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			712 lines
		
	
	
		
			24 KiB
		
	
	
	
		
			C++
		
	
	
	
| //=== A15SDOptimizerPass.cpp - Optimize DPR and SPR register accesses on A15==//
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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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| // The Cortex-A15 processor employs a tracking scheme in its register renaming
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| // in order to process each instruction's micro-ops speculatively and
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| // out-of-order with appropriate forwarding. The ARM architecture allows VFP
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| // instructions to read and write 32-bit S-registers.  Each S-register
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| // corresponds to one half (upper or lower) of an overlaid 64-bit D-register.
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| //
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| // There are several instruction patterns which can be used to provide this
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| // capability which can provide higher performance than other, potentially more
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| // direct patterns, specifically around when one micro-op reads a D-register
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| // operand that has recently been written as one or more S-register results.
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| //
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| // This file defines a pre-regalloc pass which looks for SPR producers which
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| // are going to be used by a DPR (or QPR) consumers and creates the more
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| // optimized access pattern.
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| //
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| //===----------------------------------------------------------------------===//
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| 
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| #define DEBUG_TYPE "a15-sd-optimizer"
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| #include "ARM.h"
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| #include "ARMBaseInstrInfo.h"
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| #include "ARMSubtarget.h"
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| #include "ARMISelLowering.h"
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| #include "ARMTargetMachine.h"
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| 
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| #include "llvm/ADT/SmallPtrSet.h"
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| #include "llvm/ADT/Statistic.h"
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| #include "llvm/CodeGen/MachineFunctionPass.h"
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| #include "llvm/CodeGen/MachineInstr.h"
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| #include "llvm/CodeGen/MachineInstrBuilder.h"
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| #include "llvm/CodeGen/MachineRegisterInfo.h"
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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/raw_ostream.h"
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| #include "llvm/Target/TargetRegisterInfo.h"
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| 
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| #include <set>
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| 
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| using namespace llvm;
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| 
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| namespace {
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|   struct A15SDOptimizer : public MachineFunctionPass {
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|     static char ID;
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|     A15SDOptimizer() : MachineFunctionPass(ID) {}
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| 
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|     virtual bool runOnMachineFunction(MachineFunction &Fn);
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| 
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|     virtual const char *getPassName() const {
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|       return "ARM A15 S->D optimizer";
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|     }
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| 
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|   private:
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|     const ARMBaseInstrInfo *TII;
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|     const TargetRegisterInfo *TRI;
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|     MachineRegisterInfo *MRI;
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| 
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|     bool runOnInstruction(MachineInstr *MI);
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| 
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|     //
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|     // Instruction builder helpers
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|     //
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|     unsigned createDupLane(MachineBasicBlock &MBB,
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|                            MachineBasicBlock::iterator InsertBefore,
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|                            DebugLoc DL,
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|                            unsigned Reg, unsigned Lane,
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|                            bool QPR=false);
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| 
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|     unsigned createExtractSubreg(MachineBasicBlock &MBB,
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|                                  MachineBasicBlock::iterator InsertBefore,
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|                                  DebugLoc DL,
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|                                  unsigned DReg, unsigned Lane,
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|                                  const TargetRegisterClass *TRC);
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| 
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|     unsigned createVExt(MachineBasicBlock &MBB,
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|                         MachineBasicBlock::iterator InsertBefore,
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|                         DebugLoc DL,
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|                         unsigned Ssub0, unsigned Ssub1);
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| 
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|     unsigned createRegSequence(MachineBasicBlock &MBB,
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|                                MachineBasicBlock::iterator InsertBefore,
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|                                DebugLoc DL,
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|                                unsigned Reg1, unsigned Reg2);
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| 
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|     unsigned createInsertSubreg(MachineBasicBlock &MBB,
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|                                 MachineBasicBlock::iterator InsertBefore,
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|                                 DebugLoc DL, unsigned DReg, unsigned Lane,
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|                                 unsigned ToInsert);
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| 
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|     unsigned createImplicitDef(MachineBasicBlock &MBB,
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|                                MachineBasicBlock::iterator InsertBefore,
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|                                DebugLoc DL);
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|     
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|     //
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|     // Various property checkers
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|     //
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|     bool usesRegClass(MachineOperand &MO, const TargetRegisterClass *TRC);
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|     bool hasPartialWrite(MachineInstr *MI);
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|     SmallVector<unsigned, 8> getReadDPRs(MachineInstr *MI);
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|     unsigned getDPRLaneFromSPR(unsigned SReg);
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| 
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|     //
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|     // Methods used for getting the definitions of partial registers
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|     //
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| 
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|     MachineInstr *elideCopies(MachineInstr *MI);
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|     void elideCopiesAndPHIs(MachineInstr *MI,
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|                             SmallVectorImpl<MachineInstr*> &Outs);
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| 
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|     //
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|     // Pattern optimization methods
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|     //
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|     unsigned optimizeAllLanesPattern(MachineInstr *MI, unsigned Reg);
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|     unsigned optimizeSDPattern(MachineInstr *MI);
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|     unsigned getPrefSPRLane(unsigned SReg);
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| 
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|     //
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|     // Sanitizing method - used to make sure if don't leave dead code around.
