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llvm-6502/lib/Target/X86/X86ISelSimple.cpp
Chris Lattner 89fab07abd Don't force setCC instructions into AL 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5104 91177308-0d34-0410-b5e6-96231b3b80d8
2002-12-18 01:44:31 +00:00

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//===-- InstSelectSimple.cpp - A simple instruction selector for x86 ------===//
//
// This file defines a simple peephole instruction selector for the x86 platform
//
//===----------------------------------------------------------------------===//
#include "X86.h"
#include "X86InstrInfo.h"
#include "X86InstrBuilder.h"
#include "llvm/Function.h"
#include "llvm/iTerminators.h"
#include "llvm/iOperators.h"
#include "llvm/iOther.h"
#include "llvm/iPHINode.h"
#include "llvm/iMemory.h"
#include "llvm/Type.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Constants.h"
#include "llvm/Pass.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Target/MRegisterInfo.h"
#include <map>
using namespace MOTy; // Get Use, Def, UseAndDef
/// BMI - A special BuildMI variant that takes an iterator to insert the
/// instruction at as well as a basic block.
/// this is the version for when you have a destination register in mind.
inline static MachineInstrBuilder BMI(MachineBasicBlock *MBB,
MachineBasicBlock::iterator &I,
MachineOpCode Opcode,
unsigned NumOperands,
unsigned DestReg) {
assert(I >= MBB->begin() && I <= MBB->end() && "Bad iterator!");
MachineInstr *MI = new MachineInstr(Opcode, NumOperands+1, true, true);
I = ++MBB->insert(I, MI);
return MachineInstrBuilder(MI).addReg(DestReg, MOTy::Def);
}
/// BMI - A special BuildMI variant that takes an iterator to insert the
/// instruction at as well as a basic block.
inline static MachineInstrBuilder BMI(MachineBasicBlock *MBB,
MachineBasicBlock::iterator &I,
MachineOpCode Opcode,
unsigned NumOperands) {
assert(I > MBB->begin() && I <= MBB->end() && "Bad iterator!");
MachineInstr *MI = new MachineInstr(Opcode, NumOperands, true, true);
I = ++MBB->insert(I, MI);
return MachineInstrBuilder(MI);
}
namespace {
struct ISel : public FunctionPass, InstVisitor<ISel> {
TargetMachine &TM;
MachineFunction *F; // The function we are compiling into
MachineBasicBlock *BB; // The current MBB we are compiling
unsigned CurReg;
std::map<Value*, unsigned> RegMap; // Mapping between Val's and SSA Regs
// MBBMap - Mapping between LLVM BB -> Machine BB
std::map<const BasicBlock*, MachineBasicBlock*> MBBMap;
ISel(TargetMachine &tm)
: TM(tm), F(0), BB(0), CurReg(MRegisterInfo::FirstVirtualRegister) {}
/// runOnFunction - Top level implementation of instruction selection for
/// the entire function.
///
bool runOnFunction(Function &Fn) {
F = &MachineFunction::construct(&Fn, TM);
for (Function::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I)
F->getBasicBlockList().push_back(MBBMap[I] = new MachineBasicBlock(I));
// Emit instructions to load the arguments... The function's arguments
// look like this:
//
// [EBP] -- copy of old EBP
// [EBP + 4] -- return address
// [EBP + 8] -- first argument (leftmost lexically)
//
// So we want to start with counter = 2.
//
BB = &F->front();
unsigned ArgOffset = 8;
for (Function::aiterator I = Fn.abegin(), E = Fn.aend(); I != E;
++I, ArgOffset += 4) {
unsigned Reg = getReg(*I);
// Load it out of the stack frame at EBP + 4*argPos.
// FIXME: This should load the argument of the appropriate size!!
addRegOffset(BuildMI(BB, X86::MOVmr32, 4, Reg), X86::EBP, ArgOffset);
}
// Instruction select everything except PHI nodes
visit(Fn);
// Select the PHI nodes
SelectPHINodes();
RegMap.clear();
MBBMap.clear();
CurReg = MRegisterInfo::FirstVirtualRegister;
F = 0;
return false; // We never modify the LLVM itself.
}
virtual const char *getPassName() const {
return "X86 Simple Instruction Selection";
}
/// visitBasicBlock - This method is called when we are visiting a new basic
/// block. This simply creates a new MachineBasicBlock to emit code into
/// and adds it to the current MachineFunction. Subsequent visit* for
/// instructions will be invoked for all instructions in the basic block.
///
void visitBasicBlock(BasicBlock &LLVM_BB) {
BB = MBBMap[&LLVM_BB];
}
/// SelectPHINodes - Insert machine code to generate phis. This is tricky
/// because we have to generate our sources into the source basic blocks,
/// not the current one.
///
void SelectPHINodes();
// Visitation methods for various instructions. These methods simply emit
// fixed X86 code for each instruction.
