1 //===- Mips16InstrInfo.cpp - Mips16 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 Mips16 implementation of the TargetInstrInfo class.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "Mips16InstrInfo.h"
14 #include "llvm/ADT/BitVector.h"
15 #include "llvm/CodeGen/MachineBasicBlock.h"
16 #include "llvm/CodeGen/MachineFrameInfo.h"
17 #include "llvm/CodeGen/MachineFunction.h"
18 #include "llvm/CodeGen/MachineInstr.h"
19 #include "llvm/CodeGen/MachineInstrBuilder.h"
20 #include "llvm/CodeGen/MachineMemOperand.h"
21 #include "llvm/CodeGen/MachineOperand.h"
22 #include "llvm/CodeGen/RegisterScavenging.h"
23 #include "llvm/CodeGen/TargetRegisterInfo.h"
24 #include "llvm/IR/DebugLoc.h"
25 #include "llvm/MC/MCAsmInfo.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/MathExtras.h"
29 #include "llvm/Support/raw_ostream.h"
30 #include <cassert>
31 #include <cctype>
32 #include <cstdint>
33 #include <cstdlib>
34 #include <cstring>
35 #include <iterator>
36 #include <vector>
37
38 using namespace llvm;
39
40 #define DEBUG_TYPE "mips16-instrinfo"
41
Mips16InstrInfo(const MipsSubtarget & STI)42 Mips16InstrInfo::Mips16InstrInfo(const MipsSubtarget &STI)
43 : MipsInstrInfo(STI, Mips::Bimm16) {}
44
getRegisterInfo() const45 const MipsRegisterInfo &Mips16InstrInfo::getRegisterInfo() const {
46 return RI;
47 }
48
49 /// isLoadFromStackSlot - If the specified machine instruction is a direct
50 /// load from a stack slot, return the virtual or physical register number of
51 /// the destination along with the FrameIndex of the loaded stack slot. If
52 /// not, return 0. This predicate must return 0 if the instruction has
53 /// any side effects other than loading from the stack slot.
isLoadFromStackSlot(const MachineInstr & MI,int & FrameIndex) const54 Register Mips16InstrInfo::isLoadFromStackSlot(const MachineInstr &MI,
55 int &FrameIndex) const {
56 return 0;
57 }
58
59 /// isStoreToStackSlot - If the specified machine instruction is a direct
60 /// store to a stack slot, return the virtual or physical register number of
61 /// the source reg along with the FrameIndex of the loaded stack slot. If
62 /// not, return 0. This predicate must return 0 if the instruction has
63 /// any side effects other than storing to the stack slot.
isStoreToStackSlot(const MachineInstr & MI,int & FrameIndex) const64 Register Mips16InstrInfo::isStoreToStackSlot(const MachineInstr &MI,
65 int &FrameIndex) const {
66 return 0;
67 }
68
copyPhysReg(MachineBasicBlock & MBB,MachineBasicBlock::iterator I,const DebugLoc & DL,MCRegister DestReg,MCRegister SrcReg,bool KillSrc) const69 void Mips16InstrInfo::copyPhysReg(MachineBasicBlock &MBB,
70 MachineBasicBlock::iterator I,
71 const DebugLoc &DL, MCRegister DestReg,
72 MCRegister SrcReg, bool KillSrc) const {
73 unsigned Opc = 0;
74
75 if (Mips::CPU16RegsRegClass.contains(DestReg) &&
76 Mips::GPR32RegClass.contains(SrcReg))
77 Opc = Mips::MoveR3216;
78 else if (Mips::GPR32RegClass.contains(DestReg) &&
