| File: | build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp |
| Warning: | line 419, column 7 Value stored to 'BaseReg' is never read |
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| 1 | //===- LocalStackSlotAllocation.cpp - Pre-allocate locals to stack slots --===// |
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | // |
| 9 | // This pass assigns local frame indices to stack slots relative to one another |
| 10 | // and allocates additional base registers to access them when the target |
| 11 | // estimates they are likely to be out of range of stack pointer and frame |
| 12 | // pointer relative addressing. |
| 13 | // |
| 14 | //===----------------------------------------------------------------------===// |
| 15 | |
| 16 | #include "llvm/ADT/SetVector.h" |
| 17 | #include "llvm/ADT/SmallSet.h" |
| 18 | #include "llvm/ADT/SmallVector.h" |
| 19 | #include "llvm/ADT/Statistic.h" |
| 20 | #include "llvm/CodeGen/MachineBasicBlock.h" |
| 21 | #include "llvm/CodeGen/MachineFrameInfo.h" |
| 22 | #include "llvm/CodeGen/MachineFunction.h" |
| 23 | #include "llvm/CodeGen/MachineFunctionPass.h" |
| 24 | #include "llvm/CodeGen/MachineInstr.h" |
| 25 | #include "llvm/CodeGen/MachineOperand.h" |
| 26 | #include "llvm/CodeGen/MachineRegisterInfo.h" |
| 27 | #include "llvm/CodeGen/TargetFrameLowering.h" |
| 28 | #include "llvm/CodeGen/TargetOpcodes.h" |
| 29 | #include "llvm/CodeGen/TargetRegisterInfo.h" |
| 30 | #include "llvm/CodeGen/TargetSubtargetInfo.h" |
| 31 | #include "llvm/InitializePasses.h" |
| 32 | #include "llvm/Pass.h" |
| 33 | #include "llvm/Support/Debug.h" |
| 34 | #include "llvm/Support/ErrorHandling.h" |
| 35 | #include "llvm/Support/raw_ostream.h" |
| 36 | #include <algorithm> |
| 37 | #include <cassert> |
| 38 | #include <cstdint> |
| 39 | #include <tuple> |
| 40 | |
| 41 | using namespace llvm; |
| 42 | |
| 43 | #define DEBUG_TYPE"localstackalloc" "localstackalloc" |
| 44 | |
| 45 | STATISTIC(NumAllocations, "Number of frame indices allocated into local block")static llvm::Statistic NumAllocations = {"localstackalloc", "NumAllocations" , "Number of frame indices allocated into local block"}; |
| 46 | STATISTIC(NumBaseRegisters, "Number of virtual frame base registers allocated")static llvm::Statistic NumBaseRegisters = {"localstackalloc", "NumBaseRegisters", "Number of virtual frame base registers allocated" }; |
| 47 | STATISTIC(NumReplacements, "Number of frame indices references replaced")static llvm::Statistic NumReplacements = {"localstackalloc", "NumReplacements" , "Number of frame indices references replaced"}; |
| 48 | |
| 49 | namespace { |
| 50 | |
| 51 | class FrameRef { |
| 52 | MachineBasicBlock::iterator MI; // Instr referencing the frame |
| 53 | int64_t LocalOffset; // Local offset of the frame idx referenced |
| 54 | int FrameIdx; // The frame index |
| 55 | |
| 56 | // Order reference instruction appears in program. Used to ensure |
| 57 | // deterministic order when multiple instructions may reference the same |
| 58 | // location. |
| 59 | unsigned Order; |
| 60 | |
| 61 | public: |
| 62 | FrameRef(MachineInstr *I, int64_t Offset, int Idx, unsigned Ord) : |
| 63 | MI(I), LocalOffset(Offset), FrameIdx(Idx), Order(Ord) {} |
| 64 | |
| 65 | bool operator<(const FrameRef &RHS) const { |
| 66 | return std::tie(LocalOffset, FrameIdx, Order) < |
| 67 | std::tie(RHS.LocalOffset, RHS.FrameIdx, RHS.Order); |
| 68 | } |
| 69 | |
| 70 | MachineBasicBlock::iterator getMachineInstr() const { return MI; } |
| 71 | int64_t getLocalOffset() const { return LocalOffset; } |
