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1 //===- ARMLegalizerInfo.cpp --------------------------------------*- C++ -*-==//
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 /// \file
9 /// This file implements the targeting of the Machinelegalizer class for ARM.
10 /// \todo This should be generated by TableGen.
11 //===----------------------------------------------------------------------===//
12 
13 #include "ARMLegalizerInfo.h"
14 #include "ARMCallLowering.h"
15 #include "ARMSubtarget.h"
16 #include "llvm/CodeGen/GlobalISel/LegalizerHelper.h"
17 #include "llvm/CodeGen/LowLevelType.h"
18 #include "llvm/CodeGen/MachineRegisterInfo.h"
19 #include "llvm/CodeGen/TargetOpcodes.h"
20 #include "llvm/CodeGen/ValueTypes.h"
21 #include "llvm/IR/DerivedTypes.h"
22 #include "llvm/IR/Type.h"
23 
24 using namespace llvm;
25 using namespace LegalizeActions;
26 
27 /// FIXME: The following static functions are SizeChangeStrategy functions
28 /// that are meant to temporarily mimic the behaviour of the old legalization
29 /// based on doubling/halving non-legal types as closely as possible. This is
30 /// not entirly possible as only legalizing the types that are exactly a power
31 /// of 2 times the size of the legal types would require specifying all those
32 /// sizes explicitly.
33 /// In practice, not specifying those isn't a problem, and the below functions
34 /// should disappear quickly as we add support for legalizing non-power-of-2
35 /// sized types further.
36 static void
addAndInterleaveWithUnsupported(LegalizerInfo::SizeAndActionsVec & result,const LegalizerInfo::SizeAndActionsVec & v)37 addAndInterleaveWithUnsupported(LegalizerInfo::SizeAndActionsVec &result,
38                                 const LegalizerInfo::SizeAndActionsVec &v) {
39   for (unsigned i = 0; i < v.size(); ++i) {
40     result.push_back(v[i]);
41     if (i + 1 < v[i].first && i + 1 < v.size() &&
42         v[i + 1].first != v[i].first + 1)
43       result.push_back({v[i].first + 1, Unsupported});
44   }
45 }
46 
47 static LegalizerInfo::SizeAndActionsVec
widen_8_16(const LegalizerInfo::SizeAndActionsVec & v)48 widen_8_16(const LegalizerInfo::SizeAndActionsVec &v) {
49   assert(v.size() >= 1);
50   assert(v[0].first > 17);
51   LegalizerInfo::SizeAndActionsVec result = {{1, Unsupported},
52                                              {8, WidenScalar},
53                                              {9, Unsupported},
54                                              {16, WidenScalar},
55                                              {17, Unsupported}};
56   addAndInterleaveWithUnsupported(result, v);
57   auto Largest = result.back().first;
58   result.push_back({Largest + 1, Unsupported});
59   return result;
60 }
61 
AEABI(const ARMSubtarget & ST)62 static bool AEABI(const ARMSubtarget &ST) {
63   return ST.isTargetAEABI() || ST.isTargetGNUAEABI() || ST.isTargetMuslAEABI();
64 }
65 
ARMLegalizerInfo(const ARMSubtarget & ST)66 ARMLegalizerInfo::ARMLegalizerInfo(const ARMSubtarget &ST) {
67   using namespace TargetOpcode;
68 
69   const LLT p0 = LLT::pointer(0, 32);
70 
71   const LLT s1 = LLT::scalar(1);
72   const LLT s8 = LLT::scalar(8);
73   const LLT s16 = LLT::scalar(16);
74   const LLT s32 = LLT::scalar(32);
75   const LLT s64 = LLT::scalar(64);
76 
77   if (ST.isThumb1Only()) {
78     // Thumb1 is not supported yet.