79 Mips::CPU16RegsRegClass.contains(SrcReg))
80 Opc = Mips::Move32R16;
81 else if ((SrcReg == Mips::HI0) &&
82 (Mips::CPU16RegsRegClass.contains(DestReg)))
83 Opc = Mips::Mfhi16, SrcReg = 0;
84 else if ((SrcReg == Mips::LO0) &&
85 (Mips::CPU16RegsRegClass.contains(DestReg)))
86 Opc = Mips::Mflo16, SrcReg = 0;
87
88 assert(Opc && "Cannot copy registers");
89
90 MachineInstrBuilder MIB = BuildMI(MBB, I, DL, get(Opc));
91
92 if (DestReg)
93 MIB.addReg(DestReg, RegState::Define);
94
95 if (SrcReg)
96 MIB.addReg(SrcReg, getKillRegState(KillSrc));
97 }
98
99 std::optional<DestSourcePair>
isCopyInstrImpl(const MachineInstr & MI) const100 Mips16InstrInfo::isCopyInstrImpl(const MachineInstr &MI) const {
101 if (MI.isMoveReg())
102 return DestSourcePair{MI.getOperand(0), MI.getOperand(1)};
103 return std::nullopt;
104 }
105
storeRegToStack(MachineBasicBlock & MBB,MachineBasicBlock::iterator I,Register SrcReg,bool isKill,int FI,const TargetRegisterClass * RC,const TargetRegisterInfo * TRI,int64_t Offset) const106 void Mips16InstrInfo::storeRegToStack(MachineBasicBlock &MBB,
107 MachineBasicBlock::iterator I,
108 Register SrcReg, bool isKill, int FI,
109 const TargetRegisterClass *RC,
110 const TargetRegisterInfo *TRI,
111 int64_t Offset) const {
112 DebugLoc DL;
113 if (I != MBB.end()) DL = I->getDebugLoc();
114 MachineMemOperand *MMO = GetMemOperand(MBB, FI, MachineMemOperand::MOStore);
115 unsigned Opc = 0;
116 if (Mips::CPU16RegsRegClass.hasSubClassEq(RC))
117 Opc = Mips::SwRxSpImmX16;
118 assert(Opc && "Register class not handled!");
119 BuildMI(MBB, I, DL, get(Opc)).addReg(SrcReg, getKillRegState(isKill)).
120 addFrameIndex(FI).addImm(Offset)
121 .addMemOperand(MMO);
122 }
123
loadRegFromStack(MachineBasicBlock & MBB,MachineBasicBlock::iterator I,Register DestReg,int FI,const TargetRegisterClass * RC,const TargetRegisterInfo * TRI,int64_t Offset) const124 void Mips16InstrInfo::loadRegFromStack(MachineBasicBlock &MBB,
125 MachineBasicBlock::iterator I,
126 Register DestReg, int FI,
127 const TargetRegisterClass *RC,
128 const TargetRegisterInfo *TRI,
129 int64_t Offset) const {
130 DebugLoc DL;
131 if (I != MBB.end()) DL = I->getDebugLoc();
132 MachineMemOperand *MMO = GetMemOperand(MBB, FI, MachineMemOperand::MOLoad);
133 unsigned Opc = 0;
134
135 if (Mips::CPU16RegsRegClass.hasSubClassEq(RC))
136 Opc = Mips::LwRxSpImmX16;
137 assert(Opc && "Register class not handled!");
138 BuildMI(MBB, I, DL, get(Opc), DestReg).addFrameIndex(FI).addImm(Offset)
139 .addMemOperand(MMO);
140 }
141
expandPostRAPseudo(MachineInstr & MI) const142 bool Mips16InstrInfo::expandPostRAPseudo(MachineInstr &MI) const {
143 MachineBasicBlock &MBB = *MI.getParent();
144 switch (MI.getDesc().getOpcode()) {
145 default:
146 return false;
147 case Mips::RetRA16:
148 ExpandRetRA16(MBB, MI, Mips::JrcRa16);
149 break;
150 }
151
152 MBB.erase(MI.getIterator());
153 return true;
154 }
155
156 /// GetOppositeBranchOpc - Return the inverse of the specified
157 /// opcode, e.g. turning BEQ to BNE.
