Write DWARF strings inline and remove .debug_str section.

This means we no longer de-duplicate strings. Contra-intuitively this
saves space since removal of the indirection (4 bytes per string)
outweights the saving that we had from removal of duplicated strings.

The removal of buffering and deduplication also speeds up the processing.

Change-Id: Iee559094ed6180363e1665fbc79493e624b63435

2 files changed, 4 insertions, 78 deletions

diff --git a/compiler/dwarf/dedup_vector.h b/compiler/dwarf/dedup_vector.h
deleted file mode 100644
index 7fb21b76e2..0000000000
--- a/compiler/dwarf/dedup_vector.h
+++ /dev/null
@@ -1,67 +0,0 @@
-/*
- * Copyright (C) 2015 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_DEDUP_VECTOR_H_
-#define ART_COMPILER_DWARF_DEDUP_VECTOR_H_
-
-#include <vector>
-#include <unordered_map>
-
-namespace art {
-namespace dwarf {
-  class DedupVector {
-   public:
-    // Returns an offset to previously inserted identical block of data,
-    // or appends the data at the end of the vector and returns offset to it.
-    size_t Insert(const uint8_t* ptr, size_t num_bytes) {
-      // See http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
-      uint32_t hash = 2166136261u;
-      for (size_t i = 0; i < num_bytes; i++) {
-        hash = (hash ^ ptr[i]) * 16777619u;
-      }
-      // Try to find existing copy of the data.
-      const auto& range = hash_to_offset_.equal_range(hash);
-      for (auto it = range.first; it != range.second; ++it) {
-        const size_t offset = it->second;
-        if (offset + num_bytes <= vector_.size() &&
-            memcmp(vector_.data() + offset, ptr, num_bytes) == 0) {
-          return offset;
-        }
-      }
-      // Append the data at the end of the vector.
-      const size_t new_offset = vector_.size();
-      hash_to_offset_.emplace(hash, new_offset);
-      vector_.insert(vector_.end(), ptr, ptr + num_bytes);
-      return new_offset;
-    }
-
-    const std::vector<uint8_t>& Data() const { return vector_; }
-
-   private:
-    struct IdentityHash {
-      size_t operator()(uint32_t v) const { return v; }
-    };
-
-    // We store the full hash as the key to simplify growing of the table.
-    // It avoids storing or referencing the actual data in the hash-table.
-    std::unordered_multimap<uint32_t, size_t, IdentityHash> hash_to_offset_;
-
-    std::vector<uint8_t> vector_;
-  };
-}  // namespace dwarf
-}  // namespace art
-
-#endif  // ART_COMPILER_DWARF_DEDUP_VECTOR_H_
diff --git a/compiler/elf_writer_debug.cc b/compiler/elf_writer_debug.cc
index e1116fd6d2..d1f50073a0 100644
--- a/compiler/elf_writer_debug.cc
+++ b/compiler/elf_writer_debug.cc
@@ -27,7 +27,6 @@
 #include "compiled_method.h"
 #include "dex_file-inl.h"
 #include "driver/compiler_driver.h"
-#include "dwarf/dedup_vector.h"
 #include "dwarf/expression.h"
 #include "dwarf/headers.h"
 #include "dwarf/method_debug_info.h"
@@ -497,9 +496,9 @@ class DebugInfoWriter {
       const uintptr_t cu_size = compilation_unit.high_pc_ - compilation_unit.low_pc_;
 
       info_.StartTag(DW_TAG_compile_unit);
-      info_.WriteStrp(DW_AT_producer, owner_->WriteString("Android dex2oat"));
+      info_.WriteString(DW_AT_producer, "Android dex2oat");
       info_.WriteData1(DW_AT_language, DW_LANG_Java);
-      info_.WriteStrp(DW_AT_comp_dir, owner_->WriteString("$JAVA_SRC_ROOT"));
+      info_.WriteString(DW_AT_comp_dir, "$JAVA_SRC_ROOT");
       info_.WriteAddr(DW_AT_low_pc, text_address + compilation_unit.low_pc_);
       info_.WriteUdata(DW_AT_high_pc, dchecked_integral_cast<uint32_t>(cu_size));
       info_.WriteSecOffset(DW_AT_stmt_list, compilation_unit.debug_line_offset_);
@@ -630,7 +629,7 @@ class DebugInfoWriter {
 
     void Write(const ArrayRef<mirror::Class*>& types) SHARED_REQUIRES(Locks::mutator_lock_) {
       info_.StartTag(DW_TAG_compile_unit);
-      info_.WriteStrp(DW_AT_producer, owner_->WriteString("Android dex2oat"));
+      info_.WriteString(DW_AT_producer, "Android dex2oat");
       info_.WriteData1(DW_AT_language, DW_LANG_Java);
 
       // Base class references to be patched at the end.
@@ -968,7 +967,7 @@ class DebugInfoWriter {
    private:
     void WriteName(const char* name) {
       if (name != nullptr) {
-        info_.WriteStrp(DW_AT_name, owner_->WriteString(name));
+        info_.WriteString(DW_AT_name, name);
       }
     }
 
@@ -1154,21 +1153,15 @@ class DebugInfoWriter {
     builder_->WritePatches(".debug_info.oat_patches",
                            ArrayRef<const uintptr_t>(debug_info_patches_));
     builder_->WriteSection(".debug_abbrev", &debug_abbrev_buffer_);
-    builder_->WriteSection(".debug_str", &debug_str_.Data());
     builder_->WriteSection(".debug_loc", &debug_loc_);
     builder_->WriteSection(".debug_ranges", &debug_ranges_);
   }
 
  private:
-  size_t WriteString(const char* str) {
-    return debug_str_.Insert(reinterpret_cast<const uint8_t*>(str), strlen(str) + 1);
-  }
-
   ElfBuilder<ElfTypes>* builder_;
   std::vector<uintptr_t> debug_info_patches_;
   std::vector<uint8_t> debug_abbrev_buffer_;
   DebugAbbrevWriter<> debug_abbrev_;
-  DedupVector debug_str_;
   std::vector<uint8_t> debug_loc_;
   std::vector<uint8_t> debug_ranges_;