1 //===-- MipsTargetMachine.cpp - Define TargetMachine for Mips -------------===//
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 // Implements the info about Mips target spec.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "MipsTargetMachine.h"
14 #include "MCTargetDesc/MipsABIInfo.h"
15 #include "MCTargetDesc/MipsMCTargetDesc.h"
16 #include "Mips.h"
17 #include "Mips16ISelDAGToDAG.h"
18 #include "MipsMachineFunction.h"
19 #include "MipsSEISelDAGToDAG.h"
20 #include "MipsSubtarget.h"
21 #include "MipsTargetObjectFile.h"
22 #include "MipsTargetTransformInfo.h"
23 #include "TargetInfo/MipsTargetInfo.h"
24 #include "llvm/ADT/STLExtras.h"
25 #include "llvm/ADT/StringRef.h"
26 #include "llvm/Analysis/TargetTransformInfo.h"
27 #include "llvm/CodeGen/BasicTTIImpl.h"
28 #include "llvm/CodeGen/GlobalISel/CSEInfo.h"
29 #include "llvm/CodeGen/GlobalISel/IRTranslator.h"
30 #include "llvm/CodeGen/GlobalISel/InstructionSelect.h"
31 #include "llvm/CodeGen/GlobalISel/Legalizer.h"
32 #include "llvm/CodeGen/GlobalISel/RegBankSelect.h"
33 #include "llvm/CodeGen/MachineFunction.h"
34 #include "llvm/CodeGen/Passes.h"
35 #include "llvm/CodeGen/TargetPassConfig.h"
36 #include "llvm/IR/Attributes.h"
37 #include "llvm/IR/Function.h"
38 #include "llvm/InitializePasses.h"
39 #include "llvm/MC/TargetRegistry.h"
40 #include "llvm/Support/CodeGen.h"
41 #include "llvm/Support/Debug.h"
42 #include "llvm/Support/raw_ostream.h"
43 #include "llvm/Target/TargetOptions.h"
44 #include <optional>
45 #include <string>
46
47 using namespace llvm;
48
49 #define DEBUG_TYPE "mips"
50
51 static cl::opt<bool>
52 EnableMulMulFix("mfix4300", cl::init(false),
53 cl::desc("Enable the VR4300 mulmul bug fix."), cl::Hidden);
54
LLVMInitializeMipsTarget()55 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeMipsTarget() {
56 // Register the target.
57 RegisterTargetMachine<MipsebTargetMachine> X(getTheMipsTarget());
58 RegisterTargetMachine<MipselTargetMachine> Y(getTheMipselTarget());
59 RegisterTargetMachine<MipsebTargetMachine> A(getTheMips64Target());
60 RegisterTargetMachine<MipselTargetMachine> B(getTheMips64elTarget());
61
62 PassRegistry *PR = PassRegistry::getPassRegistry();
63 initializeGlobalISel(*PR);
64 initializeMipsDelaySlotFillerPass(*PR);
65 initializeMipsBranchExpansionPass(*PR);
66 initializeMicroMipsSizeReducePass(*PR);
67 initializeMipsPreLegalizerCombinerPass(*PR);
68 initializeMipsPostLegalizerCombinerPass(*PR);
69 initializeMipsMulMulBugFixPass(*PR);
70 initializeMipsDAGToDAGISelLegacyPass(*PR);
71 }
72
computeDataLayout(const Triple & TT,StringRef CPU,const TargetOptions & Options,bool isLittle)73 static std::string computeDataLayout(const Triple &TT, StringRef CPU,
74 const TargetOptions &Options,
75 bool isLittle) {
76 std::string Ret;
77 MipsABIInfo ABI = MipsABIInfo::computeTargetABI(TT, CPU, Options.MCOptions);
78
79 // There are both little and big endian mips.
80 if (isLittle)
81 Ret += "e";
82 else
83 Ret += "E";
84
85 if (ABI.IsO32())
86 Ret += "-m:m";
87 else
88 Ret += "-m:e";
89
90 // Pointers are 32 bit on some ABIs.
91 if (!ABI.IsN64())
92 Ret += "-p:32:32";
93
94 // 8 and 16 bit integers only need to have natural alignment, but try to
95 // align them to 32 bits. 64 bit integers have natural alignment.
96 Ret += "-i8:8:32-i16:16:32-i64:64";
97
98 // 32 bit registers are always available and the stack is at least 64 bit
99 // aligned. On N64 64 bit registers are also available and the stack is
100 // 128 bit aligned.
