From 83e9513623f48943755918302a737f4e10e951e3 Mon Sep 17 00:00:00 2001
From: TellowKrinkle <tellowkrinkle@gmail.com>
Date: Wed, 1 Sep 2021 22:32:14 -0500
Subject: [PATCH] CMake: Add option for partial LTO

---
 cmake/BuildParameters.cmake |  1 +
 pcsx2/CMakeLists.txt        | 25 +++++++++++++++++++------
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/cmake/BuildParameters.cmake b/cmake/BuildParameters.cmake
index 05e6f1661e..0771bbddb3 100644
--- a/cmake/BuildParameters.cmake
+++ b/cmake/BuildParameters.cmake
@@ -18,6 +18,7 @@ set(PCSX2_DEFS "")
 option(DISABLE_BUILD_DATE "Disable including the binary compile date")
 option(ENABLE_TESTS "Enables building the unit tests" ON)
 option(USE_SYSTEM_YAML "Uses a system version of yaml, if found")
+option(LTO_PCSX2_CORE "Enable LTO/IPO/LTCG on the subset of pcsx2 that benefits most from it but not anything else")
 
 if(WIN32)
 	set(DEFAULT_NATIVE_TOOLS ON)
diff --git a/pcsx2/CMakeLists.txt b/pcsx2/CMakeLists.txt
index 272df33a4a..e3f9715bf1 100644
--- a/pcsx2/CMakeLists.txt
+++ b/pcsx2/CMakeLists.txt
@@ -1364,10 +1364,27 @@ set(pcsx2x86Headers
 	x86/R5900_Profiler.h
 	)
 
-# common Sources
-target_sources(PCSX2 PRIVATE
+# These ones benefit a lot from LTO
+set(pcsx2LTOSources
 	${pcsx2Sources}
 	${pcsx2Headers}
+	${pcsx2IPUSources}
+	${pcsx2IPUHeaders}
+	${pcsx2x86Sources}
+	${pcsx2x86Headers}
+)
+
+if(LTO_PCSX2_CORE)
+	add_library(PCSX2_LTO ${pcsx2LTOSources})
+	target_link_libraries(PCSX2_LTO PRIVATE PCSX2_FLAGS)
+	target_link_libraries(PCSX2 PRIVATE PCSX2_LTO)
+	set_target_properties(PCSX2_LTO PROPERTIES INTERPROCEDURAL_OPTIMIZATION true)
+else()
+	target_sources(PCSX2 PRIVATE ${pcsx2LTOSources})
+endif()
+
+# common Sources
+target_sources(PCSX2 PRIVATE
 	${pcsx2CDVDSources}
 	${pcsx2CDVDHeaders}
 	${pcsx2SPU2Sources}
@@ -1383,8 +1400,6 @@ target_sources(PCSX2 PRIVATE
 	${pcsx2GuiSources}
 	${pcsx2GuiResources}
 	${pcsx2GuiHeaders}
-	${pcsx2IPUSources}
-	${pcsx2IPUHeaders}
 	${pcsx2ps2Sources}
 	${pcsx2ps2Headers}
 	${pcsx2RecordingSources}
@@ -1394,8 +1409,6 @@ target_sources(PCSX2 PRIVATE
 	${pcsx2SystemHeaders}
 	${pcsx2UtilitiesSources}
 	${pcsx2UtilitiesHeaders}
-	${pcsx2x86Sources}
-	${pcsx2x86Headers}
 	${pcsx2ZipToolsSources}
 	${pcsx2ZipToolsHeaders})