[dev.inline] cmd/internal/src: introduce NoPos and use it instead Pos{}

Using a variable instead of a composite literal makes
the code independent of implementation changes of Pos.

Per David Lazar's suggestion.

Change-Id: I336967ac12a027c51a728a58ac6207cb5119af4a
Reviewed-on: https://go-review.googlesource.com/34148
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -511,7 +511,7 @@ func orderstmt(n *Node, order *Order) {
 
 		n.Left = orderexpr(n.Left, order, nil)
 		n.Left = ordersafeexpr(n.Left, order)
-		tmp1 := treecopy(n.Left, src.Pos{})
+		tmp1 := treecopy(n.Left, src.NoPos)
 		if tmp1.Op == OINDEXMAP {
 			tmp1.Etype = 0 // now an rvalue not an lvalue
 		}

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

@@ -496,7 +496,7 @@ func callinstr(np **Node, init *Nodes, wr int, skip int) bool {
 			*np = n
 		}
 
-		n = treecopy(n, src.Pos{})
+		n = treecopy(n, src.NoPos)
 		makeaddable(n)
 		var f *Node
 		if flag_msan {

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

@@ -129,7 +129,7 @@ func (f *Func) dumpFile(phaseName string) {
 
 	fi, err := os.Create(fname)
 	if err != nil {
-		f.Config.Warnl(src.Pos{}, "Unable to create after-phase dump file %s", fname)
+		f.Config.Warnl(src.NoPos, "Unable to create after-phase dump file %s", fname)
 		return
 	}
 

src/cmd/compile/internal/ssa/config.go

@@ -270,7 +270,7 @@ func NewConfig(arch string, fe Frontend, ctxt *obj.Link, optimize bool) *Config
 		c.hasGReg = true
 		c.noDuffDevice = true
 	default:
-		fe.Fatalf(src.Pos{}, "arch %s not implemented", arch)
+		fe.Fatalf(src.NoPos, "arch %s not implemented", arch)
 	}
 	c.ctxt = ctxt
 	c.optimize = optimize
@@ -310,7 +310,7 @@ func NewConfig(arch string, fe Frontend, ctxt *obj.Link, optimize bool) *Config
 	if ev != "" {
 		v, err := strconv.ParseInt(ev, 10, 64)
 		if err != nil {
-			fe.Fatalf(src.Pos{}, "Environment variable GO_SSA_PHI_LOC_CUTOFF (value '%s') did not parse as a number", ev)
+			fe.Fatalf(src.NoPos, "Environment variable GO_SSA_PHI_LOC_CUTOFF (value '%s') did not parse as a number", ev)
 		}
 		c.sparsePhiCutoff = uint64(v) // convert -1 to maxint, for never use sparse
 	}
@@ -332,7 +332,7 @@ func (c *Config) Ctxt() *obj.Link         { return c.ctxt }
 func (c *Config) NewFunc() *Func {
 	// TODO(khr): should this function take name, type, etc. as arguments?
 	if c.curFunc != nil {
-		c.Fatalf(src.Pos{}, "NewFunc called without previous Free")
+		c.Fatalf(src.NoPos, "NewFunc called without previous Free")
 	}
 	f := &Func{Config: c, NamedValues: map[LocalSlot][]*Value{}}
 	c.curFunc = f
@@ -355,7 +355,7 @@ func (c *Config) logDebugHashMatch(evname, name string) {
 			var ok error
 			file, ok = os.Create(tmpfile)
 			if ok != nil {
-				c.Fatalf(src.Pos{}, "Could not open hash-testing logfile %s", tmpfile)
+				c.Fatalf(src.NoPos, "Could not open hash-testing logfile %s", tmpfile)
 			}
 		}
 		c.logfiles[evname] = file

src/cmd/compile/internal/ssa/deadstore.go

@@ -113,7 +113,7 @@ func dse(f *Func) {
 				if sz > 0x7fffffff { // work around sparseMap's int32 value type
 					sz = 0x7fffffff
 				}
-				shadowed.set(v.Args[0].ID, int32(sz), src.Pos{})
+				shadowed.set(v.Args[0].ID, int32(sz), src.NoPos)
 			}
 		}
 		// walk to previous store

