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>

src/runtime/os_plan9.go

@@ -82,10 +82,10 @@ func sigpanic() {
 	note := gostringnocopy((*byte)(unsafe.Pointer(g.m.notesig)))
 	switch g.sig {
 	case _SIGRFAULT, _SIGWFAULT:
-		i := index(note, "addr=")
+		i := indexNoFloat(note, "addr=")
 		if i >= 0 {
 			i += 5
-		} else if i = index(note, "va="); i >= 0 {
+		} else if i = indexNoFloat(note, "va="); i >= 0 {
 			i += 3
 		} else {
 			panicmem()
@@ -111,6 +111,20 @@ func sigpanic() {
 	}
 }
 
+// indexNoFloat is bytealg.IndexString but safe to use in a note
+// handler.
+func indexNoFloat(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 atolwhex(p string) int64 {
 	for hasPrefix(p, " ") || hasPrefix(p, "\t") {
 		p = p[1:]

src/runtime/proc.go

@@ -5,6 +5,7 @@
 package runtime
 
 import (
+	"internal/bytealg"
 	"internal/cpu"
 	"runtime/internal/atomic"
 	"runtime/internal/sys"
@@ -5460,7 +5461,7 @@ func haveexperiment(name string) bool {
 	x := sys.Goexperiment
 	for x != "" {
 		xname := ""
-		i := index(x, ",")
+		i := bytealg.IndexByteString(x, ',')
 		if i < 0 {
 			xname, x = x, ""
 		} else {

src/runtime/runtime1.go

@@ -5,6 +5,7 @@
 package runtime
 
 import (
+	"internal/bytealg"
 	"runtime/internal/atomic"
 	"runtime/internal/sys"
 	"unsafe"
@@ -347,13 +348,13 @@ func parsedebugvars() {
 
 	for p := gogetenv("GODEBUG"); p != ""; {
 		field := ""
-		i := index(p, ",")
+		i := bytealg.IndexByteString(p, ',')
 		if i < 0 {
 			field, p = p, ""
 		} else {
 			field, p = p[:i], p[i+1:]
 		}
-		i = index(field, "=")
+		i = bytealg.IndexByteString(field, '=')
 		if i < 0 {
 			continue
 		}

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
 }

src/runtime/traceback.go

@@ -5,6 +5,7 @@
 package runtime
 
 import (
+	"internal/bytealg"
 	"runtime/internal/atomic"
 	"runtime/internal/sys"
 	"unsafe"
@@ -848,7 +849,7 @@ func showfuncinfo(f funcInfo, firstFrame bool, funcID, childID funcID) bool {
 		return true
 	}
 
-	return contains(name, ".") && (!hasPrefix(name, "runtime.") || isExportedRuntime(name))
+	return bytealg.IndexByteString(name, '.') >= 0 && (!hasPrefix(name, "runtime.") || isExportedRuntime(name))
 }
 
 // isExportedRuntime reports whether name is an exported runtime function.