1 //===-- HexagonRegisterInfo.cpp - Hexagon Register Information ------------===//
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 contains the Hexagon implementation of the TargetRegisterInfo
10 // class.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "HexagonRegisterInfo.h"
15 #include "Hexagon.h"
16 #include "HexagonMachineFunctionInfo.h"
17 #include "HexagonSubtarget.h"
18 #include "HexagonTargetMachine.h"
19 #include "llvm/ADT/BitVector.h"
20 #include "llvm/ADT/SmallSet.h"
21 #include "llvm/ADT/STLExtras.h"
22 #include "llvm/CodeGen/LiveIntervals.h"
23 #include "llvm/CodeGen/LiveRegUnits.h"
24 #include "llvm/CodeGen/MachineFrameInfo.h"
25 #include "llvm/CodeGen/MachineFunction.h"
26 #include "llvm/CodeGen/MachineFunctionPass.h"
27 #include "llvm/CodeGen/MachineInstrBuilder.h"
28 #include "llvm/CodeGen/MachineRegisterInfo.h"
29 #include "llvm/CodeGen/PseudoSourceValue.h"
30 #include "llvm/CodeGen/RegisterScavenging.h"
31 #include "llvm/CodeGen/TargetInstrInfo.h"
32 #include "llvm/IR/Function.h"
33 #include "llvm/IR/Type.h"
34 #include "llvm/MC/MachineLocation.h"
35 #include "llvm/Support/CommandLine.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/ErrorHandling.h"
38 #include "llvm/Support/raw_ostream.h"
39 #include "llvm/Target/TargetMachine.h"
40 #include "llvm/Target/TargetOptions.h"
41 
42 #define GET_REGINFO_TARGET_DESC
43 #include "HexagonGenRegisterInfo.inc"
44 
45 using namespace llvm;
46 
47 static cl::opt<unsigned> FrameIndexSearchRange(
48     "hexagon-frame-index-search-range", cl::init(32), cl::Hidden,
49     cl::desc("Limit on instruction search range in frame index elimination"));
50 
51 static cl::opt<unsigned> FrameIndexReuseLimit(
52     "hexagon-frame-index-reuse-limit", cl::init(~0), cl::Hidden,
53     cl::desc("Limit on the number of reused registers in frame index "
54     "elimination"));
55 
56 HexagonRegisterInfo::HexagonRegisterInfo(unsigned HwMode)
57     : HexagonGenRegisterInfo(Hexagon::R31, 0/*DwarfFlavor*/, 0/*EHFlavor*/,
58                              0/*PC*/, HwMode) {}
59 
60 
61 bool HexagonRegisterInfo::isEHReturnCalleeSaveReg(Register R) const {
62   return R == Hexagon::R0 || R == Hexagon::R1 || R == Hexagon::R2 ||
63          R == Hexagon::R3 || R == Hexagon::D0 || R == Hexagon::D1;
64 }
65 
66 const MCPhysReg *
67 HexagonRegisterInfo::getCallerSavedRegs(const MachineFunction *MF,
68       const TargetRegisterClass *RC) const {
69   using namespace Hexagon;
70 
71   static const MCPhysReg Int32[] = {
72     R0, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, 0
73   };
74   static const MCPhysReg Int64[] = {
75     D0, D1, D2, D3, D4, D5, D6, D7, 0
76   };
77   static const MCPhysReg Pred[] = {
78     P0, P1, P2, P3, 0
79   };
80   static const MCPhysReg VecSgl[] = {
81      V0,  V1,  V2,  V3,  V4,  V5,  V6,  V7,  V8,  V9, V10, V11, V12, V13,
82     V14, V15, V16, V17, V18, V19, V20, V21, V22, V23, V24, V25, V26, V27,
83     V28, V29, V30, V31,   0
84   };
85   static const MCPhysReg VecDbl[] = {
86     W0, W1, W2, W3, W4, W5, W6, W7, W8, W9, W10, W11, W12, W13, W14, W15, 0
87   };
88   static const MCPhysReg VecPred[] = {
89     Q0, Q1, Q2, Q3, 0
90   };
91 
92   switch (RC->getID()) {
93     case IntRegsRegClassID:
94       return Int32;
95     case DoubleRegsRegClassID:
96       return Int64;
