1 //===-- X86TargetMachine.cpp - Define TargetMachine for the X86 -----------===//
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 // This file defines the X86 specific subclass of TargetMachine.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "X86TargetMachine.h"
15 #include "X86.h"
16 #include "X86TargetObjectFile.h"
17 #include "X86TargetTransformInfo.h"
18 #include "llvm/CodeGen/Passes.h"
19 #include "llvm/CodeGen/TargetPassConfig.h"
20 #include "llvm/IR/Function.h"
21 #include "llvm/IR/LegacyPassManager.h"
22 #include "llvm/Support/CommandLine.h"
23 #include "llvm/Support/FormattedStream.h"
24 #include "llvm/Support/TargetRegistry.h"
25 #include "llvm/Target/TargetOptions.h"
26 using namespace llvm;
27 
28 static cl::opt<bool> EnableMachineCombinerPass("x86-machine-combiner",
29                                cl::desc("Enable the machine combiner pass"),
30                                cl::init(true), cl::Hidden);
31 
32 namespace llvm {
33 void initializeWinEHStatePassPass(PassRegistry &);
34 }
35 
36 extern "C" void LLVMInitializeX86Target() {
37   // Register the target.
38   RegisterTargetMachine<X86TargetMachine> X(TheX86_32Target);
39   RegisterTargetMachine<X86TargetMachine> Y(TheX86_64Target);
40 
41   PassRegistry &PR = *PassRegistry::getPassRegistry();
42   initializeWinEHStatePassPass(PR);
43   initializeFixupBWInstPassPass(PR);
44 }
45 
46 static std::unique_ptr<TargetLoweringObjectFile> createTLOF(const Triple &TT) {
47   if (TT.isOSBinFormatMachO()) {
48     if (TT.getArch() == Triple::x86_64)
49       return make_unique<X86_64MachoTargetObjectFile>();
50     return make_unique<TargetLoweringObjectFileMachO>();
51   }
52 
53   if (TT.isOSLinux() || TT.isOSNaCl())
54     return make_unique<X86LinuxNaClTargetObjectFile>();
55   if (TT.isOSBinFormatELF())
56     return make_unique<X86ELFTargetObjectFile>();
57   if (TT.isKnownWindowsMSVCEnvironment() || TT.isWindowsCoreCLREnvironment())
58     return make_unique<X86WindowsTargetObjectFile>();
59   if (TT.isOSBinFormatCOFF())
60     return make_unique<TargetLoweringObjectFileCOFF>();
61   llvm_unreachable("unknown subtarget type");
62 }
63 
64 static std::string computeDataLayout(const Triple &TT) {
65   // X86 is little endian
66   std::string Ret = "e";
67 
68   Ret += DataLayout::getManglingComponent(TT);
69   // X86 and x32 have 32 bit pointers.
70   if ((TT.isArch64Bit() &&
71        (TT.getEnvironment() == Triple::GNUX32 || TT.isOSNaCl())) ||
72       !TT.isArch64Bit())
73     Ret += "-p:32:32";
74 
75   // Some ABIs align 64 bit integers and doubles to 64 bits, others to 32.
76   if (TT.isArch64Bit() || TT.isOSWindows() || TT.isOSNaCl())
77     Ret += "-i64:64";
78   else if (TT.isOSIAMCU())
79     Ret += "-i64:32-f64:32";
80   else
81     Ret += "-f64:32:64";
82 
83   // Some ABIs align long double to 128 bits, others to 32.
84   if (TT.isOSNaCl() || TT.isOSIAMCU())
85     ; // No f80
86   else if (TT.isArch64Bit() || TT.isOSDarwin())
87     Ret += "-f80:128";
88   else
89     Ret += "-f80:32";
90 
91   if (TT.isOSIAMCU())
92     Ret += "-f128:32";
93 
94   // The registers can hold 8, 16, 32 or, in x86-64, 64 bits.
95   if (TT.isArch64Bit())
96     Ret += "-n8:16:32:64";
97   else
98     Ret += "-n8:16:32";
99 
100   // The stack is aligned to 32 bits on some ABIs and 128 bits on others.
101   if ((!TT.isArch64Bit() && TT.isOSWindows()) || TT.isOSIAMCU())
102     Ret += "-a:0:32-S32";
103   else
104     Ret += "-S128";
105 
106   return Ret;
107 }
108 
109 static Reloc::Model getEffectiveRelocModel(const Triple &TT,
110                                            Optional<Reloc::Model> RM) {
111   bool is64Bit = TT.getArch() == Triple::x86_64;
112   if (!RM.hasValue()) {
113     // Darwin defaults to PIC in 64 bit mode and dynamic-no-pic in 32 bit mode.
