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llvm-mirror/lib/CodeGen/SelectionDAG/FastISel.cpp
Dan Gohman 4049434a04 Fast ISel trivially coalesces away no-op casts, so check for this when 
setting kill flags.

llvm-svn: 103832
2010-05-14 22:53:18 +00:00

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//===-- FastISel.cpp - Implementation of the FastISel class ---------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the implementation of the FastISel class.
//
// "Fast" instruction selection is designed to emit very poor code quickly.
// Also, it is not designed to be able to do much lowering, so most illegal
// types (e.g. i64 on 32-bit targets) and operations are not supported. It is
// also not intended to be able to do much optimization, except in a few cases
// where doing optimizations reduces overall compile time. For example, folding
// constants into immediate fields is often done, because it's cheap and it
// reduces the number of instructions later phases have to examine.
//
// "Fast" instruction selection is able to fail gracefully and transfer
// control to the SelectionDAG selector for operations that it doesn't
// support. In many cases, this allows us to avoid duplicating a lot of
// the complicated lowering logic that SelectionDAG currently has.
//
// The intended use for "fast" instruction selection is "-O0" mode
// compilation, where the quality of the generated code is irrelevant when
// weighed against the speed at which the code can be generated. Also,
// at -O0, the LLVM optimizers are not running, and this makes the
// compile time of codegen a much higher portion of the overall compile
// time. Despite its limitations, "fast" instruction selection is able to
// handle enough code on its own to provide noticeable overall speedups
// in -O0 compiles.
//
// Basic operations are supported in a target-independent way, by reading
// the same instruction descriptions that the SelectionDAG selector reads,
// and identifying simple arithmetic operations that can be directly selected
// from simple operators. More complicated operations currently require
// target-specific code.
//
//===----------------------------------------------------------------------===//
#include "llvm/Function.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/CodeGen/FastISel.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Analysis/DebugInfo.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/ErrorHandling.h"
#include "FunctionLoweringInfo.h"
using namespace llvm;
bool FastISel::hasTrivialKill(const Value *V) const {
// Don't consider constants or arguments to have trivial kills.
const Instruction *I = dyn_cast<Instruction>(V);
if (!I)
return false;
// No-op casts are trivially coalesced by fast-isel.
if (const CastInst *Cast = dyn_cast<CastInst>(I))
if (Cast->isNoopCast(TD.getIntPtrType(Cast->getContext())) &&
!hasTrivialKill(Cast->getOperand(0)))
return false;
// Only instructions with a single use in the same basic block are considered
// to have trivial kills.
return I->hasOneUse() &&
!(I->getOpcode() == Instruction::BitCast ||
I->getOpcode() == Instruction::PtrToInt ||
I->getOpcode() == Instruction::IntToPtr) &&
cast<Instruction>(I->use_begin())->getParent() == I->getParent();
}
unsigned FastISel::getRegForValue(const Value *V) {
EVT RealVT = TLI.getValueType(V->getType(), /*AllowUnknown=*/true);
// Don't handle non-simple values in FastISel.
if (!RealVT.isSimple())
return 0;
// Ignore illegal types. We must do this before looking up the value
// in ValueMap because Arguments are given virtual registers regardless
// of whether FastISel can handle them.
MVT VT = RealVT.getSimpleVT();
if (!TLI.isTypeLegal(VT)) {
// Promote MVT::i1 to a legal type though, because it's common and easy.
if (VT == MVT::i1)
VT = TLI.getTypeToTransformTo(V->getContext(), VT).getSimpleVT();
else
return 0;
}
// Look up the value to see if we already have a register for it. We
// cache values defined by Instructions across blocks, and other values
// only locally. This is because Instructions already have the SSA
// def-dominates-use requirement enforced.
if (ValueMap.count(V))
return ValueMap[V];
unsigned Reg = LocalValueMap[V];
if (Reg != 0)
return Reg;
// In bottom-up mode, just create the virtual register which will be used
// to hold the value. It will be materialized later.
if (IsBottomUp) {
Reg = createResultReg(TLI.getRegClassFor(VT));
if (isa<Instruction>(V))
ValueMap[V] = Reg;
else
LocalValueMap[V] = Reg;
return Reg;
}
return materializeRegForValue(V, VT);
}
/// materializeRegForValue - Helper for getRegForVale. This function is
/// called when the value isn't already available in a register and must
/// be materialized with new instructions.
unsigned FastISel::materializeRegForValue(const Value *V, MVT VT) {
unsigned Reg = 0;
if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
if (CI->getValue().getActiveBits() <= 64)
Reg = FastEmit_i(VT, VT, ISD::Constant, CI->getZExtValue());
} else if (isa<AllocaInst>(V)) {
Reg = TargetMaterializeAlloca(cast<AllocaInst>(V));
} else if (isa<ConstantPointerNull>(V)) {
// Translate this as an integer zero so that it can be
// local-CSE'd with actual integer zeros.
Reg =
getRegForValue(Constant::getNullValue(TD.getIntPtrType(V->getContext())));
} else if (const ConstantFP *CF = dyn_cast<ConstantFP>(V)) {
// Try to emit the constant directly.
Reg = FastEmit_f(VT, VT, ISD::ConstantFP, CF);
if (!Reg) {
// Try to emit the constant by using an integer constant with a cast.
const APFloat &Flt = CF->getValueAPF();
EVT IntVT = TLI.getPointerTy();
uint64_t x[2];
uint32_t IntBitWidth = IntVT.getSizeInBits();
bool isExact;
(void) Flt.convertToInteger(x, IntBitWidth, /*isSigned=*/true,
APFloat::rmTowardZero, &isExact);
if (isExact) {
APInt IntVal(IntBitWidth, 2, x);
unsigned IntegerReg =
getRegForValue(ConstantInt::get(V->getContext(), IntVal));
if (IntegerReg != 0)
Reg = FastEmit_r(IntVT.getSimpleVT(), VT, ISD::SINT_TO_FP,
IntegerReg, /*Kill=*/false);
}
}
} else if (const Operator *Op = dyn_cast<Operator>(V)) {
if (!SelectOperator(Op, Op->getOpcode())) return 0;
Reg = LocalValueMap[Op];
} else if (isa<UndefValue>(V)) {
Reg = createResultReg(TLI.getRegClassFor(VT));
BuildMI(MBB, DL, TII.get(TargetOpcode::IMPLICIT_DEF), Reg);
}
// If target-independent code couldn't handle the value, give target-specific
// code a try.
if (!Reg && isa<Constant>(V))
Reg = TargetMaterializeConstant(cast<Constant>(V));
// Don't cache constant materializations in the general ValueMap.