getOppositeBranchOpc(unsigned Opc) const158 unsigned Mips16InstrInfo::getOppositeBranchOpc(unsigned Opc) const {
159 switch (Opc) {
160 case Mips::BeqzRxImmX16: return Mips::BnezRxImmX16;
161 case Mips::BnezRxImmX16: return Mips::BeqzRxImmX16;
162 case Mips::BeqzRxImm16: return Mips::BnezRxImm16;
163 case Mips::BnezRxImm16: return Mips::BeqzRxImm16;
164 case Mips::BteqzT8CmpX16: return Mips::BtnezT8CmpX16;
165 case Mips::BteqzT8SltX16: return Mips::BtnezT8SltX16;
166 case Mips::BteqzT8SltiX16: return Mips::BtnezT8SltiX16;
167 case Mips::Btnez16: return Mips::Bteqz16;
168 case Mips::BtnezX16: return Mips::BteqzX16;
169 case Mips::BtnezT8CmpiX16: return Mips::BteqzT8CmpiX16;
170 case Mips::BtnezT8SltuX16: return Mips::BteqzT8SltuX16;
171 case Mips::BtnezT8SltiuX16: return Mips::BteqzT8SltiuX16;
172 case Mips::Bteqz16: return Mips::Btnez16;
173 case Mips::BteqzX16: return Mips::BtnezX16;
174 case Mips::BteqzT8CmpiX16: return Mips::BtnezT8CmpiX16;
175 case Mips::BteqzT8SltuX16: return Mips::BtnezT8SltuX16;
176 case Mips::BteqzT8SltiuX16: return Mips::BtnezT8SltiuX16;
177 case Mips::BtnezT8CmpX16: return Mips::BteqzT8CmpX16;
178 case Mips::BtnezT8SltX16: return Mips::BteqzT8SltX16;
179 case Mips::BtnezT8SltiX16: return Mips::BteqzT8SltiX16;
180 }
181 llvm_unreachable("Illegal opcode!");
182 }
183
addSaveRestoreRegs(MachineInstrBuilder & MIB,ArrayRef<CalleeSavedInfo> CSI,unsigned Flags=0)184 static void addSaveRestoreRegs(MachineInstrBuilder &MIB,
185 ArrayRef<CalleeSavedInfo> CSI,
186 unsigned Flags = 0) {
187 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
188 // Add the callee-saved register as live-in. Do not add if the register is
189 // RA and return address is taken, because it has already been added in
190 // method MipsTargetLowering::lowerRETURNADDR.
191 // It's killed at the spill, unless the register is RA and return address
192 // is taken.
193 Register Reg = CSI[e-i-1].getReg();
194 switch (Reg) {
195 case Mips::RA:
196 case Mips::S0:
197 case Mips::S1:
198 MIB.addReg(Reg, Flags);
199 break;
200 case Mips::S2:
201 break;
202 default:
203 llvm_unreachable("unexpected mips16 callee saved register");
204
205 }
206 }
207 }
208
209 // Adjust SP by FrameSize bytes. Save RA, S0, S1
makeFrame(unsigned SP,int64_t FrameSize,MachineBasicBlock & MBB,MachineBasicBlock::iterator I) const210 void Mips16InstrInfo::makeFrame(unsigned SP, int64_t FrameSize,
211 MachineBasicBlock &MBB,
212 MachineBasicBlock::iterator I) const {
213 DebugLoc DL;
214 MachineFunction &MF = *MBB.getParent();
215 MachineFrameInfo &MFI = MF.getFrameInfo();
216 const BitVector Reserved = RI.getReservedRegs(MF);
217 bool SaveS2 = Reserved[Mips::S2];
218 MachineInstrBuilder MIB;
219 unsigned Opc = ((FrameSize <= 128) && !SaveS2)? Mips::Save16:Mips::SaveX16;
220 MIB = BuildMI(MBB, I, DL, get(Opc));
221 const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
222 addSaveRestoreRegs(MIB, CSI);
223 if (SaveS2)
224 MIB.addReg(Mips::S2);
225 if (isUInt<11>(FrameSize))
226 MIB.addImm(FrameSize);
227 else {
228 int Base = 2040; // should create template function like isUInt that
229 // returns largest possible n bit unsigned integer
230 int64_t Remainder = FrameSize - Base;
231 MIB.addImm(Base);
232 if (isInt<16>(-Remainder))
233 BuildAddiuSpImm(MBB, I, -Remainder);
234 else
235 adjustStackPtrBig(SP, -Remainder, MBB, I, Mips::V0, Mips::V1);
236 }
237 }
238
239 // Adjust SP by FrameSize bytes. Restore RA, S0, S1
restoreFrame(unsigned SP,int64_t FrameSize,MachineBasicBlock & MBB,MachineBasicBlock::iterator I) const240 void Mips16InstrInfo::restoreFrame(unsigned SP, int64_t FrameSize,
241 MachineBasicBlock &MBB,
242 MachineBasicBlock::iterator I) const {
243 DebugLoc DL = I != MBB.end() ? I->getDebugLoc() : DebugLoc();
244 MachineFunction *MF = MBB.getParent();
245 MachineFrameInfo &MFI = MF->getFrameInfo();
246 const BitVector Reserved = RI.getReservedRegs(*MF);
247 bool SaveS2 = Reserved[Mips::S2];
248 MachineInstrBuilder MIB;
249 unsigned Opc = ((FrameSize <= 128) && !SaveS2)?
