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where possible, encode symtab names with 7 bits per char instead of 8. This 

shaves 110K off kc++ to 3514K.  Before:

  Block ID #14 (VALUE_SYMTAB):
      Num Instances: 2345
         Total Size: 1.50425e+07b/1.88031e+06B/470077W
       Average Size: 6414.69b/801.837B/200.459W
          % of file: 51.8057
  Tot/Avg SubBlocks: 0/0
    Tot/Avg Abbrevs: 2345/1
    Tot/Avg Records: 120924/51.5667
      % Abbrev Recs: 85.1791

after:

  Block ID #14 (VALUE_SYMTAB):
      Num Instances: 2345
         Total Size: 1.41229e+07b/1.76536e+06B/441341W
       Average Size: 6022.56b/752.82B/188.205W
          % of file: 50.2295
  Tot/Avg SubBlocks: 0/0
    Tot/Avg Abbrevs: 4690/2
    Tot/Avg Records: 120924/51.5667
      % Abbrev Recs: 85.1791

llvm-svn: 36758
This commit is contained in:
Chris Lattner 2007-05-04 20:52:02 +00:00
parent 0c7704f23c
commit 4d92598ab0
1 changed files with 45 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

56
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
View File

@ -25,7 +25,17 @@
#include "llvm/Support/MathExtras.h"
using namespace llvm;
static const unsigned CurVersion = 0;
/// These are manifest constants used by the bitcode writer. They do not need to
/// be kept in sync with the reader, but need to be consistent within this file.
enum {
CurVersion = 0,
// VALUE_SYMTAB_BLOCK abbrev id's.
VST_ENTRY_8_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
VST_ENTRY_7_ABBREV
};
static unsigned GetEncodedCastOpcode(unsigned Opcode) {
switch (Opcode) {
@ -703,13 +713,25 @@ static void WriteValueSymbolTable(const ValueSymbolTable &VST,
if (VST.empty()) return;
Stream.EnterSubblock(bitc::VALUE_SYMTAB_BLOCK_ID, 3);
// 8-bit fixed width VST_ENTRY strings.
BitCodeAbbrev *Abbv = new BitCodeAbbrev();
Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
unsigned AbbrevID = Stream.EmitAbbrev(Abbv);
{ // 8-bit fixed width VST_ENTRY strings.
BitCodeAbbrev *Abbv = new BitCodeAbbrev();
Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
if (Stream.EmitAbbrev(Abbv) != VST_ENTRY_8_ABBREV)
assert(0 && "Unexpected abbrev ordering!");
}
{ // 7-bit fixed width VST_ENTRY strings.
BitCodeAbbrev *Abbv = new BitCodeAbbrev();
Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
if (Stream.EmitAbbrev(Abbv) != VST_ENTRY_7_ABBREV)
assert(0 && "Unexpected abbrev ordering!");
}
// FIXME: Set up the abbrev, we know how many values there are!
@ -718,6 +740,18 @@ static void WriteValueSymbolTable(const ValueSymbolTable &VST,
for (ValueSymbolTable::const_iterator SI = VST.begin(), SE = VST.end();
SI != SE; ++SI) {
const ValueName &Name = *SI;
// Figure out the encoding to use for the name.
bool is7Bit = true;
for (unsigned i = 0, e = Name.getKeyLength(); i != e; ++i)
if ((unsigned char)Name.getKeyData()[i] & 128) {
is7Bit = false;
break;
}
unsigned AbbrevToUse = 0;
// VST_ENTRY: [valueid, namelen, namechar x N]
@ -727,12 +761,12 @@ static void WriteValueSymbolTable(const ValueSymbolTable &VST,
Code = bitc::VST_CODE_BBENTRY;
} else {
Code = bitc::VST_CODE_ENTRY;
AbbrevToUse = AbbrevID;
AbbrevToUse = is7Bit ? VST_ENTRY_7_ABBREV : VST_ENTRY_8_ABBREV;
}
NameVals.push_back(VE.getValueID(SI->getValue()));
for (const char *P = SI->getKeyData(),
*E = SI->getKeyData()+SI->getKeyLength(); P != E; ++P)
for (const char *P = Name.getKeyData(),
*E = Name.getKeyData()+Name.getKeyLength(); P != E; ++P)
NameVals.push_back((unsigned char)*P);
// Emit the finished record.