llvm/lib/Target/PowerPC/PPCSubtarget.cpp

//===-- PowerPCSubtarget.cpp - PPC Subtarget Information ------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the PPC specific subclass of TargetSubtargetInfo.
//
//===----------------------------------------------------------------------===//

#include "PPCSubtarget.h"
#include "PPC.h"
#include "PPCRegisterInfo.h"
#include "PPCTargetMachine.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineScheduler.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Target/TargetMachine.h"
#include <cstdlib>

using namespace llvm;

#define DEBUG_TYPE "ppc-subtarget"

#define GET_SUBTARGETINFO_TARGET_DESC
#define GET_SUBTARGETINFO_CTOR
#include "PPCGenSubtargetInfo.inc"

static cl::opt<bool> UseSubRegLiveness("ppc-track-subreg-liveness",
cl::desc("Enable subregister liveness tracking for PPC"), cl::Hidden);

static cl::opt<bool> QPXStackUnaligned("qpx-stack-unaligned",
  cl::desc("Even when QPX is enabled the stack is not 32-byte aligned"),
  cl::Hidden);

PPCSubtarget &PPCSubtarget::initializeSubtargetDependencies(StringRef CPU,
                                                            StringRef FS) {
  initializeEnvironment();
  initSubtargetFeatures(CPU, FS);
  return *this;
}

PPCSubtarget::PPCSubtarget(const Triple &TT, const std::string &CPU,
                           const std::string &FS, const PPCTargetMachine &TM)
    : PPCGenSubtargetInfo(TT, CPU, FS), TargetTriple(TT),
      IsPPC64(TargetTriple.getArch() == Triple::ppc64 ||
              TargetTriple.getArch() == Triple::ppc64le),
      TM(TM), FrameLowering(initializeSubtargetDependencies(CPU, FS)),
      InstrInfo(*this), TLInfo(TM, *this) {}

void PPCSubtarget::initializeEnvironment() {
  StackAlignment = 16;
  DarwinDirective = PPC::DIR_NONE;
  HasMFOCRF = false;
  Has64BitSupport = false;
  Use64BitRegs = false;
  UseCRBits = false;
  UseSoftFloat = false;
  HasAltivec = false;
  HasSPE = false;
  HasQPX = false;
  HasVSX = false;
  HasP8Vector = false;
  HasP8Altivec = false;
  HasP8Crypto = false;
  HasP9Vector = false;
  HasP9Altivec = false;
  HasFCPSGN = false;
  HasFSQRT = false;
  HasFRE = false;
  HasFRES = false;
  HasFRSQRTE = false;
  HasFRSQRTES = false;
  HasRecipPrec = false;
  HasSTFIWX = false;
  HasLFIWAX = false;
  HasFPRND = false;
  HasFPCVT = false;
  HasISEL = false;
  HasBPERMD = false;
  HasExtDiv = false;
  HasCMPB = false;
  HasLDBRX = false;
  IsBookE = false;
  HasOnlyMSYNC = false;
  IsPPC4xx = false;
  IsPPC6xx = false;
  IsE500 = false;
  FeatureMFTB = false;
  DeprecatedDST = false;
  HasLazyResolverStubs = false;
  HasICBT = false;
  HasInvariantFunctionDescriptors = false;
  HasPartwordAtomics = false;
  HasDirectMove = false;
  IsQPXStackUnaligned = false;
  HasHTM = false;
  HasFusion = false;
  HasFloat128 = false;
  IsISA3_0 = false;

  HasPOPCNTD = POPCNTD_Unavailable;
}

void PPCSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
  // Determine default and user specified characteristics
  std::string CPUName = CPU;
  if (CPUName.empty() || CPU == "generic") {
    // If cross-compiling with -march=ppc64le without -mcpu
    if (TargetTriple.getArch() == Triple::ppc64le)
      CPUName = "ppc64le";
    else
      CPUName = "generic";
  }

  // Initialize scheduling itinerary for the specified CPU.
  InstrItins = getInstrItineraryForCPU(CPUName);

  // Parse features string.
  ParseSubtargetFeatures(CPUName, FS);

  // If the user requested use of 64-bit regs, but the cpu selected doesn't
  // support it, ignore.
  if (IsPPC64 && has64BitSupport())
    Use64BitRegs = true;

  // Set up darwin-specific properties.
  if (isDarwin())
    HasLazyResolverStubs = true;

