lib/CodeGen/CallingConvLower.cpp

   1 //===-- CallingConvLower.cpp - Calling Conventions ------------------------===//
   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 file implements the CCState class, used for lowering and implementing
  10 // calling conventions.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/CodeGen/CallingConvLower.h"
  15 #include "llvm/CodeGen/MachineFrameInfo.h"
  16 #include "llvm/CodeGen/MachineRegisterInfo.h"
  17 #include "llvm/CodeGen/TargetLowering.h"
  18 #include "llvm/CodeGen/TargetRegisterInfo.h"
  19 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  20 #include "llvm/IR/DataLayout.h"
  21 #include "llvm/Support/Debug.h"
  22 #include "llvm/Support/ErrorHandling.h"
  23 #include "llvm/Support/SaveAndRestore.h"
  24 #include "llvm/Support/raw_ostream.h"
  25 #include <algorithm>
  26
  27 using namespace llvm;
  28
  29 CCState::CCState(CallingConv::ID CC, bool isVarArg, MachineFunction &mf,
  30                  SmallVectorImpl<CCValAssign> &locs, LLVMContext &C)
  31     : CallingConv(CC), IsVarArg(isVarArg), MF(mf),
  32       TRI(*MF.getSubtarget().getRegisterInfo()), Locs(locs), Context(C) {
  33   // No stack is used.
  34   StackOffset = 0;
  35   MaxStackArgAlign = 1;
  36
  37   clearByValRegsInfo();
  38   UsedRegs.resize((TRI.getNumRegs()+31)/32);
  39 }
  40
  41 /// Allocate space on the stack large enough to pass an argument by value.
  42 /// The size and alignment information of the argument is encoded in
  43 /// its parameter attribute.
  44 void CCState::HandleByVal(unsigned ValNo, MVT ValVT,
  45                           MVT LocVT, CCValAssign::LocInfo LocInfo,
  46                           int MinSize, int MinAlign,
  47                           ISD::ArgFlagsTy ArgFlags) {
  48   unsigned Align = ArgFlags.getByValAlign();
  49   unsigned Size  = ArgFlags.getByValSize();
  50   if (MinSize > (int)Size)
  51     Size = MinSize;
  52   if (MinAlign > (int)Align)
  53     Align = MinAlign;
  54   ensureMaxAlignment(Align);
  55   MF.getSubtarget().getTargetLowering()->HandleByVal(this, Size, Align);
  56   Size = unsigned(alignTo(Size, MinAlign));
  57   unsigned Offset = AllocateStack(Size, Align);
  58   addLoc(CCValAssign::getMem(ValNo, ValVT, Offset, LocVT, LocInfo));
  59 }
  60
  61 /// Mark a register and all of its aliases as allocated.
  62 void CCState::MarkAllocated(unsigned Reg) {
  63   for (MCRegAliasIterator AI(Reg, &TRI, true); AI.isValid(); ++AI)
  64     UsedRegs[*AI/32] |= 1 << (*AI&31);
  65 }
  66
  67 bool CCState::IsShadowAllocatedReg(unsigned Reg) const {
  68   if (!isAllocated(Reg))
  69     return false;
  70
  71   for (auto const &ValAssign : Locs) {
  72     if (ValAssign.isRegLoc()) {
  73       for (MCRegAliasIterator AI(ValAssign.getLocReg(), &TRI, true);
  74            AI.isValid(); ++AI) {
  75         if (*AI == Reg)
  76           return false;
  77       }
  78     }
  79   }
  80   return true;
  81 }
  82
  83 /// Analyze an array of argument values,
  84 /// incorporating info about the formals into this state.
  85 void
  86 CCState::AnalyzeFormalArguments(const SmallVectorImpl<ISD::InputArg> &Ins,
  87                                 CCAssignFn Fn) {
  88   unsigned NumArgs = Ins.size();
  89
  90   for (unsigned i = 0; i != NumArgs; ++i) {
  91     MVT ArgVT = Ins[i].VT;
  92     ISD::ArgFlagsTy ArgFlags = Ins[i].Flags;
  93     if (Fn(i, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, *this)) {
  94 #ifndef NDEBUG
  95       dbgs() << "Formal argument #" << i << " has unhandled type "
  96              << EVT(ArgVT).getEVTString() << '\n';
  97 #endif
  98       llvm_unreachable(nullptr);
  99     }
 100   }
 101 }
 102
 103 /// Analyze the return values of a function, returning true if the return can
 104 /// be performed without sret-demotion and false otherwise.
 105 bool CCState::CheckReturn(const SmallVectorImpl<ISD::OutputArg> &Outs,
 106                           CCAssignFn Fn) {
 107   // Determine which register each value should be copied into.
