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Implement support for globally associating abbrevs with block IDs, which

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relieves us from having to emit the abbrevs into each instance of the block.
This shrinks kc.bit from 3368K to 3333K, but will be a more significant win
once instructions are abbreviated.

The VST went from:

  Block ID #14 (VALUE_SYMTAB):
      Num Instances: 2345
         Total Size: 1.29508e+07b/1.61885e+06B/404713W
       Average Size: 5522.73b/690.342B/172.585W
          % of file: 48.0645
  Tot/Avg SubBlocks: 0/0
    Tot/Avg Abbrevs: 7035/3
    Tot/Avg Records: 120924/51.5667
      % Abbrev Recs: 100

to:

  Block ID #14 (VALUE_SYMTAB):
      Num Instances: 2345
         Total Size: 1.26713e+07b/1.58391e+06B/395978W
       Average Size: 5403.53b/675.442B/168.86W
          % of file: 47.5198
  Tot/Avg SubBlocks: 0/0
    Tot/Avg Abbrevs: 0/0
    Tot/Avg Records: 120924/51.5667
      % Abbrev Recs: 100

because we didn't emit the same 3 abbrevs 2345 times :)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36767 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2007-05-05 00:17:00 +00:00
parent a8e9562906
commit e17b658c79
5 changed files with 264 additions and 64 deletions
Download Patch File Download Diff File Expand all files Collapse all files

