Eliminate array allocation for f(1, *a, &lvar) and f(1, *a, &@Iv)

Due to how the compiler works, while f(*a, &lvar) and f(*a, &@Iv)
do not allocate an array, but f(1, *a, &lvar) and f(1, *a, &@Iv)
do.  It's probably possible to fix this in the compiler, but
seems easiest to fix this in the peephole optimizer.

Eliminating this array allocation is as safe as the current
elimination of the array allocation for f(*a, &lvar) and
f(*a, &@Iv).

compile.c

@@ -3854,6 +3854,30 @@ iseq_peephole_optimize(rb_iseq_t *iseq, LINK_ELEMENT *list, const int do_tailcal
             if ((flag & VM_CALL_ARGS_SPLAT) && !(flag & (VM_CALL_KW_SPLAT|VM_CALL_ARGS_BLOCKARG))) {
                 OPERAND_AT(iobj, 0) = Qfalse;
             }
+        } else if (IS_NEXT_INSN_ID(niobj, getlocal) || IS_NEXT_INSN_ID(niobj, getinstancevariable)) {
+            niobj = niobj->next;
+
+            if (IS_NEXT_INSN_ID(niobj, send)) {
+                niobj = niobj->next;
+                unsigned int flag = vm_ci_flag((const struct rb_callinfo *)OPERAND_AT(niobj, 0));
+
+                if ((flag & VM_CALL_ARGS_SPLAT)) {
+                    /*
+                    * Eliminate array allocation for f(1, *a, &lvar) and f(1, *a, &@iv)
+                    *
+                    *  splatarray true
+                    *  getlocal / getinstancevariable
+                    *  send ARGS_SPLAT|ARGS_BLOCKARG and not KW_SPLAT
+                    * =>
+                    *  splatarray false
+                    *  getlocal / getinstancevariable
+                    *  send
+                    */
+                    if ((flag & VM_CALL_ARGS_BLOCKARG) && !(flag & VM_CALL_KW_SPLAT)) {
+                        OPERAND_AT(iobj, 0) = Qfalse;
+                    }
+                }
+            }
         }
     }