elf: increase Atom.Index resolution to u32

src/link/Elf.zig

@@ -887,7 +887,7 @@ pub fn populateMissingMetadata(self: *Elf) !void {
             } });
             self.zig_module_index = index;
             const zig_module = self.file(index).?.zig_module;
-
+            try zig_module.atoms.append(gpa, 0); // null input section
             const name_off = try self.strtab.insert(gpa, std.fs.path.stem(module.main_mod.root_src_path));
             const symbol_index = try self.addSymbol();
             try zig_module.local_symbols.append(gpa, symbol_index);
@@ -1319,7 +1319,7 @@ pub fn flushModule(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node
     // the relocations, and commit objects to file.
     if (self.zig_module_index) |index| {
         const zig_module = self.file(index).?.zig_module;
-        for (zig_module.atoms.keys()) |atom_index| {
+        for (zig_module.atoms.items) |atom_index| {
             const atom_ptr = self.atom(atom_index).?;
             if (!atom_ptr.flags.alive) continue;
             const shdr = &self.shdrs.items[atom_ptr.outputShndx().?];
@@ -3245,7 +3245,7 @@ pub fn updateDeclExports(
         };
         const esym = &zig_module.global_esyms.items[sym_index & 0x0fffffff];
         esym.st_value = decl_sym.value;
-        esym.st_shndx = decl_sym.atom_index;
+        esym.st_shndx = decl_esym.st_shndx;
         esym.st_info = (stb_bits << 4) | stt_bits;
         esym.st_name = name_off;
     }

src/link/Elf/Atom.zig

@@ -14,13 +14,13 @@ size: u64 = 0,
 alignment: Alignment = .@"1",
 
 /// Index of the input section.
-input_section_index: Index = 0,
+input_section_index: u16 = 0,
 
 /// Index of the output section.
 output_section_index: u16 = 0,
 
 /// Index of the input section containing this atom's relocs.
-relocs_section_index: Index = 0,
+relocs_section_index: u16 = 0,
 
 /// Index of this atom in the linker's atoms table.
 atom_index: Index = 0,
@@ -216,7 +216,6 @@ pub fn free(self: *Atom, elf_file: *Elf) void {
     log.debug("freeAtom {d} ({s})", .{ self.atom_index, self.name(elf_file) });
 
     const gpa = elf_file.base.allocator;
-    const zig_module = self.file(elf_file).?.zig_module;
     const shndx = self.outputShndx().?;
     const meta = elf_file.last_atom_and_free_list_table.getPtr(shndx).?;
     const free_list = &meta.free_list;
@@ -267,7 +266,9 @@ pub fn free(self: *Atom, elf_file: *Elf) void {
 
     // TODO create relocs free list
     self.freeRelocs(elf_file);
-    assert(zig_module.atoms.swapRemove(self.atom_index));
+    // TODO figure out how to free input section mappind in ZigModule
+    // const zig_module = self.file(elf_file).?.zig_module;
+    // assert(zig_module.atoms.swapRemove(self.atom_index));
     self.* = .{};
 }
 
@@ -698,10 +699,7 @@ fn format2(
     }
 }
 
-// TODO this has to be u32 but for now, to avoid redesigning elfSym machinery for
-// ZigModule, keep it at u16 with the intention of bumping it to u32 in the near
-// future.
-pub const Index = u16;
+pub const Index = u32;
 
 pub const Flags = packed struct {
     /// Specifies whether this atom is alive or has been garbage collected.

src/link/Elf/ZigModule.zig

@@ -13,7 +13,7 @@ local_symbols: std.ArrayListUnmanaged(Symbol.Index) = .{},
 global_symbols: std.ArrayListUnmanaged(Symbol.Index) = .{},
 globals_lookup: std.AutoHashMapUnmanaged(u32, Symbol.Index) = .{},
 
