InternPool: Rework the way strings are represented

src/Air.zig

@@ -1249,8 +1249,9 @@ pub const Inst = struct {
         // bigger than expected. Note that in safety builds, Zig is allowed
         // to insert a secret field for safety checks.
         comptime {
-            if (!std.debug.runtime_safety) {
-                assert(@sizeOf(Data) == 8);
+            switch (builtin.mode) {
+                .Debug, .ReleaseSafe => {},
+                .ReleaseFast, .ReleaseSmall => assert(@sizeOf(Data) == 8),
             }
         }
     };

src/Compilation.zig

@@ -3684,7 +3684,9 @@ const Header = extern struct {
             items_len: u32,
             extra_len: u32,
             limbs_len: u32,
-            string_bytes_len: u32,
+            large_strings_len: u32,
+            large_string_bytes_len: u32,
+            small_string_bytes_len: u32,
             tracked_insts_len: u32,
             files_len: u32,
         },
@@ -3732,7 +3734,9 @@ pub fn saveState(comp: *Compilation) !void {
                 .items_len = @intCast(local.mutate.items.len),
                 .extra_len = @intCast(local.mutate.extra.len),
                 .limbs_len = @intCast(local.mutate.limbs.len),
-                .string_bytes_len = @intCast(local.mutate.strings.len),
+                .large_strings_len = @intCast(local.mutate.large_strings.len),
+                .large_string_bytes_len = @intCast(local.mutate.large_string_bytes.len),
+                .small_string_bytes_len = @intCast(local.mutate.small_string_bytes.len),
                 .tracked_insts_len = @intCast(local.mutate.tracked_insts.len),
                 .files_len = @intCast(local.mutate.files.len),
             },
@@ -3775,8 +3779,15 @@ pub fn saveState(comp: *Compilation) !void {
                 addBuf(&bufs, @ptrCast(local.shared.items.view().items(.data)[0..pt_header.intern_pool.items_len]));
                 addBuf(&bufs, @ptrCast(local.shared.items.view().items(.tag)[0..pt_header.intern_pool.items_len]));
             }
-            if (pt_header.intern_pool.string_bytes_len > 0) {
-                addBuf(&bufs, local.shared.strings.view().items(.@"0")[0..pt_header.intern_pool.string_bytes_len]);
+            if (pt_header.intern_pool.large_strings_len > 0) {
+                addBuf(&bufs, @ptrCast(local.shared.large_strings.view().items(.offset)[0..pt_header.intern_pool.large_strings_len]));
+                addBuf(&bufs, @ptrCast(local.shared.large_strings.view().items(.len)[0..pt_header.intern_pool.large_strings_len]));
+            }
+            if (pt_header.intern_pool.large_string_bytes_len > 0) {
+                addBuf(&bufs, local.shared.large_string_bytes.view().items(.@"0")[0..pt_header.intern_pool.large_string_bytes_len]);
+            }
+            if (pt_header.intern_pool.small_string_bytes_len > 0) {
+                addBuf(&bufs, local.shared.small_string_bytes.view().items(.@"0")[0..pt_header.intern_pool.small_string_bytes_len]);
             }
             if (pt_header.intern_pool.tracked_insts_len > 0) {
                 addBuf(&bufs, @ptrCast(local.shared.tracked_insts.view().items(.@"0")[0..pt_header.intern_pool.tracked_insts_len]));