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1 //===-- SIMCCodeEmitter.cpp - SI Code Emitter -----------------------------===//
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 /// \file
10 /// The SI code emitter produces machine code that can be executed
11 /// directly on the GPU device.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "AMDGPU.h"
16 #include "MCTargetDesc/AMDGPUFixupKinds.h"
17 #include "MCTargetDesc/AMDGPUMCCodeEmitter.h"
18 #include "MCTargetDesc/AMDGPUMCTargetDesc.h"
19 #include "SIDefines.h"
20 #include "Utils/AMDGPUBaseInfo.h"
21 #include "llvm/MC/MCCodeEmitter.h"
22 #include "llvm/MC/MCContext.h"
23 #include "llvm/MC/MCExpr.h"
24 #include "llvm/MC/MCFixup.h"
25 #include "llvm/MC/MCInst.h"
26 #include "llvm/MC/MCInstrDesc.h"
27 #include "llvm/MC/MCInstrInfo.h"
28 #include "llvm/MC/MCRegisterInfo.h"
29 #include "llvm/MC/MCSubtargetInfo.h"
30 #include "llvm/MC/MCSymbol.h"
31 #include "llvm/Support/Casting.h"
32 #include "llvm/Support/ErrorHandling.h"
33 #include "llvm/Support/MathExtras.h"
34 #include "llvm/Support/raw_ostream.h"
35 #include <cassert>
36 #include <cstdint>
37 #include <cstdlib>
38 
39 using namespace llvm;
40 
41 namespace {
42 
43 class SIMCCodeEmitter : public  AMDGPUMCCodeEmitter {
44   const MCRegisterInfo &MRI;
45 
46   /// Encode an fp or int literal
47   uint32_t getLitEncoding(const MCOperand &MO, const MCOperandInfo &OpInfo,
48                           const MCSubtargetInfo &STI) const;
49 
50 public:
SIMCCodeEmitter(const MCInstrInfo & mcii,const MCRegisterInfo & mri,MCContext & ctx)51   SIMCCodeEmitter(const MCInstrInfo &mcii, const MCRegisterInfo &mri,
52                   MCContext &ctx)
53       : AMDGPUMCCodeEmitter(mcii), MRI(mri) {}
54   SIMCCodeEmitter(const SIMCCodeEmitter &) = delete;
55   SIMCCodeEmitter &operator=(const SIMCCodeEmitter &) = delete;
56 
57   /// Encode the instruction and write it to the OS.
58   void encodeInstruction(const MCInst &MI, raw_ostream &OS,
59                          SmallVectorImpl<MCFixup> &Fixups,
60                          const MCSubtargetInfo &STI) const override;
61 
62   /// \returns the encoding for an MCOperand.
63   uint64_t getMachineOpValue(const MCInst &MI, const MCOperand &MO,
64                              SmallVectorImpl<MCFixup> &Fixups,
65                              const MCSubtargetInfo &STI) const override;
66 
67   /// Use a fixup to encode the simm16 field for SOPP branch
68   ///        instructions.
69   unsigned getSOPPBrEncoding(const MCInst &MI, unsigned OpNo,
70                              SmallVectorImpl<MCFixup> &Fixups,
71                              const MCSubtargetInfo &STI) const override;
72 
73   unsigned getSMEMOffsetEncoding(const MCInst &MI, unsigned OpNo,
74                                  SmallVectorImpl<MCFixup> &Fixups,
75                                  const MCSubtargetInfo &STI) const override;
76 
77   unsigned getSDWASrcEncoding(const MCInst &MI, unsigned OpNo,
78                               SmallVectorImpl<MCFixup> &Fixups,
79                               const MCSubtargetInfo &STI) const override;
80 
81   unsigned getSDWAVopcDstEncoding(const MCInst &MI, unsigned OpNo,
82                                   SmallVectorImpl<MCFixup> &Fixups,
83                                   const MCSubtargetInfo &STI) const override;
84 
85   unsigned getAVOperandEncoding(const MCInst &MI, unsigned OpNo,
86                                 SmallVectorImpl<MCFixup> &Fixups,
87                                 const MCSubtargetInfo &STI) const override;
88 };
89 
90 } // end anonymous namespace
91 
createSIMCCodeEmitter(const MCInstrInfo & MCII,const MCRegisterInfo & MRI,MCContext & Ctx)92 MCCodeEmitter *llvm::createSIMCCodeEmitter(const MCInstrInfo &MCII,
93                                            const MCRegisterInfo &MRI,
94                                            MCContext &Ctx) {
95   return new SIMCCodeEmitter(MCII, MRI, Ctx);
96 }
97 
98 // Returns the encoding value to use if the given integer is an integer inline
99 // immediate value, or 0 if it is not.
