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63b6fead6b
Split out SimpleBitstreamCursor from BitstreamCursor, which is a lower-level cursor with no knowledge of bitcode blocks, abbreviations, or records. It just knows how to read bits and navigate the stream. This is mainly organizational, to separate the API for manipulating raw bits from that for bitcode concepts like Record and Block. llvm-svn: 264545
393 lines
13 KiB
C++
393 lines
13 KiB
C++
//===- BitstreamReader.cpp - BitstreamReader implementation ---------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Bitcode/BitstreamReader.h"
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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// BitstreamCursor implementation
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//===----------------------------------------------------------------------===//
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void BitstreamCursor::freeState() {
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// Free all the Abbrevs.
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CurAbbrevs.clear();
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// Free all the Abbrevs in the block scope.
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BlockScope.clear();
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}
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/// EnterSubBlock - Having read the ENTER_SUBBLOCK abbrevid, enter
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/// the block, and return true if the block has an error.
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bool BitstreamCursor::EnterSubBlock(unsigned BlockID, unsigned *NumWordsP) {
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// Save the current block's state on BlockScope.
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BlockScope.push_back(Block(CurCodeSize));
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BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
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// Add the abbrevs specific to this block to the CurAbbrevs list.
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if (const BitstreamReader::BlockInfo *Info =
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getBitStreamReader()->getBlockInfo(BlockID)) {
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CurAbbrevs.insert(CurAbbrevs.end(), Info->Abbrevs.begin(),
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Info->Abbrevs.end());
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}
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// Get the codesize of this block.
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CurCodeSize = ReadVBR(bitc::CodeLenWidth);
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// We can't read more than MaxChunkSize at a time
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if (CurCodeSize > MaxChunkSize)
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return true;
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SkipToFourByteBoundary();
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unsigned NumWords = Read(bitc::BlockSizeWidth);
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if (NumWordsP) *NumWordsP = NumWords;
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// Validate that this block is sane.
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return CurCodeSize == 0 || AtEndOfStream();
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}
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static uint64_t readAbbreviatedField(BitstreamCursor &Cursor,
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const BitCodeAbbrevOp &Op) {
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assert(!Op.isLiteral() && "Not to be used with literals!");
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// Decode the value as we are commanded.
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switch (Op.getEncoding()) {
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case BitCodeAbbrevOp::Array:
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case BitCodeAbbrevOp::Blob:
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llvm_unreachable("Should not reach here");
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case BitCodeAbbrevOp::Fixed:
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assert((unsigned)Op.getEncodingData() <= Cursor.MaxChunkSize);
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return Cursor.Read((unsigned)Op.getEncodingData());
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case BitCodeAbbrevOp::VBR:
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assert((unsigned)Op.getEncodingData() <= Cursor.MaxChunkSize);
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return Cursor.ReadVBR64((unsigned)Op.getEncodingData());
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case BitCodeAbbrevOp::Char6:
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return BitCodeAbbrevOp::DecodeChar6(Cursor.Read(6));
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}
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llvm_unreachable("invalid abbreviation encoding");
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}
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static void skipAbbreviatedField(BitstreamCursor &Cursor,
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const BitCodeAbbrevOp &Op) {
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assert(!Op.isLiteral() && "Not to be used with literals!");
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// Decode the value as we are commanded.
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switch (Op.getEncoding()) {
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case BitCodeAbbrevOp::Array:
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case BitCodeAbbrevOp::Blob:
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llvm_unreachable("Should not reach here");
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case BitCodeAbbrevOp::Fixed:
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assert((unsigned)Op.getEncodingData() <= Cursor.MaxChunkSize);
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Cursor.Read((unsigned)Op.getEncodingData());
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break;
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case BitCodeAbbrevOp::VBR:
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assert((unsigned)Op.getEncodingData() <= Cursor.MaxChunkSize);
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Cursor.ReadVBR64((unsigned)Op.getEncodingData());
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break;
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case BitCodeAbbrevOp::Char6:
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Cursor.Read(6);
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break;
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}
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}
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/// skipRecord - Read the current record and discard it.
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void BitstreamCursor::skipRecord(unsigned AbbrevID) {
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// Skip unabbreviated records by reading past their entries.
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if (AbbrevID == bitc::UNABBREV_RECORD) {
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unsigned Code = ReadVBR(6);
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(void)Code;
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unsigned NumElts = ReadVBR(6);
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for (unsigned i = 0; i != NumElts; ++i)
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(void)ReadVBR64(6);
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return;
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}
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const BitCodeAbbrev *Abbv = getAbbrev(AbbrevID);
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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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if (Op.isLiteral())
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continue;
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if (Op.getEncoding() != BitCodeAbbrevOp::Array &&
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Op.getEncoding() != BitCodeAbbrevOp::Blob) {
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skipAbbreviatedField(*this, Op);
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continue;
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}
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if (Op.getEncoding() == BitCodeAbbrevOp::Array) {
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// Array case. Read the number of elements as a vbr6.
