CallingConvLower.cpp revision 360784 
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
27using namespace llvm;
28
29CCState::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
36  clearByValRegsInfo();
37  UsedRegs.resize((TRI.getNumRegs()+31)/32);
38}
39
40/// Allocate space on the stack large enough to pass an argument by value.
41/// The size and alignment information of the argument is encoded in
42/// its parameter attribute.
43void CCState::HandleByVal(unsigned ValNo, MVT ValVT, MVT LocVT,
44                          CCValAssign::LocInfo LocInfo, int MinSize,
45                          int MinAlignment, ISD::ArgFlagsTy ArgFlags) {
46  Align MinAlign(MinAlignment);
47  Align Alignment(ArgFlags.getByValAlign());
48  unsigned Size  = ArgFlags.getByValSize();
49  if (MinSize > (int)Size)
50    Size = MinSize;
51  if (MinAlign > Alignment)
52    Alignment = MinAlign;
53  ensureMaxAlignment(Alignment);
54  MF.getSubtarget().getTargetLowering()->HandleByVal(this, Size,
55                                                     Alignment.value());
56  Size = unsigned(alignTo(Size, MinAlign));
57  unsigned Offset = AllocateStack(Size, Alignment.value());
58  addLoc(CCValAssign::getMem(ValNo, ValVT, Offset, LocVT, LocInfo));
59}
60
61/// Mark a register and all of its aliases as allocated.
62void CCState::MarkAllocated(unsigned Reg) {
63  for (MCRegAliasIterator AI(Reg, &TRI, true); AI.isValid(); ++AI)
64    UsedRegs[*AI/32] |= 1 << (*AI&31);
65}
66
67bool 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.
85void
86CCState::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      report_fatal_error("unable to allocate function argument #" + Twine(i));
95  }
96}
97
98/// Analyze the return values of a function, returning true if the return can
99/// be performed without sret-demotion and false otherwise.
100bool CCState::CheckReturn(const SmallVectorImpl<ISD::OutputArg> &Outs,
101                          CCAssignFn Fn) {
102  // Determine which register each value should be copied into.
103  for (unsigned i = 0, e = Outs.size(); i != e; ++i) {
104    MVT VT = Outs[i].VT;
105    ISD::ArgFlagsTy ArgFlags = Outs[i].Flags;
106    if (Fn(i, VT, VT, CCValAssign::Full, ArgFlags, *this))
107      return false;
108  }
109  return true;
110}
111
112/// Analyze the returned values of a return,
113/// incorporating info about the result values into this state.
114void CCState::AnalyzeReturn(const SmallVectorImpl<ISD::OutputArg> &Outs,
115                            CCAssignFn Fn) {
116  // Determine which register each value should be copied into.
117  for (unsigned i = 0, e = Outs.size(); i != e; ++i) {
118    MVT VT = Outs[i].VT;
119    ISD::ArgFlagsTy ArgFlags = Outs[i].Flags;
120    if (Fn(i, VT, VT, CCValAssign::Full, ArgFlags, *this))
121      report_fatal_error("unable to allocate function return #" + Twine(i));
122  }
123}
124
125/// Analyze the outgoing arguments to a call,
126/// incorporating info about the passed values into this state.
127void CCState::AnalyzeCallOperands(const SmallVectorImpl<ISD::OutputArg> &Outs,
128                                  CCAssignFn Fn) {
129  unsigned NumOps = Outs.size();
130  for (unsigned i = 0; i != NumOps; ++i) {
131    MVT ArgVT = Outs[i].VT;
132    ISD::ArgFlagsTy ArgFlags = Outs[i].Flags;
133    if (Fn(i, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, *this)) {
134#ifndef NDEBUG
135      dbgs() << "Call operand #" << i << " has unhandled type "
136             << EVT(ArgVT).getEVTString() << '\n';
137#endif
138      llvm_unreachable(nullptr);
139    }
140  }
141}
142
143/// Same as above except it takes vectors of types and argument flags.
144void CCState::AnalyzeCallOperands(SmallVectorImpl<MVT> &ArgVTs,
145                                  SmallVectorImpl<ISD::ArgFlagsTy> &Flags,
146                                  CCAssignFn Fn) {
147  unsigned NumOps = ArgVTs.size();
148  for (unsigned i = 0; i != NumOps; ++i) {
149    MVT ArgVT = ArgVTs[i];
150    ISD::ArgFlagsTy ArgFlags = Flags[i];
151    if (Fn(i, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, *this)) {
152#ifndef NDEBUG
153      dbgs() << "Call operand #" << i << " has unhandled type "
154             << EVT(ArgVT).getEVTString() << '\n';
155#endif
156      llvm_unreachable(nullptr);
157    }
158  }
159}
160
161/// Analyze the return values of a call, incorporating info about the passed
162/// values into this state.
163void CCState::AnalyzeCallResult(const SmallVectorImpl<ISD::InputArg> &Ins,
164                                CCAssignFn Fn) {
165  for (unsigned i = 0, e = Ins.size(); i != e; ++i) {
166    MVT VT = Ins[i].VT;
167    ISD::ArgFlagsTy Flags = Ins[i].Flags;
168    if (Fn(i, VT, VT, CCValAssign::Full, Flags, *this)) {
169#ifndef NDEBUG
170      dbgs() << "Call result #" << i << " has unhandled type "
171             << EVT(VT).getEVTString() << '\n';
172#endif
173      llvm_unreachable(nullptr);
174    }
175  }
176}
177
178/// Same as above except it's specialized for calls that produce a single value.