//
// Control flow operators
void visitReturnInst(ReturnInst &RI);
void visitBranchInst(BranchInst &BI);
void visitCallInst(CallInst &I);
// Arithmetic operators
void visitSimpleBinary(BinaryOperator &B, unsigned OpcodeClass);
void visitAdd(BinaryOperator &B) { visitSimpleBinary(B, 0); }
void visitSub(BinaryOperator &B) { visitSimpleBinary(B, 1); }
void doMultiply(MachineBasicBlock *MBB, MachineBasicBlock::iterator &MBBI,
unsigned destReg, const Type *resultType,
unsigned op0Reg, unsigned op1Reg);
void visitMul(BinaryOperator &B);
void visitDiv(BinaryOperator &B) { visitDivRem(B); }
void visitRem(BinaryOperator &B) { visitDivRem(B); }
void visitDivRem(BinaryOperator &B);
// Bitwise operators
void visitAnd(BinaryOperator &B) { visitSimpleBinary(B, 2); }
void visitOr (BinaryOperator &B) { visitSimpleBinary(B, 3); }
void visitXor(BinaryOperator &B) { visitSimpleBinary(B, 4); }
// Binary comparison operators
void visitSetCCInst(SetCondInst &I, unsigned OpNum);
void visitSetEQ(SetCondInst &I) { visitSetCCInst(I, 0); }
void visitSetNE(SetCondInst &I) { visitSetCCInst(I, 1); }
void visitSetLT(SetCondInst &I) { visitSetCCInst(I, 2); }
void visitSetGT(SetCondInst &I) { visitSetCCInst(I, 3); }
void visitSetLE(SetCondInst &I) { visitSetCCInst(I, 4); }
void visitSetGE(SetCondInst &I) { visitSetCCInst(I, 5); }
// Memory Instructions
void visitLoadInst(LoadInst &I);
void visitStoreInst(StoreInst &I);
void visitGetElementPtrInst(GetElementPtrInst &I);
void visitMallocInst(MallocInst &I);
void visitFreeInst(FreeInst &I);
void visitAllocaInst(AllocaInst &I);
// Other operators
void visitShiftInst(ShiftInst &I);
void visitPHINode(PHINode &I) {} // PHI nodes handled by second pass
void visitCastInst(CastInst &I);
void visitInstruction(Instruction &I) {
std::cerr << "Cannot instruction select: " << I;
abort();
}
/// promote32 - Make a value 32-bits wide, and put it somewhere.
void promote32 (const unsigned targetReg, Value *v);
// emitGEPOperation - Common code shared between visitGetElementPtrInst and
// constant expression GEP support.
//
void emitGEPOperation(MachineBasicBlock *BB, MachineBasicBlock::iterator&IP,
Value *Src, User::op_iterator IdxBegin,
User::op_iterator IdxEnd, unsigned TargetReg);
/// copyConstantToRegister - Output the instructions required to put the
/// specified constant into the specified register.
///
void copyConstantToRegister(MachineBasicBlock *MBB,
MachineBasicBlock::iterator &MBBI,
Constant *C, unsigned Reg);
/// makeAnotherReg - This method returns the next register number
/// we haven't yet used.
unsigned makeAnotherReg(const Type *Ty) {
// Add the mapping of regnumber => reg class to MachineFunction
F->addRegMap(CurReg, TM.getRegisterInfo()->getRegClassForType(Ty));
return CurReg++;
}
/// getReg - This method turns an LLVM value into a register number. This
/// is guaranteed to produce the same register number for a particular value
/// every time it is queried.
///
unsigned getReg(Value &V) { return getReg(&V); } // Allow references
unsigned getReg(Value *V) {
// Just append to the end of the current bb.
MachineBasicBlock::iterator It = BB->end();
return getReg(V, BB, It);
}
unsigned getReg(Value *V, MachineBasicBlock *MBB,
MachineBasicBlock::iterator &IPt) {
unsigned &Reg = RegMap[V];
if (Reg == 0) {
Reg = makeAnotherReg(V->getType());
RegMap[V] = Reg;
}
// If this operand is a constant, emit the code to copy the constant into
// the register here...
//
if (Constant *C = dyn_cast<Constant>(V)) {
copyConstantToRegister(MBB, IPt, C, Reg);
RegMap.erase(V); // Assign a new name to this constant if ref'd again
} else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
// Move the address of the global into the register
BMI(MBB, IPt, X86::MOVir32, 1, Reg).addReg(GV);
RegMap.erase(V); // Assign a new name to this address if ref'd again
}
return Reg;
}
};
}
/// TypeClass - Used by the X86 backend to group LLVM types by their basic X86
/// Representation.
///
enum TypeClass {
cByte, cShort, cInt, cLong, cFloat, cDouble
};
/// getClass - Turn a primitive type into a "class" number which is based on the
/// size of the type, and whether or not it is floating point.
///
static inline TypeClass getClass(const Type *Ty) {
switch (Ty->getPrimitiveID()) {
case Type::SByteTyID:
case Type::UByteTyID: return cByte; // Byte operands are class #0
case Type::ShortTyID:
case Type::UShortTyID: return cShort; // Short operands are class #1
case Type::IntTyID:
case Type::UIntTyID:
case Type::PointerTyID: return cInt; // Int's and pointers are class #2
case Type::LongTyID:
case Type::ULongTyID: //return cLong; // Longs are class #3
return cInt; // FIXME: LONGS ARE TREATED AS INTS!
case Type::FloatTyID: return cFloat; // Float is class #4
case Type::DoubleTyID: return cDouble; // Doubles are class #5
default:
assert(0 && "Invalid type to getClass!");
return cByte; // not reached
}
}
// getClassB - Just like getClass, but treat boolean values as bytes.
static inline TypeClass getClassB(const Type *Ty) {
if (Ty == Type::BoolTy) return cByte;
return getClass(Ty);
}
/// copyConstantToRegister - Output the instructions required to put the
/// specified constant into the specified register.
