[wasm] Initialize the root register for WASM tests.

src/compiler/c-linkage.cc

 // Copyright 2015 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/assembler.h"
 #include "src/macro-assembler.h"
 
 #include "src/compiler/linkage.h"
 
 #include "src/zone.h"
@@ skipping 115 matching lines @@
 // ===========================================================================
 // == unknown ================================================================
 // ===========================================================================
 #define UNSUPPORTED_C_LINKAGE 1
 #endif
 }  // namespace
 
 
 // General code uses the above configuration data.
 CallDescriptor* Linkage::GetSimplifiedCDescriptor(
-    Zone* zone, const MachineSignature* msig) {
+    Zone* zone, const MachineSignature* msig, bool set_initialize_root_flag) {
   LocationSignature::Builder locations(zone, msig->return_count(),
                                        msig->parameter_count());
 #if 0  // TODO(titzer): instruction selector tests break here.
   // Check the types of the signature.
   // Currently no floating point parameters or returns are allowed because
   // on x87 and ia32, the FP top of stack is involved.
 
   for (size_t i = 0; i < msig->return_count(); i++) {
     MachineType type = RepresentationOf(msig->GetReturn(i));
     CHECK(type != kRepFloat32 && type != kRepFloat64);
@@ skipping 66 matching lines @@
   return new (zone) CallDescriptor(  // --
       CallDescriptor::kCallAddress,  // kind
       target_type,                   // target MachineType
       target_loc,                    // target location
       msig,                          // machine_sig
       locations.Build(),             // location_sig
       0,                             // stack_parameter_count
       Operator::kNoProperties,       // properties
       kCalleeSaveRegisters,          // callee-saved registers
       kCalleeSaveFPRegisters,        // callee-saved fp regs
-      CallDescriptor::kNoFlags,      // flags
+      set_initialize_root_flag ?     // flags
+          CallDescriptor::kInitializeRootRegister
+                               : CallDescriptor::kNoFlags,
       "c-call");
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8