250 Mips::Restore16:Mips::RestoreX16;
251
252 if (!isUInt<11>(FrameSize)) {
253 unsigned Base = 2040;
254 int64_t Remainder = FrameSize - Base;
255 FrameSize = Base; // should create template function like isUInt that
256 // returns largest possible n bit unsigned integer
257
258 if (isInt<16>(Remainder))
259 BuildAddiuSpImm(MBB, I, Remainder);
260 else
261 adjustStackPtrBig(SP, Remainder, MBB, I, Mips::A0, Mips::A1);
262 }
263 MIB = BuildMI(MBB, I, DL, get(Opc));
264 const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
265 addSaveRestoreRegs(MIB, CSI, RegState::Define);
266 if (SaveS2)
267 MIB.addReg(Mips::S2, RegState::Define);
268 MIB.addImm(FrameSize);
269 }
270
271 // Adjust SP by Amount bytes where bytes can be up to 32bit number.
272 // This can only be called at times that we know that there is at least one free
273 // register.
274 // This is clearly safe at prologue and epilogue.
adjustStackPtrBig(unsigned SP,int64_t Amount,MachineBasicBlock & MBB,MachineBasicBlock::iterator I,unsigned Reg1,unsigned Reg2) const275 void Mips16InstrInfo::adjustStackPtrBig(unsigned SP, int64_t Amount,
276 MachineBasicBlock &MBB,
277 MachineBasicBlock::iterator I,
278 unsigned Reg1, unsigned Reg2) const {
279 DebugLoc DL;
280 //
281 // li reg1, constant
282 // move reg2, sp
283 // add reg1, reg1, reg2
284 // move sp, reg1
285 //
286 //
287 MachineInstrBuilder MIB1 = BuildMI(MBB, I, DL, get(Mips::LwConstant32), Reg1);
288 MIB1.addImm(Amount).addImm(-1);
289 MachineInstrBuilder MIB2 = BuildMI(MBB, I, DL, get(Mips::MoveR3216), Reg2);
290 MIB2.addReg(Mips::SP, RegState::Kill);
291 MachineInstrBuilder MIB3 = BuildMI(MBB, I, DL, get(Mips::AdduRxRyRz16), Reg1);
292 MIB3.addReg(Reg1);
293 MIB3.addReg(Reg2, RegState::Kill);
294 MachineInstrBuilder MIB4 = BuildMI(MBB, I, DL, get(Mips::Move32R16),
295 Mips::SP);
296 MIB4.addReg(Reg1, RegState::Kill);
297 }
298
adjustStackPtrBigUnrestricted(unsigned SP,int64_t Amount,MachineBasicBlock & MBB,MachineBasicBlock::iterator I) const299 void Mips16InstrInfo::adjustStackPtrBigUnrestricted(
300 unsigned SP, int64_t Amount, MachineBasicBlock &MBB,
301 MachineBasicBlock::iterator I) const {
302 llvm_unreachable("adjust stack pointer amount exceeded");
303 }
304
305 /// Adjust SP by Amount bytes.
adjustStackPtr(unsigned SP,int64_t Amount,MachineBasicBlock & MBB,MachineBasicBlock::iterator I) const306 void Mips16InstrInfo::adjustStackPtr(unsigned SP, int64_t Amount,
307 MachineBasicBlock &MBB,
308 MachineBasicBlock::iterator I) const {
309 if (Amount == 0)
310 return;
311
312 if (isInt<16>(Amount)) // need to change to addiu sp, ....and isInt<16>
313 BuildAddiuSpImm(MBB, I, Amount);
314 else
315 adjustStackPtrBigUnrestricted(SP, Amount, MBB, I);
316 }
317
318 /// This function generates the sequence of instructions needed to get the
319 /// result of adding register REG and immediate IMM.
loadImmediate(unsigned FrameReg,int64_t Imm,MachineBasicBlock & MBB,MachineBasicBlock::iterator II,const DebugLoc & DL,unsigned & NewImm) const320 unsigned Mips16InstrInfo::loadImmediate(unsigned FrameReg, int64_t Imm,
321 MachineBasicBlock &MBB,
322 MachineBasicBlock::iterator II,
323 const DebugLoc &DL,
324 unsigned &NewImm) const {
325 //
326 // given original instruction is:
327 // Instr rx, T[offset] where offset is too big.
