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llvm/lib/Target/ARM/ARMInstrInfo.cpp
Dale Johannesen 66a2a8f878 ARM: make branch folder remove unconditional branches 
following jump tables that it earlier inserted.  This
would be OK on other targets but is needed for correctness
only on ARM (constant islands needs to find jump tables).



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@39782 91177308-0d34-0410-b5e6-96231b3b80d8
2007-07-12 16:45:35 +00:00

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//===- ARMInstrInfo.cpp - ARM Instruction Information -----------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the "Instituto Nokia de Tecnologia" and
// is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the ARM implementation of the TargetInstrInfo class.
//
//===----------------------------------------------------------------------===//
#include "ARMInstrInfo.h"
#include "ARM.h"
#include "ARMAddressingModes.h"
#include "ARMGenInstrInfo.inc"
#include "ARMMachineFunctionInfo.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/Target/TargetAsmInfo.h"
#include "llvm/Support/CommandLine.h"
using namespace llvm;
static cl::opt<bool> EnableARM3Addr("enable-arm-3-addr-conv", cl::Hidden,
cl::desc("Enable ARM 2-addr to 3-addr conv"));
ARMInstrInfo::ARMInstrInfo(const ARMSubtarget &STI)
: TargetInstrInfo(ARMInsts, sizeof(ARMInsts)/sizeof(ARMInsts[0])),
RI(*this, STI) {
}
const TargetRegisterClass *ARMInstrInfo::getPointerRegClass() const {
return &ARM::GPRRegClass;
}
/// Return true if the instruction is a register to register move and
/// leave the source and dest operands in the passed parameters.
///
bool ARMInstrInfo::isMoveInstr(const MachineInstr &MI,
unsigned &SrcReg, unsigned &DstReg) const {
MachineOpCode oc = MI.getOpcode();
switch (oc) {
default:
return false;
case ARM::FCPYS:
case ARM::FCPYD:
SrcReg = MI.getOperand(1).getReg();
DstReg = MI.getOperand(0).getReg();
return true;
case ARM::MOVr:
case ARM::tMOVr:
assert(MI.getInstrDescriptor()->numOperands >= 2 &&
MI.getOperand(0).isRegister() &&
MI.getOperand(1).isRegister() &&
"Invalid ARM MOV instruction");
SrcReg = MI.getOperand(1).getReg();
DstReg = MI.getOperand(0).getReg();
return true;
}
}
unsigned ARMInstrInfo::isLoadFromStackSlot(MachineInstr *MI, int &FrameIndex) const{
switch (MI->getOpcode()) {
default: break;
case ARM::LDR:
if (MI->getOperand(1).isFrameIndex() &&
MI->getOperand(2).isReg() &&
MI->getOperand(3).isImmediate() &&
MI->getOperand(2).getReg() == 0 &&
MI->getOperand(3).getImmedValue() == 0) {
FrameIndex = MI->getOperand(1).getFrameIndex();
return MI->getOperand(0).getReg();
}
break;
case ARM::FLDD:
case ARM::FLDS:
if (MI->getOperand(1).isFrameIndex() &&
MI->getOperand(2).isImmediate() &&
MI->getOperand(2).getImmedValue() == 0) {
FrameIndex = MI->getOperand(1).getFrameIndex();
return MI->getOperand(0).getReg();
}
break;
case ARM::tRestore:
if (MI->getOperand(1).isFrameIndex() &&
MI->getOperand(2).isImmediate() &&
MI->getOperand(2).getImmedValue() == 0) {
FrameIndex = MI->getOperand(1).getFrameIndex();
return MI->getOperand(0).getReg();
}
break;
}
return 0;
}