///
void ISel::copyConstantToRegister(MachineBasicBlock *MBB,
MachineBasicBlock::iterator &IP,
Constant *C, unsigned R) {
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
if (CE->getOpcode() == Instruction::GetElementPtr) {
emitGEPOperation(MBB, IP, CE->getOperand(0),
CE->op_begin()+1, CE->op_end(), R);
return;
}
std::cerr << "Offending expr: " << C << "\n";
assert (0 && "Constant expressions not yet handled!\n");
}
if (C->getType()->isIntegral()) {
unsigned Class = getClassB(C->getType());
assert(Class != 3 && "Type not handled yet!");
static const unsigned IntegralOpcodeTab[] = {
X86::MOVir8, X86::MOVir16, X86::MOVir32
};
if (C->getType() == Type::BoolTy) {
BMI(MBB, IP, X86::MOVir8, 1, R).addZImm(C == ConstantBool::True);
} else if (C->getType()->isSigned()) {
ConstantSInt *CSI = cast<ConstantSInt>(C);
BMI(MBB, IP, IntegralOpcodeTab[Class], 1, R).addSImm(CSI->getValue());
} else {
ConstantUInt *CUI = cast<ConstantUInt>(C);
BMI(MBB, IP, IntegralOpcodeTab[Class], 1, R).addZImm(CUI->getValue());
}
} else if (isa<ConstantPointerNull>(C)) {
// Copy zero (null pointer) to the register.
BMI(MBB, IP, X86::MOVir32, 1, R).addZImm(0);
} else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(C)) {
unsigned SrcReg = getReg(CPR->getValue(), MBB, IP);
BMI(MBB, IP, X86::MOVrr32, 1, R).addReg(SrcReg);
} else {
std::cerr << "Offending constant: " << C << "\n";
assert(0 && "Type not handled yet!");
}
}
/// SelectPHINodes - Insert machine code to generate phis. This is tricky
/// because we have to generate our sources into the source basic blocks, not
/// the current one.
///
void ISel::SelectPHINodes() {
const Function &LF = *F->getFunction(); // The LLVM function...
for (Function::const_iterator I = LF.begin(), E = LF.end(); I != E; ++I) {
const BasicBlock *BB = I;
MachineBasicBlock *MBB = MBBMap[I];
// Loop over all of the PHI nodes in the LLVM basic block...
unsigned NumPHIs = 0;
for (BasicBlock::const_iterator I = BB->begin();
PHINode *PN = (PHINode*)dyn_cast<PHINode>(&*I); ++I) {
// Create a new machine instr PHI node, and insert it.
MachineInstr *MI = BuildMI(X86::PHI, PN->getNumOperands(), getReg(*PN));
MBB->insert(MBB->begin()+NumPHIs++, MI); // Insert it at the top of the BB
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
MachineBasicBlock *PredMBB = MBBMap[PN->getIncomingBlock(i)];
// Get the incoming value into a virtual register. If it is not already
// available in a virtual register, insert the computation code into
// PredMBB
//
MachineBasicBlock::iterator PI = PredMBB->begin();
while ((*PI)->getOpcode() == X86::PHI) ++PI;
MI->addRegOperand(getReg(PN->getIncomingValue(i), PredMBB, PI));
MI->addMachineBasicBlockOperand(PredMBB);
}
}
}
}
/// SetCC instructions - Here we just emit boilerplate code to set a byte-sized
/// register, then move it to wherever the result should be.
/// We handle FP setcc instructions by pushing them, doing a
/// compare-and-pop-twice, and then copying the concodes to the main
/// processor's concodes (I didn't make this up, it's in the Intel manual)
///
void ISel::visitSetCCInst(SetCondInst &I, unsigned OpNum) {
// The arguments are already supposed to be of the same type.
const Type *CompTy = I.getOperand(0)->getType();
unsigned reg1 = getReg(I.getOperand(0));
unsigned reg2 = getReg(I.getOperand(1));
unsigned Class = getClass(CompTy);
switch (Class) {
// Emit: cmp <var1>, <var2> (do the comparison). We can
// compare 8-bit with 8-bit, 16-bit with 16-bit, 32-bit with
// 32-bit.
case cByte:
BuildMI (BB, X86::CMPrr8, 2).addReg (reg1).addReg (reg2);
break;
case cShort:
BuildMI (BB, X86::CMPrr16, 2).addReg (reg1).addReg (reg2);
break;
case cInt:
BuildMI (BB, X86::CMPrr32, 2).addReg (reg1).addReg (reg2);
break;
// Push the variables on the stack with fldl opcodes.
// FIXME: assuming var1, var2 are in memory, if not, spill to
// stack first
case cFloat: // Floats
BuildMI (BB, X86::FLDr32, 1).addReg (reg1);
BuildMI (BB, X86::FLDr32, 1).addReg (reg2);
break;
case cDouble: // Doubles
BuildMI (BB, X86::FLDr64, 1).addReg (reg1);
BuildMI (BB, X86::FLDr64, 1).addReg (reg2);
break;
case cLong:
default:
visitInstruction(I);
}
if (CompTy->isFloatingPoint()) {
// (Non-trapping) compare and pop twice.
BuildMI (BB, X86::FUCOMPP, 0);
// Move fp status word (concodes) to ax.
BuildMI (BB, X86::FNSTSWr8, 1, X86::AX);
// Load real concodes from ax.