101 if (ABI.IsN64() || ABI.IsN32())
102 Ret += "-n32:64-S128";
103 else
104 Ret += "-n32-S64";
105
106 return Ret;
107 }
108
getEffectiveRelocModel(bool JIT,std::optional<Reloc::Model> RM)109 static Reloc::Model getEffectiveRelocModel(bool JIT,
110 std::optional<Reloc::Model> RM) {
111 if (!RM || JIT)
112 return Reloc::Static;
113 return *RM;
114 }
115
116 // On function prologue, the stack is created by decrementing
117 // its pointer. Once decremented, all references are done with positive
118 // offset from the stack/frame pointer, using StackGrowsUp enables
119 // an easier handling.
120 // Using CodeModel::Large enables different CALL behavior.
MipsTargetMachine(const Target & T,const Triple & TT,StringRef CPU,StringRef FS,const TargetOptions & Options,std::optional<Reloc::Model> RM,std::optional<CodeModel::Model> CM,CodeGenOptLevel OL,bool JIT,bool isLittle)121 MipsTargetMachine::MipsTargetMachine(const Target &T, const Triple &TT,
122 StringRef CPU, StringRef FS,
123 const TargetOptions &Options,
124 std::optional<Reloc::Model> RM,
125 std::optional<CodeModel::Model> CM,
126 CodeGenOptLevel OL, bool JIT,
127 bool isLittle)
128 : LLVMTargetMachine(T, computeDataLayout(TT, CPU, Options, isLittle), TT,
129 CPU, FS, Options, getEffectiveRelocModel(JIT, RM),
130 getEffectiveCodeModel(CM, CodeModel::Small), OL),
131 isLittle(isLittle), TLOF(std::make_unique<MipsTargetObjectFile>()),
132 ABI(MipsABIInfo::computeTargetABI(TT, CPU, Options.MCOptions)),
133 Subtarget(nullptr),
134 DefaultSubtarget(TT, CPU, FS, isLittle, *this, std::nullopt),
135 NoMips16Subtarget(TT, CPU, FS.empty() ? "-mips16" : FS.str() + ",-mips16",
136 isLittle, *this, std::nullopt),
137 Mips16Subtarget(TT, CPU, FS.empty() ? "+mips16" : FS.str() + ",+mips16",
138 isLittle, *this, std::nullopt) {
139 Subtarget = &DefaultSubtarget;
140 initAsmInfo();
141
142 // Mips supports the debug entry values.
143 setSupportsDebugEntryValues(true);
144 }
145
146 MipsTargetMachine::~MipsTargetMachine() = default;
147
anchor()148 void MipsebTargetMachine::anchor() {}
149
MipsebTargetMachine(const Target & T,const Triple & TT,StringRef CPU,StringRef FS,const TargetOptions & Options,std::optional<Reloc::Model> RM,std::optional<CodeModel::Model> CM,CodeGenOptLevel OL,bool JIT)150 MipsebTargetMachine::MipsebTargetMachine(const Target &T, const Triple &TT,
151 StringRef CPU, StringRef FS,
152 const TargetOptions &Options,
153 std::optional<Reloc::Model> RM,
154 std::optional<CodeModel::Model> CM,
155 CodeGenOptLevel OL, bool JIT)
156 : MipsTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, JIT, false) {}
157
anchor()158 void MipselTargetMachine::anchor() {}
159
MipselTargetMachine(const Target & T,const Triple & TT,StringRef CPU,StringRef FS,const TargetOptions & Options,std::optional<Reloc::Model> RM,std::optional<CodeModel::Model> CM,CodeGenOptLevel OL,bool JIT)160 MipselTargetMachine::MipselTargetMachine(const Target &T, const Triple &TT,
161 StringRef CPU, StringRef FS,
162 const TargetOptions &Options,
163 std::optional<Reloc::Model> RM,
164 std::optional<CodeModel::Model> CM,
165 CodeGenOptLevel OL, bool JIT)
166 : MipsTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, JIT, true) {}
167
168 const MipsSubtarget *
getSubtargetImpl(const Function & F) const169 MipsTargetMachine::getSubtargetImpl(const Function &F) const {
170 Attribute CPUAttr = F.getFnAttribute("target-cpu");
171 Attribute FSAttr = F.getFnAttribute("target-features");
172
173 std::string CPU =
174 CPUAttr.isValid() ? CPUAttr.getValueAsString().str() : TargetCPU;
175 std::string FS =
176 FSAttr.isValid() ? FSAttr.getValueAsString().str() : TargetFS;
177 bool hasMips16Attr = F.getFnAttribute("mips16").isValid();
178 bool hasNoMips16Attr = F.getFnAttribute("nomips16").isValid();
179
180 bool HasMicroMipsAttr = F.getFnAttribute("micromips").isValid();
181 bool HasNoMicroMipsAttr = F.getFnAttribute("nomicromips").isValid();
182
183 // FIXME: This is related to the code below to reset the target options,
184 // we need to know whether or not the soft float flag is set on the
185 // function, so we can enable it as a subtarget feature.
