//===-- Writer.cpp - Library for writing VM bytecode files -------*- C++ -*--=//
//
// This library implements the functionality defined in llvm/Bytecode/Writer.h
//
// This library uses the Analysis library to figure out offsets for
// variables in the method tables...
//
// Note that this file uses an unusual technique of outputting all the bytecode
// to a deque of unsigned char's, 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.
//
// Note that the performance of this library is not terribly important, because
// it shouldn't be used by JIT type applications... so it is not a huge focus
// at least. :)
//
//===----------------------------------------------------------------------===//
#include "WriterInternals.h"
#include "llvm/Module.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Method.h"
#include "llvm/BasicBlock.h"
#include "llvm/ConstPoolVals.h"
#include "llvm/SymbolTable.h"
#include "llvm/DerivedTypes.h"
#include "Support/STLExtras.h"
#include <string.h>
#include <algorithm>
BytecodeWriter::BytecodeWriter(deque<unsigned char> &o, const Module *M)
: Out(o), Table(M, false) {
outputSignature();
// Emit the top level CLASS block.
BytecodeBlock ModuleBlock(BytecodeFormat::Module, Out);
// Output the ID of first "derived" type:
output_vbr((unsigned)Type::FirstDerivedTyID, Out);
align32(Out);
// Output module level constants, including types used by the method protos
outputConstants(false);
// The ModuleInfoBlock follows directly after the Module constant pool
outputModuleInfoBlock(M);
// Do the whole module now! Process each method at a time...
for_each(M->begin(), M->end(),
bind_obj(this, &BytecodeWriter::processMethod));
// If needed, output the symbol table for the module...
if (M->hasSymbolTable())
outputSymbolTable(*M->getSymbolTable());
}
void BytecodeWriter::outputConstants(bool isMethod) {
BytecodeBlock CPool(BytecodeFormat::ConstantPool, Out);
unsigned NumPlanes = Table.getNumPlanes();
for (unsigned pno = 0; pno < NumPlanes; pno++) {
const vector<const Value*> &Plane = Table.getPlane(pno);
if (Plane.empty()) continue; // Skip empty type planes...
unsigned ValNo = 0;
if (isMethod) // Don't reemit module constants
ValNo = Table.getModuleLevel(pno);
else if (pno == Type::TypeTyID)
ValNo = Type::FirstDerivedTyID; // Start emitting at the derived types...
// Scan through and ignore method arguments...
for (; ValNo < Plane.size() && isa<MethodArgument>(Plane[ValNo]); ValNo++)
/*empty*/;
unsigned NC = ValNo; // Number of constants
for (; NC < Plane.size() &&
(isa<ConstPoolVal>(Plane[NC]) ||
isa<Type>(Plane[NC])); NC++) /*empty*/;
NC -= ValNo; // Convert from index into count
if (NC == 0) continue; // Skip empty type planes...
// Output type header: [num entries][type id number]
//
output_vbr(NC, Out);
// Output the Type ID Number...
int Slot = Table.getValSlot(Plane.front()->getType());
assert (Slot != -1 && "Type in constant pool but not in method!!");
output_vbr((unsigned)Slot, Out);
//cout << "Emitting " << NC << " constants of type '"
// << Plane.front()->getType()->getName() << "' = Slot #" << Slot << endl;
for (unsigned i = ValNo; i < ValNo+NC; ++i) {
const Value *V = Plane[i];
if (const ConstPoolVal *CPV = dyn_cast<ConstPoolVal>(V)) {
//cerr << "Serializing value: <" << V->getType() << ">: "
// << ((const ConstPoolVal*)V)->getStrValue() << ":"
// << Out.size() << "\n";
outputConstant(CPV);
} else {
outputType(cast<const Type>(V));
}
}
}
}
void BytecodeWriter::outputModuleInfoBlock(const Module *M) {
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) {
const GlobalVariable *GV = *I;
int Slot = Table.getValSlot(GV->getType());
assert(Slot != -1 && "Module global vars is broken!");
// Fields: bit0 = isConstant, bit1 = hasInitializer, bit2=InternalLinkage,
// bit3+ = slot#
unsigned oSlot = ((unsigned)Slot << 3) | (GV->hasInternalLinkage() << 2) |
(GV->hasInitializer() << 1) | GV->isConstant();
output_vbr(oSlot, Out);
// If we have an initializer, output it now.
if (GV->hasInitializer()) {
Slot = Table.getValSlot(GV->getInitializer());
assert(Slot != -1 && "No slot for global var initializer!");
output_vbr((unsigned)Slot, Out);
}
}
output_vbr((unsigned)Table.getValSlot(Type::VoidTy), Out);
// Output the types of the methods in this module...
for (Module::const_iterator I = M->begin(), End = M->end(); I != End; ++I) {
int Slot = Table.getValSlot((*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.getValSlot(Type::VoidTy), Out);
align32(Out);
}
void BytecodeWriter::processMethod(const Method *M) {
BytecodeBlock MethodBlock(BytecodeFormat::Method, Out);
output_vbr((unsigned)M->hasInternalLinkage(), Out);
// Only output the constant pool and other goodies if needed...
if (!M->isExternal()) {
// Get slot information about the method...
Table.incorporateMethod(M);
// Output information about the constants in the method...
outputConstants(true);
// Output basic block nodes...
for_each(M->begin(), M->end(),
bind_obj(this, &BytecodeWriter::processBasicBlock));
// If needed, output the symbol table for the method...
if (M->hasSymbolTable())
outputSymbolTable(*M->getSymbolTable());
Table.purgeMethod();
}
}
void BytecodeWriter::processBasicBlock(const BasicBlock *BB) {
BytecodeBlock MethodBlock(BytecodeFormat::BasicBlock, Out);
// Process all the instructions in the bb...
for_each(BB->begin(), BB->end(),
bind_obj(this, &BytecodeWriter::processInstruction));
}
void BytecodeWriter::outputSymbolTable(const SymbolTable &MST) {
BytecodeBlock MethodBlock(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.getValSlot(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.getValSlot(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...
}
}
}
void WriteBytecodeToFile(const Module *C, ostream &Out) {
assert(C && "You can't write a null module!!");
deque<unsigned char> Buffer;
// This object populates buffer for us...
BytecodeWriter BCW(Buffer, C);
// 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.
//
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(ChunkPtr, LastPtr-ChunkPtr);
}
Out.flush();
}