mame20160323.rb

 Original:
 
 Performance counter stats for './miniruby -e@v=42; n=100_000_000;while n>0; x=@v; x=@v; x=@v; n-=1;end':

       5675.422561 task-clock (msec)         #    0.998 CPUs utilized
               159 context-switches          #    0.028 K/sec
                 2 cpu-migrations            #    0.000 K/sec
               889 page-faults               #    0.157 K/sec
       16521817067 cycles                    #    2.911 GHz
        4121915626 stalled-cycles-frontend   #   24.95% frontend cycles idle
   <not supported> stalled-cycles-backend
       35724222782 instructions              #    2.16  insns per cycle
                                             #    0.12  stalled cycles per insn
        5105044210 branches                  #  899.500 M/sec
         200180709 branch-misses             #    3.92% of all branches

       5.687665622 seconds time elapsed


With patch:
 Performance counter stats for './miniruby -e@v=42; n=100_000_000;while n>0; x=@v; x=@v; x=@v; n-=1;end':

       3371.817523 task-clock (msec)         #    0.997 CPUs utilized          
                47 context-switches          #    0.014 K/sec                  
                 2 cpu-migrations            #    0.001 K/sec                  
               891 page-faults               #    0.264 K/sec                  
        9886210809 cycles                    #    2.932 GHz                    
        3685439982 stalled-cycles-frontend   #   37.28% frontend cycles idle   
   <not supported> stalled-cycles-backend  
       25821528963 instructions              #    2.61  insns per cycle        
                                             #    0.14  stalled cycles per insn
        3004551132 branches                  #  891.078 M/sec                  
            169865 branch-misses             #    0.01% of all branches        

       3.381315509 seconds time elapsed

diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 39ca48a..8abd78f 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -774,20 +774,30 @@ vm_search_const_defined_class(const VALUE cbase, ID id)
 #define USE_IC_FOR_IVAR 1
 #endif
 
+#define RB_TYPE_P_(obj, type) ((flags & RUBY_T_MASK) == T_OBJECT)
+#define ROBJECT_NUMIV_(o) \
+    ((flags & ROBJECT_EMBED) ? \
+     ROBJECT_EMBED_LEN_MAX : \
+     ROBJECT(o)->as.heap.numiv)
+#define ROBJECT_IVPTR_(o) \
+    ((flags & ROBJECT_EMBED) ? \
+     ROBJECT(o)->as.ary : \
+     ROBJECT(o)->as.heap.ivptr)
 static inline VALUE
 vm_getivar(VALUE obj, ID id, IC ic, struct rb_call_cache *cc, int is_attr)
 {
+    VALUE flags = T_OBJECT | ROBJECT_EMBED;
 #if USE_IC_FOR_IVAR
-    if (RB_TYPE_P(obj, T_OBJECT)) {
+    if (RB_TYPE_P_(obj, T_OBJECT) && (flags & ROBJECT_EMBED)) {
 	VALUE val = Qundef;
 	VALUE klass = RBASIC(obj)->klass;
-	const long len = ROBJECT_NUMIV(obj);
-	const VALUE *const ptr = ROBJECT_IVPTR(obj);
+	const long len = ROBJECT_NUMIV_(obj);
+	const VALUE *const ptr = ROBJECT_IVPTR_(obj);
 
 	if (LIKELY(is_attr ? cc->aux.index > 0 : ic->ic_serial == RCLASS_SERIAL(klass))) {
 	    long index = !is_attr ? (long)ic->ic_value.index : (long)(cc->aux.index - 1);
 
-	    if (index < len) {
+	    if (LIKELY(index < len)) {
 		val = ptr[index];
 	    }
 	}