Zcu: rework exports

This commit reworks our representation of exported Decls and values in
Zcu to be memory-optimized and trivially serialized.

All exports are now stored in the `all_exports` array on `Zcu`. An
`AnalUnit` which performs an export (either through an `export`
annotation or by containing an analyzed `@export`) gains an entry into
`single_exports` if it performs only one export, or `multi_exports` if
it performs multiple.

We no longer store a persistent mapping from a `Decl`/value to all
exports of that entity; this state is not necessary for the majority of
the pipeline. Instead, we construct it in `Zcu.processExports`, just
before flush. This does not affect the algorithmic complexity of
`processExports`, since this function already iterates all exports in
the `Zcu`.

The elimination of `decl_exports` and `value_exports` led to a few
non-trivial backend changes. The LLVM backend has been wrangled into a
more reasonable state in general regarding exports and externs. The C
backend is currently disabled in this commit, because its support for
`export` was quite broken, and that was exposed by this work -- I'm
hoping @jacobly0 will be able to pick this up!

1 files changed, 6 insertions, 6 deletions

diff --git a/src/link.zig b/src/link.zig
index 75a9723f1c..36a5cb8187 100644
--- a/src/link.zig
+++ b/src/link.zig
@@ -606,12 +606,12 @@ pub const File = struct {
         base: *File,
         module: *Module,
         exported: Module.Exported,
-        exports: []const *Module.Export,
+        export_indices: []const u32,
     ) UpdateExportsError!void {
         switch (base.tag) {
             inline else => |tag| {
                 if (tag != .c and build_options.only_c) unreachable;
-                return @as(*tag.Type(), @fieldParentPtr("base", base)).updateExports(module, exported, exports);
+                return @as(*tag.Type(), @fieldParentPtr("base", base)).updateExports(module, exported, export_indices);
             },
         }
     }
@@ -671,11 +671,11 @@ pub const File = struct {
         }
     }
 
-    pub fn deleteDeclExport(
+    pub fn deleteExport(
         base: *File,
-        decl_index: InternPool.DeclIndex,
+        exported: Zcu.Exported,
         name: InternPool.NullTerminatedString,
-    ) !void {
+    ) void {
         if (build_options.only_c) @compileError("unreachable");
         switch (base.tag) {
             .plan9,
@@ -685,7 +685,7 @@ pub const File = struct {
             => {},
 
             inline else => |tag| {
-                return @as(*tag.Type(), @fieldParentPtr("base", base)).deleteDeclExport(decl_index, name);
+                return @as(*tag.Type(), @fieldParentPtr("base", base)).deleteExport(exported, name);
             },
         }
     }