cmd/compile: use std "DO NOT EDIT" comment for generated files

Also: Fix (testdata/gen/) copyGen.go, zeroGen.go, and arithConstGen.go
to actually match (testdata/) copy.go, zero.go, and arithConst.go, all
of which were manually edited in https://go-review.googlesource.com/20823
and https://go-review.googlesource.com/22748 despite the 'do not edit'
(or perhaps because it was missing in the case of arithConst.go).

For #13560.

Change-Id: I366e1b521e51885e0d318ae848760e5e14ccd488
Reviewed-on: https://go-review.googlesource.com/39172Reviewed-by: Rob Pike <r@golang.org>

src/cmd/compile/internal/gc/builtin.go

-// AUTO-GENERATED by mkbuiltin.go; DO NOT EDIT
+// Code generated by mkbuiltin.go. DO NOT EDIT.
 
 package gc
 

src/cmd/compile/internal/gc/constFold_test.go

+// run
+// Code generated by gen/constFoldGen.go. DO NOT EDIT.
+
 package gc
 
 import "testing"

src/cmd/compile/internal/gc/mkbuiltin.go

@@ -31,7 +31,7 @@ func main() {
 	flag.Parse()
 
 	var b bytes.Buffer
-	fmt.Fprintln(&b, "// AUTO-GENERATED by mkbuiltin.go; DO NOT EDIT")
+	fmt.Fprintln(&b, "// Code generated by mkbuiltin.go. DO NOT EDIT.")
 	fmt.Fprintln(&b)
 	fmt.Fprintln(&b, "package gc")
 

src/cmd/compile/internal/gc/testdata/arithBoundary.go

+// run
+// Code generated by gen/arithBoundaryGen.go. DO NOT EDIT.
+
 package main
 
 import "fmt"

src/cmd/compile/internal/gc/testdata/arithConst.go

+// run
+// Code generated by gen/arithConstGen.go. DO NOT EDIT.
+
 package main
 
 import "fmt"

src/cmd/compile/internal/gc/testdata/copy.go

 // run
-// autogenerated from gen/copyGen.go - do not edit!
+// Code generated by gen/copyGen.go. DO NOT EDIT.
+
 package main
 
 import "fmt"

src/cmd/compile/internal/gc/testdata/gen/arithBoundaryGen.go

@@ -90,8 +90,9 @@ type op struct {
 var ops = []op{op{"add", "+"}, op{"sub", "-"}, op{"div", "/"}, op{"mod", "%%"}, op{"mul", "*"}}
 
 func main() {
-
 	w := new(bytes.Buffer)
+	fmt.Fprintf(w, "// run\n")
+	fmt.Fprintf(w, "// Code generated by gen/arithBoundaryGen.go. DO NOT EDIT.\n\n")
 	fmt.Fprintf(w, "package main;\n")
 	fmt.Fprintf(w, "import \"fmt\"\n")
 

src/cmd/compile/internal/gc/testdata/gen/arithConstGen.go

@@ -30,24 +30,31 @@ type szD struct {
 	i    []int64
 }
 
-var szs []szD = []szD{
-	szD{name: "uint64", sn: "64", u: []uint64{0, 1, 4294967296, 0xffffFFFFffffFFFF}},
-	szD{name: "int64", sn: "64", i: []int64{-0x8000000000000000, -0x7FFFFFFFFFFFFFFF,
+var szs = []szD{
+	{name: "uint64", sn: "64", u: []uint64{0, 1, 4294967296, 0xffffFFFFffffFFFF}},
+	{name: "int64", sn: "64", i: []int64{-0x8000000000000000, -0x7FFFFFFFFFFFFFFF,
 		-4294967296, -1, 0, 1, 4294967296, 0x7FFFFFFFFFFFFFFE, 0x7FFFFFFFFFFFFFFF}},
 
-	szD{name: "uint32", sn: "32", u: []uint64{0, 1, 4294967295}},
-	szD{name: "int32", sn: "32", i: []int64{-0x80000000, -0x7FFFFFFF, -1, 0,
+	{name: "uint32", sn: "32", u: []uint64{0, 1, 4294967295}},
+	{name: "int32", sn: "32", i: []int64{-0x80000000, -0x7FFFFFFF, -1, 0,
 		1, 0x7FFFFFFF}},
 
-	szD{name: "uint16", sn: "16", u: []uint64{0, 1, 65535}},
-	szD{name: "int16", sn: "16", i: []int64{-32768, -32767, -1, 0, 1, 32766, 32767}},
+	{name: "uint16", sn: "16", u: []uint64{0, 1, 65535}},
+	{name: "int16", sn: "16", i: []int64{-32768, -32767, -1, 0, 1, 32766, 32767}},
 
