[wasm] Implement GetPossibleBreakpoints

src/wasm/wasm-objects.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/wasm/wasm-objects.h"
 #include "src/utils.h"
 
+#include "src/debug/debug-interface.h"
 #include "src/wasm/module-decoder.h"
 #include "src/wasm/wasm-module.h"
 #include "src/wasm/wasm-text.h"
 
 #define TRACE(...)                                      \
   do {                                                  \
     if (FLAG_trace_wasm_instances) PrintF(__VA_ARGS__); \
   } while (false)
 
 #define TRACE_CHAIN(instance)        \
@@ skipping 627 matching lines @@
 
   std::ostringstream disassembly_os;
   v8::debug::WasmDisassembly::OffsetTable offset_table;
 
   PrintWasmText(module(), module_bytes, static_cast<uint32_t>(func_index),
                 disassembly_os, &offset_table);
 
   return {disassembly_os.str(), std::move(offset_table)};
 }
 
+bool WasmCompiledModule::GetPossibleBreakpoints(
+    const v8::debug::Location& start, const v8::debug::Location& end,
+    std::vector<v8::debug::Location>* locations) const {
+  DisallowHeapAllocation no_gc;
+
+  std::vector<WasmFunction>& functions = module()->functions;
+  if (start.GetLineNumber() < 0 || start.GetColumnNumber() < 0 ||
+      (!end.IsEmpty() &&
+       (end.GetLineNumber() < 0 || end.GetColumnNumber() < 0)))
+    return false;
+
+  DCHECK(!functions.empty());

[titzer, 2016/12/19 15:44:58]

Isn't this check redundant with the check below? I.e. if functions.size() == 0,
then the first if below will fail.

[Clemens Hammacher, 2016/12/19 15:59:22]

True, it's not needed for the code below to work, so I will remove it.

+  // start_func_index, start_offset and end_func_index is inclusive.
+  // end_offset is exclusive.
+  // start_offset and end_offset are module-relative byte offsets.
+  uint32_t start_func_index = start.GetLineNumber();
+  if (start_func_index >= functions.size()) return false;
+  int start_func_len = functions[start_func_index].code_end_offset -
+                       functions[start_func_index].code_start_offset;
+  if (start.GetColumnNumber() > start_func_len) return false;
+  uint32_t start_offset =
+      functions[start_func_index].code_start_offset + start.GetColumnNumber();
+  uint32_t end_func_index;
+  uint32_t end_offset;
+  if (end.IsEmpty()) {
+    // Default: everything till the end of the Script.
+    end_func_index = static_cast<uint32_t>(functions.size() - 1);
+    end_offset = functions[end_func_index].code_end_offset;
+  } else {
+    // If end is specified: Use it and check for valid input.
+    end_func_index = static_cast<uint32_t>(end.GetLineNumber());
+
+    // Special case: Stop before the start of the next function. Change to: Stop
+    // at the end of the function before, such that we don't disassemble the
+    // next function also.
+    if (end.GetColumnNumber() == 0 && end_func_index > 0) {
+      --end_func_index;
+      end_offset = functions[end_func_index].code_end_offset;
+    } else {
+      if (end_func_index >= functions.size()) return false;
+      end_offset =
+          functions[end_func_index].code_start_offset + end.GetColumnNumber();
+      if (end_offset > functions[end_func_index].code_end_offset) return false;
+    }
+  }
+
+  AccountingAllocator alloc;
+  Zone tmp(&alloc, ZONE_NAME);
+  const byte* module_start = ptr_to_module_bytes()->GetChars();
+
+  for (uint32_t func_idx = start_func_index; func_idx <= end_func_index;
+       ++func_idx) {
+    WasmFunction& func = functions[func_idx];
+    if (func.code_start_offset == func.code_end_offset) continue;
+
+    AstLocalDecls locals(&tmp);
+    BytecodeIterator iterator(module_start + func.code_start_offset,
+                              module_start + func.code_end_offset, &locals);
+    DCHECK_LT(0u, locals.decls_encoded_size);
+    for (; iterator.has_next(); iterator.next()) {
+      uint32_t offset = func.code_start_offset + iterator.pc_offset();
+      if (offset >= end_offset) {
+        DCHECK_EQ(end_func_index, func_idx);
+        break;
+      }
+      if (offset < start_offset) continue;
+      locations->push_back(v8::debug::Location(func_idx, iterator.pc_offset()));
+    }
+  }
+  return true;
+}
+
 Handle<WasmInstanceWrapper> WasmInstanceWrapper::New(
     Isolate* isolate, Handle<WasmInstanceObject> instance) {
   Handle<FixedArray> array =
       isolate->factory()->NewFixedArray(kWrapperPropertyCount, TENURED);
   Handle<WasmInstanceWrapper> instance_wrapper(
       reinterpret_cast<WasmInstanceWrapper*>(*array), isolate);
   instance_wrapper->set_instance_object(instance, isolate);
   return instance_wrapper;
 }
 
@@ skipping 10 matching lines @@
       !array->get(kPreviousInstanceWrapper)->IsFixedArray())
     return false;
   return true;
 }
 
 void WasmInstanceWrapper::set_instance_object(Handle<JSObject> instance,
                                               Isolate* isolate) {
   Handle<WeakCell> cell = isolate->factory()->NewWeakCell(instance);
   set(kWrapperInstanceObject, *cell);
 }