Subject: [PATCH 4/4] Add option to use -fno-semantic-interposition and
 -fdevirtualize-at-ltrans

For the final linking process.

This can be used in tandem with LTO_CP_CLONE/-fipa-cp-clone.

Do note: while -fipa-cp-clone is enabled by default at -O3,
only LTO_CP_CLONE will append -fipa-cp-clone to LTO_FINAL_CFLAGS
---
 init/Kconfig         | 8 ++++++++
 scripts/Makefile.lto | 6 +++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/init/Kconfig b/init/Kconfig
index 26d7ae4a2..acb9afa0f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1427,6 +1427,14 @@ config SINGLE_LINK
 	  Use only a single linking step for the final vmlinux, making
 	  the build slightly faster.
 
+config LTO_AGGRESSIVE
+	bool "Use aggressive optimizations for LTO"
+	depends on LTO
+	help
+	  Flags -fno-semantic-interposition and -fdevirtualize-at-ltrans
+	  are enabled for greater optimization at the expense of poorer
+	  debugging and increased linking time + memory needs.
+
 config SYSCTL
 	bool
 
diff --git a/scripts/Makefile.lto b/scripts/Makefile.lto
index e41be559d..70b7558a2 100644
--- a/scripts/Makefile.lto
+++ b/scripts/Makefile.lto
@@ -13,7 +13,7 @@ export KBUILD_MOD_LDFLAGS
 export KBUILD_MODPOST_LDFLAGS
 
 ifdef CONFIG_LTO
-	LTO_CFLAGS := -flto
+	LTO_CFLAGS := -flto -flto-compression-level=9
 	LTO_FINAL_CFLAGS := -fuse-linker-plugin
 
 	# gcc 8.x doesn't generate debuginfo if we don't
@@ -47,6 +47,10 @@ ifdef CONFIG_LTO_CP_CLONE
 	LTO_FINAL_CFLAGS += -fipa-cp-clone
 endif
 
+ifdef CONFIG_LTO_AGGRESSIVE
+	LTO_FINAL_CFLAGS += -fno-semantic-interposition -fdevirtualize-at-ltrans
+endif
+
 	# allow extra flags from command line
 	LTO_FINAL_CFLAGS += ${LTO_EXTRA_CFLAGS}
 
-- 
2.28.0