src/cmd/compile/internal/ssa/func_test.go

@@ -155,7 +155,7 @@ func Fun(c *Config, entry string, blocs ...bloc) fun {
 		blocks[bloc.name] = b
 		for _, valu := range bloc.valus {
 			// args are filled in the second pass.
-			values[valu.name] = b.NewValue0IA(src.Pos{}, valu.op, valu.t, valu.auxint, valu.aux)
+			values[valu.name] = b.NewValue0IA(src.NoPos, valu.op, valu.t, valu.auxint, valu.aux)
 		}
 	}
 	// Connect the blocks together and specify control values.
@@ -429,12 +429,12 @@ func TestConstCache(t *testing.T) {
 		Bloc("entry",
 			Valu("mem", OpInitMem, TypeMem, 0, nil),
 			Exit("mem")))
-	v1 := f.f.ConstBool(src.Pos{}, TypeBool, false)
-	v2 := f.f.ConstBool(src.Pos{}, TypeBool, true)
+	v1 := f.f.ConstBool(src.NoPos, TypeBool, false)
+	v2 := f.f.ConstBool(src.NoPos, TypeBool, true)
 	f.f.freeValue(v1)
 	f.f.freeValue(v2)
-	v3 := f.f.ConstBool(src.Pos{}, TypeBool, false)
-	v4 := f.f.ConstBool(src.Pos{}, TypeBool, true)
+	v3 := f.f.ConstBool(src.NoPos, TypeBool, false)
+	v4 := f.f.ConstBool(src.NoPos, TypeBool, true)
 	if v3.AuxInt != 0 {
 		t.Errorf("expected %s to have auxint of 0\n", v3.LongString())
 	}

src/cmd/compile/internal/ssa/html.go

@@ -21,7 +21,7 @@ type HTMLWriter struct {
 func NewHTMLWriter(path string, logger Logger, funcname string) *HTMLWriter {
 	out, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
 	if err != nil {
-		logger.Fatalf(src.Pos{}, "%v", err)
+		logger.Fatalf(src.NoPos, "%v", err)
 	}
 	html := HTMLWriter{File: out, Logger: logger}
 	html.start(funcname)
@@ -329,13 +329,13 @@ func (w *HTMLWriter) WriteColumn(title string, html string) {
 
 func (w *HTMLWriter) Printf(msg string, v ...interface{}) {
 	if _, err := fmt.Fprintf(w.File, msg, v...); err != nil {
-		w.Fatalf(src.Pos{}, "%v", err)
+		w.Fatalf(src.NoPos, "%v", err)
 	}
 }
 
 func (w *HTMLWriter) WriteString(s string) {
 	if _, err := w.File.WriteString(s); err != nil {
-		w.Fatalf(src.Pos{}, "%v", err)
+		w.Fatalf(src.NoPos, "%v", err)
 	}
 }
 

src/cmd/compile/internal/ssa/regalloc.go

@@ -555,7 +555,7 @@ func (s *regAllocState) init(f *Func) {
 		case "s390x":
 			// nothing to do, R10 & R11 already reserved
 		default:
-			s.f.Config.fe.Fatalf(src.Pos{}, "arch %s not implemented", s.f.Config.arch)
+			s.f.Config.fe.Fatalf(src.NoPos, "arch %s not implemented", s.f.Config.arch)
 		}
 	}
 	if s.f.Config.nacl {
@@ -1912,13 +1912,13 @@ func (e *edgeState) setup(idx int, srcReg []endReg, dstReg []startReg, stacklive
 
 	// Live registers can be sources.
 	for _, x := range srcReg {
-		e.set(&e.s.registers[x.r], x.v.ID, x.c, false, src.Pos{}) // don't care the position of the source
+		e.set(&e.s.registers[x.r], x.v.ID, x.c, false, src.NoPos) // don't care the position of the source
 	}
 	// So can all of the spill locations.
 	for _, spillID := range stacklive {
 		v := e.s.orig[spillID]
 		spill := e.s.values[v.ID].spill
-		e.set(e.s.f.getHome(spillID), v.ID, spill, false, src.Pos{}) // don't care the position of the source
+		e.set(e.s.f.getHome(spillID), v.ID, spill, false, src.NoPos) // don't care the position of the source
 	}
 
 	// Figure out all the destinations we need.

src/cmd/compile/internal/ssa/sparsemap.go

@@ -66,7 +66,7 @@ func (s *sparseMap) setBit(k ID, v uint) {
 		s.dense[i].val |= 1 << v
 		return
 	}
-	s.dense = append(s.dense, sparseEntry{k, 1 << v, src.Pos{}})
+	s.dense = append(s.dense, sparseEntry{k, 1 << v, src.NoPos})
 	s.sparse[k] = int32(len(s.dense)) - 1
 }
 

src/cmd/compile/internal/ssa/stackalloc.go

@@ -40,7 +40,7 @@ func newStackAllocState(f *Func) *stackAllocState {
 		return new(stackAllocState)
 	}
 	if s.f != nil {
-		f.Config.Fatalf(src.Pos{}, "newStackAllocState called without previous free")
+		f.Config.Fatalf(src.NoPos, "newStackAllocState called without previous free")
 	}
 	return s
 }

src/cmd/internal/src/src.go

@@ -18,6 +18,9 @@ type Pos struct {
 	line int32
 }
 
+// NoPos is a valid unknown position.
+var NoPos Pos
+
 // MakePos creates a new Pos from a line index.
 // It requires intimate knowledge of the underlying
 // implementation and should be used with caution.