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(unsigned Align) { 32 if (!StackRealignable) 33 assert(Align <= StackAlignment && 34 "For targets without stack realignment, Align is out of limit!"); 35 if (MaxAlignment < Align) MaxAlignment = Align; 36 } 37 38 /// Clamp the alignment if requested and emit a warning. 39 static inline unsigned clampStackAlignment(bool ShouldClamp, unsigned Align, 40 unsigned StackAlign) { 41 if (!ShouldClamp || Align <= StackAlign) 42 return Align; 43 LLVM_DEBUG(dbgs() << "Warning: requested alignment " << Align 44 << " exceeds the stack alignment " << StackAlign 45 << " when stack realignment is off" << '\n'); 46 return StackAlign; 47 } 48 49 int MachineFrameInfo::CreateStackObject(uint64_t Size, unsigned Alignment, 50 bool IsSpillSlot, 51 const AllocaInst *Alloca, 52 uint8_t StackID) { 53 assert(Size != 0 && "Cannot allocate zero size stack objects!"); 54 Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment); 55 Objects.push_back(StackObject(Size, Alignment, 0, false, IsSpillSlot, Alloca, 56 !IsSpillSlot, StackID)); 57 int Index = (int)Objects.size() - NumFixedObjects - 1; 58 assert(Index >= 0 && "Bad frame index!"); 59 if (StackID == 0) 60 ensureMaxAlignment(Alignment); 61 return Index; 62 } 63 64 int MachineFrameInfo::CreateSpillStackObject(uint64_t Size, 65 unsigned 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(unsigned 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 unsigned Alignment = MinAlign(SPOffset, ForcedRealign ? 1 : StackAlignment); 92 Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment); 93 Objects.insert(Objects.begin(), 94 StackObject(Size, Alignment, SPOffset, IsImmutable, 95 /*IsSpillSlot=*/false, /*Alloca=*/nullptr, 96 IsAliased)); 97 return -++NumFixedObjects; 98 } 99 100 int MachineFrameInfo::CreateFixedSpillStackObject(uint64_t Size, 101 int64_t SPOffset, 102 bool IsImmutable) { 103 unsigned Alignment = MinAlign(SPOffset, ForcedRealign ? 1 : StackAlignment); 104 Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment); 105 Objects.insert(Objects.begin(), 106 StackObject(Size, Alignment, SPOffset, IsImmutable, 107 /*IsSpillSlot=*/true, /*Alloca=*/nullptr, 108 /*IsAliased=*/false)); 109 return -++NumFixedObjects; 110 } 111 112 BitVector MachineFrameInfo::getPristineRegs(const MachineFunction &MF) const { 113 const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo(); 114 BitVector BV(TRI->getNumRegs()); 115 116 // Before CSI is calculated, no registers are considered pristine. They can be 117 // freely used and PEI will make sure they are saved. 118 if (!isCalleeSavedInfoValid()) 119 return BV; 120 121 const MachineRegisterInfo &MRI = MF.getRegInfo(); 122 for (const MCPhysReg *CSR = MRI.getCalleeSavedRegs(); CSR && *CSR; 123 ++CSR) 124 BV.set(*CSR); 125 126 // Saved CSRs are not pristine. 127 for (auto &I : getCalleeSavedInfo()) 128 for (MCSubRegIterator S(I.getReg(), TRI, true); S.isValid(); ++S) 129 BV.reset(*S); 130 131 return BV; 132 } 133 134 unsigned MachineFrameInfo::estimateStackSize(const MachineFunction &MF) const { 135 const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering(); 136 const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo(); 137 unsigned MaxAlign = getMaxAlignment(); 138 int Offset = 0; 139 140 // This code is very, very similar to PEI::calculateFrameObjectOffsets(). 141 // It really should be refactored to share code. Until then, changes 142 // should keep in mind that there's tight coupling between the two. 143 144 for (int i = getObjectIndexBegin(); i != 0; ++i) { 145 // Only estimate stack size of default stack. 