  // QPX requires a 32-byte aligned stack. Note that we need to do this if
  // we're compiling for a BG/Q system regardless of whether or not QPX
  // is enabled because external functions will assume this alignment.
  IsQPXStackUnaligned = QPXStackUnaligned;
  StackAlignment = getPlatformStackAlignment();

  // Determine endianness.
  // FIXME: Part of the TargetMachine.
  IsLittleEndian = (TargetTriple.getArch() == Triple::ppc64le);
}

/// Return true if accesses to the specified global have to go through a dyld
/// lazy resolution stub.  This means that an extra load is required to get the
/// address of the global.
bool PPCSubtarget::hasLazyResolverStub(const GlobalValue *GV) const {
  if (!HasLazyResolverStubs)
    return false;
  if (!shouldAssumeDSOLocal(TM.getRelocationModel(), TM.getTargetTriple(),
                            *GV->getParent(), GV))
    return true;
  // 32 bit macho has no relocation for a-b if a is undefined, even if b is in
  // the section that is being relocated. This means we have to use o load even
  // for GVs that are known to be local to the dso.
  if (GV->isDeclarationForLinker() || GV->hasCommonLinkage())
    return true;
  return false;
}

// Embedded cores need aggressive scheduling (and some others also benefit).
static bool needsAggressiveScheduling(unsigned Directive) {
  switch (Directive) {
  default: return false;
  case PPC::DIR_440:
  case PPC::DIR_A2:
  case PPC::DIR_E500mc:
  case PPC::DIR_E5500:
  case PPC::DIR_PWR7:
  case PPC::DIR_PWR8:
  // FIXME: Same as P8 until POWER9 scheduling info is available
  case PPC::DIR_PWR9:
    return true;
  }
}

bool PPCSubtarget::enableMachineScheduler() const {
  // Enable MI scheduling for the embedded cores.
  // FIXME: Enable this for all cores (some additional modeling
  // may be necessary).
  return needsAggressiveScheduling(DarwinDirective);
}

// This overrides the PostRAScheduler bit in the SchedModel for each CPU.
bool PPCSubtarget::enablePostRAScheduler() const { return true; }

PPCGenSubtargetInfo::AntiDepBreakMode PPCSubtarget::getAntiDepBreakMode() const {
  return TargetSubtargetInfo::ANTIDEP_ALL;
}

void PPCSubtarget::getCriticalPathRCs(RegClassVector &CriticalPathRCs) const {
  CriticalPathRCs.clear();
  CriticalPathRCs.push_back(isPPC64() ?
                            &PPC::G8RCRegClass : &PPC::GPRCRegClass);
}

void PPCSubtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
                                       MachineInstr *begin,
                                       MachineInstr *end,
                                       unsigned NumRegionInstrs) const {
  if (needsAggressiveScheduling(DarwinDirective)) {
    Policy.OnlyTopDown = false;
    Policy.OnlyBottomUp = false;
  }

  // Spilling is generally expensive on all PPC cores, so always enable
  // register-pressure tracking.
  Policy.ShouldTrackPressure = true;
}

bool PPCSubtarget::useAA() const {
  // Use AA during code generation for the embedded cores.
  return needsAggressiveScheduling(DarwinDirective);
}

bool PPCSubtarget::enableSubRegLiveness() const {
  return UseSubRegLiveness;
}

unsigned char PPCSubtarget::classifyGlobalReference(
    const GlobalValue *GV) const {
  // Note that currently we don't generate non-pic references.
  // If a caller wants that, this will have to be updated.

  // Large code model always uses the TOC even for local symbols.
  if (TM.getCodeModel() == CodeModel::Large)
    return PPCII::MO_PIC_FLAG | PPCII::MO_NLP_FLAG;

  unsigned char flags = PPCII::MO_PIC_FLAG;

  // Only if the relocation mode is PIC do we have to worry about
  // interposition. In all other cases we can use a slightly looser standard to
  // decide how to access the symbol.
  if (TM.getRelocationModel() == Reloc::PIC_) {
    // If it's local, or it's non-default, it can't be interposed.
    if (!GV->hasLocalLinkage() &&
        GV->hasDefaultVisibility()) {
      flags |= PPCII::MO_NLP_FLAG;
    }
    return flags;
  }

  if (GV->isStrongDefinitionForLinker())
    return flags;
  return flags | PPCII::MO_NLP_FLAG;
}

bool PPCSubtarget::isELFv2ABI() const { return TM.isELFv2ABI(); }
bool PPCSubtarget::isPPC64() const { return TM.isPPC64(); }