2015-02-18 17:13:27 +08:00
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//===-- SystemZLDCleanup.cpp - Clean up local-dynamic TLS accesses --------===//
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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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// This pass combines multiple accesses to local-dynamic TLS variables so that
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// the TLS base address for the module is only fetched once per execution path
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// through the function.
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//
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//===----------------------------------------------------------------------===//
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#include "SystemZTargetMachine.h"
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#include "SystemZMachineFunctionInfo.h"
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#include "llvm/CodeGen/MachineDominators.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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using namespace llvm;
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namespace {
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class SystemZLDCleanup : public MachineFunctionPass {
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public:
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static char ID;
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SystemZLDCleanup(const SystemZTargetMachine &tm)
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: MachineFunctionPass(ID), TII(nullptr), MF(nullptr) {}
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const char *getPassName() const override {
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return "SystemZ Local Dynamic TLS Access Clean-up";
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}
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bool runOnMachineFunction(MachineFunction &MF) override;
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void getAnalysisUsage(AnalysisUsage &AU) const override;
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private:
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bool VisitNode(MachineDomTreeNode *Node, unsigned TLSBaseAddrReg);
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MachineInstr *ReplaceTLSCall(MachineInstr *I, unsigned TLSBaseAddrReg);
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MachineInstr *SetRegister(MachineInstr *I, unsigned *TLSBaseAddrReg);
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const SystemZInstrInfo *TII;
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MachineFunction *MF;
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};
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char SystemZLDCleanup::ID = 0;
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} // end anonymous namespace
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FunctionPass *llvm::createSystemZLDCleanupPass(SystemZTargetMachine &TM) {
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return new SystemZLDCleanup(TM);
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}
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void SystemZLDCleanup::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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AU.addRequired<MachineDominatorTree>();
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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bool SystemZLDCleanup::runOnMachineFunction(MachineFunction &F) {
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2016-04-27 07:49:41 +08:00
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if (skipFunction(*F.getFunction()))
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return false;
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2015-02-18 17:13:27 +08:00
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TII = static_cast<const SystemZInstrInfo *>(F.getSubtarget().getInstrInfo());
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MF = &F;
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SystemZMachineFunctionInfo* MFI = F.getInfo<SystemZMachineFunctionInfo>();
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if (MFI->getNumLocalDynamicTLSAccesses() < 2) {
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// No point folding accesses if there isn't at least two.
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return false;
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}
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MachineDominatorTree *DT = &getAnalysis<MachineDominatorTree>();
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return VisitNode(DT->getRootNode(), 0);
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}
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// Visit the dominator subtree rooted at Node in pre-order.
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// If TLSBaseAddrReg is non-null, then use that to replace any
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// TLS_LDCALL instructions. Otherwise, create the register
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// when the first such instruction is seen, and then use it
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// as we encounter more instructions.
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bool SystemZLDCleanup::VisitNode(MachineDomTreeNode *Node,
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unsigned TLSBaseAddrReg) {
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MachineBasicBlock *BB = Node->getBlock();
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bool Changed = false;
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// Traverse the current block.
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for (auto I = BB->begin(), E = BB->end(); I != E; ++I) {
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switch (I->getOpcode()) {
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case SystemZ::TLS_LDCALL:
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if (TLSBaseAddrReg)
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I = ReplaceTLSCall(I, TLSBaseAddrReg);
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else
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I = SetRegister(I, &TLSBaseAddrReg);
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Changed = true;
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break;
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default:
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break;
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}
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}
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// Visit the children of this block in the dominator tree.
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for (auto I = Node->begin(), E = Node->end(); I != E; ++I)
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Changed |= VisitNode(*I, TLSBaseAddrReg);
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return Changed;
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}
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// Replace the TLS_LDCALL instruction I with a copy from TLSBaseAddrReg,
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// returning the new instruction.
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MachineInstr *SystemZLDCleanup::ReplaceTLSCall(MachineInstr *I,
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unsigned TLSBaseAddrReg) {
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// Insert a Copy from TLSBaseAddrReg to R2.
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MachineInstr *Copy = BuildMI(*I->getParent(), I, I->getDebugLoc(),
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TII->get(TargetOpcode::COPY), SystemZ::R2D)
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.addReg(TLSBaseAddrReg);
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// Erase the TLS_LDCALL instruction.
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I->eraseFromParent();
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return Copy;
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}
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// Create a virtal register in *TLSBaseAddrReg, and populate it by
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// inserting a copy instruction after I. Returns the new instruction.
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MachineInstr *SystemZLDCleanup::SetRegister(MachineInstr *I,
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unsigned *TLSBaseAddrReg) {
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// Create a virtual register for the TLS base address.
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MachineRegisterInfo &RegInfo = MF->getRegInfo();
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*TLSBaseAddrReg = RegInfo.createVirtualRegister(&SystemZ::GR64BitRegClass);
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// Insert a copy from R2 to TLSBaseAddrReg.
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MachineInstr *Next = I->getNextNode();
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MachineInstr *Copy = BuildMI(*I->getParent(), Next, I->getDebugLoc(),
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TII->get(TargetOpcode::COPY), *TLSBaseAddrReg)
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.addReg(SystemZ::R2D);
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return Copy;
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}
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