2010-02-24 03:15:24 +08:00
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//===-- DelaySlotFiller.cpp - MBlaze delay slot filler --------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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2010-10-27 08:23:01 +08:00
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// A pass that attempts to fill instructions with delay slots. If no
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// instructions can be moved into the delay slot then a NOP is placed there.
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2010-02-24 03:15:24 +08:00
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "delay-slot-filler"
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#include "MBlaze.h"
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#include "MBlazeTargetMachine.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/Target/TargetInstrInfo.h"
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#include "llvm/ADT/Statistic.h"
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2010-10-21 11:57:26 +08:00
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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2010-02-24 03:15:24 +08:00
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using namespace llvm;
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STATISTIC(FilledSlots, "Number of delay slots filled");
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2010-12-07 05:11:01 +08:00
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namespace llvm {
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cl::opt<bool> DisableDelaySlotFiller(
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"disable-mblaze-delay-filler",
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cl::init(false),
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cl::desc("Disable the MBlaze delay slot filter."),
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cl::Hidden);
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}
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2010-02-24 03:15:24 +08:00
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namespace {
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struct Filler : public MachineFunctionPass {
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TargetMachine &TM;
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const TargetInstrInfo *TII;
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static char ID;
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2010-11-09 03:40:01 +08:00
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Filler(TargetMachine &tm)
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2010-08-07 02:33:48 +08:00
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: MachineFunctionPass(ID), TM(tm), TII(tm.getInstrInfo()) { }
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2010-02-24 03:15:24 +08:00
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virtual const char *getPassName() const {
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return "MBlaze Delay Slot Filler";
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}
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bool runOnMachineBasicBlock(MachineBasicBlock &MBB);
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bool runOnMachineFunction(MachineFunction &F) {
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bool Changed = false;
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for (MachineFunction::iterator FI = F.begin(), FE = F.end();
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FI != FE; ++FI)
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Changed |= runOnMachineBasicBlock(*FI);
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return Changed;
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}
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};
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char Filler::ID = 0;
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} // end of anonymous namespace
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2010-11-09 03:40:01 +08:00
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static bool hasImmInstruction(MachineBasicBlock::iterator &candidate) {
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2010-10-21 11:57:26 +08:00
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// Any instruction with an immediate mode operand greater than
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// 16-bits requires an implicit IMM instruction.
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unsigned numOper = candidate->getNumOperands();
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2010-11-09 03:40:01 +08:00
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for (unsigned op = 0; op < numOper; ++op) {
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2010-12-07 05:11:01 +08:00
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MachineOperand &mop = candidate->getOperand(op);
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// The operand requires more than 16-bits to represent.
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if (mop.isImm() && (mop.getImm() < -0x8000 || mop.getImm() > 0x7fff))
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return true;
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// We must assume that unknown immediate values require more than
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// 16-bits to represent.
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if (mop.isGlobal() || mop.isSymbol())
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return true;
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2010-10-21 11:57:26 +08:00
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// FIXME: we could probably check to see if the FP value happens
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// to not need an IMM instruction. For now we just always
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2010-12-07 05:11:01 +08:00
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// assume that FP values do.
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if (mop.isFPImm())
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return true;
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2010-10-21 11:57:26 +08:00
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}
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return false;
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}
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2010-12-22 08:22:59 +08:00
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static unsigned getLastRealOperand(MachineBasicBlock::iterator &instr) {
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switch (instr->getOpcode()) {
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default: return instr->getNumOperands();
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// These instructions have a variable number of operands but the first two
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// are the "real" operands that we care about during hazard detection.
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case MBlaze::BRLID:
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case MBlaze::BRALID:
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case MBlaze::BRLD:
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case MBlaze::BRALD:
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return 2;
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}
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}
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2010-11-09 03:40:01 +08:00
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static bool delayHasHazard(MachineBasicBlock::iterator &candidate,
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MachineBasicBlock::iterator &slot) {
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// Hazard check
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MachineBasicBlock::iterator a = candidate;
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MachineBasicBlock::iterator b = slot;
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TargetInstrDesc desc = candidate->getDesc();
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// MBB layout:-
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// candidate := a0 = operation(a1, a2)
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// ...middle bit...
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// slot := b0 = operation(b1, b2)
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// Possible hazards:-/
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// 1. a1 or a2 was written during the middle bit
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// 2. a0 was read or written during the middle bit
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// 3. a0 is one or more of {b0, b1, b2}
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// 4. b0 is one or more of {a1, a2}
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// 5. a accesses memory, and the middle bit
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// contains a store operation.
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bool a_is_memory = desc.mayLoad() || desc.mayStore();
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2010-12-22 08:22:59 +08:00
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// Determine the number of operands in the slot instruction and in the
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// candidate instruction.
