1 //===-- InstSelectSimple.cpp - A simple instruction selector for x86 ------===//
3 // This file defines a simple peephole instruction selector for the x86 platform
5 //===----------------------------------------------------------------------===//
8 #include "X86InstrInfo.h"
9 #include "X86InstrBuilder.h"
10 #include "llvm/Function.h"
11 #include "llvm/iTerminators.h"
12 #include "llvm/iOperators.h"
13 #include "llvm/iOther.h"
14 #include "llvm/iPHINode.h"
15 #include "llvm/iMemory.h"
16 #include "llvm/Type.h"
17 #include "llvm/DerivedTypes.h"
18 #include "llvm/Constants.h"
19 #include "llvm/Pass.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineInstrBuilder.h"
22 #include "llvm/Target/TargetMachine.h"
23 #include "llvm/Support/InstVisitor.h"
24 #include "llvm/Target/MRegisterInfo.h"
27 using namespace MOTy; // Get Use, Def, UseAndDef
30 /// BMI - A special BuildMI variant that takes an iterator to insert the
31 /// instruction at as well as a basic block.
32 /// this is the version for when you have a destination register in mind.
33 inline static MachineInstrBuilder BMI(MachineBasicBlock *MBB,
34 MachineBasicBlock::iterator &I,
38 assert(I >= MBB->begin() && I <= MBB->end() && "Bad iterator!");
39 MachineInstr *MI = new MachineInstr(Opcode, NumOperands+1, true, true);
40 I = ++MBB->insert(I, MI);
41 return MachineInstrBuilder(MI).addReg(DestReg, MOTy::Def);
44 /// BMI - A special BuildMI variant that takes an iterator to insert the
45 /// instruction at as well as a basic block.
46 inline static MachineInstrBuilder BMI(MachineBasicBlock *MBB,
47 MachineBasicBlock::iterator &I,
49 unsigned NumOperands) {
50 assert(I > MBB->begin() && I <= MBB->end() && "Bad iterator!");
51 MachineInstr *MI = new MachineInstr(Opcode, NumOperands, true, true);
52 I = ++MBB->insert(I, MI);
53 return MachineInstrBuilder(MI);
58 struct ISel : public FunctionPass, InstVisitor<ISel> {
60 MachineFunction *F; // The function we are compiling into
61 MachineBasicBlock *BB; // The current MBB we are compiling
64 std::map<Value*, unsigned> RegMap; // Mapping between Val's and SSA Regs
66 // MBBMap - Mapping between LLVM BB -> Machine BB
67 std::map<const BasicBlock*, MachineBasicBlock*> MBBMap;
69 ISel(TargetMachine &tm)
70 : TM(tm), F(0), BB(0), CurReg(MRegisterInfo::FirstVirtualRegister) {}
72 /// runOnFunction - Top level implementation of instruction selection for
73 /// the entire function.
75 bool runOnFunction(Function &Fn) {
76 F = &MachineFunction::construct(&Fn, TM);
78 for (Function::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I)
79 F->getBasicBlockList().push_back(MBBMap[I] = new MachineBasicBlock(I));
81 // Instruction select everything except PHI nodes
84 // Select the PHI nodes
89 CurReg = MRegisterInfo::FirstVirtualRegister;
91 return false; // We never modify the LLVM itself.
94 /// visitBasicBlock - This method is called when we are visiting a new basic
95 /// block. This simply creates a new MachineBasicBlock to emit code into
96 /// and adds it to the current MachineFunction. Subsequent visit* for
97 /// instructions will be invoked for all instructions in the basic block.
99 void visitBasicBlock(BasicBlock &LLVM_BB) {
100 BB = MBBMap[&LLVM_BB];
104 /// SelectPHINodes - Insert machine code to generate phis. This is tricky
105 /// because we have to generate our sources into the source basic blocks,
106 /// not the current one.
108 void SelectPHINodes();
110 // Visitation methods for various instructions. These methods simply emit
111 // fixed X86 code for each instruction.
114 // Control flow operators
115 void visitReturnInst(ReturnInst &RI);
116 void visitBranchInst(BranchInst &BI);
117 void visitCallInst(CallInst &I);
119 // Arithmetic operators
120 void visitSimpleBinary(BinaryOperator &B, unsigned OpcodeClass);
121 void visitAdd(BinaryOperator &B) { visitSimpleBinary(B, 0); }
122 void visitSub(BinaryOperator &B) { visitSimpleBinary(B, 1); }
123 void doMultiply(unsigned destReg, const Type *resultType,
124 unsigned op0Reg, unsigned op1Reg,
125 MachineBasicBlock *MBB,
126 MachineBasicBlock::iterator &MBBI);
127 void visitMul(BinaryOperator &B);
129 void visitDiv(BinaryOperator &B) { visitDivRem(B); }
130 void visitRem(BinaryOperator &B) { visitDivRem(B); }
131 void visitDivRem(BinaryOperator &B);
134 void visitAnd(BinaryOperator &B) { visitSimpleBinary(B, 2); }
135 void visitOr (BinaryOperator &B) { visitSimpleBinary(B, 3); }
136 void visitXor(BinaryOperator &B) { visitSimpleBinary(B, 4); }
138 // Binary comparison operators
139 void visitSetCCInst(SetCondInst &I, unsigned OpNum);
140 void visitSetEQ(SetCondInst &I) { visitSetCCInst(I, 0); }
141 void visitSetNE(SetCondInst &I) { visitSetCCInst(I, 1); }
142 void visitSetLT(SetCondInst &I) { visitSetCCInst(I, 2); }
143 void visitSetGT(SetCondInst &I) { visitSetCCInst(I, 3); }
144 void visitSetLE(SetCondInst &I) { visitSetCCInst(I, 4); }
145 void visitSetGE(SetCondInst &I) { visitSetCCInst(I, 5); }
147 // Memory Instructions
148 void visitLoadInst(LoadInst &I);
149 void visitStoreInst(StoreInst &I);
150 void visitGetElementPtrInst(GetElementPtrInst &I);
151 void visitMallocInst(MallocInst &I);
152 void visitFreeInst(FreeInst &I);
153 void visitAllocaInst(AllocaInst &I);
156 void visitShiftInst(ShiftInst &I);
157 void visitPHINode(PHINode &I) {} // PHI nodes handled by second pass
158 void visitCastInst(CastInst &I);
160 void visitInstruction(Instruction &I) {
161 std::cerr << "Cannot instruction select: " << I;
165 /// promote32 - Make a value 32-bits wide, and put it somewhere.
