cmd/link/internal/ld: use strings.Cut

Change-Id: I724fe76983ea259f12f073376d591c2f4b3c3d72
GitHub-Last-Rev: e61e865ba97a52d24d3aee7642f5804916e94544
GitHub-Pull-Request: golang/go#55910
Reviewed-on: https://go-review.googlesource.com/c/go/+/435738
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Run-TryBot: shuang cui <imcusg@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/link/internal/ld/go.go

@@ -50,11 +50,7 @@ func ldpkg(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, filename s
 	// process header lines
 	for data != "" {
 		var line string
-		if i := strings.Index(data, "\n"); i >= 0 {
+		line, data, _ = strings.Cut(data, "\n")
-			line, data = data[:i], data[i+1:]
-		} else {
-			line, data = data, ""
-		}
 		if line == "main" {
 			lib.Main = true
 		}
@@ -141,8 +137,8 @@ func setCgoAttr(ctxt *Link, file string, pkg string, directives [][]string, host
 			}
 
 			q := ""
-			if i := strings.Index(remote, "#"); i >= 0 {
+			if before, after, found := strings.Cut(remote, "#"); found {
-				remote, q = remote[:i], remote[i+1:]
+				remote, q = before, after
 			}
 			s := l.LookupOrCreateSym(local, 0)
 			st := l.SymType(s)

src/cmd/link/internal/ld/ld.go

@@ -62,15 +62,13 @@ func (ctxt *Link) readImportCfg(file string) {
 			continue
 		}
 
-		var verb, args string
+		verb, args, found := strings.Cut(line, " ")
-		if i := strings.Index(line, " "); i < 0 {
+		if found {
-			verb = line
+			args = strings.TrimSpace(args)
-		} else {
-			verb, args = line[:i], strings.TrimSpace(line[i+1:])
 		}
-		var before, after string
+		before, after, exist := strings.Cut(args, "=")
-		if i := strings.Index(args, "="); i >= 0 {
+		if !exist {
-			before, after = args[:i], args[i+1:]
+			before = ""
 		}
 		switch verb {
 		default: