From 8afde59054a6ceb214ec8b792f2e49f38ea3da52 Mon Sep 17 00:00:00 2001
From: Johan Walles <johan.walles@gmail.com>
Date: Mon, 21 Apr 2025 10:56:36 +0200
Subject: [PATCH] macOS: Default to modern linker on x64

This patch changes the default macOS x64 linker from the slower legacy
"classic" linker, to the much faster default modern macOS linker. A new
CMake option `WITH_LEGACY_MACOS_X64_LINKER` was also introduced to use
the old linker, set to OFF by default.

As an example from testing on an Intel Macbook, this makes linking time
go from 3min25s to 10s after this change. The reason why the legacy
linker was enforced on x64 in the first place was to silence "platform
load command not found" warnings during linking. Since this behavior is
still desired on the BuildBot, the `WITH_LEGACY_MACOS_X64_LINKER` option
is enforced in the BuildBot macOS configs.

Pull Request: https://projects.blender.org/blender/blender/pulls/134639
---
 CMakeLists.txt                                  | 4 ++++
 build_files/buildbot/config/blender_macos.cmake | 1 +
 build_files/cmake/platform/platform_apple.cmake | 4 +++-
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9169806f810..e6063ac431b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1259,6 +1259,10 @@ if(APPLE)
   include(platform_apple_xcode)
 endif()
 
+if(APPLE)
+  option(WITH_LEGACY_MACOS_X64_LINKER "Use legacy macOS linker. Only on x64 platform. Minutes slower, but emits fewer warnings." OFF)
+  mark_as_advanced(WITH_LEGACY_MACOS_X64_LINKER)
+endif()
 
 # -----------------------------------------------------------------------------
 # Check for Conflicting/Unsupported Configurations
diff --git a/build_files/buildbot/config/blender_macos.cmake b/build_files/buildbot/config/blender_macos.cmake
index cb8d173151e..27a76ed82a5 100644
--- a/build_files/buildbot/config/blender_macos.cmake
+++ b/build_files/buildbot/config/blender_macos.cmake
@@ -5,3 +5,4 @@
 include("${CMAKE_CURRENT_LIST_DIR}/../../cmake/config/blender_release.cmake")
 
 set(WITH_CYCLES_TEST_OSL     ON CACHE BOOL "" FORCE)
+set(WITH_LEGACY_MACOS_X64_LINKER ON CACHE BOOL "" FORCE)
diff --git a/build_files/cmake/platform/platform_apple.cmake b/build_files/cmake/platform/platform_apple.cmake
index 8354d88a5c7..8c4fdc379d2 100644
--- a/build_files/cmake/platform/platform_apple.cmake
+++ b/build_files/cmake/platform/platform_apple.cmake
@@ -427,8 +427,10 @@ string(APPEND PLATFORM_LINKFLAGS
 )
 
 if(${XCODE_VERSION} VERSION_GREATER_EQUAL 15.0)
-  if("${CMAKE_OSX_ARCHITECTURES}" STREQUAL "x86_64")
+  if("${CMAKE_OSX_ARCHITECTURES}" STREQUAL "x86_64" AND WITH_LEGACY_MACOS_X64_LINKER)
     # Silence "no platform load command found in <static library>, assuming: macOS".
+    #
+    # NOTE: Using ld_classic costs minutes of extra linking time.
     string(APPEND PLATFORM_LINKFLAGS " -Wl,-ld_classic")
   else()
     # Silence "ld: warning: ignoring duplicate libraries".