1 //===- Thumb2InstrInfo.cpp - Thumb-2 Instruction 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 Thumb-2 implementation of the TargetInstrInfo class.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "Thumb2InstrInfo.h"
14 #include "ARMMachineFunctionInfo.h"
15 #include "ARMSubtarget.h"
16 #include "MCTargetDesc/ARMAddressingModes.h"
17 #include "llvm/CodeGen/MachineBasicBlock.h"
18 #include "llvm/CodeGen/MachineFrameInfo.h"
19 #include "llvm/CodeGen/MachineFunction.h"
20 #include "llvm/CodeGen/MachineInstr.h"
21 #include "llvm/CodeGen/MachineInstrBuilder.h"
22 #include "llvm/CodeGen/MachineMemOperand.h"
23 #include "llvm/CodeGen/MachineOperand.h"
24 #include "llvm/CodeGen/MachineRegisterInfo.h"
25 #include "llvm/CodeGen/TargetRegisterInfo.h"
26 #include "llvm/IR/DebugLoc.h"
27 #include "llvm/MC/MCInst.h"
28 #include "llvm/MC/MCInstBuilder.h"
29 #include "llvm/MC/MCInstrDesc.h"
30 #include "llvm/Support/CommandLine.h"
31 #include "llvm/Support/ErrorHandling.h"
32 #include "llvm/Support/MathExtras.h"
33 #include "llvm/Target/TargetMachine.h"
34 #include <cassert>
35 
36 using namespace llvm;
37 
38 static cl::opt<bool>
39 OldT2IfCvt("old-thumb2-ifcvt", cl::Hidden,
40            cl::desc("Use old-style Thumb2 if-conversion heuristics"),
41            cl::init(false));
42 
43 static cl::opt<bool>
44 PreferNoCSEL("prefer-no-csel", cl::Hidden,
45              cl::desc("Prefer predicated Move to CSEL"),
46              cl::init(false));
47 
48 Thumb2InstrInfo::Thumb2InstrInfo(const ARMSubtarget &STI)
49     : ARMBaseInstrInfo(STI) {}
50 
51 /// Return the noop instruction to use for a noop.
52 MCInst Thumb2InstrInfo::getNop() const {
53   return MCInstBuilder(ARM::tHINT).addImm(0).addImm(ARMCC::AL).addReg(0);
54 }
55 
56 unsigned Thumb2InstrInfo::getUnindexedOpcode(unsigned Opc) const {
57   // FIXME
58   return 0;
59 }
60 
61 void
62 Thumb2InstrInfo::ReplaceTailWithBranchTo(MachineBasicBlock::iterator Tail,
63                                          MachineBasicBlock *NewDest) const {
64   MachineBasicBlock *MBB = Tail->getParent();
65   ARMFunctionInfo *AFI = MBB->getParent()->getInfo<ARMFunctionInfo>();
66   if (!AFI->hasITBlocks() || Tail->isBranch()) {
67     TargetInstrInfo::ReplaceTailWithBranchTo(Tail, NewDest);
68     return;
69   }
70 
71   // If the first instruction of Tail is predicated, we may have to update
72   // the IT instruction.
73   Register PredReg;
74   ARMCC::CondCodes CC = getInstrPredicate(*Tail, PredReg);
75   MachineBasicBlock::iterator MBBI = Tail;
76   if (CC != ARMCC::AL)
77     // Expecting at least the t2IT instruction before it.
78     --MBBI;
79 
80   // Actually replace the tail.
81   TargetInstrInfo::ReplaceTailWithBranchTo(Tail, NewDest);
82 
83   // Fix up IT.
84   if (CC != ARMCC::AL) {
85     MachineBasicBlock::iterator E = MBB->begin();
86     unsigned Count = 4; // At most 4 instructions in an IT block.
87     while (Count && MBBI != E) {
88       if (MBBI->isDebugInstr()) {
89         --MBBI;
90         continue;
91       }
92       if (MBBI->getOpcode() == ARM::t2IT) {
93         unsigned Mask = MBBI->getOperand(1).getImm();
94         if (Count == 4)
95           MBBI->eraseFromParent();
96         else {
97           unsigned MaskOn = 1 << Count;
98           unsigned MaskOff = ~(MaskOn - 1);
99           MBBI->getOperand(1).setImm((Mask & MaskOff) | MaskOn);
100         }
101         return;
102       }
103       --MBBI;
104       --Count;
105     }
106 
107     // Ctrl flow can reach here if branch folding is run before IT block
108     // formation pass.