100 template <typename IntTy>
getIntInlineImmEncoding(IntTy Imm)101 static uint32_t getIntInlineImmEncoding(IntTy Imm) {
102   if (Imm >= 0 && Imm <= 64)
103     return 128 + Imm;
104 
105   if (Imm >= -16 && Imm <= -1)
106     return 192 + std::abs(Imm);
107 
108   return 0;
109 }
110 
getLit16IntEncoding(uint16_t Val,const MCSubtargetInfo & STI)111 static uint32_t getLit16IntEncoding(uint16_t Val, const MCSubtargetInfo &STI) {
112   uint16_t IntImm = getIntInlineImmEncoding(static_cast<int16_t>(Val));
113   return IntImm == 0 ? 255 : IntImm;
114 }
115 
getLit16Encoding(uint16_t Val,const MCSubtargetInfo & STI)116 static uint32_t getLit16Encoding(uint16_t Val, const MCSubtargetInfo &STI) {
117   uint16_t IntImm = getIntInlineImmEncoding(static_cast<int16_t>(Val));
118   if (IntImm != 0)
119     return IntImm;
120 
121   if (Val == 0x3800) // 0.5
122     return 240;
123 
124   if (Val == 0xB800) // -0.5
125     return 241;
126 
127   if (Val == 0x3C00) // 1.0
128     return 242;
129 
130   if (Val == 0xBC00) // -1.0
131     return 243;
132 
133   if (Val == 0x4000) // 2.0
134     return 244;
135 
136   if (Val == 0xC000) // -2.0
137     return 245;
138 
139   if (Val == 0x4400) // 4.0
140     return 246;
141 
142   if (Val == 0xC400) // -4.0
143     return 247;
144 
145   if (Val == 0x3118 && // 1.0 / (2.0 * pi)
146       STI.getFeatureBits()[AMDGPU::FeatureInv2PiInlineImm])
147     return 248;
148 
149   return 255;
150 }
151 
getLit32Encoding(uint32_t Val,const MCSubtargetInfo & STI)152 static uint32_t getLit32Encoding(uint32_t Val, const MCSubtargetInfo &STI) {
153   uint32_t IntImm = getIntInlineImmEncoding(static_cast<int32_t>(Val));
154   if (IntImm != 0)
155     return IntImm;
156 
157   if (Val == FloatToBits(0.5f))
158     return 240;
159 
160   if (Val == FloatToBits(-0.5f))
161     return 241;
162 
163   if (Val == FloatToBits(1.0f))
164     return 242;
165 
166   if (Val == FloatToBits(-1.0f))
167     return 243;
168 
169   if (Val == FloatToBits(2.0f))
170     return 244;
171 
172   if (Val == FloatToBits(-2.0f))
173     return 245;
174 
175   if (Val == FloatToBits(4.0f))
176     return 246;
177 
178   if (Val == FloatToBits(-4.0f))
179     return 247;
180 
181   if (Val == 0x3e22f983 && // 1.0 / (2.0 * pi)
182       STI.getFeatureBits()[AMDGPU::FeatureInv2PiInlineImm])
183     return 248;
184 
185   return 255;
186 }
187 
getLit64Encoding(uint64_t Val,const MCSubtargetInfo & STI)188 static uint32_t getLit64Encoding(uint64_t Val, const MCSubtargetInfo &STI) {
189   uint32_t IntImm = getIntInlineImmEncoding(static_cast<int64_t>(Val));
190   if (IntImm != 0)
191     return IntImm;
192 
193   if (Val == DoubleToBits(0.5))
194     return 240;
195 
196   if (Val == DoubleToBits(-0.5))
197     return 241;
198 
199   if (Val == DoubleToBits(1.0))
200     return 242;
201 
202   if (Val == DoubleToBits(-1.0))
203     return 243;
204 
205   if (Val == DoubleToBits(2.0))
206     return 244;
207 
208   if (Val == DoubleToBits(-2.0))
209     return 245;
210 
211   if (Val == DoubleToBits(4.0))
212     return 246;
213 
214   if (Val == DoubleToBits(-4.0))
215     return 247;
216 
217   if (Val == 0x3fc45f306dc9c882 && // 1.0 / (2.0 * pi)
218       STI.getFeatureBits()[AMDGPU::FeatureInv2PiInlineImm])
219     return 248;
220 
221   return 255;
222 }
223 
getLitEncoding(const MCOperand & MO,const MCOperandInfo & OpInfo,const MCSubtargetInfo & STI) const224 uint32_t SIMCCodeEmitter::getLitEncoding(const MCOperand &MO,
