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(llvm::Align 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 llvm::Align clampStackAlignment(bool ShouldClamp, 40 llvm::Align Align, 41 llvm::Align StackAlign) { 42 if (!ShouldClamp || Align <= StackAlign) 43 return Align; 44 LLVM_DEBUG(dbgs() << "Warning: requested alignment " << Align.value() 45 << " exceeds the stack alignment " << StackAlign.value() 46 << " when stack realignment is off" << '\n'); 47 return StackAlign; 48 } 49 50 int MachineFrameInfo::CreateStackObject(uint64_t Size, llvm::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, 66 llvm::Align Alignment) { 67 Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment); 68 CreateStackObject(Size, Alignment, true); 69 int Index = (int)Objects.size() - NumFixedObjects - 1; 70 ensureMaxAlignment(Alignment); 71 return Index; 72 } 73 74 int MachineFrameInfo::CreateVariableSizedObject(llvm::Align Alignment, 75 const AllocaInst *Alloca) { 76 HasVarSizedObjects = true; 77 Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment); 78 Objects.push_back(StackObject(0, Alignment, 0, false, false, Alloca, true)); 79 ensureMaxAlignment(Alignment); 80 return (int)Objects.size()-NumFixedObjects-1; 81 } 82 83 int MachineFrameInfo::CreateFixedObject(uint64_t Size, int64_t SPOffset, 84 bool IsImmutable, bool IsAliased) { 85 assert(Size != 0 && "Cannot allocate zero size fixed stack objects!"); 86 // The alignment of the frame index can be determined from its offset from 87 // the incoming frame position. If the frame object is at offset 32 and 88 // the stack is guaranteed to be 16-byte aligned, then we know that the 89 // object is 16-byte aligned. Note that unlike the non-fixed case, if the 90 // stack needs realignment, we can't assume that the stack will in fact be 91 // aligned. 92 llvm::Align Alignment = 93 commonAlignment(ForcedRealign ? llvm::Align() : StackAlignment, SPOffset); 94 Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment); 95 Objects.insert(Objects.begin(), 96 StackObject(Size, Alignment, SPOffset, IsImmutable, 97 /*IsSpillSlot=*/false, /*Alloca=*/nullptr, 98 IsAliased)); 99 return -++NumFixedObjects; 100 } 101 102 int MachineFrameInfo::CreateFixedSpillStackObject(uint64_t Size, 103 int64_t SPOffset, 104 bool IsImmutable) { 105 llvm::Align Alignment = 106 commonAlignment(ForcedRealign ? llvm::Align() : StackAlignment, SPOffset); 107 Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment); 108 Objects.insert(Objects.begin(), 109 StackObject(Size, Alignment, SPOffset, IsImmutable, 110 /*IsSpillSlot=*/true, /*Alloca=*/nullptr, 111 /*IsAliased=*/false)); 112 return -++NumFixedObjects; 113 } 114 115 BitVector MachineFrameInfo::getPristineRegs(const MachineFunction &MF) const { 116 const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo(); 117 BitVector BV(TRI->getNumRegs()); 118 119 // Before CSI is calculated, no registers are considered pristine. They can be 120 // freely used and PEI will make sure they are saved. 121 if (!isCalleeSavedInfoValid()) 122 return BV; 123 124 const MachineRegisterInfo &MRI = MF.getRegInfo(); 125 for (const MCPhysReg *CSR = MRI.getCalleeSavedRegs(); CSR && *CSR; 126 ++CSR) 127 BV.set(*CSR); 128 129 // Saved CSRs are not pristine. 130 for (auto &I : getCalleeSavedInfo()) 131 for (MCSubRegIterator S(I.getReg(), TRI, true); S.isValid(); ++S) 132 BV.reset(*S); 133 134 return BV; 135 } 136 137 unsigned MachineFrameInfo::estimateStackSize(const MachineFunction &MF) const { 138 const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering(); 139 const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo(); 140 unsigned MaxAlign = getMaxAlignment(); 141 int Offset = 0; 142 143 // This code is very, very similar to PEI::calculateFrameObjectOffsets(). 144 // It really should be refactored to share code. Until then, changes 145 // should keep in mind that there's tight coupling between the two. 146 147 for (int i = getObjectIndexBegin(); i != 0; ++i) { 148 // Only estimate stack size of default stack. 