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Fill delay slot with useful instructions. Modified from Sparc's version of delay
slot filler. Patch by Reed Kotler at Mips Technologies. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140825 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -7,7 +7,7 @@
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//
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//
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//===----------------------------------------------------------------------===//
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//===----------------------------------------------------------------------===//
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//
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//
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// Simple pass to fills delay slots with NOPs.
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// Simple pass to fills delay slots with useful instructions.
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//
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//
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//===----------------------------------------------------------------------===//
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//===----------------------------------------------------------------------===//
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@ -17,13 +17,23 @@
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#include "MipsTargetMachine.h"
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#include "MipsTargetMachine.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/Statistic.h"
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using namespace llvm;
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using namespace llvm;
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STATISTIC(FilledSlots, "Number of delay slots filled");
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STATISTIC(FilledSlots, "Number of delay slots filled");
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static cl::opt<bool> EnableDelaySlotFiller(
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"enable-mips-delay-filler",
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cl::init(false),
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cl::desc("Fill the Mips delay slots with noop."),
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cl::Hidden);
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namespace {
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namespace {
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struct Filler : public MachineFunctionPass {
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struct Filler : public MachineFunctionPass {
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@ -47,29 +57,56 @@ namespace {
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return Changed;
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return Changed;
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}
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}
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bool isDelayFiller(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator candidate);
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void insertCallUses(MachineBasicBlock::iterator MI,
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SmallSet<unsigned, 32>& RegDefs,
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SmallSet<unsigned, 32>& RegUses);
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void insertDefsUses(MachineBasicBlock::iterator MI,
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SmallSet<unsigned, 32>& RegDefs,
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SmallSet<unsigned, 32>& RegUses);
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bool IsRegInSet(SmallSet<unsigned, 32>& RegSet,
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unsigned Reg);
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bool delayHasHazard(MachineBasicBlock::iterator candidate,
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bool &sawLoad, bool &sawStore,
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SmallSet<unsigned, 32> &RegDefs,
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SmallSet<unsigned, 32> &RegUses);
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MachineBasicBlock::iterator
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findDelayInstr(MachineBasicBlock &MBB, MachineBasicBlock::iterator slot);
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};
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};
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char Filler::ID = 0;
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char Filler::ID = 0;
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} // end of anonymous namespace
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} // end of anonymous namespace
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/// runOnMachineBasicBlock - Fill in delay slots for the given basic block.
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/// runOnMachineBasicBlock - Fill in delay slots for the given basic block.
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/// Currently, we fill delay slots with NOPs. We assume there is only one
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/// We assume there is only one delay slot per delayed instruction.
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/// delay slot per delayed instruction.
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bool Filler::
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bool Filler::
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runOnMachineBasicBlock(MachineBasicBlock &MBB)
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runOnMachineBasicBlock(MachineBasicBlock &MBB) {
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{
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bool Changed = false;
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bool Changed = false;
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for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I) {
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for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I)
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const MCInstrDesc& MCid = I->getDesc();
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if (I->getDesc().hasDelaySlot()) {
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if (MCid.hasDelaySlot()) {
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MachineBasicBlock::iterator D = MBB.end();
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MachineBasicBlock::iterator J = I;
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MachineBasicBlock::iterator J = I;
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++J;
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BuildMI(MBB, J, I->getDebugLoc(), TII->get(Mips::NOP));
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if (EnableDelaySlotFiller)
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D = findDelayInstr(MBB, I);
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++FilledSlots;
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++FilledSlots;
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Changed = true;
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Changed = true;
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}
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}
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if (D == MBB.end())
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BuildMI(MBB, ++J, I->getDebugLoc(), TII->get(Mips::NOP));
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else
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MBB.splice(++J, &MBB, D);
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}
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return Changed;
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return Changed;
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}
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}
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/// createMipsDelaySlotFillerPass - Returns a pass that fills in delay
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/// createMipsDelaySlotFillerPass - Returns a pass that fills in delay
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@ -78,3 +115,155 @@ FunctionPass *llvm::createMipsDelaySlotFillerPass(MipsTargetMachine &tm) {
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return new Filler(tm);
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return new Filler(tm);
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}
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}
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MachineBasicBlock::iterator
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Filler::findDelayInstr(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator slot) {
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SmallSet<unsigned, 32> RegDefs;
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SmallSet<unsigned, 32> RegUses;
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bool sawLoad = false;
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bool sawStore = false;
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MachineBasicBlock::iterator I = slot;
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// Call's delay filler can def some of call's uses.