225                                          const MCOperandInfo &OpInfo,
226                                          const MCSubtargetInfo &STI) const {
227   int64_t Imm;
228   if (MO.isExpr()) {
229     const auto *C = dyn_cast<MCConstantExpr>(MO.getExpr());
230     if (!C)
231       return 255;
232 
233     Imm = C->getValue();
234   } else {
235 
236     assert(!MO.isFPImm());
237 
238     if (!MO.isImm())
239       return ~0;
240 
241     Imm = MO.getImm();
242   }
243 
244   switch (OpInfo.OperandType) {
245   case AMDGPU::OPERAND_REG_IMM_INT32:
246   case AMDGPU::OPERAND_REG_IMM_FP32:
247   case AMDGPU::OPERAND_REG_INLINE_C_INT32:
248   case AMDGPU::OPERAND_REG_INLINE_C_FP32:
249   case AMDGPU::OPERAND_REG_INLINE_AC_INT32:
250   case AMDGPU::OPERAND_REG_INLINE_AC_FP32:
251     return getLit32Encoding(static_cast<uint32_t>(Imm), STI);
252 
253   case AMDGPU::OPERAND_REG_IMM_INT64:
254   case AMDGPU::OPERAND_REG_IMM_FP64:
255   case AMDGPU::OPERAND_REG_INLINE_C_INT64:
256   case AMDGPU::OPERAND_REG_INLINE_C_FP64:
257     return getLit64Encoding(static_cast<uint64_t>(Imm), STI);
258 
259   case AMDGPU::OPERAND_REG_IMM_INT16:
260   case AMDGPU::OPERAND_REG_INLINE_C_INT16:
261   case AMDGPU::OPERAND_REG_INLINE_AC_INT16:
262     return getLit16IntEncoding(static_cast<uint16_t>(Imm), STI);
263   case AMDGPU::OPERAND_REG_IMM_FP16:
264   case AMDGPU::OPERAND_REG_INLINE_C_FP16:
265   case AMDGPU::OPERAND_REG_INLINE_AC_FP16:
266     // FIXME Is this correct? What do inline immediates do on SI for f16 src
267     // which does not have f16 support?
268     return getLit16Encoding(static_cast<uint16_t>(Imm), STI);
269   case AMDGPU::OPERAND_REG_IMM_V2INT16:
270   case AMDGPU::OPERAND_REG_IMM_V2FP16: {
271     if (!isUInt<16>(Imm) && STI.getFeatureBits()[AMDGPU::FeatureVOP3Literal])
272       return getLit32Encoding(static_cast<uint32_t>(Imm), STI);
273     if (OpInfo.OperandType == AMDGPU::OPERAND_REG_IMM_V2FP16)
274       return getLit16Encoding(static_cast<uint16_t>(Imm), STI);
275     LLVM_FALLTHROUGH;
276   }
277   case AMDGPU::OPERAND_REG_INLINE_C_V2INT16:
278   case AMDGPU::OPERAND_REG_INLINE_AC_V2INT16:
279     return getLit16IntEncoding(static_cast<uint16_t>(Imm), STI);
280   case AMDGPU::OPERAND_REG_INLINE_C_V2FP16:
281   case AMDGPU::OPERAND_REG_INLINE_AC_V2FP16: {
282     uint16_t Lo16 = static_cast<uint16_t>(Imm);
283     uint32_t Encoding = getLit16Encoding(Lo16, STI);
284     return Encoding;
285   }
286   default:
287     llvm_unreachable("invalid operand size");
288   }
289 }
290 
encodeInstruction(const MCInst & MI,raw_ostream & OS,SmallVectorImpl<MCFixup> & Fixups,const MCSubtargetInfo & STI) const291 void SIMCCodeEmitter::encodeInstruction(const MCInst &MI, raw_ostream &OS,
292                                        SmallVectorImpl<MCFixup> &Fixups,
293                                        const MCSubtargetInfo &STI) const {
294   verifyInstructionPredicates(MI,
295                               computeAvailableFeatures(STI.getFeatureBits()));
296 
297   uint64_t Encoding = getBinaryCodeForInstr(MI, Fixups, STI);
298   const MCInstrDesc &Desc = MCII.get(MI.getOpcode());
299   unsigned bytes = Desc.getSize();
300 
301   for (unsigned i = 0; i < bytes; i++) {
302     OS.write((uint8_t) ((Encoding >> (8 * i)) & 0xff));
303   }
304 
305   // NSA encoding.
