[wasm] Implement AST printing into an ostream

src/wasm/ast-decoder.h

 // 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.
 
 #ifndef V8_WASM_AST_DECODER_H_
 #define V8_WASM_AST_DECODER_H_
 
+#include <functional>
+
 #include "src/signature.h"
 #include "src/wasm/decoder.h"
 #include "src/wasm/wasm-opcodes.h"
 #include "src/wasm/wasm-result.h"
 
 namespace v8 {
 namespace internal {
 
 class BitVector;  // forward declaration
 
@@ skipping 186 matching lines @@
 typedef compiler::WasmGraphBuilder TFBuilder;
 struct ModuleEnv;  // forward declaration of module interface.
 
 // All of the various data structures necessary to decode a function body.
 struct FunctionBody {
   ModuleEnv* module;  // module environment
   FunctionSig* sig;   // function signature
   const byte* base;   // base of the module bytes, for error reporting
   const byte* start;  // start of the function body
   const byte* end;    // end of the function body
+  static FunctionBody ForTesting(const byte* start, const byte* end) {

[titzer, 2016/06/10 10:57:40]

Can you please move this out to the top level? (style guide recommends no
functions within structs).

[Clemens Hammacher, 2016/06/13 09:45:17]

Done.
Not sure though if style guide really advises against this. It sais for structs:
Methods should not provide behavior but should only be used to set up the data
members, e.g., constructor, destructor, Initialize(), Reset(), Validate().

+    return {nullptr, nullptr, start, start, end};
+  }
 };
 
 struct Tree;
 typedef Result<Tree*> TreeResult;
 
 std::ostream& operator<<(std::ostream& os, const Tree& tree);
 
 TreeResult VerifyWasmCode(base::AccountingAllocator* allocator,
                           FunctionBody& body);
 TreeResult BuildTFGraph(base::AccountingAllocator* allocator,
                         TFBuilder* builder, FunctionBody& body);
-void PrintAst(base::AccountingAllocator* allocator, FunctionBody& body);
+bool PrintAst(base::AccountingAllocator* allocator, const FunctionBody& body,
+              std::ostream& os,
+              std::function<void(uint32_t)> instruction_callback = {});

[titzer, 2016/06/10 10:57:40]

There isn't a usecase for the instruction_callback function yet. (I assume there
is one in a CL based on this one).

Can we avoid a callback and instead return a map from byte index to line (since
that is what I assume this is being used for)?

[Clemens Hammacher, 2016/06/13 09:45:17]

Done.

 
 // A simplified form of AST printing, e.g. from a debugger.
 void PrintAstForDebugging(const byte* start, const byte* end);
 
 inline TreeResult VerifyWasmCode(base::AccountingAllocator* allocator,
                                  ModuleEnv* module, FunctionSig* sig,
                                  const byte* start, const byte* end) {
   FunctionBody body = {module, sig, nullptr, start, end};
   return VerifyWasmCode(allocator, body);
 }
@@ skipping 29 matching lines @@
 int OpcodeLength(const byte* pc, const byte* end);
 
 // Computes the arity (number of sub-nodes) of the opcode at the given address.
 int OpcodeArity(const byte* pc, const byte* end);
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_AST_DECODER_H_