-	szD{name: "uint8", sn: "8", u: []uint64{0, 1, 255}},
-	szD{name: "int8", sn: "8", i: []int64{-128, -127, -1, 0, 1, 126, 127}},
+	{name: "uint8", sn: "8", u: []uint64{0, 1, 255}},
+	{name: "int8", sn: "8", i: []int64{-128, -127, -1, 0, 1, 126, 127}},
 }
 
-var ops []op = []op{op{"add", "+"}, op{"sub", "-"}, op{"div", "/"}, op{"mul", "*"},
-	op{"lsh", "<<"}, op{"rsh", ">>"}, op{"mod", "%"}}
+var ops = []op{
+	{"add", "+"},
+	{"sub", "-"},
+	{"div", "/"},
+	{"mul", "*"},
+	{"lsh", "<<"},
+	{"rsh", ">>"},
+	{"mod", "%"},
+}
 
 // compute the result of i op j, cast as type t.
 func ansU(i, j uint64, t, op string) string {
@@ -118,9 +125,9 @@ func ansS(i, j int64, t, op string) string {
 }
 
 func main() {
-
 	w := new(bytes.Buffer)
-
+	fmt.Fprintf(w, "// run\n")
+	fmt.Fprintf(w, "// Code generated by gen/arithConstGen.go. DO NOT EDIT.\n\n")
 	fmt.Fprintf(w, "package main;\n")
 	fmt.Fprintf(w, "import \"fmt\"\n")
 
@@ -160,7 +167,14 @@ func main() {
 
 					// avoid division by zero
 					if o.name != "mod" && o.name != "div" || i != 0 {
+						// introduce uint64 cast for rhs shift operands
+						// if they are too large for default uint type
+						number := fd.Number
+						if (o.name == "lsh" || o.name == "rsh") && uint64(uint32(i)) != i {
+							fd.Number = fmt.Sprintf("uint64(%s)", number)
+						}
 						fncCnst1.Execute(w, fd)
+						fd.Number = number
 					}
 
 					fncCnst2.Execute(w, fd)

src/cmd/compile/internal/gc/testdata/gen/constFoldGen.go

@@ -118,9 +118,9 @@ func ansS(i, j int64, t, op string) string {
 }
 
 func main() {
-
 	w := new(bytes.Buffer)
-
+	fmt.Fprintf(w, "// run\n")
+	fmt.Fprintf(w, "// Code generated by gen/constFoldGen.go. DO NOT EDIT.\n\n")
 	fmt.Fprintf(w, "package gc\n")
 	fmt.Fprintf(w, "import \"testing\"\n")
 

src/cmd/compile/internal/gc/testdata/gen/copyGen.go

@@ -23,7 +23,7 @@ var sizes = [...]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 16, 17, 23, 24, 25, 31,
 func main() {
 	w := new(bytes.Buffer)
 	fmt.Fprintf(w, "// run\n")
-	fmt.Fprintf(w, "// autogenerated from gen/copyGen.go - do not edit!\n")
+	fmt.Fprintf(w, "// Code generated by gen/copyGen.go. DO NOT EDIT.\n\n")
 	fmt.Fprintf(w, "package main\n")
 	fmt.Fprintf(w, "import \"fmt\"\n")
 
@@ -36,8 +36,8 @@ func main() {
 		fmt.Fprintf(w, "}\n")
 
 		// function being tested
+		fmt.Fprintf(w, "//go:noinline\n")
 		fmt.Fprintf(w, "func t%dcopy_ssa(y, x *[%d]byte) {\n", s, s)
-		fmt.Fprintf(w, "  switch{}\n")
 		fmt.Fprintf(w, "  *y = *x\n")
 		fmt.Fprintf(w, "}\n")
 

src/cmd/compile/internal/gc/testdata/gen/zeroGen.go

@@ -23,7 +23,7 @@ var sizes = [...]int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 16, 17, 23, 24, 25, 31,
 func main() {
 	w := new(bytes.Buffer)
 	fmt.Fprintf(w, "// run\n")
-	fmt.Fprintf(w, "// autogenerated from gen/zeroGen.go - do not edit!\n")
+	fmt.Fprintf(w, "// Code generated by gen/zeroGen.go. DO NOT EDIT.\n\n")
 	fmt.Fprintf(w, "package main\n")
 	fmt.Fprintf(w, "import \"fmt\"\n")
 
@@ -36,8 +36,8 @@ func main() {
 		fmt.Fprintf(w, "}\n")
 
 		// function being tested
+		fmt.Fprintf(w, "//go:noinline\n")
 		fmt.Fprintf(w, "func zero%d_ssa(x *[%d]byte) {\n", s, s)
-		fmt.Fprintf(w, "  switch{}\n")
 		fmt.Fprintf(w, "  *x = [%d]byte{}\n", s)
 		fmt.Fprintf(w, "}\n")
 

src/cmd/compile/internal/gc/testdata/zero.go

 // run
-// autogenerated from gen/zeroGen.go - do not edit!
+// Code generated by gen/zeroGen.go. DO NOT EDIT.
+
 package main
 
 import "fmt"