JIT: Double-Devirtualize atpos_i

only limited usefulness, since rakudo code mostly
generates atposref rather than atpos instructions.

Spesh will, at some point, know to turn atposref
into atpos, though, and atposref can also be
double-devirtualized in much the same way
atpos currently is.

src/6model/reprs/VMArray.c

@@ -1421,18 +1421,40 @@ MVMObject *vmarray_direct_atpos_o_to_o(MVMThreadContext *tc, MVMObject *obj, MVM
     return found ? found : tc->instance->VMNull;
 }
 
+MVMint64 vmarray_direct_atpos_i64_to_i(MVMThreadContext *tc, MVMObject *obj, MVMint64 index) {
+    MVMArrayBody *body = (MVMArrayBody *)OBJECT_BODY(obj);
+    MVMObject *found;
+
+    if (index < 0) {
+        index += body->elems;
+        if (index < 0)
+            MVM_exception_throw_adhoc(tc, "MVMArray: Index out of bounds");
+    }
+
+    if (index >= body->elems)
+        return 0;
+
+    return (MVMint64)body->slots.i64[body->start + index];
+}
+
 void *MVM_VMArray_devirtualize_ins_for_jit(MVMThreadContext *tc, MVMSTable *st, MVMSpeshIns *ins) {
     switch (ins->info->opcode) {
         case MVM_OP_atpos_o:
             if (((MVMArrayREPRData *)st->REPR_data)->slot_type != MVM_ARRAY_OBJ) {
                 return NULL;
             }
+            return vmarray_direct_atpos_o_to_o;
+            break;
+        case MVM_OP_atpos_i:
+            if (((MVMArrayREPRData *)st->REPR_data)->slot_type != MVM_ARRAY_I64) {
+                return NULL;
+            }
+            return vmarray_direct_atpos_i64_to_i;
             break;
         default:
             return NULL;
     }
 
-    return vmarray_direct_atpos_o_to_o;
 }
 
 /* Initializes the representation. */

src/jit/graph.c

@@ -871,10 +871,14 @@ static MVMint32 consume_reprop(MVMThreadContext *tc, MVMJitGraph *jg,
                         void *alternative_function = MVM_VMArray_devirtualize_ins_for_jit(tc, STABLE(type_facts->type), ins);
 
                         if (alternative_function != NULL) {
+                            MVMuint16 rv_type = op == MVM_OP_atpos_i ? MVM_JIT_RV_INT
+                                              : op == MVM_OP_atpos_o ? MVM_JIT_RV_PTR
+                                              : 0;
+
                             MVMJitCallArg args[] = { { MVM_JIT_INTERP_VAR,  MVM_JIT_INTERP_TC },
                                                      { MVM_JIT_REG_VAL,     invocant },
                                                      { MVM_JIT_REG_VAL,     value } };
-                            jg_append_call_c(tc, jg, alternative_function, 3, args, MVM_JIT_RV_PTR, dst);
+                            jg_append_call_c(tc, jg, alternative_function, 3, args, rv_type, dst);
                             MVM_spesh_graph_add_comment(tc, iter->graph, ins, "JIT: double-devirtualized");;
                             return 1;
                         }
@@ -894,7 +898,8 @@ static MVMint32 consume_reprop(MVMThreadContext *tc, MVMJitGraph *jg,
                                              op == MVM_OP_atpos_s || op == MVM_OP_atkey_s ? MVM_reg_str :
                                                                     MVM_reg_obj } };
                 jg_append_call_c(tc, jg, function, 7, args, MVM_JIT_RV_VOID, -1);
-                MVM_spesh_graph_add_comment(tc, iter->graph, ins, "JIT: devirtualized");;
+                MVM_spesh_graph_add_comment(tc, iter->graph, ins, "JIT: devirtualized");
+                }
                 return 1;
             }
             case MVM_OP_bindkey_i: