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.

1 files changed, 2 insertions, 15 deletions

diff --git a/src/arch/wasm/CodeGen.zig b/src/arch/wasm/CodeGen.zig
index 97b43b3067..7a8efdfcc2 100644
--- a/src/arch/wasm/CodeGen.zig
+++ b/src/arch/wasm/CodeGen.zig
@@ -1037,7 +1037,7 @@ fn lowerDeclRef(self: *Self, ty: Type, val: Value, decl: *Module.Decl) InnerErro
     const offset = @intCast(u32, self.code.items.len);
     const atom = &self.decl.link.wasm;
     const target_sym_index = decl.link.wasm.sym_index;
-    markDeclAlive(decl);
+    decl.markAlive();
     if (decl.ty.zigTypeTag() == .Fn) {
         // We found a function pointer, so add it to our table,
         // as function pointers are not allowed to be stored inside the data section,
@@ -1935,7 +1935,7 @@ fn emitConstant(self: *Self, val: Value, ty: Type) InnerError!void {
                 try self.emitConstant(slice.data.len, Type.usize);
             } else if (val.castTag(.decl_ref)) |payload| {
                 const decl = payload.data;
-                markDeclAlive(decl);
+                decl.markAlive();
                 // Function pointers use a table index, rather than a memory address
                 if (decl.ty.zigTypeTag() == .Fn) {
                     const target_sym_index = decl.link.wasm.sym_index;
@@ -2101,19 +2101,6 @@ fn emitConstant(self: *Self, val: Value, ty: Type) InnerError!void {
     }
 }
 
-fn markDeclAlive(decl: *Decl) void {
-    if (decl.alive) return;
-    decl.alive = true;
-
-    // This is the first time we are marking this Decl alive. We must
-    // therefore recurse into its value and mark any Decl it references
-    // as also alive, so that any Decl referenced does not get garbage collected.
-
-    if (decl.val.pointerDecl()) |pointee| {
-        return markDeclAlive(pointee);
-    }
-}
-
 fn emitUndefined(self: *Self, ty: Type) InnerError!void {
     switch (ty.zigTypeTag()) {
         .Int => switch (ty.intInfo(self.target).bits) {