| File: | lib/CodeGen/BranchFolding.cpp |
| Warning: | line 1496, column 11 Forming reference to null pointer |
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| 1 | //===- BranchFolding.cpp - Fold machine code branch instructions ----------===// | |||||||||
| 2 | // | |||||||||
| 3 | // The LLVM Compiler Infrastructure | |||||||||
| 4 | // | |||||||||
| 5 | // This file is distributed under the University of Illinois Open Source | |||||||||
| 6 | // License. See LICENSE.TXT for details. | |||||||||
| 7 | // | |||||||||
| 8 | //===----------------------------------------------------------------------===// | |||||||||
| 9 | // | |||||||||
| 10 | // This pass forwards branches to unconditional branches to make them branch | |||||||||
| 11 | // directly to the target block. This pass often results in dead MBB's, which | |||||||||
| 12 | // it then removes. | |||||||||
| 13 | // | |||||||||
| 14 | // Note that this pass must be run after register allocation, it cannot handle | |||||||||
| 15 | // SSA form. It also must handle virtual registers for targets that emit virtual | |||||||||
| 16 | // ISA (e.g. NVPTX). | |||||||||
| 17 | // | |||||||||
| 18 | //===----------------------------------------------------------------------===// | |||||||||
| 19 | ||||||||||
| 20 | #include "BranchFolding.h" | |||||||||
| 21 | #include "llvm/ADT/BitVector.h" | |||||||||
| 22 | #include "llvm/ADT/DenseMap.h" | |||||||||
| 23 | #include "llvm/ADT/STLExtras.h" | |||||||||
| 24 | #include "llvm/ADT/SmallPtrSet.h" | |||||||||
| 25 | #include "llvm/ADT/SmallSet.h" | |||||||||
| 26 | #include "llvm/ADT/SmallVector.h" | |||||||||
| 27 | #include "llvm/ADT/Statistic.h" | |||||||||
| 28 | #include "llvm/CodeGen/Analysis.h" | |||||||||
| 29 | #include "llvm/CodeGen/LivePhysRegs.h" | |||||||||
| 30 | #include "llvm/CodeGen/MachineBasicBlock.h" | |||||||||
| 31 | #include "llvm/CodeGen/MachineBlockFrequencyInfo.h" | |||||||||
| 32 | #include "llvm/CodeGen/MachineBranchProbabilityInfo.h" | |||||||||
| 33 | #include "llvm/CodeGen/MachineFunction.h" | |||||||||
| 34 | #include "llvm/CodeGen/MachineFunctionPass.h" | |||||||||
| 35 | #include "llvm/CodeGen/MachineInstr.h" | |||||||||
| 36 | #include "llvm/CodeGen/MachineInstrBuilder.h" | |||||||||
| 37 | #include "llvm/CodeGen/MachineJumpTableInfo.h" | |||||||||
| 38 | #include "llvm/CodeGen/MachineLoopInfo.h" | |||||||||
| 39 | #include "llvm/CodeGen/MachineModuleInfo.h" | |||||||||
| 40 | #include "llvm/CodeGen/MachineOperand.h" | |||||||||
| 41 | #include "llvm/CodeGen/MachineRegisterInfo.h" | |||||||||
| 42 | #include "llvm/CodeGen/TargetInstrInfo.h" | |||||||||
| 43 | #include "llvm/CodeGen/TargetOpcodes.h" | |||||||||
| 44 | #include "llvm/CodeGen/TargetPassConfig.h" | |||||||||
| 45 | #include "llvm/CodeGen/TargetRegisterInfo.h" | |||||||||
| 46 | #include "llvm/CodeGen/TargetSubtargetInfo.h" | |||||||||
| 47 | #include "llvm/IR/DebugInfoMetadata.h" | |||||||||
| 48 | #include "llvm/IR/DebugLoc.h" | |||||||||
| 49 | #include "llvm/IR/Function.h" | |||||||||
| 50 | #include "llvm/MC/LaneBitmask.h" | |||||||||
| 51 | #include "llvm/MC/MCRegisterInfo.h" | |||||||||
| 52 | #include "llvm/Pass.h" | |||||||||
| 53 | #include "llvm/Support/BlockFrequency.h" | |||||||||
| 54 | #include "llvm/Support/BranchProbability.h" | |||||||||
| 55 | #include "llvm/Support/CommandLine.h" | |||||||||
| 56 | #include "llvm/Support/Debug.h" | |||||||||
| 57 | #include "llvm/Support/ErrorHandling.h" | |||||||||
| 58 | #include "llvm/Support/raw_ostream.h" | |||||||||
| 59 | #include "llvm/Target/TargetMachine.h" | |||||||||
| 60 | #include <cassert> | |||||||||
| 61 | #include <cstddef> | |||||||||
| 62 | #include <iterator> | |||||||||
| 63 | #include <numeric> | |||||||||
| 64 | #include <vector> | |||||||||
| 65 | ||||||||||
| 66 | using namespace llvm; | |||||||||
| 67 | ||||||||||
| 68 | #define DEBUG_TYPE"branch-folder" "branch-folder" | |||||||||
| 69 | ||||||||||
| 70 | STATISTIC(NumDeadBlocks, "Number of dead blocks removed")static llvm::Statistic NumDeadBlocks = {"branch-folder", "NumDeadBlocks" , "Number of dead blocks removed", {0}, {false}}; | |||||||||
| 71 | STATISTIC(NumBranchOpts, "Number of branches optimized")static llvm::Statistic NumBranchOpts = {"branch-folder", "NumBranchOpts" , "Number of branches optimized", {0}, {false}}; | |||||||||
| 72 | STATISTIC(NumTailMerge , "Number of block tails merged")static llvm::Statistic NumTailMerge = {"branch-folder", "NumTailMerge" , "Number of block tails merged", {0}, {false}}; | |||||||||
| 73 | STATISTIC(NumHoist , "Number of times common instructions are hoisted")static llvm::Statistic NumHoist = {"branch-folder", "NumHoist" , "Number of times common instructions are hoisted", {0}, {false }}; | |||||||||
| 74 | STATISTIC(NumTailCalls, "Number of tail calls optimized")static llvm::Statistic NumTailCalls = {"branch-folder", "NumTailCalls" , "Number of tail calls optimized", {0}, {false}}; | |||||||||
| 75 | ||||||||||
| 76 | static cl::opt<cl::boolOrDefault> FlagEnableTailMerge("enable-tail-merge", | |||||||||
| 77 | cl::init(cl::BOU_UNSET), cl::Hidden); | |||||||||
| 78 | ||||||||||
| 79 | // Throttle for huge numbers of predecessors (compile speed problems) | |||||||||
| 80 | static cl::opt<unsigned> | |||||||||
| 81 | TailMergeThreshold("tail-merge-threshold", | |||||||||
| 82 | cl::desc("Max number of predecessors to consider tail merging"), | |||||||||
| 83 | cl::init(150), cl::Hidden); | |||||||||
| 84 | ||||||||||
| 85 | // Heuristic for tail merging (and, inversely, tail duplication). | |||||||||
| 86 | // TODO: This should be replaced with a target query. | |||||||||
| 87 | static cl::opt<unsigned> | |||||||||
| 88 | TailMergeSize("tail-merge-size", | |||||||||
| 89 | cl::desc("Min number of instructions to consider tail merging"), | |||||||||
| 90 | cl::init(3), cl::Hidden); | |||||||||
| 91 | ||||||||||
| 92 | namespace { | |||||||||
| 93 | ||||||||||
| 94 | /// BranchFolderPass - Wrap branch folder in a machine function pass. | |||||||||
| 95 | class BranchFolderPass : public MachineFunctionPass { | |||||||||
| 96 | public: | |||||||||
| 97 | static char ID; | |||||||||
| 98 | ||||||||||
| 99 | explicit BranchFolderPass(): MachineFunctionPass(ID) {} | |||||||||
| 100 | ||||||||||
| 101 | bool runOnMachineFunction(MachineFunction &MF) override; | |||||||||
| 102 | ||||||||||
| 103 | void getAnalysisUsage(AnalysisUsage &AU) const override { | |||||||||
| 104 | AU.addRequired<MachineBlockFrequencyInfo>(); | |||||||||
| 105 | AU.addRequired<MachineBranchProbabilityInfo>(); | |||||||||
| 106 | AU.addRequired<TargetPassConfig>(); | |||||||||
| 107 | MachineFunctionPass::getAnalysisUsage(AU); | |||||||||
| 108 | } | |||||||||
| 109 | }; | |||||||||
| 110 | ||||||||||
| 111 | } // end anonymous namespace | |||||||||
| 112 | ||||||||||
| 113 | char BranchFolderPass::ID = 0; | |||||||||
| 114 | ||||||||||
| 115 | char &llvm::BranchFolderPassID = BranchFolderPass::ID; | |||||||||
| 116 | ||||||||||
| 117 | INITIALIZE_PASS(BranchFolderPass, DEBUG_TYPE,static void *initializeBranchFolderPassPassOnce(PassRegistry & Registry) { PassInfo *PI = new PassInfo( "Control Flow Optimizer" , "branch-folder", &BranchFolderPass::ID, PassInfo::NormalCtor_t (callDefaultCtor<BranchFolderPass>), false, false); Registry .registerPass(*PI, true); return PI; } static llvm::once_flag InitializeBranchFolderPassPassFlag; void llvm::initializeBranchFolderPassPass (PassRegistry &Registry) { llvm::call_once(InitializeBranchFolderPassPassFlag , initializeBranchFolderPassPassOnce, std::ref(Registry)); } | |||||||||
| 118 | "Control Flow Optimizer", false, false)static void *initializeBranchFolderPassPassOnce(PassRegistry & Registry) { PassInfo *PI = new PassInfo( "Control Flow Optimizer" , "branch-folder", &BranchFolderPass::ID, PassInfo::NormalCtor_t (callDefaultCtor<BranchFolderPass>), false, false); Registry .registerPass(*PI, true); return PI; } static llvm::once_flag InitializeBranchFolderPassPassFlag; void llvm::initializeBranchFolderPassPass (PassRegistry &Registry) { llvm::call_once(InitializeBranchFolderPassPassFlag , initializeBranchFolderPassPassOnce, std::ref(Registry)); } | |||||||||
| 119 | ||||||||||
| 120 | bool BranchFolderPass::runOnMachineFunction(MachineFunction &MF) { | |||||||||
| 121 | if (skipFunction(MF.getFunction())) | |||||||||
| 122 | return false; | |||||||||
| 123 | ||||||||||
| 124 | TargetPassConfig *PassConfig = &getAnalysis<TargetPassConfig>(); | |||||||||
| 125 | // TailMerge can create jump into if branches that make CFG irreducible for | |||||||||
| 126 | // HW that requires structurized CFG. | |||||||||
| 127 | bool EnableTailMerge = !MF.getTarget().requiresStructuredCFG() && | |||||||||
| 128 | PassConfig->getEnableTailMerge(); | |||||||||
| 129 | BranchFolder::MBFIWrapper MBBFreqInfo( | |||||||||
| 130 | getAnalysis<MachineBlockFrequencyInfo>()); | |||||||||
| 131 | BranchFolder Folder(EnableTailMerge, /*CommonHoist=*/true, MBBFreqInfo, | |||||||||
| 132 | getAnalysis<MachineBranchProbabilityInfo>()); | |||||||||
| 133 | return Folder.OptimizeFunction(MF, MF.getSubtarget().getInstrInfo(), | |||||||||
| 134 | MF.getSubtarget().getRegisterInfo(), | |||||||||
| 135 | getAnalysisIfAvailable<MachineModuleInfo>()); | |||||||||
| 136 | } | |||||||||
| 137 | ||||||||||
| 138 | BranchFolder::BranchFolder(bool defaultEnableTailMerge, bool CommonHoist, | |||||||||
| 139 | MBFIWrapper &FreqInfo, | |||||||||
| 140 | const MachineBranchProbabilityInfo &ProbInfo, | |||||||||
| 141 | unsigned MinTailLength) | |||||||||
| 142 | : EnableHoistCommonCode(CommonHoist), MinCommonTailLength(MinTailLength), | |||||||||
| 143 | MBBFreqInfo(FreqInfo), MBPI(ProbInfo) { | |||||||||
| 144 | if (MinCommonTailLength == 0) | |||||||||
| 145 | MinCommonTailLength = TailMergeSize; | |||||||||
| 146 | switch (FlagEnableTailMerge) { | |||||||||
| 147 | case cl::BOU_UNSET: EnableTailMerge = defaultEnableTailMerge; break; | |||||||||
| 148 | case cl::BOU_TRUE: EnableTailMerge = true; break; | |||||||||
| 149 | case cl::BOU_FALSE: EnableTailMerge = false; break; | |||||||||
| 150 | } | |||||||||
| 151 | } | |||||||||
| 152 | ||||||||||
| 153 | void BranchFolder::RemoveDeadBlock(MachineBasicBlock *MBB) { | |||||||||
| 154 | assert(MBB->pred_empty() && "MBB must be dead!")(static_cast <bool> (MBB->pred_empty() && "MBB must be dead!" ) ? void (0) : __assert_fail ("MBB->pred_empty() && \"MBB must be dead!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 154, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 155 | DEBUG(dbgs() << "\nRemoving MBB: " << *MBB)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nRemoving MBB: " << *MBB; } } while (false); | |||||||||
| 156 | ||||||||||
| 157 | MachineFunction *MF = MBB->getParent(); | |||||||||
| 158 | // drop all successors. | |||||||||
| 159 | while (!MBB->succ_empty()) | |||||||||
| 160 | MBB->removeSuccessor(MBB->succ_end()-1); | |||||||||
| 161 | ||||||||||
| 162 | // Avoid matching if this pointer gets reused. | |||||||||
| 163 | TriedMerging.erase(MBB); | |||||||||
| 164 | ||||||||||
| 165 | // Remove the block. | |||||||||
| 166 | MF->erase(MBB); | |||||||||
| 167 | FuncletMembership.erase(MBB); | |||||||||
| 168 | if (MLI) | |||||||||
| 169 | MLI->removeBlock(MBB); | |||||||||
| 170 | } | |||||||||
| 171 | ||||||||||
| 172 | bool BranchFolder::OptimizeFunction(MachineFunction &MF, | |||||||||
| 173 | const TargetInstrInfo *tii, | |||||||||
| 174 | const TargetRegisterInfo *tri, | |||||||||
| 175 | MachineModuleInfo *mmi, | |||||||||
| 176 | MachineLoopInfo *mli, bool AfterPlacement) { | |||||||||
| 177 | if (!tii) return false; | |||||||||
| 178 | ||||||||||
| 179 | TriedMerging.clear(); | |||||||||
| 180 | ||||||||||
| 181 | MachineRegisterInfo &MRI = MF.getRegInfo(); | |||||||||
| 182 | AfterBlockPlacement = AfterPlacement; | |||||||||
| 183 | TII = tii; | |||||||||
| 184 | TRI = tri; | |||||||||
| 185 | MMI = mmi; | |||||||||
| 186 | MLI = mli; | |||||||||
| 187 | this->MRI = &MRI; | |||||||||
| 188 | ||||||||||
| 189 | UpdateLiveIns = MRI.tracksLiveness() && TRI->trackLivenessAfterRegAlloc(MF); | |||||||||
| 190 | if (!UpdateLiveIns) | |||||||||
| 191 | MRI.invalidateLiveness(); | |||||||||
| 192 | ||||||||||
| 193 | // Fix CFG. The later algorithms expect it to be right. | |||||||||
| 194 | bool MadeChange = false; | |||||||||
| 195 | for (MachineBasicBlock &MBB : MF) { | |||||||||
| 196 | MachineBasicBlock *TBB = nullptr, *FBB = nullptr; | |||||||||
| 197 | SmallVector<MachineOperand, 4> Cond; | |||||||||
| 198 | if (!TII->analyzeBranch(MBB, TBB, FBB, Cond, true)) | |||||||||
| 199 | MadeChange |= MBB.CorrectExtraCFGEdges(TBB, FBB, !Cond.empty()); | |||||||||
| 200 | } | |||||||||
| 201 | ||||||||||
| 202 | // Recalculate funclet membership. | |||||||||
| 203 | FuncletMembership = getFuncletMembership(MF); | |||||||||
| 204 | ||||||||||
| 205 | bool MadeChangeThisIteration = true; | |||||||||
| 206 | while (MadeChangeThisIteration) { | |||||||||
| 207 | MadeChangeThisIteration = TailMergeBlocks(MF); | |||||||||
| 208 | // No need to clean up if tail merging does not change anything after the | |||||||||
| 209 | // block placement. | |||||||||
| 210 | if (!AfterBlockPlacement || MadeChangeThisIteration) | |||||||||
| 211 | MadeChangeThisIteration |= OptimizeBranches(MF); | |||||||||
| 212 | if (EnableHoistCommonCode) | |||||||||
| 213 | MadeChangeThisIteration |= HoistCommonCode(MF); | |||||||||
| 214 | MadeChange |= MadeChangeThisIteration; | |||||||||
| 215 | } | |||||||||
| 216 | ||||||||||
| 217 | // See if any jump tables have become dead as the code generator | |||||||||
| 218 | // did its thing. | |||||||||
| 219 | MachineJumpTableInfo *JTI = MF.getJumpTableInfo(); | |||||||||
| 220 | if (!JTI) | |||||||||
| 221 | return MadeChange; | |||||||||
| 222 | ||||||||||
| 223 | // Walk the function to find jump tables that are live. | |||||||||
| 224 | BitVector JTIsLive(JTI->getJumpTables().size()); | |||||||||
| 225 | for (const MachineBasicBlock &BB : MF) { | |||||||||
| 226 | for (const MachineInstr &I : BB) | |||||||||
| 227 | for (const MachineOperand &Op : I.operands()) { | |||||||||
| 228 | if (!Op.isJTI()) continue; | |||||||||
| 229 | ||||||||||
| 230 | // Remember that this JT is live. | |||||||||
| 231 | JTIsLive.set(Op.getIndex()); | |||||||||
| 232 | } | |||||||||
| 233 | } | |||||||||
| 234 | ||||||||||
| 235 | // Finally, remove dead jump tables. This happens when the | |||||||||
| 236 | // indirect jump was unreachable (and thus deleted). | |||||||||
| 237 | for (unsigned i = 0, e = JTIsLive.size(); i != e; ++i) | |||||||||
| 238 | if (!JTIsLive.test(i)) { | |||||||||
| 239 | JTI->RemoveJumpTable(i); | |||||||||
| 240 | MadeChange = true; | |||||||||
| 241 | } | |||||||||
| 242 | ||||||||||
| 243 | return MadeChange; | |||||||||
| 244 | } | |||||||||
| 245 | ||||||||||
| 246 | //===----------------------------------------------------------------------===// | |||||||||
| 247 | // Tail Merging of Blocks | |||||||||
| 248 | //===----------------------------------------------------------------------===// | |||||||||
| 249 | ||||||||||
| 250 | /// HashMachineInstr - Compute a hash value for MI and its operands. | |||||||||
| 251 | static unsigned HashMachineInstr(const MachineInstr &MI) { | |||||||||
| 252 | unsigned Hash = MI.getOpcode(); | |||||||||
| 253 | for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { | |||||||||
| 254 | const MachineOperand &Op = MI.getOperand(i); | |||||||||
| 255 | ||||||||||
| 256 | // Merge in bits from the operand if easy. We can't use MachineOperand's | |||||||||
| 257 | // hash_code here because it's not deterministic and we sort by hash value | |||||||||
| 258 | // later. | |||||||||
| 259 | unsigned OperandHash = 0; | |||||||||
| 260 | switch (Op.getType()) { | |||||||||
| 261 | case MachineOperand::MO_Register: | |||||||||
| 262 | OperandHash = Op.getReg(); | |||||||||
