cmd/internal/gc, etc: remove dead code

Found with https://github.com/opennota/check.

Change-Id: I50c173382782fb16b15100e02c1c85610bc233a0
Reviewed-on: https://go-review.googlesource.com/7130
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>

src/cmd/5g/gsubr.go

@@ -37,11 +37,6 @@ import (
 	"fmt"
 )
 
-// TODO(rsc): Can make this bigger if we move
-// the text segment up higher in 5l for all GOOS.
-// At the same time, can raise StackBig in ../../runtime/stack.h.
-var unmappedzero int = 4096
-
 var resvd = []int{
 	arm.REG_R9,  // formerly reserved for m; might be okay to reuse now; not sure about NaCl
 	arm.REG_R10, // reserved for g

src/cmd/6g/gsubr.go

@@ -37,11 +37,6 @@ import (
 	"fmt"
 )
 
-// TODO(rsc): Can make this bigger if we move
-// the text segment up higher in 6l for all GOOS.
-// At the same time, can raise StackBig in ../../runtime/stack.h.
-var unmappedzero int64 = 4096
-
 var resvd = []int{
 	x86.REG_DI, // for movstring
 	x86.REG_SI, // for movstring

src/cmd/7g/gsubr.go

@@ -37,11 +37,6 @@ import (
 	"fmt"
 )
 
-// TODO(rsc): Can make this bigger if we move
-// the text segment up higher in 6l for all GOOS.
-// At the same time, can raise StackBig in ../../runtime/stack.h.
-var unmappedzero int64 = 4096
-
 var resvd = []int{
 	arm64.REGTMP,
 	arm64.REGG,

src/cmd/9g/gsubr.go

@@ -37,11 +37,6 @@ import (
 	"fmt"
 )
 
-// TODO(rsc): Can make this bigger if we move
-// the text segment up higher in 6l for all GOOS.
-// At the same time, can raise StackBig in ../../runtime/stack.h.
-var unmappedzero int64 = 4096
-
 var resvd = []int{
 	ppc64.REGZERO,
 	ppc64.REGSP, // reserved for SP

src/cmd/internal/gc/go.go

@@ -205,7 +205,6 @@ type Label struct {
 
 type InitEntry struct {
 	Xoffset int64 // struct, array only
-	Key     *Node // map only
 	Expr    *Node // bytes of run-time computed expressions
 }
 
@@ -245,8 +244,6 @@ type Iter struct {
 	Done  int
 	Tfunc *Type
 	T     *Type
-	An    **Node
-	N     *Node
 }
 
 const (
@@ -501,8 +498,6 @@ var Runtimepkg *Pkg // package runtime
 
 var racepkg *Pkg // package runtime/race
 
-var stringpkg *Pkg // fake package for C strings
-
 var typepkg *Pkg // fake package for runtime type info (headers)
 
 var typelinkpkg *Pkg // fake package for runtime type info (data)
@@ -513,8 +508,6 @@ var unsafepkg *Pkg // package unsafe
 
 var trackpkg *Pkg // fake package for field tracking
 
-var rawpkg *Pkg // fake package for raw symbol names
-
 var Tptr int // either TPTR32 or TPTR64
 
 var myimportpath string
@@ -673,8 +666,6 @@ var breakpc *obj.Prog
 
 var Pc *obj.Prog
 
-var firstpc *obj.Prog
-
 var nodfp *Node
 
 var Disable_checknil int

src/cmd/internal/gc/lex.go

@@ -23,8 +23,6 @@ import (
 	"unicode/utf8"
 )
 
-var yychar_lex int
-
 var yyprev int
 
 var yylast int

src/cmd/internal/gc/popt.go

@@ -520,7 +520,6 @@ type TempVar struct {
 	node    *Node
 	def     *Flow    // definition of temp var
 	use     *Flow    // use list, chained through Flow.data
-	freelink *TempVar // next free temp in Type.opt list
 	merge   *TempVar // merge var with this one
 	start   int64    // smallest Prog.pc in live range
 	end     int64    // largest Prog.pc in live range

src/cmd/internal/gc/subr.go

@@ -25,10 +25,6 @@ type Error struct {
 
 var errors []Error
 
-var nerr int
-
-var merr int
-
 func errorexit() {
 	Flusherrors()
 	if outfile != "" {