179void CCState::AnalyzeCallResult(MVT VT, CCAssignFn Fn) {
180  if (Fn(0, VT, VT, CCValAssign::Full, ISD::ArgFlagsTy(), *this)) {
181#ifndef NDEBUG
182    dbgs() << "Call result has unhandled type "
183           << EVT(VT).getEVTString() << '\n';
184#endif
185    llvm_unreachable(nullptr);
186  }
187}
188
189static bool isValueTypeInRegForCC(CallingConv::ID CC, MVT VT) {
190  if (VT.isVector())
191    return true; // Assume -msse-regparm might be in effect.
192  if (!VT.isInteger())
193    return false;
194  if (CC == CallingConv::X86_VectorCall || CC == CallingConv::X86_FastCall)
195    return true;
196  return false;
197}
198
199void CCState::getRemainingRegParmsForType(SmallVectorImpl<MCPhysReg> &Regs,
200                                          MVT VT, CCAssignFn Fn) {
201  unsigned SavedStackOffset = StackOffset;
202  Align SavedMaxStackArgAlign = MaxStackArgAlign;
203  unsigned NumLocs = Locs.size();
204
205  // Set the 'inreg' flag if it is used for this calling convention.
206  ISD::ArgFlagsTy Flags;
207  if (isValueTypeInRegForCC(CallingConv, VT))
208    Flags.setInReg();
209
210  // Allocate something of this value type repeatedly until we get assigned a
211  // location in memory.
212  bool HaveRegParm = true;
213  while (HaveRegParm) {
214    if (Fn(0, VT, VT, CCValAssign::Full, Flags, *this)) {
215#ifndef NDEBUG
216      dbgs() << "Call has unhandled type " << EVT(VT).getEVTString()
217             << " while computing remaining regparms\n";
218#endif
219      llvm_unreachable(nullptr);
220    }
221    HaveRegParm = Locs.back().isRegLoc();
222  }
223
224  // Copy all the registers from the value locations we added.
225  assert(NumLocs < Locs.size() && "CC assignment failed to add location");
226  for (unsigned I = NumLocs, E = Locs.size(); I != E; ++I)
227    if (Locs[I].isRegLoc())
228      Regs.push_back(MCPhysReg(Locs[I].getLocReg()));
229
230  // Clear the assigned values and stack memory. We leave the registers marked
231  // as allocated so that future queries don't return the same registers, i.e.
232  // when i64 and f64 are both passed in GPRs.
233  StackOffset = SavedStackOffset;
234  MaxStackArgAlign = SavedMaxStackArgAlign;
235  Locs.resize(NumLocs);
236}
237
238void CCState::analyzeMustTailForwardedRegisters(
239    SmallVectorImpl<ForwardedRegister> &Forwards, ArrayRef<MVT> RegParmTypes,
240    CCAssignFn Fn) {
241  // Oftentimes calling conventions will not user register parameters for
242  // variadic functions, so we need to assume we're not variadic so that we get
243  // all the registers that might be used in a non-variadic call.
244  SaveAndRestore<bool> SavedVarArg(IsVarArg, false);
245  SaveAndRestore<bool> SavedMustTail(AnalyzingMustTailForwardedRegs, true);
246
247  for (MVT RegVT : RegParmTypes) {
248    SmallVector<MCPhysReg, 8> RemainingRegs;
249    getRemainingRegParmsForType(RemainingRegs, RegVT, Fn);
250    const TargetLowering *TL = MF.getSubtarget().getTargetLowering();
251    const TargetRegisterClass *RC = TL->getRegClassFor(RegVT);
252    for (MCPhysReg PReg : RemainingRegs) {
253      unsigned VReg = MF.addLiveIn(PReg, RC);
254      Forwards.push_back(ForwardedRegister(VReg, PReg, RegVT));
255    }
256  }
257}
258
259bool CCState::resultsCompatible(CallingConv::ID CalleeCC,
260                                CallingConv::ID CallerCC, MachineFunction &MF,
261                                LLVMContext &C,
262                                const SmallVectorImpl<ISD::InputArg> &Ins,
263                                CCAssignFn CalleeFn, CCAssignFn CallerFn) {
264  if (CalleeCC == CallerCC)
265    return true;
266  SmallVector<CCValAssign, 4> RVLocs1;
267  CCState CCInfo1(CalleeCC, false, MF, RVLocs1, C);
268  CCInfo1.AnalyzeCallResult(Ins, CalleeFn);
269
270  SmallVector<CCValAssign, 4> RVLocs2;
271  CCState CCInfo2(CallerCC, false, MF, RVLocs2, C);
272  CCInfo2.AnalyzeCallResult(Ins, CallerFn);
273
274  if (RVLocs1.size() != RVLocs2.size())
275    return false;
276  for (unsigned I = 0, E = RVLocs1.size(); I != E; ++I) {
277    const CCValAssign &Loc1 = RVLocs1[I];
278    const CCValAssign &Loc2 = RVLocs2[I];
279    if (Loc1.getLocInfo() != Loc2.getLocInfo())
280      return false;
281    bool RegLoc1 = Loc1.isRegLoc();
282    if (RegLoc1 != Loc2.isRegLoc())
283      return false;
284    if (RegLoc1) {
285      if (Loc1.getLocReg() != Loc2.getLocReg())
286        return false;
287    } else {
288      if (Loc1.getLocMemOffset() != Loc2.getLocMemOffset())
289        return false;
290    }
291  }
292  return true;
293}
294