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llvm-6502/lib/Target/ARM/Thumb2SizeReduction.cpp
Tilmann Scheller 8e4d0d84a0 [ARM] Remove redundant assignment. 
Found by the Clang static analyzer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221366 91177308-0d34-0410-b5e6-96231b3b80d8
2014-11-05 17:28:19 +00:00

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//===-- Thumb2SizeReduction.cpp - Thumb2 code size reduction pass -*- C++ -*-=//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "ARM.h"
#include "ARMBaseInstrInfo.h"
#include "ARMSubtarget.h"
#include "MCTargetDesc/ARMAddressingModes.h"
#include "Thumb2InstrInfo.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/IR/Function.h" // To access Function attributes
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
#define DEBUG_TYPE "t2-reduce-size"
STATISTIC(NumNarrows, "Number of 32-bit instrs reduced to 16-bit ones");
STATISTIC(Num2Addrs, "Number of 32-bit instrs reduced to 2addr 16-bit ones");
STATISTIC(NumLdSts, "Number of 32-bit load / store reduced to 16-bit ones");
static cl::opt<int> ReduceLimit("t2-reduce-limit",
cl::init(-1), cl::Hidden);
static cl::opt<int> ReduceLimit2Addr("t2-reduce-limit2",
cl::init(-1), cl::Hidden);
static cl::opt<int> ReduceLimitLdSt("t2-reduce-limit3",
cl::init(-1), cl::Hidden);
namespace {
/// ReduceTable - A static table with information on mapping from wide
/// opcodes to narrow
struct ReduceEntry {
uint16_t WideOpc; // Wide opcode
uint16_t NarrowOpc1; // Narrow opcode to transform to
uint16_t NarrowOpc2; // Narrow opcode when it's two-address
uint8_t Imm1Limit; // Limit of immediate field (bits)
uint8_t Imm2Limit; // Limit of immediate field when it's two-address
unsigned LowRegs1 : 1; // Only possible if low-registers are used
unsigned LowRegs2 : 1; // Only possible if low-registers are used (2addr)
unsigned PredCC1 : 2; // 0 - If predicated, cc is on and vice versa.
// 1 - No cc field.
// 2 - Always set CPSR.
unsigned PredCC2 : 2;
unsigned PartFlag : 1; // 16-bit instruction does partial flag update
unsigned Special : 1; // Needs to be dealt with specially
unsigned AvoidMovs: 1; // Avoid movs with shifter operand (for Swift)
};
static const ReduceEntry ReduceTable[] = {
// Wide, Narrow1, Narrow2, imm1,imm2, lo1, lo2, P/C,PF,S,AM
{ ARM::t2ADCrr, 0, ARM::tADC, 0, 0, 0, 1, 0,0, 0,0,0 },
{ ARM::t2ADDri, ARM::tADDi3, ARM::tADDi8, 3, 8, 1, 1, 0,0, 0,1,0 },
{ ARM::t2ADDrr, ARM::tADDrr, ARM::tADDhirr, 0, 0, 1, 0, 0,1, 0,0,0 },
{ ARM::t2ADDSri,ARM::tADDi3, ARM::tADDi8, 3, 8, 1, 1, 2,2, 0,1,0 },
{ ARM::t2ADDSrr,ARM::tADDrr, 0, 0, 0, 1, 0, 2,0, 0,1,0 },
{ ARM::t2ANDrr, 0, ARM::tAND, 0, 0, 0, 1, 0,0, 1,0,0 },
{ ARM::t2ASRri, ARM::tASRri, 0, 5, 0, 1, 0, 0,0, 1,0,1 },
{ ARM::t2ASRrr, 0, ARM::tASRrr, 0, 0, 0, 1, 0,0, 1,0,1 },
{ ARM::t2BICrr, 0, ARM::tBIC, 0, 0, 0, 1, 0,0, 1,0,0 },
//FIXME: Disable CMN, as CCodes are backwards from compare expectations
//{ ARM::t2CMNrr, ARM::tCMN, 0, 0, 0, 1, 0, 2,0, 0,0,0 },
{ ARM::t2CMNzrr, ARM::tCMNz, 0, 0, 0, 1, 0, 2,0, 0,0,0 },
{ ARM::t2CMPri, ARM::tCMPi8, 0, 8, 0, 1, 0, 2,0, 0,0,0 },
{ ARM::t2CMPrr, ARM::tCMPhir, 0, 0, 0, 0, 0, 2,0, 0,1,0 },
{ ARM::t2EORrr, 0, ARM::tEOR, 0, 0, 0, 1, 0,0, 1,0,0 },
// FIXME: adr.n immediate offset must be multiple of 4.
//{ ARM::t2LEApcrelJT,ARM::tLEApcrelJT, 0, 0, 0, 1, 0, 1,0, 0,0,0 },
{ ARM::t2LSLri, ARM::tLSLri, 0, 5, 0, 1, 0, 0,0, 1,0,1 },
{ ARM::t2LSLrr, 0, ARM::tLSLrr, 0, 0, 0, 1, 0,0, 1,0,1 },
{ ARM::t2LSRri, ARM::tLSRri, 0, 5, 0, 1, 0, 0,0, 1,0,1 },
{ ARM::t2LSRrr, 0, ARM::tLSRrr, 0, 0, 0, 1, 0,0, 1,0,1 },
{ ARM::t2MOVi, ARM::tMOVi8, 0, 8, 0, 1, 0, 0,0, 1,0,0 },
{ ARM::t2MOVi16,ARM::tMOVi8, 0, 8, 0, 1, 0, 0,0, 1,1,0 },
// FIXME: Do we need the 16-bit 'S' variant?