// To do so would require tracking what uses they dominate.
if (Reg != 0)
LocalValueMap[V] = Reg;
return Reg;
}
unsigned FastISel::lookUpRegForValue(const Value *V) {
// Look up the value to see if we already have a register for it. We
// cache values defined by Instructions across blocks, and other values
// only locally. This is because Instructions already have the SSA
// def-dominates-use requirement enforced.
if (ValueMap.count(V))
return ValueMap[V];
return LocalValueMap[V];
}
/// UpdateValueMap - Update the value map to include the new mapping for this
/// instruction, or insert an extra copy to get the result in a previous
/// determined register.
/// NOTE: This is only necessary because we might select a block that uses
/// a value before we select the block that defines the value. It might be
/// possible to fix this by selecting blocks in reverse postorder.
unsigned FastISel::UpdateValueMap(const Value *I, unsigned Reg) {
if (!isa<Instruction>(I)) {
LocalValueMap[I] = Reg;
return Reg;
}
unsigned &AssignedReg = ValueMap[I];
if (AssignedReg == 0)
AssignedReg = Reg;
else if (Reg != AssignedReg) {
const TargetRegisterClass *RegClass = MRI.getRegClass(Reg);
TII.copyRegToReg(*MBB, MBB->end(), AssignedReg,
Reg, RegClass, RegClass, DL);
}
return AssignedReg;
}
std::pair<unsigned, bool> FastISel::getRegForGEPIndex(const Value *Idx) {
unsigned IdxN = getRegForValue(Idx);
if (IdxN == 0)
// Unhandled operand. Halt "fast" selection and bail.
return std::pair<unsigned, bool>(0, false);
bool IdxNIsKill = hasTrivialKill(Idx);
// If the index is smaller or larger than intptr_t, truncate or extend it.
MVT PtrVT = TLI.getPointerTy();
EVT IdxVT = EVT::getEVT(Idx->getType(), /*HandleUnknown=*/false);
if (IdxVT.bitsLT(PtrVT)) {
IdxN = FastEmit_r(IdxVT.getSimpleVT(), PtrVT, ISD::SIGN_EXTEND,
IdxN, IdxNIsKill);
IdxNIsKill = true;
}
else if (IdxVT.bitsGT(PtrVT)) {
IdxN = FastEmit_r(IdxVT.getSimpleVT(), PtrVT, ISD::TRUNCATE,
IdxN, IdxNIsKill);
IdxNIsKill = true;
}
return std::pair<unsigned, bool>(IdxN, IdxNIsKill);
}
/// SelectBinaryOp - Select and emit code for a binary operator instruction,
/// which has an opcode which directly corresponds to the given ISD opcode.
///
bool FastISel::SelectBinaryOp(const User *I, unsigned ISDOpcode) {
EVT VT = EVT::getEVT(I->getType(), /*HandleUnknown=*/true);
if (VT == MVT::Other || !VT.isSimple())
// Unhandled type. Halt "fast" selection and bail.
return false;
// We only handle legal types. For example, on x86-32 the instruction
// selector contains all of the 64-bit instructions from x86-64,
// under the assumption that i64 won't be used if the target doesn't
// support it.
if (!TLI.isTypeLegal(VT)) {
// MVT::i1 is special. Allow AND, OR, or XOR because they
// don't require additional zeroing, which makes them easy.
if (VT == MVT::i1 &&
(ISDOpcode == ISD::AND || ISDOpcode == ISD::OR ||
ISDOpcode == ISD::XOR))
VT = TLI.getTypeToTransformTo(I->getContext(), VT);
else
return false;
}
unsigned Op0 = getRegForValue(I->getOperand(0));
if (Op0 == 0)
// Unhandled operand. Halt "fast" selection and bail.
return false;
bool Op0IsKill = hasTrivialKill(I->getOperand(0));
// Check if the second operand is a constant and handle it appropriately.
if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
unsigned ResultReg = FastEmit_ri(VT.getSimpleVT(), VT.getSimpleVT(),
ISDOpcode, Op0, Op0IsKill,
CI->getZExtValue());
if (ResultReg != 0) {
// We successfully emitted code for the given LLVM Instruction.
UpdateValueMap(I, ResultReg);
return true;
}
}
// Check if the second operand is a constant float.
if (ConstantFP *CF = dyn_cast<ConstantFP>(I->getOperand(1))) {
unsigned ResultReg = FastEmit_rf(VT.getSimpleVT(), VT.getSimpleVT(),
ISDOpcode, Op0, Op0IsKill, CF);
if (ResultReg != 0) {
// We successfully emitted code for the given LLVM Instruction.
UpdateValueMap(I, ResultReg);
return true;
}
}
unsigned Op1 = getRegForValue(I->getOperand(1));
if (Op1 == 0)
// Unhandled operand. Halt "fast" selection and bail.
return false;
bool Op1IsKill = hasTrivialKill(I->getOperand(1));
// Now we have both operands in registers. Emit the instruction.
unsigned ResultReg = FastEmit_rr(VT.getSimpleVT(), VT.getSimpleVT(),
ISDOpcode,
Op0, Op0IsKill,
Op1, Op1IsKill);
if (ResultReg == 0)
// Target-specific code wasn't able to find a machine opcode for
// the given ISD opcode and type. Halt "fast" selection and bail.
return false;
// We successfully emitted code for the given LLVM Instruction.
