Lazily move PC with RUBY_VM_CHECK_INTS

```
$ benchmark-driver -v --rbenv 'before --jit;after --jit' --repeat-count=12 --alternate --output=all benchmark.yml
before --jit: ruby 3.0.0dev (2020-12-17T06:17:46Z master 3b4d698e0b) +JIT [x86_64-linux]
after --jit: ruby 3.0.0dev (2020-12-17T07:01:48Z master 843abb96f0) +JIT [x86_64-linux]
last_commit=Lazily move PC with RUBY_VM_CHECK_INTS
Calculating -------------------------------------
                                 before --jit           after --jit
Optcarrot Lan_Master.nes    80.29343646660429     83.15779723251525 fps
                            82.26755637885149     85.50197941326810
                            83.50682959728820     88.14657804306270
                            85.01236533133049     88.78201988978667
                            87.81799334561326     88.94841008936447
                            87.88228562393064     89.37925215601926
                            88.06695585889995     89.86143277214475
                            88.84730834922165     90.00773346420887
                            90.46317871213088     90.82603371104014
                            90.96308347148916     91.29797694822179
                            90.97945938504556     91.31086331868738
                            91.57127890154500     91.49949184318844
```

5 files changed, 26 insertions, 8 deletions

diff --git a/insns.def b/insns.def
index 1c94a7f7f8..c62e2f711b 100644
--- a/insns.def
+++ b/insns.def
@@ -961,7 +961,7 @@ jump
 ()
 ()
 /* Same discussion as leave. */
-// attr bool leaf = false; /* has rb_threadptr_execute_interrupts() */
+// attr bool leaf = leafness_of_check_ints; /* has rb_threadptr_execute_interrupts() */
 {
     RUBY_VM_CHECK_INTS(ec);
     JUMP(dst);
@@ -974,7 +974,7 @@ branchif
 (VALUE val)
 ()
 /* Same discussion as jump. */
-// attr bool leaf = false; /* has rb_threadptr_execute_interrupts() */
+// attr bool leaf = leafness_of_check_ints; /* has rb_threadptr_execute_interrupts() */
 {
     if (RTEST(val)) {
 	RUBY_VM_CHECK_INTS(ec);
@@ -989,7 +989,7 @@ branchunless
 (VALUE val)
 ()
 /* Same discussion as jump. */
-// attr bool leaf = false; /* has rb_threadptr_execute_interrupts() */
+// attr bool leaf = leafness_of_check_ints; /* has rb_threadptr_execute_interrupts() */
 {
     if (!RTEST(val)) {
 	RUBY_VM_CHECK_INTS(ec);
@@ -1004,7 +1004,7 @@ branchnil
 (VALUE val)
 ()
 /* Same discussion as jump. */
-// attr bool leaf = false; /* has rb_threadptr_execute_interrupts() */
+// attr bool leaf = leafness_of_check_ints; /* has rb_threadptr_execute_interrupts() */
 {
     if (NIL_P(val)) {
 	RUBY_VM_CHECK_INTS(ec);
diff --git a/tool/ruby_vm/models/bare_instructions.rb b/tool/ruby_vm/models/bare_instructions.rb
index b0cc83a65a..6b5f1f6cf8 100755
--- a/tool/ruby_vm/models/bare_instructions.rb
+++ b/tool/ruby_vm/models/bare_instructions.rb
@@ -112,6 +112,10 @@ class RubyVM::BareInstructions
     @attrs.fetch('leaf').expr.expr == 'true;'
   end
 
+  def leaf_without_check_ints?
+    @attrs.fetch('leaf').expr.expr == 'leafness_of_check_ints;'
+  end
+
   def handle_canary stmt
     # Stack canary is basically a good thing that we want to add, however:
     #
diff --git a/tool/ruby_vm/views/_leaf_helpers.erb b/tool/ruby_vm/views/_leaf_helpers.erb
index 2637f8777d..cbb7373e1c 100644
--- a/tool/ruby_vm/views/_leaf_helpers.erb
+++ b/tool/ruby_vm/views/_leaf_helpers.erb
@@ -10,6 +10,10 @@
 
