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//===---------- PPCTLSDynamicCall.cpp - TLS Dynamic Call Fixup ------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This pass expands ADDItls{ld,gd}LADDR[32] machine instructions into
// separate ADDItls[gd]L[32] and GETtlsADDR[32] instructions, both of
// which define GPR3. A copy is added from GPR3 to the target virtual
// register of the original instruction. The GETtlsADDR[32] is really
// a call instruction, so its target register is constrained to be GPR3.
// This is not true of ADDItls[gd]L[32], but there is a legacy linker
// optimization bug that requires the target register of the addi of
// a local- or general-dynamic TLS access sequence to be GPR3.
//
// This is done in a late pass so that TLS variable accesses can be
// fully commoned by MachineCSE.
//
//===----------------------------------------------------------------------===//
#include "PPC.h"
#include "PPCInstrBuilder.h"
#include "PPCInstrInfo.h"
#include "PPCTargetMachine.h"
#include "llvm/CodeGen/LiveIntervals.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "ppc-tls-dynamic-call"
namespace {
struct PPCTLSDynamicCall : public MachineFunctionPass {
static char ID;
PPCTLSDynamicCall() : MachineFunctionPass(ID) {
initializePPCTLSDynamicCallPass(*PassRegistry::getPassRegistry());
}
const PPCInstrInfo *TII;
LiveIntervals *LIS;
protected:
bool processBlock(MachineBasicBlock &MBB) {
bool Changed = false;
bool NeedFence = true;
bool Is64Bit = MBB.getParent()->getSubtarget<PPCSubtarget>().isPPC64();
for (MachineBasicBlock::iterator I = MBB.begin(), IE = MBB.end();
I != IE;) {
MachineInstr &MI = *I;
if (MI.getOpcode() != PPC::ADDItlsgdLADDR &&
MI.getOpcode() != PPC::ADDItlsldLADDR &&
MI.getOpcode() != PPC::ADDItlsgdLADDR32 &&
MI.getOpcode() != PPC::ADDItlsldLADDR32) {
// Although we create ADJCALLSTACKDOWN and ADJCALLSTACKUP
// as scheduling fences, we skip creating fences if we already
// have existing ADJCALLSTACKDOWN/UP to avoid nesting,
// which causes verification error with -verify-machineinstrs.
if (MI.getOpcode() == PPC::ADJCALLSTACKDOWN)
NeedFence = false;
else if (MI.getOpcode() == PPC::ADJCALLSTACKUP)
NeedFence = true;
++I;
continue;
}
LLVM_DEBUG(dbgs() << "TLS Dynamic Call Fixup:\n " << MI);
unsigned OutReg = MI.getOperand(0).getReg();
unsigned InReg = MI.getOperand(1).getReg();
DebugLoc DL = MI.getDebugLoc();
unsigned GPR3 = Is64Bit ? PPC::X3 : PPC::R3;
unsigned Opc1, Opc2;
const unsigned OrigRegs[] = {OutReg, InReg, GPR3};
switch (MI.getOpcode()) {
default:
llvm_unreachable("Opcode inconsistency error");
case PPC::ADDItlsgdLADDR:
Opc1 = PPC::ADDItlsgdL;
Opc2 = PPC::GETtlsADDR;
break;
case PPC::ADDItlsldLADDR:
Opc1 = PPC::ADDItlsldL;
Opc2 = PPC::GETtlsldADDR;
break;
case PPC::ADDItlsgdLADDR32:
Opc1 = PPC::ADDItlsgdL32;
Opc2 = PPC::GETtlsADDR32;
break;
case PPC::ADDItlsldLADDR32:
Opc1 = PPC::ADDItlsldL32;
Opc2 = PPC::GETtlsldADDR32;
break;
}
// We create ADJCALLSTACKUP and ADJCALLSTACKDOWN around _tls_get_addr
// as scheduling fence to avoid it is scheduled before
// mflr in the prologue and the address in LR is clobbered (PR25839).
// We don't really need to save data to the stack - the clobbered
// registers are already saved when the SDNode (e.g. PPCaddiTlsgdLAddr)
// gets translated to the pseudo instruction (e.g. ADDItlsgdLADDR).
if (NeedFence)
BuildMI(MBB, I, DL, TII->get(PPC::ADJCALLSTACKDOWN)).addImm(0)
.addImm(0);
// Expand into two ops built prior to the existing instruction.
MachineInstr *Addi = BuildMI(MBB, I, DL, TII->get(Opc1), GPR3)
.addReg(InReg);
Addi->addOperand(MI.getOperand(2));
// The ADDItls* instruction is the first instruction in the
// repair range.
MachineBasicBlock::iterator First = I;
--First;
MachineInstr *Call = (BuildMI(MBB, I, DL, TII->get(Opc2), GPR3)
.addReg(GPR3));
Call->addOperand(MI.getOperand(3));
if (NeedFence)
BuildMI(MBB, I, DL, TII->get(PPC::ADJCALLSTACKUP)).addImm(0).addImm(0);
BuildMI(MBB, I, DL, TII->get(TargetOpcode::COPY), OutReg)
.addReg(GPR3);
// The COPY is the last instruction in the repair range.
MachineBasicBlock::iterator Last = I;
--Last;
// Move past the original instruction and remove it.
++I;
MI.removeFromParent();
// Repair the live intervals.
LIS->repairIntervalsInRange(&MBB, First, Last, OrigRegs);
Changed = true;
}
return Changed;
}
public:
bool runOnMachineFunction(MachineFunction &MF) override {
TII = MF.getSubtarget<PPCSubtarget>().getInstrInfo();
LIS = &getAnalysis<LiveIntervals>();
bool Changed = false;
for (MachineFunction::iterator I = MF.begin(); I != MF.end();) {
MachineBasicBlock &B = *I++;
if (processBlock(B))
Changed = true;
}
return Changed;
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<LiveIntervals>();
AU.addPreserved<LiveIntervals>();
AU.addRequired<SlotIndexes>();
AU.addPreserved<SlotIndexes>();
MachineFunctionPass::getAnalysisUsage(AU);
}
};
}
INITIALIZE_PASS_BEGIN(PPCTLSDynamicCall, DEBUG_TYPE,
"PowerPC TLS Dynamic Call Fixup", false, false)
INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
INITIALIZE_PASS_END(PPCTLSDynamicCall, DEBUG_TYPE,
"PowerPC TLS Dynamic Call Fixup", false, false)
char PPCTLSDynamicCall::ID = 0;
FunctionPass*
llvm::createPPCTLSDynamicCallPass() { return new PPCTLSDynamicCall(); }
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