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|     //
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|     void eraseInstrWithNoUses(MachineInstr *MI);
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| 
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|     //
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|     // A map used to track the changes done by this pass.
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|     //
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|     std::map<MachineInstr*, unsigned> Replacements;
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|     std::set<MachineInstr *> DeadInstr;
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|   };
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|   char A15SDOptimizer::ID = 0;
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| } // end anonymous namespace
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| 
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| // Returns true if this is a use of a SPR register.
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| bool A15SDOptimizer::usesRegClass(MachineOperand &MO,
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|                                   const TargetRegisterClass *TRC) {
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|   if (!MO.isReg())
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|     return false;
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|   unsigned Reg = MO.getReg();
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| 
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|   if (TargetRegisterInfo::isVirtualRegister(Reg))
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|     return MRI->getRegClass(Reg)->hasSuperClassEq(TRC);
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|   else
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|     return TRC->contains(Reg);
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| }
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| 
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| unsigned A15SDOptimizer::getDPRLaneFromSPR(unsigned SReg) {
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|   unsigned DReg = TRI->getMatchingSuperReg(SReg, ARM::ssub_1,
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|                                            &ARM::DPRRegClass);
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|   if (DReg != ARM::NoRegister) return ARM::ssub_1;
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|   return ARM::ssub_0;
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| }
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| 
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| // Get the subreg type that is most likely to be coalesced
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| // for an SPR register that will be used in VDUP32d pseudo.
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| unsigned A15SDOptimizer::getPrefSPRLane(unsigned SReg) {
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|   if (!TRI->isVirtualRegister(SReg))
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|     return getDPRLaneFromSPR(SReg);
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| 
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|   MachineInstr *MI = MRI->getVRegDef(SReg);
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|   if (!MI) return ARM::ssub_0;
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|   MachineOperand *MO = MI->findRegisterDefOperand(SReg);
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| 
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|   assert(MO->isReg() && "Non register operand found!");
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|   if (!MO) return ARM::ssub_0;
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| 
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|   if (MI->isCopy() && usesRegClass(MI->getOperand(1),
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|                                     &ARM::SPRRegClass)) {
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|     SReg = MI->getOperand(1).getReg();
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|   }
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| 
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|   if (TargetRegisterInfo::isVirtualRegister(SReg)) {
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|     if (MO->getSubReg() == ARM::ssub_1) return ARM::ssub_1;
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|     return ARM::ssub_0;
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|   }
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|   return getDPRLaneFromSPR(SReg);
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| }
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| 
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| // MI is known to be dead. Figure out what instructions
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| // are also made dead by this and mark them for removal.
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| void A15SDOptimizer::eraseInstrWithNoUses(MachineInstr *MI) {
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|   SmallVector<MachineInstr *, 8> Front;
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|   DeadInstr.insert(MI);
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| 
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|   DEBUG(dbgs() << "Deleting base instruction " << *MI << "\n");
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|   Front.push_back(MI);
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| 
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|   while (Front.size() != 0) {
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|     MI = Front.back();
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|     Front.pop_back();
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| 
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|     // MI is already known to be dead. We need to see
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|     // if other instructions can also be removed.