109   }
110 }
111 
112 bool
113 Thumb2InstrInfo::isLegalToSplitMBBAt(MachineBasicBlock &MBB,
114                                      MachineBasicBlock::iterator MBBI) const {
115   while (MBBI->isDebugInstr()) {
116     ++MBBI;
117     if (MBBI == MBB.end())
118       return false;
119   }
120 
121   Register PredReg;
122   return getITInstrPredicate(*MBBI, PredReg) == ARMCC::AL;
123 }
124 
125 MachineInstr *
126 Thumb2InstrInfo::optimizeSelect(MachineInstr &MI,
127                                 SmallPtrSetImpl<MachineInstr *> &SeenMIs,
128                                 bool PreferFalse) const {
129   // Try to use the base optimizeSelect, which uses canFoldIntoMOVCC to fold the
130   // MOVCC into another instruction. If that fails on 8.1-M fall back to using a
131   // CSEL.
132   MachineInstr *RV = ARMBaseInstrInfo::optimizeSelect(MI, SeenMIs, PreferFalse);
133   if (!RV && getSubtarget().hasV8_1MMainlineOps() && !PreferNoCSEL) {
134     Register DestReg = MI.getOperand(0).getReg();
135 
136     if (!DestReg.isVirtual())
137       return nullptr;
138 
139     MachineInstrBuilder NewMI = BuildMI(*MI.getParent(), MI, MI.getDebugLoc(),
140                                         get(ARM::t2CSEL), DestReg)
141                                     .add(MI.getOperand(2))
142                                     .add(MI.getOperand(1))
143                                     .add(MI.getOperand(3));
144     SeenMIs.insert(NewMI);
145     return NewMI;
146   }
147   return RV;
148 }
149 
150 void Thumb2InstrInfo::copyPhysReg(MachineBasicBlock &MBB,
151                                   MachineBasicBlock::iterator I,
152                                   const DebugLoc &DL, MCRegister DestReg,
153                                   MCRegister SrcReg, bool KillSrc) const {
154   // Handle SPR, DPR, and QPR copies.
155   if (!ARM::GPRRegClass.contains(DestReg, SrcReg))
156     return ARMBaseInstrInfo::copyPhysReg(MBB, I, DL, DestReg, SrcReg, KillSrc);
157 
158   BuildMI(MBB, I, DL, get(ARM::tMOVr), DestReg)
159       .addReg(SrcReg, getKillRegState(KillSrc))
160       .add(predOps(ARMCC::AL));
161 }
162 
163 void Thumb2InstrInfo::
164 storeRegToStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
165                     Register SrcReg, bool isKill, int FI,
166                     const TargetRegisterClass *RC,
167                     const TargetRegisterInfo *TRI) const {
168   DebugLoc DL;
169   if (I != MBB.end()) DL = I->getDebugLoc();
170 
171   MachineFunction &MF = *MBB.getParent();
172   MachineFrameInfo &MFI = MF.getFrameInfo();
173   MachineMemOperand *MMO = MF.getMachineMemOperand(
174       MachinePointerInfo::getFixedStack(MF, FI), MachineMemOperand::MOStore,
175       MFI.getObjectSize(FI), MFI.getObjectAlign(FI));
176 
177   if (ARM::GPRRegClass.hasSubClassEq(RC)) {
178     BuildMI(MBB, I, DL, get(ARM::t2STRi12))
179         .addReg(SrcReg, getKillRegState(isKill))
180         .addFrameIndex(FI)
181         .addImm(0)
182         .addMemOperand(MMO)
183         .add(predOps(ARMCC::AL));
184     return;
185   }
186 
187   if (ARM::GPRPairRegClass.hasSubClassEq(RC)) {
188     // Thumb2 STRD expects its dest-registers to be in rGPR. Not a problem for
189     // gsub_0, but needs an extra constraint for gsub_1 (which could be sp
190     // otherwise).
191     if (Register::isVirtualRegister(SrcReg)) {
192       MachineRegisterInfo *MRI = &MF.getRegInfo();
193       MRI->constrainRegClass(SrcReg, &ARM::GPRPairnospRegClass);
194     }
195 
196     MachineInstrBuilder MIB = BuildMI(MBB, I, DL, get(ARM::t2STRDi8));
197     AddDReg(MIB, SrcReg, ARM::gsub_0, getKillRegState(isKill), TRI);
198     AddDReg(MIB, SrcReg, ARM::gsub_1, 0, TRI);
199     MIB.addFrameIndex(FI).addImm(0).addMemOperand(MMO).add(predOps(ARMCC::AL));
200     return;
201   }
202 
203   ARMBaseInstrInfo::storeRegToStackSlot(MBB, I, SrcReg, isKill, FI, RC, TRI);
204 }
205 
206 void Thumb2InstrInfo::
207 loadRegFromStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
208                      Register DestReg, int FI,
209                      const TargetRegisterClass *RC,
210                      const TargetRegisterInfo *TRI) const {
211   MachineFunction &MF = *MBB.getParent();
212   MachineFrameInfo &MFI = MF.getFrameInfo();
213   MachineMemOperand *MMO = MF.getMachineMemOperand(
214       MachinePointerInfo::getFixedStack(MF, FI), MachineMemOperand::MOLoad,
215       MFI.getObjectSize(FI), MFI.getObjectAlign(FI));
216   DebugLoc DL;
217   if (I != MBB.end()) DL = I->getDebugLoc();
218 
219   if (ARM::GPRRegClass.hasSubClassEq(RC)) {
220     BuildMI(MBB, I, DL, get(ARM::t2LDRi12), DestReg)
221         .addFrameIndex(FI)
222         .addImm(0)
223         .addMemOperand(MMO)
224         .add(predOps(ARMCC::AL));
225     return;
226   }
227 
228   if (ARM::GPRPairRegClass.hasSubClassEq(RC)) {
229     // Thumb2 LDRD expects its dest-registers to be in rGPR. Not a problem for
230     // gsub_0, but needs an extra constraint for gsub_1 (which could be sp
231     // otherwise).
