add Symbol type to operand

operand/types.go

@@ -10,7 +10,21 @@ type Op interface {
 	Asm() string
 }
 
+type Symbol struct {
+	Name   string
+	Static bool
+}
+
+func (s Symbol) String() string {
+	n := s.Name
+	if s.Static {
+		n += "<>"
+	}
+	return n
+}
+
 type Mem struct {
+	Symbol Symbol
 	Disp   int
 	Base   reg.Register
 	Index  reg.Register
@@ -18,9 +32,13 @@ type Mem struct {
 }
 
 func (m Mem) Asm() string {
-	a := ""
+	a := m.Symbol.String()
 	if m.Disp != 0 {
+		if a == "" {
 			a += fmt.Sprintf("%d", m.Disp)
+		} else {
+			a += fmt.Sprintf("%+d", m.Disp)
+		}
 	}
 	if m.Base != nil {
 		a += fmt.Sprintf("(%s)", m.Base.Asm())

operand/types_test.go

@@ -7,6 +7,23 @@ import (
 	"github.com/mmcloughlin/avo/reg"
 )
 
+func TestSymbolString(t *testing.T) {
+	cases := []struct {
+		Symbol Symbol
+		Expect string
+	}{
+		{Symbol{}, ""},
+		{Symbol{Name: "name"}, "name"},
+		{Symbol{Name: "static", Static: true}, "static<>"},
+	}
+	for _, c := range cases {
+		got := c.Symbol.String()
+		if got != c.Expect {
+			t.Errorf("%#v.String() = %s expected %s", c.Symbol, got, c.Expect)
+		}
+	}
+}
+
 func TestMemAsm(t *testing.T) {
 	cases := []struct {
 		Mem    Mem
@@ -14,11 +31,16 @@ func TestMemAsm(t *testing.T) {
 	}{
 		{Mem{Base: reg.EAX}, "(AX)"},
 		{Mem{Disp: 16, Base: reg.RAX}, "16(AX)"},
+		{Mem{Disp: -7, Base: reg.RAX}, "-7(AX)"},
 		{Mem{Base: reg.R11, Index: reg.RAX, Scale: 4}, "(R11)(AX*4)"},
 		{Mem{Base: reg.R11, Index: reg.RAX, Scale: 1}, "(R11)(AX*1)"},
 		{Mem{Base: reg.R11, Index: reg.RAX}, "(R11)"},
 		{Mem{Base: reg.R11, Scale: 8}, "(R11)"},
 		{Mem{Disp: 2048, Base: reg.R11, Index: reg.RAX, Scale: 8}, "2048(R11)(AX*8)"},
+		{Mem{Symbol: Symbol{Name: "foo"}, Base: reg.StaticBase}, "foo(SB)"},
+		{Mem{Symbol: Symbol{Name: "foo"}, Base: reg.StaticBase, Disp: 4}, "foo+4(SB)"},
+		{Mem{Symbol: Symbol{Name: "foo"}, Base: reg.StaticBase, Disp: -7}, "foo-7(SB)"},
+		{Mem{Symbol: Symbol{Name: "bar", Static: true}, Base: reg.StaticBase, Disp: 4, Index: reg.R11, Scale: 4}, "bar<>+4(SB)(R11*4)"},
 	}
 	for _, c := range cases {
 		got := c.Mem.Asm()

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}