166 void promote32 (const unsigned targetReg, Value *v);
168 // emitGEPOperation - Common code shared between visitGetElementPtrInst and
169 // constant expression GEP support.
171 void emitGEPOperation(MachineBasicBlock *BB, MachineBasicBlock::iterator&IP,
172 Value *Src, User::op_iterator IdxBegin,
173 User::op_iterator IdxEnd, unsigned TargetReg);
175 /// copyConstantToRegister - Output the instructions required to put the
176 /// specified constant into the specified register.
178 void copyConstantToRegister(Constant *C, unsigned Reg,
179 MachineBasicBlock *MBB,
180 MachineBasicBlock::iterator &MBBI);
182 /// makeAnotherReg - This method returns the next register number
183 /// we haven't yet used.
184 unsigned makeAnotherReg(const Type *Ty) {
185 // Add the mapping of regnumber => reg class to MachineFunction
186 F->addRegMap(CurReg, TM.getRegisterInfo()->getRegClassForType(Ty));
190 /// getReg - This method turns an LLVM value into a register number. This
191 /// is guaranteed to produce the same register number for a particular value
192 /// every time it is queried.
194 unsigned getReg(Value &V) { return getReg(&V); } // Allow references
195 unsigned getReg(Value *V) {
196 // Just append to the end of the current bb.
197 MachineBasicBlock::iterator It = BB->end();
198 return getReg(V, BB, It);
200 unsigned getReg(Value *V, MachineBasicBlock *MBB,
201 MachineBasicBlock::iterator &IPt) {
202 unsigned &Reg = RegMap[V];
204 Reg = makeAnotherReg(V->getType());
208 // If this operand is a constant, emit the code to copy the constant into
209 // the register here...
211 if (Constant *C = dyn_cast<Constant>(V)) {
212 copyConstantToRegister(C, Reg, MBB, IPt);
213 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
214 // Move the address of the global into the register
215 BMI(MBB, IPt, X86::MOVir32, 1, Reg).addReg(GV);
216 } else if (Argument *A = dyn_cast<Argument>(V)) {
217 // Find the position of the argument in the argument list.
218 const Function *f = F->getFunction ();
219 // The function's arguments look like this:
220 // [EBP] -- copy of old EBP
221 // [EBP + 4] -- return address
222 // [EBP + 8] -- first argument (leftmost lexically)
223 // So we want to start with counter = 2.
224 int counter = 2, argPos = -1;
225 for (Function::const_aiterator ai = f->abegin (), ae = f->aend ();
229 break; // Only need to find it once. ;-)
234 && "Argument not found in current function's argument list");
235 // Load it out of the stack frame at EBP + 4*argPos.
236 addRegOffset(BMI(MBB, IPt, X86::MOVmr32, 4, Reg), X86::EBP, 4*argPos);
244 /// TypeClass - Used by the X86 backend to group LLVM types by their basic X86
248 cByte, cShort, cInt, cLong, cFloat, cDouble
251 /// getClass - Turn a primitive type into a "class" number which is based on the
252 /// size of the type, and whether or not it is floating point.
254 static inline TypeClass getClass(const Type *Ty) {
255 switch (Ty->getPrimitiveID()) {
256 case Type::SByteTyID:
257 case Type::UByteTyID: return cByte; // Byte operands are class #0
258 case Type::ShortTyID:
259 case Type::UShortTyID: return cShort; // Short operands are class #1
262 case Type::PointerTyID: return cInt; // Int's and pointers are class #2
265 case Type::ULongTyID: //return cLong; // Longs are class #3
266 return cInt; // FIXME: LONGS ARE TREATED AS INTS!
268 case Type::FloatTyID: return cFloat; // Float is class #4
269 case Type::DoubleTyID: return cDouble; // Doubles are class #5
271 assert(0 && "Invalid type to getClass!");
272 return cByte; // not reached
276 // getClassB - Just like getClass, but treat boolean values as bytes.
277 static inline TypeClass getClassB(const Type *Ty) {
278 if (Ty == Type::BoolTy) return cByte;
283 /// copyConstantToRegister - Output the instructions required to put the
284 /// specified constant into the specified register.
