -1
-}
-
-func contains(s, t string) bool {
-	return index(s, t) >= 0
-}
-
 func hasPrefix(s, prefix string) bool {
 	return len(s) >= len(prefix) && s[:len(prefix)] == prefix
 }