79     computeTables();
80     verify(*ST.getInstrInfo());
81     return;
82   }
83 
84   getActionDefinitionsBuilder({G_SEXT, G_ZEXT, G_ANYEXT})
85       .legalForCartesianProduct({s8, s16, s32}, {s1, s8, s16});
86 
87   getActionDefinitionsBuilder(G_SEXT_INREG).lower();
88 
89   getActionDefinitionsBuilder({G_MUL, G_AND, G_OR, G_XOR})
90       .legalFor({s32})
91       .clampScalar(0, s32, s32);
92 
93   if (ST.hasNEON())
94     getActionDefinitionsBuilder({G_ADD, G_SUB})
95         .legalFor({s32, s64})
96         .minScalar(0, s32);
97   else
98     getActionDefinitionsBuilder({G_ADD, G_SUB})
99         .legalFor({s32})
100         .minScalar(0, s32);
101 
102   getActionDefinitionsBuilder({G_ASHR, G_LSHR, G_SHL})
103     .legalFor({{s32, s32}})
104     .minScalar(0, s32)
105     .clampScalar(1, s32, s32);
106 
107   bool HasHWDivide = (!ST.isThumb() && ST.hasDivideInARMMode()) ||
108                      (ST.isThumb() && ST.hasDivideInThumbMode());
109   if (HasHWDivide)
110     getActionDefinitionsBuilder({G_SDIV, G_UDIV})
111         .legalFor({s32})
112         .clampScalar(0, s32, s32);
113   else
114     getActionDefinitionsBuilder({G_SDIV, G_UDIV})
115         .libcallFor({s32})
116         .clampScalar(0, s32, s32);
117 
118   for (unsigned Op : {G_SREM, G_UREM}) {
119     setLegalizeScalarToDifferentSizeStrategy(Op, 0, widen_8_16);
120     if (HasHWDivide)
121       setAction({Op, s32}, Lower);
122     else if (AEABI(ST))
123       setAction({Op, s32}, Custom);
124     else
125       setAction({Op, s32}, Libcall);
126   }
127 
128   getActionDefinitionsBuilder(G_INTTOPTR)
129       .legalFor({{p0, s32}})
130       .minScalar(1, s32);
131   getActionDefinitionsBuilder(G_PTRTOINT)
132       .legalFor({{s32, p0}})
133       .minScalar(0, s32);
134 
135   getActionDefinitionsBuilder(G_CONSTANT)
136       .legalFor({s32, p0})
137       .clampScalar(0, s32, s32);
138 
139   getActionDefinitionsBuilder(G_ICMP)
140       .legalForCartesianProduct({s1}, {s32, p0})
141       .minScalar(1, s32);
142 
143   getActionDefinitionsBuilder(G_SELECT)
144       .legalForCartesianProduct({s32, p0}, {s1})
145       .minScalar(0, s32);
146 
147   // We're keeping these builders around because we'll want to add support for
148   // floating point to them.
149   auto &LoadStoreBuilder = getActionDefinitionsBuilder({G_LOAD, G_STORE})
150                                .legalForTypesWithMemDesc({{s1, p0, 8, 8},
151                                                           {s8, p0, 8, 8},
152                                                           {s16, p0, 16, 8},
153                                                           {s32, p0, 32, 8},
154                                                           {p0, p0, 32, 8}})
155                                .unsupportedIfMemSizeNotPow2();
156 
157   getActionDefinitionsBuilder(G_FRAME_INDEX).legalFor({p0});
158   getActionDefinitionsBuilder(G_GLOBAL_VALUE).legalFor({p0});
159 
160   auto &PhiBuilder =
161       getActionDefinitionsBuilder(G_PHI)
162           .legalFor({s32, p0})
163           .minScalar(0, s32);
164 
165   getActionDefinitionsBuilder(G_PTR_ADD)
166       .legalFor({{p0, s32}})
167       .minScalar(1, s32);
168 
169   getActionDefinitionsBuilder(G_BRCOND).legalFor({s1});
