Add DECY instruction.

aleury · Jan 15, 2024 · 0c372d8 · 0c372d8
1 parent 7d14568
commit 0c372d8
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Showing 5 changed files with 21 additions and 1 deletion.
diff --git a/gmachine.go b/gmachine.go
@@ -26,6 +26,7 @@ const (
 	OpINCA
 	OpDECA
 	OpDECX
+	OpDECY
 	OpADDA
 	OpMULA
 	OpMOVA
@@ -68,6 +69,7 @@ var opcodes = map[string]Word{
 	"INCA": OpINCA,
 	"DECA": OpDECA,
 	"DECX": OpDECX,
+	"DECY": OpDECY,
 	"ADDA": OpADDA,
 	"MULA": OpMULA,
 	"MOVA": OpMOVA,
@@ -134,6 +136,8 @@ func (g *Machine) Run() {
 			g.A--
 		case OpDECX:
 			g.X--
+		case OpDECY:
+			g.Y--
 		case OpADDA:
 			switch g.Next() {
 			case RegX:

diff --git a/gmachine_test.go b/gmachine_test.go
@@ -157,6 +157,20 @@ func TestDECX(t *testing.T) {
 	}
 }
 
+func TestDECY(t *testing.T) {
+	t.Parallel()
+	g := gmachine.New(nil)
+	g.Y = 1
+	var wantY gmachine.Word = 0
+	err := assembleAndRunFromString(g, "DECY")
+	if err != nil {
+		t.Fatal("didn't expect an error", err)
+	}
+	if wantY != g.Y {
+		t.Errorf("want Y value %d, got %d", wantY, g.Y)
+	}
+}
+
 func TestSETA(t *testing.T) {
 	t.Parallel()
 	g := gmachine.New(nil)

diff --git a/testdata/gc.txtar b/testdata/gc.txtar
@@ -9,6 +9,6 @@ SETA 42
 OUTA
 
 -- want --
-0000000 0000 0000 0000 0a00 0000 0000 0000 2a00
+0000000 0000 0000 0000 0b00 0000 0000 0000 2a00
 0000010 0000 0000 0000 0300                    
 0000018
diff --git a/token/token.go b/token/token.go
@@ -25,6 +25,7 @@ var opcodes = map[string]TokenType{
 	"INCA": OPCODE,
 	"DECA": OPCODE,
 	"DECX": OPCODE,
+	"DECY": OPCODE,
 	"ADDA": OPCODE,
 	"MULA": OPCODE,
 	"MOVA": OPCODE,

diff --git a/token/token_test.go b/token/token_test.go
@@ -17,6 +17,7 @@ func TestLookupIdent(t *testing.T) {
 		{"INCA", token.OPCODE},
 		{"DECA", token.OPCODE},
 		{"DECX", token.OPCODE},
+		{"DECY", token.OPCODE},
 		{"ADDA", token.OPCODE},
 		{"MULA", token.OPCODE},
 		{"MOVA", token.OPCODE},