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const unsigned aend = getLastRealOperand(a);
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const unsigned bend = getLastRealOperand(b);
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2010-12-07 05:11:01 +08:00
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// Check hazards type 1, 2 and 5 by scanning the middle bit
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MachineBasicBlock::iterator m = a;
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for (++m; m != b; ++m) {
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2010-12-22 08:22:59 +08:00
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for (unsigned aop = 0; aop<aend; ++aop) {
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2010-12-07 05:11:01 +08:00
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bool aop_is_reg = a->getOperand(aop).isReg();
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if (!aop_is_reg) continue;
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bool aop_is_def = a->getOperand(aop).isDef();
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unsigned aop_reg = a->getOperand(aop).getReg();
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2010-12-22 08:22:59 +08:00
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const unsigned mend = getLastRealOperand(m);
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for (unsigned mop = 0; mop<mend; ++mop) {
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2010-12-07 05:11:01 +08:00
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bool mop_is_reg = m->getOperand(mop).isReg();
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if (!mop_is_reg) continue;
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bool mop_is_def = m->getOperand(mop).isDef();
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unsigned mop_reg = m->getOperand(mop).getReg();
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if (aop_is_def && (mop_reg == aop_reg))
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return true; // Hazard type 2, because aop = a0
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else if (mop_is_def && (mop_reg == aop_reg))
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return true; // Hazard type 1, because aop in {a1, a2}
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}
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2010-10-21 11:57:26 +08:00
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}
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2010-12-07 05:11:01 +08:00
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// Check hazard type 5
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if (a_is_memory && m->getDesc().mayStore())
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return true;
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}
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// Check hazard type 3 & 4
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2010-12-22 08:22:59 +08:00
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for (unsigned aop = 0; aop<aend; ++aop) {
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2010-12-07 05:11:01 +08:00
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if (a->getOperand(aop).isReg()) {
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unsigned aop_reg = a->getOperand(aop).getReg();
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2010-10-21 11:57:26 +08:00
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2010-12-22 08:22:59 +08:00
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for (unsigned bop = 0; bop<bend; ++bop) {
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if (b->getOperand(bop).isReg() && !b->getOperand(bop).isImplicit()) {
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2010-12-07 05:11:01 +08:00
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unsigned bop_reg = b->getOperand(bop).getReg();
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if (aop_reg == bop_reg)
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return true;
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2010-10-21 11:57:26 +08:00
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}
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2010-12-07 05:11:01 +08:00
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}
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}
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2010-10-21 11:57:26 +08:00
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}
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return false;
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}
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2010-11-22 05:36:12 +08:00
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static bool 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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TargetInstrDesc brdesc = (--candidate)->getDesc();
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return (brdesc.hasDelaySlot());
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}
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2010-12-13 06:22:49 +08:00
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static bool hasUnknownSideEffects(MachineBasicBlock::iterator &I,
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TargetInstrDesc &desc) {
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if (!desc.hasUnmodeledSideEffects())
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return false;
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unsigned op = I->getOpcode();
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if (op == MBlaze::ADDK || op == MBlaze::ADDIK ||
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op == MBlaze::ADDC || op == MBlaze::ADDIC ||
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op == MBlaze::ADDKC || op == MBlaze::ADDIKC ||
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op == MBlaze::RSUBK || op == MBlaze::RSUBIK ||
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op == MBlaze::RSUBC || op == MBlaze::RSUBIC ||
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op == MBlaze::RSUBKC || op == MBlaze::RSUBIKC)
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return false;
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return true;
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}
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2010-10-21 11:57:26 +08:00
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static MachineBasicBlock::iterator
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2010-11-22 05:36:12 +08:00
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findDelayInstr(MachineBasicBlock &MBB,MachineBasicBlock::iterator slot) {
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MachineBasicBlock::iterator I = slot;
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while (true) {
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if (I == MBB.begin())
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break;
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--I;
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TargetInstrDesc desc = I->getDesc();
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2010-12-07 05:11:01 +08:00
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if (desc.hasDelaySlot() || desc.isBranch() || isDelayFiller(MBB,I) ||
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desc.isCall() || desc.isReturn() || desc.isBarrier() ||
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2010-12-13 06:22:49 +08:00
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hasUnknownSideEffects(I,desc))
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2010-11-22 05:36:12 +08:00
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break;
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2010-12-07 05:11:01 +08:00
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if (hasImmInstruction(I) || delayHasHazard(I,slot))
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2010-11-22 05:36:12 +08:00
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continue;
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return I;
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2010-10-21 11:57:26 +08:00
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}
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2010-11-22 05:36:12 +08:00
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return MBB.end();
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2010-10-21 11:57:26 +08:00
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}
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2010-02-24 03:15:24 +08:00
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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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/// delay slot per delayed instruction.
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bool Filler::runOnMachineBasicBlock(MachineBasicBlock &MBB) {
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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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if (I->getDesc().hasDelaySlot()) {
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2010-12-07 05:11:01 +08:00
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MachineBasicBlock::iterator D = MBB.end();
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2010-11-22 05:36:12 +08:00
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MachineBasicBlock::iterator J = I;
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2010-10-21 11:57:26 +08:00
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2010-12-07 05:11:01 +08:00
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if (!DisableDelaySlotFiller)
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D = findDelayInstr(MBB,I);
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2010-02-24 03:15:24 +08:00
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++FilledSlots;
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Changed = true;
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2010-10-21 11:57:26 +08:00
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2010-11-09 03:40:01 +08:00
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if (D == MBB.end())
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2010-11-22 05:36:12 +08:00
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BuildMI(MBB, ++J, I->getDebugLoc(), TII->get(MBlaze::NOP));
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2010-10-21 11:57:26 +08:00
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else
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2010-11-22 05:36:12 +08:00
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MBB.splice(++J, &MBB, D);
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2010-02-24 03:15:24 +08:00
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}
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return Changed;
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}
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/// createMBlazeDelaySlotFillerPass - Returns a pass that fills in delay
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/// slots in MBlaze MachineFunctions
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FunctionPass *llvm::createMBlazeDelaySlotFillerPass(MBlazeTargetMachine &tm) {
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return new Filler(tm);
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}
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