add Symbol type to operand

reg/reg_test.go

@@ -7,6 +7,7 @@ func TestSpecBytes(t *testing.T) {
 		Spec  Spec
 		Bytes uint
 	}{
+		{S0, 0},
 		{S8L, 1},
 		{S8H, 1},
 		{S16, 2},

reg/types.go

@@ -140,6 +140,7 @@ func (r register) register()       {}
 type Spec uint16
 
 const (
+	S0   Spec = 0x0 // zero value reserved for pseudo registers
 	S8L  Spec = 0x1
 	S8H  Spec = 0x2
 	S8        = S8L

reg/x86.go

@@ -2,13 +2,15 @@ package reg
 
 // Register families.
 const (
-	GP Kind = iota
+	Internal Kind = iota
+	GP
 	MMX
 	SSEAVX
 	Mask
 )
 
 var Families = []*Family{
+	Pseudo,
 	GeneralPurpose,
 	SIMD,
 }
@@ -25,6 +27,16 @@ func FamilyOfKind(k Kind) *Family {
 	return familiesByKind[k]
 }
 
+// Pseudo registers.
+var (
+	Pseudo = &Family{Kind: Internal}
+
+	FramePointer   = Pseudo.define(S0, 0, "FP")
+	ProgramCounter = Pseudo.define(S0, 0, "PC")
+	StaticBase     = Pseudo.define(S0, 0, "SB")
+	StackPointer   = Pseudo.define(S0, 0, "SP")
+)
+
 // General purpose registers.
 var (
 	GeneralPurpose = &Family{Kind: GP}