| 263 | break; | |||||||||
| 264 | case MachineOperand::MO_Immediate: | |||||||||
| 265 | OperandHash = Op.getImm(); | |||||||||
| 266 | break; | |||||||||
| 267 | case MachineOperand::MO_MachineBasicBlock: | |||||||||
| 268 | OperandHash = Op.getMBB()->getNumber(); | |||||||||
| 269 | break; | |||||||||
| 270 | case MachineOperand::MO_FrameIndex: | |||||||||
| 271 | case MachineOperand::MO_ConstantPoolIndex: | |||||||||
| 272 | case MachineOperand::MO_JumpTableIndex: | |||||||||
| 273 | OperandHash = Op.getIndex(); | |||||||||
| 274 | break; | |||||||||
| 275 | case MachineOperand::MO_GlobalAddress: | |||||||||
| 276 | case MachineOperand::MO_ExternalSymbol: | |||||||||
| 277 | // Global address / external symbol are too hard, don't bother, but do | |||||||||
| 278 | // pull in the offset. | |||||||||
| 279 | OperandHash = Op.getOffset(); | |||||||||
| 280 | break; | |||||||||
| 281 | default: | |||||||||
| 282 | break; | |||||||||
| 283 | } | |||||||||
| 284 | ||||||||||
| 285 | Hash += ((OperandHash << 3) | Op.getType()) << (i & 31); | |||||||||
| 286 | } | |||||||||
| 287 | return Hash; | |||||||||
| 288 | } | |||||||||
| 289 | ||||||||||
| 290 | /// HashEndOfMBB - Hash the last instruction in the MBB. | |||||||||
| 291 | static unsigned HashEndOfMBB(const MachineBasicBlock &MBB) { | |||||||||
| 292 | MachineBasicBlock::const_iterator I = MBB.getLastNonDebugInstr(); | |||||||||
| 293 | if (I == MBB.end()) | |||||||||
| 294 | return 0; | |||||||||
| 295 | ||||||||||
| 296 | return HashMachineInstr(*I); | |||||||||
| 297 | } | |||||||||
| 298 | ||||||||||
| 299 | /// ComputeCommonTailLength - Given two machine basic blocks, compute the number | |||||||||
| 300 | /// of instructions they actually have in common together at their end. Return | |||||||||
| 301 | /// iterators for the first shared instruction in each block. | |||||||||
| 302 | static unsigned ComputeCommonTailLength(MachineBasicBlock *MBB1, | |||||||||
| 303 | MachineBasicBlock *MBB2, | |||||||||
| 304 | MachineBasicBlock::iterator &I1, | |||||||||
| 305 | MachineBasicBlock::iterator &I2) { | |||||||||
| 306 | I1 = MBB1->end(); | |||||||||
| 307 | I2 = MBB2->end(); | |||||||||
| 308 | ||||||||||
| 309 | unsigned TailLen = 0; | |||||||||
| 310 | while (I1 != MBB1->begin() && I2 != MBB2->begin()) { | |||||||||
| 311 | --I1; --I2; | |||||||||
| 312 | // Skip debugging pseudos; necessary to avoid changing the code. | |||||||||
| 313 | while (I1->isDebugValue()) { | |||||||||
| 314 | if (I1==MBB1->begin()) { | |||||||||
| 315 | while (I2->isDebugValue()) { | |||||||||
| 316 | if (I2==MBB2->begin()) | |||||||||
| 317 | // I1==DBG at begin; I2==DBG at begin | |||||||||
| 318 | return TailLen; | |||||||||
| 319 | --I2; | |||||||||
| 320 | } | |||||||||
| 321 | ++I2; | |||||||||
| 322 | // I1==DBG at begin; I2==non-DBG, or first of DBGs not at begin | |||||||||
| 323 | return TailLen; | |||||||||
| 324 | } | |||||||||
| 325 | --I1; | |||||||||
| 326 | } | |||||||||
| 327 | // I1==first (untested) non-DBG preceding known match | |||||||||
| 328 | while (I2->isDebugValue()) { | |||||||||
| 329 | if (I2==MBB2->begin()) { | |||||||||
| 330 | ++I1; | |||||||||
| 331 | // I1==non-DBG, or first of DBGs not at begin; I2==DBG at begin | |||||||||
| 332 | return TailLen; | |||||||||
| 333 | } | |||||||||
| 334 | --I2; | |||||||||
| 335 | } | |||||||||
| 336 | // I1, I2==first (untested) non-DBGs preceding known match | |||||||||
| 337 | if (!I1->isIdenticalTo(*I2) || | |||||||||
| 338 | // FIXME: This check is dubious. It's used to get around a problem where | |||||||||
| 339 | // people incorrectly expect inline asm directives to remain in the same | |||||||||
| 340 | // relative order. This is untenable because normal compiler | |||||||||
| 341 | // optimizations (like this one) may reorder and/or merge these | |||||||||
| 342 | // directives. | |||||||||
| 343 | I1->isInlineAsm()) { | |||||||||
| 344 | ++I1; ++I2; | |||||||||
| 345 | break; | |||||||||
| 346 | } | |||||||||
| 347 | ++TailLen; | |||||||||
| 348 | } | |||||||||
| 349 | // Back past possible debugging pseudos at beginning of block. This matters | |||||||||
| 350 | // when one block differs from the other only by whether debugging pseudos | |||||||||
| 351 | // are present at the beginning. (This way, the various checks later for | |||||||||
| 352 | // I1==MBB1->begin() work as expected.) | |||||||||
| 353 | if (I1 == MBB1->begin() && I2 != MBB2->begin()) { | |||||||||
| 354 | --I2; | |||||||||
| 355 | while (I2->isDebugValue()) { | |||||||||
| 356 | if (I2 == MBB2->begin()) | |||||||||
| 357 | return TailLen; | |||||||||
| 358 | --I2; | |||||||||
| 359 | } | |||||||||
| 360 | ++I2; | |||||||||
| 361 | } | |||||||||
| 362 | if (I2 == MBB2->begin() && I1 != MBB1->begin()) { | |||||||||
| 363 | --I1; | |||||||||
| 364 | while (I1->isDebugValue()) { | |||||||||
| 365 | if (I1 == MBB1->begin()) | |||||||||
| 366 | return TailLen; | |||||||||
| 367 | --I1; | |||||||||
| 368 | } | |||||||||
| 369 | ++I1; | |||||||||
| 370 | } | |||||||||
| 371 | return TailLen; | |||||||||
| 372 | } | |||||||||
| 373 | ||||||||||
| 374 | void BranchFolder::replaceTailWithBranchTo(MachineBasicBlock::iterator OldInst, | |||||||||
| 375 | MachineBasicBlock &NewDest) { | |||||||||
| 376 | if (UpdateLiveIns) { | |||||||||
| 377 | // OldInst should always point to an instruction. | |||||||||
| 378 | MachineBasicBlock &OldMBB = *OldInst->getParent(); | |||||||||
| 379 | LiveRegs.clear(); | |||||||||
| 380 | LiveRegs.addLiveOuts(OldMBB); | |||||||||
| 381 | // Move backward to the place where will insert the jump. | |||||||||
| 382 | MachineBasicBlock::iterator I = OldMBB.end(); | |||||||||
| 383 | do { | |||||||||
| 384 | --I; | |||||||||
| 385 | LiveRegs.stepBackward(*I); | |||||||||
| 386 | } while (I != OldInst); | |||||||||
| 387 | ||||||||||
| 388 | // Merging the tails may have switched some undef operand to non-undef ones. | |||||||||
| 389 | // Add IMPLICIT_DEFS into OldMBB as necessary to have a definition of the | |||||||||
| 390 | // register. | |||||||||
| 391 | for (MachineBasicBlock::RegisterMaskPair P : NewDest.liveins()) { | |||||||||
| 392 | // We computed the liveins with computeLiveIn earlier and should only see | |||||||||
| 393 | // full registers: | |||||||||
| 394 | assert(P.LaneMask == LaneBitmask::getAll() &&(static_cast <bool> (P.LaneMask == LaneBitmask::getAll( ) && "Can only handle full register.") ? void (0) : __assert_fail ("P.LaneMask == LaneBitmask::getAll() && \"Can only handle full register.\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 395, __extension__ __PRETTY_FUNCTION__)) | |||||||||
| 395 | "Can only handle full register.")(static_cast <bool> (P.LaneMask == LaneBitmask::getAll( ) && "Can only handle full register.") ? void (0) : __assert_fail ("P.LaneMask == LaneBitmask::getAll() && \"Can only handle full register.\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 395, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 396 | MCPhysReg Reg = P.PhysReg; | |||||||||
| 397 | if (!LiveRegs.available(*MRI, Reg)) | |||||||||
| 398 | continue; | |||||||||
| 399 | DebugLoc DL; | |||||||||
| 400 | BuildMI(OldMBB, OldInst, DL, TII->get(TargetOpcode::IMPLICIT_DEF), Reg); | |||||||||
| 401 | } | |||||||||
| 402 | } | |||||||||
| 403 | ||||||||||
| 404 | TII->ReplaceTailWithBranchTo(OldInst, &NewDest); | |||||||||
| 405 | ++NumTailMerge; | |||||||||
| 406 | } | |||||||||
| 407 | ||||||||||
| 408 | MachineBasicBlock *BranchFolder::SplitMBBAt(MachineBasicBlock &CurMBB, | |||||||||
| 409 | MachineBasicBlock::iterator BBI1, | |||||||||
| 410 | const BasicBlock *BB) { | |||||||||
| 411 | if (!TII->isLegalToSplitMBBAt(CurMBB, BBI1)) | |||||||||
| 412 | return nullptr; | |||||||||
| 413 | ||||||||||
| 414 | MachineFunction &MF = *CurMBB.getParent(); | |||||||||
| 415 | ||||||||||
| 416 | // Create the fall-through block. | |||||||||
| 417 | MachineFunction::iterator MBBI = CurMBB.getIterator(); | |||||||||
| 418 | MachineBasicBlock *NewMBB = MF.CreateMachineBasicBlock(BB); | |||||||||
| 419 | CurMBB.getParent()->insert(++MBBI, NewMBB); | |||||||||
| 420 | ||||||||||
| 421 | // Move all the successors of this block to the specified block. | |||||||||
| 422 | NewMBB->transferSuccessors(&CurMBB); | |||||||||
| 423 | ||||||||||
| 424 | // Add an edge from CurMBB to NewMBB for the fall-through. | |||||||||
| 425 | CurMBB.addSuccessor(NewMBB); | |||||||||
| 426 | ||||||||||
| 427 | // Splice the code over. | |||||||||
| 428 | NewMBB->splice(NewMBB->end(), &CurMBB, BBI1, CurMBB.end()); | |||||||||
| 429 | ||||||||||
| 430 | // NewMBB belongs to the same loop as CurMBB. | |||||||||
| 431 | if (MLI) | |||||||||
| 432 | if (MachineLoop *ML = MLI->getLoopFor(&CurMBB)) | |||||||||
| 433 | ML->addBasicBlockToLoop(NewMBB, MLI->getBase()); | |||||||||
| 434 | ||||||||||
| 435 | // NewMBB inherits CurMBB's block frequency. | |||||||||
| 436 | MBBFreqInfo.setBlockFreq(NewMBB, MBBFreqInfo.getBlockFreq(&CurMBB)); | |||||||||
| 437 | ||||||||||
| 438 | if (UpdateLiveIns) | |||||||||
| 439 | computeAndAddLiveIns(LiveRegs, *NewMBB); | |||||||||
| 440 | ||||||||||
| 441 | // Add the new block to the funclet. | |||||||||
| 442 | const auto &FuncletI = FuncletMembership.find(&CurMBB); | |||||||||
| 443 | if (FuncletI != FuncletMembership.end()) { | |||||||||
| 444 | auto n = FuncletI->second; | |||||||||
| 445 | FuncletMembership[NewMBB] = n; | |||||||||
| 446 | } | |||||||||
| 447 | ||||||||||
| 448 | return NewMBB; | |||||||||
| 449 | } | |||||||||
| 450 | ||||||||||
| 451 | /// EstimateRuntime - Make a rough estimate for how long it will take to run | |||||||||
| 452 | /// the specified code. | |||||||||
| 453 | static unsigned EstimateRuntime(MachineBasicBlock::iterator I, | |||||||||
| 454 | MachineBasicBlock::iterator E) { | |||||||||
| 455 | unsigned Time = 0; | |||||||||
| 456 | for (; I != E; ++I) { | |||||||||
| 457 | if (I->isDebugValue()) | |||||||||
| 458 | continue; | |||||||||
| 459 | if (I->isCall()) | |||||||||
| 460 | Time += 10; | |||||||||
| 461 | else if (I->mayLoad() || I->mayStore()) | |||||||||
| 462 | Time += 2; | |||||||||
| 463 | else | |||||||||
| 464 | ++Time; | |||||||||
| 465 | } | |||||||||
| 466 | return Time; | |||||||||
| 467 | } | |||||||||
| 468 | ||||||||||
| 469 | // CurMBB needs to add an unconditional branch to SuccMBB (we removed these | |||||||||
| 470 | // branches temporarily for tail merging). In the case where CurMBB ends | |||||||||
| 471 | // with a conditional branch to the next block, optimize by reversing the | |||||||||
| 472 | // test and conditionally branching to SuccMBB instead. | |||||||||
| 473 | static void FixTail(MachineBasicBlock *CurMBB, MachineBasicBlock *SuccBB, | |||||||||
| 474 | const TargetInstrInfo *TII) { | |||||||||
| 475 | MachineFunction *MF = CurMBB->getParent(); | |||||||||
| 476 | MachineFunction::iterator I = std::next(MachineFunction::iterator(CurMBB)); | |||||||||
| 477 | MachineBasicBlock *TBB = nullptr, *FBB = nullptr; | |||||||||
| 478 | SmallVector<MachineOperand, 4> Cond; | |||||||||
| 479 | DebugLoc dl = CurMBB->findBranchDebugLoc(); | |||||||||
| 480 | if (I != MF->end() && !TII->analyzeBranch(*CurMBB, TBB, FBB, Cond, true)) { | |||||||||
| 481 | MachineBasicBlock *NextBB = &*I; | |||||||||
| 482 | if (TBB == NextBB && !Cond.empty() && !FBB) { | |||||||||
| 483 | if (!TII->reverseBranchCondition(Cond)) { | |||||||||
| 484 | TII->removeBranch(*CurMBB); | |||||||||
| 485 | TII->insertBranch(*CurMBB, SuccBB, nullptr, Cond, dl); | |||||||||
| 486 | return; | |||||||||
| 487 | } | |||||||||
| 488 | } | |||||||||
| 489 | } | |||||||||
| 490 | TII->insertBranch(*CurMBB, SuccBB, nullptr, | |||||||||
| 491 | SmallVector<MachineOperand, 0>(), dl); | |||||||||
| 492 | } | |||||||||
| 493 | ||||||||||
| 494 | bool | |||||||||
| 495 | BranchFolder::MergePotentialsElt::operator<(const MergePotentialsElt &o) const { | |||||||||
| 496 | if (getHash() < o.getHash()) | |||||||||
| 497 | return true; | |||||||||
| 498 | if (getHash() > o.getHash()) | |||||||||
| 499 | return false; | |||||||||
| 500 | if (getBlock()->getNumber() < o.getBlock()->getNumber()) | |||||||||
| 501 | return true; | |||||||||
| 502 | if (getBlock()->getNumber() > o.getBlock()->getNumber()) | |||||||||
| 503 | return false; | |||||||||
| 504 | // _GLIBCXX_DEBUG checks strict weak ordering, which involves comparing | |||||||||
| 505 | // an object with itself. | |||||||||
| 506 | #ifndef _GLIBCXX_DEBUG | |||||||||
| 507 | llvm_unreachable("Predecessor appears twice")::llvm::llvm_unreachable_internal("Predecessor appears twice" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 507); | |||||||||
| 508 | #else | |||||||||
| 509 | return false; | |||||||||
| 510 | #endif | |||||||||
| 511 | } | |||||||||
| 512 | ||||||||||
| 513 | BlockFrequency | |||||||||
| 514 | BranchFolder::MBFIWrapper::getBlockFreq(const MachineBasicBlock *MBB) const { | |||||||||
| 515 | auto I = MergedBBFreq.find(MBB); | |||||||||
| 516 | ||||||||||
| 517 | if (I != MergedBBFreq.end()) | |||||||||
| 518 | return I->second; | |||||||||
| 519 | ||||||||||
| 520 | return MBFI.getBlockFreq(MBB); | |||||||||
| 521 | } | |||||||||
| 522 | ||||||||||
| 523 | void BranchFolder::MBFIWrapper::setBlockFreq(const MachineBasicBlock *MBB, | |||||||||
| 524 | BlockFrequency F) { | |||||||||
| 525 | MergedBBFreq[MBB] = F; | |||||||||
| 526 | } | |||||||||
| 527 | ||||||||||
| 528 | raw_ostream & | |||||||||
| 529 | BranchFolder::MBFIWrapper::printBlockFreq(raw_ostream &OS, | |||||||||
| 530 | const MachineBasicBlock *MBB) const { | |||||||||
| 531 | return MBFI.printBlockFreq(OS, getBlockFreq(MBB)); | |||||||||
| 532 | } | |||||||||
| 533 | ||||||||||
| 534 | raw_ostream & | |||||||||
| 535 | BranchFolder::MBFIWrapper::printBlockFreq(raw_ostream &OS, | |||||||||
| 536 | const BlockFrequency Freq) const { | |||||||||
| 537 | return MBFI.printBlockFreq(OS, Freq); | |||||||||
| 538 | } | |||||||||
| 539 | ||||||||||
| 540 | void BranchFolder::MBFIWrapper::view(const Twine &Name, bool isSimple) { | |||||||||
| 541 | MBFI.view(Name, isSimple); | |||||||||
| 542 | } | |||||||||
| 543 | ||||||||||
| 544 | uint64_t | |||||||||
| 545 | BranchFolder::MBFIWrapper::getEntryFreq() const { | |||||||||
| 546 | return MBFI.getEntryFreq(); | |||||||||
| 547 | } | |||||||||
| 548 | ||||||||||
| 549 | /// CountTerminators - Count the number of terminators in the given | |||||||||
| 550 | /// block and set I to the position of the first non-terminator, if there | |||||||||
| 551 | /// is one, or MBB->end() otherwise. | |||||||||
| 552 | static unsigned CountTerminators(MachineBasicBlock *MBB, | |||||||||
| 553 | MachineBasicBlock::iterator &I) { | |||||||||
| 554 | I = MBB->end(); | |||||||||
| 555 | unsigned NumTerms = 0; | |||||||||
| 556 | while (true) { | |||||||||
| 557 | if (I == MBB->begin()) { | |||||||||
| 558 | I = MBB->end(); | |||||||||
| 559 | break; | |||||||||
| 560 | } | |||||||||
| 561 | --I; | |||||||||
| 562 | if (!I->isTerminator()) break; | |||||||||
| 563 | ++NumTerms; | |||||||||
| 564 | } | |||||||||
| 565 | return NumTerms; | |||||||||
| 566 | } | |||||||||
| 567 | ||||||||||
| 568 | /// A no successor, non-return block probably ends in unreachable and is cold. | |||||||||
| 569 | /// Also consider a block that ends in an indirect branch to be a return block, | |||||||||
| 570 | /// since many targets use plain indirect branches to return. | |||||||||
| 571 | static bool blockEndsInUnreachable(const MachineBasicBlock *MBB) { | |||||||||
| 572 | if (!MBB->succ_empty()) | |||||||||
| 573 | return false; | |||||||||
| 574 | if (MBB->empty()) | |||||||||
| 575 | return true; | |||||||||
| 576 | return !(MBB->back().isReturn() || MBB->back().isIndirectBranch()); | |||||||||
| 577 | } | |||||||||
| 578 | ||||||||||
| 579 | /// ProfitableToMerge - Check if two machine basic blocks have a common tail | |||||||||
