1 //===-- CallingConvLower.cpp - Calling Conventions ------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the CCState class, used for lowering and implementing
11 // calling conventions.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/CodeGen/CallingConvLower.h"
16 #include "llvm/CodeGen/MachineFrameInfo.h"
17 #include "llvm/CodeGen/MachineRegisterInfo.h"
18 #include "llvm/IR/DataLayout.h"
19 #include "llvm/Support/Debug.h"
20 #include "llvm/Support/ErrorHandling.h"
21 #include "llvm/Support/SaveAndRestore.h"
22 #include "llvm/Support/raw_ostream.h"
23 #include "llvm/Target/TargetLowering.h"
24 #include "llvm/Target/TargetRegisterInfo.h"
25 #include "llvm/Target/TargetSubtargetInfo.h"
26 using namespace llvm;
27 
28 CCState::CCState(CallingConv::ID CC, bool isVarArg, MachineFunction &mf,
29                  SmallVectorImpl<CCValAssign> &locs, LLVMContext &C)
30     : CallingConv(CC), IsVarArg(isVarArg), MF(mf),
31       TRI(*MF.getSubtarget().getRegisterInfo()), Locs(locs), Context(C),
32       CallOrPrologue(Unknown) {
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.
43 void CCState::HandleByVal(unsigned ValNo, MVT ValVT,
44                           MVT LocVT, CCValAssign::LocInfo LocInfo,
45                           int MinSize, int MinAlign,
46                           ISD::ArgFlagsTy ArgFlags) {
47   unsigned Align = ArgFlags.getByValAlign();
48   unsigned Size  = ArgFlags.getByValSize();
49   if (MinSize > (int)Size)
50     Size = MinSize;
51   if (MinAlign > (int)Align)
52     Align = MinAlign;
53   MF.getFrameInfo()->ensureMaxAlignment(Align);
54   MF.getSubtarget().getTargetLowering()->HandleByVal(this, Size, Align);
55   Size = unsigned(RoundUpToAlignment(Size, MinAlign));
56   unsigned Offset = AllocateStack(Size, Align);
57   addLoc(CCValAssign::getMem(ValNo, ValVT, Offset, LocVT, LocInfo));
58 }
59 
60 /// Mark a register and all of its aliases as allocated.
61 void CCState::MarkAllocated(unsigned Reg) {
62   for (MCRegAliasIterator AI(Reg, &TRI, true); AI.isValid(); ++AI)
63     UsedRegs[*AI/32] |= 1 << (*AI&31);
64 }
65 
66 /// Analyze an array of argument values,
67 /// incorporating info about the formals into this state.
68 void
69 CCState::AnalyzeFormalArguments(const SmallVectorImpl<ISD::InputArg> &Ins,
70                                 CCAssignFn Fn) {
71   unsigned NumArgs = Ins.size();
72 
73   for (unsigned i = 0; i != NumArgs; ++i) {
74     MVT ArgVT = Ins[i].VT;
75     ISD::ArgFlagsTy ArgFlags = Ins[i].Flags;
76     if (Fn(i, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, *this)) {
77 #ifndef NDEBUG
78       dbgs() << "Formal argument #" << i << " has unhandled type "
79              << EVT(ArgVT).getEVTString() << '\n';
80 #endif
81       llvm_unreachable(nullptr);
82     }
83   }
84 }
85 
86 /// Analyze the return values of a function, returning true if the return can
87 /// be performed without sret-demotion and false otherwise.
88 bool CCState::CheckReturn(const SmallVectorImpl<ISD::OutputArg> &Outs,
89                           CCAssignFn Fn) {
90   // Determine which register each value should be copied into.
91   for (unsigned i = 0, e = Outs.size(); i != e; ++i) {
92     MVT VT = Outs[i].VT;
93     ISD::ArgFlagsTy ArgFlags = Outs[i].Flags;
94     if (Fn(i, VT, VT, CCValAssign::Full, ArgFlags, *this))
95       return false;
96   }
97   return true;
98 }
99 
100 /// Analyze the returned values of a return,
101 /// incorporating info about the result values into this state.
102 void CCState::AnalyzeReturn(const SmallVectorImpl<ISD::OutputArg> &Outs,
103                             CCAssignFn Fn) {
104   // Determine which register each value should be copied into.
105   for (unsigned i = 0, e = Outs.size(); i != e; ++i) {
106     MVT VT = Outs[i].VT;
107     ISD::ArgFlagsTy ArgFlags = Outs[i].Flags;
108     if (Fn(i, VT, VT, CCValAssign::Full, ArgFlags, *this)) {
109 #ifndef NDEBUG
110       dbgs() << "Return operand #" << i << " has unhandled type "
111              << EVT(VT).getEVTString() << '\n';
112 #endif
113       llvm_unreachable(nullptr);
114     }
115   }
116 }
117 
118 /// Analyze the outgoing arguments to a call,
119 /// incorporating info about the passed values into this state.
120 void CCState::AnalyzeCallOperands(const SmallVectorImpl<ISD::OutputArg> &Outs,
121                                   CCAssignFn Fn) {
122   unsigned NumOps = Outs.size();
123   for (unsigned i = 0; i != NumOps; ++i) {
124     MVT ArgVT = Outs[i].VT;
125     ISD::ArgFlagsTy ArgFlags = Outs[i].Flags;
126     if (Fn(i, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, *this)) {
127 #ifndef NDEBUG
128       dbgs() << "Call operand #" << i << " has unhandled type "
129              << EVT(ArgVT).getEVTString() << '\n';
130 #endif
131       llvm_unreachable(nullptr);
132     }
133   }
134 }
135 
136 /// Same as above except it takes vectors of types and argument flags.
