[turbofan] Introduce TruncateTaggedToBit operator for ToBoolean truncation.

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 1325 matching lines @@
       case IrOpcode::kSelect:
         return VisitSelect(node, truncation, lowering);
       case IrOpcode::kPhi:
         return VisitPhi(node, truncation, lowering);
       case IrOpcode::kCall:
         return VisitCall(node, lowering);
 
       //------------------------------------------------------------------
       // JavaScript operators.
       //------------------------------------------------------------------
+      case IrOpcode::kJSToBoolean: {
+        if (truncation.IsUsedAsBool()) {
+          ProcessInput(node, 0, UseInfo::Bool());
+          ProcessInput(node, 1, UseInfo::None());
+          SetOutput(node, MachineRepresentation::kBit);
+          if (lower()) DeferReplacement(node, node->InputAt(0));
+        } else {
+          VisitInputs(node);
+          SetOutput(node, MachineRepresentation::kTagged);
+        }
+        return;
+      }
       case IrOpcode::kJSToNumber: {
         VisitInputs(node);
         // TODO(bmeurer): Optimize somewhat based on input type?
         if (truncation.IsUsedAsWord32()) {
           SetOutput(node, MachineRepresentation::kWord32);
           if (lower()) lowering->DoJSToNumberTruncatesToWord32(node, this);
         } else if (truncation.IsUsedAsFloat64()) {
           SetOutput(node, MachineRepresentation::kFloat64);
           if (lower()) lowering->DoJSToNumberTruncatesToFloat64(node, this);
         } else {
@@ skipping 1102 matching lines @@
       case IrOpcode::kProjection:
       case IrOpcode::kObjectState:
 // All JavaScript operators except JSToNumber have uniform handling.
 #define OPCODE_CASE(name) case IrOpcode::k##name:
         JS_SIMPLE_BINOP_LIST(OPCODE_CASE)
         JS_OTHER_UNOP_LIST(OPCODE_CASE)
         JS_OBJECT_OP_LIST(OPCODE_CASE)
         JS_CONTEXT_OP_LIST(OPCODE_CASE)
         JS_OTHER_OP_LIST(OPCODE_CASE)
 #undef OPCODE_CASE
-      case IrOpcode::kJSToBoolean:
       case IrOpcode::kJSToInteger:
       case IrOpcode::kJSToLength:
       case IrOpcode::kJSToName:
       case IrOpcode::kJSToObject:
       case IrOpcode::kJSToString:
         VisitInputs(node);
         // Assume the output is tagged.
         return SetOutput(node, MachineRepresentation::kTagged);
 
       default:
@@ skipping 759 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