306   if (AMDGPU::isGFX10Plus(STI) && Desc.TSFlags & SIInstrFlags::MIMG) {
307     int vaddr0 = AMDGPU::getNamedOperandIdx(MI.getOpcode(),
308                                             AMDGPU::OpName::vaddr0);
309     int srsrc = AMDGPU::getNamedOperandIdx(MI.getOpcode(),
310                                            AMDGPU::OpName::srsrc);
311     assert(vaddr0 >= 0 && srsrc > vaddr0);
312     unsigned NumExtraAddrs = srsrc - vaddr0 - 1;
313     unsigned NumPadding = (-NumExtraAddrs) & 3;
314 
315     for (unsigned i = 0; i < NumExtraAddrs; ++i)
316       OS.write((uint8_t)getMachineOpValue(MI, MI.getOperand(vaddr0 + 1 + i),
317                                           Fixups, STI));
318     for (unsigned i = 0; i < NumPadding; ++i)
319       OS.write(0);
320   }
321 
322   if ((bytes > 8 && STI.getFeatureBits()[AMDGPU::FeatureVOP3Literal]) ||
323       (bytes > 4 && !STI.getFeatureBits()[AMDGPU::FeatureVOP3Literal]))
324     return;
325 
326   // Check for additional literals in SRC0/1/2 (Op 1/2/3)
327   for (unsigned i = 0, e = Desc.getNumOperands(); i < e; ++i) {
328 
329     // Check if this operand should be encoded as [SV]Src
330     if (!AMDGPU::isSISrcOperand(Desc, i))
331       continue;
332 
333     // Is this operand a literal immediate?
334     const MCOperand &Op = MI.getOperand(i);
335     if (getLitEncoding(Op, Desc.OpInfo[i], STI) != 255)
336       continue;
337 
338     // Yes! Encode it
339     int64_t Imm = 0;
340 
341     if (Op.isImm())
342       Imm = Op.getImm();
343     else if (Op.isExpr()) {
344       if (const auto *C = dyn_cast<MCConstantExpr>(Op.getExpr()))
345         Imm = C->getValue();
346 
347     } else if (!Op.isExpr()) // Exprs will be replaced with a fixup value.
348       llvm_unreachable("Must be immediate or expr");
349 
350     for (unsigned j = 0; j < 4; j++) {
351       OS.write((uint8_t) ((Imm >> (8 * j)) & 0xff));
352     }
353 
354     // Only one literal value allowed
355     break;
356   }
357 }
358 
getSOPPBrEncoding(const MCInst & MI,unsigned OpNo,SmallVectorImpl<MCFixup> & Fixups,const MCSubtargetInfo & STI) const359 unsigned SIMCCodeEmitter::getSOPPBrEncoding(const MCInst &MI, unsigned OpNo,
360                                             SmallVectorImpl<MCFixup> &Fixups,
361                                             const MCSubtargetInfo &STI) const {
362   const MCOperand &MO = MI.getOperand(OpNo);
363 
364   if (MO.isExpr()) {
365     const MCExpr *Expr = MO.getExpr();
366     MCFixupKind Kind = (MCFixupKind)AMDGPU::fixup_si_sopp_br;
367     Fixups.push_back(MCFixup::create(0, Expr, Kind, MI.getLoc()));
368     return 0;
369   }
370 
371   return getMachineOpValue(MI, MO, Fixups, STI);
372 }
373 
getSMEMOffsetEncoding(const MCInst & MI,unsigned OpNo,SmallVectorImpl<MCFixup> & Fixups,const MCSubtargetInfo & STI) const374 unsigned SIMCCodeEmitter::getSMEMOffsetEncoding(const MCInst &MI, unsigned OpNo,
375                                                 SmallVectorImpl<MCFixup> &Fixups,
376                                                 const MCSubtargetInfo &STI) const {
377   auto Offset = MI.getOperand(OpNo).getImm();
378   // VI only supports 20-bit unsigned offsets.