BuildMI (BB, X86::SAHF, 1).addReg(X86::AH);
}
// Emit setOp instruction (extract concode; clobbers ax),
// using the following mapping:
// LLVM -> X86 signed X86 unsigned
// ----- ----- -----
// seteq -> sete sete
// setne -> setne setne
// setlt -> setl setb
// setgt -> setg seta
// setle -> setle setbe
// setge -> setge setae
static const unsigned OpcodeTab[2][6] = {
{X86::SETEr, X86::SETNEr, X86::SETBr, X86::SETAr, X86::SETBEr, X86::SETAEr},
{X86::SETEr, X86::SETNEr, X86::SETLr, X86::SETGr, X86::SETLEr, X86::SETGEr},
};
BuildMI(BB, OpcodeTab[CompTy->isSigned()][OpNum], 0, getReg(I));
}
/// promote32 - Emit instructions to turn a narrow operand into a 32-bit-wide
/// operand, in the specified target register.
void
ISel::promote32 (unsigned targetReg, Value *v)
{
unsigned vReg = getReg (v);
unsigned Class = getClass (v->getType ());
bool isUnsigned = v->getType ()->isUnsigned ();
assert (((Class == cByte) || (Class == cShort) || (Class == cInt))
&& "Unpromotable operand class in promote32");
switch (Class)
{
case cByte:
// Extend value into target register (8->32)
if (isUnsigned)
BuildMI (BB, X86::MOVZXr32r8, 1, targetReg).addReg (vReg);
else
BuildMI (BB, X86::MOVSXr32r8, 1, targetReg).addReg (vReg);
break;
case cShort:
// Extend value into target register (16->32)
if (isUnsigned)
BuildMI (BB, X86::MOVZXr32r16, 1, targetReg).addReg (vReg);
else
BuildMI (BB, X86::MOVSXr32r16, 1, targetReg).addReg (vReg);
break;
case cInt:
// Move value into target register (32->32)
BuildMI (BB, X86::MOVrr32, 1, targetReg).addReg (vReg);
break;
}
}
/// 'ret' instruction - Here we are interested in meeting the x86 ABI. As such,
/// we have the following possibilities:
///
/// ret void: No return value, simply emit a 'ret' instruction
/// ret sbyte, ubyte : Extend value into EAX and return
/// ret short, ushort: Extend value into EAX and return
/// ret int, uint : Move value into EAX and return
/// ret pointer : Move value into EAX and return
/// ret long, ulong : Move value into EAX/EDX and return
/// ret float/double : Top of FP stack
///
void
ISel::visitReturnInst (ReturnInst &I)
{
if (I.getNumOperands () == 0)
{
// Emit a 'ret' instruction
BuildMI (BB, X86::RET, 0);
return;
}
Value *rv = I.getOperand (0);
unsigned Class = getClass (rv->getType ());
switch (Class)
{
// integral return values: extend or move into EAX and return.
case cByte:
case cShort:
case cInt:
promote32 (X86::EAX, rv);
break;
// ret float/double: top of FP stack
// FLD <val>
case cFloat: // Floats
BuildMI (BB, X86::FLDr32, 1).addReg (getReg (rv));
break;
case cDouble: // Doubles
BuildMI (BB, X86::FLDr64, 1).addReg (getReg (rv));
break;
case cLong:
// ret long: use EAX(least significant 32 bits)/EDX (most
// significant 32)...uh, I think so Brain, but how do i call
// up the two parts of the value from inside this mouse
// cage? *zort*
default:
visitInstruction (I);
}
// Emit a 'ret' instruction
BuildMI (BB, X86::RET, 0);
}
/// visitBranchInst - Handle conditional and unconditional branches here. Note
/// that since code layout is frozen at this point, that if we are trying to
/// jump to a block that is the immediate successor of the current block, we can
/// just make a fall-through. (but we don't currently).
///
void
ISel::visitBranchInst (BranchInst & BI)
{
if (BI.isConditional ())
{
BasicBlock *ifTrue = BI.getSuccessor (0);
BasicBlock *ifFalse = BI.getSuccessor (1); // this is really unobvious
// simplest thing I can think of: compare condition with zero,
// followed by jump-if-equal to ifFalse, and jump-if-nonequal to
// ifTrue
unsigned int condReg = getReg (BI.getCondition ());
BuildMI (BB, X86::CMPri8, 2).addReg (condReg).addZImm (0);
BuildMI (BB, X86::JNE, 1).addPCDisp (BI.getSuccessor (0));
BuildMI (BB, X86::JE, 1).addPCDisp (BI.getSuccessor (1));
}
else // unconditional branch
{
BuildMI (BB, X86::JMP, 1).addPCDisp (BI.getSuccessor (0));
}
}
/// visitCallInst - Push args on stack and do a procedure call instruction.
void
ISel::visitCallInst (CallInst & CI)
{
// keep a counter of how many bytes we pushed on the stack
unsigned bytesPushed = 0;
// Push the arguments on the stack in reverse order, as specified by
// the ABI.
for (unsigned i = CI.getNumOperands()-1; i >= 1; --i)
{
Value *v = CI.getOperand (i);
switch (getClass (v->getType ()))
{
case cByte:
case cShort:
// Promote V to 32 bits wide, and move the result into EAX,
// then push EAX.
promote32 (X86::EAX, v);
BuildMI (BB, X86::PUSHr32, 1).addReg (X86::EAX);
bytesPushed += 4;
break;
case cInt:
case cFloat: {
unsigned Reg = getReg(v);
BuildMI (BB, X86::PUSHr32, 1).addReg(Reg);
bytesPushed += 4;
break;
}
default:
// FIXME: long/ulong/double args not handled.
visitInstruction (CI);
break;
}
}
if (Function *F = CI.getCalledFunction()) {
// Emit a CALL instruction with PC-relative displacement.
