cmd/compile/internal/ssa: use recently agreed upon generated code header

Updates #13560

Change-Id: I9bc08ca5cf0627e653d55f748ebb83be8b69ea3b
Reviewed-on: https://go-review.googlesource.com/39296
Run-TryBot: Brad Fitzpatrick <[email protected]>
Reviewed-by: Rob Pike <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>

Author: bradfitz

src/cmd/compile/internal/ssa/gen/main.go

@@ -95,8 +95,7 @@ func main() {
 
 func genOp() {
 	w := new(bytes.Buffer)
-	fmt.Fprintf(w, "// autogenerated: do not edit!\n")
-	fmt.Fprintf(w, "// generated from gen/*Ops.go\n")
+	fmt.Fprintf(w, "// Code generated from gen/*Ops.go; DO NOT EDIT.\n")
 	fmt.Fprintln(w)
 	fmt.Fprintln(w, "package ssa")
 

src/cmd/compile/internal/ssa/gen/rulegen.go

@@ -148,7 +148,7 @@ func genRules(arch arch) {
 
 	// Start output buffer, write header.
 	w := new(bytes.Buffer)
-	fmt.Fprintf(w, "// autogenerated from gen/%s.rules: do not edit!\n", arch.name)
+	fmt.Fprintf(w, "// Code generated from gen/%s.rules; DO NOT EDIT.\n", arch.name)
 	fmt.Fprintln(w, "// generated with: cd gen; go run *.go")
 	fmt.Fprintln(w)
 	fmt.Fprintln(w, "package ssa")