286 void ISel::copyConstantToRegister(Constant *C, unsigned R,
287 MachineBasicBlock *MBB,
288 MachineBasicBlock::iterator &IP) {
289 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
290 if (CE->getOpcode() == Instruction::GetElementPtr) {
291 emitGEPOperation(BB, IP, CE->getOperand(0),
292 CE->op_begin()+1, CE->op_end(), R);
296 std::cerr << "Offending expr: " << C << "\n";
297 assert (0 && "Constant expressions not yet handled!\n");
300 if (C->getType()->isIntegral()) {
301 unsigned Class = getClassB(C->getType());
302 assert(Class != 3 && "Type not handled yet!");
304 static const unsigned IntegralOpcodeTab[] = {
305 X86::MOVir8, X86::MOVir16, X86::MOVir32
308 if (C->getType() == Type::BoolTy) {
309 BMI(MBB, IP, X86::MOVir8, 1, R).addZImm(C == ConstantBool::True);
310 } else if (C->getType()->isSigned()) {
311 ConstantSInt *CSI = cast<ConstantSInt>(C);
312 BMI(MBB, IP, IntegralOpcodeTab[Class], 1, R).addSImm(CSI->getValue());
314 ConstantUInt *CUI = cast<ConstantUInt>(C);
315 BMI(MBB, IP, IntegralOpcodeTab[Class], 1, R).addZImm(CUI->getValue());
317 } else if (isa<ConstantPointerNull>(C)) {
318 // Copy zero (null pointer) to the register.
319 BMI(MBB, IP, X86::MOVir32, 1, R).addZImm(0);
320 } else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(C)) {
321 unsigned SrcReg = getReg(CPR->getValue(), BB, IP);
322 BMI(MBB, IP, X86::MOVrr32, 1, R).addReg(SrcReg);
324 std::cerr << "Offending constant: " << C << "\n";
325 assert(0 && "Type not handled yet!");
329 /// SelectPHINodes - Insert machine code to generate phis. This is tricky
330 /// because we have to generate our sources into the source basic blocks, not
333 void ISel::SelectPHINodes() {
334 const Function &LF = *F->getFunction(); // The LLVM function...
335 for (Function::const_iterator I = LF.begin(), E = LF.end(); I != E; ++I) {
336 const BasicBlock *BB = I;
337 MachineBasicBlock *MBB = MBBMap[I];
339 // Loop over all of the PHI nodes in the LLVM basic block...
340 unsigned NumPHIs = 0;
341 for (BasicBlock::const_iterator I = BB->begin();
342 PHINode *PN = (PHINode*)dyn_cast<PHINode>(&*I); ++I) {
343 // Create a new machine instr PHI node, and insert it.
344 MachineInstr *MI = BuildMI(X86::PHI, PN->getNumOperands(), getReg(*PN));
345 MBB->insert(MBB->begin()+NumPHIs++, MI); // Insert it at the top of the BB
347 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
348 MachineBasicBlock *PredMBB = MBBMap[PN->getIncomingBlock(i)];
350 // Get the incoming value into a virtual register. If it is not already
351 // available in a virtual register, insert the computation code into
355 MachineBasicBlock::iterator PI = PredMBB->begin();
356 while ((*PI)->getOpcode() == X86::PHI) ++PI;
358 MI->addRegOperand(getReg(PN->getIncomingValue(i), PredMBB, PI));
359 MI->addMachineBasicBlockOperand(PredMBB);
367 /// SetCC instructions - Here we just emit boilerplate code to set a byte-sized
368 /// register, then move it to wherever the result should be.
369 /// We handle FP setcc instructions by pushing them, doing a
370 /// compare-and-pop-twice, and then copying the concodes to the main
371 /// processor's concodes (I didn't make this up, it's in the Intel manual)
373 void ISel::visitSetCCInst(SetCondInst &I, unsigned OpNum) {
374 // The arguments are already supposed to be of the same type.
375 const Type *CompTy = I.getOperand(0)->getType();
376 unsigned reg1 = getReg(I.getOperand(0));
377 unsigned reg2 = getReg(I.getOperand(1));
379 unsigned Class = getClass(CompTy);
381 // Emit: cmp <var1>, <var2> (do the comparison). We can
382 // compare 8-bit with 8-bit, 16-bit with 16-bit, 32-bit with
385 BuildMI (BB, X86::CMPrr8, 2).addReg (reg1).addReg (reg2);
388 BuildMI (BB, X86::CMPrr16, 2).addReg (reg1).addReg (reg2);
391 BuildMI (BB, X86::CMPrr32, 2).addReg (reg1).addReg (reg2);
394 // Push the variables on the stack with fldl opcodes.
395 // FIXME: assuming var1, var2 are in memory, if not, spill to
397 case cFloat: // Floats
398 BuildMI (BB, X86::FLDr32, 1).addReg (reg1);
399 BuildMI (BB, X86::FLDr32, 1).addReg (reg2);
401 case cDouble: // Doubles
402 BuildMI (BB, X86::FLDr64, 1).addReg (reg1);
403 BuildMI (BB, X86::FLDr64, 1).addReg (reg2);
410 if (CompTy->isFloatingPoint()) {
411 // (Non-trapping) compare and pop twice.
412 BuildMI (BB, X86::FUCOMPP, 0);
413 // Move fp status word (concodes) to ax.
414 BuildMI (BB, X86::FNSTSWr8, 1, X86::AX);
415 // Load real concodes from ax.
