On Tue, Jul 10, 2012 at 11:04:50AM -0700, Allen Martin wrote:
On Tue, Jul 10, 2012 at 10:50:34AM -0700, Tom Rini wrote:
On Tue, Jul 10, 2012 at 10:44:33AM -0700, Allen Martin wrote:
On Tue, Jul 10, 2012 at 10:25:05AM -0700, Tom Rini wrote:
- PGP Signed by an unknown key
On Tue, Jul 10, 2012 at 10:00:17AM -0700, Allen Martin wrote:
Disable sibling call optimization based on binutils version. This is to work around a bug in the assember in binutils versions < 2.22. Branches to weak symbols can be incorrectly optimized in thumb mode to a short branch (b.n instruction) that won't reach when the symbol gets preempted.
http://sourceware.org/bugzilla/show_bug.cgi?id=12532
Signed-off-by: Allen Martin amartin@nvidia.com
changes for v2: -changed GAS_BUG_12532 from yes/no to y/n to be consistent
-added additional warning about code size increase
arch/arm/config.mk | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)
diff --git a/arch/arm/config.mk b/arch/arm/config.mk index 3f4453a..bcabf17 100644 --- a/arch/arm/config.mk +++ b/arch/arm/config.mk @@ -87,3 +87,24 @@ endif ifndef CONFIG_NAND_SPL LDFLAGS_u-boot += -pie endif
+# +# binutils versions < 2.22 have a bug in the assembler where branches +# to weak symbols can be incorrectly optimized in thumb mode to a +# short branch (b.n instruction) that won't reach when the symbol +# gets preempted +# +# http://sourceware.org/bugzilla/show_bug.cgi?id=12532 +# +ifeq ($(CONFIG_SYS_THUMB_BUILD),y) +ifeq ($(GAS_BUG_12532),) +export GAS_BUG_12532:=$(shell if [ $(call binutils-version) -lt 0222 ] ; then echo y; else echo n; fi)
Please don't squash out whitespace, just break this out into a multi-line test ala the others in the toplevel config.mk.
Ok
+ifeq ($(GAS_BUG_12532),y) +$(warning *** disabling sibling call optimzation because binutils version < 2.22) +$(warning *** code size may be slightly larger) +endif +endif +ifeq ($(GAS_BUG_12532),y) +PLATFORM_RELFLAGS += -fno-optimize-sibling-calls +endif +endif
This seems a bit longer than needed. Just check that it's y once and do both things. Also, I _think_ we should be able to squish this down to: ifeq ($(CONFIG_SYS_THUMB_BUILD),y) GAS_BUG_12532 := $(shell if [ $(call binutils-version) -lt 0222 ] ; \ then echo y; else echo n; fi) ifeq ($(GAS_BUG_125320),y) $(warning ...) $(warning ...) PLATFORM_RELFLAGS += ... endif endif
But I haven't tested it.
I wrote it the way I did because I only want the expensive shell/binutils-version to get evaluated once per "make". I think what you proposed would cause it to get re-evaluated every time the build goes down into a subdir.
It should still get evaluated once, I think. Kluding the binutils-version script to echo 1 >> /tmp/test every time it's run would tell tho for sure :)
I tried it out, it's obvious from the $(warning) it's getting reevaluated:
$ ./MAKEALL -s tegra20 /home/arm/u-boot/arch/arm/config.mk:102: *** disabling sibling call optimzation because binutils version < 2.22 /home/arm/u-boot/arch/arm/config.mk:103: *** code size may be slightly larger Configuring for harmony board... text data bss dec hex filename 170334 4284 278352 452970 6e96a ./u-boot 11676 161 36 11873 2e61 ./spl/u-boot-spl /home/arm/u-boot/arch/arm/config.mk:102: *** disabling sibling call optimzation because binutils version < 2.22 /home/arm/u-boot/arch/arm/config.mk:103: *** code size may be slightly larger /home/arm/u-boot/arch/arm/config.mk:102: *** disabling sibling call optimzation because binutils version < 2.22 /home/arm/u-boot/arch/arm/config.mk:103: *** code size may be slightly larger /home/arm/u-boot/arch/arm/config.mk:102: *** disabling sibling call optimzation because binutils version < 2.22 /home/arm/u-boot/arch/arm/config.mk:103: *** code size may be slightly larger /home/arm/u-boot/arch/arm/config.mk:102: *** disabling sibling call optimzation because binutils version < 2.22 /home/arm/u-boot/arch/arm/config.mk:103: *** code size may be slightly larger /home/arm/u-boot/arch/arm/config.mk:102: *** disabling sibling call optimzation because binutils version < 2.22 /home/arm/u-boot/arch/arm/config.mk:103: *** code size may be slightly larger /home/arm/u-boot/arch/arm/config.mk:102: *** disabling sibling call optimzation because binutils version < 2.22 /home/arm/u-boot/arch/arm/config.mk:103: *** code size may be slightly larger ... and on and on
It makes sense since unless GAS_BUG_125320 is "export"ed to the new make, it's going to be unset again each the build starts a new "make -C"
Thanks for proving me wrong. Just the white-space / multi line thing please, thanks :)