170 
171   if (!ST.useSoftFloat() && ST.hasVFP2Base()) {
172     getActionDefinitionsBuilder(
173         {G_FADD, G_FSUB, G_FMUL, G_FDIV, G_FCONSTANT, G_FNEG})
174         .legalFor({s32, s64});
175 
176     LoadStoreBuilder
177         .legalForTypesWithMemDesc({{s64, p0, 64, 32}})
178         .maxScalar(0, s32);
179     PhiBuilder.legalFor({s64});
180 
181     getActionDefinitionsBuilder(G_FCMP).legalForCartesianProduct({s1},
182                                                                  {s32, s64});
183 
184     getActionDefinitionsBuilder(G_MERGE_VALUES).legalFor({{s64, s32}});
185     getActionDefinitionsBuilder(G_UNMERGE_VALUES).legalFor({{s32, s64}});
186 
187     getActionDefinitionsBuilder(G_FPEXT).legalFor({{s64, s32}});
188     getActionDefinitionsBuilder(G_FPTRUNC).legalFor({{s32, s64}});
189 
190     getActionDefinitionsBuilder({G_FPTOSI, G_FPTOUI})
191         .legalForCartesianProduct({s32}, {s32, s64});
192     getActionDefinitionsBuilder({G_SITOFP, G_UITOFP})
193         .legalForCartesianProduct({s32, s64}, {s32});
194   } else {
195     getActionDefinitionsBuilder({G_FADD, G_FSUB, G_FMUL, G_FDIV})
196         .libcallFor({s32, s64});
197 
198     LoadStoreBuilder.maxScalar(0, s32);
199 
200     for (auto Ty : {s32, s64})
201       setAction({G_FNEG, Ty}, Lower);
202 
203     getActionDefinitionsBuilder(G_FCONSTANT).customFor({s32, s64});
204 
205     getActionDefinitionsBuilder(G_FCMP).customForCartesianProduct({s1},
206                                                                   {s32, s64});
207 
208     if (AEABI(ST))
209       setFCmpLibcallsAEABI();
210     else
211       setFCmpLibcallsGNU();
212 
213     getActionDefinitionsBuilder(G_FPEXT).libcallFor({{s64, s32}});
214     getActionDefinitionsBuilder(G_FPTRUNC).libcallFor({{s32, s64}});
215 
216     getActionDefinitionsBuilder({G_FPTOSI, G_FPTOUI})
217         .libcallForCartesianProduct({s32}, {s32, s64});
218     getActionDefinitionsBuilder({G_SITOFP, G_UITOFP})
219         .libcallForCartesianProduct({s32, s64}, {s32});
220   }
221 
222   if (!ST.useSoftFloat() && ST.hasVFP4Base())
223     getActionDefinitionsBuilder(G_FMA).legalFor({s32, s64});
224   else
225     getActionDefinitionsBuilder(G_FMA).libcallFor({s32, s64});
226 
227   getActionDefinitionsBuilder({G_FREM, G_FPOW}).libcallFor({s32, s64});
228 
229   if (ST.hasV5TOps()) {
230     getActionDefinitionsBuilder(G_CTLZ)
231         .legalFor({s32, s32})
232         .clampScalar(1, s32, s32)
233         .clampScalar(0, s32, s32);
234     getActionDefinitionsBuilder(G_CTLZ_ZERO_UNDEF)
235         .lowerFor({s32, s32})
236         .clampScalar(1, s32, s32)
237         .clampScalar(0, s32, s32);
238   } else {
239     getActionDefinitionsBuilder(G_CTLZ_ZERO_UNDEF)
240         .libcallFor({s32, s32})
241         .clampScalar(1, s32, s32)
242         .clampScalar(0, s32, s32);
243     getActionDefinitionsBuilder(G_CTLZ)
244         .lowerFor({s32, s32})
245         .clampScalar(1, s32, s32)
246         .clampScalar(0, s32, s32);
247   }
248 
249   computeTables();
250   verify(*ST.getInstrInfo());
251 }
252 
setFCmpLibcallsAEABI()253 void ARMLegalizerInfo::setFCmpLibcallsAEABI() {
254   // FCMP_TRUE and FCMP_FALSE don't need libcalls, they should be
255   // default-initialized.