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if (slot->getDesc().isCall())
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insertCallUses(slot, RegDefs, RegUses);
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else
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insertDefsUses(slot, RegDefs, RegUses);
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bool done = false;
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while (!done) {
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done = (I == MBB.begin());
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if (!done)
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--I;
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// skip debug value
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if (I->isDebugValue())
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continue;
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if (I->hasUnmodeledSideEffects()
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|| I->isInlineAsm()
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|| I->isLabel()
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|| I->getDesc().hasDelaySlot()
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|| isDelayFiller(MBB, I)
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|| I->getDesc().isPseudo()
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//
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// Should not allow:
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// ERET, DERET or WAIT, PAUSE. Need to add these to instruction
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// list. TBD.
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)
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break;
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if (delayHasHazard(I, sawLoad, sawStore, RegDefs, RegUses)) {
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insertDefsUses(I, RegDefs, RegUses);
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continue;
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}
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return I;
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}
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return MBB.end();
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}
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bool Filler::delayHasHazard(MachineBasicBlock::iterator candidate,
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bool &sawLoad,
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bool &sawStore,
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SmallSet<unsigned, 32> &RegDefs,
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SmallSet<unsigned, 32> &RegUses) {
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if (candidate->isImplicitDef() || candidate->isKill())
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return true;
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if (candidate->getDesc().mayLoad()) {
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sawLoad = true;
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if (sawStore)
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return true;
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}
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if (candidate->getDesc().mayStore()) {
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if (sawStore)
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return true;
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sawStore = true;
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if (sawLoad)
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return true;
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}
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for (unsigned i = 0, e = candidate->getNumOperands(); i!= e; ++i) {
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const MachineOperand &MO = candidate->getOperand(i);
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if (!MO.isReg())
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continue; // skip
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unsigned Reg = MO.getReg();
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if (MO.isDef()) {
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// check whether Reg is defined or used before delay slot.
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if (IsRegInSet(RegDefs, Reg) || IsRegInSet(RegUses, Reg))
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return true;
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}
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if (MO.isUse()) {
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// check whether Reg is defined before delay slot.
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if (IsRegInSet(RegDefs, Reg))
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return true;
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}
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}
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return false;
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}
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void Filler::insertCallUses(MachineBasicBlock::iterator MI,
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SmallSet<unsigned, 32>& RegDefs,
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SmallSet<unsigned, 32>& RegUses) {
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switch(MI->getOpcode()) {
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default: llvm_unreachable("Unknown opcode.");
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case Mips::JAL:
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RegDefs.insert(31);
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break;
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case Mips::JALR:
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assert(MI->getNumOperands() >= 1);
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const MachineOperand &Reg = MI->getOperand(0);
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assert(Reg.isReg() && "JALR first operand is not a register.");
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RegUses.insert(Reg.getReg());
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RegDefs.insert(31);
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break;
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}
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}
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// Insert Defs and Uses of MI into the sets RegDefs and RegUses.
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void Filler::insertDefsUses(MachineBasicBlock::iterator MI,
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SmallSet<unsigned, 32>& RegDefs,
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SmallSet<unsigned, 32>& RegUses) {
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for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
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const MachineOperand &MO = MI->getOperand(i);
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if (!MO.isReg())
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continue;
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unsigned Reg = MO.getReg();
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if (Reg == 0)
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continue;
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if (MO.isDef())
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RegDefs.insert(Reg);
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if (MO.isUse())
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RegUses.insert(Reg);
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}
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}
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//returns true if the Reg or its alias is in the RegSet.
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bool Filler::IsRegInSet(SmallSet<unsigned, 32>& RegSet, unsigned Reg) {
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if (RegSet.count(Reg))
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return true;
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// check Aliased Registers
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for (const unsigned *Alias = TM.getRegisterInfo()->getAliasSet(Reg);
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*Alias; ++Alias)
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if (RegSet.count(*Alias))
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return true;
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return false;
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}
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// return true if the candidate is a delay filler.
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bool Filler::isDelayFiller(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator candidate) {
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if (candidate == MBB.begin())
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return false;
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const MCInstrDesc &prevdesc = (--candidate)->getDesc();
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return prevdesc.hasDelaySlot();
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}
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15
test/CodeGen/Mips/brdelayslot.ll
Normal file
15
test/CodeGen/Mips/brdelayslot.ll
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; RUN: llc -march=mipsel -enable-mips-delay-filler < %s | FileCheck %s
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define void @foo1() nounwind {
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entry:
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; CHECK: jalr
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; CHECK-NOT: nop
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; CHECK: jr
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; CHECK-NOT: nop
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; CHECK: .end
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tail call void @foo2(i32 3) nounwind
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ret void
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}
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declare void @foo2(i32)
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