unsigned ARMInstrInfo::isStoreToStackSlot(MachineInstr *MI, int &FrameIndex) const {
switch (MI->getOpcode()) {
default: break;
case ARM::STR:
if (MI->getOperand(1).isFrameIndex() &&
MI->getOperand(2).isReg() &&
MI->getOperand(3).isImmediate() &&
MI->getOperand(2).getReg() == 0 &&
MI->getOperand(3).getImmedValue() == 0) {
FrameIndex = MI->getOperand(1).getFrameIndex();
return MI->getOperand(0).getReg();
}
break;
case ARM::FSTD:
case ARM::FSTS:
if (MI->getOperand(1).isFrameIndex() &&
MI->getOperand(2).isImmediate() &&
MI->getOperand(2).getImmedValue() == 0) {
FrameIndex = MI->getOperand(1).getFrameIndex();
return MI->getOperand(0).getReg();
}
break;
case ARM::tSpill:
if (MI->getOperand(1).isFrameIndex() &&
MI->getOperand(2).isImmediate() &&
MI->getOperand(2).getImmedValue() == 0) {
FrameIndex = MI->getOperand(1).getFrameIndex();
return MI->getOperand(0).getReg();
}
break;
}
return 0;
}
static unsigned getUnindexedOpcode(unsigned Opc) {
switch (Opc) {
default: break;
case ARM::LDR_PRE:
case ARM::LDR_POST:
return ARM::LDR;
case ARM::LDRH_PRE:
case ARM::LDRH_POST:
return ARM::LDRH;
case ARM::LDRB_PRE:
case ARM::LDRB_POST:
return ARM::LDRB;
case ARM::LDRSH_PRE:
case ARM::LDRSH_POST:
return ARM::LDRSH;
case ARM::LDRSB_PRE:
case ARM::LDRSB_POST:
return ARM::LDRSB;
case ARM::STR_PRE:
case ARM::STR_POST:
return ARM::STR;
case ARM::STRH_PRE:
case ARM::STRH_POST:
return ARM::STRH;
case ARM::STRB_PRE:
case ARM::STRB_POST:
return ARM::STRB;
}
return 0;
}
MachineInstr *
ARMInstrInfo::convertToThreeAddress(MachineFunction::iterator &MFI,
MachineBasicBlock::iterator &MBBI,
LiveVariables &LV) const {
if (!EnableARM3Addr)
return NULL;
MachineInstr *MI = MBBI;
unsigned TSFlags = MI->getInstrDescriptor()->TSFlags;
bool isPre = false;
switch ((TSFlags & ARMII::IndexModeMask) >> ARMII::IndexModeShift) {
default: return NULL;
case ARMII::IndexModePre:
isPre = true;
break;
case ARMII::IndexModePost:
break;
}
// Try spliting an indexed load / store to a un-indexed one plus an add/sub
// operation.
unsigned MemOpc = getUnindexedOpcode(MI->getOpcode());
if (MemOpc == 0)
return NULL;
MachineInstr *UpdateMI = NULL;
MachineInstr *MemMI = NULL;
unsigned AddrMode = (TSFlags & ARMII::AddrModeMask);
const TargetInstrDescriptor *TID = MI->getInstrDescriptor();
unsigned NumOps = TID->numOperands;
bool isLoad = (TID->Flags & M_LOAD_FLAG) != 0;
const MachineOperand &WB = isLoad ? MI->getOperand(1) : MI->getOperand(0);
const MachineOperand &Base = MI->getOperand(2);
const MachineOperand &Offset = MI->getOperand(NumOps-3);
unsigned WBReg = WB.getReg();
unsigned BaseReg = Base.getReg();
unsigned OffReg = Offset.getReg();
unsigned OffImm = MI->getOperand(NumOps-2).getImm();
ARMCC::CondCodes Pred = (ARMCC::CondCodes)MI->getOperand(NumOps-1).getImm();
switch (AddrMode) {
default:
assert(false && "Unknown indexed op!");
return NULL;
case ARMII::AddrMode2: {
bool isSub = ARM_AM::getAM2Op(OffImm) == ARM_AM::sub;
unsigned Amt = ARM_AM::getAM2Offset(OffImm);
if (OffReg == 0) {
int SOImmVal = ARM_AM::getSOImmVal(Amt);
if (SOImmVal == -1)
// Can't encode it in a so_imm operand. This transformation will
// add more than 1 instruction. Abandon!