{ ARM::t2MOVr,ARM::tMOVr, 0, 0, 0, 0, 0, 1,0, 0,0,0 },
{ ARM::t2MUL, 0, ARM::tMUL, 0, 0, 0, 1, 0,0, 1,0,0 },
{ ARM::t2MVNr, ARM::tMVN, 0, 0, 0, 1, 0, 0,0, 0,0,0 },
{ ARM::t2ORRrr, 0, ARM::tORR, 0, 0, 0, 1, 0,0, 1,0,0 },
{ ARM::t2REV, ARM::tREV, 0, 0, 0, 1, 0, 1,0, 0,0,0 },
{ ARM::t2REV16, ARM::tREV16, 0, 0, 0, 1, 0, 1,0, 0,0,0 },
{ ARM::t2REVSH, ARM::tREVSH, 0, 0, 0, 1, 0, 1,0, 0,0,0 },
{ ARM::t2RORrr, 0, ARM::tROR, 0, 0, 0, 1, 0,0, 1,0,0 },
{ ARM::t2RSBri, ARM::tRSB, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2RSBSri,ARM::tRSB, 0, 0, 0, 1, 0, 2,0, 0,1,0 },
{ ARM::t2SBCrr, 0, ARM::tSBC, 0, 0, 0, 1, 0,0, 0,0,0 },
{ ARM::t2SUBri, ARM::tSUBi3, ARM::tSUBi8, 3, 8, 1, 1, 0,0, 0,0,0 },
{ ARM::t2SUBrr, ARM::tSUBrr, 0, 0, 0, 1, 0, 0,0, 0,0,0 },
{ ARM::t2SUBSri,ARM::tSUBi3, ARM::tSUBi8, 3, 8, 1, 1, 2,2, 0,0,0 },
{ ARM::t2SUBSrr,ARM::tSUBrr, 0, 0, 0, 1, 0, 2,0, 0,0,0 },
{ ARM::t2SXTB, ARM::tSXTB, 0, 0, 0, 1, 0, 1,0, 0,1,0 },
{ ARM::t2SXTH, ARM::tSXTH, 0, 0, 0, 1, 0, 1,0, 0,1,0 },
{ ARM::t2TSTrr, ARM::tTST, 0, 0, 0, 1, 0, 2,0, 0,0,0 },
{ ARM::t2UXTB, ARM::tUXTB, 0, 0, 0, 1, 0, 1,0, 0,1,0 },
{ ARM::t2UXTH, ARM::tUXTH, 0, 0, 0, 1, 0, 1,0, 0,1,0 },
// FIXME: Clean this up after splitting each Thumb load / store opcode
// into multiple ones.
{ ARM::t2LDRi12,ARM::tLDRi, ARM::tLDRspi, 5, 8, 1, 0, 0,0, 0,1,0 },
{ ARM::t2LDRs, ARM::tLDRr, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2LDRBi12,ARM::tLDRBi, 0, 5, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2LDRBs, ARM::tLDRBr, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2LDRHi12,ARM::tLDRHi, 0, 5, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2LDRHs, ARM::tLDRHr, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2LDRSBs,ARM::tLDRSB, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2LDRSHs,ARM::tLDRSH, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2STRi12,ARM::tSTRi, ARM::tSTRspi, 5, 8, 1, 0, 0,0, 0,1,0 },
{ ARM::t2STRs, ARM::tSTRr, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2STRBi12,ARM::tSTRBi, 0, 5, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2STRBs, ARM::tSTRBr, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2STRHi12,ARM::tSTRHi, 0, 5, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2STRHs, ARM::tSTRHr, 0, 0, 0, 1, 0, 0,0, 0,1,0 },
{ ARM::t2LDMIA, ARM::tLDMIA, 0, 0, 0, 1, 1, 1,1, 0,1,0 },
{ ARM::t2LDMIA_RET,0, ARM::tPOP_RET, 0, 0, 1, 1, 1,1, 0,1,0 },
{ ARM::t2LDMIA_UPD,ARM::tLDMIA_UPD,ARM::tPOP,0, 0, 1, 1, 1,1, 0,1,0 },
// ARM::t2STM (with no basereg writeback) has no Thumb1 equivalent
{ ARM::t2STMIA_UPD,ARM::tSTMIA_UPD, 0, 0, 0, 1, 1, 1,1, 0,1,0 },
{ ARM::t2STMDB_UPD, 0, ARM::tPUSH, 0, 0, 1, 1, 1,1, 0,1,0 }
};
class Thumb2SizeReduce : public MachineFunctionPass {
public:
static char ID;
Thumb2SizeReduce();
const Thumb2InstrInfo *TII;
const ARMSubtarget *STI;
bool runOnMachineFunction(MachineFunction &MF) override;
const char *getPassName() const override {
return "Thumb2 instruction size reduction pass";
}
private:
/// ReduceOpcodeMap - Maps wide opcode to index of entry in ReduceTable.
