Improved Windows ABI support

src/x86/AlignStack.go

@@ -1,6 +0,0 @@
-package x86
-
-// AlignStack aligns RSP on a 16-byte boundary.
-func AlignStack(code []byte) []byte {
-	return append(code, 0x48, 0x83, 0xE4, 0xF0)
-}

src/x86/Push.go

@@ -1,6 +1,31 @@
 package x86
 
-import "git.akyoto.dev/cli/q/src/cpu"
+import (
+	"git.akyoto.dev/cli/q/src/cpu"
+	"git.akyoto.dev/cli/q/src/sizeof"
+)
+
+// PushNumber pushes a number onto the stack.
+func PushNumber(code []byte, number int) []byte {
+	length := sizeof.Signed(number)
+
+	if length >= 8 {
+		panic("x86 does not support pushing 64-bit numbers")
+	}
+
+	if length >= 2 {
+		return append(
+			code,
+			0x68,
+			byte(number),
+			byte(number>>8),
+			byte(number>>16),
+			byte(number>>24),
+		)
+	}
+
+	return append(code, 0x6A, byte(number))
+}
 
 // PushRegister pushes the value inside the register onto the stack.
 func PushRegister(code []byte, register cpu.Register) []byte {

src/x86/Push_test.go

@@ -8,6 +8,28 @@ import (
 	"git.akyoto.dev/go/assert"
 )
 
+func TestPushNumber(t *testing.T) {
+	usagePatterns := []struct {
+		Number int
+		Code   []byte
+	}{
+		{0, []byte{0x6A, 0x00}},
+		{1, []byte{0x6A, 0x01}},
+		{-1, []byte{0x6A, 0xFF}},
+		{127, []byte{0x6A, 0x7F}},
+		{128, []byte{0x68, 0x80, 0x00, 0x00, 0x00}},
+		{0xFF, []byte{0x68, 0xFF, 0x00, 0x00, 0x00}},
+		{0xFFFF, []byte{0x68, 0xFF, 0xFF, 0x00, 0x00}},
+		{0x7FFFFFFF, []byte{0x68, 0xFF, 0xFF, 0xFF, 0x7F}},
+	}
+
+	for _, pattern := range usagePatterns {
+		t.Logf("push %d", pattern.Number)
+		code := x86.PushNumber(nil, pattern.Number)
+		assert.DeepEqual(t, code, pattern.Code)
+	}
+}
+
 func TestPushRegister(t *testing.T) {
 	usagePatterns := []struct {
 		Register cpu.Register

src/x86/Registers.go

@@ -25,7 +25,7 @@ var (
 	AllRegisters             = []cpu.Register{RAX, RCX, RDX, RBX, RSP, RBP, RSI, RDI, R8, R9, R10, R11, R12, R13, R14, R15}
 	SyscallInputRegisters    = []cpu.Register{RAX, RDI, RSI, RDX, R10, R8, R9}
 	SyscallOutputRegisters   = []cpu.Register{RAX, RCX, R11}
-	GeneralRegisters         = []cpu.Register{RBX, R12, R13, R14, R15, RCX, R11, RBP}
+	GeneralRegisters         = []cpu.Register{RBX, R12, R13, R14, R15, RCX, R11}
 	InputRegisters           = SyscallInputRegisters
 	OutputRegisters          = SyscallInputRegisters
 	WindowsInputRegisters    = []cpu.Register{RCX, RDX, R8, R9}

src/x86/x86_test.go

@@ -8,7 +8,6 @@ import (
 )
 
 func TestX86(t *testing.T) {
-	assert.DeepEqual(t, x86.AlignStack(nil), []byte{0x48, 0x83, 0xE4, 0xF0})
 	assert.DeepEqual(t, x86.Call(nil, 1), []byte{0xE8, 0x01, 0x00, 0x00, 0x00})
 	assert.DeepEqual(t, x86.CallAtAddress(nil, 1), []byte{0xFF, 0x15, 0x01, 0x00, 0x00, 0x00})
 	assert.DeepEqual(t, x86.ExtendRAXToRDX(nil), []byte{0x48, 0x99})