186 bool softFloat = F.getFnAttribute("use-soft-float").getValueAsBool();
187
188 if (hasMips16Attr)
189 FS += FS.empty() ? "+mips16" : ",+mips16";
190 else if (hasNoMips16Attr)
191 FS += FS.empty() ? "-mips16" : ",-mips16";
192 if (HasMicroMipsAttr)
193 FS += FS.empty() ? "+micromips" : ",+micromips";
194 else if (HasNoMicroMipsAttr)
195 FS += FS.empty() ? "-micromips" : ",-micromips";
196 if (softFloat)
197 FS += FS.empty() ? "+soft-float" : ",+soft-float";
198
199 auto &I = SubtargetMap[CPU + FS];
200 if (!I) {
201 // This needs to be done before we create a new subtarget since any
202 // creation will depend on the TM and the code generation flags on the
203 // function that reside in TargetOptions.
204 resetTargetOptions(F);
205 I = std::make_unique<MipsSubtarget>(
206 TargetTriple, CPU, FS, isLittle, *this,
207 MaybeAlign(F.getParent()->getOverrideStackAlignment()));
208 }
209 return I.get();
210 }
211
resetSubtarget(MachineFunction * MF)212 void MipsTargetMachine::resetSubtarget(MachineFunction *MF) {
213 LLVM_DEBUG(dbgs() << "resetSubtarget\n");
214
215 Subtarget = &MF->getSubtarget<MipsSubtarget>();
216 }
217
218 namespace {
219
220 /// Mips Code Generator Pass Configuration Options.
221 class MipsPassConfig : public TargetPassConfig {
222 public:
MipsPassConfig(MipsTargetMachine & TM,PassManagerBase & PM)223 MipsPassConfig(MipsTargetMachine &TM, PassManagerBase &PM)
224 : TargetPassConfig(TM, PM) {
225 // The current implementation of long branch pass requires a scratch
226 // register ($at) to be available before branch instructions. Tail merging
227 // can break this requirement, so disable it when long branch pass is
228 // enabled.
229 EnableTailMerge = !getMipsSubtarget().enableLongBranchPass();
230 }
231
getMipsTargetMachine() const232 MipsTargetMachine &getMipsTargetMachine() const {
233 return getTM<MipsTargetMachine>();
234 }
235
getMipsSubtarget() const236 const MipsSubtarget &getMipsSubtarget() const {
237 return *getMipsTargetMachine().getSubtargetImpl();
238 }
239
240 void addIRPasses() override;
241 bool addInstSelector() override;
242 void addPreEmitPass() override;
243 void addPreRegAlloc() override;
244 bool addIRTranslator() override;
245 void addPreLegalizeMachineIR() override;
246 bool addLegalizeMachineIR() override;
247 void addPreRegBankSelect() override;
248 bool addRegBankSelect() override;
249 bool addGlobalInstructionSelect() override;
250
251 std::unique_ptr<CSEConfigBase> getCSEConfig() const override;
252 };
253
254 } // end anonymous namespace
255
createPassConfig(PassManagerBase & PM)256 TargetPassConfig *MipsTargetMachine::createPassConfig(PassManagerBase &PM) {
257 return new MipsPassConfig(*this, PM);
258 }
259
getCSEConfig() const260 std::unique_ptr<CSEConfigBase> MipsPassConfig::getCSEConfig() const {
261 return getStandardCSEConfigForOpt(TM->getOptLevel());
262 }
263
addIRPasses()264 void MipsPassConfig::addIRPasses() {
265 TargetPassConfig::addIRPasses();
266 addPass(createAtomicExpandLegacyPass());
267 if (getMipsSubtarget().os16())
268 addPass(createMipsOs16Pass());
269 if (getMipsSubtarget().inMips16HardFloat())
270 addPass(createMips16HardFloatPass());
271 }
272 // Install an instruction selector pass using
273 // the ISelDag to gen Mips code.