DenseMap<unsigned, unsigned> ReduceOpcodeMap;
bool canAddPseudoFlagDep(MachineInstr *Use, bool IsSelfLoop);
bool VerifyPredAndCC(MachineInstr *MI, const ReduceEntry &Entry,
bool is2Addr, ARMCC::CondCodes Pred,
bool LiveCPSR, bool &HasCC, bool &CCDead);
bool ReduceLoadStore(MachineBasicBlock &MBB, MachineInstr *MI,
const ReduceEntry &Entry);
bool ReduceSpecial(MachineBasicBlock &MBB, MachineInstr *MI,
const ReduceEntry &Entry, bool LiveCPSR, bool IsSelfLoop);
/// ReduceTo2Addr - Reduce a 32-bit instruction to a 16-bit two-address
/// instruction.
bool ReduceTo2Addr(MachineBasicBlock &MBB, MachineInstr *MI,
const ReduceEntry &Entry, bool LiveCPSR,
bool IsSelfLoop);
/// ReduceToNarrow - Reduce a 32-bit instruction to a 16-bit
/// non-two-address instruction.
bool ReduceToNarrow(MachineBasicBlock &MBB, MachineInstr *MI,
const ReduceEntry &Entry, bool LiveCPSR,
bool IsSelfLoop);
/// ReduceMI - Attempt to reduce MI, return true on success.
bool ReduceMI(MachineBasicBlock &MBB, MachineInstr *MI,
bool LiveCPSR, bool IsSelfLoop);
/// ReduceMBB - Reduce width of instructions in the specified basic block.
bool ReduceMBB(MachineBasicBlock &MBB);
bool OptimizeSize;
bool MinimizeSize;
// Last instruction to define CPSR in the current block.
MachineInstr *CPSRDef;
// Was CPSR last defined by a high latency instruction?
// When CPSRDef is null, this refers to CPSR defs in predecessors.
bool HighLatencyCPSR;
struct MBBInfo {
// The flags leaving this block have high latency.
bool HighLatencyCPSR;
// Has this block been visited yet?
bool Visited;
MBBInfo() : HighLatencyCPSR(false), Visited(false) {}
};
SmallVector<MBBInfo, 8> BlockInfo;
};
char Thumb2SizeReduce::ID = 0;
}
Thumb2SizeReduce::Thumb2SizeReduce() : MachineFunctionPass(ID) {
OptimizeSize = MinimizeSize = false;
for (unsigned i = 0, e = array_lengthof(ReduceTable); i != e; ++i) {
unsigned FromOpc = ReduceTable[i].WideOpc;
if (!ReduceOpcodeMap.insert(std::make_pair(FromOpc, i)).second)
assert(false && "Duplicated entries?");
}
}
static bool HasImplicitCPSRDef(const MCInstrDesc &MCID) {
for (const uint16_t *Regs = MCID.getImplicitDefs(); *Regs; ++Regs)
if (*Regs == ARM::CPSR)
return true;
return false;
}
// Check for a likely high-latency flag def.
static bool isHighLatencyCPSR(MachineInstr *Def) {
switch(Def->getOpcode()) {
case ARM::FMSTAT:
case ARM::tMUL:
return true;
}
return false;
}
/// canAddPseudoFlagDep - For A9 (and other out-of-order) implementations,
/// the 's' 16-bit instruction partially update CPSR. Abort the
/// transformation to avoid adding false dependency on last CPSR setting
/// instruction which hurts the ability for out-of-order execution engine
/// to do register renaming magic.
/// This function checks if there is a read-of-write dependency between the
/// last instruction that defines the CPSR and the current instruction. If there
/// is, then there is no harm done since the instruction cannot be retired
/// before the CPSR setting instruction anyway.
/// Note, we are not doing full dependency analysis here for the sake of compile
/// time. We're not looking for cases like:
/// r0 = muls ...
/// r1 = add.w r0, ...
/// ...
/// = mul.w r1
/// In this case it would have been ok to narrow the mul.w to muls since there
/// are indirect RAW dependency between the muls and the mul.w
bool
Thumb2SizeReduce::canAddPseudoFlagDep(MachineInstr *Use, bool FirstInSelfLoop) {
// Disable the check for -Oz (aka OptimizeForSizeHarder).
if (MinimizeSize || !STI->avoidCPSRPartialUpdate())
return false;
if (!CPSRDef)
// If this BB loops back to itself, conservatively avoid narrowing the
// first instruction that does partial flag update.
return HighLatencyCPSR || FirstInSelfLoop;
SmallSet<unsigned, 2> Defs;
for (const MachineOperand &MO : CPSRDef->operands()) {
if (!MO.isReg() || MO.isUndef() || MO.isUse())
continue;
unsigned Reg = MO.getReg();
if (Reg == 0 || Reg == ARM::CPSR)
continue;
Defs.insert(Reg);
}
for (const MachineOperand &MO : Use->operands()) {
if (!MO.isReg() || MO.isUndef() || MO.isDef())
continue;
unsigned Reg = MO.getReg();
if (Defs.count(Reg))
return false;
}
// If the current CPSR has high latency, try to avoid the false dependency.
if (HighLatencyCPSR)
return true;
// tMOVi8 usually doesn't start long dependency chains, and there are a lot
// of them, so always shrink them when CPSR doesn't have high latency.
if (Use->getOpcode() == ARM::t2MOVi ||
Use->getOpcode() == ARM::t2MOVi16)
return false;
// No read-after-write dependency. The narrowing will add false dependency.