| 580 | /// and decide if it would be profitable to merge those tails. Return the | |||||||||
| 581 | /// length of the common tail and iterators to the first common instruction | |||||||||
| 582 | /// in each block. | |||||||||
| 583 | /// MBB1, MBB2 The blocks to check | |||||||||
| 584 | /// MinCommonTailLength Minimum size of tail block to be merged. | |||||||||
| 585 | /// CommonTailLen Out parameter to record the size of the shared tail between | |||||||||
| 586 | /// MBB1 and MBB2 | |||||||||
| 587 | /// I1, I2 Iterator references that will be changed to point to the first | |||||||||
| 588 | /// instruction in the common tail shared by MBB1,MBB2 | |||||||||
| 589 | /// SuccBB A common successor of MBB1, MBB2 which are in a canonical form | |||||||||
| 590 | /// relative to SuccBB | |||||||||
| 591 | /// PredBB The layout predecessor of SuccBB, if any. | |||||||||
| 592 | /// FuncletMembership map from block to funclet #. | |||||||||
| 593 | /// AfterPlacement True if we are merging blocks after layout. Stricter | |||||||||
| 594 | /// thresholds apply to prevent undoing tail-duplication. | |||||||||
| 595 | static bool | |||||||||
| 596 | ProfitableToMerge(MachineBasicBlock *MBB1, MachineBasicBlock *MBB2, | |||||||||
| 597 | unsigned MinCommonTailLength, unsigned &CommonTailLen, | |||||||||
| 598 | MachineBasicBlock::iterator &I1, | |||||||||
| 599 | MachineBasicBlock::iterator &I2, MachineBasicBlock *SuccBB, | |||||||||
| 600 | MachineBasicBlock *PredBB, | |||||||||
| 601 | DenseMap<const MachineBasicBlock *, int> &FuncletMembership, | |||||||||
| 602 | bool AfterPlacement) { | |||||||||
| 603 | // It is never profitable to tail-merge blocks from two different funclets. | |||||||||
| 604 | if (!FuncletMembership.empty()) { | |||||||||
| 605 | auto Funclet1 = FuncletMembership.find(MBB1); | |||||||||
| 606 | assert(Funclet1 != FuncletMembership.end())(static_cast <bool> (Funclet1 != FuncletMembership.end( )) ? void (0) : __assert_fail ("Funclet1 != FuncletMembership.end()" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 606, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 607 | auto Funclet2 = FuncletMembership.find(MBB2); | |||||||||
| 608 | assert(Funclet2 != FuncletMembership.end())(static_cast <bool> (Funclet2 != FuncletMembership.end( )) ? void (0) : __assert_fail ("Funclet2 != FuncletMembership.end()" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 608, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 609 | if (Funclet1->second != Funclet2->second) | |||||||||
| 610 | return false; | |||||||||
| 611 | } | |||||||||
| 612 | ||||||||||
| 613 | CommonTailLen = ComputeCommonTailLength(MBB1, MBB2, I1, I2); | |||||||||
| 614 | if (CommonTailLen == 0) | |||||||||
| 615 | return false; | |||||||||
| 616 | DEBUG(dbgs() << "Common tail length of " << printMBBReference(*MBB1)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "Common tail length of " << printMBBReference(*MBB1) << " and " << printMBBReference (*MBB2) << " is " << CommonTailLen << '\n'; } } while (false) | |||||||||
| 617 | << " and " << printMBBReference(*MBB2) << " is " << CommonTailLendo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "Common tail length of " << printMBBReference(*MBB1) << " and " << printMBBReference (*MBB2) << " is " << CommonTailLen << '\n'; } } while (false) | |||||||||
| 618 | << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "Common tail length of " << printMBBReference(*MBB1) << " and " << printMBBReference (*MBB2) << " is " << CommonTailLen << '\n'; } } while (false); | |||||||||
| 619 | ||||||||||
| 620 | // It's almost always profitable to merge any number of non-terminator | |||||||||
| 621 | // instructions with the block that falls through into the common successor. | |||||||||
| 622 | // This is true only for a single successor. For multiple successors, we are | |||||||||
| 623 | // trading a conditional branch for an unconditional one. | |||||||||
| 624 | // TODO: Re-visit successor size for non-layout tail merging. | |||||||||
| 625 | if ((MBB1 == PredBB || MBB2 == PredBB) && | |||||||||
| 626 | (!AfterPlacement || MBB1->succ_size() == 1)) { | |||||||||
| 627 | MachineBasicBlock::iterator I; | |||||||||
| 628 | unsigned NumTerms = CountTerminators(MBB1 == PredBB ? MBB2 : MBB1, I); | |||||||||
| 629 | if (CommonTailLen > NumTerms) | |||||||||
| 630 | return true; | |||||||||
| 631 | } | |||||||||
| 632 | ||||||||||
| 633 | // If these are identical non-return blocks with no successors, merge them. | |||||||||
| 634 | // Such blocks are typically cold calls to noreturn functions like abort, and | |||||||||
| 635 | // are unlikely to become a fallthrough target after machine block placement. | |||||||||
| 636 | // Tail merging these blocks is unlikely to create additional unconditional | |||||||||
| 637 | // branches, and will reduce the size of this cold code. | |||||||||
| 638 | if (I1 == MBB1->begin() && I2 == MBB2->begin() && | |||||||||
| 639 | blockEndsInUnreachable(MBB1) && blockEndsInUnreachable(MBB2)) | |||||||||
| 640 | return true; | |||||||||
| 641 | ||||||||||
| 642 | // If one of the blocks can be completely merged and happens to be in | |||||||||
| 643 | // a position where the other could fall through into it, merge any number | |||||||||
| 644 | // of instructions, because it can be done without a branch. | |||||||||
| 645 | // TODO: If the blocks are not adjacent, move one of them so that they are? | |||||||||
| 646 | if (MBB1->isLayoutSuccessor(MBB2) && I2 == MBB2->begin()) | |||||||||
| 647 | return true; | |||||||||
| 648 | if (MBB2->isLayoutSuccessor(MBB1) && I1 == MBB1->begin()) | |||||||||
| 649 | return true; | |||||||||
| 650 | ||||||||||
| 651 | // If both blocks are identical and end in a branch, merge them unless they | |||||||||
| 652 | // both have a fallthrough predecessor and successor. | |||||||||
| 653 | // We can only do this after block placement because it depends on whether | |||||||||
| 654 | // there are fallthroughs, and we don't know until after layout. | |||||||||
| 655 | if (AfterPlacement && I1 == MBB1->begin() && I2 == MBB2->begin()) { | |||||||||
| 656 | auto BothFallThrough = [](MachineBasicBlock *MBB) { | |||||||||
| 657 | if (MBB->succ_size() != 0 && !MBB->canFallThrough()) | |||||||||
| 658 | return false; | |||||||||
| 659 | MachineFunction::iterator I(MBB); | |||||||||
| 660 | MachineFunction *MF = MBB->getParent(); | |||||||||
| 661 | return (MBB != &*MF->begin()) && std::prev(I)->canFallThrough(); | |||||||||
| 662 | }; | |||||||||
| 663 | if (!BothFallThrough(MBB1) || !BothFallThrough(MBB2)) | |||||||||
| 664 | return true; | |||||||||
| 665 | } | |||||||||
| 666 | ||||||||||
| 667 | // If both blocks have an unconditional branch temporarily stripped out, | |||||||||
| 668 | // count that as an additional common instruction for the following | |||||||||
| 669 | // heuristics. This heuristic is only accurate for single-succ blocks, so to | |||||||||
| 670 | // make sure that during layout merging and duplicating don't crash, we check | |||||||||
| 671 | // for that when merging during layout. | |||||||||
| 672 | unsigned EffectiveTailLen = CommonTailLen; | |||||||||
| 673 | if (SuccBB && MBB1 != PredBB && MBB2 != PredBB && | |||||||||
| 674 | (MBB1->succ_size() == 1 || !AfterPlacement) && | |||||||||
| 675 | !MBB1->back().isBarrier() && | |||||||||
| 676 | !MBB2->back().isBarrier()) | |||||||||
| 677 | ++EffectiveTailLen; | |||||||||
| 678 | ||||||||||
| 679 | // Check if the common tail is long enough to be worthwhile. | |||||||||
| 680 | if (EffectiveTailLen >= MinCommonTailLength) | |||||||||
| 681 | return true; | |||||||||
| 682 | ||||||||||
| 683 | // If we are optimizing for code size, 2 instructions in common is enough if | |||||||||
| 684 | // we don't have to split a block. At worst we will be introducing 1 new | |||||||||
| 685 | // branch instruction, which is likely to be smaller than the 2 | |||||||||
| 686 | // instructions that would be deleted in the merge. | |||||||||
| 687 | MachineFunction *MF = MBB1->getParent(); | |||||||||
| 688 | return EffectiveTailLen >= 2 && MF->getFunction().optForSize() && | |||||||||
| 689 | (I1 == MBB1->begin() || I2 == MBB2->begin()); | |||||||||
| 690 | } | |||||||||
| 691 | ||||||||||
| 692 | unsigned BranchFolder::ComputeSameTails(unsigned CurHash, | |||||||||
| 693 | unsigned MinCommonTailLength, | |||||||||
| 694 | MachineBasicBlock *SuccBB, | |||||||||
| 695 | MachineBasicBlock *PredBB) { | |||||||||
| 696 | unsigned maxCommonTailLength = 0U; | |||||||||
| 697 | SameTails.clear(); | |||||||||
| 698 | MachineBasicBlock::iterator TrialBBI1, TrialBBI2; | |||||||||
| 699 | MPIterator HighestMPIter = std::prev(MergePotentials.end()); | |||||||||
| 700 | for (MPIterator CurMPIter = std::prev(MergePotentials.end()), | |||||||||
| 701 | B = MergePotentials.begin(); | |||||||||
| 702 | CurMPIter != B && CurMPIter->getHash() == CurHash; --CurMPIter) { | |||||||||
| 703 | for (MPIterator I = std::prev(CurMPIter); I->getHash() == CurHash; --I) { | |||||||||
| 704 | unsigned CommonTailLen; | |||||||||
| 705 | if (ProfitableToMerge(CurMPIter->getBlock(), I->getBlock(), | |||||||||
| 706 | MinCommonTailLength, | |||||||||
| 707 | CommonTailLen, TrialBBI1, TrialBBI2, | |||||||||
| 708 | SuccBB, PredBB, | |||||||||
| 709 | FuncletMembership, | |||||||||
| 710 | AfterBlockPlacement)) { | |||||||||
| 711 | if (CommonTailLen > maxCommonTailLength) { | |||||||||
| 712 | SameTails.clear(); | |||||||||
| 713 | maxCommonTailLength = CommonTailLen; | |||||||||
| 714 | HighestMPIter = CurMPIter; | |||||||||
| 715 | SameTails.push_back(SameTailElt(CurMPIter, TrialBBI1)); | |||||||||
| 716 | } | |||||||||
| 717 | if (HighestMPIter == CurMPIter && | |||||||||
| 718 | CommonTailLen == maxCommonTailLength) | |||||||||
| 719 | SameTails.push_back(SameTailElt(I, TrialBBI2)); | |||||||||
| 720 | } | |||||||||
| 721 | if (I == B) | |||||||||
| 722 | break; | |||||||||
| 723 | } | |||||||||
| 724 | } | |||||||||
| 725 | return maxCommonTailLength; | |||||||||
| 726 | } | |||||||||
| 727 | ||||||||||
| 728 | void BranchFolder::RemoveBlocksWithHash(unsigned CurHash, | |||||||||
| 729 | MachineBasicBlock *SuccBB, | |||||||||
| 730 | MachineBasicBlock *PredBB) { | |||||||||
| 731 | MPIterator CurMPIter, B; | |||||||||
| 732 | for (CurMPIter = std::prev(MergePotentials.end()), | |||||||||
| 733 | B = MergePotentials.begin(); | |||||||||
| 734 | CurMPIter->getHash() == CurHash; --CurMPIter) { | |||||||||
| 735 | // Put the unconditional branch back, if we need one. | |||||||||
| 736 | MachineBasicBlock *CurMBB = CurMPIter->getBlock(); | |||||||||
| 737 | if (SuccBB && CurMBB != PredBB) | |||||||||
| 738 | FixTail(CurMBB, SuccBB, TII); | |||||||||
| 739 | if (CurMPIter == B) | |||||||||
| 740 | break; | |||||||||
| 741 | } | |||||||||
| 742 | if (CurMPIter->getHash() != CurHash) | |||||||||
| 743 | CurMPIter++; | |||||||||
| 744 | MergePotentials.erase(CurMPIter, MergePotentials.end()); | |||||||||
| 745 | } | |||||||||
| 746 | ||||||||||
| 747 | bool BranchFolder::CreateCommonTailOnlyBlock(MachineBasicBlock *&PredBB, | |||||||||
| 748 | MachineBasicBlock *SuccBB, | |||||||||
| 749 | unsigned maxCommonTailLength, | |||||||||
| 750 | unsigned &commonTailIndex) { | |||||||||
| 751 | commonTailIndex = 0; | |||||||||
| 752 | unsigned TimeEstimate = ~0U; | |||||||||
| 753 | for (unsigned i = 0, e = SameTails.size(); i != e; ++i) { | |||||||||
| 754 | // Use PredBB if possible; that doesn't require a new branch. | |||||||||
| 755 | if (SameTails[i].getBlock() == PredBB) { | |||||||||
| 756 | commonTailIndex = i; | |||||||||
| 757 | break; | |||||||||
| 758 | } | |||||||||
| 759 | // Otherwise, make a (fairly bogus) choice based on estimate of | |||||||||
| 760 | // how long it will take the various blocks to execute. | |||||||||
| 761 | unsigned t = EstimateRuntime(SameTails[i].getBlock()->begin(), | |||||||||
| 762 | SameTails[i].getTailStartPos()); | |||||||||
| 763 | if (t <= TimeEstimate) { | |||||||||
| 764 | TimeEstimate = t; | |||||||||
| 765 | commonTailIndex = i; | |||||||||
| 766 | } | |||||||||
| 767 | } | |||||||||
| 768 | ||||||||||
| 769 | MachineBasicBlock::iterator BBI = | |||||||||
| 770 | SameTails[commonTailIndex].getTailStartPos(); | |||||||||
| 771 | MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock(); | |||||||||
| 772 | ||||||||||
| 773 | DEBUG(dbgs() << "\nSplitting " << printMBBReference(*MBB) << ", size "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nSplitting " << printMBBReference (*MBB) << ", size " << maxCommonTailLength; } } while (false) | |||||||||
| 774 | << maxCommonTailLength)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nSplitting " << printMBBReference (*MBB) << ", size " << maxCommonTailLength; } } while (false); | |||||||||
| 775 | ||||||||||
| 776 | // If the split block unconditionally falls-thru to SuccBB, it will be | |||||||||
| 777 | // merged. In control flow terms it should then take SuccBB's name. e.g. If | |||||||||
| 778 | // SuccBB is an inner loop, the common tail is still part of the inner loop. | |||||||||
| 779 | const BasicBlock *BB = (SuccBB && MBB->succ_size() == 1) ? | |||||||||
| 780 | SuccBB->getBasicBlock() : MBB->getBasicBlock(); | |||||||||
| 781 | MachineBasicBlock *newMBB = SplitMBBAt(*MBB, BBI, BB); | |||||||||
| 782 | if (!newMBB) { | |||||||||
| 783 | DEBUG(dbgs() << "... failed!")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "... failed!"; } } while (false); | |||||||||
| 784 | return false; | |||||||||
| 785 | } | |||||||||
| 786 | ||||||||||
| 787 | SameTails[commonTailIndex].setBlock(newMBB); | |||||||||
| 788 | SameTails[commonTailIndex].setTailStartPos(newMBB->begin()); | |||||||||
| 789 | ||||||||||
| 790 | // If we split PredBB, newMBB is the new predecessor. | |||||||||
| 791 | if (PredBB == MBB) | |||||||||
| 792 | PredBB = newMBB; | |||||||||
| 793 | ||||||||||
| 794 | return true; | |||||||||
| 795 | } | |||||||||
| 796 | ||||||||||
| 797 | static void | |||||||||
| 798 | mergeOperations(MachineBasicBlock::iterator MBBIStartPos, | |||||||||
| 799 | MachineBasicBlock &MBBCommon) { | |||||||||
| 800 | MachineBasicBlock *MBB = MBBIStartPos->getParent(); | |||||||||
| 801 | // Note CommonTailLen does not necessarily matches the size of | |||||||||
| 802 | // the common BB nor all its instructions because of debug | |||||||||
| 803 | // instructions differences. | |||||||||
| 804 | unsigned CommonTailLen = 0; | |||||||||
| 805 | for (auto E = MBB->end(); MBBIStartPos != E; ++MBBIStartPos) | |||||||||
| 806 | ++CommonTailLen; | |||||||||
| 807 | ||||||||||
| 808 | MachineBasicBlock::reverse_iterator MBBI = MBB->rbegin(); | |||||||||
| 809 | MachineBasicBlock::reverse_iterator MBBIE = MBB->rend(); | |||||||||
| 810 | MachineBasicBlock::reverse_iterator MBBICommon = MBBCommon.rbegin(); | |||||||||
| 811 | MachineBasicBlock::reverse_iterator MBBIECommon = MBBCommon.rend(); | |||||||||
| 812 | ||||||||||
| 813 | while (CommonTailLen--) { | |||||||||
| 814 | assert(MBBI != MBBIE && "Reached BB end within common tail length!")(static_cast <bool> (MBBI != MBBIE && "Reached BB end within common tail length!" ) ? void (0) : __assert_fail ("MBBI != MBBIE && \"Reached BB end within common tail length!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 814, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 815 | (void)MBBIE; | |||||||||
| 816 | ||||||||||
| 817 | if (MBBI->isDebugValue()) { | |||||||||
| 818 | ++MBBI; | |||||||||
| 819 | continue; | |||||||||
| 820 | } | |||||||||
| 821 | ||||||||||
| 822 | while ((MBBICommon != MBBIECommon) && MBBICommon->isDebugValue()) | |||||||||
| 823 | ++MBBICommon; | |||||||||
| 824 | ||||||||||
| 825 | assert(MBBICommon != MBBIECommon &&(static_cast <bool> (MBBICommon != MBBIECommon && "Reached BB end within common tail length!") ? void (0) : __assert_fail ("MBBICommon != MBBIECommon && \"Reached BB end within common tail length!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 826, __extension__ __PRETTY_FUNCTION__)) | |||||||||