BuildMI(BB, X86::CALLpcrel32, 1).addPCDisp(F);
} else {
unsigned Reg = getReg(CI.getCalledValue());
BuildMI(BB, X86::CALLr32, 1).addReg(Reg);
}
// Adjust the stack by `bytesPushed' amount if non-zero
if (bytesPushed > 0)
BuildMI (BB, X86::ADDri32,2,X86::ESP).addReg(X86::ESP).addZImm(bytesPushed);
// If there is a return value, scavenge the result from the location the call
// leaves it in...
//
if (CI.getType() != Type::VoidTy) {
unsigned resultTypeClass = getClass (CI.getType ());
switch (resultTypeClass) {
case cByte:
case cShort:
case cInt: {
// Integral results are in %eax, or the appropriate portion
// thereof.
static const unsigned regRegMove[] = {
X86::MOVrr8, X86::MOVrr16, X86::MOVrr32
};
static const unsigned AReg[] = { X86::AL, X86::AX, X86::EAX };
BuildMI (BB, regRegMove[resultTypeClass], 1,
getReg (CI)).addReg (AReg[resultTypeClass]);
break;
}
case cFloat:
// Floating-point return values live in %st(0) (i.e., the top of
// the FP stack.) The general way to approach this is to do a
// FSTP to save the top of the FP stack on the real stack, then
// do a MOV to load the top of the real stack into the target
// register.
visitInstruction (CI); // FIXME: add the right args for the calls below
// BuildMI (BB, X86::FSTPm32, 0);
// BuildMI (BB, X86::MOVmr32, 0);
break;
default:
std::cerr << "Cannot get return value for call of type '"
<< *CI.getType() << "'\n";
visitInstruction(CI);
}
}
}
/// visitSimpleBinary - Implement simple binary operators for integral types...
/// OperatorClass is one of: 0 for Add, 1 for Sub, 2 for And, 3 for Or,
/// 4 for Xor.
///
void ISel::visitSimpleBinary(BinaryOperator &B, unsigned OperatorClass) {
if (B.getType() == Type::BoolTy) // FIXME: Handle bools for logicals
visitInstruction(B);
unsigned Class = getClass(B.getType());
if (Class > 2) // FIXME: Handle longs
visitInstruction(B);
static const unsigned OpcodeTab[][4] = {
// Arithmetic operators
{ X86::ADDrr8, X86::ADDrr16, X86::ADDrr32, 0 }, // ADD
{ X86::SUBrr8, X86::SUBrr16, X86::SUBrr32, 0 }, // SUB
// Bitwise operators
{ X86::ANDrr8, X86::ANDrr16, X86::ANDrr32, 0 }, // AND
{ X86:: ORrr8, X86:: ORrr16, X86:: ORrr32, 0 }, // OR
{ X86::XORrr8, X86::XORrr16, X86::XORrr32, 0 }, // XOR
};
unsigned Opcode = OpcodeTab[OperatorClass][Class];
unsigned Op0r = getReg(B.getOperand(0));
unsigned Op1r = getReg(B.getOperand(1));
BuildMI(BB, Opcode, 2, getReg(B)).addReg(Op0r).addReg(Op1r);
}
/// doMultiply - Emit appropriate instructions to multiply together
/// the registers op0Reg and op1Reg, and put the result in destReg.
/// The type of the result should be given as resultType.
void ISel::doMultiply(MachineBasicBlock *MBB, MachineBasicBlock::iterator &MBBI,
unsigned destReg, const Type *resultType,
unsigned op0Reg, unsigned op1Reg) {
unsigned Class = getClass (resultType);
// FIXME:
assert (Class <= 2 && "Someday, we will learn how to multiply"
"longs and floating-point numbers. This is not that day.");
static const unsigned Regs[] ={ X86::AL , X86::AX , X86::EAX };
static const unsigned MulOpcode[]={ X86::MULrr8, X86::MULrr16, X86::MULrr32 };
static const unsigned MovOpcode[]={ X86::MOVrr8, X86::MOVrr16, X86::MOVrr32 };
unsigned Reg = Regs[Class];
// Emit a MOV to put the first operand into the appropriately-sized
// subreg of EAX.
BMI(MBB, MBBI, MovOpcode[Class], 1, Reg).addReg (op0Reg);
// Emit the appropriate multiply instruction.
BMI(MBB, MBBI, MulOpcode[Class], 1).addReg (op1Reg);
// Emit another MOV to put the result into the destination register.
BMI(MBB, MBBI, MovOpcode[Class], 1, destReg).addReg (Reg);
}
/// visitMul - Multiplies are not simple binary operators because they must deal
/// with the EAX register explicitly.
///
void ISel::visitMul(BinaryOperator &I) {
unsigned DestReg = getReg(I);
unsigned Op0Reg = getReg(I.getOperand(0));
unsigned Op1Reg = getReg(I.getOperand(1));
MachineBasicBlock::iterator MBBI = BB->end();
doMultiply(BB, MBBI, DestReg, I.getType(), Op0Reg, Op1Reg);
}
/// visitDivRem - Handle division and remainder instructions... these
/// instruction both require the same instructions to be generated, they just
/// select the result from a different register. Note that both of these
/// instructions work differently for signed and unsigned operands.
