-//===-- Thumb2ITBlockPass.cpp - Insert Thumb IT blocks -----------*- C++ -*-===//
+//===-- Thumb2ITBlockPass.cpp - Insert Thumb-2 IT blocks ------------------===//
//
// The LLVM Compiler Infrastructure
//
//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "thumb2-it"
#include "ARM.h"
#include "ARMMachineFunctionInfo.h"
#include "Thumb2InstrInfo.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
-#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineInstrBundle.h"
using namespace llvm;
-STATISTIC(NumITs, "Number of IT blocks inserted");
+#define DEBUG_TYPE "thumb2-it"
+
+STATISTIC(NumITs, "Number of IT blocks inserted");
+STATISTIC(NumMovedInsts, "Number of predicated instructions moved");
namespace {
- struct VISIBILITY_HIDDEN Thumb2ITBlockPass : public MachineFunctionPass {
+ class Thumb2ITBlockPass : public MachineFunctionPass {
+ public:
static char ID;
- Thumb2ITBlockPass() : MachineFunctionPass(&ID) {}
+ Thumb2ITBlockPass() : MachineFunctionPass(ID) {}
+ bool restrictIT;
const Thumb2InstrInfo *TII;
+ const TargetRegisterInfo *TRI;
ARMFunctionInfo *AFI;
- virtual bool runOnMachineFunction(MachineFunction &Fn);
+ bool runOnMachineFunction(MachineFunction &Fn) override;
- virtual const char *getPassName() const {
+ const char *getPassName() const override {
return "Thumb IT blocks insertion pass";
}
private:
- bool InsertITBlocks(MachineBasicBlock &MBB);
+ bool MoveCopyOutOfITBlock(MachineInstr *MI,
+ ARMCC::CondCodes CC, ARMCC::CondCodes OCC,
+ SmallSet<unsigned, 4> &Defs,
+ SmallSet<unsigned, 4> &Uses);
+ bool InsertITInstructions(MachineBasicBlock &MBB);
};
char Thumb2ITBlockPass::ID = 0;
}
-static ARMCC::CondCodes getPredicate(const MachineInstr *MI,
- const Thumb2InstrInfo *TII) {
- unsigned Opc = MI->getOpcode();
- if (Opc == ARM::tBcc || Opc == ARM::t2Bcc)
- return ARMCC::AL;
- return TII->getPredicate(MI);
+/// TrackDefUses - Tracking what registers are being defined and used by
+/// instructions in the IT block. This also tracks "dependencies", i.e. uses
+/// in the IT block that are defined before the IT instruction.
+static void TrackDefUses(MachineInstr *MI,
+ SmallSet<unsigned, 4> &Defs,
+ SmallSet<unsigned, 4> &Uses,
+ const TargetRegisterInfo *TRI) {
+ SmallVector<unsigned, 4> LocalDefs;
+ SmallVector<unsigned, 4> LocalUses;
+
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg())
+ continue;
+ unsigned Reg = MO.getReg();
+ if (!Reg || Reg == ARM::ITSTATE || Reg == ARM::SP)
+ continue;
+ if (MO.isUse())
+ LocalUses.push_back(Reg);
+ else
+ LocalDefs.push_back(Reg);
+ }
+
+ for (unsigned i = 0, e = LocalUses.size(); i != e; ++i) {
+ unsigned Reg = LocalUses[i];
+ for (MCSubRegIterator Subreg(Reg, TRI, /*IncludeSelf=*/true);
+ Subreg.isValid(); ++Subreg)
+ Uses.insert(*Subreg);
+ }
+
+ for (unsigned i = 0, e = LocalDefs.size(); i != e; ++i) {
+ unsigned Reg = LocalDefs[i];
+ for (MCSubRegIterator Subreg(Reg, TRI, /*IncludeSelf=*/true);
+ Subreg.isValid(); ++Subreg)
+ Defs.insert(*Subreg);
+ if (Reg == ARM::CPSR)
+ continue;
+ }
+}
+
+static bool isCopy(MachineInstr *MI) {
+ switch (MI->getOpcode()) {
+ default:
+ return false;
+ case ARM::MOVr:
+ case ARM::MOVr_TC:
+ case ARM::tMOVr:
+ case ARM::t2MOVr:
+ return true;
+ }
+}
+
+bool
+Thumb2ITBlockPass::MoveCopyOutOfITBlock(MachineInstr *MI,
+ ARMCC::CondCodes CC, ARMCC::CondCodes OCC,
+ SmallSet<unsigned, 4> &Defs,
+ SmallSet<unsigned, 4> &Uses) {
+ if (!isCopy(MI))
+ return false;
+ // llvm models select's as two-address instructions. That means a copy
+ // is inserted before a t2MOVccr, etc. If the copy is scheduled in
+ // between selects we would end up creating multiple IT blocks.