232     if (Register::isVirtualRegister(DestReg)) {
233       MachineRegisterInfo *MRI = &MF.getRegInfo();
234       MRI->constrainRegClass(DestReg, &ARM::GPRPairnospRegClass);
235     }
236 
237     MachineInstrBuilder MIB = BuildMI(MBB, I, DL, get(ARM::t2LDRDi8));
238     AddDReg(MIB, DestReg, ARM::gsub_0, RegState::DefineNoRead, TRI);
239     AddDReg(MIB, DestReg, ARM::gsub_1, RegState::DefineNoRead, TRI);
240     MIB.addFrameIndex(FI).addImm(0).addMemOperand(MMO).add(predOps(ARMCC::AL));
241 
242     if (Register::isPhysicalRegister(DestReg))
243       MIB.addReg(DestReg, RegState::ImplicitDefine);
244     return;
245   }
246 
247   ARMBaseInstrInfo::loadRegFromStackSlot(MBB, I, DestReg, FI, RC, TRI);
248 }
249 
250 void Thumb2InstrInfo::expandLoadStackGuard(
251     MachineBasicBlock::iterator MI) const {
252   MachineFunction &MF = *MI->getParent()->getParent();
253   Module &M = *MF.getFunction().getParent();
254 
255   if (M.getStackProtectorGuard() == "tls") {
256     expandLoadStackGuardBase(MI, ARM::t2MRC, ARM::t2LDRi12);
257     return;
258   }
259 
260   const GlobalValue *GV =
261       cast<GlobalValue>((*MI->memoperands_begin())->getValue());
262 
263   if (MF.getSubtarget<ARMSubtarget>().isGVInGOT(GV))
264     expandLoadStackGuardBase(MI, ARM::t2LDRLIT_ga_pcrel, ARM::t2LDRi12);
265   else if (MF.getTarget().isPositionIndependent())
266     expandLoadStackGuardBase(MI, ARM::t2MOV_ga_pcrel, ARM::t2LDRi12);
267   else
268     expandLoadStackGuardBase(MI, ARM::t2MOVi32imm, ARM::t2LDRi12);
269 }
270 
271 MachineInstr *Thumb2InstrInfo::commuteInstructionImpl(MachineInstr &MI,
272                                                       bool NewMI,
273                                                       unsigned OpIdx1,
274                                                       unsigned OpIdx2) const {
275   switch (MI.getOpcode()) {
276   case ARM::MVE_VMAXNMAf16:
277   case ARM::MVE_VMAXNMAf32:
278   case ARM::MVE_VMINNMAf16:
279   case ARM::MVE_VMINNMAf32:
280     // Don't allow predicated instructions to be commuted.
281     if (getVPTInstrPredicate(MI) != ARMVCC::None)
282       return nullptr;
283   }
284   return ARMBaseInstrInfo::commuteInstructionImpl(MI, NewMI, OpIdx1, OpIdx2);
285 }
286 
287 void llvm::emitT2RegPlusImmediate(MachineBasicBlock &MBB,
288                                   MachineBasicBlock::iterator &MBBI,
289                                   const DebugLoc &dl, Register DestReg,
290                                   Register BaseReg, int NumBytes,
291                                   ARMCC::CondCodes Pred, Register PredReg,
292                                   const ARMBaseInstrInfo &TII,
293                                   unsigned MIFlags) {
294   if (NumBytes == 0 && DestReg != BaseReg) {
295     BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), DestReg)
296       .addReg(BaseReg, RegState::Kill)
297       .addImm((unsigned)Pred).addReg(PredReg).setMIFlags(MIFlags);
298     return;
299   }
300 
301   bool isSub = NumBytes < 0;
302   if (isSub) NumBytes = -NumBytes;
303 
304   // If profitable, use a movw or movt to materialize the offset.
305   // FIXME: Use the scavenger to grab a scratch register.
306   if (DestReg != ARM::SP && DestReg != BaseReg &&
307       NumBytes >= 4096 &&
308       ARM_AM::getT2SOImmVal(NumBytes) == -1) {
309     bool Fits = false;
310     if (NumBytes < 65536) {
311       // Use a movw to materialize the 16-bit constant.