114     // Win64 requires rip-rel addressing, thus we force it to PIC. Otherwise we
115     // use static relocation model by default.
116     if (TT.isOSDarwin()) {
117       if (is64Bit)
118         return Reloc::PIC_;
119       return Reloc::DynamicNoPIC;
120     }
121     if (TT.isOSWindows() && is64Bit)
122       return Reloc::PIC_;
123     return Reloc::Static;
124   }
125 
126   // ELF and X86-64 don't have a distinct DynamicNoPIC model.  DynamicNoPIC
127   // is defined as a model for code which may be used in static or dynamic
128   // executables but not necessarily a shared library. On X86-32 we just
129   // compile in -static mode, in x86-64 we use PIC.
130   if (*RM == Reloc::DynamicNoPIC) {
131     if (is64Bit)
132       return Reloc::PIC_;
133     if (!TT.isOSDarwin())
134       return Reloc::Static;
135   }
136 
137   // If we are on Darwin, disallow static relocation model in X86-64 mode, since
138   // the Mach-O file format doesn't support it.
139   if (*RM == Reloc::Static && TT.isOSDarwin() && is64Bit)
140     return Reloc::PIC_;
141 
142   return *RM;
143 }
144 
145 /// Create an X86 target.
146 ///
147 X86TargetMachine::X86TargetMachine(const Target &T, const Triple &TT,
148                                    StringRef CPU, StringRef FS,
149                                    const TargetOptions &Options,
150                                    Optional<Reloc::Model> RM,
151                                    CodeModel::Model CM, CodeGenOpt::Level OL)
152     : LLVMTargetMachine(T, computeDataLayout(TT), TT, CPU, FS, Options,
153                         getEffectiveRelocModel(TT, RM), CM, OL),
154       TLOF(createTLOF(getTargetTriple())),
155       Subtarget(TT, CPU, FS, *this, Options.StackAlignmentOverride) {
156   // Windows stack unwinder gets confused when execution flow "falls through"
157   // after a call to 'noreturn' function.
158   // To prevent that, we emit a trap for 'unreachable' IR instructions.
159   // (which on X86, happens to be the 'ud2' instruction)
160   // On PS4, the "return address" of a 'noreturn' call must still be within
161   // the calling function, and TrapUnreachable is an easy way to get that.
162   if (Subtarget.isTargetWin64() || Subtarget.isTargetPS4())
163     this->Options.TrapUnreachable = true;
164 
165   // By default (and when -ffast-math is on), enable estimate codegen for
166   // everything except scalar division. By default, use 1 refinement step for
167   // all operations. Defaults may be overridden by using command-line options.
168   // Scalar division estimates are disabled because they break too much
169   // real-world code. These defaults match GCC behavior.
170   this->Options.Reciprocals.setDefaults("sqrtf", true, 1);
171   this->Options.Reciprocals.setDefaults("divf", false, 1);
172   this->Options.Reciprocals.setDefaults("vec-sqrtf", true, 1);
173   this->Options.Reciprocals.setDefaults("vec-divf", true, 1);
174 
175   initAsmInfo();
176 }
177 
178 X86TargetMachine::~X86TargetMachine() {}
179 
180 const X86Subtarget *
181 X86TargetMachine::getSubtargetImpl(const Function &F) const {
182   Attribute CPUAttr = F.getFnAttribute("target-cpu");
183   Attribute FSAttr = F.getFnAttribute("target-features");
184 
185   StringRef CPU = !CPUAttr.hasAttribute(Attribute::None)
186                       ? CPUAttr.getValueAsString()
187                       : (StringRef)TargetCPU;
188   StringRef FS = !FSAttr.hasAttribute(Attribute::None)
189                      ? FSAttr.getValueAsString()
190                      : (StringRef)TargetFS;
191 
192   SmallString<512> Key;
193   Key.reserve(CPU.size() + FS.size());
194   Key += CPU;
195   Key += FS;
196 
197   // FIXME: This is related to the code below to reset the target options,
198   // we need to know whether or not the soft float flag is set on the
199   // function before we can generate a subtarget. We also need to use
200   // it as a key for the subtarget since that can be the only difference
201   // between two functions.
202   bool SoftFloat =
203       F.getFnAttribute("use-soft-float").getValueAsString() == "true";
204   // If the soft float attribute is set on the function turn on the soft float
205   // subtarget feature.