416 BuildMI (BB, X86::SAHF, 1).addReg(X86::AH);
419 // Emit setOp instruction (extract concode; clobbers ax),
420 // using the following mapping:
421 // LLVM -> X86 signed X86 unsigned
423 // seteq -> sete sete
424 // setne -> setne setne
425 // setlt -> setl setb
426 // setgt -> setg seta
427 // setle -> setle setbe
428 // setge -> setge setae
430 static const unsigned OpcodeTab[2][6] = {
431 {X86::SETEr, X86::SETNEr, X86::SETBr, X86::SETAr, X86::SETBEr, X86::SETAEr},
432 {X86::SETEr, X86::SETNEr, X86::SETLr, X86::SETGr, X86::SETLEr, X86::SETGEr},
435 BuildMI(BB, OpcodeTab[CompTy->isSigned()][OpNum], 0, X86::AL);
437 // Put it in the result using a move.
438 BuildMI (BB, X86::MOVrr8, 1, getReg(I)).addReg(X86::AL);
441 /// promote32 - Emit instructions to turn a narrow operand into a 32-bit-wide
442 /// operand, in the specified target register.
444 ISel::promote32 (unsigned targetReg, Value *v)
446 unsigned vReg = getReg (v);
447 unsigned Class = getClass (v->getType ());
448 bool isUnsigned = v->getType ()->isUnsigned ();
449 assert (((Class == cByte) || (Class == cShort) || (Class == cInt))
450 && "Unpromotable operand class in promote32");
454 // Extend value into target register (8->32)
456 BuildMI (BB, X86::MOVZXr32r8, 1, targetReg).addReg (vReg);
458 BuildMI (BB, X86::MOVSXr32r8, 1, targetReg).addReg (vReg);
461 // Extend value into target register (16->32)
463 BuildMI (BB, X86::MOVZXr32r16, 1, targetReg).addReg (vReg);
465 BuildMI (BB, X86::MOVSXr32r16, 1, targetReg).addReg (vReg);
468 // Move value into target register (32->32)
469 BuildMI (BB, X86::MOVrr32, 1, targetReg).addReg (vReg);
474 /// 'ret' instruction - Here we are interested in meeting the x86 ABI. As such,
475 /// we have the following possibilities:
477 /// ret void: No return value, simply emit a 'ret' instruction
478 /// ret sbyte, ubyte : Extend value into EAX and return
479 /// ret short, ushort: Extend value into EAX and return
480 /// ret int, uint : Move value into EAX and return
481 /// ret pointer : Move value into EAX and return
482 /// ret long, ulong : Move value into EAX/EDX and return
483 /// ret float/double : Top of FP stack
486 ISel::visitReturnInst (ReturnInst &I)
488 if (I.getNumOperands () == 0)
490 // Emit a 'ret' instruction
491 BuildMI (BB, X86::RET, 0);
494 Value *rv = I.getOperand (0);
495 unsigned Class = getClass (rv->getType ());
498 // integral return values: extend or move into EAX and return.
502 promote32 (X86::EAX, rv);
504 // ret float/double: top of FP stack
506 case cFloat: // Floats
507 BuildMI (BB, X86::FLDr32, 1).addReg (getReg (rv));
509 case cDouble: // Doubles
510 BuildMI (BB, X86::FLDr64, 1).addReg (getReg (rv));
513 // ret long: use EAX(least significant 32 bits)/EDX (most
514 // significant 32)...uh, I think so Brain, but how do i call
515 // up the two parts of the value from inside this mouse
518 visitInstruction (I);
520 // Emit a 'ret' instruction
521 BuildMI (BB, X86::RET, 0);
524 /// visitBranchInst - Handle conditional and unconditional branches here. Note
525 /// that since code layout is frozen at this point, that if we are trying to
526 /// jump to a block that is the immediate successor of the current block, we can
527 /// just make a fall-through. (but we don't currently).
530 ISel::visitBranchInst (BranchInst & BI)
532 if (BI.isConditional ())
534 BasicBlock *ifTrue = BI.getSuccessor (0);
535 BasicBlock *ifFalse = BI.getSuccessor (1); // this is really unobvious
537 // simplest thing I can think of: compare condition with zero,
538 // followed by jump-if-equal to ifFalse, and jump-if-nonequal to
540 unsigned int condReg = getReg (BI.getCondition ());
541 BuildMI (BB, X86::CMPri8, 2).addReg (condReg).addZImm (0);
542 BuildMI (BB, X86::JNE, 1).addPCDisp (BI.getSuccessor (0));
543 BuildMI (BB, X86::JE, 1).addPCDisp (BI.getSuccessor (1));
545 else // unconditional branch
547 BuildMI (BB, X86::JMP, 1).addPCDisp (BI.getSuccessor (0));
551 /// visitCallInst - Push args on stack and do a procedure call instruction.
553 ISel::visitCallInst (CallInst & CI)
555 // keep a counter of how many bytes we pushed on the stack
556 unsigned bytesPushed = 0;
558 // Push the arguments on the stack in reverse order, as specified by
560 for (unsigned i = CI.getNumOperands()-1; i >= 1; --i)
562 Value *v = CI.getOperand (i);
563 switch (getClass (v->getType ()))
567 // Promote V to 32 bits wide, and move the result into EAX,
569 promote32 (X86::EAX, v);
570 BuildMI (BB, X86::PUSHr32, 1).addReg (X86::EAX);
575 unsigned Reg = getReg(v);
576 BuildMI (BB, X86::PUSHr32, 1).addReg(Reg);
581 // FIXME: long/ulong/double args not handled.