| 72 | int getFrameIndex() const { return FrameIdx; } |
| 73 | }; |
| 74 | |
| 75 | class LocalStackSlotPass: public MachineFunctionPass { |
| 76 | SmallVector<int64_t, 16> LocalOffsets; |
| 77 | |
| 78 | /// StackObjSet - A set of stack object indexes |
| 79 | using StackObjSet = SmallSetVector<int, 8>; |
| 80 | |
| 81 | void AdjustStackOffset(MachineFrameInfo &MFI, int FrameIdx, int64_t &Offset, |
| 82 | bool StackGrowsDown, Align &MaxAlign); |
| 83 | void AssignProtectedObjSet(const StackObjSet &UnassignedObjs, |
| 84 | SmallSet<int, 16> &ProtectedObjs, |
| 85 | MachineFrameInfo &MFI, bool StackGrowsDown, |
| 86 | int64_t &Offset, Align &MaxAlign); |
| 87 | void calculateFrameObjectOffsets(MachineFunction &Fn); |
| 88 | bool insertFrameReferenceRegisters(MachineFunction &Fn); |
| 89 | |
| 90 | public: |
| 91 | static char ID; // Pass identification, replacement for typeid |
| 92 | |
| 93 | explicit LocalStackSlotPass() : MachineFunctionPass(ID) { |
| 94 | initializeLocalStackSlotPassPass(*PassRegistry::getPassRegistry()); |
| 95 | } |
| 96 | |
| 97 | bool runOnMachineFunction(MachineFunction &MF) override; |
| 98 | |
| 99 | void getAnalysisUsage(AnalysisUsage &AU) const override { |
| 100 | AU.setPreservesCFG(); |
| 101 | MachineFunctionPass::getAnalysisUsage(AU); |
| 102 | } |
| 103 | }; |
| 104 | |
| 105 | } // end anonymous namespace |
| 106 | |
| 107 | char LocalStackSlotPass::ID = 0; |
| 108 | |
| 109 | char &llvm::LocalStackSlotAllocationID = LocalStackSlotPass::ID; |
| 110 | INITIALIZE_PASS(LocalStackSlotPass, DEBUG_TYPE,static void *initializeLocalStackSlotPassPassOnce(PassRegistry &Registry) { PassInfo *PI = new PassInfo( "Local Stack Slot Allocation" , "localstackalloc", &LocalStackSlotPass::ID, PassInfo::NormalCtor_t (callDefaultCtor<LocalStackSlotPass>), false, false); Registry .registerPass(*PI, true); return PI; } static llvm::once_flag InitializeLocalStackSlotPassPassFlag; void llvm::initializeLocalStackSlotPassPass (PassRegistry &Registry) { llvm::call_once(InitializeLocalStackSlotPassPassFlag , initializeLocalStackSlotPassPassOnce, std::ref(Registry)); } |
| 111 | "Local Stack Slot Allocation", false, false)static void *initializeLocalStackSlotPassPassOnce(PassRegistry &Registry) { PassInfo *PI = new PassInfo( "Local Stack Slot Allocation" , "localstackalloc", &LocalStackSlotPass::ID, PassInfo::NormalCtor_t (callDefaultCtor<LocalStackSlotPass>), false, false); Registry .registerPass(*PI, true); return PI; } static llvm::once_flag InitializeLocalStackSlotPassPassFlag; void llvm::initializeLocalStackSlotPassPass (PassRegistry &Registry) { llvm::call_once(InitializeLocalStackSlotPassPassFlag , initializeLocalStackSlotPassPassOnce, std::ref(Registry)); } |
| 112 | |
| 113 | bool LocalStackSlotPass::runOnMachineFunction(MachineFunction &MF) { |
| 114 | MachineFrameInfo &MFI = MF.getFrameInfo(); |
| 115 | const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo(); |
| 116 | unsigned LocalObjectCount = MFI.getObjectIndexEnd(); |
| 117 | |
| 118 | // If the target doesn't want/need this pass, or if there are no locals |
| 119 | // to consider, early exit. |
| 120 | if (LocalObjectCount == 0 || !TRI->requiresVirtualBaseRegisters(MF)) |
| 121 | return false; |
| 122 | |
| 123 | // Make sure we have enough space to store the local offsets. |
| 124 | LocalOffsets.resize(MFI.getObjectIndexEnd()); |
| 125 | |
| 126 | // Lay out the local blob. |
| 127 | calculateFrameObjectOffsets(MF); |
| 128 | |
| 129 | // Insert virtual base registers to resolve frame index references. |
| 130 | bool UsedBaseRegs = insertFrameReferenceRegisters(MF); |
