riscv_pmp.c: Revert LOG2_CEIL back to run-time log2ceil function #11374
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The macro LOG2_CEIL is intended to be used in the pre-processor phase. If
used run-time it will generate a massive amount of extra code (~3.5K) which
is a problem, as the PMP configuration is quite often executed from a first
stage bootloader with a limited amount of code memory.
Code size differences pre- and post:
Memory region Used Size Region Size %age Used
envm: 112064 B 112384 B 99.72%
Memory region Used Size Region Size %age Used
envm: 108952 B 112384 B 96.95%
xiaoxiang781216
approved these changes
Dec 12, 2023
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| static uintptr_t log2ceil(uintptr_t x) |
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should we extract to a common function
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Yes that could be useful, I just didn't know where to put it. Does a place for kernel internal / integer math functions exist ?
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put to include/nuttx/lib/math32.h too.
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Summary
The macro LOG2_CEIL is intended to be used in the pre-processor phase. If used run-time it will generate a massive amount of extra code (~3.5K) which is a problem, as the PMP configuration is quite often executed from a first stage bootloader with a limited amount of code memory.
Code size differences pre- and post:
Impact
Decrease code footprint of the PMP driver
Testing
MPFS