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unsigned NumElts = ReadVBR(6);
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// Get the element encoding.
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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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// Read all the elements.
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// Decode the value as we are commanded.
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switch (EltEnc.getEncoding()) {
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default:
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report_fatal_error("Array element type can't be an Array or a Blob");
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case BitCodeAbbrevOp::Fixed:
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assert((unsigned)Op.getEncodingData() <= MaxChunkSize);
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for (; NumElts; --NumElts)
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Read((unsigned)EltEnc.getEncodingData());
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break;
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case BitCodeAbbrevOp::VBR:
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assert((unsigned)Op.getEncodingData() <= MaxChunkSize);
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for (; NumElts; --NumElts)
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ReadVBR64((unsigned)EltEnc.getEncodingData());
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break;
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case BitCodeAbbrevOp::Char6:
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for (; NumElts; --NumElts)
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Read(6);
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break;
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}
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continue;
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}
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assert(Op.getEncoding() == BitCodeAbbrevOp::Blob);
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// Blob case. Read the number of bytes as a vbr6.
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unsigned NumElts = ReadVBR(6);
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SkipToFourByteBoundary(); // 32-bit alignment
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// Figure out where the end of this blob will be including tail padding.
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size_t NewEnd = GetCurrentBitNo()+((NumElts+3)&~3)*8;
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// If this would read off the end of the bitcode file, just set the
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// record to empty and return.
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if (!canSkipToPos(NewEnd/8)) {
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skipToEnd();
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break;
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}
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// Skip over the blob.
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JumpToBit(NewEnd);
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}
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}
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unsigned BitstreamCursor::readRecord(unsigned AbbrevID,
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SmallVectorImpl<uint64_t> &Vals,
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StringRef *Blob) {
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if (AbbrevID == bitc::UNABBREV_RECORD) {
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unsigned Code = ReadVBR(6);
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unsigned NumElts = ReadVBR(6);
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for (unsigned i = 0; i != NumElts; ++i)
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Vals.push_back(ReadVBR64(6));
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return Code;
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}
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const BitCodeAbbrev *Abbv = getAbbrev(AbbrevID);
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// Read the record code first.
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assert(Abbv->getNumOperandInfos() != 0 && "no record code in abbreviation?");
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const BitCodeAbbrevOp &CodeOp = Abbv->getOperandInfo(0);
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unsigned Code;
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if (CodeOp.isLiteral())
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Code = CodeOp.getLiteralValue();
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else {
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if (CodeOp.getEncoding() == BitCodeAbbrevOp::Array ||
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CodeOp.getEncoding() == BitCodeAbbrevOp::Blob)
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report_fatal_error("Abbreviation starts with an Array or a Blob");
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Code = readAbbreviatedField(*this, CodeOp);
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}
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for (unsigned i = 1, e = Abbv->getNumOperandInfos(); i != e; ++i) {
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const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
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if (Op.isLiteral()) {
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Vals.push_back(Op.getLiteralValue());
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continue;
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}
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if (Op.getEncoding() != BitCodeAbbrevOp::Array &&
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Op.getEncoding() != BitCodeAbbrevOp::Blob) {
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Vals.push_back(readAbbreviatedField(*this, Op));
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continue;
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}
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if (Op.getEncoding() == BitCodeAbbrevOp::Array) {
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// Array case. Read the number of elements as a vbr6.
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unsigned NumElts = ReadVBR(6);
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// Get the element encoding.
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if (i + 2 != e)
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report_fatal_error("Array op not second to last");
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const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i);
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if (!EltEnc.isEncoding())
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report_fatal_error(
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"Array element type has to be an encoding of a type");
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// Read all the elements.
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switch (EltEnc.getEncoding()) {
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default:
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report_fatal_error("Array element type can't be an Array or a Blob");
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case BitCodeAbbrevOp::Fixed:
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for (; NumElts; --NumElts)
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Vals.push_back(Read((unsigned)EltEnc.getEncodingData()));
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break;
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case BitCodeAbbrevOp::VBR:
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for (; NumElts; --NumElts)
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Vals.push_back(ReadVBR64((unsigned)EltEnc.getEncodingData()));
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break;
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case BitCodeAbbrevOp::Char6:
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for (; NumElts; --NumElts)
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Vals.push_back(BitCodeAbbrevOp::DecodeChar6(Read(6)));
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}
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continue;
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}
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assert(Op.getEncoding() == BitCodeAbbrevOp::Blob);
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// Blob case. Read the number of bytes as a vbr6.
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unsigned NumElts = ReadVBR(6);
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SkipToFourByteBoundary(); // 32-bit alignment
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// Figure out where the end of this blob will be including tail padding.
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size_t CurBitPos = GetCurrentBitNo();
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size_t NewEnd = CurBitPos+((NumElts+3)&~3)*8;
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// If this would read off the end of the bitcode file, just set the
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// record to empty and return.
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if (!canSkipToPos(NewEnd/8)) {
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Vals.append(NumElts, 0);
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skipToEnd();
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break;
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}
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// Otherwise, inform the streamer that we need these bytes in memory.