312       BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi16), DestReg)
313         .addImm(NumBytes)
314         .addImm((unsigned)Pred).addReg(PredReg).setMIFlags(MIFlags);
315       Fits = true;
316     } else if ((NumBytes & 0xffff) == 0) {
317       // Use a movt to materialize the 32-bit constant.
318       BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVTi16), DestReg)
319         .addReg(DestReg)
320         .addImm(NumBytes >> 16)
321         .addImm((unsigned)Pred).addReg(PredReg).setMIFlags(MIFlags);
322       Fits = true;
323     }
324 
325     if (Fits) {
326       if (isSub) {
327         BuildMI(MBB, MBBI, dl, TII.get(ARM::t2SUBrr), DestReg)
328             .addReg(BaseReg)
329             .addReg(DestReg, RegState::Kill)
330             .add(predOps(Pred, PredReg))
331             .add(condCodeOp())
332             .setMIFlags(MIFlags);
333       } else {
334         // Here we know that DestReg is not SP but we do not
335         // know anything about BaseReg. t2ADDrr is an invalid
336         // instruction is SP is used as the second argument, but
337         // is fine if SP is the first argument. To be sure we
338         // do not generate invalid encoding, put BaseReg first.
339         BuildMI(MBB, MBBI, dl, TII.get(ARM::t2ADDrr), DestReg)
340             .addReg(BaseReg)
341             .addReg(DestReg, RegState::Kill)
342             .add(predOps(Pred, PredReg))
343             .add(condCodeOp())
344             .setMIFlags(MIFlags);
345       }
346       return;
347     }
348   }
349 
350   while (NumBytes) {
351     unsigned ThisVal = NumBytes;
352     unsigned Opc = 0;
353     if (DestReg == ARM::SP && BaseReg != ARM::SP) {
354       // mov sp, rn. Note t2MOVr cannot be used.
355       BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), DestReg)
356           .addReg(BaseReg)
357           .setMIFlags(MIFlags)
358           .add(predOps(ARMCC::AL));
359       BaseReg = ARM::SP;
360       continue;
361     }
362 
363     assert((DestReg != ARM::SP || BaseReg == ARM::SP) &&
364            "Writing to SP, from other register.");
365 
366     // Try to use T1, as it smaller
367     if ((DestReg == ARM::SP) && (ThisVal < ((1 << 7) - 1) * 4)) {
368       assert((ThisVal & 3) == 0 && "Stack update is not multiple of 4?");
369       Opc = isSub ? ARM::tSUBspi : ARM::tADDspi;
370       BuildMI(MBB, MBBI, dl, TII.get(Opc), DestReg)
371           .addReg(BaseReg)
372           .addImm(ThisVal / 4)
373           .setMIFlags(MIFlags)
374           .add(predOps(ARMCC::AL));
375       break;
376     }
377     bool HasCCOut = true;
378     int ImmIsT2SO = ARM_AM::getT2SOImmVal(ThisVal);
379     bool ToSP = DestReg == ARM::SP;
380     unsigned t2SUB = ToSP ? ARM::t2SUBspImm : ARM::t2SUBri;
381     unsigned t2ADD = ToSP ? ARM::t2ADDspImm : ARM::t2ADDri;
382     unsigned t2SUBi12 = ToSP ? ARM::t2SUBspImm12 : ARM::t2SUBri12;
383     unsigned t2ADDi12 = ToSP ? ARM::t2ADDspImm12 : ARM::t2ADDri12;
384     Opc = isSub ? t2SUB : t2ADD;
385     // Prefer T2: sub rd, rn, so_imm | sub sp, sp, so_imm
386     if (ImmIsT2SO != -1) {
387       NumBytes = 0;
388     } else if (ThisVal < 4096) {
389       // Prefer T3 if can make it in a single go: subw rd, rn, imm12 | subw sp,
390       // sp, imm12
391       Opc = isSub ? t2SUBi12 : t2ADDi12;
392       HasCCOut = false;
393       NumBytes = 0;
394     } else {
395       // Use one T2 instruction to reduce NumBytes
396       // FIXME: Move this to ARMAddressingModes.h?
397       unsigned RotAmt = countLeadingZeros(ThisVal);
398       ThisVal = ThisVal & ARM_AM::rotr32(0xff000000U, RotAmt);
399       NumBytes &= ~ThisVal;
400       assert(ARM_AM::getT2SOImmVal(ThisVal) != -1 &&
401              "Bit extraction didn't work?");
402     }
403 
404     // Build the new ADD / SUB.