| 826 | "Reached BB end within common tail length!")(static_cast <bool> (MBBICommon != MBBIECommon && "Reached BB end within common tail length!") ? void (0) : __assert_fail ("MBBICommon != MBBIECommon && \"Reached BB end within common tail length!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 826, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 827 | assert(MBBICommon->isIdenticalTo(*MBBI) && "Expected matching MIIs!")(static_cast <bool> (MBBICommon->isIdenticalTo(*MBBI ) && "Expected matching MIIs!") ? void (0) : __assert_fail ("MBBICommon->isIdenticalTo(*MBBI) && \"Expected matching MIIs!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 827, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 828 | ||||||||||
| 829 | // Merge MMOs from memory operations in the common block. | |||||||||
| 830 | if (MBBICommon->mayLoad() || MBBICommon->mayStore()) | |||||||||
| 831 | MBBICommon->setMemRefs(MBBICommon->mergeMemRefsWith(*MBBI)); | |||||||||
| 832 | // Drop undef flags if they aren't present in all merged instructions. | |||||||||
| 833 | for (unsigned I = 0, E = MBBICommon->getNumOperands(); I != E; ++I) { | |||||||||
| 834 | MachineOperand &MO = MBBICommon->getOperand(I); | |||||||||
| 835 | if (MO.isReg() && MO.isUndef()) { | |||||||||
| 836 | const MachineOperand &OtherMO = MBBI->getOperand(I); | |||||||||
| 837 | if (!OtherMO.isUndef()) | |||||||||
| 838 | MO.setIsUndef(false); | |||||||||
| 839 | } | |||||||||
| 840 | } | |||||||||
| 841 | ||||||||||
| 842 | ++MBBI; | |||||||||
| 843 | ++MBBICommon; | |||||||||
| 844 | } | |||||||||
| 845 | } | |||||||||
| 846 | ||||||||||
| 847 | void BranchFolder::mergeCommonTails(unsigned commonTailIndex) { | |||||||||
| 848 | MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock(); | |||||||||
| 849 | ||||||||||
| 850 | std::vector<MachineBasicBlock::iterator> NextCommonInsts(SameTails.size()); | |||||||||
| 851 | for (unsigned int i = 0 ; i != SameTails.size() ; ++i) { | |||||||||
| 852 | if (i != commonTailIndex) { | |||||||||
| 853 | NextCommonInsts[i] = SameTails[i].getTailStartPos(); | |||||||||
| 854 | mergeOperations(SameTails[i].getTailStartPos(), *MBB); | |||||||||
| 855 | } else { | |||||||||
| 856 | assert(SameTails[i].getTailStartPos() == MBB->begin() &&(static_cast <bool> (SameTails[i].getTailStartPos() == MBB ->begin() && "MBB is not a common tail only block" ) ? void (0) : __assert_fail ("SameTails[i].getTailStartPos() == MBB->begin() && \"MBB is not a common tail only block\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 857, __extension__ __PRETTY_FUNCTION__)) | |||||||||
| 857 | "MBB is not a common tail only block")(static_cast <bool> (SameTails[i].getTailStartPos() == MBB ->begin() && "MBB is not a common tail only block" ) ? void (0) : __assert_fail ("SameTails[i].getTailStartPos() == MBB->begin() && \"MBB is not a common tail only block\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 857, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 858 | } | |||||||||
| 859 | } | |||||||||
| 860 | ||||||||||
| 861 | for (auto &MI : *MBB) { | |||||||||
| 862 | if (MI.isDebugValue()) | |||||||||
| 863 | continue; | |||||||||
| 864 | DebugLoc DL = MI.getDebugLoc(); | |||||||||
| 865 | for (unsigned int i = 0 ; i < NextCommonInsts.size() ; i++) { | |||||||||
| 866 | if (i == commonTailIndex) | |||||||||
| 867 | continue; | |||||||||
| 868 | ||||||||||
| 869 | auto &Pos = NextCommonInsts[i]; | |||||||||
| 870 | assert(Pos != SameTails[i].getBlock()->end() &&(static_cast <bool> (Pos != SameTails[i].getBlock()-> end() && "Reached BB end within common tail") ? void ( 0) : __assert_fail ("Pos != SameTails[i].getBlock()->end() && \"Reached BB end within common tail\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 871, __extension__ __PRETTY_FUNCTION__)) | |||||||||
| 871 | "Reached BB end within common tail")(static_cast <bool> (Pos != SameTails[i].getBlock()-> end() && "Reached BB end within common tail") ? void ( 0) : __assert_fail ("Pos != SameTails[i].getBlock()->end() && \"Reached BB end within common tail\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 871, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 872 | while (Pos->isDebugValue()) { | |||||||||
| 873 | ++Pos; | |||||||||
| 874 | assert(Pos != SameTails[i].getBlock()->end() &&(static_cast <bool> (Pos != SameTails[i].getBlock()-> end() && "Reached BB end within common tail") ? void ( 0) : __assert_fail ("Pos != SameTails[i].getBlock()->end() && \"Reached BB end within common tail\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 875, __extension__ __PRETTY_FUNCTION__)) | |||||||||
| 875 | "Reached BB end within common tail")(static_cast <bool> (Pos != SameTails[i].getBlock()-> end() && "Reached BB end within common tail") ? void ( 0) : __assert_fail ("Pos != SameTails[i].getBlock()->end() && \"Reached BB end within common tail\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 875, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 876 | } | |||||||||
| 877 | assert(MI.isIdenticalTo(*Pos) && "Expected matching MIIs!")(static_cast <bool> (MI.isIdenticalTo(*Pos) && "Expected matching MIIs!" ) ? void (0) : __assert_fail ("MI.isIdenticalTo(*Pos) && \"Expected matching MIIs!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 877, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 878 | DL = DILocation::getMergedLocation(DL, Pos->getDebugLoc()); | |||||||||
| 879 | NextCommonInsts[i] = ++Pos; | |||||||||
| 880 | } | |||||||||
| 881 | MI.setDebugLoc(DL); | |||||||||
| 882 | } | |||||||||
| 883 | ||||||||||
| 884 | if (UpdateLiveIns) { | |||||||||
| 885 | LivePhysRegs NewLiveIns(*TRI); | |||||||||
| 886 | computeLiveIns(NewLiveIns, *MBB); | |||||||||
| 887 | ||||||||||
| 888 | // The flag merging may lead to some register uses no longer using the | |||||||||
| 889 | // <undef> flag, add IMPLICIT_DEFs in the predecessors as necessary. | |||||||||
| 890 | for (MachineBasicBlock *Pred : MBB->predecessors()) { | |||||||||
| 891 | LiveRegs.init(*TRI); | |||||||||
| 892 | LiveRegs.addLiveOuts(*Pred); | |||||||||
| 893 | MachineBasicBlock::iterator InsertBefore = Pred->getFirstTerminator(); | |||||||||
| 894 | for (unsigned Reg : NewLiveIns) { | |||||||||
| 895 | if (!LiveRegs.available(*MRI, Reg)) | |||||||||
| 896 | continue; | |||||||||
| 897 | DebugLoc DL; | |||||||||
| 898 | BuildMI(*Pred, InsertBefore, DL, TII->get(TargetOpcode::IMPLICIT_DEF), | |||||||||
| 899 | Reg); | |||||||||
| 900 | } | |||||||||
| 901 | } | |||||||||
| 902 | ||||||||||
| 903 | MBB->clearLiveIns(); | |||||||||
| 904 | addLiveIns(*MBB, NewLiveIns); | |||||||||
| 905 | } | |||||||||
| 906 | } | |||||||||
| 907 | ||||||||||
| 908 | // See if any of the blocks in MergePotentials (which all have SuccBB as a | |||||||||
| 909 | // successor, or all have no successor if it is null) can be tail-merged. | |||||||||
| 910 | // If there is a successor, any blocks in MergePotentials that are not | |||||||||
| 911 | // tail-merged and are not immediately before Succ must have an unconditional | |||||||||
| 912 | // branch to Succ added (but the predecessor/successor lists need no | |||||||||
| 913 | // adjustment). The lone predecessor of Succ that falls through into Succ, | |||||||||
| 914 | // if any, is given in PredBB. | |||||||||
| 915 | // MinCommonTailLength - Except for the special cases below, tail-merge if | |||||||||
| 916 | // there are at least this many instructions in common. | |||||||||
| 917 | bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB, | |||||||||
| 918 | MachineBasicBlock *PredBB, | |||||||||
| 919 | unsigned MinCommonTailLength) { | |||||||||
| 920 | bool MadeChange = false; | |||||||||
| 921 | ||||||||||
| 922 | DEBUG(dbgs() << "\nTryTailMergeBlocks: ";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nTryTailMergeBlocks: " ; for (unsigned i = 0, e = MergePotentials.size(); i != e; ++ i) dbgs() << printMBBReference(*MergePotentials[i].getBlock ()) << (i == e - 1 ? "" : ", "); dbgs() << "\n"; if (SuccBB) { dbgs() << " with successor " << printMBBReference (*SuccBB) << '\n'; if (PredBB) dbgs() << " which has fall-through from " << printMBBReference(*PredBB) << "\n"; } dbgs() << "Looking for common tails of at least " << MinCommonTailLength << " instruction" << (MinCommonTailLength == 1 ? "" : "s") << '\n';; } } while (false) | |||||||||
| 923 | for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i) dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nTryTailMergeBlocks: " ; for (unsigned i = 0, e = MergePotentials.size(); i != e; ++ i) dbgs() << printMBBReference(*MergePotentials[i].getBlock ()) << (i == e - 1 ? "" : ", "); dbgs() << "\n"; if (SuccBB) { dbgs() << " with successor " << printMBBReference (*SuccBB) << '\n'; if (PredBB) dbgs() << " which has fall-through from " << printMBBReference(*PredBB) << "\n"; } dbgs() << "Looking for common tails of at least " << MinCommonTailLength << " instruction" << (MinCommonTailLength == 1 ? "" : "s") << '\n';; } } while (false) | |||||||||
| 924 | << printMBBReference(*MergePotentials[i].getBlock())do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nTryTailMergeBlocks: " ; for (unsigned i = 0, e = MergePotentials.size(); i != e; ++ i) dbgs() << printMBBReference(*MergePotentials[i].getBlock ()) << (i == e - 1 ? "" : ", "); dbgs() << "\n"; if (SuccBB) { dbgs() << " with successor " << printMBBReference (*SuccBB) << '\n'; if (PredBB) dbgs() << " which has fall-through from " << printMBBReference(*PredBB) << "\n"; } dbgs() << "Looking for common tails of at least " << MinCommonTailLength << " instruction" << (MinCommonTailLength == 1 ? "" : "s") << '\n';; } } while (false) | |||||||||
| 925 | << (i == e - 1 ? "" : ", ");do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nTryTailMergeBlocks: " ; for (unsigned i = 0, e = MergePotentials.size(); i != e; ++ i) dbgs() << printMBBReference(*MergePotentials[i].getBlock ()) << (i == e - 1 ? "" : ", "); dbgs() << "\n"; if (SuccBB) { dbgs() << " with successor " << printMBBReference (*SuccBB) << '\n'; if (PredBB) dbgs() << " which has fall-through from " << printMBBReference(*PredBB) << "\n"; } dbgs() << "Looking for common tails of at least " << MinCommonTailLength << " instruction" << (MinCommonTailLength == 1 ? "" : "s") << '\n';; } } while (false) | |||||||||
| 926 | dbgs() << "\n"; if (SuccBB) {do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nTryTailMergeBlocks: " ; for (unsigned i = 0, e = MergePotentials.size(); i != e; ++ i) dbgs() << printMBBReference(*MergePotentials[i].getBlock ()) << (i == e - 1 ? "" : ", "); dbgs() << "\n"; if (SuccBB) { dbgs() << " with successor " << printMBBReference (*SuccBB) << '\n'; if (PredBB) dbgs() << " which has fall-through from " << printMBBReference(*PredBB) << "\n"; } dbgs() << "Looking for common tails of at least " << MinCommonTailLength << " instruction" << (MinCommonTailLength == 1 ? "" : "s") << '\n';; } } while (false) | |||||||||
| 927 | dbgs() << " with successor " << printMBBReference(*SuccBB) << '\n';do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nTryTailMergeBlocks: " ; for (unsigned i = 0, e = MergePotentials.size(); i != e; ++ i) dbgs() << printMBBReference(*MergePotentials[i].getBlock ()) << (i == e - 1 ? "" : ", "); dbgs() << "\n"; if (SuccBB) { dbgs() << " with successor " << printMBBReference (*SuccBB) << '\n'; if (PredBB) dbgs() << " which has fall-through from " << printMBBReference(*PredBB) << "\n"; } dbgs() << "Looking for common tails of at least " << MinCommonTailLength << " instruction" << (MinCommonTailLength == 1 ? "" : "s") << '\n';; } } while (false) | |||||||||
| 928 | if (PredBB)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nTryTailMergeBlocks: " ; for (unsigned i = 0, e = MergePotentials.size(); i != e; ++ i) dbgs() << printMBBReference(*MergePotentials[i].getBlock ()) << (i == e - 1 ? "" : ", "); dbgs() << "\n"; if (SuccBB) { dbgs() << " with successor " << printMBBReference (*SuccBB) << '\n'; if (PredBB) dbgs() << " which has fall-through from " << printMBBReference(*PredBB) << "\n"; } dbgs() << "Looking for common tails of at least " << MinCommonTailLength << " instruction" << (MinCommonTailLength == 1 ? "" : "s") << '\n';; } } while (false) | |||||||||
| 929 | dbgs() << " which has fall-through from "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nTryTailMergeBlocks: " ; for (unsigned i = 0, e = MergePotentials.size(); i != e; ++ i) dbgs() << printMBBReference(*MergePotentials[i].getBlock ()) << (i == e - 1 ? "" : ", "); dbgs() << "\n"; if (SuccBB) { dbgs() << " with successor " << printMBBReference (*SuccBB) << '\n'; if (PredBB) dbgs() << " which has fall-through from " << printMBBReference(*PredBB) << "\n"; } dbgs() << "Looking for common tails of at least " << MinCommonTailLength << " instruction" << (MinCommonTailLength == 1 ? "" : "s") << '\n';; } } while (false) | |||||||||
| 930 | << printMBBReference(*PredBB) << "\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nTryTailMergeBlocks: " ; for (unsigned i = 0, e = MergePotentials.size(); i != e; ++ i) dbgs() << printMBBReference(*MergePotentials[i].getBlock ()) << (i == e - 1 ? "" : ", "); dbgs() << "\n"; if (SuccBB) { dbgs() << " with successor " << printMBBReference (*SuccBB) << '\n'; if (PredBB) dbgs() << " which has fall-through from " << printMBBReference(*PredBB) << "\n"; } dbgs() << "Looking for common tails of at least " << MinCommonTailLength << " instruction" << (MinCommonTailLength == 1 ? "" : "s") << '\n';; } } while (false) | |||||||||
| 931 | } dbgs() << "Looking for common tails of at least "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nTryTailMergeBlocks: " ; for (unsigned i = 0, e = MergePotentials.size(); i != e; ++ i) dbgs() << printMBBReference(*MergePotentials[i].getBlock ()) << (i == e - 1 ? "" : ", "); dbgs() << "\n"; if (SuccBB) { dbgs() << " with successor " << printMBBReference (*SuccBB) << '\n'; if (PredBB) dbgs() << " which has fall-through from " << printMBBReference(*PredBB) << "\n"; } dbgs() << "Looking for common tails of at least " << MinCommonTailLength << " instruction" << (MinCommonTailLength == 1 ? "" : "s") << '\n';; } } while (false) | |||||||||
| 932 | << MinCommonTailLength << " instruction"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nTryTailMergeBlocks: " ; for (unsigned i = 0, e = MergePotentials.size(); i != e; ++ i) dbgs() << printMBBReference(*MergePotentials[i].getBlock ()) << (i == e - 1 ? "" : ", "); dbgs() << "\n"; if (SuccBB) { dbgs() << " with successor " << printMBBReference (*SuccBB) << '\n'; if (PredBB) dbgs() << " which has fall-through from " << printMBBReference(*PredBB) << "\n"; } dbgs() << "Looking for common tails of at least " << MinCommonTailLength << " instruction" << (MinCommonTailLength == 1 ? "" : "s") << '\n';; } } while (false) | |||||||||
| 933 | << (MinCommonTailLength == 1 ? "" : "s") << '\n';)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nTryTailMergeBlocks: " ; for (unsigned i = 0, e = MergePotentials.size(); i != e; ++ i) dbgs() << printMBBReference(*MergePotentials[i].getBlock ()) << (i == e - 1 ? "" : ", "); dbgs() << "\n"; if (SuccBB) { dbgs() << " with successor " << printMBBReference (*SuccBB) << '\n'; if (PredBB) dbgs() << " which has fall-through from " << printMBBReference(*PredBB) << "\n"; } dbgs() << "Looking for common tails of at least " << MinCommonTailLength << " instruction" << (MinCommonTailLength == 1 ? "" : "s") << '\n';; } } while (false); | |||||||||
| 934 | ||||||||||
| 935 | // Sort by hash value so that blocks with identical end sequences sort | |||||||||
| 936 | // together. | |||||||||
| 937 | array_pod_sort(MergePotentials.begin(), MergePotentials.end()); | |||||||||
| 938 | ||||||||||
| 939 | // Walk through equivalence sets looking for actual exact matches. | |||||||||
