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286 lines
10 KiB
C++
286 lines
10 KiB
C++
//===-- Writer.cpp - Library for writing VM bytecode files -------*- C++ -*--=//
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//
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// This library implements the functionality defined in llvm/Bytecode/Writer.h
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//
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// Note that this file uses an unusual technique of outputting all the bytecode
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// to a deque of unsigned char's, then copies the deque to an ostream. The
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// reason for this is that we must do "seeking" in the stream to do back-
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// patching, and some very important ostreams that we want to support (like
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// pipes) do not support seeking. :( :( :(
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//
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// The choice of the deque data structure is influenced by the extremely fast
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// "append" speed, plus the free "seek"/replace in the middle of the stream. I
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// didn't use a vector because the stream could end up very large and copying
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// the whole thing to reallocate would be kinda silly.
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//
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// Note that the performance of this library is not terribly important, because
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// it shouldn't be used by JIT type applications... so it is not a huge focus
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// at least. :)
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//
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//===----------------------------------------------------------------------===//
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#include "WriterInternals.h"
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#include "llvm/Bytecode/WriteBytecodePass.h"
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#include "llvm/Module.h"
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#include "llvm/SymbolTable.h"
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#include "llvm/DerivedTypes.h"
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#include "Support/STLExtras.h"
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#include "Support/Statistic.h"
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#include "Config/string.h"
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#include <algorithm>
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static RegisterPass<WriteBytecodePass> X("emitbytecode", "Bytecode Writer");
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static Statistic<>
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BytesWritten("bytecodewriter", "Number of bytecode bytes written");
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BytecodeWriter::BytecodeWriter(std::deque<unsigned char> &o, const Module *M)
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: Out(o), Table(M, false) {
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outputSignature();
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// Emit the top level CLASS block.
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BytecodeBlock ModuleBlock(BytecodeFormat::Module, Out);
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bool isBigEndian = M->isBigEndian();
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bool hasLongPointers = M->has64BitPointers();
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// Output the version identifier... we are currently on bytecode version #2
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unsigned Version = (2 << 4) | isBigEndian | (hasLongPointers << 1);
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output_vbr(Version, Out);
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align32(Out);
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{
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BytecodeBlock CPool(BytecodeFormat::GlobalTypePlane, Out);
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// Write the type plane for types first because earlier planes (e.g. for a
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// primitive type like float) may have constants constructed using types
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// coming later (e.g., via getelementptr from a pointer type). The type
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// plane is needed before types can be fwd or bkwd referenced.
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const std::vector<const Value*> &Plane = Table.getPlane(Type::TypeTyID);
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assert(!Plane.empty() && "No types at all?");
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unsigned ValNo = Type::FirstDerivedTyID; // Start at the derived types...
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outputConstantsInPlane(Plane, ValNo); // Write out the types
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}
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// The ModuleInfoBlock follows directly after the type information
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outputModuleInfoBlock(M);
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// Output module level constants, used for global variable initializers
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outputConstants(false);
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// Do the whole module now! Process each function at a time...
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for (Module::const_iterator I = M->begin(), E = M->end(); I != E; ++I)
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outputFunction(I);
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// If needed, output the symbol table for the module...
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outputSymbolTable(M->getSymbolTable());
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}
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// Helper function for outputConstants().
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// Writes out all the constants in the plane Plane starting at entry StartNo.
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//
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void BytecodeWriter::outputConstantsInPlane(const std::vector<const Value*>
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&Plane, unsigned StartNo) {
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unsigned ValNo = StartNo;
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// Scan through and ignore function arguments/global values...
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for (; ValNo < Plane.size() && (isa<Argument>(Plane[ValNo]) ||
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isa<GlobalValue>(Plane[ValNo])); ValNo++)
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/*empty*/;
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unsigned NC = ValNo; // Number of constants
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for (; NC < Plane.size() &&
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(isa<Constant>(Plane[NC]) || isa<Type>(Plane[NC])); NC++)
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/*empty*/;
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NC -= ValNo; // Convert from index into count
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if (NC == 0) return; // Skip empty type planes...
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// Output type header: [num entries][type id number]
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//
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output_vbr(NC, Out);
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// Output the Type ID Number...
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int Slot = Table.getValSlot(Plane.front()->getType());
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assert (Slot != -1 && "Type in constant pool but not in function!!");
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output_vbr((unsigned)Slot, Out);
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//cerr << "Emitting " << NC << " constants of type '"
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// << Plane.front()->getType()->getName() << "' = Slot #" << Slot << "\n";
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for (unsigned i = ValNo; i < ValNo+NC; ++i) {
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const Value *V = Plane[i];
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if (const Constant *CPV = dyn_cast<Constant>(V)) {
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//cerr << "Serializing value: <" << V->getType() << ">: " << V << ":"
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// << Out.size() << "\n";
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outputConstant(CPV);
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} else {
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outputType(cast<Type>(V));
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}
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}
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}
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void BytecodeWriter::outputConstants(bool isFunction) {
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BytecodeBlock CPool(BytecodeFormat::ConstantPool, Out);
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unsigned NumPlanes = Table.getNumPlanes();
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// Output the type plane before any constants!
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if (isFunction && NumPlanes > Type::TypeTyID) {
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const std::vector<const Value*> &Plane = Table.getPlane(Type::TypeTyID);
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if (!Plane.empty()) { // Skip empty type planes...
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unsigned ValNo = Table.getModuleLevel(Type::TypeTyID);
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outputConstantsInPlane(Plane, ValNo);
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}
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}
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for (unsigned pno = 0; pno != NumPlanes; pno++)
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if (pno != Type::TypeTyID) { // Type plane handled above.
