Fix issue 20190: Mark Uint32/Int32 typed data load to produce a Mint always

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/cpu.h"
 #include "vm/dart_entry.h"
@@ skipping 1641 matching lines @@
 
   array_cid = PrepareInlineIndexedOp(call,
                                      array_cid,
                                      &array,
                                      index,
                                      &cursor);
 
   intptr_t deopt_id = Isolate::kNoDeoptId;
   if ((array_cid == kTypedDataInt32ArrayCid) ||
       (array_cid == kTypedDataUint32ArrayCid)) {
-    // Prevent excessive deoptimization, assume full 32 bits used, and therefore
-    // generate Mint on 32-bit architectures.
-    deopt_id = (kSmiBits < 32) ? Isolate::kNoDeoptId : call->deopt_id();
+    // Deoptimization may be needed if result does not always fit in a Smi.
+    deopt_id = (kSmiBits >= 32) ? Isolate::kNoDeoptId : call->deopt_id();
   }
 
   // Array load and return.
   intptr_t index_scale = Instance::ElementSizeFor(array_cid);
   *last = new(I) LoadIndexedInstr(new(I) Value(array),
                                   new(I) Value(index),
                                   index_scale,
                                   array_cid,
                                   deopt_id,
                                   call->token_pos());
@@ skipping 1873 matching lines @@
   array_cid = PrepareInlineByteArrayViewOp(call,
                                            array_cid,
                                            view_cid,
                                            &array,
                                            index,
                                            &cursor);
 
   intptr_t deopt_id = Isolate::kNoDeoptId;
   if ((array_cid == kTypedDataInt32ArrayCid) ||
       (array_cid == kTypedDataUint32ArrayCid)) {
-    // Prevent excessive deoptimization, assume full 32 bits used, and therefore
-    // generate Mint on 32-bit architectures.
-    deopt_id = (kSmiBits < 32) ? Isolate::kNoDeoptId : call->deopt_id();
+    // Deoptimization may be needed if result does not always fit in a Smi.
+    deopt_id = (kSmiBits >= 32) ? Isolate::kNoDeoptId : call->deopt_id();
   }
 
   *last = new(I) LoadIndexedInstr(new(I) Value(array),
                                   new(I) Value(index),
                                   1,
                                   view_cid,
                                   deopt_id,
                                   call->token_pos());
   cursor = flow_graph()->AppendTo(
       cursor,
@@ skipping 6846 matching lines @@
 
   // Insert materializations at environment uses.
   for (intptr_t i = 0; i < exits_collector_.exits().length(); i++) {
     CreateMaterializationAt(
         exits_collector_.exits()[i], alloc, alloc->cls(), *slots);
   }
 }
 
 
 }  // namespace dart