From 19bbf83e47e4f98a45fe1c735dd2cdab80b99eca Mon Sep 17 00:00:00 2001
From: David Sherret <dsherret@users.noreply.github.com>
Date: Mon, 18 Nov 2024 15:44:17 -0500
Subject: [PATCH] perf(windows): delay load webgpu and some other dlls (#26917)

Before: ~100ms, After: ~40ms for a hello world

Closes https://github.com/denoland/deno/issues/26914
---
 cli/build.rs | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/cli/build.rs b/cli/build.rs
index 2678a8dbb0..3d98661284 100644
--- a/cli/build.rs
+++ b/cli/build.rs
@@ -400,6 +400,24 @@ fn main() {
   println!("cargo:rustc-env=TARGET={}", env::var("TARGET").unwrap());
   println!("cargo:rustc-env=PROFILE={}", env::var("PROFILE").unwrap());
 
+  if cfg!(windows) {
+    // these dls load slowly, so delay loading them
+    let dlls = [
+      // webgpu
+      "d3dcompiler_47",
+      "OPENGL32",
+      // network related functions
+      "iphlpapi",
+    ];
+    for dll in dlls {
+      println!("cargo:rustc-link-arg-bin=deno=/delayload:{dll}.dll");
+      println!("cargo:rustc-link-arg-bin=denort=/delayload:{dll}.dll");
+    }
+    // enable delay loading
+    println!("cargo:rustc-link-arg-bin=deno=delayimp.lib");
+    println!("cargo:rustc-link-arg-bin=denort=delayimp.lib");
+  }
+
   let c = PathBuf::from(env::var_os("CARGO_MANIFEST_DIR").unwrap());
   let o = PathBuf::from(env::var_os("OUT_DIR").unwrap());