Adapt atomic compare and swap to ARMv8-M Baseline
2016-10-26 Thomas Preud'homme <thomas.preudhomme@arm.com>
gcc/
* config/arm/sync.md (atomic_compare_and_swap<mode>_1): Add new ARMv8-M
Baseline only alternatives to (i) hold store atomic success value in a
return register rather than a scratch register, (ii) use a low register
for it and to (iii) ensure the cbranchsi insn generated by the split
respect the constraints of Thumb-1 cbranchsi4_insn and
cbranchsi4_scratch.
* config/arm/thumb1.md (cbranchsi4_insn): Add comment to indicate
constraints must match those in atomic_compare_and_swap.
(cbranchsi4_scratch): Likewise.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@241578 138bc75d-0d04-0410-961f-82ee72b054a4