arm64: atomics: Use K constraint when toolchain appears to support it

Browse source

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>

...

This commit is contained in:

Will Deacon 2019-08-29 14:34:42 +01:00

parent 5aad6cdabb

commit 03adcbd996

2 changed files with 48 additions and 24 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

9

arch/arm64/Makefile

View file

63

arch/arm64/include/asm/atomic_ll_sc.h

View file