| 131 | |
| 132 | // Tell MFI whether any base registers were allocated. PEI will only |
| 133 | // want to use the local block allocations from this pass if there were any. |
| 134 | // Otherwise, PEI can do a bit better job of getting the alignment right |
| 135 | // without a hole at the start since it knows the alignment of the stack |
| 136 | // at the start of local allocation, and this pass doesn't. |
| 137 | MFI.setUseLocalStackAllocationBlock(UsedBaseRegs); |
| 138 | |
| 139 | return true; |
| 140 | } |
| 141 | |
| 142 | /// AdjustStackOffset - Helper function used to adjust the stack frame offset. |
| 143 | void LocalStackSlotPass::AdjustStackOffset(MachineFrameInfo &MFI, int FrameIdx, |
| 144 | int64_t &Offset, bool StackGrowsDown, |
| 145 | Align &MaxAlign) { |
| 146 | // If the stack grows down, add the object size to find the lowest address. |
| 147 | if (StackGrowsDown) |
| 148 | Offset += MFI.getObjectSize(FrameIdx); |
| 149 | |
| 150 | Align Alignment = MFI.getObjectAlign(FrameIdx); |
| 151 | |
| 152 | // If the alignment of this object is greater than that of the stack, then |
| 153 | // increase the stack alignment to match. |
| 154 | MaxAlign = std::max(MaxAlign, Alignment); |
| 155 | |
| 156 | // Adjust to alignment boundary. |
| 157 | Offset = alignTo(Offset, Alignment); |
| 158 | |
| 159 | int64_t LocalOffset = StackGrowsDown ? -Offset : Offset; |
| 160 | LLVM_DEBUG(dbgs() << "Allocate FI(" << FrameIdx << ") to local offset "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("localstackalloc")) { dbgs() << "Allocate FI(" << FrameIdx << ") to local offset " << LocalOffset << "\n"; } } while (false) |
| 161 | << LocalOffset << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("localstackalloc")) { dbgs() << "Allocate FI(" << FrameIdx << ") to local offset " << LocalOffset << "\n"; } } while (false); |
| 162 | // Keep the offset available for base register allocation |
| 163 | LocalOffsets[FrameIdx] = LocalOffset; |
| 164 | // And tell MFI about it for PEI to use later |
| 165 | MFI.mapLocalFrameObject(FrameIdx, LocalOffset); |
| 166 | |
| 167 | if (!StackGrowsDown) |
| 168 | Offset += MFI.getObjectSize(FrameIdx); |
| 169 | |
| 170 | ++NumAllocations; |
| 171 | } |
| 172 | |
| 173 | /// AssignProtectedObjSet - Helper function to assign large stack objects (i.e., |
| 174 | /// those required to be close to the Stack Protector) to stack offsets. |
| 175 | void LocalStackSlotPass::AssignProtectedObjSet( |
| 176 | const StackObjSet &UnassignedObjs, SmallSet<int, 16> &ProtectedObjs, |
| 177 | MachineFrameInfo &MFI, bool StackGrowsDown, int64_t &Offset, |
| 178 | Align &MaxAlign) { |
| 179 | for (int i : UnassignedObjs) { |
| 180 | AdjustStackOffset(MFI, i, Offset, StackGrowsDown, MaxAlign); |
| 181 | ProtectedObjs.insert(i); |
| 182 | } |
| 183 | } |
| 184 | |
| 185 | /// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the |
| 186 | /// abstract stack objects. |
| 187 | void LocalStackSlotPass::calculateFrameObjectOffsets(MachineFunction &Fn) { |
| 188 | // Loop over all of the stack objects, assigning sequential addresses... |
| 189 | MachineFrameInfo &MFI = Fn.getFrameInfo(); |
| 190 | const TargetFrameLowering &TFI = *Fn.getSubtarget().getFrameLowering(); |
| 191 | bool StackGrowsDown = |
| 192 | TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown; |
| 193 | int64_t Offset = 0; |
| 194 | Align MaxAlign; |
| 195 | |
| 196 | // Make sure that the stack protector comes before the local variables on the |
| 197 | // stack. |
| 198 | SmallSet<int, 16> ProtectedObjs; |
