Improved x64 encoder

src/build/arch/x64/numberToRegister.go

@@ -1,24 +1,27 @@
 package x64
 
-import (
-	"math"
+// numRegReg encodes an instruction with up to two registers and a number parameter.
+func numRegReg(code []byte, opCode8 byte, opCode32 byte, reg byte, rm byte, number int) []byte {
+	w := byte(1)      // Indicates a 64-bit register.
+	r := byte(0)      // Extension to the "reg" field in ModRM.
+	x := byte(0)      // Extension to the SIB index field.
+	b := byte(0)      // Extension to the "rm" field in ModRM or the SIB base (r8 up to r15 use this).
+	mod := byte(0b11) // Direct addressing mode, no register offsets.
 
-	"git.akyoto.dev/cli/q/src/build/cpu"
-)
-
-// numberToRegister encodes an instruction with a register and a number parameter.
-func numberToRegister(opCode8 byte, opCode32 byte, reg byte, code []byte, destination cpu.Register, number int) []byte {
-	b := byte(0)
-
-	if destination >= 8 {
-		b = 1
-		destination -= 8
+	if reg > 0b111 {
+		r = 1
+		reg &= 0b111
 	}
 
-	rex := REX(1, 0, 0, b)
-	modRM := ModRM(0b11, reg, byte(destination))
+	if rm > 0b111 {
+		b = 1
+		rm &= 0b111
+	}
 
-	if number >= math.MinInt8 && number <= math.MaxInt8 {
+	rex := REX(w, r, x, b)
+	modRM := ModRM(mod, reg, rm)
+
+	if sizeOf(number) == 1 {
 		return append(
 			code,
 			rex,