///
void ISel::visitDivRem(BinaryOperator &I) {
unsigned Class = getClass(I.getType());
if (Class > 2) // FIXME: Handle longs
visitInstruction(I);
static const unsigned Regs[] ={ X86::AL , X86::AX , X86::EAX };
static const unsigned MovOpcode[]={ X86::MOVrr8, X86::MOVrr16, X86::MOVrr32 };
static const unsigned ExtOpcode[]={ X86::CBW , X86::CWD , X86::CDQ };
static const unsigned ClrOpcode[]={ X86::XORrr8, X86::XORrr16, X86::XORrr32 };
static const unsigned ExtRegs[] ={ X86::AH , X86::DX , X86::EDX };
static const unsigned DivOpcode[][4] = {
{ X86::DIVrr8 , X86::DIVrr16 , X86::DIVrr32 , 0 }, // Unsigned division
{ X86::IDIVrr8, X86::IDIVrr16, X86::IDIVrr32, 0 }, // Signed division
};
bool isSigned = I.getType()->isSigned();
unsigned Reg = Regs[Class];
unsigned ExtReg = ExtRegs[Class];
unsigned Op0Reg = getReg(I.getOperand(0));
unsigned Op1Reg = getReg(I.getOperand(1));
// Put the first operand into one of the A registers...
BuildMI(BB, MovOpcode[Class], 1, Reg).addReg(Op0Reg);
if (isSigned) {
// Emit a sign extension instruction...
BuildMI(BB, ExtOpcode[Class], 0);
} else {
// If unsigned, emit a zeroing instruction... (reg = xor reg, reg)
BuildMI(BB, ClrOpcode[Class], 2, ExtReg).addReg(ExtReg).addReg(ExtReg);
}
// Emit the appropriate divide or remainder instruction...
BuildMI(BB, DivOpcode[isSigned][Class], 1).addReg(Op1Reg);
// Figure out which register we want to pick the result out of...
unsigned DestReg = (I.getOpcode() == Instruction::Div) ? Reg : ExtReg;
// Put the result into the destination register...
BuildMI(BB, MovOpcode[Class], 1, getReg(I)).addReg(DestReg);
}
/// Shift instructions: 'shl', 'sar', 'shr' - Some special cases here
/// for constant immediate shift values, and for constant immediate
/// shift values equal to 1. Even the general case is sort of special,
/// because the shift amount has to be in CL, not just any old register.
///
void ISel::visitShiftInst (ShiftInst &I) {
unsigned Op0r = getReg (I.getOperand(0));
unsigned DestReg = getReg(I);
bool isLeftShift = I.getOpcode() == Instruction::Shl;
bool isOperandSigned = I.getType()->isUnsigned();
unsigned OperandClass = getClass(I.getType());
if (OperandClass > 2)
visitInstruction(I); // Can't handle longs yet!
if (ConstantUInt *CUI = dyn_cast <ConstantUInt> (I.getOperand (1)))
{
// The shift amount is constant, guaranteed to be a ubyte. Get its value.
assert(CUI->getType() == Type::UByteTy && "Shift amount not a ubyte?");
unsigned char shAmt = CUI->getValue();
static const unsigned ConstantOperand[][4] = {
{ X86::SHRir8, X86::SHRir16, X86::SHRir32, 0 }, // SHR
{ X86::SARir8, X86::SARir16, X86::SARir32, 0 }, // SAR
{ X86::SHLir8, X86::SHLir16, X86::SHLir32, 0 }, // SHL
{ X86::SHLir8, X86::SHLir16, X86::SHLir32, 0 }, // SAL = SHL
};
const unsigned *OpTab = // Figure out the operand table to use
ConstantOperand[isLeftShift*2+isOperandSigned];
// Emit: <insn> reg, shamt (shift-by-immediate opcode "ir" form.)
BuildMI(BB, OpTab[OperandClass], 2, DestReg).addReg(Op0r).addZImm(shAmt);
}
else
{
// The shift amount is non-constant.
//
// In fact, you can only shift with a variable shift amount if
// that amount is already in the CL register, so we have to put it
// there first.
//
// Emit: move cl, shiftAmount (put the shift amount in CL.)
BuildMI(BB, X86::MOVrr8, 1, X86::CL).addReg(getReg(I.getOperand(1)));
// This is a shift right (SHR).
static const unsigned NonConstantOperand[][4] = {
{ X86::SHRrr8, X86::SHRrr16, X86::SHRrr32, 0 }, // SHR
{ X86::SARrr8, X86::SARrr16, X86::SARrr32, 0 }, // SAR
{ X86::SHLrr8, X86::SHLrr16, X86::SHLrr32, 0 }, // SHL
{ X86::SHLrr8, X86::SHLrr16, X86::SHLrr32, 0 }, // SAL = SHL
};
const unsigned *OpTab = // Figure out the operand table to use
NonConstantOperand[isLeftShift*2+isOperandSigned];
BuildMI(BB, OpTab[OperandClass], 1, DestReg).addReg(Op0r);
}
}
/// visitLoadInst - Implement LLVM load instructions in terms of the x86 'mov'
/// instruction.
///
void ISel::visitLoadInst(LoadInst &I) {
unsigned Class = getClass(I.getType());
if (Class > 2) // FIXME: Handle longs and others...
visitInstruction(I);
static const unsigned Opcode[] = { X86::MOVmr8, X86::MOVmr16, X86::MOVmr32 };
unsigned AddressReg = getReg(I.getOperand(0));
addDirectMem(BuildMI(BB, Opcode[Class], 4, getReg(I)), AddressReg);
}
/// visitStoreInst - Implement LLVM store instructions in terms of the x86 'mov'
/// instruction.