UpdateValueMap(I, ResultReg);
return true;
}
bool FastISel::SelectGetElementPtr(const User *I) {
unsigned N = getRegForValue(I->getOperand(0));
if (N == 0)
// Unhandled operand. Halt "fast" selection and bail.
return false;
bool NIsKill = hasTrivialKill(I->getOperand(0));
const Type *Ty = I->getOperand(0)->getType();
MVT VT = TLI.getPointerTy();
for (GetElementPtrInst::const_op_iterator OI = I->op_begin()+1,
E = I->op_end(); OI != E; ++OI) {
const Value *Idx = *OI;
if (const StructType *StTy = dyn_cast<StructType>(Ty)) {
unsigned Field = cast<ConstantInt>(Idx)->getZExtValue();
if (Field) {
// N = N + Offset
uint64_t Offs = TD.getStructLayout(StTy)->getElementOffset(Field);
// FIXME: This can be optimized by combining the add with a
// subsequent one.
N = FastEmit_ri_(VT, ISD::ADD, N, NIsKill, Offs, VT);
if (N == 0)
// Unhandled operand. Halt "fast" selection and bail.
return false;
NIsKill = true;
}
Ty = StTy->getElementType(Field);
} else {
Ty = cast<SequentialType>(Ty)->getElementType();
// If this is a constant subscript, handle it quickly.
if (const ConstantInt *CI = dyn_cast<ConstantInt>(Idx)) {
if (CI->getZExtValue() == 0) continue;
uint64_t Offs =
TD.getTypeAllocSize(Ty)*cast<ConstantInt>(CI)->getSExtValue();
N = FastEmit_ri_(VT, ISD::ADD, N, NIsKill, Offs, VT);
if (N == 0)
// Unhandled operand. Halt "fast" selection and bail.
return false;
NIsKill = true;
continue;
}
// N = N + Idx * ElementSize;
uint64_t ElementSize = TD.getTypeAllocSize(Ty);
std::pair<unsigned, bool> Pair = getRegForGEPIndex(Idx);
unsigned IdxN = Pair.first;
bool IdxNIsKill = Pair.second;
if (IdxN == 0)
// Unhandled operand. Halt "fast" selection and bail.
return false;
if (ElementSize != 1) {
IdxN = FastEmit_ri_(VT, ISD::MUL, IdxN, IdxNIsKill, ElementSize, VT);
if (IdxN == 0)
// Unhandled operand. Halt "fast" selection and bail.
return false;
IdxNIsKill = true;
}
N = FastEmit_rr(VT, VT, ISD::ADD, N, NIsKill, IdxN, IdxNIsKill);
if (N == 0)
// Unhandled operand. Halt "fast" selection and bail.
return false;
}
}
// We successfully emitted code for the given LLVM Instruction.
UpdateValueMap(I, N);
return true;
}
bool FastISel::SelectCall(const User *I) {
const Function *F = cast<CallInst>(I)->getCalledFunction();
if (!F) return false;
// Handle selected intrinsic function calls.
unsigned IID = F->getIntrinsicID();
switch (IID) {
default: break;
case Intrinsic::dbg_declare: {
const DbgDeclareInst *DI = cast<DbgDeclareInst>(I);
if (!DIVariable(DI->getVariable()).Verify() ||
!MF.getMMI().hasDebugInfo())
return true;
const Value *Address = DI->getAddress();
if (!Address)
return true;
if (isa<UndefValue>(Address))
return true;
const AllocaInst *AI = dyn_cast<AllocaInst>(Address);
// Don't handle byval struct arguments or VLAs, for example.
// Note that if we have a byval struct argument, fast ISel is turned off;
// those are handled in SelectionDAGBuilder.
if (AI) {
DenseMap<const AllocaInst*, int>::iterator SI =
StaticAllocaMap.find(AI);
if (SI == StaticAllocaMap.end()) break; // VLAs.
int FI = SI->second;
if (!DI->getDebugLoc().isUnknown())
MF.getMMI().setVariableDbgInfo(DI->getVariable(), FI, DI->getDebugLoc());
} else
// Building the map above is target independent. Generating DBG_VALUE
// inline is target dependent; do this now.
(void)TargetSelectInstruction(cast<Instruction>(I));
return true;
}
case Intrinsic::dbg_value: {
// This form of DBG_VALUE is target-independent.
const DbgValueInst *DI = cast<DbgValueInst>(I);
const TargetInstrDesc &II = TII.get(TargetOpcode::DBG_VALUE);
const Value *V = DI->getValue();
if (!V) {
// Currently the optimizer can produce this; insert an undef to
// help debugging. Probably the optimizer should not do this.
BuildMI(MBB, DL, II).addReg(0U).addImm(DI->getOffset()).
addMetadata(DI->getVariable());
} else if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
BuildMI(MBB, DL, II).addImm(CI->getZExtValue()).addImm(DI->getOffset()).
addMetadata(DI->getVariable());
} else if (const ConstantFP *CF = dyn_cast<ConstantFP>(V)) {
BuildMI(MBB, DL, II).addFPImm(CF).addImm(DI->getOffset()).
addMetadata(DI->getVariable());
} else if (unsigned Reg = lookUpRegForValue(V)) {
BuildMI(MBB, DL, II).addReg(Reg, RegState::Debug).addImm(DI->getOffset()).
addMetadata(DI->getVariable());
} else {
// We can't yet handle anything else here because it would require
// generating code, thus altering codegen because of debug info.
// Insert an undef so we can see what we dropped.