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|     for (unsigned int i = 0; i < MI->getNumOperands(); ++i) {
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|       MachineOperand &MO = MI->getOperand(i);
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|       if ((!MO.isReg()) || (!MO.isUse()))
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|         continue;
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|       unsigned Reg = MO.getReg();
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|       if (!TRI->isVirtualRegister(Reg))
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|         continue;
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|       MachineOperand *Op = MI->findRegisterDefOperand(Reg);
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| 
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|       if (!Op)
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|         continue;
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| 
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|       MachineInstr *Def = Op->getParent();
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| 
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|       // We don't need to do anything if we have already marked
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|       // this instruction as being dead.
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|       if (DeadInstr.find(Def) != DeadInstr.end())
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|         continue;
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| 
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|       // Check if all the uses of this instruction are marked as
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|       // dead. If so, we can also mark this instruction as being
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|       // dead.
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|       bool IsDead = true;
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|       for (unsigned int j = 0; j < Def->getNumOperands(); ++j) {
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|         MachineOperand &MODef = Def->getOperand(j);
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|         if ((!MODef.isReg()) || (!MODef.isDef()))
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|           continue;
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|         unsigned DefReg = MODef.getReg();
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|         if (!TRI->isVirtualRegister(DefReg)) {
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|           IsDead = false;
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|           break;
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|         }
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|         for (MachineRegisterInfo::use_iterator II = MRI->use_begin(Reg),
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|                             EE = MRI->use_end();
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|                             II != EE; ++II) {
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|           // We don't care about self references.
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|           if (&*II == Def)
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|             continue;
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|           if (DeadInstr.find(&*II) == DeadInstr.end()) {
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|             IsDead = false;
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|             break;
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|           }
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|         }
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|       }
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| 
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|       if (!IsDead) continue;
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| 
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|       DEBUG(dbgs() << "Deleting instruction " << *Def << "\n");
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|       DeadInstr.insert(Def);
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|     }
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|   }
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| }
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| 
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| // Creates the more optimized patterns and generally does all the code
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| // transformations in this pass.
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| unsigned A15SDOptimizer::optimizeSDPattern(MachineInstr *MI) {
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|   if (MI->isCopy()) {
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|     return optimizeAllLanesPattern(MI, MI->getOperand(1).getReg());
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|   }
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| 
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|   if (MI->isInsertSubreg()) {
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|     unsigned DPRReg = MI->getOperand(1).getReg();
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|     unsigned SPRReg = MI->getOperand(2).getReg();
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| 
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|     if (TRI->isVirtualRegister(DPRReg) && TRI->isVirtualRegister(SPRReg)) {
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|       MachineInstr *DPRMI = MRI->getVRegDef(MI->getOperand(1).getReg());
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|       MachineInstr *SPRMI = MRI->getVRegDef(MI->getOperand(2).getReg());
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| 
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|       if (DPRMI && SPRMI) {
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|         // See if the first operand of this insert_subreg is IMPLICIT_DEF
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|         MachineInstr *ECDef = elideCopies(DPRMI);
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|         if (ECDef != 0 && ECDef->isImplicitDef()) {
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|           // Another corner case - if we're inserting something that is purely
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|           // a subreg copy of a DPR, just use that DPR.
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| 
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|           MachineInstr *EC = elideCopies(SPRMI);
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|           // Is it a subreg copy of ssub_0?
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|           if (EC && EC->isCopy() &&
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|               EC->getOperand(1).getSubReg() == ARM::ssub_0) {
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|             DEBUG(dbgs() << "Found a subreg copy: " << *SPRMI);
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| 
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|             // Find the thing we're subreg copying out of - is it of the same
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|             // regclass as DPRMI? (i.e. a DPR or QPR).
