make opt_case_dispatch leaf

This instruction can be written without rb_funcall. It not only boosts
performance of case statements, but also makes room of future JIT
improvements.  Because opt_case_dispatch is about optimization this
should not be a bad thing to have.

----

trunk: ruby 2.6.0dev (2018-09-05 trunk 64634) [x86_64-darwin15]
ours: ruby 2.6.0dev (2018-09-12 leaf-insn 64688) [x86_64-darwin15]
last_commit=make opt_case_dispatch leaf
Calculating -------------------------------------
                          trunk        ours
        vm2_case_lit      1.366       2.012 i/s -       1.000 times in 0.731839s 0.497008s

Comparison:
                     vm2_case_lit
                ours:         2.0 i/s
               trunk:         1.4 i/s - 1.47x  slower



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64689 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 0 insertions, 4 deletions

diff --git a/insns.def b/insns.def
index cf9d980277..ced6054cce 100644
--- a/insns.def
+++ b/insns.def
@@ -1020,10 +1020,6 @@ opt_case_dispatch
 (CDHASH hash, OFFSET else_offset)
 (..., VALUE key)
 ()
-/* Case dispatch involves hash lookup, which inevitably compares
- * several objects each other.  The same discussion to
- * opt_newarray_max also goes here. */
-// attr bool leaf = false; /* has rb_any_cmp() */
 // attr rb_snum_t sp_inc = -1;
 {
     OFFSET dst = vm_case_dispatch(hash, else_offset, key);