lib/Target/Hexagon/MCTargetDesc/HexagonMCShuffler.cpp

   1 //===----- HexagonMCShuffler.cpp - MC bundle shuffling --------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This implements the shuffling of insns inside a bundle according to the
  10 // packet formation rules of the Hexagon ISA.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #define DEBUG_TYPE "hexagon-shuffle"
  15
  16 #include "MCTargetDesc/HexagonMCShuffler.h"
  17 #include "MCTargetDesc/HexagonMCInstrInfo.h"
  18 #include "MCTargetDesc/HexagonShuffler.h"
  19 #include "llvm/MC/MCInst.h"
  20 #include "llvm/MC/MCInstrDesc.h"
  21 #include "llvm/MC/MCInstrInfo.h"
  22 #include "llvm/Support/CommandLine.h"
  23 #include "llvm/Support/Debug.h"
  24 #include "llvm/Support/raw_ostream.h"
  25 #include <cassert>
  26
  27 using namespace llvm;
  28
  29 static cl::opt<bool>
  30     DisableShuffle("disable-hexagon-shuffle", cl::Hidden, cl::init(false),
  31                    cl::desc("Disable Hexagon instruction shuffling"));
  32
  33 void HexagonMCShuffler::init(MCInst &MCB) {
  34   if (HexagonMCInstrInfo::isBundle(MCB)) {
  35     MCInst const *Extender = nullptr;
  36     // Copy the bundle for the shuffling.
  37     for (const auto &I : HexagonMCInstrInfo::bundleInstructions(MCB)) {
  38       MCInst &MI = *const_cast<MCInst *>(I.getInst());
  39       LLVM_DEBUG(dbgs() << "Shuffling: " << MCII.getName(MI.getOpcode())
  40                         << '\n');
  41       assert(!HexagonMCInstrInfo::getDesc(MCII, MI).isPseudo());
  42
  43       if (!HexagonMCInstrInfo::isImmext(MI)) {
  44         append(MI, Extender, HexagonMCInstrInfo::getUnits(MCII, STI, MI));
  45         Extender = nullptr;
  46       } else
  47         Extender = &MI;
  48     }
  49   }
  50
  51   Loc = MCB.getLoc();
  52   BundleFlags = MCB.getOperand(0).getImm();
  53 }
  54
  55 void HexagonMCShuffler::init(MCInst &MCB, MCInst const &AddMI,
  56                              bool bInsertAtFront) {
  57   if (HexagonMCInstrInfo::isBundle(MCB)) {
  58     if (bInsertAtFront)
  59       append(AddMI, nullptr, HexagonMCInstrInfo::getUnits(MCII, STI, AddMI));
  60     MCInst const *Extender = nullptr;
  61     // Copy the bundle for the shuffling.
  62     for (auto const &I : HexagonMCInstrInfo::bundleInstructions(MCB)) {
  63       assert(!HexagonMCInstrInfo::getDesc(MCII, *I.getInst()).isPseudo());
  64       MCInst &MI = *const_cast<MCInst *>(I.getInst());
  65       if (!HexagonMCInstrInfo::isImmext(MI)) {
  66         append(MI, Extender, HexagonMCInstrInfo::getUnits(MCII, STI, MI));
  67         Extender = nullptr;
  68       } else
  69         Extender = &MI;
  70     }
  71     if (!bInsertAtFront)
  72       append(AddMI, nullptr, HexagonMCInstrInfo::getUnits(MCII, STI, AddMI));
  73   }
  74
  75   Loc = MCB.getLoc();
  76   BundleFlags = MCB.getOperand(0).getImm();
  77 }
  78
  79 void HexagonMCShuffler::copyTo(MCInst &MCB) {
  80   MCB.clear();
  81   MCB.addOperand(MCOperand::createImm(BundleFlags));
  82   MCB.setLoc(Loc);
  83   // Copy the results into the bundle.
  84   for (HexagonShuffler::iterator I = begin(); I != end(); ++I) {
  85
  86     MCInst const &MI = I->getDesc();
  87     MCInst const *Extender = I->getExtender();
  88     if (Extender)
  89       MCB.addOperand(MCOperand::createInst(Extender));
  90     MCB.addOperand(MCOperand::createInst(&MI));
  91   }
  92 }
  93
  94 bool HexagonMCShuffler::reshuffleTo(MCInst &MCB) {
  95   if (shuffle()) {
  96     // Copy the results into the bundle.
  97     copyTo(MCB);
  98     return true;
  99   }
 100   LLVM_DEBUG(MCB.dump());
 101   return false;
 102 }
 103
 104 bool llvm::HexagonMCShuffle(MCContext &Context, bool Fatal,
 105                             MCInstrInfo const &MCII, MCSubtargetInfo const &STI,
 106                             MCInst &MCB) {
 107   HexagonMCShuffler MCS(Context, Fatal, MCII, STI, MCB);
 108
 109   if (DisableShuffle)
 110     // Ignore if user chose so.
