From 9867550c110316718b3c031f5a93aed13293ddc4 Mon Sep 17 00:00:00 2001
From: Eduard Urbach <eduard@urbach.dev>
Date: Fri, 28 Jun 2024 10:28:23 +0200
Subject: [PATCH] Reduced memory usage

---
 src/build/Debug.go    | 22 ----------------------
 src/build/Function.go |  4 ++--
 src/build/Result.go   |  4 ++--
 src/build/compile.go  | 24 ++++++++++++++----------
 src/build/debug.go    | 24 ++++++++++++++++++++++++
 5 files changed, 42 insertions(+), 36 deletions(-)
 delete mode 100644 src/build/Debug.go
 create mode 100644 src/build/debug.go

diff --git a/src/build/Debug.go b/src/build/Debug.go
deleted file mode 100644
index 5f95db4..0000000
--- a/src/build/Debug.go
+++ /dev/null
@@ -1,22 +0,0 @@
-package build
-
-import "git.akyoto.dev/cli/q/src/build/token"
-
-type debug struct {
-	pos         int
-	instruction token.List
-}
-
-func (f *Function) debugLine(instructionIndex int) token.List {
-	for _, record := range f.debug {
-		if record.pos == instructionIndex {
-			return record.instruction
-		}
-
-		if record.pos > instructionIndex {
-			return nil
-		}
-	}
-
-	return nil
-}
diff --git a/src/build/Function.go b/src/build/Function.go
index 7a2b103..16a8c8c 100644
--- a/src/build/Function.go
+++ b/src/build/Function.go
@@ -64,7 +64,7 @@ func (f *Function) CompileTokens(body token.List) error {
 
 				if config.Verbose {
 					f.debug = append(f.debug, debug{
-						pos:         len(f.Assembler.Instructions),
+						position:    len(f.Assembler.Instructions),
 						instruction: instruction,
 					})
 				}
@@ -233,7 +233,7 @@ func (f *Function) PrintAsm() {
 	ansi.Dim.Println("╭──────────────────────────────────────╮")
 
 	for i, x := range f.Assembler.Instructions {
-		instruction := f.debugLine(i)
+		instruction := f.instructionAt(i)
 
 		if instruction != nil {
 			ansi.Dim.Println("├──────────────────────────────────────┤")
diff --git a/src/build/Result.go b/src/build/Result.go
index 615cbb8..bfebb2e 100644
--- a/src/build/Result.go
+++ b/src/build/Result.go
@@ -10,7 +10,7 @@ import (
 type Result struct {
 	Used             []*Function
 	Unused           map[string]*Function
-	instructionCount int
+	InstructionCount int
 }
 
 // Finalize generates the final machine code.
@@ -20,7 +20,7 @@ func (r Result) Finalize() ([]byte, []byte) {
 	// The reason we call `main` instead of using `main` itself is to place
 	// a return address on the stack, which allows return statements in `main`.
 	final := asm.Assembler{
-		Instructions: make([]asm.Instruction, 0, r.instructionCount+4),
+		Instructions: make([]asm.Instruction, 0, r.InstructionCount+4),
 	}
 
 	final.Call("main")
diff --git a/src/build/compile.go b/src/build/compile.go
index c028a68..6ffade3 100644
--- a/src/build/compile.go
+++ b/src/build/compile.go
@@ -39,8 +39,6 @@ func compile(functions <-chan *Function, errors <-chan error) (Result, error) {
 		if function.Error != nil {
 			return result, function.Error
 		}
-
-		result.instructionCount += len(function.Assembler.Instructions)
 	}
 
 	main, exists := result.Unused["main"]
@@ -49,8 +47,8 @@ func compile(functions <-chan *Function, errors <-chan error) (Result, error) {
 		return result, fail.MissingMainFunction
 	}
 
-	result.Used = append(result.Used, main)
-	delete(result.Unused, "main")
+	result.Used = make([]*Function, 0, len(result.Unused))
+	result.markAlive(main)
 	result.findAliveCode(main)
 
 	return result, nil
@@ -73,21 +71,27 @@ func compileFunctions(functions map[string]*Function) {
 }
 
 // findAliveCode recursively finds all the calls to external functions and marks them as required.
-func (result *Result) findAliveCode(f *Function) {
-	for _, x := range f.Assembler.Instructions {
+func (result *Result) findAliveCode(caller *Function) {
+	for _, x := range caller.Assembler.Instructions {
 		if x.Mnemonic != asm.CALL {
 			continue
 		}
 
 		name := x.Data.(*asm.Label).Name
-		called, exists := result.Unused[name]
+		callee, exists := result.Unused[name]
 
 		if !exists {
 			continue
 		}
 
-		result.Used = append(result.Used, called)
-		delete(result.Unused, name)
-		result.findAliveCode(called)
+		result.markAlive(callee)
+		result.findAliveCode(callee)
 	}
 }
+
+// markAlive marks a function as being alive.
+func (result *Result) markAlive(f *Function) {
+	result.Used = append(result.Used, f)
+	result.InstructionCount += len(f.Assembler.Instructions)
+	delete(result.Unused, f.Name)
+}
diff --git a/src/build/debug.go b/src/build/debug.go
new file mode 100644
index 0000000..0292457
--- /dev/null
+++ b/src/build/debug.go
@@ -0,0 +1,24 @@
+package build
+
+import "git.akyoto.dev/cli/q/src/build/token"
+
+// debug is used to look up instructions at a certain index.
+type debug struct {
+	position    int
+	instruction token.List
+}
+
+// instructionAt retrieves the instruction at the given index.
+func (f *Function) instructionAt(index int) token.List {
+	for _, record := range f.debug {
+		if record.position == index {
+			return record.instruction
+		}
+
+		if record.position > index {
+			return nil
+		}
+	}
+
+	return nil
+}