+ assert(MI->getOperand(0).getSubReg() == 0 &&
+ MI->getOperand(1).getSubReg() == 0 &&
+ "Sub-register indices still around?");
+
+ unsigned DstReg = MI->getOperand(0).getReg();
+ unsigned SrcReg = MI->getOperand(1).getReg();
+
+ // First check if it's safe to move it.
+ if (Uses.count(DstReg) || Defs.count(SrcReg))
+ return false;
+
+ // If the CPSR is defined by this copy, then we don't want to move it. E.g.,
+ // if we have:
+ //
+ // movs r1, r1
+ // rsb r1, 0
+ // movs r2, r2
+ // rsb r2, 0
+ //
+ // we don't want this to be converted to:
+ //
+ // movs r1, r1
+ // movs r2, r2
+ // itt mi
+ // rsb r1, 0
+ // rsb r2, 0
+ //
+ const MCInstrDesc &MCID = MI->getDesc();
+ if (MI->hasOptionalDef() &&
+ MI->getOperand(MCID.getNumOperands() - 1).getReg() == ARM::CPSR)
+ return false;
+
+ // Then peek at the next instruction to see if it's predicated on CC or OCC.
+ // If not, then there is nothing to be gained by moving the copy.
+ MachineBasicBlock::iterator I = MI; ++I;
+ MachineBasicBlock::iterator E = MI->getParent()->end();
+ while (I != E && I->isDebugValue())
+ ++I;
+ if (I != E) {
+ unsigned NPredReg = 0;
+ ARMCC::CondCodes NCC = getITInstrPredicate(I, NPredReg);
+ if (NCC == CC || NCC == OCC)
+ return true;
+ }
+ return false;
}
-bool Thumb2ITBlockPass::InsertITBlocks(MachineBasicBlock &MBB) {
+bool Thumb2ITBlockPass::InsertITInstructions(MachineBasicBlock &MBB) {
bool Modified = false;
+ SmallSet<unsigned, 4> Defs;
+ SmallSet<unsigned, 4> Uses;
MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end();
while (MBBI != E) {
MachineInstr *MI = &*MBBI;
- ARMCC::CondCodes CC = getPredicate(MI, TII);
+ DebugLoc dl = MI->getDebugLoc();
+ unsigned PredReg = 0;
+ ARMCC::CondCodes CC = getITInstrPredicate(MI, PredReg);
if (CC == ARMCC::AL) {
++MBBI;
continue;
}
+ Defs.clear();
+ Uses.clear();
+ TrackDefUses(MI, Defs, Uses, TRI);
+
// Insert an IT instruction.
- DebugLoc dl = MI->getDebugLoc();
MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII->get(ARM::t2IT))
.addImm(CC);
+
+ // Add implicit use of ITSTATE to IT block instructions.
