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https://github.com/c64scene-ar/llvm-6502.git
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8d42fc3da2
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36757 91177308-0d34-0410-b5e6-96231b3b80d8
296 lines
9.4 KiB
C++
296 lines
9.4 KiB
C++
//===- BitstreamWriter.h - Low-level bitstream writer interface -*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by Chris Lattner and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This header defines the BitstreamWriter class. This class can be used to
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// write an arbitrary bitstream, regardless of its contents.
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//
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//===----------------------------------------------------------------------===//
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#ifndef BITSTREAM_WRITER_H
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#define BITSTREAM_WRITER_H
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#include "llvm/Bitcode/BitCodes.h"
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#include <vector>
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namespace llvm {
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class BitstreamWriter {
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std::vector<unsigned char> &Out;
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/// CurBit - Always between 0 and 31 inclusive, specifies the next bit to use.
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unsigned CurBit;
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/// CurValue - The current value. Only bits < CurBit are valid.
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uint32_t CurValue;
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// CurCodeSize - This is the declared size of code values used for the current
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// block, in bits.
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unsigned CurCodeSize;
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/// CurAbbrevs - Abbrevs installed at in this block.
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std::vector<BitCodeAbbrev*> CurAbbrevs;
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struct Block {
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unsigned PrevCodeSize;
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unsigned StartSizeWord;
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std::vector<BitCodeAbbrev*> PrevAbbrevs;
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Block(unsigned PCS, unsigned SSW) : PrevCodeSize(PCS), StartSizeWord(SSW) {}
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};
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/// BlockScope - This tracks the current blocks that we have entered.
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std::vector<Block> BlockScope;
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public:
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BitstreamWriter(std::vector<unsigned char> &O)
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: Out(O), CurBit(0), CurValue(0), CurCodeSize(2) {}
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~BitstreamWriter() {
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assert(CurBit == 0 && "Unflused data remaining");
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assert(BlockScope.empty() && CurAbbrevs.empty() && "Block imbalance");
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}
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//===--------------------------------------------------------------------===//
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// Basic Primitives for emitting bits to the stream.
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//===--------------------------------------------------------------------===//
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void Emit(uint32_t Val, unsigned NumBits) {
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assert(NumBits <= 32 && "Invalid value size!");
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assert((Val & ~(~0U >> (32-NumBits))) == 0 && "High bits set!");
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CurValue |= Val << CurBit;
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if (CurBit + NumBits < 32) {
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CurBit += NumBits;
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return;
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}
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// Add the current word.
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unsigned V = CurValue;
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Out.push_back((unsigned char)(V >> 0));
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Out.push_back((unsigned char)(V >> 8));
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Out.push_back((unsigned char)(V >> 16));
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Out.push_back((unsigned char)(V >> 24));
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if (CurBit)
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CurValue = Val >> (32-CurBit);
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else
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CurValue = 0;
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CurBit = (CurBit+NumBits) & 31;
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}
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void Emit64(uint64_t Val, unsigned NumBits) {
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if (NumBits <= 32)
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Emit((uint32_t)Val, NumBits);
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else {
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Emit((uint32_t)Val, 32);
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Emit((uint32_t)(Val >> 32), NumBits-32);
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}
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}
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void FlushToWord() {
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if (CurBit) {
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unsigned V = CurValue;
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Out.push_back((unsigned char)(V >> 0));
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Out.push_back((unsigned char)(V >> 8));
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Out.push_back((unsigned char)(V >> 16));
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Out.push_back((unsigned char)(V >> 24));
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CurBit = 0;
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CurValue = 0;
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}
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}
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void EmitVBR(uint32_t Val, unsigned NumBits) {
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uint32_t Threshold = 1U << (NumBits-1);
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// Emit the bits with VBR encoding, NumBits-1 bits at a time.
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while (Val >= Threshold) {
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Emit((Val & ((1 << (NumBits-1))-1)) | (1 << (NumBits-1)), NumBits);
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Val >>= NumBits-1;
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}
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Emit(Val, NumBits);
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}
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void EmitVBR64(uint64_t Val, unsigned NumBits) {
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if ((uint32_t)Val == Val)
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return EmitVBR((uint32_t)Val, NumBits);
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uint64_t Threshold = 1U << (NumBits-1);
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// Emit the bits with VBR encoding, NumBits-1 bits at a time.
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while (Val >= Threshold) {
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Emit(((uint32_t)Val & ((1 << (NumBits-1))-1)) |
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(1 << (NumBits-1)), NumBits);
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Val >>= NumBits-1;
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}
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Emit((uint32_t)Val, NumBits);
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}
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/// EmitCode - Emit the specified code.
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void EmitCode(unsigned Val) {
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Emit(Val, CurCodeSize);
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}
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//===--------------------------------------------------------------------===//
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// Block Manipulation
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//===--------------------------------------------------------------------===//
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void EnterSubblock(unsigned BlockID, unsigned CodeLen) {
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// Block header:
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// [ENTER_SUBBLOCK, blockid, newcodelen, <align4bytes>, blocklen]
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EmitCode(bitc::ENTER_SUBBLOCK);
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EmitVBR(BlockID, bitc::BlockIDWidth);
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EmitVBR(CodeLen, bitc::CodeLenWidth);
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FlushToWord();
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BlockScope.push_back(Block(CurCodeSize, Out.size()/4));
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BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
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// Emit a placeholder, which will be replaced when the block is popped.
