Simplified memory access encoding

src/x64/StoreDynamic.go

@@ -8,55 +8,7 @@ import (
 
 // StoreDynamicNumber stores a number into the memory address at `destination` with a register offset.
 func StoreDynamicNumber(code []byte, destination cpu.Register, offset cpu.Register, length byte, number int) []byte {
-	var (
-		w      = byte(0)
-		r      = byte(0)
-		x      = byte(0)
-		b      = byte(0)
-		opCode = byte(0xC7)
-		mod    = AddressMemory
-	)
-
-	if length == 1 {
-		opCode = 0xC6
-	}
-
-	if offset == RSP {
-		tmp := offset
-		offset = destination
-		destination = tmp
-	}
-
-	if length == 8 {
-		w = 1
-	}
-
-	if offset > 0b111 {
-		x = 1
-		offset &= 0b111
-	}
-
-	if destination > 0b111 {
-		b = 1
-		destination &= 0b111
-	}
-
-	if destination == RBP || destination == R13 {
-		mod = AddressMemoryOffset8
-	}
-
-	if length == 2 {
-		code = append(code, 0x66)
-	}
-
-	code = append(code, REX(w, r, x, b))
-	code = append(code, opCode)
-	code = append(code, ModRM(mod, 0b000, 0b100))
-	code = append(code, SIB(Scale1, byte(offset), byte(destination)))
-
-	if mod == AddressMemoryOffset8 {
-		code = append(code, 0x00)
-	}
+	code = memoryAccessDynamic(code, 0xC6, 0xC7, destination, offset, length, 0b000)
 
 	switch length {
 	case 8, 4:
@@ -71,60 +23,5 @@ func StoreDynamicNumber(code []byte, destination cpu.Register, offset cpu.Regist
 
 // StoreDynamicRegister stores the contents of the `source` register into the memory address at `destination` with a register offset.
 func StoreDynamicRegister(code []byte, destination cpu.Register, offset cpu.Register, length byte, source cpu.Register) []byte {
-	var (
-		w      = byte(0)
-		r      = byte(0)
-		x      = byte(0)
-		b      = byte(0)
-		opCode = byte(0x89)
-		mod    = AddressMemory
-	)
-
-	if length == 1 {
-		opCode = 0x88
-	}
-
-	if offset == RSP {
-		tmp := offset
-		offset = destination
-		destination = tmp
-	}
-
-	if length == 8 {
-		w = 1
-	}
-
-	if source > 0b111 {
-		r = 1
-		source &= 0b111
-	}
-
-	if offset > 0b111 {
-		x = 1
-		offset &= 0b111
-	}
-
-	if destination > 0b111 {
-		b = 1
-		destination &= 0b111
-	}
-
-	if destination == RBP || destination == R13 {
-		mod = AddressMemoryOffset8
-	}
-
-	if length == 2 {
-		code = append(code, 0x66)
-	}
-
-	code = append(code, REX(w, r, x, b))
-	code = append(code, opCode)
-	code = append(code, ModRM(mod, byte(source), 0b100))
-	code = append(code, SIB(Scale1, byte(offset), byte(destination)))
-
-	if mod == AddressMemoryOffset8 {
-		code = append(code, 0x00)
-	}
-
-	return code
+	return memoryAccessDynamic(code, 0x88, 0x89, destination, offset, length, source)
 }

src/x64/memoryAccess.go

@@ -4,10 +4,6 @@ import "git.akyoto.dev/cli/q/src/cpu"
 
 // memoryAccess encodes a memory access.
 func memoryAccess(code []byte, opCode8 byte, opCode32 byte, register cpu.Register, offset byte, numBytes byte, source cpu.Register) []byte {
-	if numBytes == 2 {
-		code = append(code, 0x66)
-	}
-
 	opCode := opCode32
 
 	if numBytes == 1 {
@@ -20,6 +16,10 @@ func memoryAccess(code []byte, opCode8 byte, opCode32 byte, register cpu.Registe
 		mod = AddressMemoryOffset8
 	}
 
+	if numBytes == 2 {
+		code = append(code, 0x66)
+	}
+
 	code = encode(code, mod, source, register, numBytes, opCode)
 
 	if register == RSP || register == R12 {

src/x64/memoryAccessDynamic.go

@@ -0,0 +1,63 @@
+package x64
+
+import "git.akyoto.dev/cli/q/src/cpu"
+
+// memoryAccessDynamic encodes a memory access using the value of a register as an offset.
+func memoryAccessDynamic(code []byte, opCode8 byte, opCode32 byte, destination cpu.Register, offset cpu.Register, numBytes byte, source cpu.Register) []byte {
+	var (
+		w      = byte(0)
+		r      = byte(0)
+		x      = byte(0)
+		b      = byte(0)
+		opCode = opCode32
+		mod    = AddressMemory
+	)
+
+	if numBytes == 1 {
+		opCode = opCode8
+	}
+
+	if offset == RSP {
+		tmp := offset
+		offset = destination
+		destination = tmp
+	}
+
+	if numBytes == 8 {
+		w = 1
+	}
+
+	if source > 0b111 {
+		r = 1
+		source &= 0b111
+	}
+
+	if offset > 0b111 {
+		x = 1
+		offset &= 0b111
+	}
+
+	if destination > 0b111 {
+		b = 1
+		destination &= 0b111
+	}
+
+	if destination == RBP || destination == R13 {
+		mod = AddressMemoryOffset8
+	}
+
+	if numBytes == 2 {
+		code = append(code, 0x66)
+	}
+
+	code = append(code, REX(w, r, x, b))
+	code = append(code, opCode)
+	code = append(code, ModRM(mod, byte(source), 0b100))
+	code = append(code, SIB(Scale1, byte(offset), byte(destination)))
+
+	if mod == AddressMemoryOffset8 {
+		code = append(code, 0x00)
+	}
+
+	return code
+}