149 if (getStackID(i) != TargetStackID::Default) 150 continue; 151 int FixedOff = -getObjectOffset(i); 152 if (FixedOff > Offset) Offset = FixedOff; 153 } 154 for (unsigned i = 0, e = getObjectIndexEnd(); i != e; ++i) { 155 // Only estimate stack size of live objects on default stack. 156 if (isDeadObjectIndex(i) || getStackID(i) != TargetStackID::Default) 157 continue; 158 Offset += getObjectSize(i); 159 unsigned Align = getObjectAlignment(i); 160 // Adjust to alignment boundary 161 Offset = (Offset+Align-1)/Align*Align; 162 163 MaxAlign = std::max(Align, MaxAlign); 164 } 165 166 if (adjustsStack() && TFI->hasReservedCallFrame(MF)) 167 Offset += getMaxCallFrameSize(); 168 169 // Round up the size to a multiple of the alignment. If the function has 170 // any calls or alloca's, align to the target's StackAlignment value to 171 // ensure that the callee's frame or the alloca data is suitably aligned; 172 // otherwise, for leaf functions, align to the TransientStackAlignment 173 // value. 174 unsigned StackAlign; 175 if (adjustsStack() || hasVarSizedObjects() || 176 (RegInfo->needsStackRealignment(MF) && getObjectIndexEnd() != 0)) 177 StackAlign = TFI->getStackAlignment(); 178 else 179 StackAlign = TFI->getTransientStackAlignment(); 180 181 // If the frame pointer is eliminated, all frame offsets will be relative to 182 // SP not FP. Align to MaxAlign so this works. 183 StackAlign = std::max(StackAlign, MaxAlign); 184 unsigned AlignMask = StackAlign - 1; 185 Offset = (Offset + AlignMask) & ~uint64_t(AlignMask); 186 187 return (unsigned)Offset; 188 } 189 190 void MachineFrameInfo::computeMaxCallFrameSize(const MachineFunction &MF) { 191 const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); 192 unsigned FrameSetupOpcode = TII.getCallFrameSetupOpcode(); 193 unsigned FrameDestroyOpcode = TII.getCallFrameDestroyOpcode(); 194 assert(FrameSetupOpcode != ~0u && FrameDestroyOpcode != ~0u && 195 "Can only compute MaxCallFrameSize if Setup/Destroy opcode are known"); 196 197 MaxCallFrameSize = 0; 198 for (const MachineBasicBlock &MBB : MF) { 199 for (const MachineInstr &MI : MBB) { 200 unsigned Opcode = MI.getOpcode(); 201 if (Opcode == FrameSetupOpcode || Opcode == FrameDestroyOpcode) { 202 unsigned Size = TII.getFrameSize(MI); 203 MaxCallFrameSize = std::max(MaxCallFrameSize, Size); 204 AdjustsStack = true; 205 } else if (MI.isInlineAsm()) { 206 // Some inline asm's need a stack frame, as indicated by operand 1. 207 unsigned ExtraInfo = MI.getOperand(InlineAsm::MIOp_ExtraInfo).getImm(); 208 if (ExtraInfo & InlineAsm::Extra_IsAlignStack) 209 AdjustsStack = true; 210 } 211 } 212 } 213 } 214 215 void MachineFrameInfo::print(const MachineFunction &MF, raw_ostream &OS) const{ 216 if (Objects.empty()) return; 217 218 const TargetFrameLowering *FI = MF.getSubtarget().getFrameLowering(); 219 int ValOffset = (FI ? FI->getOffsetOfLocalArea() : 0); 220 221 OS << "Frame Objects:\n"; 222 223 for (unsigned i = 0, e = Objects.size(); i != e; ++i) { 224 const StackObject &SO = Objects[i]; 225 OS << " fi#" << (int)(i-NumFixedObjects) << ": "; 226 227 if (SO.StackID != 0) 228 OS << "id=" << static_cast<unsigned>(SO.StackID) << ' '; 229 230 if (SO.Size == ~0ULL) { 231 OS << "dead\n"; 232 continue; 233 } 234 if (SO.Size == 0) 235 OS << "variable sized"; 236 else 237 OS << "size=" << SO.Size; 238 OS << ", align=" << SO.Alignment.value(); 239 240 if (i < NumFixedObjects) 241 OS << ", fixed"; 242 if (i < NumFixedObjects || SO.SPOffset != -1) { 243 int64_t Off = SO.SPOffset - ValOffset; 244 OS << ", at location [SP"; 245 if (Off > 0) 246 OS << "+" << Off; 247 else if (Off < 0) 248 OS << Off; 249 OS << "]"; 250 } 251 OS << "\n"; 252 } 253 } 254 255 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 256 LLVM_DUMP_METHOD void MachineFrameInfo::dump(const MachineFunction &MF) const { 257 print(MF, dbgs()); 258 } 259 #endif 260