405     MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII.get(Opc), DestReg)
406                                   .addReg(BaseReg, RegState::Kill)
407                                   .addImm(ThisVal)
408                                   .add(predOps(ARMCC::AL))
409                                   .setMIFlags(MIFlags);
410     if (HasCCOut)
411       MIB.add(condCodeOp());
412 
413     BaseReg = DestReg;
414   }
415 }
416 
417 static unsigned
418 negativeOffsetOpcode(unsigned opcode)
419 {
420   switch (opcode) {
421   case ARM::t2LDRi12:   return ARM::t2LDRi8;
422   case ARM::t2LDRHi12:  return ARM::t2LDRHi8;
423   case ARM::t2LDRBi12:  return ARM::t2LDRBi8;
424   case ARM::t2LDRSHi12: return ARM::t2LDRSHi8;
425   case ARM::t2LDRSBi12: return ARM::t2LDRSBi8;
426   case ARM::t2STRi12:   return ARM::t2STRi8;
427   case ARM::t2STRBi12:  return ARM::t2STRBi8;
428   case ARM::t2STRHi12:  return ARM::t2STRHi8;
429   case ARM::t2PLDi12:   return ARM::t2PLDi8;
430   case ARM::t2PLDWi12:  return ARM::t2PLDWi8;
431   case ARM::t2PLIi12:   return ARM::t2PLIi8;
432 
433   case ARM::t2LDRi8:
434   case ARM::t2LDRHi8:
435   case ARM::t2LDRBi8:
436   case ARM::t2LDRSHi8:
437   case ARM::t2LDRSBi8:
438   case ARM::t2STRi8:
439   case ARM::t2STRBi8:
440   case ARM::t2STRHi8:
441   case ARM::t2PLDi8:
442   case ARM::t2PLDWi8:
443   case ARM::t2PLIi8:
444     return opcode;
445 
446   default:
447     llvm_unreachable("unknown thumb2 opcode.");
448   }
449 }
450 
451 static unsigned
452 positiveOffsetOpcode(unsigned opcode)
453 {
454   switch (opcode) {
455   case ARM::t2LDRi8:   return ARM::t2LDRi12;
456   case ARM::t2LDRHi8:  return ARM::t2LDRHi12;
457   case ARM::t2LDRBi8:  return ARM::t2LDRBi12;
458   case ARM::t2LDRSHi8: return ARM::t2LDRSHi12;
459   case ARM::t2LDRSBi8: return ARM::t2LDRSBi12;
460   case ARM::t2STRi8:   return ARM::t2STRi12;
461   case ARM::t2STRBi8:  return ARM::t2STRBi12;
462   case ARM::t2STRHi8:  return ARM::t2STRHi12;
463   case ARM::t2PLDi8:   return ARM::t2PLDi12;
464   case ARM::t2PLDWi8:  return ARM::t2PLDWi12;
465   case ARM::t2PLIi8:   return ARM::t2PLIi12;
466 
467   case ARM::t2LDRi12:
468   case ARM::t2LDRHi12:
469   case ARM::t2LDRBi12:
470   case ARM::t2LDRSHi12:
471   case ARM::t2LDRSBi12:
472   case ARM::t2STRi12:
473   case ARM::t2STRBi12:
474   case ARM::t2STRHi12:
475   case ARM::t2PLDi12:
476   case ARM::t2PLDWi12:
477   case ARM::t2PLIi12:
478     return opcode;
479 
480   default:
481     llvm_unreachable("unknown thumb2 opcode.");
482   }
483 }
484 
485 static unsigned
486 immediateOffsetOpcode(unsigned opcode)
487 {
488   switch (opcode) {
489   case ARM::t2LDRs:   return ARM::t2LDRi12;
490   case ARM::t2LDRHs:  return ARM::t2LDRHi12;
491   case ARM::t2LDRBs:  return ARM::t2LDRBi12;
492   case ARM::t2LDRSHs: return ARM::t2LDRSHi12;
493   case ARM::t2LDRSBs: return ARM::t2LDRSBi12;
494   case ARM::t2STRs:   return ARM::t2STRi12;
495   case ARM::t2STRBs:  return ARM::t2STRBi12;
496   case ARM::t2STRHs:  return ARM::t2STRHi12;
497   case ARM::t2PLDs:   return ARM::t2PLDi12;
498   case ARM::t2PLDWs:  return ARM::t2PLDWi12;
499   case ARM::t2PLIs:   return ARM::t2PLIi12;
500 
501   case ARM::t2LDRi12:
502   case ARM::t2LDRHi12:
503   case ARM::t2LDRBi12:
504   case ARM::t2LDRSHi12:
505   case ARM::t2LDRSBi12:
506   case ARM::t2STRi12:
507   case ARM::t2STRBi12:
508   case ARM::t2STRHi12:
509   case ARM::t2PLDi12:
510   case ARM::t2PLDWi12:
511   case ARM::t2PLIi12:
512   case ARM::t2LDRi8:
513   case ARM::t2LDRHi8:
514   case ARM::t2LDRBi8:
515   case ARM::t2LDRSHi8:
516   case ARM::t2LDRSBi8:
517   case ARM::t2STRi8:
518   case ARM::t2STRBi8:
519   case ARM::t2STRHi8:
520   case ARM::t2PLDi8:
521   case ARM::t2PLDWi8:
522   case ARM::t2PLIi8:
523     return opcode;
524 
525   default:
526     llvm_unreachable("unknown thumb2 opcode.");
527   }
528 }
529 
530 bool llvm::rewriteT2FrameIndex(MachineInstr &MI, unsigned FrameRegIdx,
531                                Register FrameReg, int &Offset,
532                                const ARMBaseInstrInfo &TII,
533                                const TargetRegisterInfo *TRI) {
534   unsigned Opcode = MI.getOpcode();
535   const MCInstrDesc &Desc = MI.getDesc();
536   unsigned AddrMode = (Desc.TSFlags & ARMII::AddrModeMask);
537   bool isSub = false;
538 
539   MachineFunction &MF = *MI.getParent()->getParent();
540   const TargetRegisterClass *RegClass =
541       TII.getRegClass(Desc, FrameRegIdx, TRI, MF);
542 
543   // Memory operands in inline assembly always use AddrModeT2_i12.