| 940 | while (MergePotentials.size() > 1) { | |||||||||
| 941 | unsigned CurHash = MergePotentials.back().getHash(); | |||||||||
| 942 | ||||||||||
| 943 | // Build SameTails, identifying the set of blocks with this hash code | |||||||||
| 944 | // and with the maximum number of instructions in common. | |||||||||
| 945 | unsigned maxCommonTailLength = ComputeSameTails(CurHash, | |||||||||
| 946 | MinCommonTailLength, | |||||||||
| 947 | SuccBB, PredBB); | |||||||||
| 948 | ||||||||||
| 949 | // If we didn't find any pair that has at least MinCommonTailLength | |||||||||
| 950 | // instructions in common, remove all blocks with this hash code and retry. | |||||||||
| 951 | if (SameTails.empty()) { | |||||||||
| 952 | RemoveBlocksWithHash(CurHash, SuccBB, PredBB); | |||||||||
| 953 | continue; | |||||||||
| 954 | } | |||||||||
| 955 | ||||||||||
| 956 | // If one of the blocks is the entire common tail (and not the entry | |||||||||
| 957 | // block, which we can't jump to), we can treat all blocks with this same | |||||||||
| 958 | // tail at once. Use PredBB if that is one of the possibilities, as that | |||||||||
| 959 | // will not introduce any extra branches. | |||||||||
| 960 | MachineBasicBlock *EntryBB = | |||||||||
| 961 | &MergePotentials.front().getBlock()->getParent()->front(); | |||||||||
| 962 | unsigned commonTailIndex = SameTails.size(); | |||||||||
| 963 | // If there are two blocks, check to see if one can be made to fall through | |||||||||
| 964 | // into the other. | |||||||||
| 965 | if (SameTails.size() == 2 && | |||||||||
| 966 | SameTails[0].getBlock()->isLayoutSuccessor(SameTails[1].getBlock()) && | |||||||||
| 967 | SameTails[1].tailIsWholeBlock()) | |||||||||
| 968 | commonTailIndex = 1; | |||||||||
| 969 | else if (SameTails.size() == 2 && | |||||||||
| 970 | SameTails[1].getBlock()->isLayoutSuccessor( | |||||||||
| 971 | SameTails[0].getBlock()) && | |||||||||
| 972 | SameTails[0].tailIsWholeBlock()) | |||||||||
| 973 | commonTailIndex = 0; | |||||||||
| 974 | else { | |||||||||
| 975 | // Otherwise just pick one, favoring the fall-through predecessor if | |||||||||
| 976 | // there is one. | |||||||||
| 977 | for (unsigned i = 0, e = SameTails.size(); i != e; ++i) { | |||||||||
| 978 | MachineBasicBlock *MBB = SameTails[i].getBlock(); | |||||||||
| 979 | if (MBB == EntryBB && SameTails[i].tailIsWholeBlock()) | |||||||||
| 980 | continue; | |||||||||
| 981 | if (MBB == PredBB) { | |||||||||
| 982 | commonTailIndex = i; | |||||||||
| 983 | break; | |||||||||
| 984 | } | |||||||||
| 985 | if (SameTails[i].tailIsWholeBlock()) | |||||||||
| 986 | commonTailIndex = i; | |||||||||
| 987 | } | |||||||||
| 988 | } | |||||||||
| 989 | ||||||||||
| 990 | if (commonTailIndex == SameTails.size() || | |||||||||
| 991 | (SameTails[commonTailIndex].getBlock() == PredBB && | |||||||||
| 992 | !SameTails[commonTailIndex].tailIsWholeBlock())) { | |||||||||
| 993 | // None of the blocks consist entirely of the common tail. | |||||||||
| 994 | // Split a block so that one does. | |||||||||
| 995 | if (!CreateCommonTailOnlyBlock(PredBB, SuccBB, | |||||||||
| 996 | maxCommonTailLength, commonTailIndex)) { | |||||||||
| 997 | RemoveBlocksWithHash(CurHash, SuccBB, PredBB); | |||||||||
| 998 | continue; | |||||||||
| 999 | } | |||||||||
| 1000 | } | |||||||||
| 1001 | ||||||||||
| 1002 | MachineBasicBlock *MBB = SameTails[commonTailIndex].getBlock(); | |||||||||
| 1003 | ||||||||||
| 1004 | // Recompute common tail MBB's edge weights and block frequency. | |||||||||
| 1005 | setCommonTailEdgeWeights(*MBB); | |||||||||
| 1006 | ||||||||||
| 1007 | // Merge debug locations, MMOs and undef flags across identical instructions | |||||||||
| 1008 | // for common tail. | |||||||||
| 1009 | mergeCommonTails(commonTailIndex); | |||||||||
| 1010 | ||||||||||
| 1011 | // MBB is common tail. Adjust all other BB's to jump to this one. | |||||||||
| 1012 | // Traversal must be forwards so erases work. | |||||||||
| 1013 | DEBUG(dbgs() << "\nUsing common tail in " << printMBBReference(*MBB)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nUsing common tail in " << printMBBReference(*MBB) << " for "; } } while (false) | |||||||||
| 1014 | << " for ")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nUsing common tail in " << printMBBReference(*MBB) << " for "; } } while (false); | |||||||||
| 1015 | for (unsigned int i=0, e = SameTails.size(); i != e; ++i) { | |||||||||
| 1016 | if (commonTailIndex == i) | |||||||||
| 1017 | continue; | |||||||||
| 1018 | DEBUG(dbgs() << printMBBReference(*SameTails[i].getBlock())do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << printMBBReference(*SameTails [i].getBlock()) << (i == e - 1 ? "" : ", "); } } while ( false) | |||||||||
| 1019 | << (i == e - 1 ? "" : ", "))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << printMBBReference(*SameTails [i].getBlock()) << (i == e - 1 ? "" : ", "); } } while ( false); | |||||||||
| 1020 | // Hack the end off BB i, making it jump to BB commonTailIndex instead. | |||||||||
| 1021 | replaceTailWithBranchTo(SameTails[i].getTailStartPos(), *MBB); | |||||||||
| 1022 | // BB i is no longer a predecessor of SuccBB; remove it from the worklist. | |||||||||
| 1023 | MergePotentials.erase(SameTails[i].getMPIter()); | |||||||||
| 1024 | } | |||||||||
| 1025 | DEBUG(dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\n"; } } while (false); | |||||||||
| 1026 | // We leave commonTailIndex in the worklist in case there are other blocks | |||||||||
| 1027 | // that match it with a smaller number of instructions. | |||||||||
| 1028 | MadeChange = true; | |||||||||
| 1029 | } | |||||||||
| 1030 | return MadeChange; | |||||||||
| 1031 | } | |||||||||
| 1032 | ||||||||||
| 1033 | bool BranchFolder::TailMergeBlocks(MachineFunction &MF) { | |||||||||
| 1034 | bool MadeChange = false; | |||||||||
| 1035 | if (!EnableTailMerge) return MadeChange; | |||||||||
| 1036 | ||||||||||
| 1037 | // First find blocks with no successors. | |||||||||
| 1038 | // Block placement does not create new tail merging opportunities for these | |||||||||
| 1039 | // blocks. | |||||||||
| 1040 | if (!AfterBlockPlacement) { | |||||||||
| 1041 | MergePotentials.clear(); | |||||||||
| 1042 | for (MachineBasicBlock &MBB : MF) { | |||||||||
| 1043 | if (MergePotentials.size() == TailMergeThreshold) | |||||||||
| 1044 | break; | |||||||||
| 1045 | if (!TriedMerging.count(&MBB) && MBB.succ_empty()) | |||||||||
| 1046 | MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(MBB), &MBB)); | |||||||||
| 1047 | } | |||||||||
| 1048 | ||||||||||
| 1049 | // If this is a large problem, avoid visiting the same basic blocks | |||||||||
| 1050 | // multiple times. | |||||||||
| 1051 | if (MergePotentials.size() == TailMergeThreshold) | |||||||||
| 1052 | for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i) | |||||||||
| 1053 | TriedMerging.insert(MergePotentials[i].getBlock()); | |||||||||
| 1054 | ||||||||||
| 1055 | // See if we can do any tail merging on those. | |||||||||
| 1056 | if (MergePotentials.size() >= 2) | |||||||||
| 1057 | MadeChange |= TryTailMergeBlocks(nullptr, nullptr, MinCommonTailLength); | |||||||||
| 1058 | } | |||||||||
| 1059 | ||||||||||
| 1060 | // Look at blocks (IBB) with multiple predecessors (PBB). | |||||||||
| 1061 | // We change each predecessor to a canonical form, by | |||||||||
| 1062 | // (1) temporarily removing any unconditional branch from the predecessor | |||||||||
| 1063 | // to IBB, and | |||||||||
| 1064 | // (2) alter conditional branches so they branch to the other block | |||||||||
| 1065 | // not IBB; this may require adding back an unconditional branch to IBB | |||||||||
| 1066 | // later, where there wasn't one coming in. E.g. | |||||||||
| 1067 | // Bcc IBB | |||||||||
| 1068 | // fallthrough to QBB | |||||||||
| 1069 | // here becomes | |||||||||
| 1070 | // Bncc QBB | |||||||||
| 1071 | // with a conceptual B to IBB after that, which never actually exists. | |||||||||
| 1072 | // With those changes, we see whether the predecessors' tails match, | |||||||||
| 1073 | // and merge them if so. We change things out of canonical form and | |||||||||
| 1074 | // back to the way they were later in the process. (OptimizeBranches | |||||||||
| 1075 | // would undo some of this, but we can't use it, because we'd get into | |||||||||
| 1076 | // a compile-time infinite loop repeatedly doing and undoing the same | |||||||||
| 1077 | // transformations.) | |||||||||
| 1078 | ||||||||||
| 1079 | for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end(); | |||||||||
| 1080 | I != E; ++I) { | |||||||||
| 1081 | if (I->pred_size() < 2) continue; | |||||||||
| 1082 | SmallPtrSet<MachineBasicBlock *, 8> UniquePreds; | |||||||||
| 1083 | MachineBasicBlock *IBB = &*I; | |||||||||
| 1084 | MachineBasicBlock *PredBB = &*std::prev(I); | |||||||||
| 1085 | MergePotentials.clear(); | |||||||||
| 1086 | MachineLoop *ML; | |||||||||
| 1087 | ||||||||||
| 1088 | // Bail if merging after placement and IBB is the loop header because | |||||||||
| 1089 | // -- If merging predecessors that belong to the same loop as IBB, the | |||||||||
| 1090 | // common tail of merged predecessors may become the loop top if block | |||||||||
| 1091 | // placement is called again and the predecessors may branch to this common | |||||||||
| 1092 | // tail and require more branches. This can be relaxed if | |||||||||
| 1093 | // MachineBlockPlacement::findBestLoopTop is more flexible. | |||||||||
| 1094 | // --If merging predecessors that do not belong to the same loop as IBB, the | |||||||||
| 1095 | // loop info of IBB's loop and the other loops may be affected. Calling the | |||||||||
| 1096 | // block placement again may make big change to the layout and eliminate the | |||||||||
| 1097 | // reason to do tail merging here. | |||||||||
| 1098 | if (AfterBlockPlacement && MLI) { | |||||||||
| 1099 | ML = MLI->getLoopFor(IBB); | |||||||||
| 1100 | if (ML && IBB == ML->getHeader()) | |||||||||
| 1101 | continue; | |||||||||
| 1102 | } | |||||||||
| 1103 | ||||||||||
| 1104 | for (MachineBasicBlock *PBB : I->predecessors()) { | |||||||||
| 1105 | if (MergePotentials.size() == TailMergeThreshold) | |||||||||
| 1106 | break; | |||||||||
| 1107 | ||||||||||
| 1108 | if (TriedMerging.count(PBB)) | |||||||||
| 1109 | continue; | |||||||||
| 1110 | ||||||||||
| 1111 | // Skip blocks that loop to themselves, can't tail merge these. | |||||||||
| 1112 | if (PBB == IBB) | |||||||||
| 1113 | continue; | |||||||||
| 1114 | ||||||||||
| 1115 | // Visit each predecessor only once. | |||||||||
| 1116 | if (!UniquePreds.insert(PBB).second) | |||||||||
| 1117 | continue; | |||||||||
| 1118 | ||||||||||
| 1119 | // Skip blocks which may jump to a landing pad. Can't tail merge these. | |||||||||
| 1120 | if (PBB->hasEHPadSuccessor()) | |||||||||
| 1121 | continue; | |||||||||
| 1122 | ||||||||||
| 1123 | // After block placement, only consider predecessors that belong to the | |||||||||
| 1124 | // same loop as IBB. The reason is the same as above when skipping loop | |||||||||
| 1125 | // header. | |||||||||
| 1126 | if (AfterBlockPlacement && MLI) | |||||||||
| 1127 | if (ML != MLI->getLoopFor(PBB)) | |||||||||
| 1128 | continue; | |||||||||
| 1129 | ||||||||||
| 1130 | MachineBasicBlock *TBB = nullptr, *FBB = nullptr; | |||||||||
| 1131 | SmallVector<MachineOperand, 4> Cond; | |||||||||
| 1132 | if (!TII->analyzeBranch(*PBB, TBB, FBB, Cond, true)) { | |||||||||
| 1133 | // Failing case: IBB is the target of a cbr, and we cannot reverse the | |||||||||
| 1134 | // branch. | |||||||||
| 1135 | SmallVector<MachineOperand, 4> NewCond(Cond); | |||||||||
| 1136 | if (!Cond.empty() && TBB == IBB) { | |||||||||
| 1137 | if (TII->reverseBranchCondition(NewCond)) | |||||||||
| 1138 | continue; | |||||||||
| 1139 | // This is the QBB case described above | |||||||||
| 1140 | if (!FBB) { | |||||||||
| 1141 | auto Next = ++PBB->getIterator(); | |||||||||
| 1142 | if (Next != MF.end()) | |||||||||
| 1143 | FBB = &*Next; | |||||||||
| 1144 | } | |||||||||
| 1145 | } | |||||||||
| 1146 | ||||||||||
| 1147 | // Failing case: the only way IBB can be reached from PBB is via | |||||||||
| 1148 | // exception handling. Happens for landing pads. Would be nice to have | |||||||||
| 1149 | // a bit in the edge so we didn't have to do all this. | |||||||||
| 1150 | if (IBB->isEHPad()) { | |||||||||
| 1151 | MachineFunction::iterator IP = ++PBB->getIterator(); | |||||||||
| 1152 | MachineBasicBlock *PredNextBB = nullptr; | |||||||||
| 1153 | if (IP != MF.end()) | |||||||||
| 1154 | PredNextBB = &*IP; | |||||||||
| 1155 | if (!TBB) { | |||||||||
| 1156 | if (IBB != PredNextBB) // fallthrough | |||||||||
| 1157 | continue; | |||||||||
| 1158 | } else if (FBB) { | |||||||||
| 1159 | if (TBB != IBB && FBB != IBB) // cbr then ubr | |||||||||
| 1160 | continue; | |||||||||
| 1161 | } else if (Cond.empty()) { | |||||||||
| 1162 | if (TBB != IBB) // ubr | |||||||||
| 1163 | continue; | |||||||||
| 1164 | } else { | |||||||||
| 1165 | if (TBB != IBB && IBB != PredNextBB) // cbr | |||||||||
| 1166 | continue; | |||||||||
| 1167 | } | |||||||||
| 1168 | } | |||||||||
| 1169 | ||||||||||
| 1170 | // Remove the unconditional branch at the end, if any. | |||||||||
| 1171 | if (TBB && (Cond.empty() || FBB)) { | |||||||||
| 1172 | DebugLoc dl = PBB->findBranchDebugLoc(); | |||||||||
| 1173 | TII->removeBranch(*PBB); | |||||||||
| 1174 | if (!Cond.empty()) | |||||||||
| 1175 | // reinsert conditional branch only, for now | |||||||||
| 1176 | TII->insertBranch(*PBB, (TBB == IBB) ? FBB : TBB, nullptr, | |||||||||
| 1177 | NewCond, dl); | |||||||||
| 1178 | } | |||||||||
| 1179 | ||||||||||
| 1180 | MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(*PBB), PBB)); | |||||||||
| 1181 | } | |||||||||
| 1182 | } | |||||||||
| 1183 | ||||||||||
| 1184 | // If this is a large problem, avoid visiting the same basic blocks multiple | |||||||||
| 1185 | // times. | |||||||||
| 1186 | if (MergePotentials.size() == TailMergeThreshold) | |||||||||
| 1187 | for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i) | |||||||||
| 1188 | TriedMerging.insert(MergePotentials[i].getBlock()); | |||||||||
| 1189 | ||||||||||
| 1190 | if (MergePotentials.size() >= 2) | |||||||||
| 1191 | MadeChange |= TryTailMergeBlocks(IBB, PredBB, MinCommonTailLength); | |||||||||
| 1192 | ||||||||||
| 1193 | // Reinsert an unconditional branch if needed. The 1 below can occur as a | |||||||||
| 1194 | // result of removing blocks in TryTailMergeBlocks. | |||||||||
| 1195 | PredBB = &*std::prev(I); // this may have been changed in TryTailMergeBlocks | |||||||||
| 1196 | if (MergePotentials.size() == 1 && | |||||||||
| 1197 | MergePotentials.begin()->getBlock() != PredBB) | |||||||||
| 1198 | FixTail(MergePotentials.begin()->getBlock(), IBB, TII); | |||||||||
| 1199 | } | |||||||||
| 1200 | ||||||||||
| 1201 | return MadeChange; | |||||||||
| 1202 | } | |||||||||
| 1203 | ||||||||||
| 1204 | void BranchFolder::setCommonTailEdgeWeights(MachineBasicBlock &TailMBB) { | |||||||||
| 1205 | SmallVector<BlockFrequency, 2> EdgeFreqLs(TailMBB.succ_size()); | |||||||||
| 1206 | BlockFrequency AccumulatedMBBFreq; | |||||||||
| 1207 | ||||||||||
| 1208 | // Aggregate edge frequency of successor edge j: | |||||||||
| 1209 | // edgeFreq(j) = sum (freq(bb) * edgeProb(bb, j)), | |||||||||
| 1210 | // where bb is a basic block that is in SameTails. | |||||||||
| 1211 | for (const auto &Src : SameTails) { | |||||||||
| 1212 | const MachineBasicBlock *SrcMBB = Src.getBlock(); | |||||||||
| 1213 | BlockFrequency BlockFreq = MBBFreqInfo.getBlockFreq(SrcMBB); | |||||||||
| 1214 | AccumulatedMBBFreq += BlockFreq; | |||||||||
| 1215 | ||||||||||
| 1216 | // It is not necessary to recompute edge weights if TailBB has less than two | |||||||||
| 1217 | // successors. | |||||||||
| 1218 | if (TailMBB.succ_size() <= 1) | |||||||||