return true;
}
bool
Thumb2SizeReduce::VerifyPredAndCC(MachineInstr *MI, const ReduceEntry &Entry,
bool is2Addr, ARMCC::CondCodes Pred,
bool LiveCPSR, bool &HasCC, bool &CCDead) {
if ((is2Addr && Entry.PredCC2 == 0) ||
(!is2Addr && Entry.PredCC1 == 0)) {
if (Pred == ARMCC::AL) {
// Not predicated, must set CPSR.
if (!HasCC) {
// Original instruction was not setting CPSR, but CPSR is not
// currently live anyway. It's ok to set it. The CPSR def is
// dead though.
if (!LiveCPSR) {
HasCC = true;
CCDead = true;
return true;
}
return false;
}
} else {
// Predicated, must not set CPSR.
if (HasCC)
return false;
}
} else if ((is2Addr && Entry.PredCC2 == 2) ||
(!is2Addr && Entry.PredCC1 == 2)) {
/// Old opcode has an optional def of CPSR.
if (HasCC)
return true;
// If old opcode does not implicitly define CPSR, then it's not ok since
// these new opcodes' CPSR def is not meant to be thrown away. e.g. CMP.
if (!HasImplicitCPSRDef(MI->getDesc()))
return false;
HasCC = true;
} else {
// 16-bit instruction does not set CPSR.
if (HasCC)
return false;
}
return true;
}
static bool VerifyLowRegs(MachineInstr *MI) {
unsigned Opc = MI->getOpcode();
bool isPCOk = (Opc == ARM::t2LDMIA_RET || Opc == ARM::t2LDMIA ||
Opc == ARM::t2LDMDB || Opc == ARM::t2LDMIA_UPD ||
Opc == ARM::t2LDMDB_UPD);
bool isLROk = (Opc == ARM::t2STMDB_UPD);
bool isSPOk = isPCOk || isLROk;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || MO.isImplicit())
continue;
unsigned Reg = MO.getReg();
if (Reg == 0 || Reg == ARM::CPSR)
continue;
if (isPCOk && Reg == ARM::PC)
continue;
if (isLROk && Reg == ARM::LR)
continue;
if (Reg == ARM::SP) {
if (isSPOk)
continue;
if (i == 1 && (Opc == ARM::t2LDRi12 || Opc == ARM::t2STRi12))
// Special case for these ldr / str with sp as base register.
continue;
}
if (!isARMLowRegister(Reg))
return false;
}
return true;
}
bool
Thumb2SizeReduce::ReduceLoadStore(MachineBasicBlock &MBB, MachineInstr *MI,
const ReduceEntry &Entry) {
if (ReduceLimitLdSt != -1 && ((int)NumLdSts >= ReduceLimitLdSt))
return false;
unsigned Scale = 1;
bool HasImmOffset = false;
bool HasShift = false;
bool HasOffReg = true;
bool isLdStMul = false;
unsigned Opc = Entry.NarrowOpc1;
unsigned OpNum = 3; // First 'rest' of operands.
uint8_t ImmLimit = Entry.Imm1Limit;
switch (Entry.WideOpc) {
default:
llvm_unreachable("Unexpected Thumb2 load / store opcode!");
case ARM::t2LDRi12:
case ARM::t2STRi12:
if (MI->getOperand(1).getReg() == ARM::SP) {
Opc = Entry.NarrowOpc2;
ImmLimit = Entry.Imm2Limit;
}
Scale = 4;
HasImmOffset = true;
HasOffReg = false;
break;
case ARM::t2LDRBi12:
case ARM::t2STRBi12:
HasImmOffset = true;
HasOffReg = false;
break;
case ARM::t2LDRHi12:
case ARM::t2STRHi12:
Scale = 2;
HasImmOffset = true;
HasOffReg = false;
break;
case ARM::t2LDRs:
case ARM::t2LDRBs:
case ARM::t2LDRHs:
case ARM::t2LDRSBs:
case ARM::t2LDRSHs:
case ARM::t2STRs:
case ARM::t2STRBs:
case ARM::t2STRHs:
HasShift = true;
OpNum = 4;
break;
case ARM::t2LDMIA:
case ARM::t2LDMDB: {
unsigned BaseReg = MI->getOperand(0).getReg();
if (!isARMLowRegister(BaseReg) || Entry.WideOpc != ARM::t2LDMIA)
return false;
// For the non-writeback version (this one), the base register must be
// one of the registers being loaded.
