From dd723771c118da71aa58bb74537cacaec425542a Mon Sep 17 00:00:00 2001
From: Koichi Sasada <ko1@atdot.net>
Date: Fri, 29 Nov 2019 03:02:44 +0900
Subject: fastpath for ivar read of FL_EXIVAR objects.

vm_getivar() provides fastpath for T_OBJECT by caching an index
of ivar. This patch also provides fastpath for FL_EXIVAR objects.
FL_EXIVAR objects have an each ivar array and index can be cached
as T_OBJECT. To access this ivar array, generic_iv_tbl is exposed
by rb_ivar_generic_ivtbl() (declared in variable.h which is newly
introduced).

Benchmark script:

Benchmark.driver(repeat_count: 3){|x|
  x.executable name: 'clean', command: %w'../clean/miniruby'
  x.executable name: 'trunk', command: %w'./miniruby'

  objs = [Object.new, 'str', {a: 1, b: 2}, [1, 2]]

  objs.each.with_index{|obj, i|
    rep = obj.inspect
    rep = 'Object.new' if /\#/ =~ rep
    x.prelude str = %Q{
      v#{i} = #{rep}
      def v#{i}.foo
        @iv # ivar access method (attr_reader)
      end
      v#{i}.instance_variable_set(:@iv, :iv)
    }
    puts str
    x.report %Q{
      v#{i}.foo
    }
  }
}

Result:

      v0.foo # T_OBJECT

               clean:  85387141.8 i/s
               trunk:  85249373.6 i/s - 1.00x  slower

      v1.foo # T_STRING

               trunk:  57894407.5 i/s
               clean:  39957178.6 i/s - 1.45x  slower

      v2.foo # T_HASH

               trunk:  56629413.2 i/s
               clean:  39227088.9 i/s - 1.44x  slower

      v3.foo # T_ARRAY

               trunk:  55797530.2 i/s
               clean:  38263572.9 i/s - 1.46x  slower
---
 variable.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

(limited to 'variable.c')

diff --git a/variable.c b/variable.c
index 46573523b4..d6e2f2a601 100644
--- a/variable.c
+++ b/variable.c
@@ -23,6 +23,7 @@
 #include "debug_counter.h"
 #include "vm_core.h"
 #include "transient_heap.h"
+#include "variable.h"
 
 static struct rb_id_table *rb_global_tbl;
 static ID autoload, classpath, tmp_classpath;
@@ -34,12 +35,6 @@ static VALUE rb_const_search(VALUE klass, ID id, int exclude, int recurse, int v
 static st_table *generic_iv_tbl;
 static st_table *generic_iv_tbl_compat;
 
-/* per-object */
-struct gen_ivtbl {
-    uint32_t numiv;
-    VALUE ivptr[FLEX_ARY_LEN];
-};
-
 struct ivar_update {
     union {
 	st_table *iv_index_tbl;
@@ -804,6 +799,12 @@ gen_ivtbl_get(VALUE obj, struct gen_ivtbl **ivtbl)
     return 0;
 }
 
+struct st_table *
+rb_ivar_generic_ivtbl(void)
+{
+    return generic_iv_tbl;
+}
+
 static VALUE
 generic_ivar_delete(VALUE obj, ID id, VALUE undef)
 {
-- 
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