97     case PredRegsRegClassID:
98       return Pred;
99     case HvxVRRegClassID:
100       return VecSgl;
101     case HvxWRRegClassID:
102       return VecDbl;
103     case HvxQRRegClassID:
104       return VecPred;
105     default:
106       break;
107   }
108 
109   static const MCPhysReg Empty[] = { 0 };
110 #ifndef NDEBUG
111   dbgs() << "Register class: " << getRegClassName(RC) << "\n";
112 #endif
113   llvm_unreachable("Unexpected register class");
114   return Empty;
115 }
116 
117 
118 const MCPhysReg *
119 HexagonRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
120   static const MCPhysReg CalleeSavedRegsV3[] = {
121     Hexagon::R16,   Hexagon::R17,   Hexagon::R18,   Hexagon::R19,
122     Hexagon::R20,   Hexagon::R21,   Hexagon::R22,   Hexagon::R23,
123     Hexagon::R24,   Hexagon::R25,   Hexagon::R26,   Hexagon::R27, 0
124   };
125 
126   // Functions that contain a call to __builtin_eh_return also save the first 4
127   // parameter registers.
128   static const MCPhysReg CalleeSavedRegsV3EHReturn[] = {
129     Hexagon::R0,    Hexagon::R1,    Hexagon::R2,    Hexagon::R3,
130     Hexagon::R16,   Hexagon::R17,   Hexagon::R18,   Hexagon::R19,
131     Hexagon::R20,   Hexagon::R21,   Hexagon::R22,   Hexagon::R23,
132     Hexagon::R24,   Hexagon::R25,   Hexagon::R26,   Hexagon::R27, 0
133   };
134 
135   bool HasEHReturn = MF->getInfo<HexagonMachineFunctionInfo>()->hasEHReturn();
136 
137   return HasEHReturn ? CalleeSavedRegsV3EHReturn : CalleeSavedRegsV3;
138 }
139 
140 
141 const uint32_t *HexagonRegisterInfo::getCallPreservedMask(
142       const MachineFunction &MF, CallingConv::ID) const {
143   return HexagonCSR_RegMask;
144 }
145 
146 
147 BitVector HexagonRegisterInfo::getReservedRegs(const MachineFunction &MF)
148       const {
149   BitVector Reserved(getNumRegs());
150   Reserved.set(Hexagon::R29);
151   Reserved.set(Hexagon::R30);
152   Reserved.set(Hexagon::R31);
153   Reserved.set(Hexagon::VTMP);
154 
155   // Guest registers.
156   Reserved.set(Hexagon::GELR);        // G0
157   Reserved.set(Hexagon::GSR);         // G1
158   Reserved.set(Hexagon::GOSP);        // G2
159   Reserved.set(Hexagon::G3);          // G3
160 
161   // Control registers.
162   Reserved.set(Hexagon::SA0);         // C0
163   Reserved.set(Hexagon::LC0);         // C1
164   Reserved.set(Hexagon::SA1);         // C2
165   Reserved.set(Hexagon::LC1);         // C3
166   Reserved.set(Hexagon::P3_0);        // C4
167   Reserved.set(Hexagon::USR);         // C8
168   Reserved.set(Hexagon::PC);          // C9
169   Reserved.set(Hexagon::UGP);         // C10
170   Reserved.set(Hexagon::GP);          // C11
171   Reserved.set(Hexagon::CS0);         // C12
172   Reserved.set(Hexagon::CS1);         // C13
173   Reserved.set(Hexagon::UPCYCLELO);   // C14
174   Reserved.set(Hexagon::UPCYCLEHI);   // C15
175   Reserved.set(Hexagon::FRAMELIMIT);  // C16
176   Reserved.set(Hexagon::FRAMEKEY);    // C17
177   Reserved.set(Hexagon::PKTCOUNTLO);  // C18
178   Reserved.set(Hexagon::PKTCOUNTHI);  // C19
179   Reserved.set(Hexagon::UTIMERLO);    // C30
180   Reserved.set(Hexagon::UTIMERHI);    // C31
181   // Out of the control registers, only C8 is explicitly defined in
182   // HexagonRegisterInfo.td. If others are defined, make sure to add
183   // them here as well.
