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authorKoen Kooi <koen@openembedded.org>2008-11-14 11:27:07 +0100
committerKoen Kooi <koen@openembedded.org>2008-11-14 11:27:07 +0100
commit8d2f8e65e01ea07335c3d172866d1ccbd10ebdcc (patch)
tree3dcdc07d5135ed2a4948be2625c12a81c23ac059 /conf
parentc84c511adf8559df2ed2be13de06b1ba5474cecd (diff)
angstrom: switch armv4t to thumb as per RFC on angstrom-devel
Diffstat (limited to 'conf')
-rw-r--r--conf/distro/include/angstrom.inc26
1 files changed, 26 insertions, 0 deletions
diff --git a/conf/distro/include/angstrom.inc b/conf/distro/include/angstrom.inc
index 48cbb49d2c..5d250074c5 100644
--- a/conf/distro/include/angstrom.inc
+++ b/conf/distro/include/angstrom.inc
@@ -21,6 +21,32 @@ CACHE = "${TMPDIR}/cache/${ANGSTROM_MODE}/${MACHINE}"
DEPLOY_DIR = "${TMPDIR}/deploy/${ANGSTROM_MODE}"
require conf/distro/include/angstrom-${ANGSTROM_MODE}.inc
+# ARM920T and up can use thumb mode to decrease binary size at the expense of speed
+# (the complete story is a bit more nuanced due to cache starvation)
+# Angstrom turns on thumb for armv4t machine according to this RFC:
+# http://lists.linuxtogo.org/pipermail/angstrom-distro-devel/2008-October/002714.html
+
+# We can't do ARM_INSTRUCTION_SET_armv4t since that will un-overridable in recipes like gcc
+ANGSTROM_ARM_INSTRUCTION_SET ?= "arm"
+ANGSTROM_ARM_INSTRUCTION_SET_armv4t = "thumb"
+
+ARM_INSTRUCTION_SET = "${ANGSTROM_ARM_INSTRUCTION_SET}"
+# "arm" "thumb"
+# The instruction set the compiler should use when generating application
+# code. The kernel is always compiled with arm code at present. arm code
+# is the original 32 bit ARM instruction set, thumb code is the 16 bit
+# encoded RISC sub-set. Thumb code is smaller (maybe 70% of the ARM size)
+# but requires more instructions (140% for 70% smaller code) so may be
+# slower.
+
+THUMB_INTERWORK = "yes"
+# "yes" "no"
+# Whether to compile with code to allow interworking between the two
+# instruction sets. This allows thumb code to be executed on a primarily
+# arm system and vice versa. It is strongly recommended that DISTROs not
+# turn this off - the actual cost is very small.
+
+
#Use this variable in feeds and other parts that need a URI
ANGSTROM_URI ?= "http://www.angstrom-distribution.org"