379   assert(!AMDGPU::isVI(STI) || isUInt<20>(Offset));
380   return Offset;
381 }
382 
383 unsigned
getSDWASrcEncoding(const MCInst & MI,unsigned OpNo,SmallVectorImpl<MCFixup> & Fixups,const MCSubtargetInfo & STI) const384 SIMCCodeEmitter::getSDWASrcEncoding(const MCInst &MI, unsigned OpNo,
385                                     SmallVectorImpl<MCFixup> &Fixups,
386                                     const MCSubtargetInfo &STI) const {
387   using namespace AMDGPU::SDWA;
388 
389   uint64_t RegEnc = 0;
390 
391   const MCOperand &MO = MI.getOperand(OpNo);
392 
393   if (MO.isReg()) {
394     unsigned Reg = MO.getReg();
395     RegEnc |= MRI.getEncodingValue(Reg);
396     RegEnc &= SDWA9EncValues::SRC_VGPR_MASK;
397     if (AMDGPU::isSGPR(AMDGPU::mc2PseudoReg(Reg), &MRI)) {
398       RegEnc |= SDWA9EncValues::SRC_SGPR_MASK;
399     }
400     return RegEnc;
401   } else {
402     const MCInstrDesc &Desc = MCII.get(MI.getOpcode());
403     uint32_t Enc = getLitEncoding(MO, Desc.OpInfo[OpNo], STI);
404     if (Enc != ~0U && Enc != 255) {
405       return Enc | SDWA9EncValues::SRC_SGPR_MASK;
406     }
407   }
408 
409   llvm_unreachable("Unsupported operand kind");
410   return 0;
411 }
412 
413 unsigned
getSDWAVopcDstEncoding(const MCInst & MI,unsigned OpNo,SmallVectorImpl<MCFixup> & Fixups,const MCSubtargetInfo & STI) const414 SIMCCodeEmitter::getSDWAVopcDstEncoding(const MCInst &MI, unsigned OpNo,
415                                         SmallVectorImpl<MCFixup> &Fixups,
416                                         const MCSubtargetInfo &STI) const {
417   using namespace AMDGPU::SDWA;
418 
419   uint64_t RegEnc = 0;
420 
421   const MCOperand &MO = MI.getOperand(OpNo);
422 
423   unsigned Reg = MO.getReg();
424   if (Reg != AMDGPU::VCC && Reg != AMDGPU::VCC_LO) {
425     RegEnc |= MRI.getEncodingValue(Reg);
426     RegEnc &= SDWA9EncValues::VOPC_DST_SGPR_MASK;
427     RegEnc |= SDWA9EncValues::VOPC_DST_VCC_MASK;
428   }
429   return RegEnc;
430 }
431 
432 unsigned
getAVOperandEncoding(const MCInst & MI,unsigned OpNo,SmallVectorImpl<MCFixup> & Fixups,const MCSubtargetInfo & STI) const433 SIMCCodeEmitter::getAVOperandEncoding(const MCInst &MI, unsigned OpNo,
434                                       SmallVectorImpl<MCFixup> &Fixups,
435                                       const MCSubtargetInfo &STI) const {
436   unsigned Reg = MI.getOperand(OpNo).getReg();
437   uint64_t Enc = MRI.getEncodingValue(Reg);
438 
439   // VGPR and AGPR have the same encoding, but SrcA and SrcB operands of mfma
440   // instructions use acc[0:1] modifier bits to distinguish. These bits are
441   // encoded as a virtual 9th bit of the register for these operands.