return NULL;
UpdateMI = BuildMI(get(isSub ? ARM::SUBri : ARM::ADDri), WBReg)
.addReg(BaseReg).addImm(SOImmVal)
.addImm(Pred).addReg(0).addReg(0);
} else if (Amt != 0) {
ARM_AM::ShiftOpc ShOpc = ARM_AM::getAM2ShiftOpc(OffImm);
unsigned SOOpc = ARM_AM::getSORegOpc(ShOpc, Amt);
UpdateMI = BuildMI(get(isSub ? ARM::SUBrs : ARM::ADDrs), WBReg)
.addReg(BaseReg).addReg(OffReg).addReg(0).addImm(SOOpc)
.addImm(Pred).addReg(0).addReg(0);
} else
UpdateMI = BuildMI(get(isSub ? ARM::SUBrr : ARM::ADDrr), WBReg)
.addReg(BaseReg).addReg(OffReg)
.addImm(Pred).addReg(0).addReg(0);
break;
}
case ARMII::AddrMode3 : {
bool isSub = ARM_AM::getAM3Op(OffImm) == ARM_AM::sub;
unsigned Amt = ARM_AM::getAM3Offset(OffImm);
if (OffReg == 0)
// Immediate is 8-bits. It's guaranteed to fit in a so_imm operand.
UpdateMI = BuildMI(get(isSub ? ARM::SUBri : ARM::ADDri), WBReg)
.addReg(BaseReg).addImm(Amt)
.addImm(Pred).addReg(0).addReg(0);
else
UpdateMI = BuildMI(get(isSub ? ARM::SUBrr : ARM::ADDrr), WBReg)
.addReg(BaseReg).addReg(OffReg)
.addImm(Pred).addReg(0).addReg(0);
break;
}
}
std::vector<MachineInstr*> NewMIs;
if (isPre) {
if (isLoad)
MemMI = BuildMI(get(MemOpc), MI->getOperand(0).getReg())
.addReg(WBReg).addReg(0).addImm(0).addImm(Pred);
else
MemMI = BuildMI(get(MemOpc)).addReg(MI->getOperand(1).getReg())
.addReg(WBReg).addReg(0).addImm(0).addImm(Pred);
NewMIs.push_back(MemMI);
NewMIs.push_back(UpdateMI);
} else {
if (isLoad)
MemMI = BuildMI(get(MemOpc), MI->getOperand(0).getReg())
.addReg(BaseReg).addReg(0).addImm(0).addImm(Pred);
else
MemMI = BuildMI(get(MemOpc)).addReg(MI->getOperand(1).getReg())
.addReg(BaseReg).addReg(0).addImm(0).addImm(Pred);
if (WB.isDead())
UpdateMI->getOperand(0).setIsDead();
NewMIs.push_back(UpdateMI);
NewMIs.push_back(MemMI);
}
// Transfer LiveVariables states, kill / dead info.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (MO.isRegister() && MO.getReg() &&
MRegisterInfo::isVirtualRegister(MO.getReg())) {
unsigned Reg = MO.getReg();
LiveVariables::VarInfo &VI = LV.getVarInfo(Reg);
if (MO.isDef()) {
MachineInstr *NewMI = (Reg == WBReg) ? UpdateMI : MemMI;
if (MO.isDead())
LV.addVirtualRegisterDead(Reg, NewMI);
// Update the defining instruction.
if (VI.DefInst == MI)
VI.DefInst = NewMI;
}
if (MO.isUse() && MO.isKill()) {
for (unsigned j = 0; j < 2; ++j) {
// Look at the two new MI's in reverse order.