206   if (SoftFloat)
207     Key += FS.empty() ? "+soft-float" : ",+soft-float";
208 
209   FS = Key.substr(CPU.size());
210 
211   auto &I = SubtargetMap[Key];
212   if (!I) {
213     // This needs to be done before we create a new subtarget since any
214     // creation will depend on the TM and the code generation flags on the
215     // function that reside in TargetOptions.
216     resetTargetOptions(F);
217     I = llvm::make_unique<X86Subtarget>(TargetTriple, CPU, FS, *this,
218                                         Options.StackAlignmentOverride);
219   }
220   return I.get();
221 }
222 
223 //===----------------------------------------------------------------------===//
224 // Command line options for x86
225 //===----------------------------------------------------------------------===//
226 static cl::opt<bool>
227 UseVZeroUpper("x86-use-vzeroupper", cl::Hidden,
228   cl::desc("Minimize AVX to SSE transition penalty"),
229   cl::init(true));
230 
231 //===----------------------------------------------------------------------===//
232 // X86 TTI query.
233 //===----------------------------------------------------------------------===//
234 
235 TargetIRAnalysis X86TargetMachine::getTargetIRAnalysis() {
236   return TargetIRAnalysis([this](const Function &F) {
237     return TargetTransformInfo(X86TTIImpl(this, F));
238   });
239 }
240 
241 
242 //===----------------------------------------------------------------------===//
243 // Pass Pipeline Configuration
244 //===----------------------------------------------------------------------===//
245 
246 namespace {
247 /// X86 Code Generator Pass Configuration Options.
248 class X86PassConfig : public TargetPassConfig {
249 public:
250   X86PassConfig(X86TargetMachine *TM, PassManagerBase &PM)
251     : TargetPassConfig(TM, PM) {}
252 
253   X86TargetMachine &getX86TargetMachine() const {
254     return getTM<X86TargetMachine>();
255   }
256 
257   void addIRPasses() override;
258   bool addInstSelector() override;
259   bool addILPOpts() override;
260   bool addPreISel() override;
261   void addPreRegAlloc() override;
262   void addPostRegAlloc() override;
263   void addPreEmitPass() override;
264   void addPreSched2() override;
265 };
266 } // namespace
267 
268 TargetPassConfig *X86TargetMachine::createPassConfig(PassManagerBase &PM) {
269   return new X86PassConfig(this, PM);
270 }
271 
272 void X86PassConfig::addIRPasses() {
273   addPass(createAtomicExpandPass(&getX86TargetMachine()));
274 
275   TargetPassConfig::addIRPasses();
276 }
277 
278 bool X86PassConfig::addInstSelector() {
279   // Install an instruction selector.
280   addPass(createX86ISelDag(getX86TargetMachine(), getOptLevel()));
281 
282   // For ELF, cleanup any local-dynamic TLS accesses.
283   if (TM->getTargetTriple().isOSBinFormatELF() &&
284       getOptLevel() != CodeGenOpt::None)
285     addPass(createCleanupLocalDynamicTLSPass());
286 
287   addPass(createX86GlobalBaseRegPass());
288   return false;
289 }
290 
291 bool X86PassConfig::addILPOpts() {
292   addPass(&EarlyIfConverterID);
293   if (EnableMachineCombinerPass)
294     addPass(&MachineCombinerID);
295   return true;
296 }
297 
298 bool X86PassConfig::addPreISel() {
299   // Only add this pass for 32-bit x86 Windows.
300   const Triple &TT = TM->getTargetTriple();
301   if (TT.isOSWindows() && TT.getArch() == Triple::x86)
302     addPass(createX86WinEHStatePass());
303   return true;
304 }
305 
306 void X86PassConfig::addPreRegAlloc() {
307   if (getOptLevel() != CodeGenOpt::None) {
308     addPass(createX86FixupSetCC());
309     addPass(createX86OptimizeLEAs());
310     addPass(createX86CallFrameOptimization());
311   }
312 
313   addPass(createX86WinAllocaExpander());
314 }
315 
316 void X86PassConfig::addPostRegAlloc() {
317   addPass(createX86FloatingPointStackifierPass());
318 }
319 
320 void X86PassConfig::addPreSched2() { addPass(createX86ExpandPseudoPass()); }
321 
322 void X86PassConfig::addPreEmitPass() {
323   if (getOptLevel() != CodeGenOpt::None)
324     addPass(createExecutionDependencyFixPass(&X86::VR128XRegClass));
325 
326   if (UseVZeroUpper)
327     addPass(createX86IssueVZeroUpperPass());
328 
329   if (getOptLevel() != CodeGenOpt::None) {
330     addPass(createX86FixupBWInsts());
331     addPass(createX86PadShortFunctions());
332     addPass(createX86FixupLEAs());
333   }
334 }
335