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|             unsigned FullReg = SPRMI->getOperand(1).getReg();
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|             const TargetRegisterClass *TRC =
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|               MRI->getRegClass(MI->getOperand(1).getReg());
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|             if (TRC->hasSuperClassEq(MRI->getRegClass(FullReg))) {
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|               DEBUG(dbgs() << "Subreg copy is compatible - returning ");
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|               DEBUG(dbgs() << PrintReg(FullReg) << "\n");
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|               eraseInstrWithNoUses(MI);
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|               return FullReg;
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|             }
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|           }
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| 
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|           return optimizeAllLanesPattern(MI, MI->getOperand(2).getReg());
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|         }
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|       }
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|     }
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|     return optimizeAllLanesPattern(MI, MI->getOperand(0).getReg());
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|   }
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| 
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|   if (MI->isRegSequence() && usesRegClass(MI->getOperand(1),
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|                                           &ARM::SPRRegClass)) {
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|     // See if all bar one of the operands are IMPLICIT_DEF and insert the
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|     // optimizer pattern accordingly.
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|     unsigned NumImplicit = 0, NumTotal = 0;
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|     unsigned NonImplicitReg = ~0U;
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| 
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|     for (unsigned I = 1; I < MI->getNumExplicitOperands(); ++I) {
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|       if (!MI->getOperand(I).isReg())
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|         continue;
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|       ++NumTotal;
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|       unsigned OpReg = MI->getOperand(I).getReg();
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| 
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|       if (!TRI->isVirtualRegister(OpReg))
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|         break;
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| 
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|       MachineInstr *Def = MRI->getVRegDef(OpReg);
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|       if (!Def)
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|         break;
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|       if (Def->isImplicitDef())
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|         ++NumImplicit;
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|       else
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|         NonImplicitReg = MI->getOperand(I).getReg();
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|     }
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| 
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|     if (NumImplicit == NumTotal - 1)
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|       return optimizeAllLanesPattern(MI, NonImplicitReg);
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|     else
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|       return optimizeAllLanesPattern(MI, MI->getOperand(0).getReg());
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|   }
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| 
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|   assert(0 && "Unhandled update pattern!");
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|   return 0;
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| }
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| 
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| // Return true if this MachineInstr inserts a scalar (SPR) value into
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| // a D or Q register.
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| bool A15SDOptimizer::hasPartialWrite(MachineInstr *MI) {
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|   // The only way we can do a partial register update is through a COPY,
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|   // INSERT_SUBREG or REG_SEQUENCE.
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|   if (MI->isCopy() && usesRegClass(MI->getOperand(1), &ARM::SPRRegClass))
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|     return true;
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| 
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|   if (MI->isInsertSubreg() && usesRegClass(MI->getOperand(2),
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|                                            &ARM::SPRRegClass))
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|     return true;
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| 
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|   if (MI->isRegSequence() && usesRegClass(MI->getOperand(1), &ARM::SPRRegClass))
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|     return true;
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| 
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|   return false;
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| }
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| 
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| // Looks through full copies to get the instruction that defines the input
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| // operand for MI.
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| MachineInstr *A15SDOptimizer::elideCopies(MachineInstr *MI) {
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|   if (!MI->isFullCopy())
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|     return MI;
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|   if (!TRI->isVirtualRegister(MI->getOperand(1).getReg()))
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|     return NULL;
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|   MachineInstr *Def = MRI->getVRegDef(MI->getOperand(1).getReg());
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|   if (!Def)
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|     return NULL;
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|   return elideCopies(Def);
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| }
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| 
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| // Look through full copies and PHIs to get the set of non-copy MachineInstrs
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| // that can produce MI.
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| void A15SDOptimizer::elideCopiesAndPHIs(MachineInstr *MI,
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|                                         SmallVectorImpl<MachineInstr*> &Outs) {
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|    // Looking through PHIs may create loops so we need to track what
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|    // instructions we have visited before.
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|    std::set<MachineInstr *> Reached;
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|    SmallVector<MachineInstr *, 8> Front;
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|    Front.push_back(MI);
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|    while (Front.size() != 0) {
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|      MI = Front.back();
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|      Front.pop_back();
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| 
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|      // If we have already explored this MachineInstr, ignore it.