 108   for (unsigned i = 0, e = Outs.size(); i != e; ++i) {
 109     MVT VT = Outs[i].VT;
 110     ISD::ArgFlagsTy ArgFlags = Outs[i].Flags;
 111     if (Fn(i, VT, VT, CCValAssign::Full, ArgFlags, *this))
 112       return false;
 113   }
 114   return true;
 115 }
 116
 117 /// Analyze the returned values of a return,
 118 /// incorporating info about the result values into this state.
 119 void CCState::AnalyzeReturn(const SmallVectorImpl<ISD::OutputArg> &Outs,
 120                             CCAssignFn Fn) {
 121   // Determine which register each value should be copied into.
 122   for (unsigned i = 0, e = Outs.size(); i != e; ++i) {
 123     MVT VT = Outs[i].VT;
 124     ISD::ArgFlagsTy ArgFlags = Outs[i].Flags;
 125     if (Fn(i, VT, VT, CCValAssign::Full, ArgFlags, *this)) {
 126 #ifndef NDEBUG
 127       dbgs() << "Return operand #" << i << " has unhandled type "
 128              << EVT(VT).getEVTString() << '\n';
 129 #endif
 130       llvm_unreachable(nullptr);
 131     }
 132   }
 133 }
 134
 135 /// Analyze the outgoing arguments to a call,
 136 /// incorporating info about the passed values into this state.
 137 void CCState::AnalyzeCallOperands(const SmallVectorImpl<ISD::OutputArg> &Outs,
 138                                   CCAssignFn Fn) {
 139   unsigned NumOps = Outs.size();
 140   for (unsigned i = 0; i != NumOps; ++i) {
 141     MVT ArgVT = Outs[i].VT;
 142     ISD::ArgFlagsTy ArgFlags = Outs[i].Flags;
 143     if (Fn(i, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, *this)) {
 144 #ifndef NDEBUG
 145       dbgs() << "Call operand #" << i << " has unhandled type "
 146              << EVT(ArgVT).getEVTString() << '\n';
 147 #endif
 148       llvm_unreachable(nullptr);
 149     }
 150   }
 151 }
 152
 153 /// Same as above except it takes vectors of types and argument flags.
 154 void CCState::AnalyzeCallOperands(SmallVectorImpl<MVT> &ArgVTs,
 155                                   SmallVectorImpl<ISD::ArgFlagsTy> &Flags,
 156                                   CCAssignFn Fn) {
 157   unsigned NumOps = ArgVTs.size();
 158   for (unsigned i = 0; i != NumOps; ++i) {
 159     MVT ArgVT = ArgVTs[i];
 160     ISD::ArgFlagsTy ArgFlags = Flags[i];
 161     if (Fn(i, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, *this)) {
 162 #ifndef NDEBUG
 163       dbgs() << "Call operand #" << i << " has unhandled type "
 164              << EVT(ArgVT).getEVTString() << '\n';
 165 #endif
 166       llvm_unreachable(nullptr);
 167     }
 168   }
 169 }
 170
 171 /// Analyze the return values of a call, incorporating info about the passed
 172 /// values into this state.
 173 void CCState::AnalyzeCallResult(const SmallVectorImpl<ISD::InputArg> &Ins,
 174                                 CCAssignFn Fn) {
 175   for (unsigned i = 0, e = Ins.size(); i != e; ++i) {
 176     MVT VT = Ins[i].VT;
 177     ISD::ArgFlagsTy Flags = Ins[i].Flags;
 178     if (Fn(i, VT, VT, CCValAssign::Full, Flags, *this)) {
 179 #ifndef NDEBUG
 180       dbgs() << "Call result #" << i << " has unhandled type "
 181              << EVT(VT).getEVTString() << '\n';
 182 #endif
 183       llvm_unreachable(nullptr);
 184     }
 185   }
 186 }
 187
 188 /// Same as above except it's specialized for calls that produce a single value.
 189 void CCState::AnalyzeCallResult(MVT VT, CCAssignFn Fn) {
 190   if (Fn(0, VT, VT, CCValAssign::Full, ISD::ArgFlagsTy(), *this)) {
 191 #ifndef NDEBUG
 192     dbgs() << "Call result has unhandled type "
 193            << EVT(VT).getEVTString() << '\n';
 194 #endif
 195     llvm_unreachable(nullptr);
 196   }
 197 }
 198
 199 static bool isValueTypeInRegForCC(CallingConv::ID CC, MVT VT) {
 200   if (VT.isVector())
 201     return true; // Assume -msse-regparm might be in effect.
 202   if (!VT.isInteger())
 203     return false;
 204   if (CC == CallingConv::X86_VectorCall || CC == CallingConv::X86_FastCall)
 205     return true;
 206   return false;
 207 }
 208
 209 void CCState::getRemainingRegParmsForType(SmallVectorImpl<MCPhysReg> &Regs,
 210                                           MVT VT, CCAssignFn Fn) {
 211   unsigned SavedStackOffset = StackOffset;
 212   unsigned SavedMaxStackArgAlign = MaxStackArgAlign;
 213   unsigned NumLocs = Locs.size();
 214
 215   // Set the 'inreg' flag if it is used for this calling convention.
