Summary: * Rebase and test the shrink-wrap patches. * Learn how branch cost impact on code generation.

Details: 1. Rebase and test the shrink-wrap patches. * For pretend arguments, it is hard to generate correct dwarf info for case: * Add dwarf info for ldrd_pop. Testing is ongoing. * Expose an interface from regcpprog and do copy propagation for the entry block. Benchmark logs show there are much more functions can be shrink-wrapped.

2. Read codes and enhance ifcvt.c. * For IF-THEN-ELSE, if the last insn of then_bb or else_bb is ANY_RETURN_P, we can save one JUMP. In this, we'd keep max MAX_CONDITIONAL_EXECUTE, not "max *= 2". A patch is sent out for review. * Take the branch probability into account. Test is ongoing.

3. R/M toolchain related work.

Plan: * Follow up the shrink-wrap dwarf info issue. * Investigate benchmarks which is impacted by different branch cost.

Planed leaves: * Feb. 9 - 15: Chinese Spring Festival.

Best Regards! -Zhenqiang