bool isOK = false;
for (unsigned i = 4; i < MI->getNumOperands(); ++i) {
if (MI->getOperand(i).getReg() == BaseReg) {
isOK = true;
break;
}
}
if (!isOK)
return false;
OpNum = 0;
isLdStMul = true;
break;
}
case ARM::t2LDMIA_RET: {
unsigned BaseReg = MI->getOperand(1).getReg();
if (BaseReg != ARM::SP)
return false;
Opc = Entry.NarrowOpc2; // tPOP_RET
OpNum = 2;
isLdStMul = true;
break;
}
case ARM::t2LDMIA_UPD:
case ARM::t2LDMDB_UPD:
case ARM::t2STMIA_UPD:
case ARM::t2STMDB_UPD: {
OpNum = 0;
unsigned BaseReg = MI->getOperand(1).getReg();
if (BaseReg == ARM::SP &&
(Entry.WideOpc == ARM::t2LDMIA_UPD ||
Entry.WideOpc == ARM::t2STMDB_UPD)) {
Opc = Entry.NarrowOpc2; // tPOP or tPUSH
OpNum = 2;
} else if (!isARMLowRegister(BaseReg) ||
(Entry.WideOpc != ARM::t2LDMIA_UPD &&
Entry.WideOpc != ARM::t2STMIA_UPD)) {
return false;
}
isLdStMul = true;
break;
}
}
unsigned OffsetReg = 0;
bool OffsetKill = false;
if (HasShift) {
OffsetReg = MI->getOperand(2).getReg();
OffsetKill = MI->getOperand(2).isKill();
if (MI->getOperand(3).getImm())
// Thumb1 addressing mode doesn't support shift.
return false;
}
unsigned OffsetImm = 0;
if (HasImmOffset) {
OffsetImm = MI->getOperand(2).getImm();
unsigned MaxOffset = ((1 << ImmLimit) - 1) * Scale;
if ((OffsetImm & (Scale - 1)) || OffsetImm > MaxOffset)
// Make sure the immediate field fits.
return false;
}
// Add the 16-bit load / store instruction.
DebugLoc dl = MI->getDebugLoc();
MachineInstrBuilder MIB = BuildMI(MBB, MI, dl, TII->get(Opc));
if (!isLdStMul) {
MIB.addOperand(MI->getOperand(0));
MIB.addOperand(MI->getOperand(1));
if (HasImmOffset)
MIB.addImm(OffsetImm / Scale);
assert((!HasShift || OffsetReg) && "Invalid so_reg load / store address!");
if (HasOffReg)
MIB.addReg(OffsetReg, getKillRegState(OffsetKill));
}
// Transfer the rest of operands.
for (unsigned e = MI->getNumOperands(); OpNum != e; ++OpNum)
MIB.addOperand(MI->getOperand(OpNum));
// Transfer memoperands.
MIB->setMemRefs(MI->memoperands_begin(), MI->memoperands_end());
// Transfer MI flags.
MIB.setMIFlags(MI->getFlags());
DEBUG(errs() << "Converted 32-bit: " << *MI << " to 16-bit: " << *MIB);
MBB.erase_instr(MI);
++NumLdSts;
return true;
}
bool
Thumb2SizeReduce::ReduceSpecial(MachineBasicBlock &MBB, MachineInstr *MI,
const ReduceEntry &Entry,
bool LiveCPSR, bool IsSelfLoop) {
unsigned Opc = MI->getOpcode();
if (Opc == ARM::t2ADDri) {
// If the source register is SP, try to reduce to tADDrSPi, otherwise
// it's a normal reduce.
if (MI->getOperand(1).getReg() != ARM::SP) {
if (ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, IsSelfLoop))
return true;
return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
}
// Try to reduce to tADDrSPi.
unsigned Imm = MI->getOperand(2).getImm();
// The immediate must be in range, the destination register must be a low
// reg, the predicate must be "always" and the condition flags must not
// be being set.
if (Imm & 3 || Imm > 1020)
return false;
if (!isARMLowRegister(MI->getOperand(0).getReg()))
return false;
if (MI->getOperand(3).getImm() != ARMCC::AL)
return false;
const MCInstrDesc &MCID = MI->getDesc();
if (MCID.hasOptionalDef() &&
MI->getOperand(MCID.getNumOperands()-1).getReg() == ARM::CPSR)
return false;
MachineInstrBuilder MIB = BuildMI(MBB, MI, MI->getDebugLoc(),
TII->get(ARM::tADDrSPi))
.addOperand(MI->getOperand(0))
.addOperand(MI->getOperand(1))
.addImm(Imm / 4); // The tADDrSPi has an implied scale by four.
AddDefaultPred(MIB);
// Transfer MI flags.
MIB.setMIFlags(MI->getFlags());
DEBUG(errs() << "Converted 32-bit: " << *MI << " to 16-bit: " <<*MIB);
MBB.erase_instr(MI);
++NumNarrows;
return true;
}
if (Entry.LowRegs1 && !VerifyLowRegs(MI))
return false;
if (MI->mayLoad() || MI->mayStore())
return ReduceLoadStore(MBB, MI, Entry);
switch (Opc) {
default: break;
case ARM::t2ADDSri:
case ARM::t2ADDSrr: {
unsigned PredReg = 0;
if (getInstrPredicate(MI, PredReg) == ARMCC::AL) {
switch (Opc) {
default: break;
case ARM::t2ADDSri: {
if (ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, IsSelfLoop))
return true;
// fallthrough
}
case ARM::t2ADDSrr:
return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
}
}
break;
}
case ARM::t2RSBri:
case ARM::t2RSBSri:
case ARM::t2SXTB:
case ARM::t2SXTH:
case ARM::t2UXTB:
case ARM::t2UXTH:
if (MI->getOperand(2).getImm() == 0)
return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
break;
case ARM::t2MOVi16:
// Can convert only 'pure' immediate operands, not immediates obtained as
// globals' addresses.
if (MI->getOperand(1).isImm())
return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
break;
case ARM::t2CMPrr: {
// Try to reduce to the lo-reg only version first. Why there are two
// versions of the instruction is a mystery.