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const char *Ptr =
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(const char *)getBitStreamReader()->getBitcodeBytes().getPointer(
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CurBitPos / 8, NumElts);
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// If we can return a reference to the data, do so to avoid copying it.
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if (Blob) {
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*Blob = StringRef(Ptr, NumElts);
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} else {
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// Otherwise, unpack into Vals with zero extension.
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for (; NumElts; --NumElts)
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Vals.push_back((unsigned char)*Ptr++);
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}
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// Skip over tail padding.
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JumpToBit(NewEnd);
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}
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return Code;
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}
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void BitstreamCursor::ReadAbbrevRecord() {
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BitCodeAbbrev *Abbv = new BitCodeAbbrev();
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unsigned NumOpInfo = ReadVBR(5);
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for (unsigned i = 0; i != NumOpInfo; ++i) {
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bool IsLiteral = Read(1);
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if (IsLiteral) {
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Abbv->Add(BitCodeAbbrevOp(ReadVBR64(8)));
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continue;
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}
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BitCodeAbbrevOp::Encoding E = (BitCodeAbbrevOp::Encoding)Read(3);
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if (BitCodeAbbrevOp::hasEncodingData(E)) {
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uint64_t Data = ReadVBR64(5);
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// As a special case, handle fixed(0) (i.e., a fixed field with zero bits)
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// and vbr(0) as a literal zero. This is decoded the same way, and avoids
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// a slow path in Read() to have to handle reading zero bits.
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if ((E == BitCodeAbbrevOp::Fixed || E == BitCodeAbbrevOp::VBR) &&
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Data == 0) {
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Abbv->Add(BitCodeAbbrevOp(0));
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continue;
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}
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if ((E == BitCodeAbbrevOp::Fixed || E == BitCodeAbbrevOp::VBR) &&
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Data > MaxChunkSize)
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report_fatal_error(
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"Fixed or VBR abbrev record with size > MaxChunkData");
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Abbv->Add(BitCodeAbbrevOp(E, Data));
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} else
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Abbv->Add(BitCodeAbbrevOp(E));
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}
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if (Abbv->getNumOperandInfos() == 0)
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report_fatal_error("Abbrev record with no operands");
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CurAbbrevs.push_back(Abbv);
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}
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bool BitstreamCursor::ReadBlockInfoBlock() {
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// If this is the second stream to get to the block info block, skip it.
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if (getBitStreamReader()->hasBlockInfoRecords())
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return SkipBlock();
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if (EnterSubBlock(bitc::BLOCKINFO_BLOCK_ID)) return true;
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SmallVector<uint64_t, 64> Record;
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BitstreamReader::BlockInfo *CurBlockInfo = nullptr;
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// Read all the records for this module.
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while (1) {
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BitstreamEntry Entry = advanceSkippingSubblocks(AF_DontAutoprocessAbbrevs);
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switch (Entry.Kind) {
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case llvm::BitstreamEntry::SubBlock: // Handled for us already.
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case llvm::BitstreamEntry::Error:
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return true;
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case llvm::BitstreamEntry::EndBlock:
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return false;
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case llvm::BitstreamEntry::Record:
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// The interesting case.
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break;
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}
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// Read abbrev records, associate them with CurBID.
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if (Entry.ID == bitc::DEFINE_ABBREV) {
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if (!CurBlockInfo) return true;
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ReadAbbrevRecord();
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// ReadAbbrevRecord installs the abbrev in CurAbbrevs. Move it to the
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// appropriate BlockInfo.
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CurBlockInfo->Abbrevs.push_back(std::move(CurAbbrevs.back()));
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CurAbbrevs.pop_back();
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continue;
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}
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// Read a record.
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Record.clear();
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switch (readRecord(Entry.ID, Record)) {
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default: break; // Default behavior, ignore unknown content.
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case bitc::BLOCKINFO_CODE_SETBID:
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if (Record.size() < 1) return true;
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CurBlockInfo =
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&getBitStreamReader()->getOrCreateBlockInfo((unsigned)Record[0]);
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break;
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case bitc::BLOCKINFO_CODE_BLOCKNAME: {
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if (!CurBlockInfo) return true;
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if (getBitStreamReader()->isIgnoringBlockInfoNames())
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break; // Ignore name.
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std::string Name;
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for (unsigned i = 0, e = Record.size(); i != e; ++i)
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Name += (char)Record[i];
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CurBlockInfo->Name = Name;
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break;
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}
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case bitc::BLOCKINFO_CODE_SETRECORDNAME: {
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if (!CurBlockInfo) return true;
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if (getBitStreamReader()->isIgnoringBlockInfoNames())
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break; // Ignore name.
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std::string Name;
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for (unsigned i = 1, e = Record.size(); i != e; ++i)
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Name += (char)Record[i];
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CurBlockInfo->RecordNames.push_back(std::make_pair((unsigned)Record[0],
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Name));
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break;
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}
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}
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}
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}
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