184   Reserved.set(Hexagon::C8);
185   Reserved.set(Hexagon::USR_OVF);
186 
187   // Leveraging these registers will require more work to recognize
188   // the new semantics posed, Hi/LoVec patterns, etc.
189   // Note well: if enabled, they should be restricted to only
190   // where `HST.useHVXOps() && HST.hasV67Ops()` is true.
191   for (auto Reg : Hexagon_MC::GetVectRegRev())
192     Reserved.set(Reg);
193 
194   if (MF.getSubtarget<HexagonSubtarget>().hasReservedR19())
195     Reserved.set(Hexagon::R19);
196 
197   Register AP =
198       MF.getInfo<HexagonMachineFunctionInfo>()->getStackAlignBaseReg();
199   if (AP.isValid())
200     Reserved.set(AP);
201 
202   for (int x = Reserved.find_first(); x >= 0; x = Reserved.find_next(x))
203     markSuperRegs(Reserved, x);
204 
205   return Reserved;
206 }
207 
208 bool HexagonRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
209                                               int SPAdj, unsigned FIOp,
210                                               RegScavenger *RS) const {
211   static unsigned ReuseCount = 0;
212   //
213   // Hexagon_TODO: Do we need to enforce this for Hexagon?
214   assert(SPAdj == 0 && "Unexpected");
215 
216   MachineInstr &MI = *II;
217   MachineBasicBlock &MB = *MI.getParent();
218   MachineFunction &MF = *MB.getParent();
219   auto &HST = MF.getSubtarget<HexagonSubtarget>();
220   auto &HII = *HST.getInstrInfo();
221   auto &HFI = *HST.getFrameLowering();
222 
223   Register BP;
224   int FI = MI.getOperand(FIOp).getIndex();
225   // Select the base pointer (BP) and calculate the actual offset from BP
226   // to the beginning of the object at index FI.
227   int Offset = HFI.getFrameIndexReference(MF, FI, BP).getFixed();
228   // Add the offset from the instruction.
229   int RealOffset = Offset + MI.getOperand(FIOp+1).getImm();
230 
231   unsigned Opc = MI.getOpcode();
232   switch (Opc) {
233     case Hexagon::PS_fia:
234       MI.setDesc(HII.get(Hexagon::A2_addi));
235       MI.getOperand(FIOp).ChangeToImmediate(RealOffset);
236       MI.removeOperand(FIOp+1);
237       return false;
238     case Hexagon::PS_fi:
239       // Set up the instruction for updating below.
240       MI.setDesc(HII.get(Hexagon::A2_addi));
241       break;
242   }
243 
244   if (!HII.isValidOffset(Opc, RealOffset, this)) {
245     // If the offset is not valid, calculate the address in a temporary
246     // register and use it with offset 0.
247     int InstOffset = 0;
248     // The actual base register (BP) is typically shared between many
249     // instructions where frame indices are being replaced. In scalar
250     // instructions the offset range is large, and the need for an extra
251     // add instruction is infrequent. Vector loads/stores, however, have
252     // a much smaller offset range: [-8, 7), or #s4. In those cases it
253     // makes sense to "standardize" the immediate in the "addi" instruction
254     // so that multiple loads/stores could be based on it.
255     bool IsPair = false;
256     switch (MI.getOpcode()) {
257       // All of these instructions have the same format: base+#s4.
258       case Hexagon::PS_vloadrw_ai:
259       case Hexagon::PS_vloadrw_nt_ai:
260       case Hexagon::PS_vstorerw_ai:
261       case Hexagon::PS_vstorerw_nt_ai:
262         IsPair = true;
263         [[fallthrough]];
264       case Hexagon::PS_vloadrv_ai:
265       case Hexagon::PS_vloadrv_nt_ai:
266       case Hexagon::PS_vstorerv_ai:
267       case Hexagon::PS_vstorerv_nt_ai:
268       case Hexagon::V6_vL32b_ai:
269       case Hexagon::V6_vS32b_ai: {
270         unsigned HwLen = HST.getVectorLength();
271         if (RealOffset % HwLen == 0) {
272           int VecOffset = RealOffset / HwLen;
273           // Rewrite the offset as "base + [-8, 7)".
