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[Core] Squeeze AVR some more with -mrelax and -mcall-prologues #16269

Merged
merged 2 commits into from
Feb 27, 2022
Merged

[Core] Squeeze AVR some more with -mrelax and -mcall-prologues #16269

merged 2 commits into from
Feb 27, 2022

Commits on Feb 7, 2022

  1. [Core] Enable linker relaxation for AVR targets 

    This can save some bytes for by using RJMP instructions to
memory location that are +-2k relative to the current
program counter position. Unfortunately this is only possible
when LTO is disabled.
    @KarlK90
    KarlK90 committed Feb 7, 2022
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  2. [Core] Use -mcall-prologues the save code size 

    From GCC Manual:

Functions prologues/epilogues are expanded as calls
to appropriate subroutines. Code size is smaller.

Small programs with few functions can increase in size,
but QMK benefits from this as it is rather large.

See: https://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_optflags
    @KarlK90
    KarlK90 committed Feb 7, 2022
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