| 199 | if (MFI.hasStackProtectorIndex()) { |
| 200 | int StackProtectorFI = MFI.getStackProtectorIndex(); |
| 201 | |
| 202 | // We need to make sure we didn't pre-allocate the stack protector when |
| 203 | // doing this. |
| 204 | // If we already have a stack protector, this will re-assign it to a slot |
| 205 | // that is **not** covering the protected objects. |
| 206 | assert(!MFI.isObjectPreAllocated(StackProtectorFI) &&(static_cast <bool> (!MFI.isObjectPreAllocated(StackProtectorFI ) && "Stack protector pre-allocated in LocalStackSlotAllocation" ) ? void (0) : __assert_fail ("!MFI.isObjectPreAllocated(StackProtectorFI) && \"Stack protector pre-allocated in LocalStackSlotAllocation\"" , "llvm/lib/CodeGen/LocalStackSlotAllocation.cpp", 207, __extension__ __PRETTY_FUNCTION__)) |
| 207 | "Stack protector pre-allocated in LocalStackSlotAllocation")(static_cast <bool> (!MFI.isObjectPreAllocated(StackProtectorFI ) && "Stack protector pre-allocated in LocalStackSlotAllocation" ) ? void (0) : __assert_fail ("!MFI.isObjectPreAllocated(StackProtectorFI) && \"Stack protector pre-allocated in LocalStackSlotAllocation\"" , "llvm/lib/CodeGen/LocalStackSlotAllocation.cpp", 207, __extension__ __PRETTY_FUNCTION__)); |
| 208 | |
| 209 | StackObjSet LargeArrayObjs; |
| 210 | StackObjSet SmallArrayObjs; |
| 211 | StackObjSet AddrOfObjs; |
| 212 | |
| 213 | // Only place the stack protector in the local stack area if the target |
| 214 | // allows it. |
| 215 | if (TFI.isStackIdSafeForLocalArea(MFI.getStackID(StackProtectorFI))) |
| 216 | AdjustStackOffset(MFI, StackProtectorFI, Offset, StackGrowsDown, |
| 217 | MaxAlign); |
| 218 | |
| 219 | // Assign large stack objects first. |
| 220 | for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) { |
| 221 | if (MFI.isDeadObjectIndex(i)) |
| 222 | continue; |
| 223 | if (StackProtectorFI == (int)i) |
| 224 | continue; |
| 225 | if (!TFI.isStackIdSafeForLocalArea(MFI.getStackID(i))) |
| 226 | continue; |
| 227 | |
| 228 | switch (MFI.getObjectSSPLayout(i)) { |
| 229 | case MachineFrameInfo::SSPLK_None: |
| 230 | continue; |
| 231 | case MachineFrameInfo::SSPLK_SmallArray: |
| 232 | SmallArrayObjs.insert(i); |
| 233 | continue; |
| 234 | case MachineFrameInfo::SSPLK_AddrOf: |
| 235 | AddrOfObjs.insert(i); |
| 236 | continue; |
| 237 | case MachineFrameInfo::SSPLK_LargeArray: |
| 238 | LargeArrayObjs.insert(i); |
| 239 | continue; |
| 240 | } |
| 241 | llvm_unreachable("Unexpected SSPLayoutKind.")::llvm::llvm_unreachable_internal("Unexpected SSPLayoutKind." , "llvm/lib/CodeGen/LocalStackSlotAllocation.cpp", 241); |
| 242 | } |
| 243 | |
| 244 | AssignProtectedObjSet(LargeArrayObjs, ProtectedObjs, MFI, StackGrowsDown, |
| 245 | Offset, MaxAlign); |
| 246 | AssignProtectedObjSet(SmallArrayObjs, ProtectedObjs, MFI, StackGrowsDown, |
| 247 | Offset, MaxAlign); |
| 248 | AssignProtectedObjSet(AddrOfObjs, ProtectedObjs, MFI, StackGrowsDown, |
| 249 | Offset, MaxAlign); |
| 250 | } |
| 251 | |
| 252 | // Then assign frame offsets to stack objects that are not used to spill |
| 253 | // callee saved registers. |
| 254 | for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) { |
| 255 | if (MFI.isDeadObjectIndex(i)) |
| 256 | continue; |
| 257 | if (MFI.getStackProtectorIndex() == (int)i) |
| 258 | continue; |
| 259 | if (ProtectedObjs.count(i)) |
| 260 | continue; |
| 261 | if (!TFI.isStackIdSafeForLocalArea(MFI.getStackID(i))) |
| 262 | continue; |
| 263 | |
| 264 | AdjustStackOffset(MFI, i, Offset, StackGrowsDown, MaxAlign); |
| 265 | } |
| 266 | |
| 267 | // Remember how big this blob of stack space is |
