Hi Mark, On Thu, Jan 11, 2024 at 7:26 PM Mark Rutland <mark.rutland@xxxxxxx> wrote: > > On Thu, Jan 11, 2024 at 09:42:40AM +0800, richard clark wrote: > > On Wed, Jan 10, 2024 at 10:12 PM Segher Boessenkool > > <segher@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > On Wed, Jan 10, 2024 at 01:59:53PM +0800, richard clark wrote: > > > > A ported driver in linux kernel calls '__sync_val_compare_and_swap', > > > > > > That is a builtin function. It does not necessarily expand to an actual > > > function call. aarch64 will typically expand it to inline code. > > > > > native gcc version: > > gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0 > > cross-compiler gcc version: > > aarch64-linux-gnu-gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0 > > > > Interesting, the same '__sync_val_compare_and_swap' in the .c file > > will be 'U __aarch64_cas4_sync' in the .o file compiled by native, > > will be 't __cmpxchg_case_mb_32' in the .o file compiled by > > aarch64-linux-gnu-gcc... don't know what the reason is > > The __cmpxchg_case_mb_32() function is kernel code from > arch/arm64/include/asm/cmpxchg.h, so I do not believe that's being generated by > the compiler from __sync_val_compare_and_swap(). > > Are you certain that's being built from the exact same C file? > > Are you able to share the code in question? Where has it come from in the first > place? > Ah, double check and the misleading info about the native and cross compiler, the native gcc(Ubuntu 11.4.0-1ubuntu1~22.04) and the cross-compiler - aarch64-linux-gnu-gcc(Ubuntu 11.4.0-1ubuntu1~22.04) will generate the same link error, but the cross-compiler - aarch64-buildroot-linux-gnu-gcc. (aarch64-buildroot-linux-gnu-gcc.br_real (Buildroot 2020.08) 9.3.0) will not generate the link error, I believe it should be as you said, the aarch64-buildroot-linux-gnu-gcc doesn't enable '-moutline-atomics' by default. > > Thanks, > Mark.