256   FCmp32Libcalls.resize(CmpInst::LAST_FCMP_PREDICATE + 1);
257   FCmp32Libcalls[CmpInst::FCMP_OEQ] = {
258       {RTLIB::OEQ_F32, CmpInst::BAD_ICMP_PREDICATE}};
259   FCmp32Libcalls[CmpInst::FCMP_OGE] = {
260       {RTLIB::OGE_F32, CmpInst::BAD_ICMP_PREDICATE}};
261   FCmp32Libcalls[CmpInst::FCMP_OGT] = {
262       {RTLIB::OGT_F32, CmpInst::BAD_ICMP_PREDICATE}};
263   FCmp32Libcalls[CmpInst::FCMP_OLE] = {
264       {RTLIB::OLE_F32, CmpInst::BAD_ICMP_PREDICATE}};
265   FCmp32Libcalls[CmpInst::FCMP_OLT] = {
266       {RTLIB::OLT_F32, CmpInst::BAD_ICMP_PREDICATE}};
267   FCmp32Libcalls[CmpInst::FCMP_ORD] = {{RTLIB::UO_F32, CmpInst::ICMP_EQ}};
268   FCmp32Libcalls[CmpInst::FCMP_UGE] = {{RTLIB::OLT_F32, CmpInst::ICMP_EQ}};
269   FCmp32Libcalls[CmpInst::FCMP_UGT] = {{RTLIB::OLE_F32, CmpInst::ICMP_EQ}};
270   FCmp32Libcalls[CmpInst::FCMP_ULE] = {{RTLIB::OGT_F32, CmpInst::ICMP_EQ}};
271   FCmp32Libcalls[CmpInst::FCMP_ULT] = {{RTLIB::OGE_F32, CmpInst::ICMP_EQ}};
272   FCmp32Libcalls[CmpInst::FCMP_UNE] = {{RTLIB::UNE_F32, CmpInst::ICMP_EQ}};
273   FCmp32Libcalls[CmpInst::FCMP_UNO] = {
274       {RTLIB::UO_F32, CmpInst::BAD_ICMP_PREDICATE}};
275   FCmp32Libcalls[CmpInst::FCMP_ONE] = {
276       {RTLIB::OGT_F32, CmpInst::BAD_ICMP_PREDICATE},
277       {RTLIB::OLT_F32, CmpInst::BAD_ICMP_PREDICATE}};
278   FCmp32Libcalls[CmpInst::FCMP_UEQ] = {
279       {RTLIB::OEQ_F32, CmpInst::BAD_ICMP_PREDICATE},
280       {RTLIB::UO_F32, CmpInst::BAD_ICMP_PREDICATE}};
281 
282   FCmp64Libcalls.resize(CmpInst::LAST_FCMP_PREDICATE + 1);
283   FCmp64Libcalls[CmpInst::FCMP_OEQ] = {
284       {RTLIB::OEQ_F64, CmpInst::BAD_ICMP_PREDICATE}};
285   FCmp64Libcalls[CmpInst::FCMP_OGE] = {
286       {RTLIB::OGE_F64, CmpInst::BAD_ICMP_PREDICATE}};
287   FCmp64Libcalls[CmpInst::FCMP_OGT] = {
288       {RTLIB::OGT_F64, CmpInst::BAD_ICMP_PREDICATE}};
289   FCmp64Libcalls[CmpInst::FCMP_OLE] = {
290       {RTLIB::OLE_F64, CmpInst::BAD_ICMP_PREDICATE}};
291   FCmp64Libcalls[CmpInst::FCMP_OLT] = {
292       {RTLIB::OLT_F64, CmpInst::BAD_ICMP_PREDICATE}};
293   FCmp64Libcalls[CmpInst::FCMP_ORD] = {{RTLIB::UO_F64, CmpInst::ICMP_EQ}};
294   FCmp64Libcalls[CmpInst::FCMP_UGE] = {{RTLIB::OLT_F64, CmpInst::ICMP_EQ}};
295   FCmp64Libcalls[CmpInst::FCMP_UGT] = {{RTLIB::OLE_F64, CmpInst::ICMP_EQ}};
296   FCmp64Libcalls[CmpInst::FCMP_ULE] = {{RTLIB::OGT_F64, CmpInst::ICMP_EQ}};
297   FCmp64Libcalls[CmpInst::FCMP_ULT] = {{RTLIB::OGE_F64, CmpInst::ICMP_EQ}};