///
void ISel::visitStoreInst(StoreInst &I) {
unsigned Class = getClass(I.getOperand(0)->getType());
if (Class > 2) // FIXME: Handle longs and others...
visitInstruction(I);
static const unsigned Opcode[] = { X86::MOVrm8, X86::MOVrm16, X86::MOVrm32 };
unsigned ValReg = getReg(I.getOperand(0));
unsigned AddressReg = getReg(I.getOperand(1));
addDirectMem(BuildMI(BB, Opcode[Class], 1+4), AddressReg).addReg(ValReg);
}
/// visitCastInst - Here we have various kinds of copying with or without
/// sign extension going on.
void
ISel::visitCastInst (CastInst &CI)
{
const Type *targetType = CI.getType ();
Value *operand = CI.getOperand (0);
unsigned int operandReg = getReg (operand);
const Type *sourceType = operand->getType ();
unsigned int destReg = getReg (CI);
//
// Currently we handle:
//
// 1) cast * to bool
//
// 2) cast {sbyte, ubyte} to {sbyte, ubyte}
// cast {short, ushort} to {ushort, short}
// cast {int, uint, ptr} to {int, uint, ptr}
//
// 3) cast {sbyte, ubyte} to {ushort, short}
// cast {sbyte, ubyte} to {int, uint, ptr}
// cast {short, ushort} to {int, uint, ptr}
//
// 4) cast {int, uint, ptr} to {short, ushort}
// cast {int, uint, ptr} to {sbyte, ubyte}
// cast {short, ushort} to {sbyte, ubyte}
// 1) Implement casts to bool by using compare on the operand followed
// by set if not zero on the result.
if (targetType == Type::BoolTy)
{
BuildMI (BB, X86::CMPri8, 2).addReg (operandReg).addZImm (0);
BuildMI (BB, X86::SETNEr, 1, destReg);
return;
}
// 2) Implement casts between values of the same type class (as determined
// by getClass) by using a register-to-register move.
unsigned srcClass = getClassB (sourceType);
unsigned targClass = getClass (targetType);
static const unsigned regRegMove[] = {
X86::MOVrr8, X86::MOVrr16, X86::MOVrr32
};
if ((srcClass < cLong) && (targClass < cLong) && (srcClass == targClass))
{
BuildMI (BB, regRegMove[srcClass], 1, destReg).addReg (operandReg);
return;
}
// 3) Handle cast of SMALLER int to LARGER int using a move with sign
// extension or zero extension, depending on whether the source type
// was signed.
if ((srcClass < cLong) && (targClass < cLong) && (srcClass < targClass))
{
static const unsigned ops[] = {
X86::MOVSXr16r8, X86::MOVSXr32r8, X86::MOVSXr32r16,
X86::MOVZXr16r8, X86::MOVZXr32r8, X86::MOVZXr32r16
};
unsigned srcSigned = sourceType->isSigned ();
BuildMI (BB, ops[3 * srcSigned + srcClass + targClass - 1], 1,
destReg).addReg (operandReg);
return;
}
// 4) Handle cast of LARGER int to SMALLER int using a move to EAX
// followed by a move out of AX or AL.
if ((srcClass < cLong) && (targClass < cLong) && (srcClass > targClass))
{
static const unsigned AReg[] = { X86::AL, X86::AX, X86::EAX };
BuildMI (BB, regRegMove[srcClass], 1,
AReg[srcClass]).addReg (operandReg);
BuildMI (BB, regRegMove[targClass], 1, destReg).addReg (AReg[srcClass]);
return;
}
// Anything we haven't handled already, we can't (yet) handle at all.
//
// FP to integral casts can be handled with FISTP to store onto the
// stack while converting to integer, followed by a MOV to load from
// the stack into the result register. Integral to FP casts can be
// handled with MOV to store onto the stack, followed by a FILD to
// load from the stack while converting to FP. For the moment, I
// can't quite get straight in my head how to borrow myself some
// stack space and write on it. Otherwise, this would be trivial.
visitInstruction (CI);
}
// ExactLog2 - This function solves for (Val == 1 << (N-1)) and returns N. It
// returns zero when the input is not exactly a power of two.
static unsigned ExactLog2(unsigned Val) {
if (Val == 0) return 0;
unsigned Count = 0;
while (Val != 1) {
if (Val & 1) return 0;
Val >>= 1;
++Count;
}
return Count+1;
}
/// visitGetElementPtrInst - I don't know, most programs don't have
/// getelementptr instructions, right? That means we can put off
/// implementing this, right? Right. This method emits machine
/// instructions to perform type-safe pointer arithmetic. I am
/// guessing this could be cleaned up somewhat to use fewer temporary
/// registers.
void
ISel::visitGetElementPtrInst (GetElementPtrInst &I)
{
unsigned outputReg = getReg (I);
MachineBasicBlock::iterator MI = BB->end();
emitGEPOperation(BB, MI, I.getOperand(0),
I.op_begin()+1, I.op_end(), outputReg);
}
void ISel::emitGEPOperation(MachineBasicBlock *MBB,
MachineBasicBlock::iterator &IP,
Value *Src, User::op_iterator IdxBegin,
User::op_iterator IdxEnd, unsigned TargetReg) {
const TargetData &TD = TM.getTargetData();
const Type *Ty = Src->getType();
unsigned basePtrReg = getReg(Src, MBB, IP);
// GEPs have zero or more indices; we must perform a struct access
// or array access for each one.
for (GetElementPtrInst::op_iterator oi = IdxBegin,
oe = IdxEnd; oi != oe; ++oi) {
Value *idx = *oi;
unsigned nextBasePtrReg = makeAnotherReg(Type::UIntTy);
if (const StructType *StTy = dyn_cast <StructType> (Ty)) {
// It's a struct access. idx is the index into the structure,
// which names the field. This index must have ubyte type.
const ConstantUInt *CUI = cast <ConstantUInt> (idx);
assert (CUI->getType () == Type::UByteTy
&& "Funny-looking structure index in GEP");
// Use the TargetData structure to pick out what the layout of
// the structure is in memory. Since the structure index must
// be constant, we can get its value and use it to find the
// right byte offset from the StructLayout class's list of
// structure member offsets.
unsigned idxValue = CUI->getValue ();
unsigned memberOffset =
TD.getStructLayout (StTy)->MemberOffsets[idxValue];
// Emit an ADD to add memberOffset to the basePtr.