328 //
329 // lo = offset & 0xFFFF
330 // hi = ((offset >> 16) + (lo >> 15)) & 0xFFFF;
331 //
332 // let T = temporary register
333 // li T, hi
334 // shl T, 16
335 // add T, Rx, T
336 //
337 RegScavenger rs;
338 int32_t lo = Imm & 0xFFFF;
339 NewImm = lo;
340 int Reg =0;
341 int SpReg = 0;
342
343 rs.enterBasicBlockEnd(MBB);
344 rs.backward(std::next(II));
345 //
346 // We need to know which registers can be used, in the case where there
347 // are not enough free registers. We exclude all registers that
348 // are used in the instruction that we are helping.
349 // // Consider all allocatable registers in the register class initially
350 BitVector Candidates =
351 RI.getAllocatableSet
352 (*II->getParent()->getParent(), &Mips::CPU16RegsRegClass);
353 // Exclude all the registers being used by the instruction.
354 for (MachineOperand &MO : II->operands()) {
355 if (MO.isReg() && MO.getReg() != 0 && !MO.isDef() &&
356 !MO.getReg().isVirtual())
357 Candidates.reset(MO.getReg());
358 }
359
360 // If the same register was used and defined in an instruction, then
361 // it will not be in the list of candidates.
362 //
363 // we need to analyze the instruction that we are helping.
364 // we need to know if it defines register x but register x is not
365 // present as an operand of the instruction. this tells
366 // whether the register is live before the instruction. if it's not
367 // then we don't need to save it in case there are no free registers.
368 int DefReg = 0;
369 for (MachineOperand &MO : II->operands()) {
370 if (MO.isReg() && MO.isDef()) {
371 DefReg = MO.getReg();
372 break;
373 }
374 }
375
376 BitVector Available = rs.getRegsAvailable(&Mips::CPU16RegsRegClass);
377 Available &= Candidates;
378 //
379 // we use T0 for the first register, if we need to save something away.
380 // we use T1 for the second register, if we need to save something away.
381 //
382 unsigned FirstRegSaved =0, SecondRegSaved=0;
383 unsigned FirstRegSavedTo = 0, SecondRegSavedTo = 0;
384
385 Reg = Available.find_first();
386
387 if (Reg == -1) {
388 Reg = Candidates.find_first();
389 Candidates.reset(Reg);
390 if (DefReg != Reg) {
391 FirstRegSaved = Reg;
392 FirstRegSavedTo = Mips::T0;
393 copyPhysReg(MBB, II, DL, FirstRegSavedTo, FirstRegSaved, true);
394 }
395 }
396 else
397 Available.reset(Reg);
398 BuildMI(MBB, II, DL, get(Mips::LwConstant32), Reg).addImm(Imm).addImm(-1);
399 NewImm = 0;
400 if (FrameReg == Mips::SP) {
401 SpReg = Available.find_first();
402 if (SpReg == -1) {
403 SpReg = Candidates.find_first();
404 // Candidates.reset(SpReg); // not really needed
405 if (DefReg!= SpReg) {
406 SecondRegSaved = SpReg;
407 SecondRegSavedTo = Mips::T1;
408 }
409 if (SecondRegSaved)
410 copyPhysReg(MBB, II, DL, SecondRegSavedTo, SecondRegSaved, true);
411 }
412 else
413 Available.reset(SpReg);
414 copyPhysReg(MBB, II, DL, SpReg, Mips::SP, false);
415 BuildMI(MBB, II, DL, get(Mips::AdduRxRyRz16), Reg)
