elf: do not re-allocate AtomLists unless dirtied

src/link/Elf.zig

@@ -3586,19 +3586,23 @@ fn updateSectionSizes(self: *Elf) !void {
     const slice = self.sections.slice();
     for (slice.items(.shdr), slice.items(.atom_list_2)) |shdr, *atom_list| {
         if (atom_list.atoms.keys().len == 0) continue;
+        if (!atom_list.dirty) continue;
         if (self.requiresThunks() and shdr.sh_flags & elf.SHF_EXECINSTR != 0) continue;
         atom_list.updateSize(self);
         try atom_list.allocate(self);
+        atom_list.dirty = false;
     }
 
     if (self.requiresThunks()) {
         for (slice.items(.shdr), slice.items(.atom_list_2)) |shdr, *atom_list| {
             if (shdr.sh_flags & elf.SHF_EXECINSTR == 0) continue;
             if (atom_list.atoms.keys().len == 0) continue;
+            if (!atom_list.dirty) continue;
 
             // Create jump/branch range extenders if needed.
             try self.createThunks(atom_list);
             try atom_list.allocate(self);
+            atom_list.dirty = false;
         }
 
         // FIXME:JK this will hopefully not be needed once we create a link from Atom/Thunk to AtomList.

src/link/Elf/AtomList.zig

@@ -5,6 +5,8 @@ output_section_index: u32 = 0,
 // atoms: std.ArrayListUnmanaged(Elf.Ref) = .empty,
 atoms: std.AutoArrayHashMapUnmanaged(Elf.Ref, void) = .empty,
 
+dirty: bool = true,
+
 pub fn deinit(list: *AtomList, allocator: Allocator) void {
     list.atoms.deinit(allocator);
 }
@@ -20,9 +22,7 @@ pub fn offset(list: AtomList, elf_file: *Elf) u64 {
 }
 
 pub fn updateSize(list: *AtomList, elf_file: *Elf) void {
-    // TODO perhaps a 'stale' flag would be better here?
-    list.size = 0;
-    list.alignment = .@"1";
+    assert(list.dirty);
     for (list.atoms.keys()) |ref| {
         const atom_ptr = elf_file.atom(ref).?;
         assert(atom_ptr.alive);
@@ -35,6 +35,8 @@ pub fn updateSize(list: *AtomList, elf_file: *Elf) void {
 }
 
 pub fn allocate(list: *AtomList, elf_file: *Elf) !void {
+    assert(list.dirty);
+
     const alloc_res = try elf_file.allocateChunk(.{
         .shndx = list.output_section_index,
         .size = list.size,
@@ -43,6 +45,8 @@ pub fn allocate(list: *AtomList, elf_file: *Elf) !void {
     });
     list.value = @intCast(alloc_res.value);
 
+    log.debug("allocated atom_list({d}) at 0x{x}", .{ list.output_section_index, list.address(elf_file) });
+
     const slice = elf_file.sections.slice();
     const shdr = &slice.items(.shdr)[list.output_section_index];
     const last_atom_ref = &slice.items(.last_atom)[list.output_section_index];
@@ -80,12 +84,15 @@ pub fn allocate(list: *AtomList, elf_file: *Elf) !void {
         atom_ptr.output_section_index = list.output_section_index;
         atom_ptr.value += list.value;
     }
+
+    list.dirty = false;
 }
 
 pub fn write(list: AtomList, buffer: *std.ArrayList(u8), undefs: anytype, elf_file: *Elf) !void {
     const gpa = elf_file.base.comp.gpa;
     const osec = elf_file.sections.items(.shdr)[list.output_section_index];
     assert(osec.sh_type != elf.SHT_NOBITS);
+    assert(!list.dirty);
 
     log.debug("writing atoms in section '{s}'", .{elf_file.getShString(osec.sh_name)});
 

src/link/Elf/relocatable.zig

@@ -336,8 +336,10 @@ fn updateSectionSizes(elf_file: *Elf) !void {
     const slice = elf_file.sections.slice();
     for (slice.items(.atom_list_2)) |*atom_list| {
         if (atom_list.atoms.keys().len == 0) continue;
+        if (!atom_list.dirty) continue;
         atom_list.updateSize(elf_file);
         try atom_list.allocate(elf_file);
+        atom_list.dirty = false;
     }
 
     for (slice.items(.shdr), 0..) |*shdr, shndx| {