avoid extra dup and pop in compile_op_asgn2

Co-authored-by: John Hawthorn <jhawthorn@github.com>

benchmark/vm_lvar_cond_set.yml

@@ -0,0 +1,8 @@
+benchmark:
+  vm_lvar_cond_set: |
+    a ||= 1
+    b ||= 1
+    c ||= 1
+    d ||= 1
+    nil
+loop_count: 30000000

compile.c

@@ -8663,6 +8663,17 @@ compile_op_asgn2(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *const node
       lfin:       # o ?
       pop       # o
 
+      # or (popped)
+      if lcfin  # r
+      eval v    # r v
+      send a=   # ?
+      jump lfin # ?
+
+      lcfin:      # r
+
+      lfin:       # ?
+      pop       #
+
       # and
       dup       # r o o
       unless lcfin
@@ -8691,32 +8702,36 @@ compile_op_asgn2(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *const node
     ADD_SEND_WITH_FLAG(ret, node, vid, INT2FIX(0), INT2FIX(asgnflag));
 
     if (atype == idOROP || atype == idANDOP) {
-        ADD_INSN(ret, node, dup);
+        if (!popped) {
+            ADD_INSN(ret, node, dup);
+        }
         if (atype == idOROP) {
             ADD_INSNL(ret, node, branchif, lcfin);
         }
         else { /* idANDOP */
             ADD_INSNL(ret, node, branchunless, lcfin);
         }
-        ADD_INSN(ret, node, pop);
+        if (!popped) {
+            ADD_INSN(ret, node, pop);
+        }
         CHECK(COMPILE(ret, "NODE_OP_ASGN2 val", node->nd_value));
-        ADD_INSN(ret, node, swap);
-        ADD_INSN1(ret, node, topn, INT2FIX(1));
+        if (!popped) {
+            ADD_INSN(ret, node, swap);
+            ADD_INSN1(ret, node, topn, INT2FIX(1));
+        }
         ADD_SEND_WITH_FLAG(ret, node, aid, INT2FIX(1), INT2FIX(asgnflag));
         ADD_INSNL(ret, node, jump, lfin);
 
         ADD_LABEL(ret, lcfin);
-        ADD_INSN(ret, node, swap);
+        if (!popped) {
+            ADD_INSN(ret, node, swap);
+        }
 
         ADD_LABEL(ret, lfin);
         ADD_INSN(ret, node, pop);
         if (lskip) {
             ADD_LABEL(ret, lskip);
         }
-        if (popped) {
-            /* we can apply more optimize */
-            ADD_INSN(ret, node, pop);
-        }
     }
     else {
         CHECK(COMPILE(ret, "NODE_OP_ASGN2 val", node->nd_value));
@@ -8848,9 +8863,7 @@ compile_op_log(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *const node,
     }
 
     ADD_LABEL(ret, lassign);
-
     CHECK(COMPILE_(ret, "NODE_OP_ASGN_AND/OR#nd_value", node->nd_value, popped));
-
     ADD_LABEL(ret, lfin);
     return COMPILE_OK;
 }