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277 lines
9.9 KiB
C++
277 lines
9.9 KiB
C++
//===-- WriteInst.cpp - Functions for writing instructions -------*- C++ -*--=//
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//
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// This file implements the routines for encoding instruction opcodes to a
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// bytecode stream.
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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/Module.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Instructions.h"
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#include "Support/Statistic.h"
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#include <algorithm>
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static Statistic<>
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NumInstrs("bytecodewriter", "Number of instructions");
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typedef unsigned char uchar;
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// outputInstructionFormat0 - Output those wierd instructions that have a large
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// number of operands or have large operands themselves...
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//
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// Format: [opcode] [type] [numargs] [arg0] [arg1] ... [arg<numargs-1>]
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//
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static void outputInstructionFormat0(const Instruction *I, unsigned Opcode,
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const SlotCalculator &Table,
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unsigned Type, std::deque<uchar> &Out) {
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// Opcode must have top two bits clear...
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output_vbr(Opcode << 2, Out); // Instruction Opcode ID
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output_vbr(Type, Out); // Result type
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unsigned NumArgs = I->getNumOperands();
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output_vbr(NumArgs + (isa<CastInst>(I) || isa<VarArgInst>(I)), Out);
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for (unsigned i = 0; i < NumArgs; ++i) {
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int Slot = Table.getValSlot(I->getOperand(i));
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assert(Slot >= 0 && "No slot number for value!?!?");
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output_vbr((unsigned)Slot, Out);
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}
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if (isa<CastInst>(I) || isa<VarArgInst>(I)) {
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int Slot = Table.getValSlot(I->getType());
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assert(Slot != -1 && "Cast/VarArg return type unknown?");
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output_vbr((unsigned)Slot, Out);
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}
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align32(Out); // We must maintain correct alignment!
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}
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// outputInstrVarArgsCall - Output the absurdly annoying varargs function calls.
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// This are more annoying than most because the signature of the call does not
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// tell us anything about the types of the arguments in the varargs portion.
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// Because of this, we encode (as type 0) all of the argument types explicitly
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// before the argument value. This really sucks, but you shouldn't be using
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// varargs functions in your code! *death to printf*!
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//
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// Format: [opcode] [type] [numargs] [arg0] [arg1] ... [arg<numargs-1>]
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//
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static void outputInstrVarArgsCall(const Instruction *I, unsigned Opcode,
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const SlotCalculator &Table, unsigned Type,
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std::deque<uchar> &Out) {
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assert(isa<CallInst>(I) || isa<InvokeInst>(I));
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// Opcode must have top two bits clear...
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output_vbr(Opcode << 2, Out); // Instruction Opcode ID
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output_vbr(Type, Out); // Result type (varargs type)
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unsigned NumArgs = I->getNumOperands();
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output_vbr(NumArgs*2, Out);
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// TODO: Don't need to emit types for the fixed types of the varargs function
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// prototype...
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// The type for the function has already been emitted in the type field of the
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// instruction. Just emit the slot # now.
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int Slot = Table.getValSlot(I->getOperand(0));
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assert(Slot >= 0 && "No slot number for value!?!?");
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output_vbr((unsigned)Slot, Out);
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// Output a dummy field to fill Arg#2 in the reader that is currently unused
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// for varargs calls. This is a gross hack to make the code simpler, but we
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// aren't really doing very small bytecode for varargs calls anyways.
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// FIXME in the future: Smaller bytecode for varargs calls
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output_vbr(0, Out);
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for (unsigned i = 1; i < NumArgs; ++i) {
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// Output Arg Type ID
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Slot = Table.getValSlot(I->getOperand(i)->getType());
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assert(Slot >= 0 && "No slot number for value!?!?");
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output_vbr((unsigned)Slot, Out);
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// Output arg ID itself
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Slot = Table.getValSlot(I->getOperand(i));
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assert(Slot >= 0 && "No slot number for value!?!?");
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output_vbr((unsigned)Slot, Out);
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}
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align32(Out); // We must maintain correct alignment!
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}
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// outputInstructionFormat1 - Output one operand instructions, knowing that no
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// operand index is >= 2^12.
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//
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static void outputInstructionFormat1(const Instruction *I, unsigned Opcode,
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const SlotCalculator &Table, int *Slots,
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unsigned Type, std::deque<uchar> &Out) {
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// bits Instruction format:
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// --------------------------
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// 01-00: Opcode type, fixed to 1.
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// 07-02: Opcode
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// 19-08: Resulting type plane
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// 31-20: Operand #1 (if set to (2^12-1), then zero operands)
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//
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unsigned Bits = 1 | (Opcode << 2) | (Type << 8) | (Slots[0] << 20);
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// cerr << "1 " << IType << " " << Type << " " << Slots[0] << endl;
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output(Bits, Out);
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}
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// outputInstructionFormat2 - Output two operand instructions, knowing that no
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// operand index is >= 2^8.
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//
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static void outputInstructionFormat2(const Instruction *I, unsigned Opcode,
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const SlotCalculator &Table, int *Slots,
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unsigned Type, std::deque<uchar> &Out) {
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// bits Instruction format:
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// --------------------------
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// 01-00: Opcode type, fixed to 2.
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// 07-02: Opcode
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// 15-08: Resulting type plane
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// 23-16: Operand #1
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// 31-24: Operand #2
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//
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unsigned Bits = 2 | (Opcode << 2) | (Type << 8) |
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(Slots[0] << 16) | (Slots[1] << 24);
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// cerr << "2 " << IType << " " << Type << " " << Slots[0] << " "
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// << Slots[1] << endl;
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output(Bits, Out);
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}
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// outputInstructionFormat3 - Output three operand instructions, knowing that no
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// operand index is >= 2^6.