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|      if (Reached.find(MI) != Reached.end())
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|        continue;
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|      Reached.insert(MI);
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|      if (MI->isPHI()) {
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|        for (unsigned I = 1, E = MI->getNumOperands(); I != E; I += 2) {
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|          unsigned Reg = MI->getOperand(I).getReg();
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|          if (!TRI->isVirtualRegister(Reg)) {
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|            continue;
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|          }
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|          MachineInstr *NewMI = MRI->getVRegDef(Reg);
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|          if (!NewMI)
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|            continue;
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|          Front.push_back(NewMI);
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|        }
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|      } else if (MI->isFullCopy()) {
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|        if (!TRI->isVirtualRegister(MI->getOperand(1).getReg()))
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|          continue;
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|        MachineInstr *NewMI = MRI->getVRegDef(MI->getOperand(1).getReg());
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|        if (!NewMI)
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|          continue;
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|        Front.push_back(NewMI);
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|      } else {
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|        DEBUG(dbgs() << "Found partial copy" << *MI <<"\n");
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|        Outs.push_back(MI);
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|      }
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|    }
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| }
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| 
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| // Return the DPR virtual registers that are read by this machine instruction
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| // (if any).
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| SmallVector<unsigned, 8> A15SDOptimizer::getReadDPRs(MachineInstr *MI) {
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|   if (MI->isCopyLike() || MI->isInsertSubreg() || MI->isRegSequence() ||
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|       MI->isKill())
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|     return SmallVector<unsigned, 8>();
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| 
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|   SmallVector<unsigned, 8> Defs;
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|   for (unsigned i = 0; i < MI->getNumOperands(); ++i) {
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|     MachineOperand &MO = MI->getOperand(i);
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| 
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|     if (!MO.isReg() || !MO.isUse())
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|       continue;
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|     if (!usesRegClass(MO, &ARM::DPRRegClass) &&
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|         !usesRegClass(MO, &ARM::QPRRegClass))
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|       continue;
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| 
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|     Defs.push_back(MO.getReg());
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|   }
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|   return Defs;
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| }
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| 
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| // Creates a DPR register from an SPR one by using a VDUP.
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| unsigned
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| A15SDOptimizer::createDupLane(MachineBasicBlock &MBB,
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|                               MachineBasicBlock::iterator InsertBefore,
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|                               DebugLoc DL,
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|                               unsigned Reg, unsigned Lane, bool QPR) {
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|   unsigned Out = MRI->createVirtualRegister(QPR ? &ARM::QPRRegClass :
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|                                                   &ARM::DPRRegClass);
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|   AddDefaultPred(BuildMI(MBB,
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|                          InsertBefore,
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|                          DL,
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|                          TII->get(QPR ? ARM::VDUPLN32q : ARM::VDUPLN32d),
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|                          Out)
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|                    .addReg(Reg)
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|                    .addImm(Lane));
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|  
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|   return Out;
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| }
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| 
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| // Creates a SPR register from a DPR by copying the value in lane 0.
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| unsigned
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| A15SDOptimizer::createExtractSubreg(MachineBasicBlock &MBB,
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|                                     MachineBasicBlock::iterator InsertBefore,
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|                                     DebugLoc DL,
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|                                     unsigned DReg, unsigned Lane,
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|                                     const TargetRegisterClass *TRC) {
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|   unsigned Out = MRI->createVirtualRegister(TRC);
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|   BuildMI(MBB,
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|           InsertBefore,
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|           DL,
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|           TII->get(TargetOpcode::COPY), Out)
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|     .addReg(DReg, 0, Lane);
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| 
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|   return Out;
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| }
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| 
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| // Takes two SPR registers and creates a DPR by using a REG_SEQUENCE.
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| unsigned
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| A15SDOptimizer::createRegSequence(MachineBasicBlock &MBB,
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|                                   MachineBasicBlock::iterator InsertBefore,
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|                                   DebugLoc DL,
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|                                   unsigned Reg1, unsigned Reg2) {
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|   unsigned Out = MRI->createVirtualRegister(&ARM::QPRRegClass);
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|   BuildMI(MBB,
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|           InsertBefore,
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|           DL,
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|           TII->get(TargetOpcode::REG_SEQUENCE), Out)
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|     .addReg(Reg1)
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|     .addImm(ARM::dsub_0)
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|     .addReg(Reg2)
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|     .addImm(ARM::dsub_1);
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|   return Out;
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| }
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| 
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| // Takes two DPR registers that have previously been VDUPed (Ssub0 and Ssub1)
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| // and merges them into one DPR register.
