commit f15ceeb7841ef97c24a0b7708732756d433c5d0d
author Dmitriy Ivanov <dimitry@google.com> Tue Apr 21 15:03:04 2015 -0700
committer Dmitriy Ivanov <dimitry@google.com> Wed Apr 22 12:58:38 2015 -0700
tree b7888d48605d20313d6d417109da27043afc7995
parent 913fe559f69395aaf160653c1d3994df3272810b

Always use signed leb128 encoding

 According to runs on /system/lib there using
 unsigned leb128 does not save us any additional
 space. In order to keep packing as simple as
 possible switch to using signed leb128 for
 everything.

Bug: http://b/18051137
Change-Id: I1a47cb9eb2175895b3c3f7c13b4c6b1060de86c0

tools/relocation_packer/src/packer.cc

diff --git a/tools/relocation_packer/src/packer.cc b/tools/relocation_packer/src/packer.cc
index 8e30612..433611f 100644
--- a/tools/relocation_packer/src/packer.cc
+++ b/tools/relocation_packer/src/packer.cc
@@ -9,7 +9,6 @@
 #include "debug.h"
 #include "delta_encoder.h"
 #include "elf_traits.h"
-#include "leb128.h"
 #include "sleb128.h"
 
 namespace relocation_packer {
@@ -28,32 +27,17 @@
     return;
 
   Sleb128Encoder<typename ELF::Addr> sleb128_encoder;
-  Leb128Encoder<typename ELF::Addr> leb128_encoder;
 
-  std::vector<uint8_t> leb128_packed;
   std::vector<uint8_t> sleb128_packed;
 
-  leb128_encoder.EnqueueAll(packed_words);
-  leb128_encoder.GetEncoding(&leb128_packed);
-
   sleb128_encoder.EnqueueAll(packed_words);
   sleb128_encoder.GetEncoding(&sleb128_packed);
 
-  // TODO (simonb): Estimate savings on current android system image and consider using
-  // one encoder for all packed relocations to reduce complexity.
-  if (leb128_packed.size() <= sleb128_packed.size()) {
-    packed->push_back('A');
-    packed->push_back('P');
-    packed->push_back('U');
-    packed->push_back('2');
-    packed->insert(packed->end(), leb128_packed.begin(), leb128_packed.end());
-  } else {
-    packed->push_back('A');
-    packed->push_back('P');
-    packed->push_back('S');
-    packed->push_back('2');
-    packed->insert(packed->end(), sleb128_packed.begin(), sleb128_packed.end());
-  }
+  packed->push_back('A');
+  packed->push_back('P');
+  packed->push_back('S');
+  packed->push_back('2');
+  packed->insert(packed->end(), sleb128_packed.begin(), sleb128_packed.end());
 }
 
 // Unpack relative relocations from a run-length encoded packed
@@ -67,16 +51,11 @@
   CHECK(packed.size() > 4 &&
         packed[0] == 'A' &&
         packed[1] == 'P' &&
-        (packed[2] == 'U' || packed[2] == 'S') &&
+        packed[2] == 'S' &&
         packed[3] == '2');
 
-  if (packed[2] == 'U') {
-    Leb128Decoder<typename ELF::Addr> decoder(packed, 4);
-    decoder.DequeueAll(&packed_words);
-  } else {
-    Sleb128Decoder<typename ELF::Addr> decoder(packed, 4);
-    decoder.DequeueAll(&packed_words);
-  }
+  Sleb128Decoder<typename ELF::Addr> decoder(packed, 4);
+  decoder.DequeueAll(&packed_words);
 
   RelocationDeltaCodec<ELF> codec;
   codec.Decode(packed_words, relocations);