1 //===-- MachineFrameInfo.cpp ---------------------------------------------===// 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 /// \file Implements MachineFrameInfo that manages the stack frame. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "llvm/CodeGen/MachineFrameInfo.h" 14 15 #include "llvm/ADT/BitVector.h" 16 #include "llvm/CodeGen/MachineFunction.h" 17 #include "llvm/CodeGen/MachineRegisterInfo.h" 18 #include "llvm/CodeGen/TargetFrameLowering.h" 19 #include "llvm/CodeGen/TargetInstrInfo.h" 20 #include "llvm/CodeGen/TargetRegisterInfo.h" 21 #include "llvm/CodeGen/TargetSubtargetInfo.h" 22 #include "llvm/Config/llvm-config.h" 23 #include "llvm/Support/Debug.h" 24 #include "llvm/Support/raw_ostream.h" 25 #include <cassert> 26 27 #define DEBUG_TYPE "codegen" 28 29 using namespace llvm; 30 31 void MachineFrameInfo::ensureMaxAlignment(Align Alignment) { 32 if (!StackRealignable) 33 assert(Alignment <= StackAlignment && 34 "For targets without stack realignment, Alignment is out of limit!"); 35 if (MaxAlignment < Alignment) 36 MaxAlignment = Alignment; 37 } 38 39 /// Clamp the alignment if requested and emit a warning. 40 static inline Align clampStackAlignment(bool ShouldClamp, Align Alignment, 41 Align StackAlignment) { 42 if (!ShouldClamp || Alignment <= StackAlignment) 43 return Alignment; 44 LLVM_DEBUG(dbgs() << "Warning: requested alignment " << Alignment.value() 45 << " exceeds the stack alignment " << StackAlignment.value() 46 << " when stack realignment is off" << '\n'); 47 return StackAlignment; 48 } 49 50 int MachineFrameInfo::CreateStackObject(uint64_t Size, Align Alignment, 51 bool IsSpillSlot, 52 const AllocaInst *Alloca, 53 uint8_t StackID) { 54 assert(Size != 0 && "Cannot allocate zero size stack objects!"); 55 Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment); 56 Objects.push_back(StackObject(Size, Alignment, 0, false, IsSpillSlot, Alloca, 57 !IsSpillSlot, StackID)); 58 int Index = (int)Objects.size() - NumFixedObjects - 1; 59 assert(Index >= 0 && "Bad frame index!"); 60 if (StackID == 0) 61 ensureMaxAlignment(Alignment); 62 return Index; 63 } 64 65 int MachineFrameInfo::CreateSpillStackObject(uint64_t Size, Align Alignment) { 66 Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment); 67 CreateStackObject(Size, Alignment, true); 68 int Index = (int)Objects.size() - NumFixedObjects - 1; 69 ensureMaxAlignment(Alignment); 70 return Index; 71 } 72 73 int MachineFrameInfo::CreateVariableSizedObject(Align Alignment, 74 const AllocaInst *Alloca) { 75 HasVarSizedObjects = true; 76 Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment); 77 Objects.push_back(StackObject(0, Alignment, 0, false, false, Alloca, true)); 78 ensureMaxAlignment(Alignment); 79 return (int)Objects.size()-NumFixedObjects-1; 80 } 81 82 int MachineFrameInfo::CreateFixedObject(uint64_t Size, int64_t SPOffset, 83 bool IsImmutable, bool IsAliased) { 84 assert(Size != 0 && "Cannot allocate zero size fixed stack objects!"); 85 // The alignment of the frame index can be determined from its offset from 86 // the incoming frame position. If the frame object is at offset 32 and 87 // the stack is guaranteed to be 16-byte aligned, then we know that the 88 // object is 16-byte aligned. Note that unlike the non-fixed case, if the 89 // stack needs realignment, we can't assume that the stack will in fact be 90 // aligned. 91 Align Alignment = 92 commonAlignment(ForcedRealign ? Align(1) : StackAlignment, SPOffset); 93 Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment); 94 Objects.insert(Objects.begin(), 95 StackObject(Size, Alignment, SPOffset, IsImmutable, 96 /*IsSpillSlot=*/false, /*Alloca=*/nullptr, 97 IsAliased)); 98 return -++NumFixedObjects; 99 } 100 101 int MachineFrameInfo::CreateFixedSpillStackObject(uint64_t Size, 102 int64_t SPOffset, 103 bool IsImmutable) { 104 Align Alignment = 105 commonAlignment(ForcedRealign ? Align(1) : StackAlignment, SPOffset); 106 Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment); 107 Objects.insert(Objects.begin(), 108 StackObject(Size, Alignment, SPOffset, IsImmutable, 109 /*IsSpillSlot=*/true, /*Alloca=*/nullptr, 110 /*IsAliased=*/false)); 111 return -++NumFixedObjects; 112 } 113 114 BitVector MachineFrameInfo::getPristineRegs(const MachineFunction &MF) const { 115 const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo(); 116 BitVector BV(TRI->getNumRegs()); 117 118 // Before CSI is calculated, no registers are considered pristine. They can be 119 // freely used and PEI will make sure they are saved. 120 if (!isCalleeSavedInfoValid()) 121 return BV; 122 123 const MachineRegisterInfo &MRI = MF.getRegInfo(); 124 for (const MCPhysReg *CSR = MRI.getCalleeSavedRegs(); CSR && *CSR; 125 ++CSR) 126 BV.set(*CSR); 127 128 // Saved CSRs are not pristine. 