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add a char6 abbrev for bbnames and value names. This represents each character 

with 6 bits where possible.  This shrinks kc++ from 3324164B to 3183584B.  The
old VST was:

  Block ID #14 (VALUE_SYMTAB):
         Total Size: 1.26713e+07b/1.58391e+06B/395978W
       Average Size: 5403.53b/675.442B/168.86W
          % of file: 47.6484

The new one is:

  Block ID #14 (VALUE_SYMTAB):
         Total Size: 1.15467e+07b/1.44334e+06B/360834W
       Average Size: 4923.96b/615.495B/153.874W
          % of file: 45.3368

This is 11% smaller than the VST in the bytecode format.

llvm-svn: 36771
This commit is contained in:
Chris Lattner 2007-05-05 01:26:50 +00:00
parent 7dce4b04ca
commit e760d6f4c1
1 changed files with 30 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
View File

@ -33,8 +33,8 @@ enum {
// VALUE_SYMTAB_BLOCK abbrev id's.
VST_ENTRY_8_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
VST_ENTRY_7_ABBREV,
VST_BBENTRY_7_ABBREV
VST_ENTRY_6_ABBREV,
VST_BBENTRY_6_ABBREV
};
@ -712,7 +712,7 @@ static void WriteValueSymbolTable(const ValueSymbolTable &VST,
const ValueEnumerator &VE,
BitstreamWriter &Stream) {
if (VST.empty()) return;
Stream.EnterSubblock(bitc::VALUE_SYMTAB_BLOCK_ID, 3);
Stream.EnterSubblock(bitc::VALUE_SYMTAB_BLOCK_ID, 4);
// FIXME: Set up the abbrev, we know how many values there are!
// FIXME: We know if the type names can use 7-bit ascii.
@ -725,12 +725,16 @@ static void WriteValueSymbolTable(const ValueSymbolTable &VST,
// 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) {
bool isChar6 = true;
for (const char *C = Name.getKeyData(), *E = C+Name.getKeyLength();
C != E; ++C) {
if (isChar6)
isChar6 = BitCodeAbbrevOp::isChar6(*C);
if ((unsigned char)*C & 128) {
is7Bit = false;
break;
break; // don't bother scanning the rest.
}
}
unsigned AbbrevToUse = VST_ENTRY_8_ABBREV;
@ -739,10 +743,14 @@ static void WriteValueSymbolTable(const ValueSymbolTable &VST,
unsigned Code;
if (isa<BasicBlock>(SI->getValue())) {
Code = bitc::VST_CODE_BBENTRY;
if (is7Bit) AbbrevToUse = VST_BBENTRY_7_ABBREV;
if (isChar6)
AbbrevToUse = VST_BBENTRY_6_ABBREV;
} else {
Code = bitc::VST_CODE_ENTRY;
if (is7Bit) AbbrevToUse = VST_ENTRY_7_ABBREV;
if (isChar6)
AbbrevToUse = VST_ENTRY_6_ABBREV;
else if (is7Bit)
AbbrevToUse = VST_ENTRY_7_ABBREV;
}
NameVals.push_back(VE.getValueID(SI->getValue()));
@ -910,14 +918,24 @@ static void WriteBlockInfo(BitstreamWriter &Stream) {
Abbv) != VST_ENTRY_7_ABBREV)
assert(0 && "Unexpected abbrev ordering!");
}
{ // 7-bit fixed width VST_BBENTRY strings.
{ // 6-bit char6 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::Char6));
if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
Abbv) != VST_ENTRY_6_ABBREV)
assert(0 && "Unexpected abbrev ordering!");
}
{ // 6-bit char6 VST_BBENTRY strings.
BitCodeAbbrev *Abbv = new BitCodeAbbrev();
Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_BBENTRY));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
Abbv) != VST_BBENTRY_7_ABBREV)
Abbv) != VST_BBENTRY_6_ABBREV)
assert(0 && "Unexpected abbrev ordering!");
}