// It would be nice to just have two entries in the master table that
// are prioritized, but the table assumes a unique entry for each
// source insn opcode. So for now, we hack a local entry record to use.
static const ReduceEntry NarrowEntry =
{ ARM::t2CMPrr,ARM::tCMPr, 0, 0, 0, 1, 1,2, 0, 0,1,0 };
if (ReduceToNarrow(MBB, MI, NarrowEntry, LiveCPSR, IsSelfLoop))
return true;
return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
}
}
return false;
}
bool
Thumb2SizeReduce::ReduceTo2Addr(MachineBasicBlock &MBB, MachineInstr *MI,
const ReduceEntry &Entry,
bool LiveCPSR, bool IsSelfLoop) {
if (ReduceLimit2Addr != -1 && ((int)Num2Addrs >= ReduceLimit2Addr))
return false;
if (!MinimizeSize && !OptimizeSize && Entry.AvoidMovs &&
STI->avoidMOVsShifterOperand())
// Don't issue movs with shifter operand for some CPUs unless we
// are optimizing / minimizing for size.
return false;
unsigned Reg0 = MI->getOperand(0).getReg();
unsigned Reg1 = MI->getOperand(1).getReg();
// t2MUL is "special". The tied source operand is second, not first.
if (MI->getOpcode() == ARM::t2MUL) {
unsigned Reg2 = MI->getOperand(2).getReg();
// Early exit if the regs aren't all low regs.
if (!isARMLowRegister(Reg0) || !isARMLowRegister(Reg1)
|| !isARMLowRegister(Reg2))
return false;
if (Reg0 != Reg2) {
// If the other operand also isn't the same as the destination, we
// can't reduce.
if (Reg1 != Reg0)
return false;
// Try to commute the operands to make it a 2-address instruction.
MachineInstr *CommutedMI = TII->commuteInstruction(MI);
if (!CommutedMI)
return false;
}
} else if (Reg0 != Reg1) {
// Try to commute the operands to make it a 2-address instruction.
unsigned CommOpIdx1, CommOpIdx2;
if (!TII->findCommutedOpIndices(MI, CommOpIdx1, CommOpIdx2) ||
CommOpIdx1 != 1 || MI->getOperand(CommOpIdx2).getReg() != Reg0)
return false;
MachineInstr *CommutedMI = TII->commuteInstruction(MI);
if (!CommutedMI)
return false;
}
if (Entry.LowRegs2 && !isARMLowRegister(Reg0))
return false;
if (Entry.Imm2Limit) {
unsigned Imm = MI->getOperand(2).getImm();
unsigned Limit = (1 << Entry.Imm2Limit) - 1;
if (Imm > Limit)
return false;
} else {
unsigned Reg2 = MI->getOperand(2).getReg();
if (Entry.LowRegs2 && !isARMLowRegister(Reg2))
return false;
}
// Check if it's possible / necessary to transfer the predicate.
const MCInstrDesc &NewMCID = TII->get(Entry.NarrowOpc2);
unsigned PredReg = 0;
ARMCC::CondCodes Pred = getInstrPredicate(MI, PredReg);
bool SkipPred = false;
if (Pred != ARMCC::AL) {
if (!NewMCID.isPredicable())
// Can't transfer predicate, fail.
return false;
} else {
SkipPred = !NewMCID.isPredicable();
}
bool HasCC = false;
bool CCDead = false;
const MCInstrDesc &MCID = MI->getDesc();
if (MCID.hasOptionalDef()) {
unsigned NumOps = MCID.getNumOperands();
HasCC = (MI->getOperand(NumOps-1).getReg() == ARM::CPSR);
if (HasCC && MI->getOperand(NumOps-1).isDead())
CCDead = true;
}
if (!VerifyPredAndCC(MI, Entry, true, Pred, LiveCPSR, HasCC, CCDead))
return false;
// Avoid adding a false dependency on partial flag update by some 16-bit
// instructions which has the 's' bit set.
if (Entry.PartFlag && NewMCID.hasOptionalDef() && HasCC &&
canAddPseudoFlagDep(MI, IsSelfLoop))
return false;
// Add the 16-bit instruction.
DebugLoc dl = MI->getDebugLoc();
MachineInstrBuilder MIB = BuildMI(MBB, MI, dl, NewMCID);
MIB.addOperand(MI->getOperand(0));
if (NewMCID.hasOptionalDef()) {
if (HasCC)
AddDefaultT1CC(MIB, CCDead);
else
AddNoT1CC(MIB);
}
// Transfer the rest of operands.
unsigned NumOps = MCID.getNumOperands();
for (unsigned i = 1, e = MI->getNumOperands(); i != e; ++i) {
if (i < NumOps && MCID.OpInfo[i].isOptionalDef())
continue;
if (SkipPred && MCID.OpInfo[i].isPredicate())
continue;
MIB.addOperand(MI->getOperand(i));
}
// Transfer MI flags.