298   FCmp64Libcalls[CmpInst::FCMP_UNE] = {{RTLIB::UNE_F64, CmpInst::ICMP_EQ}};
299   FCmp64Libcalls[CmpInst::FCMP_UNO] = {
300       {RTLIB::UO_F64, CmpInst::BAD_ICMP_PREDICATE}};
301   FCmp64Libcalls[CmpInst::FCMP_ONE] = {
302       {RTLIB::OGT_F64, CmpInst::BAD_ICMP_PREDICATE},
303       {RTLIB::OLT_F64, CmpInst::BAD_ICMP_PREDICATE}};
304   FCmp64Libcalls[CmpInst::FCMP_UEQ] = {
305       {RTLIB::OEQ_F64, CmpInst::BAD_ICMP_PREDICATE},
306       {RTLIB::UO_F64, CmpInst::BAD_ICMP_PREDICATE}};
307 }
308 
setFCmpLibcallsGNU()309 void ARMLegalizerInfo::setFCmpLibcallsGNU() {
310   // FCMP_TRUE and FCMP_FALSE don't need libcalls, they should be
311   // default-initialized.
312   FCmp32Libcalls.resize(CmpInst::LAST_FCMP_PREDICATE + 1);
313   FCmp32Libcalls[CmpInst::FCMP_OEQ] = {{RTLIB::OEQ_F32, CmpInst::ICMP_EQ}};
314   FCmp32Libcalls[CmpInst::FCMP_OGE] = {{RTLIB::OGE_F32, CmpInst::ICMP_SGE}};
315   FCmp32Libcalls[CmpInst::FCMP_OGT] = {{RTLIB::OGT_F32, CmpInst::ICMP_SGT}};
316   FCmp32Libcalls[CmpInst::FCMP_OLE] = {{RTLIB::OLE_F32, CmpInst::ICMP_SLE}};
317   FCmp32Libcalls[CmpInst::FCMP_OLT] = {{RTLIB::OLT_F32, CmpInst::ICMP_SLT}};
318   FCmp32Libcalls[CmpInst::FCMP_ORD] = {{RTLIB::UO_F32, CmpInst::ICMP_EQ}};
319   FCmp32Libcalls[CmpInst::FCMP_UGE] = {{RTLIB::OLT_F32, CmpInst::ICMP_SGE}};
320   FCmp32Libcalls[CmpInst::FCMP_UGT] = {{RTLIB::OLE_F32, CmpInst::ICMP_SGT}};
321   FCmp32Libcalls[CmpInst::FCMP_ULE] = {{RTLIB::OGT_F32, CmpInst::ICMP_SLE}};
322   FCmp32Libcalls[CmpInst::FCMP_ULT] = {{RTLIB::OGE_F32, CmpInst::ICMP_SLT}};
323   FCmp32Libcalls[CmpInst::FCMP_UNE] = {{RTLIB::UNE_F32, CmpInst::ICMP_NE}};
324   FCmp32Libcalls[CmpInst::FCMP_UNO] = {{RTLIB::UO_F32, CmpInst::ICMP_NE}};
325   FCmp32Libcalls[CmpInst::FCMP_ONE] = {{RTLIB::OGT_F32, CmpInst::ICMP_SGT},
326                                        {RTLIB::OLT_F32, CmpInst::ICMP_SLT}};
327   FCmp32Libcalls[CmpInst::FCMP_UEQ] = {{RTLIB::OEQ_F32, CmpInst::ICMP_EQ},
328                                        {RTLIB::UO_F32, CmpInst::ICMP_NE}};
329 
330   FCmp64Libcalls.resize(CmpInst::LAST_FCMP_PREDICATE + 1);
331   FCmp64Libcalls[CmpInst::FCMP_OEQ] = {{RTLIB::OEQ_F64, CmpInst::ICMP_EQ}};
332   FCmp64Libcalls[CmpInst::FCMP_OGE] = {{RTLIB::OGE_F64, CmpInst::ICMP_SGE}};
333   FCmp64Libcalls[CmpInst::FCMP_OGT] = {{RTLIB::OGT_F64, CmpInst::ICMP_SGT}};
334   FCmp64Libcalls[CmpInst::FCMP_OLE] = {{RTLIB::OLE_F64, CmpInst::ICMP_SLE}};
335   FCmp64Libcalls[CmpInst::FCMP_OLT] = {{RTLIB::OLT_F64, CmpInst::ICMP_SLT}};
