From 0e11812af3439fc0cecebcb6723b420fc7c4dc75 Mon Sep 17 00:00:00 2001
From: Eduard Urbach <eduard@urbach.dev>
Date: Thu, 9 Oct 2025 11:37:21 +0200
Subject: [PATCH] Added more tests for LoadAddress on arm64

---
 src/arm/LoadAddress.go      | 15 ++++++++++-----
 src/arm/LoadAddress_test.go | 12 +++++++++---
 src/arm/arm_test.go         |  4 ++++
 src/arm/mask.go             |  1 +
 src/asm/compilerARM.go      | 22 ++++++++++++++++++----
 5 files changed, 42 insertions(+), 12 deletions(-)

diff --git a/src/arm/LoadAddress.go b/src/arm/LoadAddress.go
index 1d60287..d570303 100644
--- a/src/arm/LoadAddress.go
+++ b/src/arm/LoadAddress.go
@@ -2,9 +2,14 @@ package arm
 
 import "git.urbach.dev/cli/q/src/cpu"
 
-// LoadAddress calculates the address with the PC-relative offset and writes the result to the destination register.
-func LoadAddress(destination cpu.Register, offset int) uint32 {
-	hi := uint32(offset) >> 2
-	lo := uint32(offset) & 0b11
-	return lo<<29 | 0b10000<<24 | hi<<5 | uint32(destination)
+// LoadAddress calculates the address with the PC-relative offset in the range -1048576 to 1048575
+// and writes the result to the destination register.
+func LoadAddress(destination cpu.Register, offset int) (code uint32, encodable bool) {
+	if offset < -1048576 || offset > 1048575 {
+		return 0, false
+	}
+
+	hi := uint32(offset>>2) & mask19
+	lo := uint32(offset) & mask2
+	return lo<<29 | 0b10000<<24 | hi<<5 | uint32(destination), true
 }
\ No newline at end of file
diff --git a/src/arm/LoadAddress_test.go b/src/arm/LoadAddress_test.go
index d43a836..95bdaed 100644
--- a/src/arm/LoadAddress_test.go
+++ b/src/arm/LoadAddress_test.go
@@ -11,17 +11,23 @@ import (
 func TestLoadAddress(t *testing.T) {
 	usagePatterns := []struct {
 		Destination cpu.Register
-		Number      int
+		Offset      int
 		Code        uint32
 	}{
+		{arm.X0, 0, 0x10000000},
+		{arm.X0, 4, 0x10000020},
+		{arm.X0, -4, 0x10FFFFE0},
 		{arm.X0, 56, 0x100001C0},
+		{arm.X0, -1048576, 0x10800000},
+		{arm.X0, 1048575, 0x707FFFE0},
 		{arm.X1, 80, 0x10000281},
 		{arm.X16, 0x3000, 0x10018010},
 	}
 
 	for _, pattern := range usagePatterns {
-		t.Logf("adr %s, %d", pattern.Destination, pattern.Number)
-		code := arm.LoadAddress(pattern.Destination, pattern.Number)
+		t.Logf("adr %s, %d", pattern.Destination, pattern.Offset)
+		code, encodable := arm.LoadAddress(pattern.Destination, pattern.Offset)
+		assert.True(t, encodable)
 		assert.Equal(t, code, pattern.Code)
 	}
 }
\ No newline at end of file
diff --git a/src/arm/arm_test.go b/src/arm/arm_test.go
index dbc29d5..0c7bd99 100644
--- a/src/arm/arm_test.go
+++ b/src/arm/arm_test.go
@@ -33,4 +33,8 @@ func TestNotEncodable(t *testing.T) {
 	assert.False(t, encodable)
 	_, encodable = arm.SubRegisterNumber(arm.X0, arm.X0, 0xF0000000)
 	assert.False(t, encodable)
+	_, encodable = arm.LoadAddress(arm.X0, -1048577)
+	assert.False(t, encodable)
+	_, encodable = arm.LoadAddress(arm.X0, 1048576)
+	assert.False(t, encodable)
 }
\ No newline at end of file
diff --git a/src/arm/mask.go b/src/arm/mask.go
index c7850f8..7bdb6cf 100644
--- a/src/arm/mask.go
+++ b/src/arm/mask.go
@@ -1,6 +1,7 @@
 package arm
 
 const (
+	mask2  = 0b11
 	mask6  = 0b111111
 	mask7  = 0b1111111
 	mask9  = 0b1_11111111
diff --git a/src/asm/compilerARM.go b/src/asm/compilerARM.go
index d084bf7..161ea80 100644
--- a/src/asm/compilerARM.go
+++ b/src/asm/compilerARM.go
@@ -45,7 +45,8 @@ func (c *compilerARM) Compile(instr Instruction) {
 			return code
 		}
 	case *CallExtern:
-		c.append(arm.LoadAddress(arm.X16, 0))
+		encoding, _ := arm.LoadAddress(arm.X16, 0)
+		c.append(encoding)
 		patch := c.PatchLast4Bytes()
 		c.append(arm.LoadFixedOffset(arm.X16, arm.X16, arm.UnscaledImmediate, 0, 8))
 		c.append(arm.CallRegister(arm.X16))
@@ -59,7 +60,13 @@ func (c *compilerARM) Compile(instr Instruction) {
 
 			address := c.importsStart + index*8
 			offset := address - patch.start
-			binary.LittleEndian.PutUint32(code, arm.LoadAddress(arm.X16, offset))
+			encoding, encodable := arm.LoadAddress(arm.X16, offset)
+
+			if !encodable {
+				panic("label offset outside of encodable range")
+			}
+
+			binary.LittleEndian.PutUint32(code, encoding)
 			return code
 		}
 	case *CallExternStart:
@@ -155,7 +162,8 @@ func (c *compilerARM) Compile(instr Instruction) {
 		c.append(arm.DivSignedRegisterRegister(instr.Destination, instr.Source, instr.Operand))
 		c.append(arm.MultiplySubtract(instr.Destination, instr.Destination, instr.Operand, instr.Source))
 	case *MoveLabel:
-		c.append(arm.LoadAddress(instr.Destination, 0))
+		encoding, _ := arm.LoadAddress(instr.Destination, 0)
+		c.append(encoding)
 		patch := c.PatchLast4Bytes()
 
 		patch.apply = func(code []byte) []byte {
@@ -166,7 +174,13 @@ func (c *compilerARM) Compile(instr Instruction) {
 			}
 
 			offset := address - patch.start
-			binary.LittleEndian.PutUint32(code, arm.LoadAddress(instr.Destination, offset))
+			encoding, encodable := arm.LoadAddress(instr.Destination, offset)
+
+			if !encodable {
+				panic("label offset outside of encodable range")
+			}
+
+			binary.LittleEndian.PutUint32(code, encoding)
 			return code
 		}
 	case *Move:
-- 
2.51.2