416 .addReg(SpReg, RegState::Kill)
417 .addReg(Reg);
418 }
419 else
420 BuildMI(MBB, II, DL, get(Mips:: AdduRxRyRz16), Reg).addReg(FrameReg)
421 .addReg(Reg, RegState::Kill);
422 if (FirstRegSaved || SecondRegSaved) {
423 II = std::next(II);
424 if (FirstRegSaved)
425 copyPhysReg(MBB, II, DL, FirstRegSaved, FirstRegSavedTo, true);
426 if (SecondRegSaved)
427 copyPhysReg(MBB, II, DL, SecondRegSaved, SecondRegSavedTo, true);
428 }
429 return Reg;
430 }
431
getAnalyzableBrOpc(unsigned Opc) const432 unsigned Mips16InstrInfo::getAnalyzableBrOpc(unsigned Opc) const {
433 return (Opc == Mips::BeqzRxImmX16 || Opc == Mips::BimmX16 ||
434 Opc == Mips::Bimm16 ||
435 Opc == Mips::Bteqz16 || Opc == Mips::Btnez16 ||
436 Opc == Mips::BeqzRxImm16 || Opc == Mips::BnezRxImm16 ||
437 Opc == Mips::BnezRxImmX16 || Opc == Mips::BteqzX16 ||
438 Opc == Mips::BteqzT8CmpX16 || Opc == Mips::BteqzT8CmpiX16 ||
439 Opc == Mips::BteqzT8SltX16 || Opc == Mips::BteqzT8SltuX16 ||
440 Opc == Mips::BteqzT8SltiX16 || Opc == Mips::BteqzT8SltiuX16 ||
441 Opc == Mips::BtnezX16 || Opc == Mips::BtnezT8CmpX16 ||
442 Opc == Mips::BtnezT8CmpiX16 || Opc == Mips::BtnezT8SltX16 ||
443 Opc == Mips::BtnezT8SltuX16 || Opc == Mips::BtnezT8SltiX16 ||
444 Opc == Mips::BtnezT8SltiuX16 ) ? Opc : 0;
445 }
446
ExpandRetRA16(MachineBasicBlock & MBB,MachineBasicBlock::iterator I,unsigned Opc) const447 void Mips16InstrInfo::ExpandRetRA16(MachineBasicBlock &MBB,
448 MachineBasicBlock::iterator I,
449 unsigned Opc) const {
450 BuildMI(MBB, I, I->getDebugLoc(), get(Opc));
451 }
452
AddiuSpImm(int64_t Imm) const453 const MCInstrDesc &Mips16InstrInfo::AddiuSpImm(int64_t Imm) const {
454 if (validSpImm8(Imm))
455 return get(Mips::AddiuSpImm16);
456 else
457 return get(Mips::AddiuSpImmX16);
458 }
459
BuildAddiuSpImm(MachineBasicBlock & MBB,MachineBasicBlock::iterator I,int64_t Imm) const460 void Mips16InstrInfo::BuildAddiuSpImm
461 (MachineBasicBlock &MBB, MachineBasicBlock::iterator I, int64_t Imm) const {
462 DebugLoc DL;
463 BuildMI(MBB, I, DL, AddiuSpImm(Imm)).addImm(Imm);
464 }
465
createMips16InstrInfo(const MipsSubtarget & STI)466 const MipsInstrInfo *llvm::createMips16InstrInfo(const MipsSubtarget &STI) {
467 return new Mips16InstrInfo(STI);
468 }
469
validImmediate(unsigned Opcode,unsigned Reg,int64_t Amount)470 bool Mips16InstrInfo::validImmediate(unsigned Opcode, unsigned Reg,
471 int64_t Amount) {
472 switch (Opcode) {
473 case Mips::LbRxRyOffMemX16:
474 case Mips::LbuRxRyOffMemX16:
475 case Mips::LhRxRyOffMemX16:
476 case Mips::LhuRxRyOffMemX16:
477 case Mips::SbRxRyOffMemX16:
478 case Mips::ShRxRyOffMemX16:
479 case Mips::LwRxRyOffMemX16:
480 case Mips::SwRxRyOffMemX16:
481 case Mips::SwRxSpImmX16:
482 case Mips::LwRxSpImmX16:
483 return isInt<16>(Amount);
484 case Mips::AddiuRxRyOffMemX16:
485 if ((Reg == Mips::PC) || (Reg == Mips::SP))
486 return isInt<16>(Amount);
487 return isInt<15>(Amount);
488 }
489 llvm_unreachable("unexpected Opcode in validImmediate");
490 }
491