Hi Albert,
On 25.02.2015 23:09, Albert ARIBAUD wrote:
On Tue, 24 Feb 2015 14:53:36 +0100, Albert ARIBAUD albert.u.boot@aribaud.net wrote:
When building a THumb-1-only target with CONFIG_SYS_THUMB_BUILD, some files fail to build, most of the time because they include mcr instructions, which only exist for Thumb-2.
Thos patch introduces a Kconfig option CONFIG_THUMB2 and uses it to select between Thumb-2 and ARM mode for the aforementioned files.
Signed-off-by: Albert ARIBAUD albert.u.boot@aribaud.net
This patch has been build-tested and run-tested on ED Mini V2, above the "edmini: switch to SPL" patch, and found to reduce U-Boot size by 25% and SPL size by 14%... and to run fine. :)
This patch has also been tested against side effects on the non-Thumb wireless_space target. The binaries produced with and without ths patch were found to differ only by their version string.
Changes in v2:
- fixed a typo in the commit message
- added file arch/arm/thumb1/include/asm/proc-armv/system.h, which overrides arch/arm/include/asm/proc-armv/system.h when building for Thumb-1 and provides non-functional but Thumb-compilable IRQ and FIQ related macros and functions.
Ok, this does not fare as good as I have hoped, because there are also thumb1-unfrendly macros in arch/arm/include/asm/cache.h, this time with mcr and mrc instructions.
/me hates macros used as inline functions. :(
I cannot just replace the macros with empty inline functions as I did with arch/arm/include/asm/proc-armv/system.h, since this would cause cache to not work. :(
This leaves only one solution: when buildding for thumb1, replace the macros in cache.h with plain function prototypes, and provide simple ARM-state implementations for these. We'll lose a bit of performance as instead of a single mcr or mrc instruction, we'll have a call switching from Thumb to ARM state, the mcr/mrc instruction, and a return to Thumb state. Hopefully that won't hurt performance too much.
V3 in the works.
Any update on this?
Thanks, Stefan