| 268 | MFI.setLocalFrameSize(Offset); |
| 269 | MFI.setLocalFrameMaxAlign(MaxAlign); |
| 270 | } |
| 271 | |
| 272 | static inline bool |
| 273 | lookupCandidateBaseReg(unsigned BaseReg, |
| 274 | int64_t BaseOffset, |
| 275 | int64_t FrameSizeAdjust, |
| 276 | int64_t LocalFrameOffset, |
| 277 | const MachineInstr &MI, |
| 278 | const TargetRegisterInfo *TRI) { |
| 279 | // Check if the relative offset from the where the base register references |
| 280 | // to the target address is in range for the instruction. |
| 281 | int64_t Offset = FrameSizeAdjust + LocalFrameOffset - BaseOffset; |
| 282 | return TRI->isFrameOffsetLegal(&MI, BaseReg, Offset); |
| 283 | } |
| 284 | |
| 285 | bool LocalStackSlotPass::insertFrameReferenceRegisters(MachineFunction &Fn) { |
| 286 | // Scan the function's instructions looking for frame index references. |
| 287 | // For each, ask the target if it wants a virtual base register for it |
| 288 | // based on what we can tell it about where the local will end up in the |
| 289 | // stack frame. If it wants one, re-use a suitable one we've previously |
| 290 | // allocated, or if there isn't one that fits the bill, allocate a new one |
| 291 | // and ask the target to create a defining instruction for it. |
| 292 | bool UsedBaseReg = false; |
| 293 | |
| 294 | MachineFrameInfo &MFI = Fn.getFrameInfo(); |
| 295 | const TargetRegisterInfo *TRI = Fn.getSubtarget().getRegisterInfo(); |
| 296 | const TargetFrameLowering &TFI = *Fn.getSubtarget().getFrameLowering(); |
| 297 | bool StackGrowsDown = |
| 298 | TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown; |
| 299 | |
| 300 | // Collect all of the instructions in the block that reference |
| 301 | // a frame index. Also store the frame index referenced to ease later |
| 302 | // lookup. (For any insn that has more than one FI reference, we arbitrarily |
| 303 | // choose the first one). |
| 304 | SmallVector<FrameRef, 64> FrameReferenceInsns; |
| 305 | |
| 306 | unsigned Order = 0; |
| 307 | |
| 308 | for (MachineBasicBlock &BB : Fn) { |
| 309 | for (MachineInstr &MI : BB) { |
| 310 | // Debug value, stackmap and patchpoint instructions can't be out of |
| 311 | // range, so they don't need any updates. |
| 312 | if (MI.isDebugInstr() || MI.getOpcode() == TargetOpcode::STATEPOINT || |
| 313 | MI.getOpcode() == TargetOpcode::STACKMAP || |
| 314 | MI.getOpcode() == TargetOpcode::PATCHPOINT) |
| 315 | continue; |
| 316 | |
| 317 | // For now, allocate the base register(s) within the basic block |
| 318 | // where they're used, and don't try to keep them around outside |
| 319 | // of that. It may be beneficial to try sharing them more broadly |
| 320 | // than that, but the increased register pressure makes that a |
| 321 | // tricky thing to balance. Investigate if re-materializing these |
| 322 | // becomes an issue. |
| 323 | for (const MachineOperand &MO : MI.operands()) { |
| 324 | // Consider replacing all frame index operands that reference |
| 325 | // an object allocated in the local block. |
| 326 | if (MO.isFI()) { |
| 327 | // Don't try this with values not in the local block. |
| 328 | if (!MFI.isObjectPreAllocated(MO.getIndex())) |
| 329 | break; |
| 330 | int Idx = MO.getIndex(); |
| 331 | int64_t LocalOffset = LocalOffsets[Idx]; |
| 332 | if (!TRI->needsFrameBaseReg(&MI, LocalOffset)) |
| 333 | break; |
| 334 | FrameReferenceInsns.push_back(FrameRef(&MI, LocalOffset, Idx, Order++)); |
| 335 | break; |
| 336 | } |
| 337 | } |
| 338 | } |
| 339 | } |
| 340 | |
| 341 | // Sort the frame references by local offset. |