+ MI->addOperand(MachineOperand::CreateReg(ARM::ITSTATE, false/*ifDef*/,
+ true/*isImp*/, false/*isKill*/));
+
+ MachineInstr *LastITMI = MI;
+ MachineBasicBlock::iterator InsertPos = MIB;
++MBBI;
- // Finalize IT mask. If the following instruction is not predicated or it's
- // predicated on a condition that's not the same or the opposite of CC, then
- // the mask is 0x8.
+ // Form IT block.
ARMCC::CondCodes OCC = ARMCC::getOppositeCondition(CC);
- unsigned Mask = 0x8;
- while (MBBI != E || (Mask & 1)) {
- ARMCC::CondCodes NCC = getPredicate(&*MBBI, TII);
- if (NCC == CC) {
- Mask >>= 1;
- Mask |= 0x8;
- } else if (NCC == OCC) {
- Mask >>= 1;
- } else {
- break;
+ unsigned Mask = 0, Pos = 3;
+
+ // v8 IT blocks are limited to one conditional op unless -arm-no-restrict-it
+ // is set: skip the loop
+ if (!restrictIT) {
+ // Branches, including tricky ones like LDM_RET, need to end an IT
+ // block so check the instruction we just put in the block.
+ for (; MBBI != E && Pos &&
+ (!MI->isBranch() && !MI->isReturn()) ; ++MBBI) {
+ if (MBBI->isDebugValue())
+ continue;
+
+ MachineInstr *NMI = &*MBBI;
+ MI = NMI;
+
+ unsigned NPredReg = 0;
+ ARMCC::CondCodes NCC = getITInstrPredicate(NMI, NPredReg);
+ if (NCC == CC || NCC == OCC) {
+ Mask |= (NCC & 1) << Pos;
+ // Add implicit use of ITSTATE.
+ NMI->addOperand(MachineOperand::CreateReg(ARM::ITSTATE, false/*ifDef*/,
+ true/*isImp*/, false/*isKill*/));
+ LastITMI = NMI;
+ } else {
+ if (NCC == ARMCC::AL &&
+ MoveCopyOutOfITBlock(NMI, CC, OCC, Defs, Uses)) {
+ --MBBI;
+ MBB.remove(NMI);
+ MBB.insert(InsertPos, NMI);
+ ++NumMovedInsts;
+ continue;
+ }
+ break;
+ }
+ TrackDefUses(NMI, Defs, Uses, TRI);
+ --Pos;
}
- ++MBBI;
}
+
+ // Finalize IT mask.
+ Mask |= (1 << Pos);
+ // Tag along (firstcond[0] << 4) with the mask.
+ Mask |= (CC & 1) << 4;
MIB.addImm(Mask);
+
+ // Last instruction in IT block kills ITSTATE.
+ LastITMI->findRegisterUseOperand(ARM::ITSTATE)->setIsKill();
+
+ // Finalize the bundle.
+ MachineBasicBlock::instr_iterator LI = LastITMI;
+ finalizeBundle(MBB, InsertPos.getInstrIterator(), std::next(LI));
+
Modified = true;
++NumITs;
}
bool Thumb2ITBlockPass::runOnMachineFunction(MachineFunction &Fn) {
const TargetMachine &TM = Fn.getTarget();
AFI = Fn.getInfo<ARMFunctionInfo>();
- TII = static_cast<const Thumb2InstrInfo*>(TM.getInstrInfo());
+ TII = static_cast<const Thumb2InstrInfo *>(
+ TM.getSubtargetImpl()->getInstrInfo());
+ TRI = TM.getSubtargetImpl()->getRegisterInfo();
+ restrictIT = TM.getSubtarget<ARMSubtarget>().restrictIT();
if (!AFI->isThumbFunction())
return false;
bool Modified = false;
- for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
- ++MFI) {
+ for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E; ) {
MachineBasicBlock &MBB = *MFI;
- Modified |= InsertITBlocks(MBB);
+ ++MFI;
+ Modified |= InsertITInstructions(MBB);
}
+ if (Modified)
+ AFI->setHasITBlocks(true);
+
return Modified;
}
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