addInstSelector()274 bool MipsPassConfig::addInstSelector() {
275 addPass(createMipsModuleISelDagPass());
276 addPass(createMips16ISelDag(getMipsTargetMachine(), getOptLevel()));
277 addPass(createMipsSEISelDag(getMipsTargetMachine(), getOptLevel()));
278 return false;
279 }
280
addPreRegAlloc()281 void MipsPassConfig::addPreRegAlloc() {
282 addPass(createMipsOptimizePICCallPass());
283 }
284
285 TargetTransformInfo
getTargetTransformInfo(const Function & F) const286 MipsTargetMachine::getTargetTransformInfo(const Function &F) const {
287 if (Subtarget->allowMixed16_32()) {
288 LLVM_DEBUG(errs() << "No Target Transform Info Pass Added\n");
289 // FIXME: This is no longer necessary as the TTI returned is per-function.
290 return TargetTransformInfo(F.getDataLayout());
291 }
292
293 LLVM_DEBUG(errs() << "Target Transform Info Pass Added\n");
294 return TargetTransformInfo(MipsTTIImpl(this, F));
295 }
296
createMachineFunctionInfo(BumpPtrAllocator & Allocator,const Function & F,const TargetSubtargetInfo * STI) const297 MachineFunctionInfo *MipsTargetMachine::createMachineFunctionInfo(
298 BumpPtrAllocator &Allocator, const Function &F,
299 const TargetSubtargetInfo *STI) const {
300 return MipsFunctionInfo::create<MipsFunctionInfo>(Allocator, F, STI);
301 }
302
303 // Implemented by targets that want to run passes immediately before
304 // machine code is emitted.
addPreEmitPass()305 void MipsPassConfig::addPreEmitPass() {
306 // Expand pseudo instructions that are sensitive to register allocation.
307 addPass(createMipsExpandPseudoPass());
308
309 // The microMIPS size reduction pass performs instruction reselection for
310 // instructions which can be remapped to a 16 bit instruction.
311 addPass(createMicroMipsSizeReducePass());
312
313 // This pass inserts a nop instruction between two back-to-back multiplication
314 // instructions when the "mfix4300" flag is passed.
315 if (EnableMulMulFix)
316 addPass(createMipsMulMulBugPass());
317
318 // The delay slot filler pass can potientially create forbidden slot hazards
319 // for MIPSR6 and therefore it should go before MipsBranchExpansion pass.
320 addPass(createMipsDelaySlotFillerPass());
321
322 // This pass expands branches and takes care about the forbidden slot hazards.
323 // Expanding branches may potentially create forbidden slot hazards for
324 // MIPSR6, and fixing such hazard may potentially break a branch by extending
325 // its offset out of range. That's why this pass combine these two tasks, and
326 // runs them alternately until one of them finishes without any changes. Only
327 // then we can be sure that all branches are expanded properly and no hazards
328 // exists.
329 // Any new pass should go before this pass.
330 addPass(createMipsBranchExpansion());
331
332 addPass(createMipsConstantIslandPass());
333 }
334
addIRTranslator()335 bool MipsPassConfig::addIRTranslator() {
336 addPass(new IRTranslator(getOptLevel()));
337 return false;
338 }
339
addPreLegalizeMachineIR()340 void MipsPassConfig::addPreLegalizeMachineIR() {
341 addPass(createMipsPreLegalizeCombiner());
342 }
343
addLegalizeMachineIR()344 bool MipsPassConfig::addLegalizeMachineIR() {
345 addPass(new Legalizer());
346 return false;
347 }
348
addPreRegBankSelect()349 void MipsPassConfig::addPreRegBankSelect() {
350 bool IsOptNone = getOptLevel() == CodeGenOptLevel::None;
351 addPass(createMipsPostLegalizeCombiner(IsOptNone));
352 }
353
addRegBankSelect()354 bool MipsPassConfig::addRegBankSelect() {
355 addPass(new RegBankSelect());
356 return false;
357 }
358
addGlobalInstructionSelect()359 bool MipsPassConfig::addGlobalInstructionSelect() {
360 addPass(new InstructionSelect(getOptLevel()));
361 return false;
362 }
363