[WASM] Implements catch for the wasm low level exception mechanism.

src/compiler/instruction-selector.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/instruction-selector.h"
 
 #include <limits>
 
 #include "src/base/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
@@ skipping 1689 matching lines @@
   InstructionOperand op =
       linkage()->ParameterHasSecondaryLocation(index)
           ? g.DefineAsDualLocation(
                 node, linkage()->GetParameterLocation(index),
                 linkage()->GetParameterSecondaryLocation(index))
           : g.DefineAsLocation(node, linkage()->GetParameterLocation(index));
 
   Emit(kArchNop, op);
 }
 
+namespace {
+LinkageLocation ExceptionLocation() {
+  return LinkageLocation::ForRegister(kReturnRegister0.code(),
+                                      MachineType::IntPtr());
+}
+}
 
 void InstructionSelector::VisitIfException(Node* node) {
   OperandGenerator g(this);
-  Node* call = node->InputAt(1);
-  DCHECK_EQ(IrOpcode::kCall, call->opcode());
-  const CallDescriptor* descriptor = CallDescriptorOf(call->op());
-  Emit(kArchNop, g.DefineAsLocation(node, descriptor->GetReturnLocation(0)));
+  DCHECK_EQ(IrOpcode::kCall, node->InputAt(1)->opcode());
+  Emit(kArchNop, g.DefineAsLocation(node, ExceptionLocation()));
 }
 
 
 void InstructionSelector::VisitOsrValue(Node* node) {
   OperandGenerator g(this);
   int index = OpParameter<int>(node);
   Emit(kArchNop,
        g.DefineAsLocation(node, linkage()->GetOsrValueLocation(index)));
 }
 
@@ skipping 368 matching lines @@
   return new (instruction_zone()) FrameStateDescriptor(
       instruction_zone(), state_info.type(), state_info.bailout_id(),
       state_info.state_combine(), parameters, locals, stack,
       state_info.shared_info(), outer_state);
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8