| 342 | // Use frame index as a tie-breaker in case MI's have the same offset. |
| 343 | llvm::sort(FrameReferenceInsns); |
| 344 | |
| 345 | MachineBasicBlock *Entry = &Fn.front(); |
| 346 | |
| 347 | unsigned BaseReg = 0; |
| 348 | int64_t BaseOffset = 0; |
| 349 | |
| 350 | // Loop through the frame references and allocate for them as necessary. |
| 351 | for (int ref = 0, e = FrameReferenceInsns.size(); ref < e ; ++ref) { |
| 352 | FrameRef &FR = FrameReferenceInsns[ref]; |
| 353 | MachineInstr &MI = *FR.getMachineInstr(); |
| 354 | int64_t LocalOffset = FR.getLocalOffset(); |
| 355 | int FrameIdx = FR.getFrameIndex(); |
| 356 | assert(MFI.isObjectPreAllocated(FrameIdx) &&(static_cast <bool> (MFI.isObjectPreAllocated(FrameIdx) && "Only pre-allocated locals expected!") ? void (0) : __assert_fail ("MFI.isObjectPreAllocated(FrameIdx) && \"Only pre-allocated locals expected!\"" , "llvm/lib/CodeGen/LocalStackSlotAllocation.cpp", 357, __extension__ __PRETTY_FUNCTION__)) |
| 357 | "Only pre-allocated locals expected!")(static_cast <bool> (MFI.isObjectPreAllocated(FrameIdx) && "Only pre-allocated locals expected!") ? void (0) : __assert_fail ("MFI.isObjectPreAllocated(FrameIdx) && \"Only pre-allocated locals expected!\"" , "llvm/lib/CodeGen/LocalStackSlotAllocation.cpp", 357, __extension__ __PRETTY_FUNCTION__)); |
| 358 | |
| 359 | // We need to keep the references to the stack protector slot through frame |
| 360 | // index operands so that it gets resolved by PEI rather than this pass. |
| 361 | // This avoids accesses to the stack protector though virtual base |
| 362 | // registers, and forces PEI to address it using fp/sp/bp. |
| 363 | if (MFI.hasStackProtectorIndex() && |
| 364 | FrameIdx == MFI.getStackProtectorIndex()) |
| 365 | continue; |
| 366 | |
| 367 | LLVM_DEBUG(dbgs() << "Considering: " << MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("localstackalloc")) { dbgs() << "Considering: " << MI; } } while (false); |
| 368 | |
| 369 | unsigned idx = 0; |
| 370 | for (unsigned f = MI.getNumOperands(); idx != f; ++idx) { |
| 371 | if (!MI.getOperand(idx).isFI()) |
| 372 | continue; |
| 373 | |
| 374 | if (FrameIdx == MI.getOperand(idx).getIndex()) |
| 375 | break; |
| 376 | } |
| 377 | |
| 378 | assert(idx < MI.getNumOperands() && "Cannot find FI operand")(static_cast <bool> (idx < MI.getNumOperands() && "Cannot find FI operand") ? void (0) : __assert_fail ("idx < MI.getNumOperands() && \"Cannot find FI operand\"" , "llvm/lib/CodeGen/LocalStackSlotAllocation.cpp", 378, __extension__ __PRETTY_FUNCTION__)); |
| 379 | |
| 380 | int64_t Offset = 0; |
| 381 | int64_t FrameSizeAdjust = StackGrowsDown ? MFI.getLocalFrameSize() : 0; |
| 382 | |
| 383 | LLVM_DEBUG(dbgs() << " Replacing FI in: " << MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("localstackalloc")) { dbgs() << " Replacing FI in: " << MI; } } while (false); |
| 384 | |
| 385 | // If we have a suitable base register available, use it; otherwise |
| 386 | // create a new one. Note that any offset encoded in the |
| 387 | // instruction itself will be taken into account by the target, |
| 388 | // so we don't have to adjust for it here when reusing a base |
| 389 | // register. |
| 390 | if (UsedBaseReg && |
| 391 | lookupCandidateBaseReg(BaseReg, BaseOffset, FrameSizeAdjust, |
| 392 | LocalOffset, MI, TRI)) { |
| 393 | LLVM_DEBUG(dbgs() << " Reusing base register " << BaseReg << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("localstackalloc")) { dbgs() << " Reusing base register " << BaseReg << "\n"; } } while (false); |
| 394 | // We found a register to reuse. |