BuildMI(MBB, DL, II).addReg(0U).addImm(DI->getOffset()).
addMetadata(DI->getVariable());
}
return true;
}
case Intrinsic::eh_exception: {
EVT VT = TLI.getValueType(I->getType());
switch (TLI.getOperationAction(ISD::EXCEPTIONADDR, VT)) {
default: break;
case TargetLowering::Expand: {
assert(MBB->isLandingPad() && "Call to eh.exception not in landing pad!");
unsigned Reg = TLI.getExceptionAddressRegister();
const TargetRegisterClass *RC = TLI.getRegClassFor(VT);
unsigned ResultReg = createResultReg(RC);
bool InsertedCopy = TII.copyRegToReg(*MBB, MBB->end(), ResultReg,
Reg, RC, RC, DL);
assert(InsertedCopy && "Can't copy address registers!");
InsertedCopy = InsertedCopy;
UpdateValueMap(I, ResultReg);
return true;
}
}
break;
}
case Intrinsic::eh_selector: {
EVT VT = TLI.getValueType(I->getType());
switch (TLI.getOperationAction(ISD::EHSELECTION, VT)) {
default: break;
case TargetLowering::Expand: {
if (MBB->isLandingPad())
AddCatchInfo(*cast<CallInst>(I), &MF.getMMI(), MBB);
else {
#ifndef NDEBUG
CatchInfoLost.insert(cast<CallInst>(I));
#endif
// FIXME: Mark exception selector register as live in. Hack for PR1508.
unsigned Reg = TLI.getExceptionSelectorRegister();
if (Reg) MBB->addLiveIn(Reg);
}
unsigned Reg = TLI.getExceptionSelectorRegister();
EVT SrcVT = TLI.getPointerTy();
const TargetRegisterClass *RC = TLI.getRegClassFor(SrcVT);
unsigned ResultReg = createResultReg(RC);
bool InsertedCopy = TII.copyRegToReg(*MBB, MBB->end(), ResultReg, Reg,
RC, RC, DL);
assert(InsertedCopy && "Can't copy address registers!");
InsertedCopy = InsertedCopy;
bool ResultRegIsKill = hasTrivialKill(I);
// Cast the register to the type of the selector.
if (SrcVT.bitsGT(MVT::i32))
ResultReg = FastEmit_r(SrcVT.getSimpleVT(), MVT::i32, ISD::TRUNCATE,
ResultReg, ResultRegIsKill);
else if (SrcVT.bitsLT(MVT::i32))
ResultReg = FastEmit_r(SrcVT.getSimpleVT(), MVT::i32,
ISD::SIGN_EXTEND, ResultReg, ResultRegIsKill);
if (ResultReg == 0)
// Unhandled operand. Halt "fast" selection and bail.
return false;
UpdateValueMap(I, ResultReg);
return true;
}
}
break;
}
}
// An arbitrary call. Bail.
return false;
}
bool FastISel::SelectCast(const User *I, unsigned Opcode) {
EVT SrcVT = TLI.getValueType(I->getOperand(0)->getType());
EVT DstVT = TLI.getValueType(I->getType());
if (SrcVT == MVT::Other || !SrcVT.isSimple() ||
DstVT == MVT::Other || !DstVT.isSimple())
// Unhandled type. Halt "fast" selection and bail.
return false;
// Check if the destination type is legal. Or as a special case,
// it may be i1 if we're doing a truncate because that's
// easy and somewhat common.
if (!TLI.isTypeLegal(DstVT))
if (DstVT != MVT::i1 || Opcode != ISD::TRUNCATE)
// Unhandled type. Halt "fast" selection and bail.
return false;
// Check if the source operand is legal. Or as a special case,
// it may be i1 if we're doing zero-extension because that's
// easy and somewhat common.
if (!TLI.isTypeLegal(SrcVT))
if (SrcVT != MVT::i1 || Opcode != ISD::ZERO_EXTEND)
// Unhandled type. Halt "fast" selection and bail.
return false;
unsigned InputReg = getRegForValue(I->getOperand(0));
if (!InputReg)
// Unhandled operand. Halt "fast" selection and bail.
return false;
bool InputRegIsKill = hasTrivialKill(I->getOperand(0));
// If the operand is i1, arrange for the high bits in the register to be zero.
if (SrcVT == MVT::i1) {
SrcVT = TLI.getTypeToTransformTo(I->getContext(), SrcVT);
InputReg = FastEmitZExtFromI1(SrcVT.getSimpleVT(), InputReg, InputRegIsKill);
if (!InputReg)
return false;
InputRegIsKill = true;
}
// If the result is i1, truncate to the target's type for i1 first.
if (DstVT == MVT::i1)
DstVT = TLI.getTypeToTransformTo(I->getContext(), DstVT);
unsigned ResultReg = FastEmit_r(SrcVT.getSimpleVT(),
DstVT.getSimpleVT(),
Opcode,
InputReg, InputRegIsKill);
if (!ResultReg)
return false;
UpdateValueMap(I, ResultReg);
return true;
}
bool FastISel::SelectBitCast(const User *I) {
// If the bitcast doesn't change the type, just use the operand value.
if (I->getType() == I->getOperand(0)->getType()) {
unsigned Reg = getRegForValue(I->getOperand(0));
if (Reg == 0)
return false;
UpdateValueMap(I, Reg);
return true;
}
// Bitcasts of other values become reg-reg copies or BIT_CONVERT operators.