582 visitInstruction (CI);
587 if (Function *F = CI.getCalledFunction()) {
588 // Emit a CALL instruction with PC-relative displacement.
589 BuildMI(BB, X86::CALLpcrel32, 1).addPCDisp(F);
591 unsigned Reg = getReg(CI.getCalledValue());
592 BuildMI(BB, X86::CALLr32, 1).addReg(Reg);
595 // Adjust the stack by `bytesPushed' amount if non-zero
597 BuildMI (BB, X86::ADDri32, 2).addReg(X86::ESP).addZImm(bytesPushed);
599 // If there is a return value, scavenge the result from the location the call
602 if (CI.getType() != Type::VoidTy) {
603 unsigned resultTypeClass = getClass (CI.getType ());
604 switch (resultTypeClass) {
608 // Integral results are in %eax, or the appropriate portion
610 static const unsigned regRegMove[] = {
611 X86::MOVrr8, X86::MOVrr16, X86::MOVrr32
613 static const unsigned AReg[] = { X86::AL, X86::AX, X86::EAX };
614 BuildMI (BB, regRegMove[resultTypeClass], 1,
615 getReg (CI)).addReg (AReg[resultTypeClass]);
619 // Floating-point return values live in %st(0) (i.e., the top of
620 // the FP stack.) The general way to approach this is to do a
621 // FSTP to save the top of the FP stack on the real stack, then
622 // do a MOV to load the top of the real stack into the target
624 visitInstruction (CI); // FIXME: add the right args for the calls below
625 // BuildMI (BB, X86::FSTPm32, 0);
626 // BuildMI (BB, X86::MOVmr32, 0);
629 std::cerr << "Cannot get return value for call of type '"
630 << *CI.getType() << "'\n";
631 visitInstruction(CI);
636 /// visitSimpleBinary - Implement simple binary operators for integral types...
637 /// OperatorClass is one of: 0 for Add, 1 for Sub, 2 for And, 3 for Or,
640 void ISel::visitSimpleBinary(BinaryOperator &B, unsigned OperatorClass) {
641 if (B.getType() == Type::BoolTy) // FIXME: Handle bools for logicals
644 unsigned Class = getClass(B.getType());
645 if (Class > 2) // FIXME: Handle longs
648 static const unsigned OpcodeTab[][4] = {
649 // Arithmetic operators
650 { X86::ADDrr8, X86::ADDrr16, X86::ADDrr32, 0 }, // ADD
651 { X86::SUBrr8, X86::SUBrr16, X86::SUBrr32, 0 }, // SUB
654 { X86::ANDrr8, X86::ANDrr16, X86::ANDrr32, 0 }, // AND
655 { X86:: ORrr8, X86:: ORrr16, X86:: ORrr32, 0 }, // OR
656 { X86::XORrr8, X86::XORrr16, X86::XORrr32, 0 }, // XOR
659 unsigned Opcode = OpcodeTab[OperatorClass][Class];
660 unsigned Op0r = getReg(B.getOperand(0));
661 unsigned Op1r = getReg(B.getOperand(1));
662 BuildMI(BB, Opcode, 2, getReg(B)).addReg(Op0r).addReg(Op1r);
665 /// doMultiply - Emit appropriate instructions to multiply together
666 /// the registers op0Reg and op1Reg, and put the result in destReg.
667 /// The type of the result should be given as resultType.
669 ISel::doMultiply(unsigned destReg, const Type *resultType,
670 unsigned op0Reg, unsigned op1Reg,
671 MachineBasicBlock *MBB, MachineBasicBlock::iterator &MBBI)
673 unsigned Class = getClass (resultType);
676 assert (Class <= 2 && "Someday, we will learn how to multiply"
677 "longs and floating-point numbers. This is not that day.");
679 static const unsigned Regs[] ={ X86::AL , X86::AX , X86::EAX };
680 static const unsigned MulOpcode[]={ X86::MULrr8, X86::MULrr16, X86::MULrr32 };
681 static const unsigned MovOpcode[]={ X86::MOVrr8, X86::MOVrr16, X86::MOVrr32 };
682 unsigned Reg = Regs[Class];
684 // Emit a MOV to put the first operand into the appropriately-sized
686 BMI(MBB, MBBI, MovOpcode[Class], 1, Reg).addReg (op0Reg);
688 // Emit the appropriate multiply instruction.
689 BMI(MBB, MBBI, MulOpcode[Class], 1).addReg (op1Reg);
691 // Emit another MOV to put the result into the destination register.
692 BMI(MBB, MBBI, MovOpcode[Class], 1, destReg).addReg (Reg);
695 /// visitMul - Multiplies are not simple binary operators because they must deal
696 /// with the EAX register explicitly.
698 void ISel::visitMul(BinaryOperator &I) {
699 unsigned DestReg = getReg(I);
700 unsigned Op0Reg = getReg(I.getOperand(0));
701 unsigned Op1Reg = getReg(I.getOperand(1));
702 MachineBasicBlock::iterator MBBI = BB->end();
703 doMultiply(DestReg, I.getType(), Op0Reg, Op1Reg, BB, MBBI);
707 /// visitDivRem - Handle division and remainder instructions... these
708 /// instruction both require the same instructions to be generated, they just
709 /// select the result from a different register. Note that both of these
710 /// instructions work differently for signed and unsigned operands.
