Add proper __sync_*() intrinsics for MIPS.

To make <stdatomic.h> work on MIPS (and ARM) using GCC, we need to
provide implementations of the __sync_*() functions. I already added
these functions for 4 and 8 byte types to libcompiler-rt some time ago,
based on top of <machine/atomic.h>.

Unfortunately, <machine/atomic.h> only provides a subset of the features
needed to implement <stdatomic.h>. This means that in some cases we had
to do compare-and-exchange calls in loops, where a simple ll/sc would
suffice.

Also implement these functions for 1 and 2 byte types. MIPS only
provides ll/sc instructions for 4 and 8 byte types, but this is of
course no limitation. We can simply load 4 bytes and use some bitmask
tricks to modify only the bytes affected.

Discussed on:	mips, arch
Tested with:	QEMU

1 files changed, 2 insertions, 0 deletions

diff --git a/sys/conf/files.mips b/sys/conf/files.mips
index 7308143bbebf..79676b992887 100644
--- a/sys/conf/files.mips
+++ b/sys/conf/files.mips
@@ -35,6 +35,8 @@ mips/mips/pmap.c			standard
 mips/mips/ptrace_machdep.c		standard
 mips/mips/sc_machdep.c			standard
 mips/mips/stack_machdep.c		optional	ddb | stack
+mips/mips/stdatomic.c			standard \
+	compile-with "${NORMAL_C:N-Wmissing-prototypes}"
 mips/mips/support.S			standard
 mips/mips/swtch.S			standard
 mips/mips/sys_machdep.c			standard