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| unsigned
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| A15SDOptimizer::createVExt(MachineBasicBlock &MBB,
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|                            MachineBasicBlock::iterator InsertBefore,
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|                            DebugLoc DL,
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|                            unsigned Ssub0, unsigned Ssub1) {
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|   unsigned Out = MRI->createVirtualRegister(&ARM::DPRRegClass);
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|   AddDefaultPred(BuildMI(MBB,
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|                          InsertBefore,
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|                          DL,
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|                          TII->get(ARM::VEXTd32), Out)
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|                    .addReg(Ssub0)
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|                    .addReg(Ssub1)
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|                    .addImm(1));
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|   return Out;
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| }
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| 
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| unsigned
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| A15SDOptimizer::createInsertSubreg(MachineBasicBlock &MBB,
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|                                    MachineBasicBlock::iterator InsertBefore,
 | |
|                                    DebugLoc DL, unsigned DReg, unsigned Lane,
 | |
|                                    unsigned ToInsert) {
 | |
|   unsigned Out = MRI->createVirtualRegister(&ARM::DPR_VFP2RegClass);
 | |
|   BuildMI(MBB,
 | |
|           InsertBefore,
 | |
|           DL,
 | |
|           TII->get(TargetOpcode::INSERT_SUBREG), Out)
 | |
|     .addReg(DReg)
 | |
|     .addReg(ToInsert)
 | |
|     .addImm(Lane);
 | |
| 
 | |
|   return Out;
 | |
| }
 | |
| 
 | |
| unsigned
 | |
| A15SDOptimizer::createImplicitDef(MachineBasicBlock &MBB,
 | |
|                                   MachineBasicBlock::iterator InsertBefore,
 | |
|                                   DebugLoc DL) {
 | |
|   unsigned Out = MRI->createVirtualRegister(&ARM::DPRRegClass);
 | |
|   BuildMI(MBB,
 | |
|           InsertBefore,
 | |
|           DL,
 | |
|           TII->get(TargetOpcode::IMPLICIT_DEF), Out);
 | |
|   return Out;
 | |
| }
 | |
| 
 | |
| // This function inserts instructions in order to optimize interactions between
 | |
| // SPR registers and DPR/QPR registers. It does so by performing VDUPs on all
 | |
| // lanes, and the using VEXT instructions to recompose the result.
 | |
| unsigned
 | |
| A15SDOptimizer::optimizeAllLanesPattern(MachineInstr *MI, unsigned Reg) {
 | |
|   MachineBasicBlock::iterator InsertPt(MI);
 | |
|   DebugLoc DL = MI->getDebugLoc();
 | |
|   MachineBasicBlock &MBB = *MI->getParent();
 | |
|   InsertPt++;
 | |
|   unsigned Out;
 | |
| 
 | |
|   if (MRI->getRegClass(Reg)->hasSuperClassEq(&ARM::QPRRegClass)) {
 | |
|     unsigned DSub0 = createExtractSubreg(MBB, InsertPt, DL, Reg,
 | |
|                                          ARM::dsub_0, &ARM::DPRRegClass);
 | |
|     unsigned DSub1 = createExtractSubreg(MBB, InsertPt, DL, Reg,
 | |
|                                          ARM::dsub_1, &ARM::DPRRegClass);
 | |
| 
 | |
|     unsigned Out1 = createDupLane(MBB, InsertPt, DL, DSub0, 0);
 | |
|     unsigned Out2 = createDupLane(MBB, InsertPt, DL, DSub0, 1);
