[U-Boot] [PATCH 0/2] armv8: reduce exception handling code size

[Andre Przywara]

These two patches try to address the issue that the default ARMv8
exception vectors take up quite some code space, but don't provide much
benefit apart from a crash dump. Since the overhead might not be justified
for some very size-restricted SPLs, we try to reduce the code size:
- Patch 1/2 stuffs the shared register save/restore code into the gaps
  between the exception entries, which have to follow an architectural
  128 byte alignment requirement.
  This reduces the code size by about 250 bytes, while still having the
  full functionality.
- Patch 2/2 goes much further by introducing a Kconfig symbol allowing to
  drop the exception vector table for the SPL at all, at the expense of
  losing the crash dump feature. On the Allwinner A64 SPL this saves about
  3KB of code, which sound quite worthwhile with our chronically tight
  SPL builds.

The last feature is off by default, but could be selected manually in
menuconfig to fix too big SPL builds.

Cheers,
Andre.

Andre Przywara (2):
  armv8: Reduce exception handling code
  armv8: make SPL exception vectors optional

 arch/arm/cpu/armv8/Kconfig      |  11 ++++
 arch/arm/cpu/armv8/Makefile     |   4 ++
 arch/arm/cpu/armv8/exceptions.S | 132 +++++++++++++++++++++++++---------------
 arch/arm/cpu/armv8/start.S      |  19 ++++--
 4 files changed, 112 insertions(+), 54 deletions(-)

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2.14.4