274           VecOffset += 8;
275           // Pairs are expanded into two instructions: make sure that both
276           // can use the same base (i.e. VecOffset+1 is not a different
277           // multiple of 16 than VecOffset).
278           if (!IsPair || (VecOffset + 1) % 16 != 0) {
279             RealOffset = (VecOffset & -16) * HwLen;
280             InstOffset = (VecOffset % 16 - 8) * HwLen;
281           }
282         }
283       }
284     }
285 
286     // Search backwards in the block for "Reg = A2_addi BP, RealOffset".
287     // This will give us a chance to avoid creating a new register.
288     Register ReuseBP;
289 
290     if (ReuseCount < FrameIndexReuseLimit) {
291       unsigned SearchCount = 0, SearchRange = FrameIndexSearchRange;
292       SmallSet<Register,2> SeenVRegs;
293       bool PassedCall = false;
294       LiveRegUnits Defs(*this), Uses(*this);
295 
296       for (auto I = std::next(II.getReverse()), E = MB.rend(); I != E; ++I) {
297         if (SearchCount == SearchRange)
298           break;
299         ++SearchCount;
300         const MachineInstr &BI = *I;
301         LiveRegUnits::accumulateUsedDefed(BI, Defs, Uses, this);
302         PassedCall |= BI.isCall();
303         for (const MachineOperand &Op : BI.operands()) {
304           if (SeenVRegs.size() > 1)
305             break;
306           if (Op.isReg() && Op.getReg().isVirtual())
307             SeenVRegs.insert(Op.getReg());
308         }
309         if (BI.getOpcode() != Hexagon::A2_addi)
310           continue;
311         if (BI.getOperand(1).getReg() != BP)
312           continue;
313         const auto &Op2 = BI.getOperand(2);
314         if (!Op2.isImm() || Op2.getImm() != RealOffset)
315           continue;
316 
317         Register R = BI.getOperand(0).getReg();
318         if (R.isPhysical()) {
319           if (Defs.available(R))
320             ReuseBP = R;
321         } else if (R.isVirtual()) {
322           // Extending a range of a virtual register can be dangerous,
323           // since the scavenger will need to find a physical register
324           // for it. Avoid extending the range past a function call,
325           // and avoid overlapping it with another virtual register.
326           if (!PassedCall && SeenVRegs.size() <= 1)
327             ReuseBP = R;
328         }
329         break;
330       }
331       if (ReuseBP)
332         ++ReuseCount;
333     }
334 
335     auto &MRI = MF.getRegInfo();
336     if (!ReuseBP) {
337       ReuseBP = MRI.createVirtualRegister(&Hexagon::IntRegsRegClass);
338       const DebugLoc &DL = MI.getDebugLoc();
339       BuildMI(MB, II, DL, HII.get(Hexagon::A2_addi), ReuseBP)
340         .addReg(BP)
341         .addImm(RealOffset);
342     }
343     BP = ReuseBP;
344     RealOffset = InstOffset;
345   }
346 
347   MI.getOperand(FIOp).ChangeToRegister(BP, false, false, false);
348   MI.getOperand(FIOp+1).ChangeToImmediate(RealOffset);
349   return false;
350 }
351 
352 
353 bool HexagonRegisterInfo::shouldCoalesce(MachineInstr *MI,
354       const TargetRegisterClass *SrcRC, unsigned SubReg,
355       const TargetRegisterClass *DstRC, unsigned DstSubReg,
356       const TargetRegisterClass *NewRC, LiveIntervals &LIS) const {
357   // Coalescing will extend the live interval of the destination register.
358   // If the destination register is a vector pair, avoid introducing function
359   // calls into the interval, since it could result in a spilling of a pair
360   // instead of a single vector.
