RT-Thread/rt-thread — pull request #112 by aozima (2013-06-23 08:31:58+00:00)
Title: update libcpu/arm/cortex-m4: support lazy stack optimized.

优化cortex-m4f线程切换，按需保存FPU寄存器。
http://www.rt-thread.org/phpBB3/viewtopic.php?f=2&t=2872