1 //===-- MipsTargetMachine.cpp - Define TargetMachine for Mips -------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Implements the info about Mips target spec.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "MipsTargetMachine.h"
15 #include "MCTargetDesc/MipsABIInfo.h"
16 #include "MCTargetDesc/MipsMCTargetDesc.h"
17 #include "Mips.h"
18 #include "Mips16ISelDAGToDAG.h"
19 #include "MipsSEISelDAGToDAG.h"
20 #include "MipsSubtarget.h"
21 #include "MipsTargetObjectFile.h"
22 #include "llvm/ADT/Optional.h"
23 #include "llvm/ADT/STLExtras.h"
24 #include "llvm/ADT/StringRef.h"
25 #include "llvm/Analysis/TargetTransformInfo.h"
26 #include "llvm/CodeGen/BasicTTIImpl.h"
27 #include "llvm/CodeGen/MachineFunction.h"
28 #include "llvm/CodeGen/Passes.h"
29 #include "llvm/CodeGen/TargetPassConfig.h"
30 #include "llvm/IR/Attributes.h"
31 #include "llvm/IR/Function.h"
32 #include "llvm/Support/CodeGen.h"
33 #include "llvm/Support/Debug.h"
34 #include "llvm/Support/TargetRegistry.h"
35 #include "llvm/Support/raw_ostream.h"
36 #include "llvm/Target/TargetOptions.h"
37 #include <string>
38 
39 using namespace llvm;
40 
41 #define DEBUG_TYPE "mips"
42 
43 extern "C" void LLVMInitializeMipsTarget() {
44   // Register the target.
45   RegisterTargetMachine<MipsebTargetMachine> X(getTheMipsTarget());
46   RegisterTargetMachine<MipselTargetMachine> Y(getTheMipselTarget());
47   RegisterTargetMachine<MipsebTargetMachine> A(getTheMips64Target());
48   RegisterTargetMachine<MipselTargetMachine> B(getTheMips64elTarget());
49 }
50 
51 static std::string computeDataLayout(const Triple &TT, StringRef CPU,
52                                      const TargetOptions &Options,
53                                      bool isLittle) {
54   std::string Ret;
55   MipsABIInfo ABI = MipsABIInfo::computeTargetABI(TT, CPU, Options.MCOptions);
56 
57   // There are both little and big endian mips.
58   if (isLittle)
59     Ret += "e";
60   else
61     Ret += "E";
62 
63   if (ABI.IsO32())
64     Ret += "-m:m";
65   else
66     Ret += "-m:e";
67 
68   // Pointers are 32 bit on some ABIs.
69   if (!ABI.IsN64())
70     Ret += "-p:32:32";
71 
72   // 8 and 16 bit integers only need to have natural alignment, but try to
73   // align them to 32 bits. 64 bit integers have natural alignment.
74   Ret += "-i8:8:32-i16:16:32-i64:64";
75 
76   // 32 bit registers are always available and the stack is at least 64 bit
77   // aligned. On N64 64 bit registers are also available and the stack is
78   // 128 bit aligned.
79   if (ABI.IsN64() || ABI.IsN32())
80     Ret += "-n32:64-S128";
81   else
82     Ret += "-n32-S64";
83 
84   return Ret;
85 }
86 
87 static Reloc::Model getEffectiveRelocModel(CodeModel::Model CM,
88                                            Optional<Reloc::Model> RM) {
89   if (!RM.hasValue() || CM == CodeModel::JITDefault)
90     return Reloc::Static;
91   return *RM;
92 }
93 
94 // On function prologue, the stack is created by decrementing
95 // its pointer. Once decremented, all references are done with positive
96 // offset from the stack/frame pointer, using StackGrowsUp enables
97 // an easier handling.
98 // Using CodeModel::Large enables different CALL behavior.