MIB.setMIFlags(MI->getFlags());
DEBUG(errs() << "Converted 32-bit: " << *MI << " to 16-bit: " << *MIB);
MBB.erase_instr(MI);
++Num2Addrs;
return true;
}
bool
Thumb2SizeReduce::ReduceToNarrow(MachineBasicBlock &MBB, MachineInstr *MI,
const ReduceEntry &Entry,
bool LiveCPSR, bool IsSelfLoop) {
if (ReduceLimit != -1 && ((int)NumNarrows >= ReduceLimit))
return false;
if (!MinimizeSize && !OptimizeSize && Entry.AvoidMovs &&
STI->avoidMOVsShifterOperand())
// Don't issue movs with shifter operand for some CPUs unless we
// are optimizing / minimizing for size.
return false;
unsigned Limit = ~0U;
if (Entry.Imm1Limit)
Limit = (1 << Entry.Imm1Limit) - 1;
const MCInstrDesc &MCID = MI->getDesc();
for (unsigned i = 0, e = MCID.getNumOperands(); i != e; ++i) {
if (MCID.OpInfo[i].isPredicate())
continue;
const MachineOperand &MO = MI->getOperand(i);
if (MO.isReg()) {
unsigned Reg = MO.getReg();
if (!Reg || Reg == ARM::CPSR)
continue;
if (Entry.LowRegs1 && !isARMLowRegister(Reg))
return false;
} else if (MO.isImm() &&
!MCID.OpInfo[i].isPredicate()) {
if (((unsigned)MO.getImm()) > Limit)
return false;
}
}
// Check if it's possible / necessary to transfer the predicate.
const MCInstrDesc &NewMCID = TII->get(Entry.NarrowOpc1);
unsigned PredReg = 0;
ARMCC::CondCodes Pred = getInstrPredicate(MI, PredReg);
bool SkipPred = false;
if (Pred != ARMCC::AL) {
if (!NewMCID.isPredicable())
// Can't transfer predicate, fail.
return false;
} else {
SkipPred = !NewMCID.isPredicable();
}
bool HasCC = false;
bool CCDead = false;
if (MCID.hasOptionalDef()) {
unsigned NumOps = MCID.getNumOperands();
HasCC = (MI->getOperand(NumOps-1).getReg() == ARM::CPSR);
if (HasCC && MI->getOperand(NumOps-1).isDead())
CCDead = true;
}
if (!VerifyPredAndCC(MI, Entry, false, Pred, LiveCPSR, HasCC, CCDead))
return false;
// Avoid adding a false dependency on partial flag update by some 16-bit
// instructions which has the 's' bit set.
if (Entry.PartFlag && NewMCID.hasOptionalDef() && HasCC &&
canAddPseudoFlagDep(MI, IsSelfLoop))
return false;
// Add the 16-bit instruction.
DebugLoc dl = MI->getDebugLoc();
MachineInstrBuilder MIB = BuildMI(MBB, MI, dl, NewMCID);
MIB.addOperand(MI->getOperand(0));
if (NewMCID.hasOptionalDef()) {
if (HasCC)
AddDefaultT1CC(MIB, CCDead);
else
AddNoT1CC(MIB);
}
// Transfer the rest of operands.
unsigned NumOps = MCID.getNumOperands();
for (unsigned i = 1, e = MI->getNumOperands(); i != e; ++i) {
if (i < NumOps && MCID.OpInfo[i].isOptionalDef())
continue;
if ((MCID.getOpcode() == ARM::t2RSBSri ||
MCID.getOpcode() == ARM::t2RSBri ||
MCID.getOpcode() == ARM::t2SXTB ||
MCID.getOpcode() == ARM::t2SXTH ||
MCID.getOpcode() == ARM::t2UXTB ||
MCID.getOpcode() == ARM::t2UXTH) && i == 2)
// Skip the zero immediate operand, it's now implicit.
continue;
bool isPred = (i < NumOps && MCID.OpInfo[i].isPredicate());
if (SkipPred && isPred)
continue;
const MachineOperand &MO = MI->getOperand(i);
if (MO.isReg() && MO.isImplicit() && MO.getReg() == ARM::CPSR)
// Skip implicit def of CPSR. Either it's modeled as an optional
// def now or it's already an implicit def on the new instruction.
continue;
MIB.addOperand(MO);
}
if (!MCID.isPredicable() && NewMCID.isPredicable())
AddDefaultPred(MIB);
// Transfer MI flags.
MIB.setMIFlags(MI->getFlags());
DEBUG(errs() << "Converted 32-bit: " << *MI << " to 16-bit: " << *MIB);
MBB.erase_instr(MI);
++NumNarrows;
return true;
}
static bool UpdateCPSRDef(MachineInstr &MI, bool LiveCPSR, bool &DefCPSR) {
bool HasDef = false;
for (const MachineOperand &MO : MI.operands()) {
if (!MO.isReg() || MO.isUndef() || MO.isUse())
continue;
if (MO.getReg() != ARM::CPSR)
continue;
DefCPSR = true;
if (!MO.isDead())
HasDef = true;
}
return HasDef || LiveCPSR;
}
static bool UpdateCPSRUse(MachineInstr &MI, bool LiveCPSR) {
for (const MachineOperand &MO : MI.operands()) {
if (!MO.isReg() || MO.isUndef() || MO.isDef())
continue;
if (MO.getReg() != ARM::CPSR)
continue;
assert(LiveCPSR && "CPSR liveness tracking is wrong!");
if (MO.isKill()) {
LiveCPSR = false;
break;
}
}
return LiveCPSR;
}
bool Thumb2SizeReduce::ReduceMI(MachineBasicBlock &MBB, MachineInstr *MI,
bool LiveCPSR, bool IsSelfLoop) {
unsigned Opcode = MI->getOpcode();
DenseMap<unsigned, unsigned>::iterator OPI = ReduceOpcodeMap.find(Opcode);
if (OPI == ReduceOpcodeMap.end())
return false;
const ReduceEntry &Entry = ReduceTable[OPI->second];
// Don't attempt normal reductions on "special" cases for now.