EVT SrcVT = TLI.getValueType(I->getOperand(0)->getType());
EVT DstVT = TLI.getValueType(I->getType());
if (SrcVT == MVT::Other || !SrcVT.isSimple() ||
DstVT == MVT::Other || !DstVT.isSimple() ||
!TLI.isTypeLegal(SrcVT) || !TLI.isTypeLegal(DstVT))
// Unhandled type. Halt "fast" selection and bail.
return false;
unsigned Op0 = getRegForValue(I->getOperand(0));
if (Op0 == 0)
// Unhandled operand. Halt "fast" selection and bail.
return false;
bool Op0IsKill = hasTrivialKill(I->getOperand(0));
// First, try to perform the bitcast by inserting a reg-reg copy.
unsigned ResultReg = 0;
if (SrcVT.getSimpleVT() == DstVT.getSimpleVT()) {
TargetRegisterClass* SrcClass = TLI.getRegClassFor(SrcVT);
TargetRegisterClass* DstClass = TLI.getRegClassFor(DstVT);
ResultReg = createResultReg(DstClass);
bool InsertedCopy = TII.copyRegToReg(*MBB, MBB->end(), ResultReg,
Op0, DstClass, SrcClass, DL);
if (!InsertedCopy)
ResultReg = 0;
}
// If the reg-reg copy failed, select a BIT_CONVERT opcode.
if (!ResultReg)
ResultReg = FastEmit_r(SrcVT.getSimpleVT(), DstVT.getSimpleVT(),
ISD::BIT_CONVERT, Op0, Op0IsKill);
if (!ResultReg)
return false;
UpdateValueMap(I, ResultReg);
return true;
}
bool
FastISel::SelectInstruction(const Instruction *I) {
// Just before the terminator instruction, insert instructions to
// feed PHI nodes in successor blocks.
if (isa<TerminatorInst>(I))
if (!HandlePHINodesInSuccessorBlocks(I->getParent()))
return false;
DL = I->getDebugLoc();
// First, try doing target-independent selection.
if (SelectOperator(I, I->getOpcode())) {
DL = DebugLoc();
return true;
}
// Next, try calling the target to attempt to handle the instruction.
if (TargetSelectInstruction(I)) {
DL = DebugLoc();
return true;
}
DL = DebugLoc();
return false;
}
/// FastEmitBranch - Emit an unconditional branch to the given block,
/// unless it is the immediate (fall-through) successor, and update
/// the CFG.
void
FastISel::FastEmitBranch(MachineBasicBlock *MSucc) {
if (MBB->isLayoutSuccessor(MSucc)) {
// The unconditional fall-through case, which needs no instructions.
} else {
// The unconditional branch case.
TII.InsertBranch(*MBB, MSucc, NULL, SmallVector<MachineOperand, 0>());
}
MBB->addSuccessor(MSucc);
}
/// SelectFNeg - Emit an FNeg operation.
///
bool
FastISel::SelectFNeg(const User *I) {
unsigned OpReg = getRegForValue(BinaryOperator::getFNegArgument(I));
if (OpReg == 0) return false;
bool OpRegIsKill = hasTrivialKill(I);
// If the target has ISD::FNEG, use it.
EVT VT = TLI.getValueType(I->getType());
unsigned ResultReg = FastEmit_r(VT.getSimpleVT(), VT.getSimpleVT(),
ISD::FNEG, OpReg, OpRegIsKill);
if (ResultReg != 0) {
UpdateValueMap(I, ResultReg);
return true;
}
// Bitcast the value to integer, twiddle the sign bit with xor,
// and then bitcast it back to floating-point.
if (VT.getSizeInBits() > 64) return false;
EVT IntVT = EVT::getIntegerVT(I->getContext(), VT.getSizeInBits());
if (!TLI.isTypeLegal(IntVT))
return false;
unsigned IntReg = FastEmit_r(VT.getSimpleVT(), IntVT.getSimpleVT(),
ISD::BIT_CONVERT, OpReg, OpRegIsKill);
if (IntReg == 0)
return false;
unsigned IntResultReg = FastEmit_ri_(IntVT.getSimpleVT(), ISD::XOR,
IntReg, /*Kill=*/true,
UINT64_C(1) << (VT.getSizeInBits()-1),
IntVT.getSimpleVT());
if (IntResultReg == 0)
return false;
ResultReg = FastEmit_r(IntVT.getSimpleVT(), VT.getSimpleVT(),
ISD::BIT_CONVERT, IntResultReg, /*Kill=*/true);
if (ResultReg == 0)
return false;
UpdateValueMap(I, ResultReg);
return true;
}
bool
FastISel::SelectOperator(const User *I, unsigned Opcode) {
switch (Opcode) {
case Instruction::Add:
return SelectBinaryOp(I, ISD::ADD);
case Instruction::FAdd:
return SelectBinaryOp(I, ISD::FADD);
case Instruction::Sub:
return SelectBinaryOp(I, ISD::SUB);
case Instruction::FSub:
// FNeg is currently represented in LLVM IR as a special case of FSub.
if (BinaryOperator::isFNeg(I))
return SelectFNeg(I);
return SelectBinaryOp(I, ISD::FSUB);
case Instruction::Mul:
return SelectBinaryOp(I, ISD::MUL);
case Instruction::FMul:
return SelectBinaryOp(I, ISD::FMUL);
case Instruction::SDiv:
return SelectBinaryOp(I, ISD::SDIV);
case Instruction::UDiv:
return SelectBinaryOp(I, ISD::UDIV);
case Instruction::FDiv:
return SelectBinaryOp(I, ISD::FDIV);
case Instruction::SRem:
return SelectBinaryOp(I, ISD::SREM);
case Instruction::URem:
return SelectBinaryOp(I, ISD::UREM);
case Instruction::FRem:
return SelectBinaryOp(I, ISD::FREM);
case Instruction::Shl:
return SelectBinaryOp(I, ISD::SHL);
case Instruction::LShr:
return SelectBinaryOp(I, ISD::SRL);
case Instruction::AShr:
return SelectBinaryOp(I, ISD::SRA);
case Instruction::And:
return SelectBinaryOp(I, ISD::AND);
case Instruction::Or:
return SelectBinaryOp(I, ISD::OR);
case Instruction::Xor:
return SelectBinaryOp(I, ISD::XOR);
case Instruction::GetElementPtr:
return SelectGetElementPtr(I);
case Instruction::Br: {
const BranchInst *BI = cast<BranchInst>(I);
if (BI->isUnconditional()) {
const BasicBlock *LLVMSucc = BI->getSuccessor(0);
MachineBasicBlock *MSucc = MBBMap[LLVMSucc];
FastEmitBranch(MSucc);
return true;
}
// Conditional branches are not handed yet.
