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Add comment; refactor; avoid pulling in DT if it's not used.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93306 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
parent
ee9250bb4f
commit
d89d5180d1
@ -6,6 +6,16 @@
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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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// This pass performs optimization of sign / zero extension instructions. It
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// may be extended to handle other instructions of similar property.
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//
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// On some targets, some instructions, e.g. X86 sign / zero extension, may
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// leave the source value in the lower part of the result. This pass will
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// replace (some) uses of the pre-extension value with uses of the sub-register
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// of the results.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "ext-opt"
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#include "llvm/CodeGen/Passes.h"
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@ -40,9 +50,15 @@ namespace {
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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MachineFunctionPass::getAnalysisUsage(AU);
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AU.addRequired<MachineDominatorTree>();
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AU.addPreserved<MachineDominatorTree>();
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if (Aggressive) {
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AU.addRequired<MachineDominatorTree>();
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AU.addPreserved<MachineDominatorTree>();
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}
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}
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private:
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bool OptimizeInstr(MachineInstr *MI, MachineBasicBlock *MBB,
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SmallPtrSet<MachineInstr*, 8> &LocalMIs);
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};
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}
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@ -52,98 +68,113 @@ X("opt-exts", "Optimize sign / zero extensions");
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FunctionPass *llvm::createOptimizeExtsPass() { return new OptimizeExts(); }
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bool OptimizeExts::runOnMachineFunction(MachineFunction &MF) {
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TM = &MF.getTarget();
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TII = TM->getInstrInfo();
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MRI = &MF.getRegInfo();
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DT = &getAnalysis<MachineDominatorTree>();
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/// OptimizeInstr - If instruction is a copy-like instruction, i.e. it reads
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/// a single register and writes a single register and it does not modify
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/// the source, and if the source value is preserved as a sub-register of
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/// the result, then replace all reachable uses of the source with the subreg
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/// of the result.
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bool OptimizeExts::OptimizeInstr(MachineInstr *MI, MachineBasicBlock *MBB,
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SmallPtrSet<MachineInstr*, 8> &LocalMIs) {
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bool Changed = false;
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LocalMIs.insert(MI);
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SmallPtrSet<MachineInstr*, 8> LocalMIs;
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for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
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MachineBasicBlock *MBB = &*I;
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for (MachineBasicBlock::iterator MII = I->begin(), ME = I->end(); MII != ME;
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++MII) {
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MachineInstr *MI = &*MII;
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LocalMIs.insert(MI);
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unsigned SrcReg, DstReg, SubIdx;
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if (TII->isCoalescableExtInstr(*MI, SrcReg, DstReg, SubIdx)) {
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if (TargetRegisterInfo::isPhysicalRegister(DstReg) ||
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TargetRegisterInfo::isPhysicalRegister(SrcReg))
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return false;
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unsigned SrcReg, DstReg, SubIdx;
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if (TII->isCoalescableExtInstr(*MI, SrcReg, DstReg, SubIdx)) {
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if (TargetRegisterInfo::isPhysicalRegister(DstReg) ||
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TargetRegisterInfo::isPhysicalRegister(SrcReg))
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continue;
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MachineRegisterInfo::use_iterator UI = MRI->use_begin(SrcReg);
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if (++UI == MRI->use_end())
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// No other uses.
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return false;
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MachineRegisterInfo::use_iterator UI = MRI->use_begin(SrcReg);
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if (++UI == MRI->use_end())
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// No other uses.
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continue;
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// Ok, the source has other uses. See if we can replace the other uses
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// with use of the result of the extension.
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SmallPtrSet<MachineBasicBlock*, 4> ReachedBBs;
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UI = MRI->use_begin(DstReg);
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for (MachineRegisterInfo::use_iterator UE = MRI->use_end(); UI != UE;
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++UI)
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ReachedBBs.insert(UI->getParent());
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// Ok, the source has other uses. See if we can replace the other uses
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// with use of the result of the extension.
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SmallPtrSet<MachineBasicBlock*, 4> ReachedBBs;
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UI = MRI->use_begin(DstReg);
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for (MachineRegisterInfo::use_iterator UE = MRI->use_end(); UI != UE;
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++UI)
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ReachedBBs.insert(UI->getParent());
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bool ExtendLife = true;
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// Uses that are in the same BB of uses of the result of the instruction.
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SmallVector<MachineOperand*, 8> Uses;
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// Uses that the result of the instruction can reach.
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SmallVector<MachineOperand*, 8> ExtendedUses;
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bool ExtendLife = true;
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SmallVector<MachineOperand*, 8> Uses;
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SmallVector<MachineOperand*, 8> ExtendedUses;
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UI = MRI->use_begin(SrcReg);
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for (MachineRegisterInfo::use_iterator UE = MRI->use_end(); UI != UE;
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++UI) {
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MachineOperand &UseMO = UI.getOperand();
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MachineInstr *UseMI = &*UI;
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if (UseMI == MI)
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continue;
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MachineBasicBlock *UseMBB = UseMI->getParent();
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if (UseMBB == MBB) {
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// Local uses that come after the extension.
