cmd/asm: make asm -S flag consistent with compile -S flag

Change things so that the -S command line option for the assembler
works the same as -S in the compiler, e.g. you can use -S=2 to
get additional detail.

Change-Id: I7bdfba39a98e67c7ae4b93019e171b188bb99a2d
Reviewed-on: https://go-review.googlesource.com/c/go/+/255717
Trust: Than McIntosh <thanm@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

src/cmd/asm/internal/flags/flags.go

@@ -17,7 +17,6 @@ import (
 var (
 	Debug      = flag.Bool("debug", false, "dump instructions as they are parsed")
 	OutputFile = flag.String("o", "", "output file; default foo.o for /a/b/c/foo.s as first argument")
-	PrintOut   = flag.Bool("S", false, "print assembly and machine code")
 	TrimPath   = flag.String("trimpath", "", "remove prefix from recorded source file paths")
 	Shared     = flag.Bool("shared", false, "generate code that can be linked into a shared library")
 	Dynlink    = flag.Bool("dynlink", false, "support references to Go symbols defined in other shared libraries")
@@ -28,14 +27,16 @@ var (
 )
 
 var (
-	D MultiFlag
+	D        MultiFlag
-	I MultiFlag
+	I        MultiFlag
+	PrintOut int
 )
 
 func init() {
 	flag.Var(&D, "D", "predefined symbol with optional simple value -D=identifier=value; can be set multiple times")
 	flag.Var(&I, "I", "include directory; can be set multiple times")
 	objabi.AddVersionFlag() // -V
+	objabi.Flagcount("S", "print assembly and machine code", &PrintOut)
 }
 
 // MultiFlag allows setting a value multiple times to collect a list, as in -I=dir1 -I=dir2.

src/cmd/asm/main.go

@@ -35,9 +35,7 @@ func main() {
 	flags.Parse()
 
 	ctxt := obj.Linknew(architecture.LinkArch)
-	if *flags.PrintOut {
+	ctxt.Debugasm = flags.PrintOut
-		ctxt.Debugasm = 1
-	}
 	ctxt.Flag_dynlink = *flags.Dynlink
 	ctxt.Flag_shared = *flags.Shared || *flags.Dynlink
 	ctxt.IsAsm = true