442   if (MRI.getRegClass(AMDGPU::AGPR_32RegClassID).contains(Reg) ||
443       MRI.getRegClass(AMDGPU::AReg_64RegClassID).contains(Reg) ||
444       MRI.getRegClass(AMDGPU::AReg_96RegClassID).contains(Reg) ||
445       MRI.getRegClass(AMDGPU::AReg_128RegClassID).contains(Reg) ||
446       MRI.getRegClass(AMDGPU::AReg_160RegClassID).contains(Reg) ||
447       MRI.getRegClass(AMDGPU::AReg_192RegClassID).contains(Reg) ||
448       MRI.getRegClass(AMDGPU::AReg_256RegClassID).contains(Reg) ||
449       MRI.getRegClass(AMDGPU::AGPR_LO16RegClassID).contains(Reg))
450     Enc |= 512;
451 
452   return Enc;
453 }
454 
needsPCRel(const MCExpr * Expr)455 static bool needsPCRel(const MCExpr *Expr) {
456   switch (Expr->getKind()) {
457   case MCExpr::SymbolRef: {
458     auto *SE = cast<MCSymbolRefExpr>(Expr);
459     MCSymbolRefExpr::VariantKind Kind = SE->getKind();
460     return Kind != MCSymbolRefExpr::VK_AMDGPU_ABS32_LO &&
461            Kind != MCSymbolRefExpr::VK_AMDGPU_ABS32_HI;
462   }
463   case MCExpr::Binary: {
464     auto *BE = cast<MCBinaryExpr>(Expr);
465     if (BE->getOpcode() == MCBinaryExpr::Sub)
466       return false;
467     return needsPCRel(BE->getLHS()) || needsPCRel(BE->getRHS());
468   }
469   case MCExpr::Unary:
470     return needsPCRel(cast<MCUnaryExpr>(Expr)->getSubExpr());
471   case MCExpr::Target:
472   case MCExpr::Constant:
473     return false;
474   }
475   llvm_unreachable("invalid kind");
476 }
477 
getMachineOpValue(const MCInst & MI,const MCOperand & MO,SmallVectorImpl<MCFixup> & Fixups,const MCSubtargetInfo & STI) const478 uint64_t SIMCCodeEmitter::getMachineOpValue(const MCInst &MI,
479                                             const MCOperand &MO,
480                                        SmallVectorImpl<MCFixup> &Fixups,
481                                        const MCSubtargetInfo &STI) const {
482   if (MO.isReg())
483     return MRI.getEncodingValue(MO.getReg());
484 
485   if (MO.isExpr() && MO.getExpr()->getKind() != MCExpr::Constant) {
486     // FIXME: If this is expression is PCRel or not should not depend on what
487     // the expression looks like. Given that this is just a general expression,
488     // it should probably be FK_Data_4 and whatever is producing
489     //
490     //    s_add_u32 s2, s2, (extern_const_addrspace+16
491     //
492     // And expecting a PCRel should instead produce
493     //
494     // .Ltmp1:
495     //   s_add_u32 s2, s2, (extern_const_addrspace+16)-.Ltmp1
496     MCFixupKind Kind;
497     if (needsPCRel(MO.getExpr()))
498       Kind = FK_PCRel_4;
499     else
500       Kind = FK_Data_4;
501 
502     const MCInstrDesc &Desc = MCII.get(MI.getOpcode());
503     uint32_t Offset = Desc.getSize();
504     assert(Offset == 4 || Offset == 8);
505 
506     Fixups.push_back(
507       MCFixup::create(Offset, MO.getExpr(), Kind, MI.getLoc()));
508   }
509 
510   // Figure out the operand number, needed for isSrcOperand check
511   unsigned OpNo = 0;
512   for (unsigned e = MI.getNumOperands(); OpNo < e; ++OpNo) {
513     if (&MO == &MI.getOperand(OpNo))
514       break;
515   }
516 
517   const MCInstrDesc &Desc = MCII.get(MI.getOpcode());
518   if (AMDGPU::isSISrcOperand(Desc, OpNo)) {
519     uint32_t Enc = getLitEncoding(MO, Desc.OpInfo[OpNo], STI);
520     if (Enc != ~0U &&
521         (Enc != 255 || Desc.getSize() == 4 || Desc.getSize() == 8))
522       return Enc;
523 
524   } else if (MO.isImm())
525     return MO.getImm();
526 
527   llvm_unreachable("Encoding of this operand type is not supported yet.");
528   return 0;
529 }
530 
531 #define ENABLE_INSTR_PREDICATE_VERIFIER
532 #include "AMDGPUGenMCCodeEmitter.inc"
533