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if (!LocalMIs.count(UseMI))
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Uses.push_back(&UseMO);
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} else if (ReachedBBs.count(UseMBB))
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// Non-local uses where the result of extension is used. Always
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// replace these.
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Uses.push_back(&UseMO);
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else if (Aggressive && DT->dominates(MBB, UseMBB))
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// We may want to extend live range of the extension result in order
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// to replace these uses.
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ExtendedUses.push_back(&UseMO);
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else {
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// Both will be live out of the def MBB anyway. Don't extend live
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// range of the extension result.
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ExtendLife = false;
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break;
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}
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}
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UI = MRI->use_begin(SrcReg);
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for (MachineRegisterInfo::use_iterator UE = MRI->use_end(); UI != UE;
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++UI) {
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MachineOperand &UseMO = UI.getOperand();
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MachineInstr *UseMI = &*UI;
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if (UseMI == MI)
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continue;
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MachineBasicBlock *UseMBB = UseMI->getParent();
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if (UseMBB == MBB) {
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// Local uses that come after the extension.
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if (!LocalMIs.count(UseMI))
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Uses.push_back(&UseMO);
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} else if (ReachedBBs.count(UseMBB))
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// Non-local uses where the result of extension is used. Always
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// replace these.
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Uses.push_back(&UseMO);
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else if (Aggressive && DT->dominates(MBB, UseMBB))
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// We may want to extend live range of the extension result in order
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// to replace these uses.
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ExtendedUses.push_back(&UseMO);
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else {
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// Both will be live out of the def MBB anyway. Don't extend live
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// range of the extension result.
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ExtendLife = false;
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break;
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}
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}
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if (ExtendLife && !ExtendedUses.empty())
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// Ok, we'll extend the liveness of the extension result.
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std::copy(ExtendedUses.begin(), ExtendedUses.end(),
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std::back_inserter(Uses));
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if (ExtendLife && !ExtendedUses.empty())
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// Ok, we'll extend the liveness of the extension result.
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std::copy(ExtendedUses.begin(), ExtendedUses.end(),
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std::back_inserter(Uses));
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// Now replace all uses.
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if (!Uses.empty()) {
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const TargetRegisterClass *RC = MRI->getRegClass(SrcReg);
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for (unsigned i = 0, e = Uses.size(); i != e; ++i) {
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MachineOperand *UseMO = Uses[i];
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MachineInstr *UseMI = UseMO->getParent();
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MachineBasicBlock *UseMBB = UseMI->getParent();
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unsigned NewVR = MRI->createVirtualRegister(RC);
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BuildMI(*UseMBB, UseMI, UseMI->getDebugLoc(),
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TII->get(TargetInstrInfo::EXTRACT_SUBREG), NewVR)
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.addReg(DstReg).addImm(SubIdx);
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UseMO->setReg(NewVR);
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++NumReuse;
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Changed = true;
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}
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}
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// Now replace all uses.
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if (!Uses.empty()) {
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const TargetRegisterClass *RC = MRI->getRegClass(SrcReg);
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for (unsigned i = 0, e = Uses.size(); i != e; ++i) {
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MachineOperand *UseMO = Uses[i];
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MachineInstr *UseMI = UseMO->getParent();
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MachineBasicBlock *UseMBB = UseMI->getParent();
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unsigned NewVR = MRI->createVirtualRegister(RC);
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BuildMI(*UseMBB, UseMI, UseMI->getDebugLoc(),
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TII->get(TargetInstrInfo::EXTRACT_SUBREG), NewVR)
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.addReg(DstReg).addImm(SubIdx);
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UseMO->setReg(NewVR);
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++NumReuse;
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Changed = true;
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}
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}
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}
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return Changed;
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}
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bool OptimizeExts::runOnMachineFunction(MachineFunction &MF) {
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TM = &MF.getTarget();
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TII = TM->getInstrInfo();
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MRI = &MF.getRegInfo();
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DT = Aggressive ? &getAnalysis<MachineDominatorTree>() : 0;
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bool Changed = false;
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SmallPtrSet<MachineInstr*, 8> LocalMIs;
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for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
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MachineBasicBlock *MBB = &*I;
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LocalMIs.clear();
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for (MachineBasicBlock::iterator MII = I->begin(), ME = I->end(); MII != ME;
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++MII) {
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MachineInstr *MI = &*MII;
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Changed |= OptimizeInstr(MI, MBB, LocalMIs);
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}
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}
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return Changed;
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}
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