544   if (Opcode == ARM::INLINEASM || Opcode == ARM::INLINEASM_BR)
545     AddrMode = ARMII::AddrModeT2_i12; // FIXME. mode for thumb2?
546 
547   const bool IsSP = Opcode == ARM::t2ADDspImm12 || Opcode == ARM::t2ADDspImm;
548   if (IsSP || Opcode == ARM::t2ADDri || Opcode == ARM::t2ADDri12) {
549     Offset += MI.getOperand(FrameRegIdx+1).getImm();
550 
551     Register PredReg;
552     if (Offset == 0 && getInstrPredicate(MI, PredReg) == ARMCC::AL &&
553         !MI.definesRegister(ARM::CPSR)) {
554       // Turn it into a move.
555       MI.setDesc(TII.get(ARM::tMOVr));
556       MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
557       // Remove offset and remaining explicit predicate operands.
558       do MI.removeOperand(FrameRegIdx+1);
559       while (MI.getNumOperands() > FrameRegIdx+1);
560       MachineInstrBuilder MIB(*MI.getParent()->getParent(), &MI);
561       MIB.add(predOps(ARMCC::AL));
562       return true;
563     }
564 
565     bool HasCCOut = (Opcode != ARM::t2ADDspImm12 && Opcode != ARM::t2ADDri12);
566 
567     if (Offset < 0) {
568       Offset = -Offset;
569       isSub = true;
570       MI.setDesc(IsSP ? TII.get(ARM::t2SUBspImm) : TII.get(ARM::t2SUBri));
571     } else {
572       MI.setDesc(IsSP ? TII.get(ARM::t2ADDspImm) : TII.get(ARM::t2ADDri));
573     }
574 
575     // Common case: small offset, fits into instruction.
576     if (ARM_AM::getT2SOImmVal(Offset) != -1) {
577       MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
578       MI.getOperand(FrameRegIdx+1).ChangeToImmediate(Offset);
579       // Add cc_out operand if the original instruction did not have one.
580       if (!HasCCOut)
581         MI.addOperand(MachineOperand::CreateReg(0, false));
582       Offset = 0;
583       return true;
584     }
585     // Another common case: imm12.
586     if (Offset < 4096 &&
587         (!HasCCOut || MI.getOperand(MI.getNumOperands()-1).getReg() == 0)) {
588       unsigned NewOpc = isSub ? IsSP ? ARM::t2SUBspImm12 : ARM::t2SUBri12
589                               : IsSP ? ARM::t2ADDspImm12 : ARM::t2ADDri12;
590       MI.setDesc(TII.get(NewOpc));
591       MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
592       MI.getOperand(FrameRegIdx+1).ChangeToImmediate(Offset);
593       // Remove the cc_out operand.
594       if (HasCCOut)
595         MI.removeOperand(MI.getNumOperands()-1);
596       Offset = 0;
597       return true;
598     }
599 
600     // Otherwise, extract 8 adjacent bits from the immediate into this
601     // t2ADDri/t2SUBri.
602     unsigned RotAmt = countLeadingZeros<unsigned>(Offset);
603     unsigned ThisImmVal = Offset & ARM_AM::rotr32(0xff000000U, RotAmt);
604 
605     // We will handle these bits from offset, clear them.
606     Offset &= ~ThisImmVal;
607 
608     assert(ARM_AM::getT2SOImmVal(ThisImmVal) != -1 &&
609            "Bit extraction didn't work?");
610     MI.getOperand(FrameRegIdx+1).ChangeToImmediate(ThisImmVal);
611     // Add cc_out operand if the original instruction did not have one.
612     if (!HasCCOut)
613       MI.addOperand(MachineOperand::CreateReg(0, false));
614   } else {
615     // AddrMode4 and AddrMode6 cannot handle any offset.
616     if (AddrMode == ARMII::AddrMode4 || AddrMode == ARMII::AddrMode6)
617       return false;
618 
619     // AddrModeT2_so cannot handle any offset. If there is no offset
620     // register then we change to an immediate version.