 #include "iseq.h"
 
+// This is used to tell MJIT that this insn would be leaf if CHECK_INTS didn't exist.
+// It should be used only when RUBY_VM_CHECK_INTS is directly written in insns.def.
+static bool leafness_of_check_ints = false;
+
 static bool
 leafness_of_defined(rb_num_t op_type)
 {
diff --git a/tool/ruby_vm/views/_mjit_compile_insn_body.erb b/tool/ruby_vm/views/_mjit_compile_insn_body.erb
index bc77b02b71..900480ddc0 100644
--- a/tool/ruby_vm/views/_mjit_compile_insn_body.erb
+++ b/tool/ruby_vm/views/_mjit_compile_insn_body.erb
@@ -20,14 +20,14 @@
 %     # For `leave`. We can't proceed next ISeq in the same JIT function.
 %     expr.gsub!(/^(?<indent>\s*)RESTORE_REGS\(\);\n/) do
 %       indent = Regexp.last_match[:indent]
-%       <<-RESTORE_REGS.gsub(/^ +/, '')
+%       <<-end.gsub(/^ +/, '')
 %         #if OPT_CALL_THREADED_CODE
 %         #{indent}rb_ec_thread_ptr(ec)->retval = val;
 %         #{indent}return 0;
 %         #else
 %         #{indent}return val;
 %         #endif
-%       RESTORE_REGS
+%       end
 %     end
 %     expr.gsub!(/^(?<indent>\s*)NEXT_INSN\(\);\n/) do
 %       indent = Regexp.last_match[:indent]
@@ -47,6 +47,15 @@
 %   #
 %   # TODO: support combination of following macros in the same line
 %   case line
+%   when /\A\s+RUBY_VM_CHECK_INTS\(ec\);\s+\z/
+%     if insn.leaf_without_check_ints? # lazily move PC here
+        fprintf(f, "            if (UNLIKELY(RUBY_VM_INTERRUPTED_ANY(ec))) {\n");
+        fprintf(f, "                reg_cfp->pc = original_body_iseq + %d;\n", next_pos); /* ADD_PC(INSN_ATTR(width)); */
+        fprintf(f, "                rb_threadptr_execute_interrupts(rb_ec_thread_ptr(ec), 0);\n");
+        fprintf(f, "            }\n");
+%     else
+        fprintf(f, <%= to_cstr.call(line) %>);
+%     end
 %   when /\A\s+JUMP\((?<dest>[^)]+)\);\s+\z/
 %     dest = Regexp.last_match[:dest]
 %
diff --git a/tool/ruby_vm/views/_mjit_compile_pc_and_sp.erb b/tool/ruby_vm/views/_mjit_compile_pc_and_sp.erb
index f6d611693d..390b3ce525 100644
--- a/tool/ruby_vm/views/_mjit_compile_pc_and_sp.erb
+++ b/tool/ruby_vm/views/_mjit_compile_pc_and_sp.erb
@@ -5,9 +5,10 @@
 % # conditions mentioned  in the  file COPYING  are met.   Consult the  file for
 % # details.
 %
-% # JIT: Move pc for catch table on catch_except_p, and for #caller_locations and rb_profile_frames on !insn.always_leaf?
+% # JIT: When an insn is leaf, we don't need to Move pc for a catch table on catch_except_p, #caller_locations,
+% #      and rb_profile_frames. For check_ints, we lazily move PC when we have interruptions.
         MAYBE_UNUSED(bool pc_moved_p) = false;
-        if (<%= insn.always_leaf? ? 'false' : 'true' %>) {
+        if (<%= !(insn.always_leaf? || insn.leaf_without_check_ints?) %>) {
             fprintf(f, "    reg_cfp->pc = original_body_iseq + %d;\n", next_pos); /* ADD_PC(INSN_ATTR(width)); */
             pc_moved_p = true;
         }