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

src/compiler/instruction-selector.cc

Index: src/compiler/instruction-selector.cc
diff --git a/src/compiler/instruction-selector.cc b/src/compiler/instruction-selector.cc
index f233cae5b5ac89e324c159daaf7fd71c54127ee1..64bfa6ecc5d24bbc98b2b1c7e30bb1d42d1f7887 100644
--- a/src/compiler/instruction-selector.cc
+++ b/src/compiler/instruction-selector.cc
@@ -1696,13 +1696,17 @@ void InstructionSelector::VisitParameter(Node* node) {
   Emit(kArchNop, op);
 }
 
+namespace {
+LinkageLocation ExceptionLocation() {

[bradnelson, 2016/09/27 04:25:56]

Could land this as a separate fix if you link (rolled in is fine too)?

[John, 2016/09/28 13:37:18]

Small enough, and mildly related to this CL... I'll land here.

+  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()));
 }