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Emit(0, bitc::BlockSizeWidth);
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CurCodeSize = CodeLen;
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}
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void ExitBlock() {
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assert(!BlockScope.empty() && "Block scope imbalance!");
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// Delete all abbrevs.
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for (unsigned i = 0, e = CurAbbrevs.size(); i != e; ++i)
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CurAbbrevs[i]->dropRef();
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const Block &B = BlockScope.back();
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// Block tail:
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// [END_BLOCK, <align4bytes>]
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EmitCode(bitc::END_BLOCK);
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FlushToWord();
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// Compute the size of the block, in words, not counting the size field.
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unsigned SizeInWords = Out.size()/4-B.StartSizeWord - 1;
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unsigned ByteNo = B.StartSizeWord*4;
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// Update the block size field in the header of this sub-block.
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Out[ByteNo++] = (unsigned char)(SizeInWords >> 0);
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Out[ByteNo++] = (unsigned char)(SizeInWords >> 8);
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Out[ByteNo++] = (unsigned char)(SizeInWords >> 16);
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Out[ByteNo++] = (unsigned char)(SizeInWords >> 24);
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// Restore the inner block's code size and abbrev table.
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CurCodeSize = B.PrevCodeSize;
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BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
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BlockScope.pop_back();
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}
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//===--------------------------------------------------------------------===//
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// Record Emission
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//===--------------------------------------------------------------------===//
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private:
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/// EmitAbbreviatedField - Emit a single scalar field value with the specified
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/// encoding.
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template<typename uintty>
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void EmitAbbreviatedField(const BitCodeAbbrevOp &Op, uintty V) {
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if (Op.isLiteral()) {
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// If the abbrev specifies the literal value to use, don't emit
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// anything.
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assert(V == Op.getLiteralValue() &&
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"Invalid abbrev for record!");
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return;
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}
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// Encode the value as we are commanded.
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switch (Op.getEncoding()) {
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default: assert(0 && "Unknown encoding!");
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case BitCodeAbbrevOp::Fixed:
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Emit(V, Op.getEncodingData());
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break;
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case BitCodeAbbrevOp::VBR:
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EmitVBR(V, Op.getEncodingData());
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break;
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}
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}
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public:
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/// EmitRecord - Emit the specified record to the stream, using an abbrev if
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/// we have one to compress the output.
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template<typename uintty>
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void EmitRecord(unsigned Code, SmallVectorImpl<uintty> &Vals,
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unsigned Abbrev = 0) {
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if (Abbrev) {
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unsigned AbbrevNo = Abbrev-bitc::FIRST_APPLICATION_ABBREV;
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assert(AbbrevNo < CurAbbrevs.size() && "Invalid abbrev #!");
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BitCodeAbbrev *Abbv = CurAbbrevs[AbbrevNo];
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EmitCode(Abbrev);
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// Insert the code into Vals to treat it uniformly.
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Vals.insert(Vals.begin(), Code);
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unsigned RecordIdx = 0;
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for (unsigned i = 0, e = Abbv->getNumOperandInfos(); i != e; ++i) {
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assert(RecordIdx < Vals.size() && "Invalid abbrev/record");
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const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
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if (Op.isLiteral() || Op.getEncoding() != BitCodeAbbrevOp::Array) {
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EmitAbbreviatedField(Op, Vals[RecordIdx]);
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++RecordIdx;
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} else {
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// Array case.
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assert(i+2 == e && "array op not second to last?");
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const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i);
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// Emit a vbr6 to indicate the number of elements present.
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EmitVBR(Vals.size()-RecordIdx, 6);
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// Emit each field.
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for (; RecordIdx != Vals.size(); ++RecordIdx)
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EmitAbbreviatedField(EltEnc, Vals[RecordIdx]);
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}
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}
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assert(RecordIdx == Vals.size() && "Not all record operands emitted!");
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} else {
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// If we don't have an abbrev to use, emit this in its fully unabbreviated
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// form.
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EmitCode(bitc::UNABBREV_RECORD);
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EmitVBR(Code, 6);
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EmitVBR(Vals.size(), 6);
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for (unsigned i = 0, e = Vals.size(); i != e; ++i)
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EmitVBR64(Vals[i], 6);
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}
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}
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//===--------------------------------------------------------------------===//
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// Abbrev Emission
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//===--------------------------------------------------------------------===//
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/// EmitAbbrev - This emits an abbreviation to the stream. Note that this
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/// method takes ownership of the specified abbrev.
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unsigned EmitAbbrev(BitCodeAbbrev *Abbv) {
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// Emit the abbreviation as a record.
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EmitCode(bitc::DEFINE_ABBREV);
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EmitVBR(Abbv->getNumOperandInfos(), 5);
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for (unsigned i = 0, e = Abbv->getNumOperandInfos(); i != e; ++i) {
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const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
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Emit(Op.isLiteral(), 1);
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if (Op.isLiteral()) {
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EmitVBR64(Op.getLiteralValue(), 8);
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} else {
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Emit(Op.getEncoding(), 3);
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if (Op.hasEncodingData())
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EmitVBR64(Op.getEncodingData(), 5);
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}
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}
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CurAbbrevs.push_back(Abbv);
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return CurAbbrevs.size()-1+bitc::FIRST_APPLICATION_ABBREV;
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}
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};
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} // End llvm namespace
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#endif
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