MachineInstr *NewMI = NewMIs[j];
int NIdx = NewMI->findRegisterUseOperandIdx(Reg);
if (NIdx == -1)
continue;
LV.addVirtualRegisterKilled(Reg, NewMI);
if (VI.removeKill(MI))
VI.Kills.push_back(NewMI);
break;
}
}
}
}
MFI->insert(MBBI, NewMIs[1]);
MFI->insert(MBBI, NewMIs[0]);
return NewMIs[0];
}
// Branch analysis.
bool ARMInstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,MachineBasicBlock *&TBB,
MachineBasicBlock *&FBB,
std::vector<MachineOperand> &Cond) const {
// If the block has no terminators, it just falls into the block after it.
MachineBasicBlock::iterator I = MBB.end();
if (I == MBB.begin() || !isUnpredicatedTerminator(--I))
return false;
// Get the last instruction in the block.
MachineInstr *LastInst = I;
// If there is only one terminator instruction, process it.
unsigned LastOpc = LastInst->getOpcode();
if (I == MBB.begin() || !isUnpredicatedTerminator(--I)) {
if (LastOpc == ARM::B || LastOpc == ARM::tB) {
TBB = LastInst->getOperand(0).getMachineBasicBlock();
return false;
}
if (LastOpc == ARM::Bcc || LastOpc == ARM::tBcc) {
// Block ends with fall-through condbranch.
TBB = LastInst->getOperand(0).getMachineBasicBlock();
Cond.push_back(LastInst->getOperand(1));
Cond.push_back(LastInst->getOperand(2));
return false;
}
return true; // Can't handle indirect branch.
}
// Get the instruction before it if it is a terminator.
MachineInstr *SecondLastInst = I;
// If there are three terminators, we don't know what sort of block this is.
if (SecondLastInst && I != MBB.begin() && isUnpredicatedTerminator(--I))
return true;
// If the block ends with ARM::B/ARM::tB and a ARM::Bcc/ARM::tBcc, handle it.
unsigned SecondLastOpc = SecondLastInst->getOpcode();
if ((SecondLastOpc == ARM::Bcc && LastOpc == ARM::B) ||
(SecondLastOpc == ARM::tBcc && LastOpc == ARM::tB)) {
TBB = SecondLastInst->getOperand(0).getMachineBasicBlock();
Cond.push_back(SecondLastInst->getOperand(1));
Cond.push_back(SecondLastInst->getOperand(2));
FBB = LastInst->getOperand(0).getMachineBasicBlock();
return false;
}
// If the block ends with two unconditional branches, handle it. The second
// one is not executed, so remove it.
if ((SecondLastOpc == ARM::B || SecondLastOpc==ARM::tB) &&
(LastOpc == ARM::B || LastOpc == ARM::tB)) {
TBB = SecondLastInst->getOperand(0).getMachineBasicBlock();
I = LastInst;
I->eraseFromParent();
return false;
}
// Likewise if it ends with a branch table followed by an unconditional branch.
// The branch folder can create these, and we must get rid of them for
// correctness of Thumb constant islands.
if ((SecondLastOpc == ARM::BR_JTr || SecondLastOpc==ARM::BR_JTm ||
SecondLastOpc == ARM::BR_JTadd || SecondLastOpc==ARM::tBR_JTr) &&
(LastOpc == ARM::B || LastOpc == ARM::tB)) {
I = LastInst;
I->eraseFromParent();
return true;
}
// Otherwise, can't handle this.
return true;
}
unsigned ARMInstrInfo::RemoveBranch(MachineBasicBlock &MBB) const {
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
int BOpc = AFI->isThumbFunction() ? ARM::tB : ARM::B;
int BccOpc = AFI->isThumbFunction() ? ARM::tBcc : ARM::Bcc;
MachineBasicBlock::iterator I = MBB.end();
if (I == MBB.begin()) return 0;
--I;
if (I->getOpcode() != BOpc && I->getOpcode() != BccOpc)
return 0;
// Remove the branch.
I->eraseFromParent();
I = MBB.end();
if (I == MBB.begin()) return 1;
--I;
if (I->getOpcode() != BccOpc)
return 1;
// Remove the branch.
