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authorWill Deacon <will@kernel.org>2019-08-29 14:34:42 +0100
committerWill Deacon <will@kernel.org>2019-08-30 11:18:40 +0100
commit03adcbd996be7ce81cac793b1511406a7a4df117 (patch)
tree47a2847b763aad328f42f7cbc22984a129a47227 /Makefile
parent5aad6cdabbf91fd330bd216fe3c93d90f78bc7e7 (diff)
arm64: atomics: Use K constraint when toolchain appears to support it
The 'K' constraint is a documented AArch64 machine constraint supported by GCC for matching integer constants that can be used with a 32-bit logical instruction. Unfortunately, some released compilers erroneously accept the immediate '4294967295' for this constraint, which is later refused by GAS at assembly time. This had led us to avoid the use of the 'K' constraint altogether. Instead, detect whether the compiler is up to the job when building the kernel and pass the 'K' constraint to our 32-bit atomic macros when it appears to be supported. Signed-off-by: Will Deacon <will@kernel.org>
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