Improved x64 encoder

src/build/arch/x64/Store.go

@@ -0,0 +1,52 @@
+package x64
+
+import (
+	"encoding/binary"
+
+	"git.akyoto.dev/cli/q/src/build/cpu"
+)
+
+// StoreNumber stores a number into the memory address included in the given register.
+func StoreNumber(code []byte, register cpu.Register, offset byte, byteCount byte, number int) []byte {
+	if byteCount == 2 {
+		code = append(code, 0x66)
+	}
+
+	opCode := byte(0xC7)
+
+	if byteCount == 1 {
+		opCode = 0xC6
+	}
+
+	mod := AddressMemory
+
+	if offset != 0 || register == RBP || register == R13 {
+		mod = AddressMemoryOffset8
+	}
+
+	is64Bit := byte(0)
+
+	if byteCount == 8 {
+		is64Bit = 1
+	}
+
+	code = encode(code, is64Bit, mod, 0b000, byte(register), opCode)
+
+	if register == RSP || register == R12 {
+		code = append(code, SIB(0b00, 0b100, 0b100))
+	}
+
+	if mod == AddressMemoryOffset8 {
+		code = append(code, offset)
+	}
+
+	switch byteCount {
+	case 8, 4:
+		return binary.LittleEndian.AppendUint32(code, uint32(number))
+
+	case 2:
+		return binary.LittleEndian.AppendUint16(code, uint16(number))
+	}
+
+	return append(code, byte(number))
+}