| 1219 | continue; | |||||||||
| 1220 | ||||||||||
| 1221 | auto EdgeFreq = EdgeFreqLs.begin(); | |||||||||
| 1222 | ||||||||||
| 1223 | for (auto SuccI = TailMBB.succ_begin(), SuccE = TailMBB.succ_end(); | |||||||||
| 1224 | SuccI != SuccE; ++SuccI, ++EdgeFreq) | |||||||||
| 1225 | *EdgeFreq += BlockFreq * MBPI.getEdgeProbability(SrcMBB, *SuccI); | |||||||||
| 1226 | } | |||||||||
| 1227 | ||||||||||
| 1228 | MBBFreqInfo.setBlockFreq(&TailMBB, AccumulatedMBBFreq); | |||||||||
| 1229 | ||||||||||
| 1230 | if (TailMBB.succ_size() <= 1) | |||||||||
| 1231 | return; | |||||||||
| 1232 | ||||||||||
| 1233 | auto SumEdgeFreq = | |||||||||
| 1234 | std::accumulate(EdgeFreqLs.begin(), EdgeFreqLs.end(), BlockFrequency(0)) | |||||||||
| 1235 | .getFrequency(); | |||||||||
| 1236 | auto EdgeFreq = EdgeFreqLs.begin(); | |||||||||
| 1237 | ||||||||||
| 1238 | if (SumEdgeFreq > 0) { | |||||||||
| 1239 | for (auto SuccI = TailMBB.succ_begin(), SuccE = TailMBB.succ_end(); | |||||||||
| 1240 | SuccI != SuccE; ++SuccI, ++EdgeFreq) { | |||||||||
| 1241 | auto Prob = BranchProbability::getBranchProbability( | |||||||||
| 1242 | EdgeFreq->getFrequency(), SumEdgeFreq); | |||||||||
| 1243 | TailMBB.setSuccProbability(SuccI, Prob); | |||||||||
| 1244 | } | |||||||||
| 1245 | } | |||||||||
| 1246 | } | |||||||||
| 1247 | ||||||||||
| 1248 | //===----------------------------------------------------------------------===// | |||||||||
| 1249 | // Branch Optimization | |||||||||
| 1250 | //===----------------------------------------------------------------------===// | |||||||||
| 1251 | ||||||||||
| 1252 | bool BranchFolder::OptimizeBranches(MachineFunction &MF) { | |||||||||
| 1253 | bool MadeChange = false; | |||||||||
| 1254 | ||||||||||
| 1255 | // Make sure blocks are numbered in order | |||||||||
| 1256 | MF.RenumberBlocks(); | |||||||||
| 1257 | // Renumbering blocks alters funclet membership, recalculate it. | |||||||||
| 1258 | FuncletMembership = getFuncletMembership(MF); | |||||||||
| 1259 | ||||||||||
| 1260 | for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end(); | |||||||||
| 1261 | I != E; ) { | |||||||||
| 1262 | MachineBasicBlock *MBB = &*I++; | |||||||||
| 1263 | MadeChange |= OptimizeBlock(MBB); | |||||||||
| 1264 | ||||||||||
| 1265 | // If it is dead, remove it. | |||||||||
| 1266 | if (MBB->pred_empty()) { | |||||||||
| 1267 | RemoveDeadBlock(MBB); | |||||||||
| 1268 | MadeChange = true; | |||||||||
| 1269 | ++NumDeadBlocks; | |||||||||
| 1270 | } | |||||||||
| 1271 | } | |||||||||
| 1272 | ||||||||||
| 1273 | return MadeChange; | |||||||||
| 1274 | } | |||||||||
| 1275 | ||||||||||
| 1276 | // Blocks should be considered empty if they contain only debug info; | |||||||||
| 1277 | // else the debug info would affect codegen. | |||||||||
| 1278 | static bool IsEmptyBlock(MachineBasicBlock *MBB) { | |||||||||
| 1279 | return MBB->getFirstNonDebugInstr() == MBB->end(); | |||||||||
| 1280 | } | |||||||||
| 1281 | ||||||||||
| 1282 | // Blocks with only debug info and branches should be considered the same | |||||||||
| 1283 | // as blocks with only branches. | |||||||||
| 1284 | static bool IsBranchOnlyBlock(MachineBasicBlock *MBB) { | |||||||||
| 1285 | MachineBasicBlock::iterator I = MBB->getFirstNonDebugInstr(); | |||||||||
| 1286 | assert(I != MBB->end() && "empty block!")(static_cast <bool> (I != MBB->end() && "empty block!" ) ? void (0) : __assert_fail ("I != MBB->end() && \"empty block!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 1286, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 1287 | return I->isBranch(); | |||||||||
| 1288 | } | |||||||||
| 1289 | ||||||||||
| 1290 | /// IsBetterFallthrough - Return true if it would be clearly better to | |||||||||
| 1291 | /// fall-through to MBB1 than to fall through into MBB2. This has to return | |||||||||
| 1292 | /// a strict ordering, returning true for both (MBB1,MBB2) and (MBB2,MBB1) will | |||||||||
| 1293 | /// result in infinite loops. | |||||||||
| 1294 | static bool IsBetterFallthrough(MachineBasicBlock *MBB1, | |||||||||
| 1295 | MachineBasicBlock *MBB2) { | |||||||||
| 1296 | // Right now, we use a simple heuristic. If MBB2 ends with a call, and | |||||||||
| 1297 | // MBB1 doesn't, we prefer to fall through into MBB1. This allows us to | |||||||||
| 1298 | // optimize branches that branch to either a return block or an assert block | |||||||||
| 1299 | // into a fallthrough to the return. | |||||||||
| 1300 | MachineBasicBlock::iterator MBB1I = MBB1->getLastNonDebugInstr(); | |||||||||
| 1301 | MachineBasicBlock::iterator MBB2I = MBB2->getLastNonDebugInstr(); | |||||||||
| 1302 | if (MBB1I == MBB1->end() || MBB2I == MBB2->end()) | |||||||||
| 1303 | return false; | |||||||||
| 1304 | ||||||||||
| 1305 | // If there is a clear successor ordering we make sure that one block | |||||||||
| 1306 | // will fall through to the next | |||||||||
| 1307 | if (MBB1->isSuccessor(MBB2)) return true; | |||||||||
| 1308 | if (MBB2->isSuccessor(MBB1)) return false; | |||||||||
| 1309 | ||||||||||
| 1310 | return MBB2I->isCall() && !MBB1I->isCall(); | |||||||||
| 1311 | } | |||||||||
| 1312 | ||||||||||
| 1313 | /// getBranchDebugLoc - Find and return, if any, the DebugLoc of the branch | |||||||||
| 1314 | /// instructions on the block. | |||||||||
| 1315 | static DebugLoc getBranchDebugLoc(MachineBasicBlock &MBB) { | |||||||||
| 1316 | MachineBasicBlock::iterator I = MBB.getLastNonDebugInstr(); | |||||||||
| 1317 | if (I != MBB.end() && I->isBranch()) | |||||||||
| 1318 | return I->getDebugLoc(); | |||||||||
| 1319 | return DebugLoc(); | |||||||||
| 1320 | } | |||||||||
| 1321 | ||||||||||
| 1322 | bool BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) { | |||||||||
| 1323 | bool MadeChange = false; | |||||||||
| 1324 | MachineFunction &MF = *MBB->getParent(); | |||||||||
| 1325 | ReoptimizeBlock: | |||||||||
| 1326 | ||||||||||
| 1327 | MachineFunction::iterator FallThrough = MBB->getIterator(); | |||||||||
| 1328 | ++FallThrough; | |||||||||
| 1329 | ||||||||||
| 1330 | // Make sure MBB and FallThrough belong to the same funclet. | |||||||||
| 1331 | bool SameFunclet = true; | |||||||||
| 1332 | if (!FuncletMembership.empty() && FallThrough != MF.end()) { | |||||||||
| ||||||||||
| 1333 | auto MBBFunclet = FuncletMembership.find(MBB); | |||||||||
| 1334 | assert(MBBFunclet != FuncletMembership.end())(static_cast <bool> (MBBFunclet != FuncletMembership.end ()) ? void (0) : __assert_fail ("MBBFunclet != FuncletMembership.end()" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 1334, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 1335 | auto FallThroughFunclet = FuncletMembership.find(&*FallThrough); | |||||||||
| 1336 | assert(FallThroughFunclet != FuncletMembership.end())(static_cast <bool> (FallThroughFunclet != FuncletMembership .end()) ? void (0) : __assert_fail ("FallThroughFunclet != FuncletMembership.end()" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 1336, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 1337 | SameFunclet = MBBFunclet->second == FallThroughFunclet->second; | |||||||||
| 1338 | } | |||||||||
| 1339 | ||||||||||
| 1340 | // If this block is empty, make everyone use its fall-through, not the block | |||||||||
| 1341 | // explicitly. Landing pads should not do this since the landing-pad table | |||||||||
| 1342 | // points to this block. Blocks with their addresses taken shouldn't be | |||||||||
| 1343 | // optimized away. | |||||||||
| 1344 | if (IsEmptyBlock(MBB) && !MBB->isEHPad() && !MBB->hasAddressTaken() && | |||||||||
| 1345 | SameFunclet) { | |||||||||
| 1346 | // Dead block? Leave for cleanup later. | |||||||||
| 1347 | if (MBB->pred_empty()) return MadeChange; | |||||||||
| 1348 | ||||||||||
| 1349 | if (FallThrough == MF.end()) { | |||||||||
| 1350 | // TODO: Simplify preds to not branch here if possible! | |||||||||
| 1351 | } else if (FallThrough->isEHPad()) { | |||||||||
| 1352 | // Don't rewrite to a landing pad fallthough. That could lead to the case | |||||||||
| 1353 | // where a BB jumps to more than one landing pad. | |||||||||
| 1354 | // TODO: Is it ever worth rewriting predecessors which don't already | |||||||||
| 1355 | // jump to a landing pad, and so can safely jump to the fallthrough? | |||||||||
| 1356 | } else if (MBB->isSuccessor(&*FallThrough)) { | |||||||||
| 1357 | // Rewrite all predecessors of the old block to go to the fallthrough | |||||||||
| 1358 | // instead. | |||||||||
| 1359 | while (!MBB->pred_empty()) { | |||||||||
| 1360 | MachineBasicBlock *Pred = *(MBB->pred_end()-1); | |||||||||
| 1361 | Pred->ReplaceUsesOfBlockWith(MBB, &*FallThrough); | |||||||||
| 1362 | } | |||||||||
| 1363 | // If MBB was the target of a jump table, update jump tables to go to the | |||||||||
| 1364 | // fallthrough instead. | |||||||||
| 1365 | if (MachineJumpTableInfo *MJTI = MF.getJumpTableInfo()) | |||||||||
| 1366 | MJTI->ReplaceMBBInJumpTables(MBB, &*FallThrough); | |||||||||
| 1367 | MadeChange = true; | |||||||||
| 1368 | } | |||||||||
| 1369 | return MadeChange; | |||||||||
| 1370 | } | |||||||||
| 1371 | ||||||||||
| 1372 | // Check to see if we can simplify the terminator of the block before this | |||||||||
| 1373 | // one. | |||||||||
| 1374 | MachineBasicBlock &PrevBB = *std::prev(MachineFunction::iterator(MBB)); | |||||||||
| 1375 | ||||||||||
| 1376 | MachineBasicBlock *PriorTBB = nullptr, *PriorFBB = nullptr; | |||||||||
| 1377 | SmallVector<MachineOperand, 4> PriorCond; | |||||||||
| 1378 | bool PriorUnAnalyzable = | |||||||||
| 1379 | TII->analyzeBranch(PrevBB, PriorTBB, PriorFBB, PriorCond, true); | |||||||||
| 1380 | if (!PriorUnAnalyzable) { | |||||||||
| 1381 | // If the CFG for the prior block has extra edges, remove them. | |||||||||
| 1382 | MadeChange |= PrevBB.CorrectExtraCFGEdges(PriorTBB, PriorFBB, | |||||||||
| 1383 | !PriorCond.empty()); | |||||||||
| 1384 | ||||||||||
| 1385 | // If the previous branch is conditional and both conditions go to the same | |||||||||
| 1386 | // destination, remove the branch, replacing it with an unconditional one or | |||||||||
| 1387 | // a fall-through. | |||||||||
| 1388 | if (PriorTBB && PriorTBB == PriorFBB) { | |||||||||
| 1389 | DebugLoc dl = getBranchDebugLoc(PrevBB); | |||||||||
| 1390 | TII->removeBranch(PrevBB); | |||||||||
| 1391 | PriorCond.clear(); | |||||||||
| 1392 | if (PriorTBB != MBB) | |||||||||
| 1393 | TII->insertBranch(PrevBB, PriorTBB, nullptr, PriorCond, dl); | |||||||||
| 1394 | MadeChange = true; | |||||||||
| 1395 | ++NumBranchOpts; | |||||||||
| 1396 | goto ReoptimizeBlock; | |||||||||
| 1397 | } | |||||||||
| 1398 | ||||||||||
| 1399 | // If the previous block unconditionally falls through to this block and | |||||||||
| 1400 | // this block has no other predecessors, move the contents of this block | |||||||||
| 1401 | // into the prior block. This doesn't usually happen when SimplifyCFG | |||||||||
| 1402 | // has been used, but it can happen if tail merging splits a fall-through | |||||||||
| 1403 | // predecessor of a block. | |||||||||
| 1404 | // This has to check PrevBB->succ_size() because EH edges are ignored by | |||||||||
| 1405 | // AnalyzeBranch. | |||||||||
| 1406 | if (PriorCond.empty() && !PriorTBB && MBB->pred_size() == 1 && | |||||||||
| 1407 | PrevBB.succ_size() == 1 && | |||||||||
| 1408 | !MBB->hasAddressTaken() && !MBB->isEHPad()) { | |||||||||
| 1409 | DEBUG(dbgs() << "\nMerging into block: " << PrevBBdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nMerging into block: " << PrevBB << "From MBB: " << *MBB; } } while (false) | |||||||||
| 1410 | << "From MBB: " << *MBB)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nMerging into block: " << PrevBB << "From MBB: " << *MBB; } } while (false); | |||||||||
| 1411 | // Remove redundant DBG_VALUEs first. | |||||||||
| 1412 | if (PrevBB.begin() != PrevBB.end()) { | |||||||||
| 1413 | MachineBasicBlock::iterator PrevBBIter = PrevBB.end(); | |||||||||
| 1414 | --PrevBBIter; | |||||||||
| 1415 | MachineBasicBlock::iterator MBBIter = MBB->begin(); | |||||||||
| 1416 | // Check if DBG_VALUE at the end of PrevBB is identical to the | |||||||||
| 1417 | // DBG_VALUE at the beginning of MBB. | |||||||||
| 1418 | while (PrevBBIter != PrevBB.begin() && MBBIter != MBB->end() | |||||||||
| 1419 | && PrevBBIter->isDebugValue() && MBBIter->isDebugValue()) { | |||||||||
| 1420 | if (!MBBIter->isIdenticalTo(*PrevBBIter)) | |||||||||
| 1421 | break; | |||||||||
| 1422 | MachineInstr &DuplicateDbg = *MBBIter; | |||||||||
| 1423 | ++MBBIter; -- PrevBBIter; | |||||||||
| 1424 | DuplicateDbg.eraseFromParent(); | |||||||||
| 1425 | } | |||||||||
| 1426 | } | |||||||||
| 1427 | PrevBB.splice(PrevBB.end(), MBB, MBB->begin(), MBB->end()); | |||||||||
| 1428 | PrevBB.removeSuccessor(PrevBB.succ_begin()); | |||||||||
| 1429 | assert(PrevBB.succ_empty())(static_cast <bool> (PrevBB.succ_empty()) ? void (0) : __assert_fail ("PrevBB.succ_empty()", "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 1429, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 1430 | PrevBB.transferSuccessors(MBB); | |||||||||
| 1431 | MadeChange = true; | |||||||||
| 1432 | return MadeChange; | |||||||||
| 1433 | } | |||||||||
| 1434 | ||||||||||
| 1435 | // If the previous branch *only* branches to *this* block (conditional or | |||||||||
| 1436 | // not) remove the branch. | |||||||||
| 1437 | if (PriorTBB == MBB && !PriorFBB) { | |||||||||
| 1438 | TII->removeBranch(PrevBB); | |||||||||
| 1439 | MadeChange = true; | |||||||||
| 1440 | ++NumBranchOpts; | |||||||||
| 1441 | goto ReoptimizeBlock; | |||||||||
| 1442 | } | |||||||||
| 1443 | ||||||||||
| 1444 | // If the prior block branches somewhere else on the condition and here if | |||||||||
| 1445 | // the condition is false, remove the uncond second branch. | |||||||||
| 1446 | if (PriorFBB == MBB) { | |||||||||
| 1447 | DebugLoc dl = getBranchDebugLoc(PrevBB); | |||||||||
| 1448 | TII->removeBranch(PrevBB); | |||||||||
| 1449 | TII->insertBranch(PrevBB, PriorTBB, nullptr, PriorCond, dl); | |||||||||
| 1450 | MadeChange = true; | |||||||||
| 1451 | ++NumBranchOpts; | |||||||||
| 1452 | goto ReoptimizeBlock; | |||||||||
| 1453 | } | |||||||||
| 1454 | ||||||||||
| 1455 | // If the prior block branches here on true and somewhere else on false, and | |||||||||
| 1456 | // if the branch condition is reversible, reverse the branch to create a | |||||||||
| 1457 | // fall-through. | |||||||||
| 1458 | if (PriorTBB == MBB) { | |||||||||
| 1459 | SmallVector<MachineOperand, 4> NewPriorCond(PriorCond); | |||||||||
| 1460 | if (!TII->reverseBranchCondition(NewPriorCond)) { | |||||||||
| 1461 | DebugLoc dl = getBranchDebugLoc(PrevBB); | |||||||||
| 1462 | TII->removeBranch(PrevBB); | |||||||||
| 1463 | TII->insertBranch(PrevBB, PriorFBB, nullptr, NewPriorCond, dl); | |||||||||
| 1464 | MadeChange = true; | |||||||||
| 1465 | ++NumBranchOpts; | |||||||||
| 1466 | goto ReoptimizeBlock; | |||||||||
| 1467 | } | |||||||||
| 1468 | } | |||||||||
| 1469 | ||||||||||
| 1470 | // If this block has no successors (e.g. it is a return block or ends with | |||||||||
| 1471 | // a call to a no-return function like abort or __cxa_throw) and if the pred | |||||||||
| 1472 | // falls through into this block, and if it would otherwise fall through | |||||||||
| 1473 | // into the block after this, move this block to the end of the function. | |||||||||
| 1474 | // | |||||||||
| 1475 | // We consider it more likely that execution will stay in the function (e.g. | |||||||||
| 1476 | // due to loops) than it is to exit it. This asserts in loops etc, moving | |||||||||
| 1477 | // the assert condition out of the loop body. | |||||||||
| 1478 | if (MBB->succ_empty() && !PriorCond.empty() && !PriorFBB && | |||||||||
| 1479 | MachineFunction::iterator(PriorTBB) == FallThrough && | |||||||||
| 1480 | !MBB->canFallThrough()) { | |||||||||