// Halt "fast" selection and bail.
return false;
}
case Instruction::Unreachable:
// Nothing to emit.
return true;
case Instruction::Alloca:
// FunctionLowering has the static-sized case covered.
if (StaticAllocaMap.count(cast<AllocaInst>(I)))
return true;
// Dynamic-sized alloca is not handled yet.
return false;
case Instruction::Call:
return SelectCall(I);
case Instruction::BitCast:
return SelectBitCast(I);
case Instruction::FPToSI:
return SelectCast(I, ISD::FP_TO_SINT);
case Instruction::ZExt:
return SelectCast(I, ISD::ZERO_EXTEND);
case Instruction::SExt:
return SelectCast(I, ISD::SIGN_EXTEND);
case Instruction::Trunc:
return SelectCast(I, ISD::TRUNCATE);
case Instruction::SIToFP:
return SelectCast(I, ISD::SINT_TO_FP);
case Instruction::IntToPtr: // Deliberate fall-through.
case Instruction::PtrToInt: {
EVT SrcVT = TLI.getValueType(I->getOperand(0)->getType());
EVT DstVT = TLI.getValueType(I->getType());
if (DstVT.bitsGT(SrcVT))
return SelectCast(I, ISD::ZERO_EXTEND);
if (DstVT.bitsLT(SrcVT))
return SelectCast(I, ISD::TRUNCATE);
unsigned Reg = getRegForValue(I->getOperand(0));
if (Reg == 0) return false;
UpdateValueMap(I, Reg);
return true;
}
case Instruction::PHI:
llvm_unreachable("FastISel shouldn't visit PHI nodes!");
default:
// Unhandled instruction. Halt "fast" selection and bail.
return false;
}
}
FastISel::FastISel(MachineFunction &mf,
DenseMap<const Value *, unsigned> &vm,
DenseMap<const BasicBlock *, MachineBasicBlock *> &bm,
DenseMap<const AllocaInst *, int> &am,
std::vector<std::pair<MachineInstr*, unsigned> > &pn
#ifndef NDEBUG
, SmallSet<const Instruction *, 8> &cil
#endif
)
: MBB(0),
ValueMap(vm),
MBBMap(bm),
StaticAllocaMap(am),
PHINodesToUpdate(pn),
#ifndef NDEBUG
CatchInfoLost(cil),
#endif
MF(mf),
MRI(MF.getRegInfo()),
MFI(*MF.getFrameInfo()),
MCP(*MF.getConstantPool()),
TM(MF.getTarget()),
TD(*TM.getTargetData()),
TII(*TM.getInstrInfo()),
TLI(*TM.getTargetLowering()),
IsBottomUp(false) {
}
FastISel::~FastISel() {}
unsigned FastISel::FastEmit_(MVT, MVT,
unsigned) {
return 0;
}
unsigned FastISel::FastEmit_r(MVT, MVT,
unsigned,
unsigned /*Op0*/, bool /*Op0IsKill*/) {
return 0;
}
unsigned FastISel::FastEmit_rr(MVT, MVT,
unsigned,
unsigned /*Op0*/, bool /*Op0IsKill*/,
unsigned /*Op1*/, bool /*Op1IsKill*/) {
return 0;
}
unsigned FastISel::FastEmit_i(MVT, MVT, unsigned, uint64_t /*Imm*/) {
return 0;
}
unsigned FastISel::FastEmit_f(MVT, MVT,
unsigned, const ConstantFP * /*FPImm*/) {
return 0;
}
unsigned FastISel::FastEmit_ri(MVT, MVT,
unsigned,
unsigned /*Op0*/, bool /*Op0IsKill*/,
uint64_t /*Imm*/) {
return 0;
}
unsigned FastISel::FastEmit_rf(MVT, MVT,
unsigned,
unsigned /*Op0*/, bool /*Op0IsKill*/,
const ConstantFP * /*FPImm*/) {
return 0;
}
unsigned FastISel::FastEmit_rri(MVT, MVT,
unsigned,
unsigned /*Op0*/, bool /*Op0IsKill*/,
unsigned /*Op1*/, bool /*Op1IsKill*/,
uint64_t /*Imm*/) {
return 0;
}
/// FastEmit_ri_ - This method is a wrapper of FastEmit_ri. It first tries
/// to emit an instruction with an immediate operand using FastEmit_ri.
/// If that fails, it materializes the immediate into a register and try
/// FastEmit_rr instead.
unsigned FastISel::FastEmit_ri_(MVT VT, unsigned Opcode,
unsigned Op0, bool Op0IsKill,
uint64_t Imm, MVT ImmType) {
// First check if immediate type is legal. If not, we can't use the ri form.
unsigned ResultReg = FastEmit_ri(VT, VT, Opcode, Op0, Op0IsKill, Imm);
if (ResultReg != 0)
return ResultReg;
unsigned MaterialReg = FastEmit_i(ImmType, ImmType, ISD::Constant, Imm);
if (MaterialReg == 0)
return 0;
return FastEmit_rr(VT, VT, Opcode,
Op0, Op0IsKill,
MaterialReg, /*Kill=*/true);
}
/// FastEmit_rf_ - This method is a wrapper of FastEmit_ri. It first tries
/// to emit an instruction with a floating-point immediate operand using
/// FastEmit_rf. If that fails, it materializes the immediate into a register
/// and try FastEmit_rr instead.
unsigned FastISel::FastEmit_rf_(MVT VT, unsigned Opcode,
unsigned Op0, bool Op0IsKill,
const ConstantFP *FPImm, MVT ImmType) {
// First check if immediate type is legal. If not, we can't use the rf form.
unsigned ResultReg = FastEmit_rf(VT, VT, Opcode, Op0, Op0IsKill, FPImm);
if (ResultReg != 0)
return ResultReg;
// Materialize the constant in a register.
unsigned MaterialReg = FastEmit_f(ImmType, ImmType, ISD::ConstantFP, FPImm);
if (MaterialReg == 0) {
// If the target doesn't have a way to directly enter a floating-point
// value into a register, use an alternate approach.
