From c7a6f9bc31c026c5e4adcd1691f88daca4374358 Mon Sep 17 00:00:00 2001
From: Yuta Saito <kateinoigakukun@gmail.com>
Date: Sun, 13 Oct 2024 16:58:36 +0900
Subject: [PATCH] CMake: Enable WMO for Release builds

The new interpreter heavily benefits from WMO and it's even slower than
the old one without it. This change enables WMO for Release builds for
CMake builds as it's not enabled by default.

Use `CMAKE_Swift_COMPILATION_MODE` if CMake 3.29 or newer is used, and
fall back to `add_compile_options` if older.
https://cmake.org/cmake/help/latest/prop_tgt/Swift_COMPILATION_MODE.html
---
 CMakeLists.txt | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 470d8254..19eecd80 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,6 +7,13 @@ project(WasmKit LANGUAGES C Swift)
 set(SWIFT_VERSION 5)
 set(CMAKE_Swift_LANGUAGE_VERSION ${SWIFT_VERSION})
 
+# Enable whole module optimization for Release or RelWithDebInfo builds.
+if(POLICY CMP0157)
+  set(CMAKE_Swift_COMPILATION_MODE $<IF:$<CONFIG:Release,RelWithDebInfo>,wholemodule,incremental>)
+else()
+  add_compile_options($<$<AND:$<COMPILE_LANGUAGE:Swift>,$<CONFIG:Release,RelWithDebInfo>>:-wmo>)
+endif()
+
 if(CMAKE_VERSION VERSION_LESS 3.21)
   get_property(parent_dir DIRECTORY PROPERTY PARENT_DIRECTORY)
   if(NOT parent_dir)