Implemented division

src/build/arch/x64/Div.go

@@ -0,0 +1,20 @@
+package x64
+
+import "git.akyoto.dev/cli/q/src/build/cpu"
+
+// DivReg divides RDX:RAX by the value in the register.
+func DivReg(code []byte, divisor cpu.Register) []byte {
+	rex := byte(0x48)
+
+	if divisor >= 8 {
+		rex++
+		divisor -= 8
+	}
+
+	return append(
+		code,
+		rex,
+		0xF7,
+		0xF8+byte(divisor),
+	)
+}

src/build/arch/x64/Div_test.go

@@ -0,0 +1,39 @@
+package x64_test
+
+import (
+	"testing"
+
+	"git.akyoto.dev/cli/q/src/build/arch/x64"
+	"git.akyoto.dev/cli/q/src/build/cpu"
+	"git.akyoto.dev/go/assert"
+)
+
+func TestDivRegister(t *testing.T) {
+	usagePatterns := []struct {
+		Register cpu.Register
+		Code     []byte
+	}{
+		{x64.RAX, []byte{0x48, 0xF7, 0xF8}},
+		{x64.RCX, []byte{0x48, 0xF7, 0xF9}},
+		{x64.RDX, []byte{0x48, 0xF7, 0xFA}},
+		{x64.RBX, []byte{0x48, 0xF7, 0xFB}},
+		{x64.RSP, []byte{0x48, 0xF7, 0xFC}},
+		{x64.RBP, []byte{0x48, 0xF7, 0xFD}},
+		{x64.RSI, []byte{0x48, 0xF7, 0xFE}},
+		{x64.RDI, []byte{0x48, 0xF7, 0xFF}},
+		{x64.R8, []byte{0x49, 0xF7, 0xF8}},
+		{x64.R9, []byte{0x49, 0xF7, 0xF9}},
+		{x64.R10, []byte{0x49, 0xF7, 0xFA}},
+		{x64.R11, []byte{0x49, 0xF7, 0xFB}},
+		{x64.R12, []byte{0x49, 0xF7, 0xFC}},
+		{x64.R13, []byte{0x49, 0xF7, 0xFD}},
+		{x64.R14, []byte{0x49, 0xF7, 0xFE}},
+		{x64.R15, []byte{0x49, 0xF7, 0xFF}},
+	}
+
+	for _, pattern := range usagePatterns {
+		t.Logf("idiv %s", pattern.Register)
+		code := x64.DivReg(nil, pattern.Register)
+		assert.DeepEqual(t, code, pattern.Code)
+	}
+}

src/build/arch/x64/ExtendRAXToRDX.go

@@ -0,0 +1,7 @@
+package x64
+
+// ExtendRAXToRDX doubles the size of RAX by sign-extending it to RDX.
+// This is also known as CQO.
+func ExtendRAXToRDX(code []byte) []byte {
+	return append(code, 0x48, 0x99)
+}