712 void ISel::visitDivRem(BinaryOperator &I) {
713 unsigned Class = getClass(I.getType());
714 if (Class > 2) // FIXME: Handle longs
717 static const unsigned Regs[] ={ X86::AL , X86::AX , X86::EAX };
718 static const unsigned MovOpcode[]={ X86::MOVrr8, X86::MOVrr16, X86::MOVrr32 };
719 static const unsigned ExtOpcode[]={ X86::CBW , X86::CWD , X86::CDQ };
720 static const unsigned ClrOpcode[]={ X86::XORrr8, X86::XORrr16, X86::XORrr32 };
721 static const unsigned ExtRegs[] ={ X86::AH , X86::DX , X86::EDX };
723 static const unsigned DivOpcode[][4] = {
724 { X86::DIVrr8 , X86::DIVrr16 , X86::DIVrr32 , 0 }, // Unsigned division
725 { X86::IDIVrr8, X86::IDIVrr16, X86::IDIVrr32, 0 }, // Signed division
728 bool isSigned = I.getType()->isSigned();
729 unsigned Reg = Regs[Class];
730 unsigned ExtReg = ExtRegs[Class];
731 unsigned Op0Reg = getReg(I.getOperand(0));
732 unsigned Op1Reg = getReg(I.getOperand(1));
734 // Put the first operand into one of the A registers...
735 BuildMI(BB, MovOpcode[Class], 1, Reg).addReg(Op0Reg);
738 // Emit a sign extension instruction...
739 BuildMI(BB, ExtOpcode[Class], 0);
741 // If unsigned, emit a zeroing instruction... (reg = xor reg, reg)
742 BuildMI(BB, ClrOpcode[Class], 2, ExtReg).addReg(ExtReg).addReg(ExtReg);
745 // Emit the appropriate divide or remainder instruction...
746 BuildMI(BB, DivOpcode[isSigned][Class], 1).addReg(Op1Reg);
748 // Figure out which register we want to pick the result out of...
749 unsigned DestReg = (I.getOpcode() == Instruction::Div) ? Reg : ExtReg;
751 // Put the result into the destination register...
752 BuildMI(BB, MovOpcode[Class], 1, getReg(I)).addReg(DestReg);
756 /// Shift instructions: 'shl', 'sar', 'shr' - Some special cases here
757 /// for constant immediate shift values, and for constant immediate
758 /// shift values equal to 1. Even the general case is sort of special,
759 /// because the shift amount has to be in CL, not just any old register.
761 void ISel::visitShiftInst (ShiftInst &I) {
762 unsigned Op0r = getReg (I.getOperand(0));
763 unsigned DestReg = getReg(I);
764 bool isLeftShift = I.getOpcode() == Instruction::Shl;
765 bool isOperandSigned = I.getType()->isUnsigned();
766 unsigned OperandClass = getClass(I.getType());
768 if (OperandClass > 2)
769 visitInstruction(I); // Can't handle longs yet!
771 if (ConstantUInt *CUI = dyn_cast <ConstantUInt> (I.getOperand (1)))
773 // The shift amount is constant, guaranteed to be a ubyte. Get its value.
774 assert(CUI->getType() == Type::UByteTy && "Shift amount not a ubyte?");
775 unsigned char shAmt = CUI->getValue();
777 static const unsigned ConstantOperand[][4] = {
778 { X86::SHRir8, X86::SHRir16, X86::SHRir32, 0 }, // SHR
779 { X86::SARir8, X86::SARir16, X86::SARir32, 0 }, // SAR
780 { X86::SHLir8, X86::SHLir16, X86::SHLir32, 0 }, // SHL
781 { X86::SHLir8, X86::SHLir16, X86::SHLir32, 0 }, // SAL = SHL
784 const unsigned *OpTab = // Figure out the operand table to use
785 ConstantOperand[isLeftShift*2+isOperandSigned];
787 // Emit: <insn> reg, shamt (shift-by-immediate opcode "ir" form.)
788 BuildMI(BB, OpTab[OperandClass], 2, DestReg).addReg(Op0r).addZImm(shAmt);
792 // The shift amount is non-constant.
794 // In fact, you can only shift with a variable shift amount if
795 // that amount is already in the CL register, so we have to put it
799 // Emit: move cl, shiftAmount (put the shift amount in CL.)
800 BuildMI(BB, X86::MOVrr8, 1, X86::CL).addReg(getReg(I.getOperand(1)));
802 // This is a shift right (SHR).
803 static const unsigned NonConstantOperand[][4] = {
804 { X86::SHRrr8, X86::SHRrr16, X86::SHRrr32, 0 }, // SHR
805 { X86::SARrr8, X86::SARrr16, X86::SARrr32, 0 }, // SAR
806 { X86::SHLrr8, X86::SHLrr16, X86::SHLrr32, 0 }, // SHL
807 { X86::SHLrr8, X86::SHLrr16, X86::SHLrr32, 0 }, // SAL = SHL
810 const unsigned *OpTab = // Figure out the operand table to use
811 NonConstantOperand[isLeftShift*2+isOperandSigned];
813 BuildMI(BB, OpTab[OperandClass], 1, DestReg).addReg(Op0r);
818 /// visitLoadInst - Implement LLVM load instructions in terms of the x86 'mov'
821 void ISel::visitLoadInst(LoadInst &I) {
822 unsigned Class = getClass(I.getType());
823 if (Class > 2) // FIXME: Handle longs and others...