-atoms: std.AutoArrayHashMapUnmanaged(Atom.Index, void) = .{},
+atoms: std.ArrayListUnmanaged(Atom.Index) = .{},
 relocs: std.ArrayListUnmanaged(std.ArrayListUnmanaged(elf.Elf64_Rela)) = .{},
 
 output_symtab_size: Elf.SymtabSize = .{},
@@ -56,7 +56,8 @@ pub fn addAtom(self: *ZigModule, elf_file: *Elf) !Symbol.Index {
     const symbol_index = try elf_file.addSymbol();
     const esym_index = try self.addLocalEsym(gpa);
 
-    try self.atoms.putNoClobber(gpa, atom_index, {});
+    const shndx = @as(u16, @intCast(self.atoms.items.len));
+    try self.atoms.append(gpa, atom_index);
     try self.local_symbols.append(gpa, symbol_index);
 
     const atom_ptr = elf_file.atom(atom_index).?;
@@ -67,10 +68,10 @@ pub fn addAtom(self: *ZigModule, elf_file: *Elf) !Symbol.Index {
     symbol_ptr.atom_index = atom_index;
 
     const esym = &self.local_esyms.items[esym_index];
-    esym.st_shndx = atom_index;
+    esym.st_shndx = shndx;
     symbol_ptr.esym_index = esym_index;
 
-    const relocs_index = @as(Atom.Index, @intCast(self.relocs.items.len));
+    const relocs_index = @as(u16, @intCast(self.relocs.items.len));
     const relocs = try self.relocs.addOne(gpa);
     relocs.* = .{};
     atom_ptr.relocs_section_index = relocs_index;
@@ -86,7 +87,7 @@ pub fn resolveSymbols(self: *ZigModule, elf_file: *Elf) void {
         if (esym.st_shndx == elf.SHN_UNDEF) continue;
 
         if (esym.st_shndx != elf.SHN_ABS and esym.st_shndx != elf.SHN_COMMON) {
-            const atom_index = esym.st_shndx;
+            const atom_index = self.atoms.items[esym.st_shndx];
             const atom = elf_file.atom(atom_index) orelse continue;
             if (!atom.flags.alive) continue;
         }
@@ -95,7 +96,7 @@ pub fn resolveSymbols(self: *ZigModule, elf_file: *Elf) void {
         if (self.asFile().symbolRank(esym, false) < global.symbolRank(elf_file)) {
             const atom_index = switch (esym.st_shndx) {
                 elf.SHN_ABS, elf.SHN_COMMON => 0,
-                else => esym.st_shndx,
+                else => self.atoms.items[esym.st_shndx],
             };
             const output_section_index = if (elf_file.atom(atom_index)) |atom|
                 atom.outputShndx().?
@@ -141,7 +142,7 @@ pub fn claimUnresolved(self: *ZigModule, elf_file: *Elf) void {
 }
 
 pub fn scanRelocs(self: *ZigModule, elf_file: *Elf, undefs: anytype) !void {
-    for (self.atoms.keys()) |atom_index| {
+    for (self.atoms.items) |atom_index| {
         const atom = elf_file.atom(atom_index) orelse continue;
         if (!atom.flags.alive) continue;
         if (try atom.scanRelocsRequiresCode(elf_file)) {
@@ -324,7 +325,7 @@ fn formatAtoms(
     _ = unused_fmt_string;
     _ = options;
     try writer.writeAll("  atoms\n");
-    for (ctx.self.atoms.keys()) |atom_index| {
+    for (ctx.self.atoms.items) |atom_index| {
         const atom = ctx.elf_file.atom(atom_index) orelse continue;
         try writer.print("    {}\n", .{atom.fmt(ctx.elf_file)});
     }

src/link/Elf/file.zig

@@ -92,7 +92,7 @@ pub const File = union(enum) {
     pub fn atoms(file: File) []const Atom.Index {
         return switch (file) {
             .linker_defined => unreachable,
-            .zig_module => |x| x.atoms.keys(),
+            .zig_module => |x| x.atoms.items,
             .object => |x| x.atoms.items,
         };
     }