[wasm] Move and refactor position to location translation

The GetPositionInfo function only operates on WasmCompiledModule, so it
should be a method of that class.
This CL also splits the method in two, such that I can reuse the
GetContainingFunction method for breakpoint support.

R=titzer@chromium.org
BUG=chromium:613110

Review-Url: https://codereview.chromium.org/2521293002
Cr-Commit-Position: refs/heads/master@{#41191}

src/objects.cc

@@ -13474,8 +13474,8 @@ bool Script::GetPositionInfo(int position, PositionInfo* info,
     Handle<WasmCompiledModule> compiled_module(
         WasmCompiledModule::cast(wasm_compiled_module()));
     DCHECK_LE(0, position);
-    return wasm::GetPositionInfo(compiled_module,
-                                 static_cast<uint32_t>(position), info);
+    return compiled_module->GetPositionInfo(static_cast<uint32_t>(position),
+                                            info);
   }
 
   if (line_ends()->IsUndefined(GetIsolate())) {

src/wasm/wasm-module.cc

@@ -767,35 +767,6 @@ int wasm::GetFunctionCodeOffset(Handle<WasmCompiledModule> compiled_module,
   return GetFunctionOffsetAndLength(compiled_module, func_index).first;
 }
 
-bool wasm::GetPositionInfo(Handle<WasmCompiledModule> compiled_module,
-                           uint32_t position, Script::PositionInfo* info) {
-  std::vector<WasmFunction>& functions = compiled_module->module()->functions;
-
-  // Binary search for a function containing the given position.
-  int left = 0;                                    // inclusive
-  int right = static_cast<int>(functions.size());  // exclusive
-  if (right == 0) return false;
-  while (right - left > 1) {
-    int mid = left + (right - left) / 2;
-    if (functions[mid].code_start_offset <= position) {
-      left = mid;
-    } else {
-      right = mid;
-    }
-  }
-  // If the found entry does not contains the given position, return false.
-  WasmFunction& func = functions[left];
-  if (position < func.code_start_offset || position >= func.code_end_offset) {
-    return false;
-  }
-
-  info->line = left;
-  info->column = position - func.code_start_offset;
-  info->line_start = func.code_start_offset;
-  info->line_end = func.code_end_offset;
-  return true;
-}
-
 WasmModule::WasmModule(Zone* owned, const byte* module_start)
     : owned_zone(owned),
       module_start(module_start),

src/wasm/wasm-module.h

@@ -413,11 +413,6 @@ V8_EXPORT_PRIVATE bool ValidateModuleBytes(Isolate* isolate, const byte* start,
 int GetFunctionCodeOffset(Handle<WasmCompiledModule> compiled_module,
                           int func_index);
 
-// Translate from byte offset in the module to function number and byte offset
-// within that function, encoded as line and column in the position info.
-bool GetPositionInfo(Handle<WasmCompiledModule> compiled_module,
-                     uint32_t position, Script::PositionInfo* info);
-
 // Assumed to be called with a code object associated to a wasm module instance.
 // Intended to be called from runtime functions.
 // Returns nullptr on failing to get owning instance.

src/wasm/wasm-objects.cc

@@ -385,3 +385,42 @@ int WasmCompiledModule::GetFunctionOffset(uint32_t func_index) const {
             functions[func_index].code_start_offset);
   return static_cast<int>(functions[func_index].code_start_offset);
 }
+
+int WasmCompiledModule::GetContainingFunction(uint32_t byte_offset) const {
+  std::vector<WasmFunction>& functions = module()->functions;
+
+  // Binary search for a function containing the given position.
+  int left = 0;                                    // inclusive
+  int right = static_cast<int>(functions.size());  // exclusive
+  if (right == 0) return false;
+  while (right - left > 1) {
+    int mid = left + (right - left) / 2;
+    if (functions[mid].code_start_offset <= byte_offset) {
+      left = mid;
+    } else {
+      right = mid;
+    }
+  }
+  // If the found function does not contains the given position, return -1.
+  WasmFunction& func = functions[left];
+  if (byte_offset < func.code_start_offset ||
+      byte_offset >= func.code_end_offset) {
+    return -1;
+  }
+
+  return left;
+}
+
+bool WasmCompiledModule::GetPositionInfo(uint32_t position,
+                                         Script::PositionInfo* info) {
+  int func_index = GetContainingFunction(position);
+  if (func_index < 0) return false;
+
+  WasmFunction& function = module()->functions[func_index];
+
+  info->line = func_index;
+  info->column = position - function.code_start_offset;
+  info->line_start = function.code_start_offset;
+  info->line_end = function.code_end_offset;
+  return true;
+}

src/wasm/wasm-objects.h

@@ -276,6 +276,16 @@ class WasmCompiledModule : public FixedArray {
   // Returns -1 if the function index is invalid.
   int GetFunctionOffset(uint32_t func_index) const;
 
+  // Returns the function containing the given byte offset.
+  // Returns -1 if the byte offset is not contained in any function of this
+  // module.
+  int GetContainingFunction(uint32_t byte_offset) const;
+
+  // Translate from byte offset in the module to function number and byte offset
+  // within that function, encoded as line and column in the position info.
+  // Returns true if the position is valid inside this module, false otherwise.
+  bool GetPositionInfo(uint32_t position, Script::PositionInfo* info);
+
  private:
   void InitId();