* 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.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36099 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 40 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index ed06937658..068fe4438d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,43 @@
+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