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Subject[PATCH] kbuild: llvmlinux: Set appropriate compiler-flag for CONFIG_CC_OPTIMIZE_FOR_SIZE
Date
Based on a patch of Behan Webster (see [1]).

CLANG (here: v3.7) requires '-Oz' as OptLevel to be set.

A Linux v4.3-rc1 kernel built fine with CONFIG_CC_OPTIMIZE_FOR_SIZE=y
and boots on bare metal.
This is a Ubuntu/precise AMD64 system.

Tested against Linux v4.3-rc1 and a refreshed llvmlinux patchset.

[1] http://git.linuxfoundation.org/?p=llvmlinux.git;a=blob;f=arch/all/patches/smaller.patch

CC: Behan Webster <behanw@converseincode.com>
---
Makefile | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 4249441e535d..a57fb6b39ed7 100644
--- a/Makefile
+++ b/Makefile
@@ -622,7 +622,8 @@ KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks,)
endif

ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
-KBUILD_CFLAGS += -Os $(call cc-disable-warning,maybe-uninitialized,)
+KBUILD_CFLAGS += $(call cc-option,-Oz,-Os)
+KBUILD_CFLAGS += $(call cc-disable-warning,maybe-uninitialized,)
else
KBUILD_CFLAGS += -O2
endif
--
2.5.2


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