621     unsigned NewOpc = Opcode;
622     if (AddrMode == ARMII::AddrModeT2_so) {
623       Register OffsetReg = MI.getOperand(FrameRegIdx + 1).getReg();
624       if (OffsetReg != 0) {
625         MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
626         return Offset == 0;
627       }
628 
629       MI.removeOperand(FrameRegIdx+1);
630       MI.getOperand(FrameRegIdx+1).ChangeToImmediate(0);
631       NewOpc = immediateOffsetOpcode(Opcode);
632       AddrMode = ARMII::AddrModeT2_i12;
633     }
634 
635     unsigned NumBits = 0;
636     unsigned Scale = 1;
637     if (AddrMode == ARMII::AddrModeT2_i8neg ||
638         AddrMode == ARMII::AddrModeT2_i12) {
639       // i8 supports only negative, and i12 supports only positive, so
640       // based on Offset sign convert Opcode to the appropriate
641       // instruction
642       Offset += MI.getOperand(FrameRegIdx+1).getImm();
643       if (Offset < 0) {
644         NewOpc = negativeOffsetOpcode(Opcode);
645         NumBits = 8;
646         isSub = true;
647         Offset = -Offset;
648       } else {
649         NewOpc = positiveOffsetOpcode(Opcode);
650         NumBits = 12;
651       }
652     } else if (AddrMode == ARMII::AddrMode5) {
653       // VFP address mode.
654       const MachineOperand &OffOp = MI.getOperand(FrameRegIdx+1);
655       int InstrOffs = ARM_AM::getAM5Offset(OffOp.getImm());
656       if (ARM_AM::getAM5Op(OffOp.getImm()) == ARM_AM::sub)
657         InstrOffs *= -1;
658       NumBits = 8;
659       Scale = 4;
660       Offset += InstrOffs * 4;
661       assert((Offset & (Scale-1)) == 0 && "Can't encode this offset!");
662       if (Offset < 0) {
663         Offset = -Offset;
664         isSub = true;
665       }
666     } else if (AddrMode == ARMII::AddrMode5FP16) {
667       // VFP address mode.
668       const MachineOperand &OffOp = MI.getOperand(FrameRegIdx+1);
669       int InstrOffs = ARM_AM::getAM5FP16Offset(OffOp.getImm());
670       if (ARM_AM::getAM5FP16Op(OffOp.getImm()) == ARM_AM::sub)
671         InstrOffs *= -1;
672       NumBits = 8;
673       Scale = 2;
674       Offset += InstrOffs * 2;
675       assert((Offset & (Scale-1)) == 0 && "Can't encode this offset!");
676       if (Offset < 0) {
677         Offset = -Offset;
678         isSub = true;
679       }
680     } else if (AddrMode == ARMII::AddrModeT2_i7s4 ||
681                AddrMode == ARMII::AddrModeT2_i7s2 ||
682                AddrMode == ARMII::AddrModeT2_i7) {
683       Offset += MI.getOperand(FrameRegIdx + 1).getImm();
684       unsigned OffsetMask;
685       switch (AddrMode) {
686       case ARMII::AddrModeT2_i7s4: NumBits = 9; OffsetMask = 0x3; break;
687       case ARMII::AddrModeT2_i7s2: NumBits = 8; OffsetMask = 0x1; break;
688       default:                     NumBits = 7; OffsetMask = 0x0; break;
689       }
690       // MCInst operand expects already scaled value.
691       Scale = 1;
692       assert((Offset & OffsetMask) == 0 && "Can't encode this offset!");
693       (void)OffsetMask; // squash unused-variable warning at -NDEBUG
694     } else if (AddrMode == ARMII::AddrModeT2_i8s4) {
695       Offset += MI.getOperand(FrameRegIdx + 1).getImm();
696       NumBits = 8 + 2;
697       // MCInst operand expects already scaled value.
698       Scale = 1;
699       assert((Offset & 3) == 0 && "Can't encode this offset!");
700     } else if (AddrMode == ARMII::AddrModeT2_ldrex) {
701       Offset += MI.getOperand(FrameRegIdx + 1).getImm() * 4;
702       NumBits = 8; // 8 bits scaled by 4
703       Scale = 4;
704       assert((Offset & 3) == 0 && "Can't encode this offset!");
705     } else {
706       llvm_unreachable("Unsupported addressing mode!");
707     }
708 
709     if (NewOpc != Opcode)
710       MI.setDesc(TII.get(NewOpc));
711 
712     MachineOperand &ImmOp = MI.getOperand(FrameRegIdx+1);
713 
714     // Attempt to fold address computation
715     // Common case: small offset, fits into instruction. We need to make sure
716     // the register class is correct too, for instructions like the MVE
717     // VLDRH.32, which only accepts low tGPR registers.