// TODO: The current approach only supports floating-point constants
// that can be constructed by conversion from integer values. This should
// be replaced by code that creates a load from a constant-pool entry,
// which will require some target-specific work.
const APFloat &Flt = FPImm->getValueAPF();
EVT IntVT = TLI.getPointerTy();
uint64_t x[2];
uint32_t IntBitWidth = IntVT.getSizeInBits();
bool isExact;
(void) Flt.convertToInteger(x, IntBitWidth, /*isSigned=*/true,
APFloat::rmTowardZero, &isExact);
if (!isExact)
return 0;
APInt IntVal(IntBitWidth, 2, x);
unsigned IntegerReg = FastEmit_i(IntVT.getSimpleVT(), IntVT.getSimpleVT(),
ISD::Constant, IntVal.getZExtValue());
if (IntegerReg == 0)
return 0;
MaterialReg = FastEmit_r(IntVT.getSimpleVT(), VT,
ISD::SINT_TO_FP, IntegerReg, /*Kill=*/true);
if (MaterialReg == 0)
return 0;
}
return FastEmit_rr(VT, VT, Opcode,
Op0, Op0IsKill,
MaterialReg, /*Kill=*/true);
}
unsigned FastISel::createResultReg(const TargetRegisterClass* RC) {
return MRI.createVirtualRegister(RC);
}
unsigned FastISel::FastEmitInst_(unsigned MachineInstOpcode,
const TargetRegisterClass* RC) {
unsigned ResultReg = createResultReg(RC);
const TargetInstrDesc &II = TII.get(MachineInstOpcode);
BuildMI(MBB, DL, II, ResultReg);
return ResultReg;
}
unsigned FastISel::FastEmitInst_r(unsigned MachineInstOpcode,
const TargetRegisterClass *RC,
unsigned Op0, bool Op0IsKill) {
unsigned ResultReg = createResultReg(RC);
const TargetInstrDesc &II = TII.get(MachineInstOpcode);
if (II.getNumDefs() >= 1)
BuildMI(MBB, DL, II, ResultReg).addReg(Op0, Op0IsKill * RegState::Kill);
else {
BuildMI(MBB, DL, II).addReg(Op0, Op0IsKill * RegState::Kill);
bool InsertedCopy = TII.copyRegToReg(*MBB, MBB->end(), ResultReg,
II.ImplicitDefs[0], RC, RC, DL);
if (!InsertedCopy)
ResultReg = 0;
}
return ResultReg;
}
unsigned FastISel::FastEmitInst_rr(unsigned MachineInstOpcode,
const TargetRegisterClass *RC,
unsigned Op0, bool Op0IsKill,
unsigned Op1, bool Op1IsKill) {
unsigned ResultReg = createResultReg(RC);
const TargetInstrDesc &II = TII.get(MachineInstOpcode);
if (II.getNumDefs() >= 1)
BuildMI(MBB, DL, II, ResultReg)
.addReg(Op0, Op0IsKill * RegState::Kill)
.addReg(Op1, Op1IsKill * RegState::Kill);
else {
BuildMI(MBB, DL, II)
.addReg(Op0, Op0IsKill * RegState::Kill)
.addReg(Op1, Op1IsKill * RegState::Kill);
bool InsertedCopy = TII.copyRegToReg(*MBB, MBB->end(), ResultReg,
II.ImplicitDefs[0], RC, RC, DL);
if (!InsertedCopy)
ResultReg = 0;
}
return ResultReg;
}
unsigned FastISel::FastEmitInst_ri(unsigned MachineInstOpcode,
const TargetRegisterClass *RC,
unsigned Op0, bool Op0IsKill,
uint64_t Imm) {
unsigned ResultReg = createResultReg(RC);
const TargetInstrDesc &II = TII.get(MachineInstOpcode);
if (II.getNumDefs() >= 1)
BuildMI(MBB, DL, II, ResultReg)
.addReg(Op0, Op0IsKill * RegState::Kill)
.addImm(Imm);
else {
BuildMI(MBB, DL, II)
.addReg(Op0, Op0IsKill * RegState::Kill)
.addImm(Imm);
bool InsertedCopy = TII.copyRegToReg(*MBB, MBB->end(), ResultReg,
II.ImplicitDefs[0], RC, RC, DL);
if (!InsertedCopy)
ResultReg = 0;
}
return ResultReg;
}
unsigned FastISel::FastEmitInst_rf(unsigned MachineInstOpcode,
const TargetRegisterClass *RC,
unsigned Op0, bool Op0IsKill,
const ConstantFP *FPImm) {
unsigned ResultReg = createResultReg(RC);
const TargetInstrDesc &II = TII.get(MachineInstOpcode);
if (II.getNumDefs() >= 1)
BuildMI(MBB, DL, II, ResultReg)
.addReg(Op0, Op0IsKill * RegState::Kill)
.addFPImm(FPImm);
else {
BuildMI(MBB, DL, II)
.addReg(Op0, Op0IsKill * RegState::Kill)
.addFPImm(FPImm);
bool InsertedCopy = TII.copyRegToReg(*MBB, MBB->end(), ResultReg,
II.ImplicitDefs[0], RC, RC, DL);
if (!InsertedCopy)
ResultReg = 0;
}
return ResultReg;
}
unsigned FastISel::FastEmitInst_rri(unsigned MachineInstOpcode,
const TargetRegisterClass *RC,
unsigned Op0, bool Op0IsKill,
unsigned Op1, bool Op1IsKill,
uint64_t Imm) {
unsigned ResultReg = createResultReg(RC);
const TargetInstrDesc &II = TII.get(MachineInstOpcode);
if (II.getNumDefs() >= 1)
BuildMI(MBB, DL, II, ResultReg)
.addReg(Op0, Op0IsKill * RegState::Kill)
.addReg(Op1, Op1IsKill * RegState::Kill)
.addImm(Imm);
else {
BuildMI(MBB, DL, II)
.addReg(Op0, Op0IsKill * RegState::Kill)
.addReg(Op1, Op1IsKill * RegState::Kill)
.addImm(Imm);
