[turbofan] Introduce CheckIf simplified operator.

src/compiler/simplified-lowering.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/simplified-lowering.h"
 
 #include <limits>
 
 #include "src/address-map.h"
 #include "src/base/bits.h"
@@ skipping 1674 matching lines @@
           NodeProperties::ChangeOp(node, jsgraph_->common()->Call(desc));
         }
         return;
       }
 
       case IrOpcode::kCheckBounds: {
         VisitBinop(node, UseInfo::CheckedSigned32AsWord32(),
                    UseInfo::TruncatingWord32(), MachineRepresentation::kWord32);
         return;
       }
+      case IrOpcode::kCheckIf: {
+        ProcessInput(node, 0, UseInfo::Bool());
+        ProcessRemainingInputs(node, 1);
+        SetOutput(node, MachineRepresentation::kNone);
+        return;
+      }
       case IrOpcode::kCheckNumber: {
         if (InputIs(node, Type::Number())) {
           if (truncation.TruncatesToWord32()) {
             VisitUnop(node, UseInfo::TruncatingWord32(),
                       MachineRepresentation::kWord32);
           } else {
-            VisitUnop(node, UseInfo::TruncatingFloat64(),
-                      MachineRepresentation::kFloat64);
+            // TODO(jarin,bmeurer): We need to go to Tagged here, because
+            // otherwise we cannot distinguish the hole NaN (which might need to
+            // be treated as undefined). We should have a dedicated Type for
+            // that at some point, and maybe even a dedicated truncation.
+            VisitUnop(node, UseInfo::AnyTagged(),
+                      MachineRepresentation::kTagged);
           }
           if (lower()) DeferReplacement(node, node->InputAt(0));
         } else {
           VisitUnop(node, UseInfo::AnyTagged(), MachineRepresentation::kTagged);
         }
         return;
       }
       case IrOpcode::kCheckTaggedPointer: {
         if (InputCannotBe(node, Type::SignedSmall())) {
           VisitUnop(node, UseInfo::AnyTagged(), MachineRepresentation::kTagged);
@@ skipping 1384 matching lines @@
         isolate(), graph()->zone(), callable.descriptor(), 0, flags,
         Operator::kNoProperties);
     to_number_operator_.set(common()->Call(desc));
   }
   return to_number_operator_.get();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8