BMI(MBB, IP, X86::ADDri32, 2,
nextBasePtrReg).addReg (basePtrReg).addZImm (memberOffset);
// The next type is the member of the structure selected by the
// index.
Ty = StTy->getElementTypes ()[idxValue];
} else if (const SequentialType *SqTy = cast <SequentialType>(Ty)) {
// It's an array or pointer access: [ArraySize x ElementType].
// idx is the index into the array. Unlike with structure
// indices, we may not know its actual value at code-generation
// time.
assert(idx->getType() == Type::LongTy && "Bad GEP array index!");
// We want to add basePtrReg to (idxReg * sizeof ElementType). First, we
// must find the size of the pointed-to type (Not coincidentally, the next
// type is the type of the elements in the array).
Ty = SqTy->getElementType();
unsigned elementSize = TD.getTypeSize(Ty);
// If idxReg is a constant, we don't need to perform the multiply!
if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(idx)) {
if (CSI->isNullValue()) {
BMI(MBB, IP, X86::MOVrr32, 1, nextBasePtrReg).addReg(basePtrReg);
} else {
unsigned Offset = elementSize*CSI->getValue();
BMI(MBB, IP, X86::ADDri32, 2,
nextBasePtrReg).addReg(basePtrReg).addZImm(Offset);
}
} else if (elementSize == 1) {
// If the element size is 1, we don't have to multiply, just add
unsigned idxReg = getReg(idx, MBB, IP);
BMI(MBB, IP, X86::ADDrr32, 2,
nextBasePtrReg).addReg(basePtrReg).addReg(idxReg);
} else {
unsigned idxReg = getReg(idx, MBB, IP);
unsigned OffsetReg = makeAnotherReg(Type::UIntTy);
if (unsigned Shift = ExactLog2(elementSize)) {
// If the element size is exactly a power of 2, use a shift to get it.
BMI(MBB, IP, X86::SHLir32, 2,
OffsetReg).addReg(idxReg).addZImm(Shift-1);
} else {
// Most general case, emit a multiply...
unsigned elementSizeReg = makeAnotherReg(Type::LongTy);
BMI(MBB, IP, X86::MOVir32, 1, elementSizeReg).addZImm(elementSize);
// Emit a MUL to multiply the register holding the index by
// elementSize, putting the result in OffsetReg.
doMultiply(MBB, IP, OffsetReg, Type::LongTy, idxReg, elementSizeReg);
}
// Emit an ADD to add OffsetReg to the basePtr.
BMI(MBB, IP, X86::ADDrr32, 2,
nextBasePtrReg).addReg (basePtrReg).addReg (OffsetReg);
}
}
// Now that we are here, further indices refer to subtypes of this
// one, so we don't need to worry about basePtrReg itself, anymore.
basePtrReg = nextBasePtrReg;
}
// After we have processed all the indices, the result is left in
// basePtrReg. Move it to the register where we were expected to
// put the answer. A 32-bit move should do it, because we are in
// ILP32 land.
BMI(MBB, IP, X86::MOVrr32, 1, TargetReg).addReg (basePtrReg);
}
/// visitMallocInst - I know that personally, whenever I want to remember
/// something, I have to clear off some space in my brain.
void
ISel::visitMallocInst (MallocInst &I)
{
// We assume that by this point, malloc instructions have been
// lowered to calls, and dlsym will magically find malloc for us.
// So we do not want to see malloc instructions here.
visitInstruction (I);
}
/// visitFreeInst - same story as MallocInst
void
ISel::visitFreeInst (FreeInst &I)
{
// We assume that by this point, free instructions have been
// lowered to calls, and dlsym will magically find free for us.
// So we do not want to see free instructions here.
visitInstruction (I);
}
/// visitAllocaInst - I want some stack space. Come on, man, I said I
/// want some freakin' stack space.
void
ISel::visitAllocaInst (AllocaInst &I)
{
// Find the data size of the alloca inst's getAllocatedType.
const Type *allocatedType = I.getAllocatedType ();
const TargetData &TD = TM.DataLayout;
unsigned allocatedTypeSize = TD.getTypeSize (allocatedType);
// Keep stack 32-bit aligned.
unsigned int allocatedTypeWords = allocatedTypeSize / 4;
if (allocatedTypeSize % 4 != 0) { allocatedTypeWords++; }
// Subtract size from stack pointer, thereby allocating some space.
BuildMI(BB, X86::SUBri32, 2,
X86::ESP).addReg(X86::ESP).addZImm(allocatedTypeWords * 4);
// Put a pointer to the space into the result register, by copying
// the stack pointer.
BuildMI (BB, X86::MOVrr32, 1, getReg (I)).addReg (X86::ESP);
}
/// createSimpleX86InstructionSelector - This pass converts an LLVM function
/// into a machine code representation is a very simple peep-hole fashion. The
/// generated code sucks but the implementation is nice and simple.
///
Pass *createSimpleX86InstructionSelector(TargetMachine &TM) {
return new ISel(TM);
}
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