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const std::vector<const Value*> &Plane = Table.getPlane(pno);
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if (!Plane.empty()) { // Skip empty type planes...
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unsigned ValNo = 0;
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if (isFunction) // Don't reemit module constants
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ValNo += Table.getModuleLevel(pno);
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if (pno >= Type::FirstDerivedTyID) {
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// Skip zero initializer
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if (ValNo == 0)
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ValNo = 1;
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}
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// Write out constants in the plane
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outputConstantsInPlane(Plane, ValNo);
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}
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}
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}
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void BytecodeWriter::outputModuleInfoBlock(const Module *M) {
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BytecodeBlock ModuleInfoBlock(BytecodeFormat::ModuleGlobalInfo, Out);
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// Output the types for the global variables in the module...
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for (Module::const_giterator I = M->gbegin(), End = M->gend(); I != End;++I) {
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int Slot = Table.getValSlot(I->getType());
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assert(Slot != -1 && "Module global vars is broken!");
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// Fields: bit0 = isConstant, bit1 = hasInitializer, bit2,3=Linkage,
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// bit4+ = Slot # for type
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unsigned oSlot = ((unsigned)Slot << 4) | ((unsigned)I->getLinkage() << 2) |
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(I->hasInitializer() << 1) | I->isConstant();
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output_vbr(oSlot, Out);
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// If we have an initializer, output it now.
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if (I->hasInitializer()) {
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Slot = Table.getValSlot((Value*)I->getInitializer());
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assert(Slot != -1 && "No slot for global var initializer!");
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output_vbr((unsigned)Slot, Out);
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}
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}
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output_vbr((unsigned)Table.getValSlot(Type::VoidTy), Out);
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// Output the types of the functions in this module...
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for (Module::const_iterator I = M->begin(), End = M->end(); I != End; ++I) {
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int Slot = Table.getValSlot(I->getType());
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assert(Slot != -1 && "Module const pool is broken!");
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assert(Slot >= Type::FirstDerivedTyID && "Derived type not in range!");
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output_vbr((unsigned)Slot, Out);
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}
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output_vbr((unsigned)Table.getValSlot(Type::VoidTy), Out);
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align32(Out);
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}
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void BytecodeWriter::outputFunction(const Function *F) {
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BytecodeBlock FunctionBlock(BytecodeFormat::Function, Out);
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output_vbr((unsigned)F->getLinkage(), Out);
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// Only output the constant pool and other goodies if needed...
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if (!F->isExternal()) {
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// Get slot information about the function...
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Table.incorporateFunction(F);
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// Output information about the constants in the function...
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outputConstants(true);
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// Output basic block nodes...
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for (Function::const_iterator I = F->begin(), E = F->end(); I != E; ++I)
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processBasicBlock(*I);
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// If needed, output the symbol table for the function...
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outputSymbolTable(F->getSymbolTable());
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Table.purgeFunction();
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}
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}
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void BytecodeWriter::processBasicBlock(const BasicBlock &BB) {
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BytecodeBlock FunctionBlock(BytecodeFormat::BasicBlock, Out);
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// Process all the instructions in the bb...
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for(BasicBlock::const_iterator I = BB.begin(), E = BB.end(); I != E; ++I)
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processInstruction(*I);
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}
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void BytecodeWriter::outputSymbolTable(const SymbolTable &MST) {
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BytecodeBlock FunctionBlock(BytecodeFormat::SymbolTable, Out);
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for (SymbolTable::const_iterator TI = MST.begin(); TI != MST.end(); ++TI) {
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SymbolTable::type_const_iterator I = MST.type_begin(TI->first);
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SymbolTable::type_const_iterator End = MST.type_end(TI->first);
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int Slot;
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if (I == End) continue; // Don't mess with an absent type...
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// Symtab block header: [num entries][type id number]
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output_vbr(MST.type_size(TI->first), Out);
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Slot = Table.getValSlot(TI->first);
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assert(Slot != -1 && "Type in symtab, but not in table!");
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output_vbr((unsigned)Slot, Out);
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for (; I != End; ++I) {
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// Symtab entry: [def slot #][name]
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Slot = Table.getValSlot(I->second);
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assert(Slot != -1 && "Value in symtab but has no slot number!!");
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output_vbr((unsigned)Slot, Out);
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output(I->first, Out, false); // Don't force alignment...
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}
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}
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}
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void WriteBytecodeToFile(const Module *C, std::ostream &Out) {
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assert(C && "You can't write a null module!!");
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std::deque<unsigned char> Buffer;
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// This object populates buffer for us...
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BytecodeWriter BCW(Buffer, C);
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// Keep track of how much we've written...
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BytesWritten += Buffer.size();
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// Okay, write the deque out to the ostream now... the deque is not
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// sequential in memory, however, so write out as much as possible in big
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// chunks, until we're done.
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//
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std::deque<unsigned char>::const_iterator I = Buffer.begin(),E = Buffer.end();
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while (I != E) { // Loop until it's all written
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// Scan to see how big this chunk is...
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const unsigned char *ChunkPtr = &*I;
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const unsigned char *LastPtr = ChunkPtr;
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while (I != E) {
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const unsigned char *ThisPtr = &*++I;
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if (LastPtr+1 != ThisPtr) { // Advanced by more than a byte of memory?
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++LastPtr;
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break;
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}
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LastPtr = ThisPtr;
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}
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// Write out the chunk...
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Out.write((char*)ChunkPtr, LastPtr-ChunkPtr);
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}
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Out.flush();
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}
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