 111     return false;
 112
 113   if (!HexagonMCInstrInfo::bundleSize(MCB)) {
 114     // There once was a bundle:
 115     //    BUNDLE implicit-def %d2, implicit-def %r4, implicit-def %r5,
 116     //    implicit-def %d7, ...
 117     //      * %d2 = IMPLICIT_DEF; flags:
 118     //      * %d7 = IMPLICIT_DEF; flags:
 119     // After the IMPLICIT_DEFs were removed by the asm printer, the bundle
 120     // became empty.
 121     LLVM_DEBUG(dbgs() << "Skipping empty bundle");
 122     return false;
 123   } else if (!HexagonMCInstrInfo::isBundle(MCB)) {
 124     LLVM_DEBUG(dbgs() << "Skipping stand-alone insn");
 125     return false;
 126   }
 127
 128   return MCS.reshuffleTo(MCB);
 129 }
 130
 131 bool
 132 llvm::HexagonMCShuffle(MCContext &Context, MCInstrInfo const &MCII,
 133                        MCSubtargetInfo const &STI, MCInst &MCB,
 134                        SmallVector<DuplexCandidate, 8> possibleDuplexes) {
 135   if (DisableShuffle)
 136     return false;
 137
 138   if (!HexagonMCInstrInfo::bundleSize(MCB)) {
 139     // There once was a bundle:
 140     //    BUNDLE implicit-def %d2, implicit-def %r4, implicit-def %r5,
 141     //    implicit-def %d7, ...
 142     //      * %d2 = IMPLICIT_DEF; flags:
 143     //      * %d7 = IMPLICIT_DEF; flags:
 144     // After the IMPLICIT_DEFs were removed by the asm printer, the bundle
 145     // became empty.
 146     LLVM_DEBUG(dbgs() << "Skipping empty bundle");
 147     return false;
 148   } else if (!HexagonMCInstrInfo::isBundle(MCB)) {
 149     LLVM_DEBUG(dbgs() << "Skipping stand-alone insn");
 150     return false;
 151   }
 152
 153   bool doneShuffling = false;
 154   while (possibleDuplexes.size() > 0 && (!doneShuffling)) {
 155     // case of Duplex Found
 156     DuplexCandidate duplexToTry = possibleDuplexes.pop_back_val();
 157     MCInst Attempt(MCB);
 158     HexagonMCInstrInfo::replaceDuplex(Context, Attempt, duplexToTry);
 159     HexagonMCShuffler MCS(Context, false, MCII, STI, Attempt); // copy packet to the shuffler
 160     if (MCS.size() == 1) {                     // case of one duplex
 161       // copy the created duplex in the shuffler to the bundle
 162       MCS.copyTo(MCB);
 163       return false;
 164     }
 165     // try shuffle with this duplex
 166     doneShuffling = MCS.reshuffleTo(MCB);
 167
 168     if (doneShuffling)
 169       break;
 170   }
 171
 172   if (!doneShuffling) {
 173     HexagonMCShuffler MCS(Context, false, MCII, STI, MCB);
 174     doneShuffling = MCS.reshuffleTo(MCB); // shuffle
 175   }
 176   if (!doneShuffling)
 177     return true;
 178
 179   return false;
 180 }
 181
 182 bool llvm::HexagonMCShuffle(MCContext &Context, MCInstrInfo const &MCII,
 183                             MCSubtargetInfo const &STI, MCInst &MCB,
 184                             MCInst const &AddMI, int fixupCount) {
 185   if (!HexagonMCInstrInfo::isBundle(MCB))
 186     return false;
 187
 188   // if fixups present, make sure we don't insert too many nops that would
 189   // later prevent an extender from being inserted.
 190   unsigned int bundleSize = HexagonMCInstrInfo::bundleSize(MCB);
 191   if (bundleSize >= HEXAGON_PACKET_SIZE)
 192     return false;
 193   bool bhasDuplex = HexagonMCInstrInfo::hasDuplex(MCII, MCB);
 194   if (fixupCount >= 2) {
 195     if (bhasDuplex) {
 196       if (bundleSize >= HEXAGON_PACKET_SIZE - 1) {
 197         return false;
 198       }
 199     } else {
 200       return false;
 201     }
 202   } else {
 203     if (bundleSize == HEXAGON_PACKET_SIZE - 1 && fixupCount)
 204       return false;
 205   }
 206
 207   if (DisableShuffle)
 208     return false;
 209
 210   // mgl: temporary code (shuffler doesn't take into account the fact that
 211   // a duplex takes up two slots.  for example, 3 nops can be put into a packet
 212   // containing a duplex oversubscribing slots by 1).
 213   unsigned maxBundleSize = (HexagonMCInstrInfo::hasImmExt(MCB))
 214                                ? HEXAGON_PACKET_SIZE
 215                                : HEXAGON_PACKET_SIZE - 1;
 216   if (bhasDuplex && bundleSize >= maxBundleSize)
 217     return false;
 218
 219   HexagonMCShuffler MCS(Context, false, MCII, STI, MCB, AddMI, false);
 220   return MCS.reshuffleTo(MCB);
 221 }