improved pointers

src/mir_interpreter.ts

@@ -2,7 +2,6 @@ import * as mir from "./middle.ts";
 
 export class FnInterpreter {
     private regs = new Map<mir.Inst, Val>();
-    private locals: (Val | null)[] = [];
     private bb: mir.BasicBlock;
     private instIdx = 0;
 
@@ -42,33 +41,31 @@ export class FnInterpreter {
                     break;
                 }
                 case "Alloca": {
-                    const localIdx = this.locals.length;
-                    this.locals.push(null);
                     this.regs.set(
                         inst,
-                        new Val({ tag: "LocalPtr", localIdx, mutable: true }),
+                        new Val({
+                            tag: "Ptr",
+                            mutable: true,
+                            value: new Val({ tag: "Null" }),
+                        }),
                     );
                     break;
                 }
                 case "Load": {
-                    const source = this.regs.get(k.source);
-                    if (!source || source.kind.tag !== "LocalPtr") {
+                    const source = this.regs.get(k.source)!;
+                    if (source.kind.tag !== "Ptr") {
                         throw new Error();
                     }
-                    const value = this.locals[source.kind.localIdx];
-                    if (!value) {
-                        throw new Error();
-                    }
-                    this.regs.set(inst, value);
+                    this.regs.set(inst, source.kind.value);
                     break;
                 }
                 case "Store": {
                     const target = this.regs.get(k.target)!;
-                    if (target.kind.tag !== "LocalPtr") {
+                    if (target.kind.tag !== "Ptr") {
                         throw new Error();
                     }
                     const source = this.regs.get(k.source)!;
-                    this.locals[target.kind.localIdx] = source;
+                    target.kind.value = source;
                     break;
                 }
                 case "Jump": {
@@ -207,12 +204,14 @@ class Val {
     pretty() {
         const k = this.kind;
         switch (k.tag) {
+            case "Null":
+                return "<null>";
             case "Void":
                 return "void";
             case "Int":
             case "Bool":
                 return `${k.value}`;
-            case "LocalPtr":
+            case "Ptr":
                 return `<pointer>`;
             case "Fn":
                 return `<${k.fn.ty.pretty()}>`;
@@ -223,8 +222,9 @@ class Val {
 }
 
 type ValKind =
+    | { tag: "Null" }
     | { tag: "Void" }
     | { tag: "Int"; value: number }
     | { tag: "Bool"; value: boolean }
-    | { tag: "LocalPtr"; mutable: boolean; localIdx: number }
+    | { tag: "Ptr"; mutable: boolean; value: Val }
     | { tag: "Fn"; fn: mir.Fn };

tests/pointer.ethlang

@@ -1,4 +1,9 @@
 
+fn change_to(place: *mut int, value: int)
+{
+    *place = value;
+}
+
 fn main()
 {
     let a = 1;
@@ -19,5 +24,10 @@ fn main()
     print_int(a);
     // expect: 3
     print_int(*c);
+
+    change_to(&mut a, 4);
+
+    // expect: 4
+    print_int(a);
 }
 

tests/test.sh

@@ -29,7 +29,7 @@ run_test_file() {
     then
         if grep -q '// expect:' $file
         then
-            expected=$(grep '// expect:' $file | sed -E 's/\s*\/\/\s+expect: (.*?)/\1/g')
+            expected=$(grep '// expect:' $file | sed -E 's/\s*\/\/\s+expect:\s*(.*?)\s*/\1/g')
             if [[ $output != $expected ]]
             then
                 echo "-- failed: incorrect output --"