99 MipsTargetMachine::MipsTargetMachine(const Target &T, const Triple &TT,
100                                      StringRef CPU, StringRef FS,
101                                      const TargetOptions &Options,
102                                      Optional<Reloc::Model> RM,
103                                      CodeModel::Model CM, CodeGenOpt::Level OL,
104                                      bool isLittle)
105     : LLVMTargetMachine(T, computeDataLayout(TT, CPU, Options, isLittle), TT,
106                         CPU, FS, Options, getEffectiveRelocModel(CM, RM), CM,
107                         OL),
108       isLittle(isLittle), TLOF(llvm::make_unique<MipsTargetObjectFile>()),
109       ABI(MipsABIInfo::computeTargetABI(TT, CPU, Options.MCOptions)),
110       Subtarget(nullptr), DefaultSubtarget(TT, CPU, FS, isLittle, *this),
111       NoMips16Subtarget(TT, CPU, FS.empty() ? "-mips16" : FS.str() + ",-mips16",
112                         isLittle, *this),
113       Mips16Subtarget(TT, CPU, FS.empty() ? "+mips16" : FS.str() + ",+mips16",
114                       isLittle, *this) {
115   Subtarget = &DefaultSubtarget;
116   initAsmInfo();
117 }
118 
119 MipsTargetMachine::~MipsTargetMachine() = default;
120 
121 void MipsebTargetMachine::anchor() {}
122 
123 MipsebTargetMachine::MipsebTargetMachine(const Target &T, const Triple &TT,
124                                          StringRef CPU, StringRef FS,
125                                          const TargetOptions &Options,
126                                          Optional<Reloc::Model> RM,
127                                          CodeModel::Model CM,
128                                          CodeGenOpt::Level OL)
129     : MipsTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, false) {}
130 
131 void MipselTargetMachine::anchor() {}
132 
133 MipselTargetMachine::MipselTargetMachine(const Target &T, const Triple &TT,
134                                          StringRef CPU, StringRef FS,
135                                          const TargetOptions &Options,
136                                          Optional<Reloc::Model> RM,
137                                          CodeModel::Model CM,
138                                          CodeGenOpt::Level OL)
139     : MipsTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, true) {}
140 
141 const MipsSubtarget *
142 MipsTargetMachine::getSubtargetImpl(const Function &F) const {
143   Attribute CPUAttr = F.getFnAttribute("target-cpu");
144   Attribute FSAttr = F.getFnAttribute("target-features");
145 
146   std::string CPU = !CPUAttr.hasAttribute(Attribute::None)
147                         ? CPUAttr.getValueAsString().str()
148                         : TargetCPU;
149   std::string FS = !FSAttr.hasAttribute(Attribute::None)
150                        ? FSAttr.getValueAsString().str()
151                        : TargetFS;
152   bool hasMips16Attr =
153       !F.getFnAttribute("mips16").hasAttribute(Attribute::None);
154   bool hasNoMips16Attr =
155       !F.getFnAttribute("nomips16").hasAttribute(Attribute::None);
156 
157   bool HasMicroMipsAttr =
158       !F.getFnAttribute("micromips").hasAttribute(Attribute::None);
159   bool HasNoMicroMipsAttr =
160       !F.getFnAttribute("nomicromips").hasAttribute(Attribute::None);
161 
162   // FIXME: This is related to the code below to reset the target options,
163   // we need to know whether or not the soft float flag is set on the
164   // function, so we can enable it as a subtarget feature.
165   bool softFloat =
166       F.hasFnAttribute("use-soft-float") &&
167       F.getFnAttribute("use-soft-float").getValueAsString() == "true";
168 
169   if (hasMips16Attr)
170     FS += FS.empty() ? "+mips16" : ",+mips16";
171   else if (hasNoMips16Attr)
172     FS += FS.empty() ? "-mips16" : ",-mips16";
173   if (HasMicroMipsAttr)
174     FS += FS.empty() ? "+micromips" : ",+micromips";
175   else if (HasNoMicroMipsAttr)
176     FS += FS.empty() ? "-micromips" : ",-micromips";
177   if (softFloat)
178     FS += FS.empty() ? "+soft-float" : ",+soft-float";
179 
180   auto &I = SubtargetMap[CPU + FS];
181   if (!I) {
182     // This needs to be done before we create a new subtarget since any
183     // creation will depend on the TM and the code generation flags on the
184     // function that reside in TargetOptions.