118
include/llvm/Bitcode/BitstreamWriter.h
View File

@ -29,10 +29,14 @@ class BitstreamWriter {
/// CurValue - The current value. Only bits < CurBit are valid.
uint32_t CurValue;
// CurCodeSize - This is the declared size of code values used for the current
// block, in bits.
/// CurCodeSize - This is the declared size of code values used for the
/// current block, in bits.
unsigned CurCodeSize;
/// BlockInfoCurBID - When emitting a BLOCKINFO_BLOCK, this is the currently
/// selected BLOCK ID.
unsigned BlockInfoCurBID;
/// CurAbbrevs - Abbrevs installed at in this block.
std::vector<BitCodeAbbrev*> CurAbbrevs;
@ -46,6 +50,14 @@ class BitstreamWriter {
/// BlockScope - This tracks the current blocks that we have entered.
std::vector<Block> BlockScope;
/// BlockInfo - This contains information emitted to BLOCKINFO_BLOCK blocks.
/// These describe abbreviations that all blocks of the specified ID inherit.
struct BlockInfo {
unsigned BlockID;
std::vector<BitCodeAbbrev*> Abbrevs;
};
std::vector<BlockInfo> BlockInfoRecords;
public:
BitstreamWriter(std::vector<unsigned char> &O)
: Out(O), CurBit(0), CurValue(0), CurCodeSize(2) {}
@ -53,6 +65,15 @@ public:
~BitstreamWriter() {
assert(CurBit == 0 && "Unflused data remaining");
assert(BlockScope.empty() && CurAbbrevs.empty() && "Block imbalance");
// Free the BlockInfoRecords.
while (!BlockInfoRecords.empty()) {
BlockInfo &Info = BlockInfoRecords.back();
// Free blockinfo abbrev info.
for (unsigned i = 0, e = Info.Abbrevs.size(); i != e; ++i)
Info.Abbrevs[i]->dropRef();
BlockInfoRecords.pop_back();
}
}
//===--------------------------------------------------------------------===//
// Basic Primitives for emitting bits to the stream.
@ -139,6 +160,19 @@ public:
// Block Manipulation
//===--------------------------------------------------------------------===//
/// getBlockInfo - If there is block info for the specified ID, return it,
/// otherwise return null.
BlockInfo *getBlockInfo(unsigned BlockID) {
// Common case, the most recent entry matches BlockID.
if (!BlockInfoRecords.empty() && BlockInfoRecords.back().BlockID == BlockID)
return &BlockInfoRecords.back();
for (unsigned i = 0, e = BlockInfoRecords.size(); i != e; ++i)
if (BlockInfoRecords[i].BlockID == BlockID)
return &BlockInfoRecords[i];
return 0;
}
void EnterSubblock(unsigned BlockID, unsigned CodeLen) {
// Block header:
// [ENTER_SUBBLOCK, blockid, newcodelen, <align4bytes>, blocklen]
@ -146,13 +180,28 @@ public:
EmitVBR(BlockID, bitc::BlockIDWidth);
EmitVBR(CodeLen, bitc::CodeLenWidth);
FlushToWord();
BlockScope.push_back(Block(CurCodeSize, Out.size()/4));
BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
unsigned BlockSizeWordLoc = Out.size();
unsigned OldCodeSize = CurCodeSize;
// Emit a placeholder, which will be replaced when the block is popped.
Emit(0, bitc::BlockSizeWidth);
CurCodeSize = CodeLen;
// Push the outer block's abbrev set onto the stack, start out with an
// empty abbrev set.
BlockScope.push_back(Block(OldCodeSize, BlockSizeWordLoc/4));
BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
// If there is a blockinfo for this BlockID, add all the predefined abbrevs
// to the abbrev list.
if (BlockInfo *Info = getBlockInfo(BlockID)) {
for (unsigned i = 0, e = Info->Abbrevs.size(); i != e; ++i) {
CurAbbrevs.push_back(Info->Abbrevs[i]);
Info->Abbrevs[i]->addRef();
}
}
}
void ExitBlock() {
@ -261,15 +310,14 @@ public:
EmitVBR64(Vals[i], 6);
}
}
//===--------------------------------------------------------------------===//
// Abbrev Emission
//===--------------------------------------------------------------------===//
/// EmitAbbrev - This emits an abbreviation to the stream. Note that this
/// method takes ownership of the specified abbrev.
unsigned EmitAbbrev(BitCodeAbbrev *Abbv) {
// Emit the abbreviation as a record.
private:
// Emit the abbreviation as a DEFINE_ABBREV record.
void EncodeAbbrev(BitCodeAbbrev *Abbv) {
EmitCode(bitc::DEFINE_ABBREV);
EmitVBR(Abbv->getNumOperandInfos(), 5);
for (unsigned i = 0, e = Abbv->getNumOperandInfos(); i != e; ++i) {
@ -283,10 +331,62 @@ public:
EmitVBR64(Op.getEncodingData(), 5);
}
}
}
public:
/// EmitAbbrev - This emits an abbreviation to the stream. Note that this
/// method takes ownership of the specified abbrev.
unsigned EmitAbbrev(BitCodeAbbrev *Abbv) {
// Emit the abbreviation as a record.
EncodeAbbrev(Abbv);
CurAbbrevs.push_back(Abbv);
return CurAbbrevs.size()-1+bitc::FIRST_APPLICATION_ABBREV;
}
//===--------------------------------------------------------------------===//
// BlockInfo Block Emission
//===--------------------------------------------------------------------===//
/// EnterBlockInfoBlock - Start emitting the BLOCKINFO_BLOCK.
void EnterBlockInfoBlock(unsigned CodeWidth) {
EnterSubblock(bitc::BLOCKINFO_BLOCK_ID, CodeWidth);
BlockInfoCurBID = -1U;
}
private:
/// SwitchToBlockID - If we aren't already talking about the specified block
/// ID, emit a BLOCKINFO_CODE_SETBID record.
void SwitchToBlockID(unsigned BlockID) {
if (BlockInfoCurBID == BlockID) return;
SmallVector<unsigned, 2> V;
V.push_back(BlockID);
EmitRecord(bitc::BLOCKINFO_CODE_SETBID, V);
BlockInfoCurBID = BlockID;
}
BlockInfo &getOrCreateBlockInfo(unsigned BlockID) {
if (BlockInfo *BI = getBlockInfo(BlockID))
return *BI;
// Otherwise, add a new record.
BlockInfoRecords.push_back(BlockInfo());
BlockInfoRecords.back().BlockID = BlockID;
return BlockInfoRecords.back();
}
public:
/// EmitBlockInfoAbbrev - Emit a DEFINE_ABBREV record for the specified
/// BlockID.
unsigned EmitBlockInfoAbbrev(unsigned BlockID, BitCodeAbbrev *Abbv) {
SwitchToBlockID(BlockID);
EncodeAbbrev(Abbv);
// Add the abbrev to the specified block record.
BlockInfo &Info = getOrCreateBlockInfo(BlockID);
Info.Abbrevs.push_back(Abbv);
return Info.Abbrevs.size()-1+bitc::FIRST_APPLICATION_ABBREV;
}
};