Implemented register calls

src/x86/Call.go

@@ -1,5 +1,7 @@
 package x86
 
+import "git.urbach.dev/cli/q/src/cpu"
+
 // Call places the return address on the top of the stack and continues
 // program flow at the new address.
 // The address is relative to the next instruction.
@@ -14,8 +16,25 @@ func Call(code []byte, address uint32) []byte {
 	)
 }
 
-// CallAtAddress places the return address on the top of the stack and
-// continues program flow at the address stored at the given memory address.
+// Calls a function whose address is stored in the given register.
+func CallRegister(code []byte, register cpu.Register) []byte {
+	if register > 0b111 {
+		return append(
+			code,
+			0x41,
+			0xFF,
+			0xD0+byte(register&0b111),
+		)
+	}
+
+	return append(
+		code,
+		0xFF,
+		0xD0+byte(register),
+	)
+}
+
+// CallAtAddress calls a function at the address stored at the given memory address.
 // The memory address is relative to the next instruction.
 func CallAtAddress(code []byte, address uint32) []byte {
 	return append(

src/x86/Call_test.go

@@ -0,0 +1,39 @@
+package x86_test
+
+import (
+	"testing"
+
+	"git.urbach.dev/cli/q/src/cpu"
+	"git.urbach.dev/cli/q/src/x86"
+	"git.urbach.dev/go/assert"
+)
+
+func TestCallRegister(t *testing.T) {
+	usagePatterns := []struct {
+		Register cpu.Register
+		Code     []byte
+	}{
+		{x86.RAX, []byte{0xFF, 0xD0}},
+		{x86.RCX, []byte{0xFF, 0xD1}},
+		{x86.RDX, []byte{0xFF, 0xD2}},
+		{x86.RBX, []byte{0xFF, 0xD3}},
+		{x86.RSP, []byte{0xFF, 0xD4}},
+		{x86.RBP, []byte{0xFF, 0xD5}},
+		{x86.RSI, []byte{0xFF, 0xD6}},
+		{x86.RDI, []byte{0xFF, 0xD7}},
+		{x86.R8, []byte{0x41, 0xFF, 0xD0}},
+		{x86.R9, []byte{0x41, 0xFF, 0xD1}},
+		{x86.R10, []byte{0x41, 0xFF, 0xD2}},
+		{x86.R11, []byte{0x41, 0xFF, 0xD3}},
+		{x86.R12, []byte{0x41, 0xFF, 0xD4}},
+		{x86.R13, []byte{0x41, 0xFF, 0xD5}},
+		{x86.R14, []byte{0x41, 0xFF, 0xD6}},
+		{x86.R15, []byte{0x41, 0xFF, 0xD7}},
+	}
+
+	for _, pattern := range usagePatterns {
+		t.Logf("call %s", pattern.Register)
+		code := x86.CallRegister(nil, pattern.Register)
+		assert.DeepEqual(t, code, pattern.Code)
+	}
+}