826 static const unsigned Opcode[] = { X86::MOVmr8, X86::MOVmr16, X86::MOVmr32 };
828 unsigned AddressReg = getReg(I.getOperand(0));
829 addDirectMem(BuildMI(BB, Opcode[Class], 4, getReg(I)), AddressReg);
833 /// visitStoreInst - Implement LLVM store instructions in terms of the x86 'mov'
836 void ISel::visitStoreInst(StoreInst &I) {
837 unsigned Class = getClass(I.getOperand(0)->getType());
838 if (Class > 2) // FIXME: Handle longs and others...
841 static const unsigned Opcode[] = { X86::MOVrm8, X86::MOVrm16, X86::MOVrm32 };
843 unsigned ValReg = getReg(I.getOperand(0));
844 unsigned AddressReg = getReg(I.getOperand(1));
845 addDirectMem(BuildMI(BB, Opcode[Class], 1+4), AddressReg).addReg(ValReg);
849 /// visitCastInst - Here we have various kinds of copying with or without
850 /// sign extension going on.
852 ISel::visitCastInst (CastInst &CI)
854 const Type *targetType = CI.getType ();
855 Value *operand = CI.getOperand (0);
856 unsigned int operandReg = getReg (operand);
857 const Type *sourceType = operand->getType ();
858 unsigned int destReg = getReg (CI);
860 // Currently we handle:
864 // 2) cast {sbyte, ubyte} to {sbyte, ubyte}
865 // cast {short, ushort} to {ushort, short}
866 // cast {int, uint, ptr} to {int, uint, ptr}
868 // 3) cast {sbyte, ubyte} to {ushort, short}
869 // cast {sbyte, ubyte} to {int, uint, ptr}
870 // cast {short, ushort} to {int, uint, ptr}
872 // 4) cast {int, uint, ptr} to {short, ushort}
873 // cast {int, uint, ptr} to {sbyte, ubyte}
874 // cast {short, ushort} to {sbyte, ubyte}
876 // 1) Implement casts to bool by using compare on the operand followed
877 // by set if not zero on the result.
878 if (targetType == Type::BoolTy)
880 BuildMI (BB, X86::CMPri8, 2).addReg (operandReg).addZImm (0);
881 BuildMI (BB, X86::SETNEr, 1, destReg);
885 // 2) Implement casts between values of the same type class (as determined
886 // by getClass) by using a register-to-register move.
887 unsigned srcClass = getClassB(sourceType);
888 unsigned targClass = getClass (targetType);
889 static const unsigned regRegMove[] = {
890 X86::MOVrr8, X86::MOVrr16, X86::MOVrr32
892 if ((srcClass < 3) && (targClass < 3) && (srcClass == targClass))
894 BuildMI (BB, regRegMove[srcClass], 1, destReg).addReg (operandReg);
897 // 3) Handle cast of SMALLER int to LARGER int using a move with sign
898 // extension or zero extension, depending on whether the source type
900 if ((srcClass < 3) && (targClass < 3) && (srcClass < targClass))
902 static const unsigned ops[] = {
903 X86::MOVSXr16r8, X86::MOVSXr32r8, X86::MOVSXr32r16,
904 X86::MOVZXr16r8, X86::MOVZXr32r8, X86::MOVZXr32r16
906 unsigned srcSigned = sourceType->isSigned ();
907 BuildMI (BB, ops[3 * srcSigned + srcClass + targClass - 1], 1,
908 destReg).addReg (operandReg);
911 // 4) Handle cast of LARGER int to SMALLER int using a move to EAX
912 // followed by a move out of AX or AL.
913 if ((srcClass < 3) && (targClass < 3) && (srcClass > targClass))
915 static const unsigned AReg[] = { X86::AL, X86::AX, X86::EAX };
916 BuildMI (BB, regRegMove[srcClass], 1,
917 AReg[srcClass]).addReg (operandReg);
918 BuildMI (BB, regRegMove[targClass], 1, destReg).addReg (AReg[srcClass]);
921 // Anything we haven't handled already, we can't (yet) handle at all.
923 // FP to integral casts can be handled with FISTP to store onto the
924 // stack while converting to integer, followed by a MOV to load from
925 // the stack into the result register. Integral to FP casts can be
926 // handled with MOV to store onto the stack, followed by a FILD to
927 // load from the stack while converting to FP. For the moment, I
928 // can't quite get straight in my head how to borrow myself some
929 // stack space and write on it. Otherwise, this would be trivial.
930 visitInstruction (CI);
933 /// visitGetElementPtrInst - I don't know, most programs don't have
934 /// getelementptr instructions, right? That means we can put off
935 /// implementing this, right? Right. This method emits machine
936 /// instructions to perform type-safe pointer arithmetic. I am
937 /// guessing this could be cleaned up somewhat to use fewer temporary
940 ISel::visitGetElementPtrInst (GetElementPtrInst &I)
942 MachineBasicBlock::iterator MI = BB->end();
943 emitGEPOperation(BB, MI, I.getOperand(0),
944 I.op_begin()+1, I.op_end(), getReg(I));
947 void ISel::emitGEPOperation(MachineBasicBlock *MBB,
948 MachineBasicBlock::iterator &IP,
949 Value *Src, User::op_iterator IdxBegin,
950 User::op_iterator IdxEnd, unsigned TargetReg) {
951 const TargetData &TD = TM.getTargetData();
952 const Type *Ty = Src->getType();
953 unsigned basePtrReg = getReg(Src, BB, IP);
955 // GEPs have zero or more indices; we must perform a struct access
956 // or array access for each one.