361   MachineFunction &MF = *MI->getParent()->getParent();
362   const HexagonSubtarget &HST = MF.getSubtarget<HexagonSubtarget>();
363   if (!HST.useHVXOps() || NewRC->getID() != Hexagon::HvxWRRegClass.getID())
364     return true;
365   bool SmallSrc = SrcRC->getID() == Hexagon::HvxVRRegClass.getID();
366   bool SmallDst = DstRC->getID() == Hexagon::HvxVRRegClass.getID();
367   if (!SmallSrc && !SmallDst)
368     return true;
369 
370   Register DstReg = MI->getOperand(0).getReg();
371   Register SrcReg = MI->getOperand(1).getReg();
372   const SlotIndexes &Indexes = *LIS.getSlotIndexes();
373   auto HasCall = [&Indexes] (const LiveInterval::Segment &S) {
374     for (SlotIndex I = S.start.getBaseIndex(), E = S.end.getBaseIndex();
375          I != E; I = I.getNextIndex()) {
376       if (const MachineInstr *MI = Indexes.getInstructionFromIndex(I))
377         if (MI->isCall())
378           return true;
379     }
380     return false;
381   };
382 
383   if (SmallSrc == SmallDst) {
384     // Both must be true, because the case for both being false was
385     // checked earlier. Both registers will be coalesced into a register
386     // of a wider class (HvxWR), and we don't want its live range to
387     // span over calls.
388     return !any_of(LIS.getInterval(DstReg), HasCall) &&
389            !any_of(LIS.getInterval(SrcReg), HasCall);
390   }
391 
392   // If one register is large (HvxWR) and the other is small (HvxVR), then
393   // coalescing is ok if the large is already live across a function call,
394   // or if the small one is not.
395   Register SmallReg = SmallSrc ? SrcReg : DstReg;
396   Register LargeReg = SmallSrc ? DstReg : SrcReg;
397   return  any_of(LIS.getInterval(LargeReg), HasCall) ||
398          !any_of(LIS.getInterval(SmallReg), HasCall);
399 }
400 
401 
402 Register HexagonRegisterInfo::getFrameRegister(const MachineFunction
403                                                &MF) const {
404   const HexagonFrameLowering *TFI = getFrameLowering(MF);
405   if (TFI->hasFP(MF))
406     return getFrameRegister();
407   return getStackRegister();
408 }
409 
410 
411 Register HexagonRegisterInfo::getFrameRegister() const {
412   return Hexagon::R30;
413 }
414 
415 
416 Register HexagonRegisterInfo::getStackRegister() const {
417   return Hexagon::R29;
418 }
419 
420 
421 unsigned HexagonRegisterInfo::getHexagonSubRegIndex(
422       const TargetRegisterClass &RC, unsigned GenIdx) const {
423   assert(GenIdx == Hexagon::ps_sub_lo || GenIdx == Hexagon::ps_sub_hi);
424 
425   static const unsigned ISub[] = { Hexagon::isub_lo, Hexagon::isub_hi };
426   static const unsigned VSub[] = { Hexagon::vsub_lo, Hexagon::vsub_hi };
427   static const unsigned WSub[] = { Hexagon::wsub_lo, Hexagon::wsub_hi };
428 
429   switch (RC.getID()) {
430     case Hexagon::CtrRegs64RegClassID:
431     case Hexagon::DoubleRegsRegClassID:
432       return ISub[GenIdx];
433     case Hexagon::HvxWRRegClassID:
434       return VSub[GenIdx];
435     case Hexagon::HvxVQRRegClassID:
436       return WSub[GenIdx];
437   }
438 
439   if (const TargetRegisterClass *SuperRC = *RC.getSuperClasses())
440     return getHexagonSubRegIndex(*SuperRC, GenIdx);
441 
442   llvm_unreachable("Invalid register class");
443 }
444 
445 bool HexagonRegisterInfo::useFPForScavengingIndex(const MachineFunction &MF)
446       const {
447   return MF.getSubtarget<HexagonSubtarget>().getFrameLowering()->hasFP(MF);
448 }
449 
450 const TargetRegisterClass *
451 HexagonRegisterInfo::getPointerRegClass(const MachineFunction &MF,
452                                         unsigned Kind) const {
453   return &Hexagon::IntRegsRegClass;
454 }
455