336   FCmp64Libcalls[CmpInst::FCMP_ORD] = {{RTLIB::UO_F64, CmpInst::ICMP_EQ}};
337   FCmp64Libcalls[CmpInst::FCMP_UGE] = {{RTLIB::OLT_F64, CmpInst::ICMP_SGE}};
338   FCmp64Libcalls[CmpInst::FCMP_UGT] = {{RTLIB::OLE_F64, CmpInst::ICMP_SGT}};
339   FCmp64Libcalls[CmpInst::FCMP_ULE] = {{RTLIB::OGT_F64, CmpInst::ICMP_SLE}};
340   FCmp64Libcalls[CmpInst::FCMP_ULT] = {{RTLIB::OGE_F64, CmpInst::ICMP_SLT}};
341   FCmp64Libcalls[CmpInst::FCMP_UNE] = {{RTLIB::UNE_F64, CmpInst::ICMP_NE}};
342   FCmp64Libcalls[CmpInst::FCMP_UNO] = {{RTLIB::UO_F64, CmpInst::ICMP_NE}};
343   FCmp64Libcalls[CmpInst::FCMP_ONE] = {{RTLIB::OGT_F64, CmpInst::ICMP_SGT},
344                                        {RTLIB::OLT_F64, CmpInst::ICMP_SLT}};
345   FCmp64Libcalls[CmpInst::FCMP_UEQ] = {{RTLIB::OEQ_F64, CmpInst::ICMP_EQ},
346                                        {RTLIB::UO_F64, CmpInst::ICMP_NE}};
347 }
348 
349 ARMLegalizerInfo::FCmpLibcallsList
getFCmpLibcalls(CmpInst::Predicate Predicate,unsigned Size) const350 ARMLegalizerInfo::getFCmpLibcalls(CmpInst::Predicate Predicate,
351                                   unsigned Size) const {
352   assert(CmpInst::isFPPredicate(Predicate) && "Unsupported FCmp predicate");
353   if (Size == 32)
354     return FCmp32Libcalls[Predicate];
355   if (Size == 64)
356     return FCmp64Libcalls[Predicate];
357   llvm_unreachable("Unsupported size for FCmp predicate");
358 }
359 
legalizeCustom(LegalizerHelper & Helper,MachineInstr & MI) const360 bool ARMLegalizerInfo::legalizeCustom(LegalizerHelper &Helper,
361                                       MachineInstr &MI) const {
362   using namespace TargetOpcode;
363 
364   MachineIRBuilder &MIRBuilder = Helper.MIRBuilder;
365   MachineRegisterInfo &MRI = *MIRBuilder.getMRI();
366   LLVMContext &Ctx = MIRBuilder.getMF().getFunction().getContext();
367 
368   switch (MI.getOpcode()) {
369   default:
370     return false;
371   case G_SREM:
372   case G_UREM: {
373     Register OriginalResult = MI.getOperand(0).getReg();
374     auto Size = MRI.getType(OriginalResult).getSizeInBits();
375     if (Size != 32)
376       return false;
377 
378     auto Libcall =
379         MI.getOpcode() == G_SREM ? RTLIB::SDIVREM_I32 : RTLIB::UDIVREM_I32;
380 
381     // Our divmod libcalls return a struct containing the quotient and the
382     // remainder. Create a new, unused register for the quotient and use the
383     // destination of the original instruction for the remainder.
