//===-- Writer.cpp - Library for writing LLVM bytecode files --------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This library implements the functionality defined in llvm/Bytecode/Writer.h
//
// Note that this file uses an unusual technique of outputting all the bytecode
// to a deque of unsigned char, then copies the deque to an ostream. The
// reason for this is that we must do "seeking" in the stream to do back-
// patching, and some very important ostreams that we want to support (like
// pipes) do not support seeking. :( :( :(
//
// The choice of the deque data structure is influenced by the extremely fast
// "append" speed, plus the free "seek"/replace in the middle of the stream. I
// didn't use a vector because the stream could end up very large and copying
// the whole thing to reallocate would be kinda silly.
//
//===----------------------------------------------------------------------===//
#include "WriterInternals.h"
#include "llvm/Bytecode/WriteBytecodePass.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/SymbolTable.h"
#include "Support/STLExtras.h"
#include "Support/Statistic.h"
#include "Support/Debug.h"
#include <cstring>
#include <algorithm>
using namespace llvm;
static RegisterPass<WriteBytecodePass> X("emitbytecode", "Bytecode Writer");
static Statistic<>
BytesWritten("bytecodewriter", "Number of bytecode bytes written");
static Statistic<>
ConstantTotalBytes("bytecodewriter", "Bytes of constants total");
static Statistic<>
FunctionConstantTotalBytes("bytecodewriter", "Bytes of function constants total");
static Statistic<>
ConstantPlaneHeaderBytes("bytecodewriter", "Constant plane header bytes");
static Statistic<>
InstructionBytes("bytecodewriter", "Bytes of bytes of instructions");
static Statistic<>
SymTabBytes("bytecodewriter", "Bytes of symbol table");
static Statistic<>
ModuleInfoBytes("bytecodewriter", "Bytes of module info");
BytecodeWriter::BytecodeWriter(std::deque<unsigned char> &o, const Module *M)
: Out(o), Table(M, true) {
// Emit the signature...
static const unsigned char *Sig = (const unsigned char*)"llvm";
output_data(Sig, Sig+4, Out);
// Emit the top level CLASS block.
BytecodeBlock ModuleBlock(BytecodeFormat::Module, Out);
bool isBigEndian = M->getEndianness() == Module::BigEndian;
bool hasLongPointers = M->getPointerSize() == Module::Pointer64;
bool hasNoEndianness = M->getEndianness() == Module::AnyEndianness;
bool hasNoPointerSize = M->getPointerSize() == Module::AnyPointerSize;
// Output the version identifier... we are currently on bytecode version #1,
// which corresponds to LLVM v1.2.
unsigned Version = (1 << 4) | isBigEndian | (hasLongPointers << 1) |
(hasNoEndianness << 2) | (hasNoPointerSize << 3);
output_vbr(Version, Out);
align32(Out);
{
BytecodeBlock CPool(BytecodeFormat::GlobalTypePlane, Out);
// Write the type plane for types first because earlier planes (e.g. for a
// primitive type like float) may have constants constructed using types
// coming later (e.g., via getelementptr from a pointer type). The type
// plane is needed before types can be fwd or bkwd referenced.
const std::vector<const Value*> &Plane = Table.getPlane(Type::TypeTyID);
assert(!Plane.empty() && "No types at all?");
unsigned ValNo = Type::FirstDerivedTyID; // Start at the derived types...
outputConstantsInPlane(Plane, ValNo); // Write out the types
}
DEBUG(for (unsigned i = 0; i != Type::TypeTyID; ++i)
if (Table.getPlane(i).size())
std::cerr << " ModuleLevel["
<< *Type::getPrimitiveType((Type::PrimitiveID)i)
<< "] = " << Table.getPlane(i).size() << "\n");
// The ModuleInfoBlock follows directly after the type information
outputModuleInfoBlock(M);
// Output module level constants, used for global variable initializers
outputConstants(false);
// Do the whole module now! Process each function at a time...
for (Module::const_iterator I = M->begin(), E = M->end(); I != E; ++I)
outputFunction(I);
// If needed, output the symbol table for the module...
outputSymbolTable(M->getSymbolTable());
}
// Helper function for outputConstants().
// Writes out all the constants in the plane Plane starting at entry StartNo.
