From f04e9d7a60eb4e5a452fc844ed96714664aec8be Mon Sep 17 00:00:00 2001
From: Eduard Urbach <admin@akyoto.dev>
Date: Fri, 14 Jun 2024 10:46:45 +0200
Subject: [PATCH] Implemented return keyword

---
 src/build/Function.go         | 7 +++++++
 src/build/asm/Assembler.go    | 6 ++++++
 src/build/asm/Instructions.go | 5 +++++
 src/build/asm/Mnemonic.go     | 4 ++++
 4 files changed, 22 insertions(+)

diff --git a/src/build/Function.go b/src/build/Function.go
index 11c84ed..729c5c5 100644
--- a/src/build/Function.go
+++ b/src/build/Function.go
@@ -34,6 +34,13 @@ func (f *Function) Compile() {
 			continue
 		}
 
+		if line[0].Kind == token.Keyword {
+			switch line[0].Text() {
+			case "return":
+				f.Assembler.Return()
+			}
+		}
+
 		if line[0].Kind == token.Identifier && line[0].Text() == "syscall" {
 			paramTokens := line[2 : len(line)-1]
 			start := 0
diff --git a/src/build/asm/Assembler.go b/src/build/asm/Assembler.go
index 94a4ce7..01379f9 100644
--- a/src/build/asm/Assembler.go
+++ b/src/build/asm/Assembler.go
@@ -38,8 +38,14 @@ func (a *Assembler) Finalize() ([]byte, []byte) {
 				})
 			}
 
+		case RETURN:
+			code = x64.Return(code)
+
 		case SYSCALL:
 			code = x64.Syscall(code)
+
+		default:
+			panic("Unknown mnemonic: " + x.Mnemonic.String())
 		}
 	}
 
diff --git a/src/build/asm/Instructions.go b/src/build/asm/Instructions.go
index 0cd9014..f201af9 100644
--- a/src/build/asm/Instructions.go
+++ b/src/build/asm/Instructions.go
@@ -26,6 +26,11 @@ func (a *Assembler) MoveRegisterAddress(reg cpu.Register, address Address) {
 	})
 }
 
+// Return returns back to the caller.
+func (a *Assembler) Return() {
+	a.Instructions = append(a.Instructions, Instruction{Mnemonic: RETURN})
+}
+
 // Syscall executes a kernel function.
 func (a *Assembler) Syscall() {
 	a.Instructions = append(a.Instructions, Instruction{Mnemonic: SYSCALL})
diff --git a/src/build/asm/Mnemonic.go b/src/build/asm/Mnemonic.go
index cd7f033..7fd1a06 100644
--- a/src/build/asm/Mnemonic.go
+++ b/src/build/asm/Mnemonic.go
@@ -5,6 +5,7 @@ type Mnemonic uint8
 const (
 	NONE Mnemonic = iota
 	MOVE
+	RETURN
 	SYSCALL
 )
 
@@ -14,6 +15,9 @@ func (m Mnemonic) String() string {
 	case MOVE:
 		return "move"
 
+	case RETURN:
+		return "return"
+
 	case SYSCALL:
 		return "syscall"
 	}