From 7b837d8c75f78fe55c9b348b9ec2281169a48d2a Mon Sep 17 00:00:00 2001 From: Tim Northover Date: Sat, 29 Mar 2014 10:18:08 +0000 Subject: ARM64: initial backend import This adds a second implementation of the AArch64 architecture to LLVM, accessible in parallel via the "arm64" triple. The plan over the coming weeks & months is to merge the two into a single backend, during which time thorough code review should naturally occur. Everything will be easier with the target in-tree though, hence this commit. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205090 91177308-0d34-0410-b5e6-96231b3b80d8 --- .../ARM64/ARM64CleanupLocalDynamicTLSPass.cpp | 148 +++++++++++++++++++++ 1 file changed, 148 insertions(+) create mode 100644 lib/Target/ARM64/ARM64CleanupLocalDynamicTLSPass.cpp (limited to 'lib/Target/ARM64/ARM64CleanupLocalDynamicTLSPass.cpp') diff --git a/lib/Target/ARM64/ARM64CleanupLocalDynamicTLSPass.cpp b/lib/Target/ARM64/ARM64CleanupLocalDynamicTLSPass.cpp new file mode 100644 index 0000000000..33fe6ef9da --- /dev/null +++ b/lib/Target/ARM64/ARM64CleanupLocalDynamicTLSPass.cpp @@ -0,0 +1,148 @@ +//===-- ARM64CleanupLocalDynamicTLSPass.cpp -----------------------*- C++ -*-=// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// Local-dynamic access to thread-local variables proceeds in three stages. +// +// 1. The offset of this Module's thread-local area from TPIDR_EL0 is calculated +// in much the same way as a general-dynamic TLS-descriptor access against +// the special symbol _TLS_MODULE_BASE. +// 2. The variable's offset from _TLS_MODULE_BASE_ is calculated using +// instructions with "dtprel" modifiers. +// 3. These two are added, together with TPIDR_EL0, to obtain the variable's +// true address. +// +// This is only better than general-dynamic access to the variable if two or +// more of the first stage TLS-descriptor calculations can be combined. This +// pass looks through a function and performs such combinations. +// +//===----------------------------------------------------------------------===// +#include "ARM64.h" +#include "ARM64InstrInfo.h" +#include "ARM64MachineFunctionInfo.h" +#include "ARM64TargetMachine.h" +#include "llvm/CodeGen/MachineDominators.h" +#include "llvm/CodeGen/MachineFunction.h" +#include "llvm/CodeGen/MachineFunctionPass.h" +#include "llvm/CodeGen/MachineInstrBuilder.h" +#include "llvm/CodeGen/MachineRegisterInfo.h" +using namespace llvm; + +namespace { +struct LDTLSCleanup : public MachineFunctionPass { + static char ID; + LDTLSCleanup() : MachineFunctionPass(ID) {} + + virtual bool runOnMachineFunction(MachineFunction &MF) { + ARM64FunctionInfo *AFI = MF.getInfo(); + if (AFI->getNumLocalDynamicTLSAccesses() < 2) { + // No point folding accesses if there isn't at least two. + return false; + } + + MachineDominatorTree *DT = &getAnalysis(); + return VisitNode(DT->getRootNode(), 0); + } + + // Visit the dominator subtree rooted at Node in pre-order. + // If TLSBaseAddrReg is non-null, then use that to replace any + // TLS_base_addr instructions. Otherwise, create the register + // when the first such instruction is seen, and then use it + // as we encounter more instructions. + bool VisitNode(MachineDomTreeNode *Node, unsigned TLSBaseAddrReg) { + MachineBasicBlock *BB = Node->getBlock(); + bool Changed = false; + + // Traverse the current block. + for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; + ++I) { + switch (I->getOpcode()) { + case ARM64::TLSDESC_BLR: + // Make sure it's a local dynamic access. + if (!I->getOperand(1).isSymbol() || + strcmp(I->getOperand(1).getSymbolName(), "_TLS_MODULE_BASE_")) + break; + + if (TLSBaseAddrReg) + I = replaceTLSBaseAddrCall(I, TLSBaseAddrReg); + else + I = setRegister(I, &TLSBaseAddrReg); + Changed = true; + break; + default: + break; + } + } + + // Visit the children of this block in the dominator tree. + for (MachineDomTreeNode::iterator I = Node->begin(), E = Node->end(); + I != E; ++I) { + Changed |= VisitNode(*I, TLSBaseAddrReg); + } + + return Changed; + } + + // Replace the TLS_base_addr instruction I with a copy from + // TLSBaseAddrReg, returning the new instruction. + MachineInstr *replaceTLSBaseAddrCall(MachineInstr *I, + unsigned TLSBaseAddrReg) { + MachineFunction *MF = I->getParent()->getParent(); + const ARM64TargetMachine *TM = + static_cast(&MF->getTarget()); + const ARM64InstrInfo *TII = TM->getInstrInfo(); + + // Insert a Copy from TLSBaseAddrReg to x0, which is where the rest of the + // code sequence assumes the address will be. + MachineInstr *Copy = + BuildMI(*I->getParent(), I, I->getDebugLoc(), + TII->get(TargetOpcode::COPY), ARM64::X0).addReg(TLSBaseAddrReg); + + // Erase the TLS_base_addr instruction. + I->eraseFromParent(); + + return Copy; + } + + // Create a virtal register in *TLSBaseAddrReg, and populate it by + // inserting a copy instruction after I. Returns the new instruction. + MachineInstr *setRegister(MachineInstr *I, unsigned *TLSBaseAddrReg) { + MachineFunction *MF = I->getParent()->getParent(); + const ARM64TargetMachine *TM = + static_cast(&MF->getTarget()); + const ARM64InstrInfo *TII = TM->getInstrInfo(); + + // Create a virtual register for the TLS base address. + MachineRegisterInfo &RegInfo = MF->getRegInfo(); + *TLSBaseAddrReg = RegInfo.createVirtualRegister(&ARM64::GPR64RegClass); + + // Insert a copy from X0 to TLSBaseAddrReg for later. + MachineInstr *Next = I->getNextNode(); + MachineInstr *Copy = BuildMI(*I->getParent(), Next, I->getDebugLoc(), + TII->get(TargetOpcode::COPY), + *TLSBaseAddrReg).addReg(ARM64::X0); + + return Copy; + } + + virtual const char *getPassName() const { + return "Local Dynamic TLS Access Clean-up"; + } + + virtual void getAnalysisUsage(AnalysisUsage &AU) const { + AU.setPreservesCFG(); + AU.addRequired(); + MachineFunctionPass::getAnalysisUsage(AU); + } +}; +} + +char LDTLSCleanup::ID = 0; +FunctionPass *llvm::createARM64CleanupLocalDynamicTLSPass() { + return new LDTLSCleanup(); +} -- cgit v1.2.3