cmd/compile: make node.hasVal into two bools

In addition to being more compact,
this makes the code a lot clearer.

Change-Id: Ibcb70526c2e5913dcf34904fda194e3585228c3f
Reviewed-on: https://go-review.googlesource.com/41761
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -62,7 +62,6 @@ type Node struct {
 	Walkdef   uint8       // tracks state during typecheckdef; 2 == loop detected
 	Typecheck uint8       // tracks state during typechecking; 2 == loop detected
 	Initorder uint8
-	hasVal    int8 // +1 for Val, -1 for Opt, 0 for not yet set
 }
 
 // IsAutoTmp indicates if n was created by the compiler as a temporary,
@@ -93,6 +92,8 @@ const (
 	nodeUsed     // for variable/label declared and not used error
 	nodeHasCall  // expression contains a function call
 	nodeLikely   // if statement condition likely
+	nodeHasVal   // node.E contains a Val
+	nodeHasOpt   // node.E contains an Opt
 )
 
 func (n *Node) HasBreak() bool              { return n.flags&nodeHasBreak != 0 }
@@ -113,6 +114,8 @@ func (n *Node) Addable() bool               { return n.flags&nodeAddable != 0 }
 func (n *Node) Used() bool                  { return n.flags&nodeUsed != 0 }
 func (n *Node) HasCall() bool               { return n.flags&nodeHasCall != 0 }
 func (n *Node) Likely() bool                { return n.flags&nodeLikely != 0 }
+func (n *Node) HasVal() bool                { return n.flags&nodeHasVal != 0 }
+func (n *Node) HasOpt() bool                { return n.flags&nodeHasOpt != 0 }
 
 func (n *Node) SetHasBreak(b bool)              { n.flags.set(nodeHasBreak, b) }
 func (n *Node) SetIsClosureVar(b bool)          { n.flags.set(nodeIsClosureVar, b) }
@@ -132,10 +135,12 @@ func (n *Node) SetAddable(b bool)               { n.flags.set(nodeAddable, b) }
 func (n *Node) SetUsed(b bool)                  { n.flags.set(nodeUsed, b) }
 func (n *Node) SetHasCall(b bool)               { n.flags.set(nodeHasCall, b) }
 func (n *Node) SetLikely(b bool)                { n.flags.set(nodeLikely, b) }
+func (n *Node) SetHasVal(b bool)                { n.flags.set(nodeHasVal, b) }
+func (n *Node) SetHasOpt(b bool)                { n.flags.set(nodeHasOpt, b) }
 
 // Val returns the Val for the node.
 func (n *Node) Val() Val {
-	if n.hasVal != +1 {
+	if !n.HasVal() {
 		return Val{}
 	}
 	return Val{n.E}
@@ -143,18 +148,18 @@ func (n *Node) Val() Val {
 
 // SetVal sets the Val for the node, which must not have been used with SetOpt.
 func (n *Node) SetVal(v Val) {
-	if n.hasVal == -1 {
+	if n.HasOpt() {
 		Debug['h'] = 1
 		Dump("have Opt", n)
 		Fatalf("have Opt")
 	}
-	n.hasVal = +1
+	n.SetHasVal(true)
 	n.E = v.U
 }
 
 // Opt returns the optimizer data for the node.
 func (n *Node) Opt() interface{} {
-	if n.hasVal != -1 {
+	if !n.HasOpt() {
 		return nil
 	}
 	return n.E
@@ -163,15 +168,15 @@ func (n *Node) Opt() interface{} {
 // SetOpt sets the optimizer data for the node, which must not have been used with SetVal.
 // SetOpt(nil) is ignored for Vals to simplify call sites that are clearing Opts.
 func (n *Node) SetOpt(x interface{}) {
-	if x == nil && n.hasVal >= 0 {
+	if x == nil && n.HasVal() {
 		return
 	}
-	if n.hasVal == +1 {
+	if n.HasVal() {
 		Debug['h'] = 1
 		Dump("have Val", n)
 		Fatalf("have Val")
 	}
-	n.hasVal = -1
+	n.SetHasOpt(true)
 	n.E = x
 }