Re: Some questions about the gcc __sync intrinsics

/usr/local/linare-gcc-5.2/bin/gcc -S -O3 -march=armv8-a+lse test.c

add_int: ldaddal w0, w0, [x1] add w2, w0, w0 mov w0, w2 ret

Am I going mad, or does this just return the contents of the memory location * 2.

ldaddal w0, w0, [x1]

Returns the original contents of [x1] in w0.

add w2, w0, w0

doubles it.

mov w0, w2

returns it.

I think __sync_add_and_fetch should return the updated contents.

Here is the test C code again.

int add_int(int add_value, int *dest) { return __sync_add_and_fetch(dest, add_value); }

Regards, Ed.