[U-Boot] [PATCH 3/6] ARM: enable Thumb build

Aneesh V
2012-03-08T17:10:41Z

Enable Thumb build and ARM-Thumb interworking based on the new
config flag CONFIG_SYS_THUMB_BUILD

Signed-off-by: Aneesh V <aneesh@ti.com>
---
Changes in v4:
- Use ':=' instead of '+=' when computed make variables
are involved

Changes in v3:
- None

Changes from V1 to V2:
- None

Changes from RFC to V1:
- Fixed review comments from Tom Rini <trini@ti.com>
---
README | 8 ++++++++
arch/arm/config.mk | 22 +++++++++++++++-------
2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/README b/README
index 8964672..bdb428e 100644
--- a/README
+++ b/README
@@ -426,6 +426,14 @@ The following options need to be configured:
Select high exception vectors of the ARM core, e.g., do not
clear the V bit of the c1 register of CP15.

+ CONFIG_SYS_THUMB_BUILD
+
+ Use this flag to build U-Boot using the Thumb instruction
+ set for ARM architectures. Thumb instruction set provides
+ better code density. For ARM architectures that support
+ Thumb2 this flag will result in Thumb2 code generated by
+ GCC.
+
- Linux Kernel Interface:
CONFIG_CLOCKS_IN_MHZ

diff --git a/arch/arm/config.mk b/arch/arm/config.mk
index 45f9dca..d4fa1f8 100644
--- a/arch/arm/config.mk
+++ b/arch/arm/config.mk
@@ -33,25 +33,33 @@ endif

PLATFORM_CPPFLAGS += -DCONFIG_ARM -D__ARM__

-# Explicitly specifiy 32-bit ARM ISA since toolchain default can be -mthumb:
-PF_CPPFLAGS_ARM := $(call cc-option,-marm,)
+# Choose between ARM/Thumb instruction sets
+ifeq ($(CONFIG_SYS_THUMB_BUILD),y)
+PF_CPPFLAGS_ARM := $(call cc-option, -mthumb -mthumb-interwork,\
+ $(call cc-option,-marm,)\
+ $(call cc-option,-mno-thumb-interwork,)\
+ )
+else
+PF_CPPFLAGS_ARM := $(call cc-option,-marm,) \
+ $(call cc-option,-mno-thumb-interwork,)
+endif

# Try if EABI is supported, else fall back to old API,
# i. e. for example:
# - with ELDK 4.2 (EABI supported), use:
-# -mabi=aapcs-linux -mno-thumb-interwork
+# -mabi=aapcs-linux
# - with ELDK 4.1 (gcc 4.x, no EABI), use:
-# -mabi=apcs-gnu -mno-thumb-interwork
+# -mabi=apcs-gnu
# - with ELDK 3.1 (gcc 3.x), use:
-# -mapcs-32 -mno-thumb-interwork
+# -mapcs-32
PF_CPPFLAGS_ABI := $(call cc-option,\
- -mabi=aapcs-linux -mno-thumb-interwork,\
+ -mabi=aapcs-linux,\
$(call cc-option,\
-mapcs-32,\
$(call cc-option,\
-mabi=apcs-gnu,\
)\
- ) $(call cc-option,-mno-thumb-interwork,)\
+ )\
)
PLATFORM_CPPFLAGS += $(PF_CPPFLAGS_ARM) $(PF_CPPFLAGS_ABI)

--
1.7.1