718     int ImmedOffset = Offset / Scale;
719     unsigned Mask = (1 << NumBits) - 1;
720     if ((unsigned)Offset <= Mask * Scale &&
721         (Register::isVirtualRegister(FrameReg) ||
722          RegClass->contains(FrameReg))) {
723       if (Register::isVirtualRegister(FrameReg)) {
724         // Make sure the register class for the virtual register is correct
725         MachineRegisterInfo *MRI = &MF.getRegInfo();
726         if (!MRI->constrainRegClass(FrameReg, RegClass))
727           llvm_unreachable("Unable to constrain virtual register class.");
728       }
729 
730       // Replace the FrameIndex with fp/sp
731       MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
732       if (isSub) {
733         if (AddrMode == ARMII::AddrMode5 || AddrMode == ARMII::AddrMode5FP16)
734           // FIXME: Not consistent.
735           ImmedOffset |= 1 << NumBits;
736         else
737           ImmedOffset = -ImmedOffset;
738       }
739       ImmOp.ChangeToImmediate(ImmedOffset);
740       Offset = 0;
741       return true;
742     }
743 
744     // Otherwise, offset doesn't fit. Pull in what we can to simplify
745     ImmedOffset = ImmedOffset & Mask;
746     if (isSub) {
747       if (AddrMode == ARMII::AddrMode5 || AddrMode == ARMII::AddrMode5FP16)
748         // FIXME: Not consistent.
749         ImmedOffset |= 1 << NumBits;
750       else {
751         ImmedOffset = -ImmedOffset;
752         if (ImmedOffset == 0)
753           // Change the opcode back if the encoded offset is zero.
754           MI.setDesc(TII.get(positiveOffsetOpcode(NewOpc)));
755       }
756     }
757     ImmOp.ChangeToImmediate(ImmedOffset);
758     Offset &= ~(Mask*Scale);
759   }
760 
761   Offset = (isSub) ? -Offset : Offset;
762   return Offset == 0 && (Register::isVirtualRegister(FrameReg) ||
763                          RegClass->contains(FrameReg));
764 }
765 
766 ARMCC::CondCodes llvm::getITInstrPredicate(const MachineInstr &MI,
767                                            Register &PredReg) {
768   unsigned Opc = MI.getOpcode();
769   if (Opc == ARM::tBcc || Opc == ARM::t2Bcc)
770     return ARMCC::AL;
771   return getInstrPredicate(MI, PredReg);
772 }
773 
774 int llvm::findFirstVPTPredOperandIdx(const MachineInstr &MI) {
775   const MCInstrDesc &MCID = MI.getDesc();
776 
777   if (!MCID.OpInfo)
778     return -1;
779 
780   for (unsigned i = 0, e = MCID.getNumOperands(); i != e; ++i)
781     if (ARM::isVpred(MCID.OpInfo[i].OperandType))
782       return i;
783 
784   return -1;
785 }
786 
787 ARMVCC::VPTCodes llvm::getVPTInstrPredicate(const MachineInstr &MI,
788                                             Register &PredReg) {
789   int PIdx = findFirstVPTPredOperandIdx(MI);
790   if (PIdx == -1) {
791     PredReg = 0;
792     return ARMVCC::None;
793   }
794 
795   PredReg = MI.getOperand(PIdx+1).getReg();
796   return (ARMVCC::VPTCodes)MI.getOperand(PIdx).getImm();
797 }
798 
799 void llvm::recomputeVPTBlockMask(MachineInstr &Instr) {
800   assert(isVPTOpcode(Instr.getOpcode()) && "Not a VPST or VPT Instruction!");
801 
802   MachineOperand &MaskOp = Instr.getOperand(0);
803   assert(MaskOp.isImm() && "Operand 0 is not the block mask of the VPT/VPST?!");
804 
805   MachineBasicBlock::iterator Iter = ++Instr.getIterator(),
806                               End = Instr.getParent()->end();
807 
808   while (Iter != End && Iter->isDebugInstr())
809     ++Iter;
810 
811   // Verify that the instruction after the VPT/VPST is predicated (it should
812   // be), and skip it.
813   assert(Iter != End && "Expected some instructions in any VPT block");
814   assert(
815       getVPTInstrPredicate(*Iter) == ARMVCC::Then &&
816       "VPT/VPST should be followed by an instruction with a 'then' predicate!");
817   ++Iter;
818 
819   // Iterate over the predicated instructions, updating the BlockMask as we go.
820   ARM::PredBlockMask BlockMask = ARM::PredBlockMask::T;
821   while (Iter != End) {
822     if (Iter->isDebugInstr()) {
823       ++Iter;
824       continue;
825     }
826     ARMVCC::VPTCodes Pred = getVPTInstrPredicate(*Iter);
827     if (Pred == ARMVCC::None)
828       break;
829     BlockMask = expandPredBlockMask(BlockMask, Pred);
830     ++Iter;
831   }
832 
833   // Rewrite the BlockMask.
834   MaskOp.setImm((int64_t)(BlockMask));
835 }
836