| 1481 | bool DoTransform = true; | |||||||||
| 1482 | ||||||||||
| 1483 | // We have to be careful that the succs of PredBB aren't both no-successor | |||||||||
| 1484 | // blocks. If neither have successors and if PredBB is the second from | |||||||||
| 1485 | // last block in the function, we'd just keep swapping the two blocks for | |||||||||
| 1486 | // last. Only do the swap if one is clearly better to fall through than | |||||||||
| 1487 | // the other. | |||||||||
| 1488 | if (FallThrough == --MF.end() && | |||||||||
| 1489 | !IsBetterFallthrough(PriorTBB, MBB)) | |||||||||
| 1490 | DoTransform = false; | |||||||||
| 1491 | ||||||||||
| 1492 | if (DoTransform) { | |||||||||
| 1493 | // Reverse the branch so we will fall through on the previous true cond. | |||||||||
| 1494 | SmallVector<MachineOperand, 4> NewPriorCond(PriorCond); | |||||||||
| 1495 | if (!TII->reverseBranchCondition(NewPriorCond)) { | |||||||||
| 1496 | DEBUG(dbgs() << "\nMoving MBB: " << *MBBdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nMoving MBB: " << *MBB << "To make fallthrough to: " << *PriorTBB << "\n"; } } while (false) | |||||||||
| ||||||||||
| 1497 | << "To make fallthrough to: " << *PriorTBB << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("branch-folder")) { dbgs() << "\nMoving MBB: " << *MBB << "To make fallthrough to: " << *PriorTBB << "\n"; } } while (false); | |||||||||
| 1498 | ||||||||||
| 1499 | DebugLoc dl = getBranchDebugLoc(PrevBB); | |||||||||
| 1500 | TII->removeBranch(PrevBB); | |||||||||
| 1501 | TII->insertBranch(PrevBB, MBB, nullptr, NewPriorCond, dl); | |||||||||
| 1502 | ||||||||||
| 1503 | // Move this block to the end of the function. | |||||||||
| 1504 | MBB->moveAfter(&MF.back()); | |||||||||
| 1505 | MadeChange = true; | |||||||||
| 1506 | ++NumBranchOpts; | |||||||||
| 1507 | return MadeChange; | |||||||||
| 1508 | } | |||||||||
| 1509 | } | |||||||||
| 1510 | } | |||||||||
| 1511 | } | |||||||||
| 1512 | ||||||||||
| 1513 | if (!IsEmptyBlock(MBB) && MBB->pred_size() == 1 && | |||||||||
| 1514 | MF.getFunction().optForSize()) { | |||||||||
| 1515 | // Changing "Jcc foo; foo: jmp bar;" into "Jcc bar;" might change the branch | |||||||||
| 1516 | // direction, thereby defeating careful block placement and regressing | |||||||||
| 1517 | // performance. Therefore, only consider this for optsize functions. | |||||||||
| 1518 | MachineInstr &TailCall = *MBB->getFirstNonDebugInstr(); | |||||||||
| 1519 | if (TII->isUnconditionalTailCall(TailCall)) { | |||||||||
| 1520 | MachineBasicBlock *Pred = *MBB->pred_begin(); | |||||||||
| 1521 | MachineBasicBlock *PredTBB = nullptr, *PredFBB = nullptr; | |||||||||
| 1522 | SmallVector<MachineOperand, 4> PredCond; | |||||||||
| 1523 | bool PredAnalyzable = | |||||||||
| 1524 | !TII->analyzeBranch(*Pred, PredTBB, PredFBB, PredCond, true); | |||||||||
| 1525 | ||||||||||
| 1526 | if (PredAnalyzable && !PredCond.empty() && PredTBB == MBB && | |||||||||
| 1527 | PredTBB != PredFBB) { | |||||||||
| 1528 | // The predecessor has a conditional branch to this block which consists | |||||||||
| 1529 | // of only a tail call. Try to fold the tail call into the conditional | |||||||||
| 1530 | // branch. | |||||||||
| 1531 | if (TII->canMakeTailCallConditional(PredCond, TailCall)) { | |||||||||
| 1532 | // TODO: It would be nice if analyzeBranch() could provide a pointer | |||||||||
| 1533 | // to the branch instruction so replaceBranchWithTailCall() doesn't | |||||||||
| 1534 | // have to search for it. | |||||||||
| 1535 | TII->replaceBranchWithTailCall(*Pred, PredCond, TailCall); | |||||||||
| 1536 | ++NumTailCalls; | |||||||||
| 1537 | Pred->removeSuccessor(MBB); | |||||||||
| 1538 | MadeChange = true; | |||||||||
| 1539 | return MadeChange; | |||||||||
| 1540 | } | |||||||||
| 1541 | } | |||||||||
| 1542 | // If the predecessor is falling through to this block, we could reverse | |||||||||
| 1543 | // the branch condition and fold the tail call into that. However, after | |||||||||
| 1544 | // that we might have to re-arrange the CFG to fall through to the other | |||||||||
| 1545 | // block and there is a high risk of regressing code size rather than | |||||||||
| 1546 | // improving it. | |||||||||
| 1547 | } | |||||||||
| 1548 | } | |||||||||
| 1549 | ||||||||||
| 1550 | // Analyze the branch in the current block. | |||||||||
| 1551 | MachineBasicBlock *CurTBB = nullptr, *CurFBB = nullptr; | |||||||||
| 1552 | SmallVector<MachineOperand, 4> CurCond; | |||||||||
| 1553 | bool CurUnAnalyzable = | |||||||||
| 1554 | TII->analyzeBranch(*MBB, CurTBB, CurFBB, CurCond, true); | |||||||||
| 1555 | if (!CurUnAnalyzable) { | |||||||||
| 1556 | // If the CFG for the prior block has extra edges, remove them. | |||||||||
| 1557 | MadeChange |= MBB->CorrectExtraCFGEdges(CurTBB, CurFBB, !CurCond.empty()); | |||||||||
| 1558 | ||||||||||
| 1559 | // If this is a two-way branch, and the FBB branches to this block, reverse | |||||||||
| 1560 | // the condition so the single-basic-block loop is faster. Instead of: | |||||||||
| 1561 | // Loop: xxx; jcc Out; jmp Loop | |||||||||
| 1562 | // we want: | |||||||||
| 1563 | // Loop: xxx; jncc Loop; jmp Out | |||||||||
| 1564 | if (CurTBB && CurFBB && CurFBB == MBB && CurTBB != MBB) { | |||||||||
| 1565 | SmallVector<MachineOperand, 4> NewCond(CurCond); | |||||||||
| 1566 | if (!TII->reverseBranchCondition(NewCond)) { | |||||||||
| 1567 | DebugLoc dl = getBranchDebugLoc(*MBB); | |||||||||
| 1568 | TII->removeBranch(*MBB); | |||||||||
| 1569 | TII->insertBranch(*MBB, CurFBB, CurTBB, NewCond, dl); | |||||||||
| 1570 | MadeChange = true; | |||||||||
| 1571 | ++NumBranchOpts; | |||||||||
| 1572 | goto ReoptimizeBlock; | |||||||||
| 1573 | } | |||||||||
| 1574 | } | |||||||||
| 1575 | ||||||||||
| 1576 | // If this branch is the only thing in its block, see if we can forward | |||||||||
| 1577 | // other blocks across it. | |||||||||
| 1578 | if (CurTBB && CurCond.empty() && !CurFBB && | |||||||||
| 1579 | IsBranchOnlyBlock(MBB) && CurTBB != MBB && | |||||||||
| 1580 | !MBB->hasAddressTaken() && !MBB->isEHPad()) { | |||||||||
| 1581 | DebugLoc dl = getBranchDebugLoc(*MBB); | |||||||||
| 1582 | // This block may contain just an unconditional branch. Because there can | |||||||||
| 1583 | // be 'non-branch terminators' in the block, try removing the branch and | |||||||||
| 1584 | // then seeing if the block is empty. | |||||||||
| 1585 | TII->removeBranch(*MBB); | |||||||||
| 1586 | // If the only things remaining in the block are debug info, remove these | |||||||||
| 1587 | // as well, so this will behave the same as an empty block in non-debug | |||||||||
| 1588 | // mode. | |||||||||
| 1589 | if (IsEmptyBlock(MBB)) { | |||||||||
| 1590 | // Make the block empty, losing the debug info (we could probably | |||||||||
| 1591 | // improve this in some cases.) | |||||||||
| 1592 | MBB->erase(MBB->begin(), MBB->end()); | |||||||||
| 1593 | } | |||||||||
| 1594 | // If this block is just an unconditional branch to CurTBB, we can | |||||||||
| 1595 | // usually completely eliminate the block. The only case we cannot | |||||||||
| 1596 | // completely eliminate the block is when the block before this one | |||||||||
| 1597 | // falls through into MBB and we can't understand the prior block's branch | |||||||||
| 1598 | // condition. | |||||||||
| 1599 | if (MBB->empty()) { | |||||||||
| 1600 | bool PredHasNoFallThrough = !PrevBB.canFallThrough(); | |||||||||
| 1601 | if (PredHasNoFallThrough || !PriorUnAnalyzable || | |||||||||
| 1602 | !PrevBB.isSuccessor(MBB)) { | |||||||||
| 1603 | // If the prior block falls through into us, turn it into an | |||||||||
| 1604 | // explicit branch to us to make updates simpler. | |||||||||
| 1605 | if (!PredHasNoFallThrough && PrevBB.isSuccessor(MBB) && | |||||||||
| 1606 | PriorTBB != MBB && PriorFBB != MBB) { | |||||||||
| 1607 | if (!PriorTBB) { | |||||||||
| 1608 | assert(PriorCond.empty() && !PriorFBB &&(static_cast <bool> (PriorCond.empty() && !PriorFBB && "Bad branch analysis") ? void (0) : __assert_fail ("PriorCond.empty() && !PriorFBB && \"Bad branch analysis\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 1609, __extension__ __PRETTY_FUNCTION__)) | |||||||||
| 1609 | "Bad branch analysis")(static_cast <bool> (PriorCond.empty() && !PriorFBB && "Bad branch analysis") ? void (0) : __assert_fail ("PriorCond.empty() && !PriorFBB && \"Bad branch analysis\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 1609, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 1610 | PriorTBB = MBB; | |||||||||
| 1611 | } else { | |||||||||
| 1612 | assert(!PriorFBB && "Machine CFG out of date!")(static_cast <bool> (!PriorFBB && "Machine CFG out of date!" ) ? void (0) : __assert_fail ("!PriorFBB && \"Machine CFG out of date!\"" , "/build/llvm-toolchain-snapshot-7~svn329677/lib/CodeGen/BranchFolding.cpp" , 1612, __extension__ __PRETTY_FUNCTION__)); | |||||||||
| 1613 | PriorFBB = MBB; | |||||||||
| 1614 | } | |||||||||
| 1615 | DebugLoc pdl = getBranchDebugLoc(PrevBB); | |||||||||
| 1616 | TII->removeBranch(PrevBB); | |||||||||
| 1617 | TII->insertBranch(PrevBB, PriorTBB, PriorFBB, PriorCond, pdl); | |||||||||
| 1618 | } | |||||||||
| 1619 | ||||||||||
| 1620 | // Iterate through all the predecessors, revectoring each in-turn. | |||||||||
| 1621 | size_t PI = 0; | |||||||||
| 1622 | bool DidChange = false; | |||||||||
| 1623 | bool HasBranchToSelf = false; | |||||||||
| 1624 | while(PI != MBB->pred_size()) { | |||||||||
| 1625 | MachineBasicBlock *PMBB = *(MBB->pred_begin() + PI); | |||||||||
| 1626 | if (PMBB == MBB) { | |||||||||
| 1627 | // If this block has an uncond branch to itself, leave it. | |||||||||
| 1628 | ++PI; | |||||||||
| 1629 | HasBranchToSelf = true; | |||||||||
| 1630 | } else { | |||||||||
| 1631 | DidChange = true; | |||||||||
| 1632 | PMBB->ReplaceUsesOfBlockWith(MBB, CurTBB); | |||||||||
| 1633 | // If this change resulted in PMBB ending in a conditional | |||||||||
| 1634 | // branch where both conditions go to the same destination, | |||||||||
| 1635 | // change this to an unconditional branch (and fix the CFG). | |||||||||
| 1636 | MachineBasicBlock *NewCurTBB = nullptr, *NewCurFBB = nullptr; | |||||||||
| 1637 | SmallVector<MachineOperand, 4> NewCurCond; | |||||||||
| 1638 | bool NewCurUnAnalyzable = TII->analyzeBranch( | |||||||||
| 1639 | *PMBB, NewCurTBB, NewCurFBB, NewCurCond, true); | |||||||||
| 1640 | if (!NewCurUnAnalyzable && NewCurTBB && NewCurTBB == NewCurFBB) { | |||||||||
| 1641 | DebugLoc pdl = getBranchDebugLoc(*PMBB); | |||||||||
| 1642 | TII->removeBranch(*PMBB); | |||||||||
| 1643 | NewCurCond.clear(); | |||||||||
| 1644 | TII->insertBranch(*PMBB, NewCurTBB, nullptr, NewCurCond, pdl); | |||||||||
| 1645 | MadeChange = true; | |||||||||
| 1646 | ++NumBranchOpts; | |||||||||
| 1647 | PMBB->CorrectExtraCFGEdges(NewCurTBB, nullptr, false); | |||||||||
| 1648 | } | |||||||||
| 1649 | } | |||||||||
| 1650 | } | |||||||||
| 1651 | ||||||||||
| 1652 | // Change any jumptables to go to the new MBB. | |||||||||
| 1653 | if (MachineJumpTableInfo *MJTI = MF.getJumpTableInfo()) | |||||||||
| 1654 | MJTI->ReplaceMBBInJumpTables(MBB, CurTBB); | |||||||||
| 1655 | if (DidChange) { | |||||||||
| 1656 | ++NumBranchOpts; | |||||||||
| 1657 | MadeChange = true; | |||||||||
| 1658 | if (!HasBranchToSelf) return MadeChange; | |||||||||
| 1659 | } | |||||||||
| 1660 | } | |||||||||
| 1661 | } | |||||||||
| 1662 | ||||||||||
| 1663 | // Add the branch back if the block is more than just an uncond branch. | |||||||||
| 1664 | TII->insertBranch(*MBB, CurTBB, nullptr, CurCond, dl); | |||||||||
| 1665 | } | |||||||||
| 1666 | } | |||||||||
| 1667 | ||||||||||
| 1668 | // If the prior block doesn't fall through into this block, and if this | |||||||||
| 1669 | // block doesn't fall through into some other block, see if we can find a | |||||||||
| 1670 | // place to move this block where a fall-through will happen. | |||||||||
| 1671 | if (!PrevBB.canFallThrough()) { | |||||||||
| 1672 | // Now we know that there was no fall-through into this block, check to | |||||||||
| 1673 | // see if it has a fall-through into its successor. | |||||||||
| 1674 | bool CurFallsThru = MBB->canFallThrough(); | |||||||||
| 1675 | ||||||||||
| 1676 | if (!MBB->isEHPad()) { | |||||||||
| 1677 | // Check all the predecessors of this block. If one of them has no fall | |||||||||
| 1678 | // throughs, move this block right after it. | |||||||||
| 1679 | for (MachineBasicBlock *PredBB : MBB->predecessors()) { | |||||||||
| 1680 | // Analyze the branch at the end of the pred. | |||||||||
| 1681 | MachineBasicBlock *PredTBB = nullptr, *PredFBB = nullptr; | |||||||||
| 1682 | SmallVector<MachineOperand, 4> PredCond; | |||||||||
| 1683 | if (PredBB != MBB && !PredBB->canFallThrough() && | |||||||||
| 1684 | !TII->analyzeBranch(*PredBB, PredTBB, PredFBB, PredCond, true) && | |||||||||
| 1685 | (!CurFallsThru || !CurTBB || !CurFBB) && | |||||||||
| 1686 | (!CurFallsThru || MBB->getNumber() >= PredBB->getNumber())) { | |||||||||
| 1687 | // If the current block doesn't fall through, just move it. | |||||||||
| 1688 | // If the current block can fall through and does not end with a | |||||||||
| 1689 | // conditional branch, we need to append an unconditional jump to | |||||||||
| 1690 | // the (current) next block. To avoid a possible compile-time | |||||||||
| 1691 | // infinite loop, move blocks only backward in this case. | |||||||||
| 1692 | // Also, if there are already 2 branches here, we cannot add a third; | |||||||||
| 1693 | // this means we have the case | |||||||||
| 1694 | // Bcc next | |||||||||
| 1695 | // B elsewhere | |||||||||
| 1696 | // next: | |||||||||
| 1697 | if (CurFallsThru) { | |||||||||
| 1698 | MachineBasicBlock *NextBB = &*std::next(MBB->getIterator()); | |||||||||
| 1699 | CurCond.clear(); | |||||||||
| 1700 | TII->insertBranch(*MBB, NextBB, nullptr, CurCond, DebugLoc()); | |||||||||
| 1701 | } | |||||||||
| 1702 | MBB->moveAfter(PredBB); | |||||||||
| 1703 | MadeChange = true; | |||||||||
| 1704 | goto ReoptimizeBlock; | |||||||||
| 1705 | } | |||||||||
| 1706 | } | |||||||||
| 1707 | } | |||||||||
| 1708 | ||||||||||
| 1709 | if (!CurFallsThru) { | |||||||||
| 1710 | // Check all successors to see if we can move this block before it. | |||||||||
| 1711 | for (MachineBasicBlock *SuccBB : MBB->successors()) { | |||||||||
| 1712 | // Analyze the branch at the end of the block before the succ. | |||||||||
| 1713 | MachineFunction::iterator SuccPrev = --SuccBB->getIterator(); | |||||||||
| 1714 | ||||||||||
| 1715 | // If this block doesn't already fall-through to that successor, and if | |||||||||
| 1716 | // the succ doesn't already have a block that can fall through into it, | |||||||||
| 1717 | // and if the successor isn't an EH destination, we can arrange for the | |||||||||
| 1718 | // fallthrough to happen. | |||||||||
| 1719 | if (SuccBB != MBB && &*SuccPrev != MBB && | |||||||||
| 1720 | !SuccPrev->canFallThrough() && !CurUnAnalyzable && | |||||||||
| 1721 | !SuccBB->isEHPad()) { | |||||||||
| 1722 | MBB->moveBefore(SuccBB); | |||||||||
| 1723 | MadeChange = true; | |||||||||
| 1724 | goto ReoptimizeBlock; | |||||||||
| 1725 | } | |||||||||
| 1726 | } | |||||||||
| 1727 | ||||||||||
| 1728 | // Okay, there is no really great place to put this block. If, however, | |||||||||
| 1729 | // the block before this one would be a fall-through if this block were | |||||||||
| 1730 | // removed, move this block to the end of the function. There is no real | |||||||||
| 1731 | // advantage in "falling through" to an EH block, so we don't want to | |||||||||
| 1732 | // perform this transformation for that case. | |||||||||
| 1733 | // | |||||||||
| 1734 | // Also, Windows EH introduced the possibility of an arbitrary number of | |||||||||
| 1735 | // successors to a given block. The analyzeBranch call does not consider | |||||||||