| 395 | Offset = FrameSizeAdjust + LocalOffset - BaseOffset; |
| 396 | } else { |
| 397 | // No previously defined register was in range, so create a new one. |
| 398 | int64_t InstrOffset = TRI->getFrameIndexInstrOffset(&MI, idx); |
| 399 | |
| 400 | int64_t PrevBaseOffset = BaseOffset; |
| 401 | BaseOffset = FrameSizeAdjust + LocalOffset + InstrOffset; |
| 402 | |
| 403 | // We'd like to avoid creating single-use virtual base registers. |
| 404 | // Because the FrameRefs are in sorted order, and we've already |
| 405 | // processed all FrameRefs before this one, just check whether or not |
| 406 | // the next FrameRef will be able to reuse this new register. If not, |
| 407 | // then don't bother creating it. |
| 408 | if (ref + 1 >= e || |
| 409 | !lookupCandidateBaseReg( |
| 410 | BaseReg, BaseOffset, FrameSizeAdjust, |
| 411 | FrameReferenceInsns[ref + 1].getLocalOffset(), |
| 412 | *FrameReferenceInsns[ref + 1].getMachineInstr(), TRI)) { |
| 413 | BaseOffset = PrevBaseOffset; |
| 414 | continue; |
| 415 | } |
| 416 | |
| 417 | const MachineFunction *MF = MI.getMF(); |
| 418 | const TargetRegisterClass *RC = TRI->getPointerRegClass(*MF); |
| 419 | BaseReg = Fn.getRegInfo().createVirtualRegister(RC); |
Value stored to 'BaseReg' is never read | |
| 420 | |
| 421 | LLVM_DEBUG(dbgs() << " Materializing base register"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("localstackalloc")) { dbgs() << " Materializing base register" << " at frame local offset " << LocalOffset + InstrOffset ; } } while (false) |
| 422 | << " at frame local offset "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("localstackalloc")) { dbgs() << " Materializing base register" << " at frame local offset " << LocalOffset + InstrOffset ; } } while (false) |
| 423 | << LocalOffset + InstrOffset)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("localstackalloc")) { dbgs() << " Materializing base register" << " at frame local offset " << LocalOffset + InstrOffset ; } } while (false); |
| 424 | |
| 425 | // Tell the target to insert the instruction to initialize |
| 426 | // the base register. |
| 427 | // MachineBasicBlock::iterator InsertionPt = Entry->begin(); |
| 428 | BaseReg = TRI->materializeFrameBaseRegister(Entry, FrameIdx, InstrOffset); |
| 429 | |
| 430 | LLVM_DEBUG(dbgs() << " into " << printReg(BaseReg, TRI) << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("localstackalloc")) { dbgs() << " into " << printReg (BaseReg, TRI) << '\n'; } } while (false); |
| 431 | |
| 432 | // The base register already includes any offset specified |
| 433 | // by the instruction, so account for that so it doesn't get |
| 434 | // applied twice. |
| 435 | Offset = -InstrOffset; |
| 436 | |
| 437 | ++NumBaseRegisters; |
| 438 | UsedBaseReg = true; |
| 439 | } |
| 440 | assert(BaseReg != 0 && "Unable to allocate virtual base register!")(static_cast <bool> (BaseReg != 0 && "Unable to allocate virtual base register!" ) ? void (0) : __assert_fail ("BaseReg != 0 && \"Unable to allocate virtual base register!\"" , "llvm/lib/CodeGen/LocalStackSlotAllocation.cpp", 440, __extension__ __PRETTY_FUNCTION__)); |
| 441 | |
| 442 | // Modify the instruction to use the new base register rather |
| 443 | // than the frame index operand. |
| 444 | TRI->resolveFrameIndex(MI, BaseReg, Offset); |
| 445 | LLVM_DEBUG(dbgs() << "Resolved: " << MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType ("localstackalloc")) { dbgs() << "Resolved: " << MI ; } } while (false); |
| 446 | |
| 447 | ++NumReplacements; |
| 448 | } |
| 449 | |
| 450 | return UsedBaseReg; |
| 451 | } |