[wasm] add atomic opcodes

src/wasm/ast-decoder.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/signature.h"
 
 #include "src/bit-vector.h"
 #include "src/flags.h"
 #include "src/handles.h"
 #include "src/zone/zone-containers.h"
@@ skipping 1128 matching lines @@
           case kSimdPrefix: {
             CHECK_PROTOTYPE_OPCODE(wasm_simd_prototype);
             len++;
             byte simd_index = *(pc_ + 1);
             opcode = static_cast<WasmOpcode>(opcode << 8 | simd_index);
             TRACE("  @%-4d #%02x #%02x:%-20s|", startrel(pc_), kSimdPrefix,
                   simd_index, WasmOpcodes::ShortOpcodeName(opcode));
             len += DecodeSimdOpcode(opcode);
             break;
           }
+          case kAtomicPrefix: {
+            if (!module_ || module_->origin != kAsmJsOrigin) {
+              error("Atomics are allowed only in AsmJs modules");
+              break;
+            }
+            if (!FLAG_wasm_atomics_prototype) {

[titzer, 2016/10/26 08:07:17]

You can use the macro for this check.

[aseemgarg, 2016/10/26 19:53:57]

The CHECK_PROTOTYPE_OPCODE checks that module origin is not asmjs. In this case
we want the origin to be asmjs. 
I can create a new Macro for that but since it is used at only one place yet,
don't really see the point. 

+              error("Invalid opcode (enable with --wasm_atomics_prototype)");
+              break;
+            }
+            len++;

[titzer, 2016/10/26 08:07:17]

Please don't do len++, but set len = 2.

[aseemgarg, 2016/10/26 19:53:57]

Done. Can you explain why?

+            byte atomic_index = checked_read_u8(pc_, 1, "atomic index");

[titzer, 2016/10/26 08:07:17]

"atomic opcode" instead of "atomic index"

[aseemgarg, 2016/10/26 19:53:57]

Done.

+            opcode = static_cast<WasmOpcode>(opcode << 8 | atomic_index);
+            sig = WasmOpcodes::AtomicSignature(opcode);
+            if (sig) {
+              BuildAtomicOperator(opcode);
+            }
+            break;
+          }
           default: {
             // Deal with special asmjs opcodes.
             if (module_ && module_->origin == kAsmJsOrigin) {
               sig = WasmOpcodes::AsmjsSignature(opcode);
               if (sig) {
                 BuildSimpleOperator(opcode, sig);
               }
             } else {
               error("Invalid opcode");
               return;
@@ skipping 162 matching lines @@
           TFNode* node = BUILD(SimdOp, opcode, inputs);
           Push(GetReturnType(sig), node);
         } else {
           error("invalid simd opcode");
         }
       }
     }
     return len;
   }
 
+  void BuildAtomicOperator(WasmOpcode opcode) { UNIMPLEMENTED(); }
+
   void DoReturn() {
     int count = static_cast<int>(sig_->return_count());
     TFNode** buffer = nullptr;
     if (build()) buffer = builder_->Buffer(count);
 
     // Pop return values off the stack in reverse order.
     for (int i = count - 1; i >= 0; i--) {
       Value val = Pop(i, sig_->GetReturn(i));
       if (buffer) buffer[i] = val.node;
     }
@@ skipping 657 matching lines @@
 BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, size_t num_locals,
                                            const byte* start, const byte* end) {
   FunctionBody body = {nullptr, nullptr, nullptr, start, end};
   WasmFullDecoder decoder(zone, nullptr, body);
   return decoder.AnalyzeLoopAssignmentForTesting(start, num_locals);
 }
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8