 | |
|     Out = createVExt(MBB, InsertPt, DL, Out1, Out2);
 | |
| 
 | |
|     unsigned Out3 = createDupLane(MBB, InsertPt, DL, DSub1, 0);
 | |
|     unsigned Out4 = createDupLane(MBB, InsertPt, DL, DSub1, 1);
 | |
|     Out2 = createVExt(MBB, InsertPt, DL, Out3, Out4);
 | |
| 
 | |
|     Out = createRegSequence(MBB, InsertPt, DL, Out, Out2);
 | |
| 
 | |
|   } else if (MRI->getRegClass(Reg)->hasSuperClassEq(&ARM::DPRRegClass)) {
 | |
|     unsigned Out1 = createDupLane(MBB, InsertPt, DL, Reg, 0);
 | |
|     unsigned Out2 = createDupLane(MBB, InsertPt, DL, Reg, 1);
 | |
|     Out = createVExt(MBB, InsertPt, DL, Out1, Out2);
 | |
| 
 | |
|   } else {
 | |
|     assert(MRI->getRegClass(Reg)->hasSuperClassEq(&ARM::SPRRegClass) &&
 | |
|            "Found unexpected regclass!");
 | |
| 
 | |
|     unsigned PrefLane = getPrefSPRLane(Reg);
 | |
|     unsigned Lane;
 | |
|     switch (PrefLane) {
 | |
|       case ARM::ssub_0: Lane = 0; break;
 | |
|       case ARM::ssub_1: Lane = 1; break;
 | |
|       default: llvm_unreachable("Unknown preferred lane!");
 | |
|     }
 | |
| 
 | |
|     bool UsesQPR = usesRegClass(MI->getOperand(0), &ARM::QPRRegClass);
 | |
| 
 | |
|     Out = createImplicitDef(MBB, InsertPt, DL);
 | |
|     Out = createInsertSubreg(MBB, InsertPt, DL, Out, PrefLane, Reg);
 | |
|     Out = createDupLane(MBB, InsertPt, DL, Out, Lane, UsesQPR);
 | |
|     eraseInstrWithNoUses(MI);
 | |
|   }
 | |
|   return Out;
 | |
| }
 | |
| 
 | |
| bool A15SDOptimizer::runOnInstruction(MachineInstr *MI) {
 | |
|   // We look for instructions that write S registers that are then read as
 | |
|   // D/Q registers. These can only be caused by COPY, INSERT_SUBREG and
 | |
|   // REG_SEQUENCE pseudos that insert an SPR value into a DPR register or
 | |
|   // merge two SPR values to form a DPR register.  In order avoid false
 | |
|   // positives we make sure that there is an SPR producer so we look past
 | |
|   // COPY and PHI nodes to find it.
 | |
|   //
 | |
|   // The best code pattern for when an SPR producer is going to be used by a
 | |
|   // DPR or QPR consumer depends on whether the other lanes of the
 | |
|   // corresponding DPR/QPR are currently defined.
 | |
|   //
 | |
|   // We can handle these efficiently, depending on the type of
 | |
|   // pseudo-instruction that is producing the pattern
 | |
|   //
 | |
|   //   * COPY:          * VDUP all lanes and merge the results together
 | |
|   //                      using VEXTs.
 | |
|   //
 | |
|   //   * INSERT_SUBREG: * If the SPR value was originally in another DPR/QPR
 | |
|   //                      lane, and the other lane(s) of the DPR/QPR register
 | |
|   //                      that we are inserting in are undefined, use the
 | |
|   //                      original DPR/QPR value. 
 | |
|   //                    * Otherwise, fall back on the same stategy as COPY.
 | |
|   //
 | |
|   //   * REG_SEQUENCE:  * If all except one of the input operands are
 | |
|   //                      IMPLICIT_DEFs, insert the VDUP pattern for just the
 | |
|   //                      defined input operand
 | |
|   //                    * Otherwise, fall back on the same stategy as COPY.
 | |
|   //
 | |
| 
 | |
|   // First, get all the reads of D-registers done by this instruction.
 | |
|   SmallVector<unsigned, 8> Defs = getReadDPRs(MI);
 | |
|   bool Modified = false;
 | |
| 
 | |
|   for (SmallVectorImpl<unsigned>::iterator I = Defs.begin(), E = Defs.end();
 | |
|      I != E; ++I) {
 | |
|     // Follow the def-use chain for this DPR through COPYs, and also through
 | |
|     // PHIs (which are essentially multi-way COPYs). It is because of PHIs that
 | |
|     // we can end up with multiple defs of this DPR.
