[machine-operator-reducer] fix float truncation

src/compiler/machine-operator-reducer.cc

Index: src/compiler/machine-operator-reducer.cc
diff --git a/src/compiler/machine-operator-reducer.cc b/src/compiler/machine-operator-reducer.cc
index 5951fb612a9f75feb3f456f840a8c2d364cb80a2..04af8d4a431a9ca9c9e875a05380359084192d03 100644
--- a/src/compiler/machine-operator-reducer.cc
+++ b/src/compiler/machine-operator-reducer.cc
@@ -648,7 +648,18 @@ Reduction MachineOperatorReducer::ReduceTruncateFloat64ToInt32(Node* node) {
   Float64Matcher m(node->InputAt(0));
   if (m.HasValue()) return ReplaceInt32(DoubleToInt32(m.Value()));
   if (m.IsChangeInt32ToFloat64()) return Replace(m.node()->InputAt(0));
-  if (m.IsRoundInt64ToFloat64()) return Replace(m.node()->InputAt(0));
+  if (m.IsRoundInt64ToFloat64()) {
+    Node* value = m.node()->InputAt(0);
+    Type* type = NodeProperties::GetType(value);
+    Type::RangeType* range = type->GetRange();
+
+    // Rounding int64 to float64 should not lose precision
+    if (range != nullptr && range->Min() >= 0 &&
+        range->Max() <= 0xFFFFFFFFFFFFFULL) {
+      return Replace(
+          graph()->NewNode(machine()->TruncateInt64ToInt32(), value));
+    }
+  }
   if (m.IsPhi()) {
     Node* const phi = m.node();
     DCHECK_EQ(kRepFloat64, RepresentationOf(OpParameter<MachineType>(phi)));