137 void CCState::AnalyzeCallOperands(SmallVectorImpl<MVT> &ArgVTs,
138                                   SmallVectorImpl<ISD::ArgFlagsTy> &Flags,
139                                   CCAssignFn Fn) {
140   unsigned NumOps = ArgVTs.size();
141   for (unsigned i = 0; i != NumOps; ++i) {
142     MVT ArgVT = ArgVTs[i];
143     ISD::ArgFlagsTy ArgFlags = Flags[i];
144     if (Fn(i, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, *this)) {
145 #ifndef NDEBUG
146       dbgs() << "Call operand #" << i << " has unhandled type "
147              << EVT(ArgVT).getEVTString() << '\n';
148 #endif
149       llvm_unreachable(nullptr);
150     }
151   }
152 }
153 
154 /// Analyze the return values of a call, incorporating info about the passed
155 /// values into this state.
156 void CCState::AnalyzeCallResult(const SmallVectorImpl<ISD::InputArg> &Ins,
157                                 CCAssignFn Fn) {
158   for (unsigned i = 0, e = Ins.size(); i != e; ++i) {
159     MVT VT = Ins[i].VT;
160     ISD::ArgFlagsTy Flags = Ins[i].Flags;
161     if (Fn(i, VT, VT, CCValAssign::Full, Flags, *this)) {
162 #ifndef NDEBUG
163       dbgs() << "Call result #" << i << " has unhandled type "
164              << EVT(VT).getEVTString() << '\n';
165 #endif
166       llvm_unreachable(nullptr);
167     }
168   }
169 }
170 
171 /// Same as above except it's specialized for calls that produce a single value.
172 void CCState::AnalyzeCallResult(MVT VT, CCAssignFn Fn) {
173   if (Fn(0, VT, VT, CCValAssign::Full, ISD::ArgFlagsTy(), *this)) {
174 #ifndef NDEBUG
175     dbgs() << "Call result has unhandled type "
176            << EVT(VT).getEVTString() << '\n';
177 #endif
178     llvm_unreachable(nullptr);
179   }
180 }
181 
182 static bool isValueTypeInRegForCC(CallingConv::ID CC, MVT VT) {
183   if (VT.isVector())
184     return true; // Assume -msse-regparm might be in effect.
185   if (!VT.isInteger())
186     return false;
187   if (CC == CallingConv::X86_VectorCall || CC == CallingConv::X86_FastCall)
188     return true;
189   return false;
190 }
191 
192 void CCState::getRemainingRegParmsForType(SmallVectorImpl<MCPhysReg> &Regs,
193                                           MVT VT, CCAssignFn Fn) {
194   unsigned SavedStackOffset = StackOffset;
195   unsigned NumLocs = Locs.size();
196 
197   // Set the 'inreg' flag if it is used for this calling convention.
198   ISD::ArgFlagsTy Flags;
199   if (isValueTypeInRegForCC(CallingConv, VT))
200     Flags.setInReg();
201 
202   // Allocate something of this value type repeatedly until we get assigned a
203   // location in memory.
204   bool HaveRegParm = true;
205   while (HaveRegParm) {
206     if (Fn(0, VT, VT, CCValAssign::Full, Flags, *this)) {
207 #ifndef NDEBUG
208       dbgs() << "Call has unhandled type " << EVT(VT).getEVTString()
209              << " while computing remaining regparms\n";
210 #endif
211       llvm_unreachable(nullptr);
212     }
213     HaveRegParm = Locs.back().isRegLoc();
214   }
215 
216   // Copy all the registers from the value locations we added.
217   assert(NumLocs < Locs.size() && "CC assignment failed to add location");
218   for (unsigned I = NumLocs, E = Locs.size(); I != E; ++I)
219     if (Locs[I].isRegLoc())
220       Regs.push_back(MCPhysReg(Locs[I].getLocReg()));
221 
222   // Clear the assigned values and stack memory. We leave the registers marked
223   // as allocated so that future queries don't return the same registers, i.e.
224   // when i64 and f64 are both passed in GPRs.
225   StackOffset = SavedStackOffset;
226   Locs.resize(NumLocs);
227 }
228 
229 void CCState::analyzeMustTailForwardedRegisters(
230     SmallVectorImpl<ForwardedRegister> &Forwards, ArrayRef<MVT> RegParmTypes,
231     CCAssignFn Fn) {
232   // Oftentimes calling conventions will not user register parameters for
233   // variadic functions, so we need to assume we're not variadic so that we get
234   // all the registers that might be used in a non-variadic call.
235   SaveAndRestore<bool> SavedVarArg(IsVarArg, false);
236 
237   for (MVT RegVT : RegParmTypes) {
238     SmallVector<MCPhysReg, 8> RemainingRegs;
239     getRemainingRegParmsForType(RemainingRegs, RegVT, Fn);
240     const TargetLowering *TL = MF.getSubtarget().getTargetLowering();
241     const TargetRegisterClass *RC = TL->getRegClassFor(RegVT);
242     for (MCPhysReg PReg : RemainingRegs) {
243       unsigned VReg = MF.addLiveIn(PReg, RC);
244       Forwards.push_back(ForwardedRegister(VReg, PReg, RegVT));
245     }
246   }
247 }
248