From 501cd997e91b6228505141062ebc68bbd350bf0a Mon Sep 17 00:00:00 2001
From: SimonFJ20 <simonfromjakobsen@gmail.com>
Date: Tue, 10 Dec 2024 15:45:19 +0100
Subject: [PATCH] add assembler

---
 compiler/Lowerer.ts         | 31 ++++++++----
 compiler/program_builder.ts | 97 +++++++++++++++++++++++++++++++++++++
 2 files changed, 119 insertions(+), 9 deletions(-)
 create mode 100644 compiler/program_builder.ts

diff --git a/compiler/Lowerer.ts b/compiler/Lowerer.ts
index c7525a5..3557730 100644
--- a/compiler/Lowerer.ts
+++ b/compiler/Lowerer.ts
@@ -2,10 +2,11 @@ import { Builtins } from "./arch.ts";
 import { BinaryType, Expr, Stmt } from "./ast.ts";
 import { LocalLeaf, Locals, LocalsFnRoot } from "./lowerer_locals.ts";
 import { Ops } from "./mod.ts";
+import { Assembler } from "./program_builder.ts";
 import { VType, vtypeToString } from "./vtypes.ts";
 
 export class Lowerer {
-    private program: number[] = [];
+    private program = new Assembler();
     private locals: Locals = new LocalsFnRoot();
     private fnStmtIdAddrMap: { [key: number]: number } = {};
 
@@ -16,7 +17,7 @@ export class Lowerer {
     }
 
     public finish(): number[] {
-        return this.program;
+        return this.program.assemble();
     }
 
     private lowerStaticStmt(stmt: Stmt) {
@@ -60,7 +61,7 @@ export class Lowerer {
         const outerLocals = this.locals;
         this.locals = new LocalsFnRoot(outerLocals);
         const outerProgram = this.program;
-        this.program = [];
+        this.program = new Assembler();
 
         for (const { ident } of stmt.kind.params) {
             this.locals.allocSym(ident);
@@ -73,7 +74,7 @@ export class Lowerer {
         this.program.push(Ops.Return);
 
         this.locals = outerLocals;
-        outerProgram.push(...this.program);
+        outerProgram.concat(this.program);
         this.program = outerProgram;
     }
 
@@ -222,13 +223,25 @@ export class Lowerer {
         if (expr.kind.type !== "if") {
             throw new Error();
         }
+
+        const falseLabel = this.program.makeLabel();
+        const doneLabel = this.program.makeLabel();
+
         this.lowerExpr(expr.kind.cond);
+
+        this.program.push(Ops.Not, Ops.JumpIfTrue);
+        this.program.addRef(falseLabel);
+
         this.lowerExpr(expr.kind.truthy);
-        const falsyIndex = this.program.length;
-        if (expr.kind.falsy) {
-            this.lowerExpr(expr.kind.falsy);
-        }
-        const doneIndex = this.program.length;
+
+        this.program.push(Ops.Jump);
+        this.program.addRef(doneLabel);
+
+        this.program.setLabel(falseLabel);
+
+        this.lowerExpr(expr.kind.falsy!);
+
+        this.program.setLabel(doneLabel);
     }
 
     private lowerBlockExpr(expr: Expr) {
diff --git a/compiler/program_builder.ts b/compiler/program_builder.ts
new file mode 100644
index 0000000..83097e9
--- /dev/null
+++ b/compiler/program_builder.ts
@@ -0,0 +1,97 @@
+import { Ops } from "./arch.ts";
+
+export type Line = {
+    labels?: number[];
+} & LineKind;
+
+export type Label = { label: number };
+
+export type LineKind =
+    | { type: "op"; op: number }
+    | { type: "lit"; val: number }
+    | { type: "ref"; label: number };
+
+export class Assembler {
+    private lines: Line[] = [];
+    private labelCounter = 0;
+
+    public push(...values: number[]) {
+        for (const value of values) {
+            this.addLit(value);
+        }
+    }
+
+    public addOp(op: number): Assembler {
+        this.lines.push({ type: "op", op });
+        return this;
+    }
+
+    public addLit(val: number): Assembler {
+        this.lines.push({ type: "lit", val });
+        return this;
+    }
+
+    public addRef({ label }: Label): Assembler {
+        this.lines.push({ type: "ref", label });
+        return this;
+    }
+
+    public setLabel({ label }: Label): Assembler {
+        const line = this.lines.at(-1);
+        if (line === undefined) {
+            return this;
+        }
+        if (line.labels === undefined) {
+            line.labels = [];
+        }
+        line.labels.push(label);
+        return this;
+    }
+
+    public makeLabel(): Label {
+        const label = this.labelCounter;
+        this.labelCounter += 1;
+        return { label };
+    }
+
+    public concat(assembler: Assembler) {
+        this.lines.push(...assembler.lines);
+    }
+
+    public assemble(): number[] {
+        let ip = 0;
+        const output: number[] = [];
+        const locs: { [key: number]: number } = {};
+        const refs: { [key: number]: number } = {};
+        for (const line of this.lines) {
+            switch (line.type) {
+                case "op":
+                    output.push(line.op);
+                    ip += 1;
+                    break;
+                case "lit":
+                    output.push(line.val);
+                    ip += 1;
+                    break;
+                case "ref":
+                    output.push(0);
+                    refs[ip] = line.label;
+                    ip += 1;
+                    break;
+            }
+        }
+        for (let i = 0; i < output.length; ++i) {
+            if (!(i in refs)) {
+                continue;
+            }
+            if (!(refs[i] in locs)) {
+                console.error(
+                    `Assembler: label '${refs[i]}' used at ${i} not defined`,
+                );
+                continue;
+            }
+            output[i] = locs[refs[i]];
+        }
+        return output;
+    }
+}