From 28189b0fa5be6b56d1d9961b4e432ac7c16a80de Mon Sep 17 00:00:00 2001
From: Jonathan Marler <johnnymarler@gmail.com>
Date: Fri, 27 Sep 2024 09:35:16 -0600
Subject: [PATCH] build: move dependency cache into Graph

The dependency cache is shared amongst all Build objects. This is currently
done by allocating a single instance and storing a reference to it in each
Build object.  However, the Graph object already exists to host shared
state so by moving it there we reuse the same pattern for shared state
and avoid an extra object on the heap.
---
 lib/compiler/build_runner.zig |  1 +
 lib/std/Build.zig             | 14 ++++----------
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/lib/compiler/build_runner.zig b/lib/compiler/build_runner.zig
index 4d643222d7..f29b9e6c42 100644
--- a/lib/compiler/build_runner.zig
+++ b/lib/compiler/build_runner.zig
@@ -80,6 +80,7 @@ pub fn main() !void {
             .query = .{},
             .result = try std.zig.system.resolveTargetQuery(.{}),
         },
+        .dependency_cache = std.Build.InitializedDepMap.initContext(arena, .{ .allocator = arena }),
     };
 
     graph.cache.addPrefix(.{ .path = null, .handle = std.fs.cwd() });
diff --git a/lib/std/Build.zig b/lib/std/Build.zig
index dbd96441b1..fd734dd617 100644
--- a/lib/std/Build.zig
+++ b/lib/std/Build.zig
@@ -90,9 +90,6 @@ modules: std.StringArrayHashMap(*Module),
 
 named_writefiles: std.StringArrayHashMap(*Step.WriteFile),
 named_lazy_paths: std.StringArrayHashMap(LazyPath),
-/// A map from build root dirs to the corresponding `*Dependency`. This is shared with all child
-/// `Build`s.
-initialized_deps: *InitializedDepMap,
 /// The hash of this instance's package. `""` means that this is the root package.
 pkg_hash: []const u8,
 /// A mapping from dependency names to package hashes.
@@ -125,6 +122,7 @@ pub const Graph = struct {
     host: ResolvedTarget,
     incremental: ?bool = null,
     random_seed: u32 = 0,
+    dependency_cache: InitializedDepMap,
 };
 
 const AvailableDeps = []const struct { []const u8, []const u8 };
@@ -144,7 +142,7 @@ const SystemLibraryMode = enum {
     declared_enabled,
 };
 
-const InitializedDepMap = std.HashMap(InitializedDepKey, *Dependency, InitializedDepContext, std.hash_map.default_max_load_percentage);
+pub const InitializedDepMap = std.HashMap(InitializedDepKey, *Dependency, InitializedDepContext, std.hash_map.default_max_load_percentage);
 const InitializedDepKey = struct {
     build_root_string: []const u8,
     user_input_options: UserInputOptionsMap,
@@ -252,8 +250,6 @@ pub fn create(
     available_deps: AvailableDeps,
 ) !*Build {
     const arena = graph.arena;
-    const initialized_deps = try arena.create(InitializedDepMap);
-    initialized_deps.* = InitializedDepMap.initContext(arena, .{ .allocator = arena });
 
     const b = try arena.create(Build);
     b.* = .{
@@ -304,7 +300,6 @@ pub fn create(
         .modules = .init(arena),
         .named_writefiles = .init(arena),
         .named_lazy_paths = .init(arena),
-        .initialized_deps = initialized_deps,
         .pkg_hash = "",
         .available_deps = available_deps,
         .release_mode = .off,
@@ -398,7 +393,6 @@ fn createChildOnly(
         .modules = .init(allocator),
         .named_writefiles = .init(allocator),
         .named_lazy_paths = .init(allocator),
-        .initialized_deps = parent.initialized_deps,
         .pkg_hash = pkg_hash,
         .available_deps = pkg_deps,
         .release_mode = parent.release_mode,
@@ -2127,7 +2121,7 @@ fn dependencyInner(
     args: anytype,
 ) *Dependency {
     const user_input_options = userInputOptionsFromArgs(b.allocator, args);
-    if (b.initialized_deps.get(.{
+    if (b.graph.dependency_cache.get(.{
         .build_root_string = build_root_string,
         .user_input_options = user_input_options,
     })) |dep|
@@ -2155,7 +2149,7 @@ fn dependencyInner(
     const dep = b.allocator.create(Dependency) catch @panic("OOM");
     dep.* = .{ .builder = sub_builder };
 
-    b.initialized_deps.put(.{
+    b.graph.dependency_cache.put(.{
         .build_root_string = build_root_string,
         .user_input_options = user_input_options,
     }, dep) catch @panic("OOM");