From ce8ceaa952524180b4bce0a0cd6a3556b59dfa8e Mon Sep 17 00:00:00 2001
From: Jeremy Schonfeld <1004103+jmschonfeld@users.noreply.github.com>
Date: Fri, 9 Aug 2024 14:54:26 -0700
Subject: [PATCH] Enable WMO (#832)

* Enable whole-module-optimization in release builds

* Address feedback

* Fix build failures

* Don't enable WMO on Windows
---
 CMakeLists.txt | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b99fcfa8f..fd8e463de 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -35,6 +35,16 @@ if(NOT SWIFT_SYSTEM_NAME)
   endif()
 endif()
 
+# Don't enable WMO on Windows due to linker failures
+if(NOT CMAKE_SYSTEM_NAME STREQUAL Windows)
+    # Enable whole module optimization for release builds & incremental for debug builds
+    if(POLICY CMP0157)
+        set(CMAKE_Swift_COMPILATION_MODE "$<IF:$<CONFIG:Release>,wholemodule,incremental>")
+    else()
+        add_compile_options($<$<AND:$<COMPILE_LANGUAGE:Swift>,$<CONFIG:Release>>:-wmo>)
+    endif()
+endif()
+
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)