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llvm-mirror/lib/Bytecode/Writer/Writer.cpp
Chris Lattner ec1a192b16 *** empty log message ***
llvm-svn: 3105
2002-07-26 18:40:14 +00:00

267 lines
9.5 KiB
C++

//===-- Writer.cpp - Library for writing VM bytecode files -------*- C++ -*--=//
//
// 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'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/Bytecode/WriteBytecodePass.h"
#include "llvm/Module.h"
#include "llvm/SymbolTable.h"
#include "llvm/DerivedTypes.h"
#include "Support/STLExtras.h"
#include "Support/StatisticReporter.h"
#include <string.h>
#include <algorithm>
static RegisterPass<WriteBytecodePass> X("emitbytecode", "Bytecode Writer");
static Statistic<>
BytesWritten("bytecodewriter\t- Number of bytecode bytes written");
BytecodeWriter::BytecodeWriter(std::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 function protos
outputConstants(false);
// The ModuleInfoBlock follows directly after the Module constant pool
outputModuleInfoBlock(M);
// Do the whole module now! Process each function at a time...
for (Module::const_iterator I = M->begin(), E = M->end(); I != E; ++I)
processMethod(I);
// If needed, output the symbol table for the module...
if (M->hasSymbolTable())
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...
for (; ValNo < Plane.size() && isa<Argument>(Plane[ValNo]); 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...
// 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 function!!");
output_vbr((unsigned)Slot, Out);
//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<const Type>(V));
}
}
}
void BytecodeWriter::outputConstants(bool isFunction) {
BytecodeBlock CPool(BytecodeFormat::ConstantPool, Out);
unsigned NumPlanes = Table.getNumPlanes();
// 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.
if (!isFunction) {
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
}
for (unsigned pno = 0; pno < NumPlanes; pno++) {
const std::vector<const Value*> &Plane = Table.getPlane(pno);
if (Plane.empty()) continue; // Skip empty type planes...
unsigned ValNo = 0;
if (isFunction) // Don't reemit module constants
ValNo = Table.getModuleLevel(pno);
else if (pno == Type::TypeTyID)
continue; // Type plane was written out above
outputConstantsInPlane(Plane, ValNo); // Write out constants in the plane
}
}
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) {
int Slot = Table.getValSlot(I->getType());
assert(Slot != -1 && "Module global vars is broken!");
// Fields: bit0 = isConstant, bit1 = hasInitializer, bit2=InternalLinkage,
// bit3+ = slot#
unsigned oSlot = ((unsigned)Slot << 3) | (I->hasInternalLinkage() << 2) |
(I->hasInitializer() << 1) | I->isConstant();
output_vbr(oSlot, Out);
// If we have an initializer, output it now.
if (I->hasInitializer()) {
Slot = Table.getValSlot((Value*)I->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 functions 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 Function *F) {
BytecodeBlock FunctionBlock(BytecodeFormat::Function, Out);
output_vbr((unsigned)F->hasInternalLinkage(), 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 basic block nodes...
for (Function::const_iterator I = F->begin(), E = F->end(); I != E; ++I)
processBasicBlock(*I);
// If needed, output the symbol table for the function...
if (F->hasSymbolTable())
outputSymbolTable(*F->getSymbolTable());
Table.purgeFunction();
}
}
void BytecodeWriter::processBasicBlock(const BasicBlock &BB) {
BytecodeBlock FunctionBlock(BytecodeFormat::BasicBlock, Out);
// Process all the instructions in the bb...
for(BasicBlock::const_iterator I = BB.begin(), E = BB.end(); I != E; ++I)
processInstruction(*I);
}
void BytecodeWriter::outputSymbolTable(const SymbolTable &MST) {
BytecodeBlock FunctionBlock(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, 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();
}