commit 24868a16c71d9a024101cce3b9ecc4b5ad038d07
author David Srbecky <dsrbecky@google.com> Fri Jan 29 18:59:56 2016 +0000
committer David Srbecky <dsrbecky@google.com> Wed Feb 03 10:17:42 2016 +0000
tree 9da04303cf2ba019933e9c2283d597da967c9481
parent 99e8e0b968e31b3757e329de560886b5aa7d6a13

Share DWARF .debug_abbrev sections.

Restructure the code so that all compilation units share the same
.debug_abbrev sections.  This deduplicates many of the abbrevs.

Change-Id: I7da07a8c850871786df52674183c16d574684729

compiler/dwarf/debug_abbrev_writer.h

diff --git a/compiler/dwarf/debug_abbrev_writer.h b/compiler/dwarf/debug_abbrev_writer.h
new file mode 100644
index 0000000..71367e8
--- /dev/null
+++ b/compiler/dwarf/debug_abbrev_writer.h
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_COMPILER_DWARF_DEBUG_ABBREV_WRITER_H_
+#define ART_COMPILER_DWARF_DEBUG_ABBREV_WRITER_H_
+
+#include <cstdint>
+#include <type_traits>
+#include <unordered_map>
+
+#include "base/casts.h"
+#include "base/stl_util.h"
+#include "dwarf/dwarf_constants.h"
+#include "dwarf/writer.h"
+#include "leb128.h"
+
+namespace art {
+namespace dwarf {
+
+// Writer for the .debug_abbrev.
+//
+// Abbreviations specify the format of entries in .debug_info.
+// Each entry specifies abbreviation code, which in turns
+// determines all the attributes and their format.
+// It is possible to think of them as type definitions.
+template <typename Vector = std::vector<uint8_t>>
+class DebugAbbrevWriter FINAL : private Writer<Vector> {
+  static_assert(std::is_same<typename Vector::value_type, uint8_t>::value, "Invalid value type");
+
+ public:
+  explicit DebugAbbrevWriter(Vector* buffer)
+      : Writer<Vector>(buffer),
+        current_abbrev_(buffer->get_allocator()) {
+    this->PushUint8(0);  // Add abbrev table terminator.
+  }
+
+  // Start abbreviation declaration.
+  void StartAbbrev(Tag tag) {
+    DCHECK(current_abbrev_.empty());
+    EncodeUnsignedLeb128(&current_abbrev_, tag);
+    has_children_offset_ = current_abbrev_.size();
+    current_abbrev_.push_back(0);  // Place-holder for DW_CHILDREN.
+  }
+
+  // Add attribute specification.
+  void AddAbbrevAttribute(Attribute name, Form type) {
+    EncodeUnsignedLeb128(&current_abbrev_, name);
+    EncodeUnsignedLeb128(&current_abbrev_, type);
+  }
+
+  // End abbreviation declaration and return its code.
+  // This will deduplicate abbreviations.
+  uint32_t EndAbbrev(Children has_children) {
+    DCHECK(!current_abbrev_.empty());
+    current_abbrev_[has_children_offset_] = has_children;
+    auto it = abbrev_codes_.insert(std::make_pair(std::move(current_abbrev_), NextAbbrevCode()));
+    uint32_t abbrev_code = it.first->second;
+    if (UNLIKELY(it.second)) {  // Inserted new entry.
+      const Vector& abbrev = it.first->first;
+      this->Pop();  // Remove abbrev table terminator.
+      this->PushUleb128(abbrev_code);
+      this->PushData(abbrev.data(), abbrev.size());
+      this->PushUint8(0);  // Attribute list end.
+      this->PushUint8(0);  // Attribute list end.
+      this->PushUint8(0);  // Add abbrev table terminator.
+    }
+    current_abbrev_.clear();
+    return abbrev_code;
+  }
+
+  // Get the next free abbrev code.
+  uint32_t NextAbbrevCode() {
+    return dchecked_integral_cast<uint32_t>(1 + abbrev_codes_.size());
+  }
+
+ private:
+  Vector current_abbrev_;
+  size_t has_children_offset_ = 0;
+  std::unordered_map<Vector, uint32_t, FNVHash<Vector> > abbrev_codes_;
+};
+
+}  // namespace dwarf
+}  // namespace art
+
+#endif  // ART_COMPILER_DWARF_DEBUG_ABBREV_WRITER_H_