| 1736 | // exception handling and so we can get in a state where a block | |||||||||
| 1737 | // containing a call is followed by multiple EH blocks that would be | |||||||||
| 1738 | // rotated infinitely at the end of the function if the transformation | |||||||||
| 1739 | // below were performed for EH "FallThrough" blocks. Therefore, even if | |||||||||
| 1740 | // that appears not to be happening anymore, we should assume that it is | |||||||||
| 1741 | // possible and not remove the "!FallThrough()->isEHPad" condition below. | |||||||||
| 1742 | MachineBasicBlock *PrevTBB = nullptr, *PrevFBB = nullptr; | |||||||||
| 1743 | SmallVector<MachineOperand, 4> PrevCond; | |||||||||
| 1744 | if (FallThrough != MF.end() && | |||||||||
| 1745 | !FallThrough->isEHPad() && | |||||||||
| 1746 | !TII->analyzeBranch(PrevBB, PrevTBB, PrevFBB, PrevCond, true) && | |||||||||
| 1747 | PrevBB.isSuccessor(&*FallThrough)) { | |||||||||
| 1748 | MBB->moveAfter(&MF.back()); | |||||||||
| 1749 | MadeChange = true; | |||||||||
| 1750 | return MadeChange; | |||||||||
| 1751 | } | |||||||||
| 1752 | } | |||||||||
| 1753 | } | |||||||||
| 1754 | ||||||||||
| 1755 | return MadeChange; | |||||||||
| 1756 | } | |||||||||
| 1757 | ||||||||||
| 1758 | //===----------------------------------------------------------------------===// | |||||||||
| 1759 | // Hoist Common Code | |||||||||
| 1760 | //===----------------------------------------------------------------------===// | |||||||||
| 1761 | ||||||||||
| 1762 | bool BranchFolder::HoistCommonCode(MachineFunction &MF) { | |||||||||
| 1763 | bool MadeChange = false; | |||||||||
| 1764 | for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ) { | |||||||||
| 1765 | MachineBasicBlock *MBB = &*I++; | |||||||||
| 1766 | MadeChange |= HoistCommonCodeInSuccs(MBB); | |||||||||
| 1767 | } | |||||||||
| 1768 | ||||||||||
| 1769 | return MadeChange; | |||||||||
| 1770 | } | |||||||||
| 1771 | ||||||||||
| 1772 | /// findFalseBlock - BB has a fallthrough. Find its 'false' successor given | |||||||||
| 1773 | /// its 'true' successor. | |||||||||
| 1774 | static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB, | |||||||||
| 1775 | MachineBasicBlock *TrueBB) { | |||||||||
| 1776 | for (MachineBasicBlock *SuccBB : BB->successors()) | |||||||||
| 1777 | if (SuccBB != TrueBB) | |||||||||
| 1778 | return SuccBB; | |||||||||
| 1779 | return nullptr; | |||||||||
| 1780 | } | |||||||||
| 1781 | ||||||||||
| 1782 | template <class Container> | |||||||||
| 1783 | static void addRegAndItsAliases(unsigned Reg, const TargetRegisterInfo *TRI, | |||||||||
| 1784 | Container &Set) { | |||||||||
| 1785 | if (TargetRegisterInfo::isPhysicalRegister(Reg)) { | |||||||||
| 1786 | for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) | |||||||||
| 1787 | Set.insert(*AI); | |||||||||
| 1788 | } else { | |||||||||
| 1789 | Set.insert(Reg); | |||||||||
| 1790 | } | |||||||||
| 1791 | } | |||||||||
| 1792 | ||||||||||
| 1793 | /// findHoistingInsertPosAndDeps - Find the location to move common instructions | |||||||||
| 1794 | /// in successors to. The location is usually just before the terminator, | |||||||||
| 1795 | /// however if the terminator is a conditional branch and its previous | |||||||||
| 1796 | /// instruction is the flag setting instruction, the previous instruction is | |||||||||
| 1797 | /// the preferred location. This function also gathers uses and defs of the | |||||||||
| 1798 | /// instructions from the insertion point to the end of the block. The data is | |||||||||
| 1799 | /// used by HoistCommonCodeInSuccs to ensure safety. | |||||||||
| 1800 | static | |||||||||
| 1801 | MachineBasicBlock::iterator findHoistingInsertPosAndDeps(MachineBasicBlock *MBB, | |||||||||
| 1802 | const TargetInstrInfo *TII, | |||||||||
| 1803 | const TargetRegisterInfo *TRI, | |||||||||
| 1804 | SmallSet<unsigned,4> &Uses, | |||||||||
| 1805 | SmallSet<unsigned,4> &Defs) { | |||||||||
| 1806 | MachineBasicBlock::iterator Loc = MBB->getFirstTerminator(); | |||||||||
| 1807 | if (!TII->isUnpredicatedTerminator(*Loc)) | |||||||||
| 1808 | return MBB->end(); | |||||||||
| 1809 | ||||||||||
| 1810 | for (const MachineOperand &MO : Loc->operands()) { | |||||||||
| 1811 | if (!MO.isReg()) | |||||||||
| 1812 | continue; | |||||||||
| 1813 | unsigned Reg = MO.getReg(); | |||||||||
| 1814 | if (!Reg) | |||||||||
| 1815 | continue; | |||||||||
| 1816 | if (MO.isUse()) { | |||||||||
| 1817 | addRegAndItsAliases(Reg, TRI, Uses); | |||||||||
| 1818 | } else { | |||||||||
| 1819 | if (!MO.isDead()) | |||||||||
| 1820 | // Don't try to hoist code in the rare case the terminator defines a | |||||||||
| 1821 | // register that is later used. | |||||||||
| 1822 | return MBB->end(); | |||||||||
| 1823 | ||||||||||
| 1824 | // If the terminator defines a register, make sure we don't hoist | |||||||||
| 1825 | // the instruction whose def might be clobbered by the terminator. | |||||||||
| 1826 | addRegAndItsAliases(Reg, TRI, Defs); | |||||||||
| 1827 | } | |||||||||
| 1828 | } | |||||||||
| 1829 | ||||||||||
| 1830 | if (Uses.empty()) | |||||||||
| 1831 | return Loc; | |||||||||
| 1832 | if (Loc == MBB->begin()) | |||||||||
| 1833 | return MBB->end(); | |||||||||
| 1834 | ||||||||||
| 1835 | // The terminator is probably a conditional branch, try not to separate the | |||||||||
| 1836 | // branch from condition setting instruction. | |||||||||
| 1837 | MachineBasicBlock::iterator PI = | |||||||||
| 1838 | skipDebugInstructionsBackward(std::prev(Loc), MBB->begin()); | |||||||||
| 1839 | ||||||||||
| 1840 | bool IsDef = false; | |||||||||
| 1841 | for (const MachineOperand &MO : PI->operands()) { | |||||||||
| 1842 | // If PI has a regmask operand, it is probably a call. Separate away. | |||||||||
| 1843 | if (MO.isRegMask()) | |||||||||
| 1844 | return Loc; | |||||||||
| 1845 | if (!MO.isReg() || MO.isUse()) | |||||||||
| 1846 | continue; | |||||||||
| 1847 | unsigned Reg = MO.getReg(); | |||||||||
| 1848 | if (!Reg) | |||||||||
| 1849 | continue; | |||||||||
| 1850 | if (Uses.count(Reg)) { | |||||||||
| 1851 | IsDef = true; | |||||||||
| 1852 | break; | |||||||||
| 1853 | } | |||||||||
| 1854 | } | |||||||||
| 1855 | if (!IsDef) | |||||||||
| 1856 | // The condition setting instruction is not just before the conditional | |||||||||
| 1857 | // branch. | |||||||||
| 1858 | return Loc; | |||||||||
| 1859 | ||||||||||
| 1860 | // Be conservative, don't insert instruction above something that may have | |||||||||
| 1861 | // side-effects. And since it's potentially bad to separate flag setting | |||||||||
| 1862 | // instruction from the conditional branch, just abort the optimization | |||||||||
| 1863 | // completely. | |||||||||
| 1864 | // Also avoid moving code above predicated instruction since it's hard to | |||||||||
| 1865 | // reason about register liveness with predicated instruction. | |||||||||
| 1866 | bool DontMoveAcrossStore = true; | |||||||||
| 1867 | if (!PI->isSafeToMove(nullptr, DontMoveAcrossStore) || TII->isPredicated(*PI)) | |||||||||
| 1868 | return MBB->end(); | |||||||||
| 1869 | ||||||||||
| 1870 | // Find out what registers are live. Note this routine is ignoring other live | |||||||||
| 1871 | // registers which are only used by instructions in successor blocks. | |||||||||
| 1872 | for (const MachineOperand &MO : PI->operands()) { | |||||||||
| 1873 | if (!MO.isReg()) | |||||||||
| 1874 | continue; | |||||||||
| 1875 | unsigned Reg = MO.getReg(); | |||||||||
| 1876 | if (!Reg) | |||||||||
| 1877 | continue; | |||||||||
| 1878 | if (MO.isUse()) { | |||||||||
| 1879 | addRegAndItsAliases(Reg, TRI, Uses); | |||||||||
| 1880 | } else { | |||||||||
| 1881 | if (Uses.erase(Reg)) { | |||||||||
| 1882 | if (TargetRegisterInfo::isPhysicalRegister(Reg)) { | |||||||||
| 1883 | for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) | |||||||||
| 1884 | Uses.erase(*SubRegs); // Use sub-registers to be conservative | |||||||||
| 1885 | } | |||||||||
| 1886 | } | |||||||||
| 1887 | addRegAndItsAliases(Reg, TRI, Defs); | |||||||||
| 1888 | } | |||||||||
| 1889 | } | |||||||||
| 1890 | ||||||||||
| 1891 | return PI; | |||||||||
| 1892 | } | |||||||||
| 1893 | ||||||||||
| 1894 | bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) { | |||||||||
| 1895 | MachineBasicBlock *TBB = nullptr, *FBB = nullptr; | |||||||||
| 1896 | SmallVector<MachineOperand, 4> Cond; | |||||||||
| 1897 | if (TII->analyzeBranch(*MBB, TBB, FBB, Cond, true) || !TBB || Cond.empty()) | |||||||||
| 1898 | return false; | |||||||||
| 1899 | ||||||||||
| 1900 | if (!FBB) FBB = findFalseBlock(MBB, TBB); | |||||||||
| 1901 | if (!FBB) | |||||||||
| 1902 | // Malformed bcc? True and false blocks are the same? | |||||||||
| 1903 | return false; | |||||||||
| 1904 | ||||||||||
| 1905 | // Restrict the optimization to cases where MBB is the only predecessor, | |||||||||
| 1906 | // it is an obvious win. | |||||||||
| 1907 | if (TBB->pred_size() > 1 || FBB->pred_size() > 1) | |||||||||
| 1908 | return false; | |||||||||
| 1909 | ||||||||||
| 1910 | // Find a suitable position to hoist the common instructions to. Also figure | |||||||||
| 1911 | // out which registers are used or defined by instructions from the insertion | |||||||||
| 1912 | // point to the end of the block. | |||||||||
| 1913 | SmallSet<unsigned, 4> Uses, Defs; | |||||||||
| 1914 | MachineBasicBlock::iterator Loc = | |||||||||
| 1915 | findHoistingInsertPosAndDeps(MBB, TII, TRI, Uses, Defs); | |||||||||
| 1916 | if (Loc == MBB->end()) | |||||||||
| 1917 | return false; | |||||||||
| 1918 | ||||||||||
| 1919 | bool HasDups = false; | |||||||||
| 1920 | SmallVector<unsigned, 4> LocalDefs, LocalKills; | |||||||||
| 1921 | SmallSet<unsigned, 4> ActiveDefsSet, AllDefsSet; | |||||||||
| 1922 | MachineBasicBlock::iterator TIB = TBB->begin(); | |||||||||
| 1923 | MachineBasicBlock::iterator FIB = FBB->begin(); | |||||||||
| 1924 | MachineBasicBlock::iterator TIE = TBB->end(); | |||||||||
| 1925 | MachineBasicBlock::iterator FIE = FBB->end(); | |||||||||
| 1926 | while (TIB != TIE && FIB != FIE) { | |||||||||
| 1927 | // Skip dbg_value instructions. These do not count. | |||||||||
| 1928 | TIB = skipDebugInstructionsForward(TIB, TIE); | |||||||||
| 1929 | FIB = skipDebugInstructionsForward(FIB, FIE); | |||||||||
| 1930 | if (TIB == TIE || FIB == FIE) | |||||||||
| 1931 | break; | |||||||||
| 1932 | ||||||||||
| 1933 | if (!TIB->isIdenticalTo(*FIB, MachineInstr::CheckKillDead)) | |||||||||
| 1934 | break; | |||||||||
| 1935 | ||||||||||
| 1936 | if (TII->isPredicated(*TIB)) | |||||||||
| 1937 | // Hard to reason about register liveness with predicated instruction. | |||||||||
| 1938 | break; | |||||||||
| 1939 | ||||||||||
| 1940 | bool IsSafe = true; | |||||||||
| 1941 | for (MachineOperand &MO : TIB->operands()) { | |||||||||
| 1942 | // Don't attempt to hoist instructions with register masks. | |||||||||
| 1943 | if (MO.isRegMask()) { | |||||||||
| 1944 | IsSafe = false; | |||||||||
| 1945 | break; | |||||||||
| 1946 | } | |||||||||
| 1947 | if (!MO.isReg()) | |||||||||
| 1948 | continue; | |||||||||
| 1949 | unsigned Reg = MO.getReg(); | |||||||||
| 1950 | if (!Reg) | |||||||||
| 1951 | continue; | |||||||||
| 1952 | if (MO.isDef()) { | |||||||||
| 1953 | if (Uses.count(Reg)) { | |||||||||
| 1954 | // Avoid clobbering a register that's used by the instruction at | |||||||||
| 1955 | // the point of insertion. | |||||||||
| 1956 | IsSafe = false; | |||||||||
| 1957 | break; | |||||||||
| 1958 | } | |||||||||
| 1959 | ||||||||||
| 1960 | if (Defs.count(Reg) && !MO.isDead()) { | |||||||||
| 1961 | // Don't hoist the instruction if the def would be clobber by the | |||||||||
| 1962 | // instruction at the point insertion. FIXME: This is overly | |||||||||
| 1963 | // conservative. It should be possible to hoist the instructions | |||||||||
| 1964 | // in BB2 in the following example: | |||||||||
| 1965 | // BB1: | |||||||||
| 1966 | // r1, eflag = op1 r2, r3 | |||||||||
| 1967 | // brcc eflag | |||||||||
| 1968 | // | |||||||||
| 1969 | // BB2: | |||||||||
| 1970 | // r1 = op2, ... | |||||||||
| 1971 | // = op3, killed r1 | |||||||||
| 1972 | IsSafe = false; | |||||||||
| 1973 | break; | |||||||||
| 1974 | } | |||||||||
| 1975 | } else if (!ActiveDefsSet.count(Reg)) { | |||||||||
| 1976 | if (Defs.count(Reg)) { | |||||||||
| 1977 | // Use is defined by the instruction at the point of insertion. | |||||||||
| 1978 | IsSafe = false; | |||||||||
| 1979 | break; | |||||||||
| 1980 | } | |||||||||
| 1981 | ||||||||||
| 1982 | if (MO.isKill() && Uses.count(Reg)) | |||||||||
| 1983 | // Kills a register that's read by the instruction at the point of | |||||||||
| 1984 | // insertion. Remove the kill marker. | |||||||||
| 1985 | MO.setIsKill(false); | |||||||||
| 1986 | } | |||||||||
| 1987 | } | |||||||||
| 1988 | if (!IsSafe) | |||||||||
| 1989 | break; | |||||||||
| 1990 | ||||||||||
| 1991 | bool DontMoveAcrossStore = true; | |||||||||
| 1992 | if (!TIB->isSafeToMove(nullptr, DontMoveAcrossStore)) | |||||||||
| 1993 | break; | |||||||||
| 1994 | ||||||||||
| 1995 | // Remove kills from ActiveDefsSet, these registers had short live ranges. | |||||||||
| 1996 | for (const MachineOperand &MO : TIB->operands()) { | |||||||||
| 1997 | if (!MO.isReg() || !MO.isUse() || !MO.isKill()) | |||||||||
| 1998 | continue; | |||||||||
| 1999 | unsigned Reg = MO.getReg(); | |||||||||
| 2000 | if (!Reg) | |||||||||
| 2001 | continue; | |||||||||
| 2002 | if (!AllDefsSet.count(Reg)) { | |||||||||
| 2003 | LocalKills.push_back(Reg); | |||||||||
| 2004 | continue; | |||||||||
| 2005 | } | |||||||||
| 2006 | if (TargetRegisterInfo::isPhysicalRegister(Reg)) { | |||||||||
| 2007 | for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) | |||||||||
| 2008 | ActiveDefsSet.erase(*AI); | |||||||||
| 2009 | } else { | |||||||||
| 2010 | ActiveDefsSet.erase(Reg); | |||||||||
| 2011 | } | |||||||||
| 2012 | } | |||||||||
| 2013 | ||||||||||
| 2014 | // Track local defs so we can update liveins. | |||||||||
| 2015 | for (const MachineOperand &MO : TIB->operands()) { | |||||||||
| 2016 | if (!MO.isReg() || !MO.isDef() || MO.isDead()) | |||||||||
| 2017 | continue; | |||||||||
| 2018 | unsigned Reg = MO.getReg(); | |||||||||
| 2019 | if (!Reg || TargetRegisterInfo::isVirtualRegister(Reg)) | |||||||||
| 2020 | continue; | |||||||||
| 2021 | LocalDefs.push_back(Reg); | |||||||||
| 2022 | addRegAndItsAliases(Reg, TRI, ActiveDefsSet); | |||||||||
| 2023 | addRegAndItsAliases(Reg, TRI, AllDefsSet); | |||||||||
| 2024 | } | |||||||||
| 2025 | ||||||||||
| 2026 | HasDups = true; | |||||||||
| 2027 | ++TIB; | |||||||||
| 2028 | ++FIB; | |||||||||
| 2029 | } | |||||||||
| 2030 | ||||||||||
| 2031 | if (!HasDups) | |||||||||
| 2032 | return false; | |||||||||
| 2033 | ||||||||||
| 2034 | MBB->splice(Loc, TBB, TBB->begin(), TIB); | |||||||||
| 2035 | FBB->erase(FBB->begin(), FIB); | |||||||||
| 2036 | ||||||||||
| 2037 | // Update livein's. | |||||||||
| 2038 | bool ChangedLiveIns = false; | |||||||||
| 2039 | for (unsigned i = 0, e = LocalDefs.size(); i != e; ++i) { | |||||||||
| 2040 | unsigned Def = LocalDefs[i]; | |||||||||
| 2041 | if (ActiveDefsSet.count(Def)) { | |||||||||
| 2042 | TBB->addLiveIn(Def); | |||||||||
| 2043 | FBB->addLiveIn(Def); | |||||||||
| 2044 | ChangedLiveIns = true; | |||||||||
| 2045 | } | |||||||||
| 2046 | } | |||||||||
| 2047 | for (unsigned K : LocalKills) { | |||||||||
| 2048 | TBB->removeLiveIn(K); | |||||||||
| 2049 | FBB->removeLiveIn(K); | |||||||||
| 2050 | ChangedLiveIns = true; | |||||||||
| 2051 | } | |||||||||
| 2052 | ||||||||||
| 2053 | if (ChangedLiveIns) { | |||||||||
| 2054 | TBB->sortUniqueLiveIns(); | |||||||||
| 2055 | FBB->sortUniqueLiveIns(); | |||||||||
| 2056 | } | |||||||||
| 2057 | ||||||||||
| 2058 | ++NumHoist; | |||||||||
| 2059 | return true; | |||||||||
| 2060 | } |