//
void BytecodeWriter::outputConstantsInPlane(const std::vector<const Value*>
&Plane, unsigned StartNo) {
unsigned ValNo = StartNo;
// Scan through and ignore function arguments, global values, and constant
// strings.
for (; ValNo < Plane.size() &&
(isa<Argument>(Plane[ValNo]) || isa<GlobalValue>(Plane[ValNo]) ||
(isa<ConstantArray>(Plane[ValNo]) &&
cast<ConstantArray>(Plane[ValNo])->isString())); ValNo++)
/*empty*/;
unsigned NC = ValNo; // Number of constants
for (; NC < Plane.size() &&
(isa<Constant>(Plane[NC]) || isa<Type>(Plane[NC])); NC++)
/*empty*/;
NC -= ValNo; // Convert from index into count
if (NC == 0) return; // Skip empty type planes...
// FIXME: Most slabs only have 1 or 2 entries! We should encode this much
// more compactly.
ConstantPlaneHeaderBytes -= Out.size();
// Output type header: [num entries][type id number]
//
output_vbr(NC, Out);
// Output the Type ID Number...
int Slot = Table.getSlot(Plane.front()->getType());
assert (Slot != -1 && "Type in constant pool but not in function!!");
output_vbr((unsigned)Slot, Out);
ConstantPlaneHeaderBytes += Out.size();
//cerr << "Emitting " << NC << " constants of type '"
// << Plane.front()->getType()->getName() << "' = Slot #" << Slot << "\n";
for (unsigned i = ValNo; i < ValNo+NC; ++i) {
const Value *V = Plane[i];
if (const Constant *CPV = dyn_cast<Constant>(V)) {
//cerr << "Serializing value: <" << V->getType() << ">: " << V << ":"
// << Out.size() << "\n";
outputConstant(CPV);
} else {
outputType(cast<Type>(V));
}
}
}
void BytecodeWriter::outputConstants(bool isFunction) {
ConstantTotalBytes -= Out.size();
if (isFunction) FunctionConstantTotalBytes -= Out.size();
BytecodeBlock CPool(BytecodeFormat::ConstantPool, Out);
unsigned NumPlanes = Table.getNumPlanes();
// Output the type plane before any constants!
if (isFunction && NumPlanes > Type::TypeTyID) {
const std::vector<const Value*> &Plane = Table.getPlane(Type::TypeTyID);
if (!Plane.empty()) { // Skip empty type planes...
unsigned ValNo = Table.getModuleLevel(Type::TypeTyID);
outputConstantsInPlane(Plane, ValNo);
}
}
// Output module-level string constants before any other constants.x
if (!isFunction)
outputConstantStrings();
for (unsigned pno = 0; pno != NumPlanes; pno++)
if (pno != Type::TypeTyID) { // Type plane handled above.
const std::vector<const Value*> &Plane = Table.getPlane(pno);
if (!Plane.empty()) { // Skip empty type planes...
unsigned ValNo = 0;
if (isFunction) // Don't re-emit module constants
ValNo += Table.getModuleLevel(pno);
if (pno >= Type::FirstDerivedTyID) {
// Skip zero initializer
if (ValNo == 0)
ValNo = 1;
}
// Write out constants in the plane
outputConstantsInPlane(Plane, ValNo);
}
}
ConstantTotalBytes += Out.size();
if (isFunction) FunctionConstantTotalBytes += Out.size();
}
static unsigned getEncodedLinkage(const GlobalValue *GV) {
switch (GV->getLinkage()) {
default: assert(0 && "Invalid linkage!");
case GlobalValue::ExternalLinkage: return 0;
case GlobalValue::WeakLinkage: return 1;
case GlobalValue::AppendingLinkage: return 2;
case GlobalValue::InternalLinkage: return 3;
case GlobalValue::LinkOnceLinkage: return 4;
}
}
void BytecodeWriter::outputModuleInfoBlock(const Module *M) {
ModuleInfoBytes -= Out.size();
BytecodeBlock ModuleInfoBlock(BytecodeFormat::ModuleGlobalInfo, Out);
// Output the types for the global variables in the module...
for (Module::const_giterator I = M->gbegin(), End = M->gend(); I != End;++I) {
int Slot = Table.getSlot(I->getType());
assert(Slot != -1 && "Module global vars is broken!");
// Fields: bit0 = isConstant, bit1 = hasInitializer, bit2-4=Linkage,
// bit5+ = Slot # for type
unsigned oSlot = ((unsigned)Slot << 5) | (getEncodedLinkage(I) << 2) |
(I->hasInitializer() << 1) | I->isConstant();
output_vbr(oSlot, Out);
// If we have an initializer, output it now.