 216   ISD::ArgFlagsTy Flags;
 217   if (isValueTypeInRegForCC(CallingConv, VT))
 218     Flags.setInReg();
 219
 220   // Allocate something of this value type repeatedly until we get assigned a
 221   // location in memory.
 222   bool HaveRegParm = true;
 223   while (HaveRegParm) {
 224     if (Fn(0, VT, VT, CCValAssign::Full, Flags, *this)) {
 225 #ifndef NDEBUG
 226       dbgs() << "Call has unhandled type " << EVT(VT).getEVTString()
 227              << " while computing remaining regparms\n";
 228 #endif
 229       llvm_unreachable(nullptr);
 230     }
 231     HaveRegParm = Locs.back().isRegLoc();
 232   }
 233
 234   // Copy all the registers from the value locations we added.
 235   assert(NumLocs < Locs.size() && "CC assignment failed to add location");
 236   for (unsigned I = NumLocs, E = Locs.size(); I != E; ++I)
 237     if (Locs[I].isRegLoc())
 238       Regs.push_back(MCPhysReg(Locs[I].getLocReg()));
 239
 240   // Clear the assigned values and stack memory. We leave the registers marked
 241   // as allocated so that future queries don't return the same registers, i.e.
 242   // when i64 and f64 are both passed in GPRs.
 243   StackOffset = SavedStackOffset;
 244   MaxStackArgAlign = SavedMaxStackArgAlign;
 245   Locs.resize(NumLocs);
 246 }
 247
 248 void CCState::analyzeMustTailForwardedRegisters(
 249     SmallVectorImpl<ForwardedRegister> &Forwards, ArrayRef<MVT> RegParmTypes,
 250     CCAssignFn Fn) {
 251   // Oftentimes calling conventions will not user register parameters for
 252   // variadic functions, so we need to assume we're not variadic so that we get
 253   // all the registers that might be used in a non-variadic call.
 254   SaveAndRestore<bool> SavedVarArg(IsVarArg, false);
 255   SaveAndRestore<bool> SavedMustTail(AnalyzingMustTailForwardedRegs, true);
 256
 257   for (MVT RegVT : RegParmTypes) {
 258     SmallVector<MCPhysReg, 8> RemainingRegs;
 259     getRemainingRegParmsForType(RemainingRegs, RegVT, Fn);
 260     const TargetLowering *TL = MF.getSubtarget().getTargetLowering();
 261     const TargetRegisterClass *RC = TL->getRegClassFor(RegVT);
 262     for (MCPhysReg PReg : RemainingRegs) {
 263       unsigned VReg = MF.addLiveIn(PReg, RC);
 264       Forwards.push_back(ForwardedRegister(VReg, PReg, RegVT));
 265     }
 266   }
 267 }
 268
 269 bool CCState::resultsCompatible(CallingConv::ID CalleeCC,
 270                                 CallingConv::ID CallerCC, MachineFunction &MF,
 271                                 LLVMContext &C,
 272                                 const SmallVectorImpl<ISD::InputArg> &Ins,
 273                                 CCAssignFn CalleeFn, CCAssignFn CallerFn) {
 274   if (CalleeCC == CallerCC)
 275     return true;
 276   SmallVector<CCValAssign, 4> RVLocs1;
 277   CCState CCInfo1(CalleeCC, false, MF, RVLocs1, C);
 278   CCInfo1.AnalyzeCallResult(Ins, CalleeFn);
 279
 280   SmallVector<CCValAssign, 4> RVLocs2;
 281   CCState CCInfo2(CallerCC, false, MF, RVLocs2, C);
 282   CCInfo2.AnalyzeCallResult(Ins, CallerFn);
 283
 284   if (RVLocs1.size() != RVLocs2.size())
 285     return false;
 286   for (unsigned I = 0, E = RVLocs1.size(); I != E; ++I) {
 287     const CCValAssign &Loc1 = RVLocs1[I];
 288     const CCValAssign &Loc2 = RVLocs2[I];
 289     if (Loc1.getLocInfo() != Loc2.getLocInfo())
 290       return false;
 291     bool RegLoc1 = Loc1.isRegLoc();
 292     if (RegLoc1 != Loc2.isRegLoc())
 293       return false;
 294     if (RegLoc1) {
 295       if (Loc1.getLocReg() != Loc2.getLocReg())
 296         return false;
 297     } else {
 298       if (Loc1.getLocMemOffset() != Loc2.getLocMemOffset())
 299         return false;
 300     }
 301   }
 302   return true;
 303 }