[wasm] Provide better stack traces for asm.js code

src/wasm/wasm-module.h

Index: src/wasm/wasm-module.h
diff --git a/src/wasm/wasm-module.h b/src/wasm/wasm-module.h
index 466b15ba6735eb0e89a796dc36fe9248643e9eef..15152a87269c2e86dcf96365b24f3acd335056e0 100644
--- a/src/wasm/wasm-module.h
+++ b/src/wasm/wasm-module.h
@@ -35,19 +35,20 @@ const uint8_t kWasmFunctionTypeForm = 0x40;
 const uint8_t kWasmAnyFunctionTypeForm = 0x20;
 
 enum WasmSectionCode {
-  kUnknownSectionCode = 0,   // code for unknown sections
-  kTypeSectionCode = 1,      // Function signature declarations
-  kImportSectionCode = 2,    // Import declarations
-  kFunctionSectionCode = 3,  // Function declarations
-  kTableSectionCode = 4,     // Indirect function table and other tables
-  kMemorySectionCode = 5,    // Memory attributes
-  kGlobalSectionCode = 6,    // Global declarations
-  kExportSectionCode = 7,    // Exports
-  kStartSectionCode = 8,     // Start function declaration
-  kElementSectionCode = 9,   // Elements section
-  kCodeSectionCode = 10,     // Function code
-  kDataSectionCode = 11,     // Data segments
-  kNameSectionCode = 12,     // Name section (encoded as a string)
+  kUnknownSectionCode = 0,      // code for unknown sections
+  kTypeSectionCode = 1,         // Function signature declarations
+  kImportSectionCode = 2,       // Import declarations
+  kFunctionSectionCode = 3,     // Function declarations
+  kTableSectionCode = 4,        // Indirect function table and other tables
+  kMemorySectionCode = 5,       // Memory attributes
+  kGlobalSectionCode = 6,       // Global declarations
+  kExportSectionCode = 7,       // Exports
+  kStartSectionCode = 8,        // Start function declaration
+  kElementSectionCode = 9,      // Elements section
+  kCodeSectionCode = 10,        // Function code
+  kDataSectionCode = 11,        // Data segments
+  kNameSectionCode = 12,        // Name section (encoded as a string)
+  kAsmOffsetsSectionCode = 13,  // Asm.js offset table
 };
 
 inline bool IsValidSectionCode(uint8_t byte) {
@@ -394,6 +395,7 @@ class WasmCompiledModule : public FixedArray {
   MACRO(OBJECT, FixedArray, indirect_function_tables) \
   MACRO(OBJECT, SeqOneByteString, module_bytes)       \
   MACRO(OBJECT, ByteArray, function_names)            \
+  MACRO(OBJECT, Script, asm_js_script)                \
   MACRO(SMALL_NUMBER, uint32_t, min_memory_pages)     \
   MACRO(OBJECT, FixedArray, data_segments_info)       \
   MACRO(OBJECT, ByteArray, data_segments)             \
@@ -499,6 +501,17 @@ Handle<JSFunction> WrapExportCodeAsJSFunction(Isolate* isolate,
 // else.
 bool IsWasmObject(Object* object);
 
+// Check whether the wasm module was generated from asm.js code.
+bool WasmIsAsm(Object* wasm, Isolate* isolate);
+
+// Get the script for the asm.js origin of the wasm module.
+Handle<Script> GetAsmWasmScript(Handle<JSObject> wasm);
+
+// Get the asm.js source position for the given byte offset in the given
+// function.
+int GetAsmWasmSourcePosition(Handle<JSObject> wasm, int func_index,
+                             int byte_offset);
+
 // Update memory references of code objects associated with the module
 bool UpdateWasmModuleMemory(Handle<JSObject> object, Address old_start,
                             Address new_start, uint32_t old_size,
@@ -520,7 +533,7 @@ Handle<JSObject> CreateCompiledModuleObject(
 
 V8_EXPORT_PRIVATE MaybeHandle<JSObject> CreateModuleObjectFromBytes(
     Isolate* isolate, const byte* start, const byte* end, ErrorThrower* thrower,
-    ModuleOrigin origin);
+    ModuleOrigin origin, Handle<Script> asm_js_script);

[titzer, 2016/10/11 14:51:25]

What if, instead of using a special section, we just passed the encoded
Handle<ByteArray> directly here and have the asm-wasm builder build that byte
array? That skips an extra encoding/decoding step and all the associated logic.

[Clemens Hammacher, 2016/10/11 17:04:22]

That's a very nice idea. Done. It makes things a lot easier and improves
performance.

 
 V8_EXPORT_PRIVATE bool ValidateModuleBytes(Isolate* isolate, const byte* start,
                                            const byte* end,