fix: shadow mapping must always allocate new registers

sno2 · Oct 31, 2024 · 761a639 · 761a639
1 parent 90be32e
commit 761a639
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Showing 2 changed files with 14 additions and 11 deletions.
diff --git a/examples/shadow.vl b/examples/shadow.vl
@@ -1,7 +1,7 @@
 (let ((a 2))
-    (+ a (let ((a 4))
-        (+ a (let ((a 6))
-            a
-        ))
-    ))
+  (+ (let ((a 4))
+    (+ (let ((a 6))
+      a
+    ) a)
+  ) a)
 )
diff --git a/src/CodeGen.zig b/src/CodeGen.zig
@@ -589,17 +589,20 @@ fn genExpression(cg: *CodeGen, exe: *Executable, is_tail: bool, comptime is_type
                         i -= 1;
                         const let = cg.let_stack.items[i];
                         const gop = try exe.locals.getOrPut(cg.gpa, let.identifier);
-                        if (!gop.found_existing) {
-                            gop.value_ptr.* = exe.allocLocal();
-                            if (is_typed) try exe.local_types.append(cg.gpa, let.type);
-                        } else if (is_typed) {
-                            exe.local_types.items[gop.value_ptr.*] = let.type;
+                        const old = if (gop.found_existing) gop.value_ptr.* else undefined;
+                        gop.value_ptr.* = exe.allocLocal();
+                        if (is_typed) {
+                            if (!gop.found_existing) {
+                                try exe.local_types.append(cg.gpa, let.type);
+                            } else {
+                                exe.local_types.items[gop.value_ptr.*] = let.type;
+                            }
                         }
                         try exe.emit(.move_local, gop.value_ptr.*, null);
                         if (gop.found_existing or cg.defines.contains(let.identifier)) {
                             try cg.shadow_stack.append(cg.gpa, .{
                                 .name = let.identifier,
-                                .old_local = if (gop.found_existing) gop.value_ptr.* else null,
+                                .old_local = if (gop.found_existing) old else null,
                             });
                         }
                     }