[dev.ssa] cmd/compile/ssa: improve comments, logging, and debug output

Change-Id: Id949db82ddaf802c1aa245a337081d4d46fd914f
Reviewed-on: https://go-review.googlesource.com/11380Reviewed-by: Alan Donovan <adonovan@google.com>

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

@@ -15,6 +15,7 @@ func cse(f *Func) {
 	//   v.op == w.op
 	//   v.type == w.type
 	//   v.aux == w.aux
+	//   v.auxint == w.auxint
 	//   len(v.args) == len(w.args)
 	//   equivalent(v.args[i], w.args[i]) for i in 0..len(v.args)-1
 
@@ -23,7 +24,7 @@ func cse(f *Func) {
 	// It starts with a coarse partition and iteratively refines it
 	// until it reaches a fixed point.
 
-	// Make initial partition based on opcode/type/aux/nargs
+	// Make initial partition based on opcode/type/aux/auxint/nargs
 	// TODO(khr): types are not canonical, so we split unnecessarily.
 	// For example, all pointer types are distinct. Fix this.
 	// As a data point, using v.Type.String() instead of

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

@@ -59,8 +59,12 @@ func (v *Value) LongString() string {
 		s += fmt.Sprintf(" [%d]", v.AuxInt)
 	}
 	if v.Aux != nil {
+		if _, ok := v.Aux.(string); ok {
+			s += fmt.Sprintf(" {%q}", v.Aux)
+		} else {
 			s += fmt.Sprintf(" {%v}", v.Aux)
 		}
+	}
 	for _, a := range v.Args {
 		s += fmt.Sprintf(" %v", a)
 	}