384     Type *ArgTy = Type::getInt32Ty(Ctx);
385     StructType *RetTy = StructType::get(Ctx, {ArgTy, ArgTy}, /* Packed */ true);
386     Register RetRegs[] = {MRI.createGenericVirtualRegister(LLT::scalar(32)),
387                           OriginalResult};
388     auto Status = createLibcall(MIRBuilder, Libcall, {RetRegs, RetTy},
389                                 {{MI.getOperand(1).getReg(), ArgTy},
390                                  {MI.getOperand(2).getReg(), ArgTy}});
391     if (Status != LegalizerHelper::Legalized)
392       return false;
393     break;
394   }
395   case G_FCMP: {
396     assert(MRI.getType(MI.getOperand(2).getReg()) ==
397                MRI.getType(MI.getOperand(3).getReg()) &&
398            "Mismatched operands for G_FCMP");
399     auto OpSize = MRI.getType(MI.getOperand(2).getReg()).getSizeInBits();
400 
401     auto OriginalResult = MI.getOperand(0).getReg();
402     auto Predicate =
403         static_cast<CmpInst::Predicate>(MI.getOperand(1).getPredicate());
404     auto Libcalls = getFCmpLibcalls(Predicate, OpSize);
405 
406     if (Libcalls.empty()) {
407       assert((Predicate == CmpInst::FCMP_TRUE ||
408               Predicate == CmpInst::FCMP_FALSE) &&
409              "Predicate needs libcalls, but none specified");
410       MIRBuilder.buildConstant(OriginalResult,
411                                Predicate == CmpInst::FCMP_TRUE ? 1 : 0);
412       MI.eraseFromParent();
413       return true;
414     }
415 
416     assert((OpSize == 32 || OpSize == 64) && "Unsupported operand size");
417     auto *ArgTy = OpSize == 32 ? Type::getFloatTy(Ctx) : Type::getDoubleTy(Ctx);
418     auto *RetTy = Type::getInt32Ty(Ctx);
419 
420     SmallVector<Register, 2> Results;
421     for (auto Libcall : Libcalls) {
422       auto LibcallResult = MRI.createGenericVirtualRegister(LLT::scalar(32));
423       auto Status =
424           createLibcall(MIRBuilder, Libcall.LibcallID, {LibcallResult, RetTy},
425                         {{MI.getOperand(2).getReg(), ArgTy},
426                          {MI.getOperand(3).getReg(), ArgTy}});
427 
428       if (Status != LegalizerHelper::Legalized)
429         return false;
430 
431       auto ProcessedResult =
432           Libcalls.size() == 1
433               ? OriginalResult
434               : MRI.createGenericVirtualRegister(MRI.getType(OriginalResult));
435 
436       // We have a result, but we need to transform it into a proper 1-bit 0 or
437       // 1, taking into account the different peculiarities of the values
438       // returned by the comparison functions.
439       CmpInst::Predicate ResultPred = Libcall.Predicate;
440       if (ResultPred == CmpInst::BAD_ICMP_PREDICATE) {
441         // We have a nice 0 or 1, and we just need to truncate it back to 1 bit
442         // to keep the types consistent.
443         MIRBuilder.buildTrunc(ProcessedResult, LibcallResult);
444       } else {
445         // We need to compare against 0.
446         assert(CmpInst::isIntPredicate(ResultPred) && "Unsupported predicate");
447         auto Zero = MIRBuilder.buildConstant(LLT::scalar(32), 0);
448         MIRBuilder.buildICmp(ResultPred, ProcessedResult, LibcallResult, Zero);
449       }
450       Results.push_back(ProcessedResult);
451     }
452 
453     if (Results.size() != 1) {
454       assert(Results.size() == 2 && "Unexpected number of results");
455       MIRBuilder.buildOr(OriginalResult, Results[0], Results[1]);
456     }
457     break;
458   }
459   case G_FCONSTANT: {
460     // Convert to integer constants, while preserving the binary representation.
461     auto AsInteger =
462         MI.getOperand(1).getFPImm()->getValueAPF().bitcastToAPInt();
463     MIRBuilder.buildConstant(MI.getOperand(0),
464                              *ConstantInt::get(Ctx, AsInteger));
465     break;
466   }
467   }
468 
469   MI.eraseFromParent();
470   return true;
471 }
472