[wasm] Implement stepping in wasm code

src/compiler/wasm-compiler.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/compiler/wasm-compiler.h"
 
 #include <memory>
 
 #include "src/isolate-inl.h"
 
@@ skipping 2938 matching lines @@
   }
 
   // The return value is also passed via this buffer:
   DCHECK_GE(wasm::kV8MaxWasmFunctionReturns, sig->return_count());
   // TODO(wasm): Handle multi-value returns.
   DCHECK_EQ(1, wasm::kV8MaxWasmFunctionReturns);
   int return_size_bytes =
       sig->return_count() == 0 ? 0 : 1 << ElementSizeLog2Of(sig->GetReturn(0));
 
   // Get a stack slot for the arguments.
-  Node* arg_buffer = graph()->NewNode(jsgraph()->machine()->StackSlot(
-      std::max(args_size_bytes, return_size_bytes)));
+  Node* arg_buffer = args_size_bytes == 0 && return_size_bytes == 0
+                         ? jsgraph()->IntPtrConstant(0)
+                         : graph()->NewNode(jsgraph()->machine()->StackSlot(
+                               std::max(args_size_bytes, return_size_bytes)));
 
   // Now store all our arguments to the buffer.
   int param_index = 0;
   int offset = 0;
   for (int i = 0; i < wasm_count; i++) {
     Node* param = Param(param_index++);
     bool is_i64_as_two_params =
         jsgraph()->machine()->Is32() && sig->GetParam(i) == wasm::kWasmI64;
     MachineRepresentation param_rep =
         is_i64_as_two_params ? wasm::kWasmI32 : sig->GetParam(i);
@@ skipping 905 matching lines @@
                       Smi::FromInt(instruction.instr_offset));
     fn_protected->set(Code::kTrapDataSize * i + Code::kTrapLandingOffset,
                       Smi::FromInt(instruction.landing_offset));
   }
   return fn_protected;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8