cmd/compile: more String methods for prove types

These aid in debugging.

Change-Id: Ieb38c996765f780f6103f8c3292639d408c25123
Reviewed-on: https://go-review.googlesource.com/87476
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/fmt_test.go

@@ -707,6 +707,7 @@ var knownFormats = map[string]string{
 	"uint %04x":        "",
 	"uint %5d":         "",
 	"uint %d":          "",
+	"uint %x":          "",
 	"uint16 %d":        "",
 	"uint16 %v":        "",
 	"uint16 %x":        "",

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

@@ -45,6 +45,18 @@ const (
 	gt
 )
 
+var relationStrings = [...]string{
+	0: "none", lt: "<", eq: "==", lt | eq: "<=",
+	gt: ">", gt | lt: "!=", gt | eq: ">=", gt | eq | lt: "any",
+}
+
+func (r relation) String() string {
+	if r < relation(len(relationStrings)) {
+		return relationStrings[r]
+	}
+	return fmt.Sprintf("relation(%d)", uint(r))
+}
+
 // domain represents the domain of a variable pair in which a set
 // of relations is known.  For example, relations learned for unsigned
 // pairs cannot be transferred to signed pairs because the same bit
@@ -58,6 +70,30 @@ const (
 	boolean
 )
 
+var domainStrings = [...]string{
+	"signed", "unsigned", "pointer", "boolean",
+}
+
+func (d domain) String() string {
+	s := ""
+	for i, ds := range domainStrings {
+		if d&(1<<uint(i)) != 0 {
+			if len(s) != 0 {
+				s += "|"
+			}
+			s += ds
+			d &^= 1 << uint(i)
+		}
+	}
+	if d != 0 {
+		if len(s) != 0 {
+			s += "|"
+		}
+		s += fmt.Sprintf("0x%x", uint(d))
+	}
+	return s
+}
+
 type pair struct {
 	v, w *Value // a pair of values, ordered by ID.
 	// v can be nil, to mean the zero value.