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+Fri Jun 15 19:22:13 2012 Koichi Sasada <ko1@atdot.net>
+
+ * vm_core.h: remove VM_FRAME_MAGIC_FINISH (finish frame type).
+ Before this commit:
+ `finish frame' was place holder which indicates that VM loop
+ needs to return function.
+ If a C method calls a Ruby methods (a method written by Ruby),
+ then VM loop will be (re-)invoked. When the Ruby method returns,
+ then also VM loop should be escaped. `finish frame' has only
+ one instruction `finish', which returns VM loop function.
+ VM loop function executes `finish' instruction, then VM loop
+ function returns itself.
+ With such mechanism, `leave' instruction (which returns one
+ frame from current scope) doesn't need to check that this `leave'
+ should also return from VM loop function.
+ Strictly, one branch can be removed from `leave' instructon.
+ Consideration:
+ However, pushing the `finish frame' needs costs because
+ it needs several memory accesses. The number of pushing
+ `finish frame' is greater than I had assumed. Of course,
+ pushing `finish frame' consumes additional control frame.
+ Moreover, recent processors has good branch prediction,
+ with which we can ignore such trivial checking.
+ After this commit:
+ Finally, I decide to remove `finish frame' and `finish'
+ instruction. Some parts of VM depend on `finish frame',
+ so the new frame flag VM_FRAME_FLAG_FINISH is introduced.
+ If this frame should escape from VM function loop, then
+ the result of VM_FRAME_TYPE_FINISH_P(cfp) is true.
+ `leave' instruction checks this flag every time.
+ I measured performance on it. However on my environments,
+ it improves some benchmarks and slows some benchmarks down.
+ Maybe it is because of C compiler optimization parameters.
+ I'll re-visit here if this cause problems.
+
+ * insns.def (leave, finish): remove finish instruction.
+
+ * vm.c, vm_eval.c, vm_exec.c, vm_backtrace.c, vm_dump.c:
+ apply above changes.
+
Fri Jun 15 19:11:23 2012 Nobuyoshi Nakada <nobu@ruby-lang.org>
* lib/test/unit.rb (Test::Unit::Runner#puke): always add skipped