From a5c7742ba6fc793608b8bb7ba058e33eccd9cfec Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Sat, 15 Jan 2022 00:17:25 -0700
Subject: stage2: fix Decl garbage collection not marking enough

It is the job of codegen backends to mark Decls that are referenced as
alive so that the frontend does not sweep them with the garbage. This
commit unifies the code between the backends with an added method on
Decl.

The implementation is more complete than before, switching on the Decl
val tag and recursing into sub-values.

As a result, two more array tests are passing.
---
 src/value.zig | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

(limited to 'src/value.zig')

diff --git a/src/value.zig b/src/value.zig
index 1993a853cd..1836a14ce0 100644
--- a/src/value.zig
+++ b/src/value.zig
@@ -1746,6 +1746,55 @@ pub const Value = extern union {
         };
     }
 
+    pub fn markReferencedDeclsAlive(val: Value) void {
+        switch (val.tag()) {
+            .decl_ref_mut => return val.castTag(.decl_ref_mut).?.data.decl.markAlive(),
+            .extern_fn, .decl_ref => return val.cast(Payload.Decl).?.data.markAlive(),
+            .function => return val.castTag(.function).?.data.owner_decl.markAlive(),
+            .variable => return val.castTag(.variable).?.data.owner_decl.markAlive(),
+
+            .repeated,
+            .eu_payload,
+            .eu_payload_ptr,
+            .opt_payload,
+            .opt_payload_ptr,
+            .empty_array_sentinel,
+            => return markReferencedDeclsAlive(val.cast(Payload.SubValue).?.data),
+
+            .array => {
+                for (val.cast(Payload.Array).?.data) |elem_val| {
+                    markReferencedDeclsAlive(elem_val);
+                }
+            },
+            .slice => {
+                const slice = val.cast(Payload.Slice).?.data;
+                markReferencedDeclsAlive(slice.ptr);
+                markReferencedDeclsAlive(slice.len);
+            },
+
+            .elem_ptr => {
+                const elem_ptr = val.cast(Payload.ElemPtr).?.data;
+                return markReferencedDeclsAlive(elem_ptr.array_ptr);
+            },
+            .field_ptr => {
+                const field_ptr = val.cast(Payload.FieldPtr).?.data;
+                return markReferencedDeclsAlive(field_ptr.container_ptr);
+            },
+            .@"struct" => {
+                for (val.cast(Payload.Struct).?.data) |field_val| {
+                    markReferencedDeclsAlive(field_val);
+                }
+            },
+            .@"union" => {
+                const data = val.cast(Payload.Union).?.data;
+                markReferencedDeclsAlive(data.tag);
+                markReferencedDeclsAlive(data.val);
+            },
+
+            else => {},
+        }
+    }
+
     pub fn slicePtr(val: Value) Value {
         return switch (val.tag()) {
             .slice => val.castTag(.slice).?.data.ptr,
-- 
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