On Wed, Oct 27, 2021 at 02:21:17PM +0200, Heinrich Schuchardt wrote:
On 10/27/21 10:50, Ilias Apalodimas wrote:
Hi Simon
How does this patch related to the standard boot series? Shouldn't this be a completely separate patch?
Thanks /Ilias
On Sun, 24 Oct 2021 at 02:26, Simon Glass sjg@chromium.org wrote:
LTO (Link-Time Optimisation) is an very useful feature which can significantly reduce the size of U-Boot binaries. So far it has been made available for selected ARM boards and sandbox.
However, incremental builds are much slower when LTO is used. For example, an incremental build of sandbox takes 2.1 seconds on my machine, but 6.7 seconds with LTO enabled.
Add a LTO_BUILD=n parameter to the build, so it can be disabled during development if needed, for faster builds.
Add some documentation about LTO while we are here.
Signed-off-by: Simon Glass sjg@chromium.org
(no changes since v1)
Makefile | 18 +++++++++++++----- arch/arm/config.mk | 4 ++-- arch/arm/include/asm/global_data.h | 2 +- doc/build/gcc.rst | 17 +++++++++++++++++ 4 files changed, 33 insertions(+), 8 deletions(-)
diff --git a/Makefile b/Makefile index b79b2319ff6..7057723e046 100644 --- a/Makefile +++ b/Makefile @@ -434,6 +434,9 @@ KBUILD_CFLAGS += -fshort-wchar -fno-strict-aliasing KBUILD_AFLAGS := -D__ASSEMBLY__ KBUILD_LDFLAGS :=
+# Set this to "n" use of LTO for this build, e.g. LTO_BUILD=n +LTO_BUILD ?= y
This does not allow LTO_BUILD=y to enable LTO for CONFIG_LTO=n.
I don't understand why we need this patch at all. If you want to disable LTO, disable LTO. Yes, LTO makes linking take longer which can be annoying on iterative development. I have a few different "HACK: DO NOT PUSH: ..." things I git am at the start of a branch, depending on needs. You can just do that to drop "imply LTO" from the SANDBOX stanza in arch/Kconfig. We do not need a whole thing around a CONFIG option that can be disabled in the defconfig, or local .config file even.