if (I->hasInitializer()) {
Slot = Table.getSlot((Value*)I->getInitializer());
assert(Slot != -1 && "No slot for global var initializer!");
output_vbr((unsigned)Slot, Out);
}
}
output_vbr((unsigned)Table.getSlot(Type::VoidTy), Out);
// Output the types of the functions in this module...
for (Module::const_iterator I = M->begin(), End = M->end(); I != End; ++I) {
int Slot = Table.getSlot(I->getType());
assert(Slot != -1 && "Module const pool is broken!");
assert(Slot >= Type::FirstDerivedTyID && "Derived type not in range!");
output_vbr((unsigned)Slot, Out);
}
output_vbr((unsigned)Table.getSlot(Type::VoidTy), Out);
ModuleInfoBytes += Out.size();
}
void BytecodeWriter::outputFunction(const Function *F) {
BytecodeBlock FunctionBlock(BytecodeFormat::Function, Out);
output_vbr(getEncodedLinkage(F), Out);
// Only output the constant pool and other goodies if needed...
if (!F->isExternal()) {
// Get slot information about the function...
Table.incorporateFunction(F);
// Output information about the constants in the function...
outputConstants(true);
{ // Output all of the instructions in the body of the function
BytecodeBlock ILBlock(BytecodeFormat::InstructionList, Out);
InstructionBytes -= Out.size();
for (Function::const_iterator BB = F->begin(), E = F->end(); BB != E;++BB)
for(BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I!=E;++I)
processInstruction(*I);
InstructionBytes += Out.size();
}
// If needed, output the symbol table for the function...
outputSymbolTable(F->getSymbolTable());
Table.purgeFunction();
}
}
void BytecodeWriter::outputSymbolTable(const SymbolTable &MST) {
// Do not output the Bytecode block for an empty symbol table, it just wastes
// space!
if (MST.begin() == MST.end()) return;
SymTabBytes -= Out.size();
BytecodeBlock SymTabBlock(BytecodeFormat::SymbolTable, Out);
for (SymbolTable::const_iterator TI = MST.begin(); TI != MST.end(); ++TI) {
SymbolTable::type_const_iterator I = MST.type_begin(TI->first);
SymbolTable::type_const_iterator End = MST.type_end(TI->first);
int Slot;
if (I == End) continue; // Don't mess with an absent type...
// Symtab block header: [num entries][type id number]
output_vbr(MST.type_size(TI->first), Out);
Slot = Table.getSlot(TI->first);
assert(Slot != -1 && "Type in symtab, but not in table!");
output_vbr((unsigned)Slot, Out);
for (; I != End; ++I) {
// Symtab entry: [def slot #][name]
Slot = Table.getSlot(I->second);
assert(Slot != -1 && "Value in symtab but has no slot number!!");
output_vbr((unsigned)Slot, Out);
output(I->first, Out, false); // Don't force alignment...
}
}
SymTabBytes += Out.size();
}
void llvm::WriteBytecodeToFile(const Module *C, std::ostream &Out) {
assert(C && "You can't write a null module!!");
std::deque<unsigned char> Buffer;
// This object populates buffer for us...
BytecodeWriter BCW(Buffer, C);
// Keep track of how much we've written...
BytesWritten += Buffer.size();
// Okay, write the deque out to the ostream now... the deque is not
// sequential in memory, however, so write out as much as possible in big
// chunks, until we're done.
//
std::deque<unsigned char>::const_iterator I = Buffer.begin(),E = Buffer.end();
while (I != E) { // Loop until it's all written
// Scan to see how big this chunk is...
const unsigned char *ChunkPtr = &*I;
const unsigned char *LastPtr = ChunkPtr;
while (I != E) {
const unsigned char *ThisPtr = &*++I;
if (LastPtr+1 != ThisPtr) { // Advanced by more than a byte of memory?
++LastPtr;
break;
}
LastPtr = ThisPtr;
}
// Write out the chunk...
Out.write((char*)ChunkPtr, LastPtr-ChunkPtr);
}
Out.flush();
}