I->eraseFromParent();
return 2;
}
unsigned ARMInstrInfo::InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
MachineBasicBlock *FBB,
const std::vector<MachineOperand> &Cond) const {
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
int BOpc = AFI->isThumbFunction() ? ARM::tB : ARM::B;
int BccOpc = AFI->isThumbFunction() ? ARM::tBcc : ARM::Bcc;
// Shouldn't be a fall through.
assert(TBB && "InsertBranch must not be told to insert a fallthrough");
assert((Cond.size() == 2 || Cond.size() == 0) &&
"ARM branch conditions have two components!");
if (FBB == 0) {
if (Cond.empty()) // Unconditional branch?
BuildMI(&MBB, get(BOpc)).addMBB(TBB);
else
BuildMI(&MBB, get(BccOpc)).addMBB(TBB)
.addImm(Cond[0].getImm()).addReg(Cond[1].getReg());
return 1;
}
// Two-way conditional branch.
BuildMI(&MBB, get(BccOpc)).addMBB(TBB)
.addImm(Cond[0].getImm()).addReg(Cond[1].getReg());
BuildMI(&MBB, get(BOpc)).addMBB(FBB);
return 2;
}
bool ARMInstrInfo::BlockHasNoFallThrough(MachineBasicBlock &MBB) const {
if (MBB.empty()) return false;
switch (MBB.back().getOpcode()) {
case ARM::BX_RET: // Return.
case ARM::LDM_RET:
case ARM::tBX_RET:
case ARM::tBX_RET_vararg:
case ARM::tPOP_RET:
case ARM::B:
case ARM::tB: // Uncond branch.
case ARM::tBR_JTr:
case ARM::BR_JTr: // Jumptable branch.
case ARM::BR_JTm: // Jumptable branch through mem.
case ARM::BR_JTadd: // Jumptable branch add to pc.
return true;
default: return false;
}
}
bool ARMInstrInfo::
ReverseBranchCondition(std::vector<MachineOperand> &Cond) const {
ARMCC::CondCodes CC = (ARMCC::CondCodes)(int)Cond[0].getImm();
Cond[0].setImm(ARMCC::getOppositeCondition(CC));
return false;
}
bool ARMInstrInfo::isPredicated(const MachineInstr *MI) const {
int PIdx = MI->findFirstPredOperandIdx();
return PIdx != -1 && MI->getOperand(PIdx).getImmedValue() != ARMCC::AL;
}
bool ARMInstrInfo::PredicateInstruction(MachineInstr *MI,
const std::vector<MachineOperand> &Pred) const {
unsigned Opc = MI->getOpcode();
if (Opc == ARM::B || Opc == ARM::tB) {
MI->setInstrDescriptor(get(Opc == ARM::B ? ARM::Bcc : ARM::tBcc));
MI->addImmOperand(Pred[0].getImmedValue());
MI->addRegOperand(Pred[1].getReg(), false);
return true;
}
int PIdx = MI->findFirstPredOperandIdx();
if (PIdx != -1) {
MachineOperand &PMO = MI->getOperand(PIdx);
PMO.setImm(Pred[0].getImmedValue());
MI->getOperand(PIdx+1).setReg(Pred[1].getReg());
return true;
}
return false;
}
bool
ARMInstrInfo::SubsumesPredicate(const std::vector<MachineOperand> &Pred1,
const std::vector<MachineOperand> &Pred2) const{
if (Pred1.size() > 2 || Pred2.size() > 2)
return false;
ARMCC::CondCodes CC1 = (ARMCC::CondCodes)Pred1[0].getImmedValue();
ARMCC::CondCodes CC2 = (ARMCC::CondCodes)Pred2[0].getImmedValue();
if (CC1 == CC2)
return true;
switch (CC1) {
default:
return false;
case ARMCC::AL:
return true;
case ARMCC::HS:
return CC2 == ARMCC::HI;
case ARMCC::LS:
return CC2 == ARMCC::LO || CC2 == ARMCC::EQ;
case ARMCC::GE:
return CC2 == ARMCC::GT;
case ARMCC::LE:
return CC2 == ARMCC::LT;
}
}
bool ARMInstrInfo::DefinesPredicate(MachineInstr *MI,
std::vector<MachineOperand> &Pred) const {
const TargetInstrDescriptor *TID = MI->getInstrDescriptor();
if (!TID->ImplicitDefs && (TID->Flags & M_HAS_OPTIONAL_DEF) == 0)
return false;
bool Found = false;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (MO.isReg() && MO.getReg() == ARM::CPSR) {
Pred.push_back(MO);
Found = true;
}
}
return Found;
}
/// FIXME: Works around a gcc miscompilation with -fstrict-aliasing
static unsigned getNumJTEntries(const std::vector<MachineJumpTableEntry> &JT,
unsigned JTI) DISABLE_INLINE;
static unsigned getNumJTEntries(const std::vector<MachineJumpTableEntry> &JT,
unsigned JTI) {
return JT[JTI].MBBs.size();
}
/// GetInstSize - Return the size of the specified MachineInstr.