bool InsertedCopy = TII.copyRegToReg(*MBB, MBB->end(), ResultReg,
II.ImplicitDefs[0], RC, RC, DL);
if (!InsertedCopy)
ResultReg = 0;
}
return ResultReg;
}
unsigned FastISel::FastEmitInst_i(unsigned MachineInstOpcode,
const TargetRegisterClass *RC,
uint64_t Imm) {
unsigned ResultReg = createResultReg(RC);
const TargetInstrDesc &II = TII.get(MachineInstOpcode);
if (II.getNumDefs() >= 1)
BuildMI(MBB, DL, II, ResultReg).addImm(Imm);
else {
BuildMI(MBB, DL, II).addImm(Imm);
bool InsertedCopy = TII.copyRegToReg(*MBB, MBB->end(), ResultReg,
II.ImplicitDefs[0], RC, RC, DL);
if (!InsertedCopy)
ResultReg = 0;
}
return ResultReg;
}
unsigned FastISel::FastEmitInst_extractsubreg(MVT RetVT,
unsigned Op0, bool Op0IsKill,
uint32_t Idx) {
const TargetRegisterClass* RC = MRI.getRegClass(Op0);
unsigned ResultReg = createResultReg(TLI.getRegClassFor(RetVT));
const TargetInstrDesc &II = TII.get(TargetOpcode::EXTRACT_SUBREG);
if (II.getNumDefs() >= 1)
BuildMI(MBB, DL, II, ResultReg)
.addReg(Op0, Op0IsKill * RegState::Kill)
.addImm(Idx);
else {
BuildMI(MBB, DL, II)
.addReg(Op0, Op0IsKill * RegState::Kill)
.addImm(Idx);
bool InsertedCopy = TII.copyRegToReg(*MBB, MBB->end(), ResultReg,
II.ImplicitDefs[0], RC, RC, DL);
if (!InsertedCopy)
ResultReg = 0;
}
return ResultReg;
}
/// FastEmitZExtFromI1 - Emit MachineInstrs to compute the value of Op
/// with all but the least significant bit set to zero.
unsigned FastISel::FastEmitZExtFromI1(MVT VT, unsigned Op0, bool Op0IsKill) {
return FastEmit_ri(VT, VT, ISD::AND, Op0, Op0IsKill, 1);
}
/// HandlePHINodesInSuccessorBlocks - Handle PHI nodes in successor blocks.
/// Emit code to ensure constants are copied into registers when needed.
/// Remember the virtual registers that need to be added to the Machine PHI
/// nodes as input. We cannot just directly add them, because expansion
/// might result in multiple MBB's for one BB. As such, the start of the
/// BB might correspond to a different MBB than the end.
bool FastISel::HandlePHINodesInSuccessorBlocks(const BasicBlock *LLVMBB) {
const TerminatorInst *TI = LLVMBB->getTerminator();
SmallPtrSet<MachineBasicBlock *, 4> SuccsHandled;
unsigned OrigNumPHINodesToUpdate = PHINodesToUpdate.size();
// Check successor nodes' PHI nodes that expect a constant to be available
// from this block.
for (unsigned succ = 0, e = TI->getNumSuccessors(); succ != e; ++succ) {
const BasicBlock *SuccBB = TI->getSuccessor(succ);
if (!isa<PHINode>(SuccBB->begin())) continue;
MachineBasicBlock *SuccMBB = MBBMap[SuccBB];
// If this terminator has multiple identical successors (common for
// switches), only handle each succ once.
if (!SuccsHandled.insert(SuccMBB)) continue;
MachineBasicBlock::iterator MBBI = SuccMBB->begin();
// At this point we know that there is a 1-1 correspondence between LLVM PHI
// nodes and Machine PHI nodes, but the incoming operands have not been
// emitted yet.
for (BasicBlock::const_iterator I = SuccBB->begin();
const PHINode *PN = dyn_cast<PHINode>(I); ++I) {
// Ignore dead phi's.
if (PN->use_empty()) continue;
// Only handle legal types. Two interesting things to note here. First,
// by bailing out early, we may leave behind some dead instructions,
// since SelectionDAG's HandlePHINodesInSuccessorBlocks will insert its
// own moves. Second, this check is necessary becuase FastISel doesn't
// use CreateRegForValue to create registers, so it always creates
// exactly one register for each non-void instruction.
EVT VT = TLI.getValueType(PN->getType(), /*AllowUnknown=*/true);
if (VT == MVT::Other || !TLI.isTypeLegal(VT)) {
// Promote MVT::i1.
if (VT == MVT::i1)
VT = TLI.getTypeToTransformTo(LLVMBB->getContext(), VT);
else {
PHINodesToUpdate.resize(OrigNumPHINodesToUpdate);
return false;
}
}
const Value *PHIOp = PN->getIncomingValueForBlock(LLVMBB);
// Set the DebugLoc for the copy. Prefer the location of the operand
// if there is one; use the location of the PHI otherwise.
DL = PN->getDebugLoc();
if (const Instruction *Inst = dyn_cast<Instruction>(PHIOp))
DL = Inst->getDebugLoc();
unsigned Reg = getRegForValue(PHIOp);
if (Reg == 0) {
PHINodesToUpdate.resize(OrigNumPHINodesToUpdate);
return false;
}
PHINodesToUpdate.push_back(std::make_pair(MBBI++, Reg));
DL = DebugLoc();
}
}
return true;
}
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