957 for (GetElementPtrInst::op_iterator oi = IdxBegin,
958 oe = IdxEnd; oi != oe; ++oi) {
960 unsigned nextBasePtrReg = makeAnotherReg(Type::UIntTy);
961 if (const StructType *StTy = dyn_cast <StructType> (Ty)) {
962 // It's a struct access. idx is the index into the structure,
963 // which names the field. This index must have ubyte type.
964 const ConstantUInt *CUI = cast <ConstantUInt> (idx);
965 assert (CUI->getType () == Type::UByteTy
966 && "Funny-looking structure index in GEP");
967 // Use the TargetData structure to pick out what the layout of
968 // the structure is in memory. Since the structure index must
969 // be constant, we can get its value and use it to find the
970 // right byte offset from the StructLayout class's list of
971 // structure member offsets.
972 unsigned idxValue = CUI->getValue ();
973 unsigned memberOffset =
974 TD.getStructLayout (StTy)->MemberOffsets[idxValue];
975 // Emit an ADD to add memberOffset to the basePtr.
976 BMI(MBB, IP, X86::ADDri32, 2,
977 nextBasePtrReg).addReg (basePtrReg).addZImm (memberOffset);
978 // The next type is the member of the structure selected by the
980 Ty = StTy->getElementTypes ()[idxValue];
981 } else if (const SequentialType *SqTy = cast <SequentialType> (Ty)) {
982 // It's an array or pointer access: [ArraySize x ElementType].
983 const Type *typeOfSequentialTypeIndex = SqTy->getIndexType ();
984 // idx is the index into the array. Unlike with structure
985 // indices, we may not know its actual value at code-generation
987 assert (idx->getType () == typeOfSequentialTypeIndex
988 && "Funny-looking array index in GEP");
989 // We want to add basePtrReg to (idxReg * sizeof
990 // ElementType). First, we must find the size of the pointed-to
991 // type. (Not coincidentally, the next type is the type of the
992 // elements in the array.)
993 Ty = SqTy->getElementType ();
994 unsigned elementSize = TD.getTypeSize (Ty);
995 unsigned elementSizeReg = makeAnotherReg(typeOfSequentialTypeIndex);
996 copyConstantToRegister(ConstantSInt::get(typeOfSequentialTypeIndex,
997 elementSize), elementSizeReg,
1000 unsigned idxReg = getReg(idx, BB, IP);
1001 // Emit a MUL to multiply the register holding the index by
1002 // elementSize, putting the result in memberOffsetReg.
1003 unsigned memberOffsetReg = makeAnotherReg(Type::UIntTy);
1004 doMultiply (memberOffsetReg, typeOfSequentialTypeIndex,
1005 elementSizeReg, idxReg, BB, IP);
1006 // Emit an ADD to add memberOffsetReg to the basePtr.
1007 BMI(MBB, IP, X86::ADDrr32, 2,
1008 nextBasePtrReg).addReg (basePtrReg).addReg (memberOffsetReg);
1010 // Now that we are here, further indices refer to subtypes of this
1011 // one, so we don't need to worry about basePtrReg itself, anymore.
1012 basePtrReg = nextBasePtrReg;
1014 // After we have processed all the indices, the result is left in
1015 // basePtrReg. Move it to the register where we were expected to
1016 // put the answer. A 32-bit move should do it, because we are in
1018 BMI(MBB, IP, X86::MOVrr32, 1, TargetReg).addReg (basePtrReg);
1022 /// visitMallocInst - I know that personally, whenever I want to remember
1023 /// something, I have to clear off some space in my brain.
1025 ISel::visitMallocInst (MallocInst &I)
1027 // We assume that by this point, malloc instructions have been
1028 // lowered to calls, and dlsym will magically find malloc for us.
1029 // So we do not want to see malloc instructions here.
1030 visitInstruction (I);
1034 /// visitFreeInst - same story as MallocInst
1036 ISel::visitFreeInst (FreeInst &I)
1038 // We assume that by this point, free instructions have been
1039 // lowered to calls, and dlsym will magically find free for us.
1040 // So we do not want to see free instructions here.
1041 visitInstruction (I);
1045 /// visitAllocaInst - I want some stack space. Come on, man, I said I
1046 /// want some freakin' stack space.
1048 ISel::visitAllocaInst (AllocaInst &I)
1050 // Find the data size of the alloca inst's getAllocatedType.
1051 const Type *allocatedType = I.getAllocatedType ();
1052 const TargetData &TD = TM.DataLayout;
1053 unsigned allocatedTypeSize = TD.getTypeSize (allocatedType);
1054 // Keep stack 32-bit aligned.
1055 unsigned int allocatedTypeWords = allocatedTypeSize / 4;
1056 if (allocatedTypeSize % 4 != 0) { allocatedTypeWords++; }
1057 // Subtract size from stack pointer, thereby allocating some space.
1058 BuildMI (BB, X86::SUBri32, 1, X86::ESP).addZImm (allocatedTypeWords * 4);
1059 // Put a pointer to the space into the result register, by copying
1060 // the stack pointer.
1061 BuildMI (BB, X86::MOVrr32, 1, getReg (I)).addReg (X86::ESP);
1065 /// createSimpleX86InstructionSelector - This pass converts an LLVM function
1066 /// into a machine code representation is a very simple peep-hole fashion. The
1067 /// generated code sucks but the implementation is nice and simple.
1069 Pass *createSimpleX86InstructionSelector(TargetMachine &TM) {
1070 return new ISel(TM);