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Subject[RFC PATCH] kbuild: Add an option to enable -O1 and speed-up compilation time
Date
Add a new compilation option which speeds-up compilation time.
This can be useful when using static checker such as smatch or build-bots.
In such cases, the speed and quality of the generated code is not
important.

Using -O0 would be even better, but unfortunately, building fails with
this option.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
Makefile | 5 ++++-
init/Kconfig | 8 ++++++++
2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 1f8bef92868f..14467386f947 100644
--- a/Makefile
+++ b/Makefile
@@ -817,7 +817,10 @@ KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation)
KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)

-ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
+ifdef CONFIG_CC_OPTIMIZE_FOR_COMPILATION_SPEED
+KBUILD_CFLAGS += -O1
+KBUILD_RUSTFLAGS_OPT_LEVEL_MAP := 1
+else ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
KBUILD_CFLAGS += -O2
KBUILD_RUSTFLAGS_OPT_LEVEL_MAP := 2
else ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3
diff --git a/init/Kconfig b/init/Kconfig
index a96776a9b080..3177a1830c9a 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1384,6 +1384,14 @@ choice
prompt "Compiler optimization level"
default CC_OPTIMIZE_FOR_PERFORMANCE

+config CC_OPTIMIZE_FOR_COMPILATION_SPEED
+ bool "Optimize for compilation speed (-O1)"
+ help
+ This option can be useful when running a static checker such as smatch
+ or a build-bot.
+ Compilation time is slighly faster than -O2 and it requires less
+ memory.
+
config CC_OPTIMIZE_FOR_PERFORMANCE
bool "Optimize for performance (-O2)"
help
--
2.34.1
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