riscv: prevent compressed instructions in alternatives

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Instructions are opportunistically compressed by the RISC-V assembler
when possible, but in alternatives-blocks both the old and new content
need to be the same size, so having the toolchain do somewhat random
optimizations will cause strange side-effects like
"attempt to move .org backwards" compile-time errors.

Already a simple "and" used in alternatives assembly will cause these
mismatched code sizes.

So prevent compressed instructions to be generated in alternatives-
code and use option-push and -pop to only limit this to the relevant
code blocks

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Link: https://lore.kernel.org/r/20220511192921.2223629-7-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

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Heiko Stuebner 2022-05-11 21:29:15 +02:00 • committed by Palmer Dabbelt

parent e509204acb

commit 49b290e430

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arch/riscv/include/asm/alternative-macros.h

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