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//
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static void outputInstructionFormat3(const Instruction *I, unsigned Opcode,
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const SlotCalculator &Table, int *Slots,
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unsigned Type, std::deque<uchar> &Out) {
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// bits Instruction format:
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// --------------------------
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// 01-00: Opcode type, fixed to 3.
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// 07-02: Opcode
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// 13-08: Resulting type plane
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// 19-14: Operand #1
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// 25-20: Operand #2
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// 31-26: Operand #3
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//
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unsigned Bits = 3 | (Opcode << 2) | (Type << 8) |
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(Slots[0] << 14) | (Slots[1] << 20) | (Slots[2] << 26);
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//cerr << "3 " << IType << " " << Type << " " << Slots[0] << " "
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// << Slots[1] << " " << Slots[2] << endl;
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output(Bits, Out);
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}
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void BytecodeWriter::processInstruction(const Instruction &I) {
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assert(I.getOpcode() < 62 && "Opcode too big???");
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unsigned Opcode = I.getOpcode();
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// Encode 'volatile load' as 62 and 'volatile store' as 63.
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if (isa<LoadInst>(I) && cast<LoadInst>(I).isVolatile())
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Opcode = 62;
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if (isa<StoreInst>(I) && cast<StoreInst>(I).isVolatile())
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Opcode = 63;
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unsigned NumOperands = I.getNumOperands();
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int MaxOpSlot = 0;
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int Slots[3]; Slots[0] = (1 << 12)-1; // Marker to signify 0 operands
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for (unsigned i = 0; i < NumOperands; ++i) {
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const Value *Def = I.getOperand(i);
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int slot = Table.getValSlot(Def);
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assert(slot != -1 && "Broken bytecode!");
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if (slot > MaxOpSlot) MaxOpSlot = slot;
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if (i < 3) Slots[i] = slot;
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}
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// Figure out which type to encode with the instruction. Typically we want
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// the type of the first parameter, as opposed to the type of the instruction
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// (for example, with setcc, we always know it returns bool, but the type of
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// the first param is actually interesting). But if we have no arguments
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// we take the type of the instruction itself.
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//
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const Type *Ty;
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switch (I.getOpcode()) {
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case Instruction::Malloc:
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case Instruction::Alloca:
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Ty = I.getType(); // Malloc & Alloca ALWAYS want to encode the return type
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break;
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case Instruction::Store:
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Ty = I.getOperand(1)->getType(); // Encode the pointer type...
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assert(isa<PointerType>(Ty) && "Store to nonpointer type!?!?");
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break;
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default: // Otherwise use the default behavior...
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Ty = NumOperands ? I.getOperand(0)->getType() : I.getType();
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break;
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}
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unsigned Type;
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int Slot = Table.getValSlot(Ty);
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assert(Slot != -1 && "Type not available!!?!");
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Type = (unsigned)Slot;
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// Make sure that we take the type number into consideration. We don't want
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// to overflow the field size for the instruction format we select.
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//
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if (Slot > MaxOpSlot) MaxOpSlot = Slot;
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// Handle the special case for cast...
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if (isa<CastInst>(I) || isa<VarArgInst>(I)) {
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// Cast has to encode the destination type as the second argument in the
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// packet, or else we won't know what type to cast to!
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Slots[1] = Table.getValSlot(I.getType());
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assert(Slots[1] != -1 && "Cast return type unknown?");
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if (Slots[1] > MaxOpSlot) MaxOpSlot = Slots[1];
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NumOperands++;
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} else if (const CallInst *CI = dyn_cast<CallInst>(&I)){// Handle VarArg calls
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const PointerType *Ty = cast<PointerType>(CI->getCalledValue()->getType());
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if (cast<FunctionType>(Ty->getElementType())->isVarArg()) {
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outputInstrVarArgsCall(CI, Opcode, Table, Type, Out);
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return;
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}
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} else if (const InvokeInst *II = dyn_cast<InvokeInst>(&I)) {// ... & Invokes
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const PointerType *Ty = cast<PointerType>(II->getCalledValue()->getType());
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if (cast<FunctionType>(Ty->getElementType())->isVarArg()) {
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outputInstrVarArgsCall(II, Opcode, Table, Type, Out);
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return;
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}
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}
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++NumInstrs;
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// Decide which instruction encoding to use. This is determined primarily by
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// the number of operands, and secondarily by whether or not the max operand
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// will fit into the instruction encoding. More operands == fewer bits per
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// operand.
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//
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switch (NumOperands) {
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case 0:
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case 1:
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if (MaxOpSlot < (1 << 12)-1) { // -1 because we use 4095 to indicate 0 ops
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outputInstructionFormat1(&I, Opcode, Table, Slots, Type, Out);
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return;
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}
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break;
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case 2:
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if (MaxOpSlot < (1 << 8)) {
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outputInstructionFormat2(&I, Opcode, Table, Slots, Type, Out);
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return;
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}
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break;
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case 3:
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if (MaxOpSlot < (1 << 6)) {
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outputInstructionFormat3(&I, Opcode, Table, Slots, Type, Out);
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return;
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}
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break;
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}
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// If we weren't handled before here, we either have a large number of
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// operands or a large operand index that we are referring to.
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outputInstructionFormat0(&I, Opcode, Table, Type, Out);
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}
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