129 for (auto &I : getCalleeSavedInfo()) 130 for (MCSubRegIterator S(I.getReg(), TRI, true); S.isValid(); ++S) 131 BV.reset(*S); 132 133 return BV; 134 } 135 136 uint64_t MachineFrameInfo::estimateStackSize(const MachineFunction &MF) const { 137 const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering(); 138 const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo(); 139 Align MaxAlign = getMaxAlign(); 140 int64_t Offset = 0; 141 142 // This code is very, very similar to PEI::calculateFrameObjectOffsets(). 143 // It really should be refactored to share code. Until then, changes 144 // should keep in mind that there's tight coupling between the two. 145 146 for (int i = getObjectIndexBegin(); i != 0; ++i) { 147 // Only estimate stack size of default stack. 148 if (getStackID(i) != TargetStackID::Default) 149 continue; 150 int64_t FixedOff = -getObjectOffset(i); 151 if (FixedOff > Offset) Offset = FixedOff; 152 } 153 for (unsigned i = 0, e = getObjectIndexEnd(); i != e; ++i) { 154 // Only estimate stack size of live objects on default stack. 155 if (isDeadObjectIndex(i) || getStackID(i) != TargetStackID::Default) 156 continue; 157 Offset += getObjectSize(i); 158 Align Alignment = getObjectAlign(i); 159 // Adjust to alignment boundary 160 Offset = alignTo(Offset, Alignment); 161 162 MaxAlign = std::max(Alignment, MaxAlign); 163 } 164 165 if (adjustsStack() && TFI->hasReservedCallFrame(MF)) 166 Offset += getMaxCallFrameSize(); 167 168 // Round up the size to a multiple of the alignment. If the function has 169 // any calls or alloca's, align to the target's StackAlignment value to 170 // ensure that the callee's frame or the alloca data is suitably aligned; 171 // otherwise, for leaf functions, align to the TransientStackAlignment 172 // value. 173 Align StackAlign; 174 if (adjustsStack() || hasVarSizedObjects() || 175 (RegInfo->needsStackRealignment(MF) && getObjectIndexEnd() != 0)) 176 StackAlign = TFI->getStackAlign(); 177 else 178 StackAlign = TFI->getTransientStackAlign(); 179 180 // If the frame pointer is eliminated, all frame offsets will be relative to 181 // SP not FP. Align to MaxAlign so this works. 182 StackAlign = std::max(StackAlign, MaxAlign); 183 return alignTo(Offset, StackAlign); 184 } 185 186 void MachineFrameInfo::computeMaxCallFrameSize(const MachineFunction &MF) { 187 const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); 188 unsigned FrameSetupOpcode = TII.getCallFrameSetupOpcode(); 189 unsigned FrameDestroyOpcode = TII.getCallFrameDestroyOpcode(); 190 assert(FrameSetupOpcode != ~0u && FrameDestroyOpcode != ~0u && 191 "Can only compute MaxCallFrameSize if Setup/Destroy opcode are known"); 192 193 MaxCallFrameSize = 0; 194 for (const MachineBasicBlock &MBB : MF) { 195 for (const MachineInstr &MI : MBB) { 196 unsigned Opcode = MI.getOpcode(); 197 if (Opcode == FrameSetupOpcode || Opcode == FrameDestroyOpcode) { 198 unsigned Size = TII.getFrameSize(MI); 199 MaxCallFrameSize = std::max(MaxCallFrameSize, Size); 200 AdjustsStack = true; 201 } else if (MI.isInlineAsm()) { 202 // Some inline asm's need a stack frame, as indicated by operand 1. 203 unsigned ExtraInfo = MI.getOperand(InlineAsm::MIOp_ExtraInfo).getImm(); 204 if (ExtraInfo & InlineAsm::Extra_IsAlignStack) 205 AdjustsStack = true; 206 } 207 } 208 } 209 } 210 211 void MachineFrameInfo::print(const MachineFunction &MF, raw_ostream &OS) const{ 212 if (Objects.empty()) return; 213 214 const TargetFrameLowering *FI = MF.getSubtarget().getFrameLowering(); 215 int ValOffset = (FI ? FI->getOffsetOfLocalArea() : 0); 216 217 OS << "Frame Objects:\n"; 218 219 for (unsigned i = 0, e = Objects.size(); i != e; ++i) { 220 const StackObject &SO = Objects[i]; 221 OS << " fi#" << (int)(i-NumFixedObjects) << ": "; 222 223 if (SO.StackID != 0) 224 OS << "id=" << static_cast<unsigned>(SO.StackID) << ' '; 225 226 if (SO.Size == ~0ULL) { 227 OS << "dead\n"; 228 continue; 229 } 230 if (SO.Size == 0) 231 OS << "variable sized"; 232 else 233 OS << "size=" << SO.Size; 234 OS << ", align=" << SO.Alignment.value(); 235 236 if (i < NumFixedObjects) 237 OS << ", fixed"; 238 if (i < NumFixedObjects || SO.SPOffset != -1) { 239 int64_t Off = SO.SPOffset - ValOffset; 240 OS << ", at location [SP"; 241 if (Off > 0) 242 OS << "+" << Off; 243 else if (Off < 0) 244 OS << Off; 245 OS << "]"; 246 } 247 OS << "\n"; 248 } 249 } 250 251 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 252 LLVM_DUMP_METHOD void MachineFrameInfo::dump(const MachineFunction &MF) const { 253 print(MF, dbgs()); 254 } 255 #endif 256