 | |
| 
 | |
|     SmallVector<MachineInstr *, 8> DefSrcs;
 | |
|     if (!TRI->isVirtualRegister(*I))
 | |
|       continue;
 | |
|     MachineInstr *Def = MRI->getVRegDef(*I);
 | |
|     if (!Def)
 | |
|       continue;
 | |
| 
 | |
|     elideCopiesAndPHIs(Def, DefSrcs);
 | |
| 
 | |
|     for (SmallVectorImpl<MachineInstr *>::iterator II = DefSrcs.begin(),
 | |
|       EE = DefSrcs.end(); II != EE; ++II) {
 | |
|       MachineInstr *MI = *II;
 | |
| 
 | |
|       // If we've already analyzed and replaced this operand, don't do
 | |
|       // anything.
 | |
|       if (Replacements.find(MI) != Replacements.end())
 | |
|         continue;
 | |
| 
 | |
|       // Now, work out if the instruction causes a SPR->DPR dependency.
 | |
|       if (!hasPartialWrite(MI))
 | |
|         continue;
 | |
| 
 | |
|       // Collect all the uses of this MI's DPR def for updating later.
 | |
|       SmallVector<MachineOperand*, 8> Uses;
 | |
|       unsigned DPRDefReg = MI->getOperand(0).getReg();
 | |
|       for (MachineRegisterInfo::use_iterator I = MRI->use_begin(DPRDefReg),
 | |
|              E = MRI->use_end(); I != E; ++I)
 | |
|         Uses.push_back(&I.getOperand());
 | |
| 
 | |
|       // We can optimize this.
 | |
|       unsigned NewReg = optimizeSDPattern(MI);
 | |
| 
 | |
|       if (NewReg != 0) {
 | |
|         Modified = true;
 | |
|         for (SmallVectorImpl<MachineOperand *>::const_iterator I = Uses.begin(),
 | |
|                E = Uses.end(); I != E; ++I) {
 | |
|           // Make sure to constrain the register class of the new register to
 | |
|           // match what we're replacing. Otherwise we can optimize a DPR_VFP2
 | |
|           // reference into a plain DPR, and that will end poorly. NewReg is
 | |
|           // always virtual here, so there will always be a matching subclass
 | |
|           // to find.
 | |
|           MRI->constrainRegClass(NewReg, MRI->getRegClass((*I)->getReg()));
 | |
| 
 | |
|           DEBUG(dbgs() << "Replacing operand "
 | |
|                        << **I << " with "
 | |
|                        << PrintReg(NewReg) << "\n");
 | |
|           (*I)->substVirtReg(NewReg, 0, *TRI);
 | |
|         }
 | |
|       }
 | |
|       Replacements[MI] = NewReg;
 | |
|     }
 | |
|   }
 | |
|   return Modified;
 | |
| }
 | |
| 
 | |
| bool A15SDOptimizer::runOnMachineFunction(MachineFunction &Fn) {
 | |
|   TII = static_cast<const ARMBaseInstrInfo*>(Fn.getTarget().getInstrInfo());
 | |
|   TRI = Fn.getTarget().getRegisterInfo();
 | |
|   MRI = &Fn.getRegInfo();
 | |
|   bool Modified = false;
 | |
| 
 | |
|   DEBUG(dbgs() << "Running on function " << Fn.getName()<< "\n");
 | |
| 
 | |
|   DeadInstr.clear();
 | |
|   Replacements.clear();
 | |
| 
 | |
|   for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
 | |
|        ++MFI) {
 | |
| 
 | |
|     for (MachineBasicBlock::iterator MI = MFI->begin(), ME = MFI->end();
 | |
|       MI != ME;) {
 | |
|       Modified |= runOnInstruction(MI++);
 | |
|     }
 | |
|  
 | |
|   }
 | |
| 
 | |
|   for (std::set<MachineInstr *>::iterator I = DeadInstr.begin(),
 | |
|                                             E = DeadInstr.end();
 | |
|                                             I != E; ++I) {
 | |
|     (*I)->eraseFromParent();
 | |
|   }
 | |
| 
 | |
|   return Modified;
 | |
| }
 | |
| 
 | |
| FunctionPass *llvm::createA15SDOptimizerPass() {
 | |
|   return new A15SDOptimizer();
 | |
| }
 |