[wasm] Handle non-asm-js case in WasmCompiledModule::GetAsmJsSourcePosition.

This hides more implementation details and simplifies callers.

R=ahaas@chromium.org

Bug: 
Change-Id: I4809611c55b810a3b0674713e12f3f17401e6c9c
Reviewed-on: https://chromium-review.googlesource.com/620713Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47434}

src/frames.cc

@@ -1229,16 +1229,11 @@ WASM_SUMMARY_DISPATCH(int, byte_offset)
 #undef WASM_SUMMARY_DISPATCH
 
 int FrameSummary::WasmFrameSummary::SourcePosition() const {
-  int offset = byte_offset();
   Handle<WasmCompiledModule> compiled_module(wasm_instance()->compiled_module(),
                                              isolate());
-  if (compiled_module->is_asm_js()) {
-    offset = WasmCompiledModule::GetAsmJsSourcePosition(
-        compiled_module, function_index(), offset, at_to_number_conversion());
-  } else {
-    offset += compiled_module->GetFunctionOffset(function_index());
-  }
-  return offset;
+  return WasmCompiledModule::GetSourcePosition(compiled_module,
+                                               function_index(), byte_offset(),
+                                               at_to_number_conversion());
 }
 
 Handle<Script> FrameSummary::WasmFrameSummary::script() const {

src/isolate.cc

@@ -1625,21 +1625,14 @@ bool Isolate::ComputeLocationFromStackTrace(MessageLocation* target,
       int func_index = elements->WasmFunctionIndex(i)->value();
       int code_offset = elements->Offset(i)->value();
       // TODO(wasm): Clean this up (bug 5007).
-      int pos = code_offset < 0
-                    ? (-1 - code_offset)
-                    : elements->Code(i)->SourcePosition(code_offset);
-      if (elements->IsAsmJsWasmFrame(i)) {
-        // For asm.js frames, make an additional translation step to get the
-        // asm.js source position.
-        bool at_to_number_conversion =
-            elements->Flags(i)->value() & FrameArray::kAsmJsAtNumberConversion;
-        pos = WasmCompiledModule::GetAsmJsSourcePosition(
-            compiled_module, func_index, pos, at_to_number_conversion);
-      } else {
-        // For pure wasm, make the function-local position module-relative by
-        // adding the function offset.
-        pos += compiled_module->GetFunctionOffset(func_index);
-      }
+      int byte_offset = code_offset < 0
+                            ? (-1 - code_offset)
+                            : elements->Code(i)->SourcePosition(code_offset);
+      bool is_at_number_conversion =
+          elements->IsAsmJsWasmFrame(i) &&
+          elements->Flags(i)->value() & FrameArray::kAsmJsAtNumberConversion;
+      byte pos = WasmCompiledModule::GetSourcePosition(
+          compiled_module, func_index, byte_offset, is_at_number_conversion);
       Handle<Script> script(compiled_module->script());
 
       *target = MessageLocation(script, pos, pos + 1);

src/messages.cc

@@ -757,7 +757,7 @@ int AsmJsWasmStackFrame::GetPosition() const {
   Handle<WasmCompiledModule> compiled_module(
       WasmInstanceObject::cast(*wasm_instance_)->compiled_module(), isolate_);
   DCHECK_LE(0, byte_offset);
-  return WasmCompiledModule::GetAsmJsSourcePosition(
+  return WasmCompiledModule::GetSourcePosition(
       compiled_module, wasm_func_index_, static_cast<uint32_t>(byte_offset),
       is_at_number_conversion_);
 }

src/wasm/wasm-objects.cc

@@ -1232,16 +1232,24 @@ Handle<ByteArray> GetDecodedAsmJsOffsetTable(
 
 }  // namespace
 
-int WasmCompiledModule::GetAsmJsSourcePosition(
+int WasmCompiledModule::GetSourcePosition(
     Handle<WasmCompiledModule> compiled_module, uint32_t func_index,
     uint32_t byte_offset, bool is_at_number_conversion) {
   Isolate* isolate = compiled_module->GetIsolate();
+  const WasmModule* module = compiled_module->module();
+
+  if (!module->is_asm_js()) {
+    // for non-asm.js modules, we just add the function's start offset
+    // to make a module-relative position.
+    return byte_offset + compiled_module->GetFunctionOffset(func_index);
+  }
+
+  // asm.js modules have an additional offset table that must be searched.
   Handle<ByteArray> offset_table =
       GetDecodedAsmJsOffsetTable(compiled_module, isolate);
 
-  DCHECK_LT(func_index, compiled_module->module()->functions.size());
-  uint32_t func_code_offset =
-      compiled_module->module()->functions[func_index].code.offset();
+  DCHECK_LT(func_index, module->functions.size());
+  uint32_t func_code_offset = module->functions[func_index].code.offset();
   uint32_t total_offset = func_code_offset + byte_offset;
 
   // Binary search for the total byte offset.

src/wasm/wasm-objects.h

@@ -512,11 +512,11 @@ class WasmCompiledModule : public FixedArray {
   // Returns true if the position is valid inside this module, false otherwise.
   bool GetPositionInfo(uint32_t position, Script::PositionInfo* info);
 
-  // Get the asm.js source position from a byte offset.
-  // Must only be called if the associated wasm object was created from asm.js.
-  static int GetAsmJsSourcePosition(Handle<WasmCompiledModule> compiled_module,
-                                    uint32_t func_index, uint32_t byte_offset,
-                                    bool is_at_number_conversion);
+  // Get the source position from a given function index and byte offset,
+  // for either asm.js or pure WASM modules.
+  static int GetSourcePosition(Handle<WasmCompiledModule> compiled_module,
+                               uint32_t func_index, uint32_t byte_offset,
+                               bool is_at_number_conversion);
 
   // Compute the disassembly of a wasm function.
   // Returns the disassembly string and a list of <byte_offset, line, column>