cmd/compile/internal/gc: better names for (b|c|f)conf (cleanup)

Use String and GoString methods instead of the xconf names
for the numeric conversion routines.

Also, fixed a couple of comments in fmt.go.

Change-Id: I1b8acdd95dbff3fc30273070fbb1ac4860031a3c
Reviewed-on: https://go-review.googlesource.com/136197Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -476,7 +476,7 @@ func toflt(v Val) Val {
 		f := newMpflt()
 		f.Set(&u.Real)
 		if u.Imag.CmpFloat64(0) != 0 {
-			yyerror("constant %v truncated to real", cconv(u))
+			yyerror("constant %v truncated to real", u.GoString())
 		}
 		v.U = f
 	}
@@ -509,11 +509,11 @@ func toint(v Val) Val {
 				// value from the error message.
 				// (See issue #11371).
 				var t big.Float
-				t.Parse(fconv(u), 10)
+				t.Parse(u.GoString(), 10)
 				if t.IsInt() {
 					yyerror("constant truncated to integer")
 				} else {
-					yyerror("constant %v truncated to integer", fconv(u))
+					yyerror("constant %v truncated to integer", u.GoString())
 				}
 			}
 		}
@@ -522,7 +522,7 @@ func toint(v Val) Val {
 	case *Mpcplx:
 		i := new(Mpint)
 		if !i.SetFloat(&u.Real) || u.Imag.CmpFloat64(0) != 0 {
-			yyerror("constant %v truncated to integer", cconv(u))
+			yyerror("constant %v truncated to integer", u.GoString())
 		}
 
 		v.U = i

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

@@ -119,7 +119,7 @@ const (
 // *types.Type:
 //   %#v    Go format
 //   %#L    type definition instead of name
-//   %#S    omit"func" and receiver in function signature
+//   %#S    omit "func" and receiver in function signature
 //
 //   %-v    type identifiers
 //   %-S    type identifiers without "func" and arg names in type signatures (methodsym)
@@ -514,10 +514,10 @@ func (v Val) vconv(s fmt.State, flag FmtFlag) {
 	case *Mpint:
 		if !u.Rune {
 			if flag&FmtSharp != 0 {
-				fmt.Fprint(s, bconv(u))
+				fmt.Fprint(s, u.String())
 				return
 			}
-			fmt.Fprint(s, u.String())
+			fmt.Fprint(s, u.GoString())
 			return
 		}
 
@@ -540,23 +540,16 @@ func (v Val) vconv(s fmt.State, flag FmtFlag) {
 			fmt.Fprint(s, u.String())
 			return
 		}
-		fmt.Fprint(s, fconv(u))
+		fmt.Fprint(s, u.GoString())
 		return
 
 	case *Mpcplx:
-		switch {
-		case flag&FmtSharp != 0:
-			fmt.Fprintf(s, "(%v+%vi)", &u.Real, &u.Imag)
-
-		case v.U.(*Mpcplx).Real.CmpFloat64(0) == 0:
-			fmt.Fprintf(s, "%vi", fconv(&u.Imag))
-
-		case v.U.(*Mpcplx).Imag.CmpFloat64(0) == 0:
-			fmt.Fprint(s, fconv(&u.Real))
-
-		default:
-			fmt.Fprintf(s, "(%v)", cconv(u))
+		if flag&FmtSharp != 0 {
+			fmt.Fprint(s, u.String())
+			return
 		}
+		fmt.Fprint(s, u.GoString())
+		return
 
 	case string:
 		fmt.Fprint(s, strconv.Quote(u))
@@ -668,7 +661,7 @@ func typefmt(t *types.Type, flag FmtFlag, mode fmtMode, depth int) string {
 		return "error"
 	}
 
-	// Unless the 'l' flag was specified, if the type has a name, just print that name.
+	// Unless the 'L' flag was specified, if the type has a name, just print that name.
 	if flag&FmtLong == 0 && t.Sym != nil && t != types.Types[t.Etype] {
 		switch mode {
 		case FTypeId, FTypeIdName:
@@ -1529,9 +1522,8 @@ func (n *Node) exprfmt(s fmt.State, prec int, mode fmtMode) {
 func (n *Node) nodefmt(s fmt.State, flag FmtFlag, mode fmtMode) {
 	t := n.Type
 
-	// We almost always want the original, except in export mode for literals.
-	// This saves the importer some work, and avoids us having to redo some
-	// special casing for package unsafe.
+	// We almost always want the original.
+	// TODO(gri) Why the special case for OLITERAL?
 	if n.Op != OLITERAL && n.Orig != nil {
 		n = n.Orig
 	}

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

@@ -204,7 +204,7 @@ func (f *Mpflt) String() string {
 	return f.Val.Text('b', 0)
 }
 
-func fconv(fvp *Mpflt) string {
+func (fvp *Mpflt) GoString() string {
 	// determine sign
 	sign := ""
 	f := &fvp.Val
@@ -327,11 +327,33 @@ func (v *Mpcplx) Div(rv *Mpcplx) bool {
 	return true
 }
 
-func cconv(v *Mpcplx) string {
-	re := fconv(&v.Real)
-	im := fconv(&v.Imag)
-	if im[0] == '-' {
-		return re + im + "i"
+func (v *Mpcplx) String() string {
+	return fmt.Sprintf("(%s+%si)", v.Real.String(), v.Imag.String())
+}
+
+func (v *Mpcplx) GoString() string {
+	var re string
+	sre := v.Real.CmpFloat64(0)
+	if sre != 0 {
+		re = v.Real.GoString()
+	}
+
+	var im string
+	sim := v.Imag.CmpFloat64(0)
+	if sim != 0 {
+		im = v.Imag.GoString()
+	}
+
+	switch {
+	case sre == 0 && sim == 0:
+		return "0"
+	case sre == 0:
+		return im + "i"
+	case sim == 0:
+		return re
+	case sim < 0:
+		return fmt.Sprintf("(%s%si)", re, im)
+	default:
+		return fmt.Sprintf("(%s+%si)", re, im)
 	}
-	return re + "+" + im + "i"
 }

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

@@ -299,10 +299,10 @@ func (a *Mpint) SetString(as string) {
 	}
 }
 
-func (a *Mpint) String() string {
+func (a *Mpint) GoString() string {
 	return a.Val.String()
 }
 
-func bconv(a *Mpint) string {
+func (a *Mpint) String() string {
 	return fmt.Sprintf("%#x", &a.Val)
 }