146 if (getStackID(i) != TargetStackID::Default) 147 continue; 148 int FixedOff = -getObjectOffset(i); 149 if (FixedOff > Offset) Offset = FixedOff; 150 } 151 for (unsigned i = 0, e = getObjectIndexEnd(); i != e; ++i) { 152 // Only estimate stack size of live objects on default stack. 153 if (isDeadObjectIndex(i) || getStackID(i) != TargetStackID::Default) 154 continue; 155 Offset += getObjectSize(i); 156 unsigned Align = getObjectAlignment(i); 157 // Adjust to alignment boundary 158 Offset = (Offset+Align-1)/Align*Align; 159 160 MaxAlign = std::max(Align, MaxAlign); 161 } 162 163 if (adjustsStack() && TFI->hasReservedCallFrame(MF)) 164 Offset += getMaxCallFrameSize(); 165 166 // Round up the size to a multiple of the alignment. If the function has 167 // any calls or alloca's, align to the target's StackAlignment value to 168 // ensure that the callee's frame or the alloca data is suitably aligned; 169 // otherwise, for leaf functions, align to the TransientStackAlignment 170 // value. 171 unsigned StackAlign; 172 if (adjustsStack() || hasVarSizedObjects() || 173 (RegInfo->needsStackRealignment(MF) && getObjectIndexEnd() != 0)) 174 StackAlign = TFI->getStackAlignment(); 175 else 176 StackAlign = TFI->getTransientStackAlignment(); 177 178 // If the frame pointer is eliminated, all frame offsets will be relative to 179 // SP not FP. Align to MaxAlign so this works. 180 StackAlign = std::max(StackAlign, MaxAlign); 181 unsigned AlignMask = StackAlign - 1; 182 Offset = (Offset + AlignMask) & ~uint64_t(AlignMask); 183 184 return (unsigned)Offset; 185 } 186 187 void MachineFrameInfo::computeMaxCallFrameSize(const MachineFunction &MF) { 188 const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); 189 unsigned FrameSetupOpcode = TII.getCallFrameSetupOpcode(); 190 unsigned FrameDestroyOpcode = TII.getCallFrameDestroyOpcode(); 191 assert(FrameSetupOpcode != ~0u && FrameDestroyOpcode != ~0u && 192 "Can only compute MaxCallFrameSize if Setup/Destroy opcode are known"); 193 194 MaxCallFrameSize = 0; 195 for (const MachineBasicBlock &MBB : MF) { 196 for (const MachineInstr &MI : MBB) { 197 unsigned Opcode = MI.getOpcode(); 198 if (Opcode == FrameSetupOpcode || Opcode == FrameDestroyOpcode) { 199 unsigned Size = TII.getFrameSize(MI); 200 MaxCallFrameSize = std::max(MaxCallFrameSize, Size); 201 AdjustsStack = true; 202 } else if (MI.isInlineAsm()) { 203 // Some inline asm's need a stack frame, as indicated by operand 1. 204 unsigned ExtraInfo = MI.getOperand(InlineAsm::MIOp_ExtraInfo).getImm(); 205 if (ExtraInfo & InlineAsm::Extra_IsAlignStack) 206 AdjustsStack = true; 207 } 208 } 209 } 210 } 211 212 void MachineFrameInfo::print(const MachineFunction &MF, raw_ostream &OS) const{ 213 if (Objects.empty()) return; 214 215 const TargetFrameLowering *FI = MF.getSubtarget().getFrameLowering(); 216 int ValOffset = (FI ? FI->getOffsetOfLocalArea() : 0); 217 218 OS << "Frame Objects:\n"; 219 220 for (unsigned i = 0, e = Objects.size(); i != e; ++i) { 221 const StackObject &SO = Objects[i]; 222 OS << " fi#" << (int)(i-NumFixedObjects) << ": "; 223 224 if (SO.StackID != 0) 225 OS << "id=" << static_cast<unsigned>(SO.StackID) << ' '; 226 227 if (SO.Size == ~0ULL) { 228 OS << "dead\n"; 229 continue; 230 } 231 if (SO.Size == 0) 232 OS << "variable sized"; 233 else 234 OS << "size=" << SO.Size; 235 OS << ", align=" << SO.Alignment; 236 237 if (i < NumFixedObjects) 238 OS << ", fixed"; 239 if (i < NumFixedObjects || SO.SPOffset != -1) { 240 int64_t Off = SO.SPOffset - ValOffset; 241 OS << ", at location [SP"; 242 if (Off > 0) 243 OS << "+" << Off; 244 else if (Off < 0) 245 OS << Off; 246 OS << "]"; 247 } 248 OS << "\n"; 249 } 250 } 251 252 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 253 LLVM_DUMP_METHOD void MachineFrameInfo::dump(const MachineFunction &MF) const { 254 print(MF, dbgs()); 255 } 256 #endif 257