From: Andi Kleen
Date: Wed Mar 28 2012 - 14:51:52 EST

From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

Add a config option to disable various gcc compiler optimizations that
make assembler listings much harder to read. This is everything that reorders
code significantly or creates partial functions.

This is mainly to keep kernel hackers sane.

Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Makefile | 10 ++++++++++
lib/Kconfig.debug | 9 +++++++++
2 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/Makefile b/Makefile
index 1932984..6f7328b 100644
--- a/Makefile
+++ b/Makefile
@@ -564,6 +564,16 @@ else

+# Disable optimizations that make assembler listings hard to read.
+# reorder blocks reorders the control in the function
+# ipa clone creates specialized cloned functions
+# partial inlining inlines only parts of functions
+KBUILD_CFLAGS += $(call cc-option,-fno-reorder-blocks,) \
+ $(call cc-option,-fno-ipa-cp-clone,) \
+ $(call cc-option,-fno-partial-inlining)
include $(srctree)/arch/$(SRCARCH)/Makefile

ifneq ($(CONFIG_FRAME_WARN),0)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index f7af95d..d6102f3 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -70,6 +70,15 @@ config STRIP_ASM_SYMS
that look like '.Lxxx') so they don't pollute the output of
get_wchan() and suchlike.

+ bool "Generate readable assembler code"
+ depends on DEBUG_KERNEL
+ help
+ Disable some compiler optimizations that tend to generate human unreadable
+ assembler output. This may make the kernel slightly slower, but it helps
+ to keep kernel developers who have to stare a lot at assembler listings
+ sane.
bool "Enable unused/obsolete exported symbols"
default y if X86

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