185     resetTargetOptions(F);
186     I = llvm::make_unique<MipsSubtarget>(TargetTriple, CPU, FS, isLittle,
187                                          *this);
188   }
189   return I.get();
190 }
191 
192 void MipsTargetMachine::resetSubtarget(MachineFunction *MF) {
193   DEBUG(dbgs() << "resetSubtarget\n");
194 
195   Subtarget = const_cast<MipsSubtarget *>(getSubtargetImpl(*MF->getFunction()));
196   MF->setSubtarget(Subtarget);
197 }
198 
199 namespace {
200 
201 /// Mips Code Generator Pass Configuration Options.
202 class MipsPassConfig : public TargetPassConfig {
203 public:
204   MipsPassConfig(MipsTargetMachine &TM, PassManagerBase &PM)
205     : TargetPassConfig(TM, PM) {
206     // The current implementation of long branch pass requires a scratch
207     // register ($at) to be available before branch instructions. Tail merging
208     // can break this requirement, so disable it when long branch pass is
209     // enabled.
210     EnableTailMerge = !getMipsSubtarget().enableLongBranchPass();
211   }
212 
213   MipsTargetMachine &getMipsTargetMachine() const {
214     return getTM<MipsTargetMachine>();
215   }
216 
217   const MipsSubtarget &getMipsSubtarget() const {
218     return *getMipsTargetMachine().getSubtargetImpl();
219   }
220 
221   void addIRPasses() override;
222   bool addInstSelector() override;
223   void addPreEmitPass() override;
224   void addPreRegAlloc() override;
225 };
226 
227 } // end anonymous namespace
228 
229 TargetPassConfig *MipsTargetMachine::createPassConfig(PassManagerBase &PM) {
230   return new MipsPassConfig(*this, PM);
231 }
232 
233 void MipsPassConfig::addIRPasses() {
234   TargetPassConfig::addIRPasses();
235   addPass(createAtomicExpandPass());
236   if (getMipsSubtarget().os16())
237     addPass(createMipsOs16Pass());
238   if (getMipsSubtarget().inMips16HardFloat())
239     addPass(createMips16HardFloatPass());
240 }
241 // Install an instruction selector pass using
242 // the ISelDag to gen Mips code.
243 bool MipsPassConfig::addInstSelector() {
244   addPass(createMipsModuleISelDagPass());
245   addPass(createMips16ISelDag(getMipsTargetMachine(), getOptLevel()));
246   addPass(createMipsSEISelDag(getMipsTargetMachine(), getOptLevel()));
247   return false;
248 }
249 
250 void MipsPassConfig::addPreRegAlloc() {
251   addPass(createMipsOptimizePICCallPass());
252 }
253 
254 TargetIRAnalysis MipsTargetMachine::getTargetIRAnalysis() {
255   return TargetIRAnalysis([this](const Function &F) {
256     if (Subtarget->allowMixed16_32()) {
257       DEBUG(errs() << "No Target Transform Info Pass Added\n");
258       // FIXME: This is no longer necessary as the TTI returned is per-function.
259       return TargetTransformInfo(F.getParent()->getDataLayout());
260     }
261 
262     DEBUG(errs() << "Target Transform Info Pass Added\n");
263     return TargetTransformInfo(BasicTTIImpl(this, F));
264   });
265 }
266 
267 // Implemented by targets that want to run passes immediately before
268 // machine code is emitted. return true if -print-machineinstrs should
269 // print out the code after the passes.
270 void MipsPassConfig::addPreEmitPass() {
271   addPass(createMicroMipsSizeReductionPass());
272 
273   // The delay slot filler pass can potientially create forbidden slot (FS)
274   // hazards for MIPSR6 which the hazard schedule pass (HSP) will fix. Any
275   // (new) pass that creates compact branches after the HSP must handle FS
276   // hazards itself or be pipelined before the HSP.
277   addPass(createMipsDelaySlotFillerPass());
278   addPass(createMipsHazardSchedule());
279   addPass(createMipsLongBranchPass());
280   addPass(createMipsConstantIslandPass());
281 }
282