///
unsigned ARM::GetInstSize(MachineInstr *MI) {
MachineBasicBlock &MBB = *MI->getParent();
const MachineFunction *MF = MBB.getParent();
const TargetAsmInfo *TAI = MF->getTarget().getTargetAsmInfo();
// Basic size info comes from the TSFlags field.
const TargetInstrDescriptor *TID = MI->getInstrDescriptor();
unsigned TSFlags = TID->TSFlags;
switch ((TSFlags & ARMII::SizeMask) >> ARMII::SizeShift) {
default:
// If this machine instr is an inline asm, measure it.
if (MI->getOpcode() == ARM::INLINEASM)
return TAI->getInlineAsmLength(MI->getOperand(0).getSymbolName());
if (MI->getOpcode() == ARM::LABEL)
return 0;
assert(0 && "Unknown or unset size field for instr!");
break;
case ARMII::Size8Bytes: return 8; // Arm instruction x 2.
case ARMII::Size4Bytes: return 4; // Arm instruction.
case ARMII::Size2Bytes: return 2; // Thumb instruction.
case ARMII::SizeSpecial: {
switch (MI->getOpcode()) {
case ARM::CONSTPOOL_ENTRY:
// If this machine instr is a constant pool entry, its size is recorded as
// operand #2.
return MI->getOperand(2).getImm();
case ARM::BR_JTr:
case ARM::BR_JTm:
case ARM::BR_JTadd:
case ARM::tBR_JTr: {
// These are jumptable branches, i.e. a branch followed by an inlined
// jumptable. The size is 4 + 4 * number of entries.
unsigned NumOps = TID->numOperands;
MachineOperand JTOP =
MI->getOperand(NumOps - ((TID->Flags & M_PREDICABLE) ? 3 : 2));
unsigned JTI = JTOP.getJumpTableIndex();
MachineJumpTableInfo *MJTI = MF->getJumpTableInfo();
const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
assert(JTI < JT.size());
// Thumb instructions are 2 byte aligned, but JT entries are 4 byte
// 4 aligned. The assembler / linker may add 2 byte padding just before
// the JT entries. The size does not include this padding; the
// constant islands pass does separate bookkeeping for it.
// FIXME: If we know the size of the function is less than (1 << 16) *2
// bytes, we can use 16-bit entries instead. Then there won't be an
// alignment issue.
return getNumJTEntries(JT, JTI) * 4 +
(MI->getOpcode()==ARM::tBR_JTr ? 2 : 4);
}
default:
// Otherwise, pseudo-instruction sizes are zero.
return 0;
}
}
}
}
/// GetFunctionSize - Returns the size of the specified MachineFunction.
///
unsigned ARM::GetFunctionSize(MachineFunction &MF) {
unsigned FnSize = 0;
for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
MBBI != E; ++MBBI) {
MachineBasicBlock &MBB = *MBBI;
for (MachineBasicBlock::iterator I = MBB.begin(),E = MBB.end(); I != E; ++I)
FnSize += ARM::GetInstSize(I);
}
return FnSize;
}
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