if (Entry.Special)
return ReduceSpecial(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
// Try to transform to a 16-bit two-address instruction.
if (Entry.NarrowOpc2 &&
ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, IsSelfLoop))
return true;
// Try to transform to a 16-bit non-two-address instruction.
if (Entry.NarrowOpc1 &&
ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop))
return true;
return false;
}
bool Thumb2SizeReduce::ReduceMBB(MachineBasicBlock &MBB) {
bool Modified = false;
// Yes, CPSR could be livein.
bool LiveCPSR = MBB.isLiveIn(ARM::CPSR);
MachineInstr *BundleMI = nullptr;
CPSRDef = nullptr;
HighLatencyCPSR = false;
// Check predecessors for the latest CPSRDef.
for (auto *Pred : MBB.predecessors()) {
const MBBInfo &PInfo = BlockInfo[Pred->getNumber()];
if (!PInfo.Visited) {
// Since blocks are visited in RPO, this must be a back-edge.
continue;
}
if (PInfo.HighLatencyCPSR) {
HighLatencyCPSR = true;
break;
}
}
// If this BB loops back to itself, conservatively avoid narrowing the
// first instruction that does partial flag update.
bool IsSelfLoop = MBB.isSuccessor(&MBB);
MachineBasicBlock::instr_iterator MII = MBB.instr_begin(),E = MBB.instr_end();
MachineBasicBlock::instr_iterator NextMII;
for (; MII != E; MII = NextMII) {
NextMII = std::next(MII);
MachineInstr *MI = &*MII;
if (MI->isBundle()) {
BundleMI = MI;
continue;
}
if (MI->isDebugValue())
continue;
LiveCPSR = UpdateCPSRUse(*MI, LiveCPSR);
// Does NextMII belong to the same bundle as MI?
bool NextInSameBundle = NextMII != E && NextMII->isBundledWithPred();
if (ReduceMI(MBB, MI, LiveCPSR, IsSelfLoop)) {
Modified = true;
MachineBasicBlock::instr_iterator I = std::prev(NextMII);
MI = &*I;
// Removing and reinserting the first instruction in a bundle will break
// up the bundle. Fix the bundling if it was broken.
if (NextInSameBundle && !NextMII->isBundledWithPred())
NextMII->bundleWithPred();
}
if (!NextInSameBundle && MI->isInsideBundle()) {
// FIXME: Since post-ra scheduler operates on bundles, the CPSR kill
// marker is only on the BUNDLE instruction. Process the BUNDLE
// instruction as we finish with the bundled instruction to work around
// the inconsistency.
if (BundleMI->killsRegister(ARM::CPSR))
LiveCPSR = false;
MachineOperand *MO = BundleMI->findRegisterDefOperand(ARM::CPSR);
if (MO && !MO->isDead())
LiveCPSR = true;
MO = BundleMI->findRegisterUseOperand(ARM::CPSR);
if (MO && !MO->isKill())
LiveCPSR = true;
}
bool DefCPSR = false;
LiveCPSR = UpdateCPSRDef(*MI, LiveCPSR, DefCPSR);
if (MI->isCall()) {
// Calls don't really set CPSR.
CPSRDef = nullptr;
HighLatencyCPSR = false;
IsSelfLoop = false;
} else if (DefCPSR) {
// This is the last CPSR defining instruction.
CPSRDef = MI;
HighLatencyCPSR = isHighLatencyCPSR(CPSRDef);
IsSelfLoop = false;
}
}
MBBInfo &Info = BlockInfo[MBB.getNumber()];
Info.HighLatencyCPSR = HighLatencyCPSR;
Info.Visited = true;
return Modified;
}
bool Thumb2SizeReduce::runOnMachineFunction(MachineFunction &MF) {
const TargetMachine &TM = MF.getTarget();
TII = static_cast<const Thumb2InstrInfo *>(
TM.getSubtargetImpl()->getInstrInfo());
STI = &TM.getSubtarget<ARMSubtarget>();
// Optimizing / minimizing size?
AttributeSet FnAttrs = MF.getFunction()->getAttributes();
OptimizeSize = FnAttrs.hasAttribute(AttributeSet::FunctionIndex,
Attribute::OptimizeForSize);
MinimizeSize =
FnAttrs.hasAttribute(AttributeSet::FunctionIndex, Attribute::MinSize);
BlockInfo.clear();
BlockInfo.resize(MF.getNumBlockIDs());
// Visit blocks in reverse post-order so LastCPSRDef is known for all
// predecessors.
ReversePostOrderTraversal<MachineFunction*> RPOT(&MF);
bool Modified = false;
for (ReversePostOrderTraversal<MachineFunction*>::rpo_iterator
I = RPOT.begin(), E = RPOT.end(); I != E; ++I)
Modified |= ReduceMBB(**I);
return Modified;
}
/// createThumb2SizeReductionPass - Returns an instance of the Thumb2 size
/// reduction pass.
FunctionPass *llvm::createThumb2SizeReductionPass() {
return new Thumb2SizeReduce();
}
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