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authorMarek BehĂșn <marek.behun@nic.cz>2021-05-20 13:24:03 +0200
committerTom Rini <trini@konsulko.com>2021-05-24 14:21:30 -0400
commitc1094987d1dc4701646c5f3aa254e7a92a02d305 (patch)
tree5d2bbcee39b8adff66ac767d8bde1bcb6283dfe7 /Kconfig
parent958f2e57eff72b5156f7b08b9c1415fb7e12833d (diff)
downloadu-boot-c1094987d1dc4701646c5f3aa254e7a92a02d305.tar.gz
build: support building with Link Time Optimizations
Add plumbing for building U-Boot with Link Time Optimizations. When building with LTO, $(PLATFORM_LIBS) has to be in --whole-archive / --no-whole-archive group, otherwise some functions declared in assembly may not be resolved and linking may fail. Note: clang may throw away linker list symbols it thinks are unused when compiling with LTO. To force these symbols to be included, we refer to them via the __ADDRESSABLE macro in a C file generated from compiled built-in.o files before linking. Signed-off-by: Marek BehĂșn <marek.behun@nic.cz> Reviewed-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'Kconfig')
-rw-r--r--Kconfig24
1 files changed, 24 insertions, 0 deletions
diff --git a/Kconfig b/Kconfig
index 86f0a39bb0..f8c1a77bed 100644
--- a/Kconfig
+++ b/Kconfig
@@ -85,6 +85,30 @@ config SPL_OPTIMIZE_INLINING
do what it thinks is best, which is desirable in some cases for size
reasons.
+config ARCH_SUPPORTS_LTO
+ bool
+
+config LTO
+ bool "Enable Link Time Optimizations"
+ depends on ARCH_SUPPORTS_LTO
+ default n
+ help
+ This option enables Link Time Optimization (LTO), a mechanism which
+ allows the compiler to optimize between different compilation units.
+
+ This can optimize away dead code paths, resulting in smaller binary
+ size (if CC_OPTIMIZE_FOR_SIZE is enabled).
+
+ This option is not available for every architecture and may
+ introduce bugs.
+
+ Currently, when compiling with GCC, due to a weird bug regarding
+ jobserver, the final linking will not respect make's --jobs argument.
+ Instead all available processors will be used (as reported by the
+ nproc command).
+
+ If unsure, say n.
+
config TPL_OPTIMIZE_INLINING
bool "Allow compiler to uninline functions marked 'inline' in TPL"
depends on TPL