1 //===-- X86Subtarget.cpp - X86 Subtarget Information ----------------------===//
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 implements the X86 specific subclass of TargetSubtargetInfo.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "X86Subtarget.h"
15 #include "X86InstrInfo.h"
16 #include "X86TargetMachine.h"
17 #include "llvm/CodeGen/Analysis.h"
18 #include "llvm/IR/Attributes.h"
19 #include "llvm/IR/Function.h"
20 #include "llvm/IR/GlobalValue.h"
21 #include "llvm/Support/CommandLine.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/ErrorHandling.h"
24 #include "llvm/Support/Host.h"
25 #include "llvm/Support/raw_ostream.h"
26 #include "llvm/Target/TargetMachine.h"
27 #include "llvm/Target/TargetOptions.h"
28 
29 #if defined(_MSC_VER)
30 #include <intrin.h>
31 #endif
32 
33 using namespace llvm;
34 
35 #define DEBUG_TYPE "subtarget"
36 
37 #define GET_SUBTARGETINFO_TARGET_DESC
38 #define GET_SUBTARGETINFO_CTOR
39 #include "X86GenSubtargetInfo.inc"
40 
41 // Temporary option to control early if-conversion for x86 while adding machine
42 // models.
43 static cl::opt<bool>
44 X86EarlyIfConv("x86-early-ifcvt", cl::Hidden,
45                cl::desc("Enable early if-conversion on X86"));
46 
47 
48 /// Classify a blockaddress reference for the current subtarget according to how
49 /// we should reference it in a non-pcrel context.
50 unsigned char X86Subtarget::classifyBlockAddressReference() const {
51   return classifyLocalReference(nullptr);
52 }
53 
54 /// Classify a global variable reference for the current subtarget according to
55 /// how we should reference it in a non-pcrel context.
56 unsigned char
57 X86Subtarget::classifyGlobalReference(const GlobalValue *GV) const {
58   return classifyGlobalReference(GV, *GV->getParent());
59 }
60 
61 unsigned char
62 X86Subtarget::classifyLocalReference(const GlobalValue *GV) const {
63   // 64 bits can use %rip addressing for anything local.
64   if (is64Bit())
65     return X86II::MO_NO_FLAG;
66 
67   // If this is for a position dependent executable, the static linker can
68   // figure it out.
69   if (TM.getRelocationModel() != Reloc::PIC_)
70     return X86II::MO_NO_FLAG;
71 
72   // The COFF dynamic linker just patches the executable sections.
73   if (isTargetCOFF())
74     return X86II::MO_NO_FLAG;
75 
76   if (isTargetDarwin()) {
77     // 32 bit macho has no relocation for a-b if a is undefined, even if
78     // b is in the section that is being relocated.
79     // This means we have to use o load even for GVs that are known to be
80     // local to the dso.
81     if (GV && (GV->isDeclarationForLinker() || GV->hasCommonLinkage()))
82       return X86II::MO_DARWIN_NONLAZY_PIC_BASE;
83 
84     return X86II::MO_PIC_BASE_OFFSET;
85   }
86 
87   return X86II::MO_GOTOFF;
88 }
89 
90 unsigned char X86Subtarget::classifyGlobalReference(const GlobalValue *GV,
91                                                     const Module &M) const {
92   // Large model never uses stubs.
93   if (TM.getCodeModel() == CodeModel::Large)
94     return X86II::MO_NO_FLAG;
95 
96   Reloc::Model RM = TM.getRelocationModel();
97   if (shouldAssumeDSOLocal(RM, TargetTriple, M, GV))
98     return classifyLocalReference(GV);
99 
100   if (isTargetCOFF())
101     return X86II::MO_DLLIMPORT;
102 
103   if (is64Bit())
104     return X86II::MO_GOTPCREL;
105 
106   if (isTargetDarwin()) {
107     if (RM != Reloc::PIC_)
108       return X86II::MO_DARWIN_NONLAZY;
109     return X86II::MO_DARWIN_NONLAZY_PIC_BASE;
110   }
111 
112   return X86II::MO_GOT;
113 }
114 
115 unsigned char
116 X86Subtarget::classifyGlobalFunctionReference(const GlobalValue *GV) const {
117   return classifyGlobalFunctionReference(GV, *GV->getParent());
118 }
119 
120 unsigned char
121 X86Subtarget::classifyGlobalFunctionReference(const GlobalValue *GV,
122                                               const Module &M) const {
123   if (shouldAssumeDSOLocal(TM.getRelocationModel(), TargetTriple, M, GV))
124     return X86II::MO_NO_FLAG;
125 
126   assert(!isTargetCOFF());
127 
128   if (isTargetELF())
129     return X86II::MO_PLT;
130 
131   if (is64Bit()) {
132     auto *F = dyn_cast_or_null<Function>(GV);
133     if (F && F->hasFnAttribute(Attribute::NonLazyBind))
134       // If the function is marked as non-lazy, generate an indirect call
135       // which loads from the GOT directly. This avoids runtime overhead
136       // at the cost of eager binding (and one extra byte of encoding).
137       return X86II::MO_GOTPCREL;
138     return X86II::MO_NO_FLAG;
139   }
140 
141   // PC-relative references to external symbols should go through $stub,
142   // unless we're building with the leopard linker or later, which
143   // automatically synthesizes these stubs.
144   if (!getTargetTriple().isMacOSX() ||
145       getTargetTriple().isMacOSXVersionLT(10, 5))
146     return X86II::MO_DARWIN_STUB;
147 
148   return X86II::MO_NO_FLAG;
149 }
150 
151 /// This function returns the name of a function which has an interface like
152 /// the non-standard bzero function, if such a function exists on the
153 /// current subtarget and it is considered preferable over memset with zero
154 /// passed as the second argument. Otherwise it returns null.
155 const char *X86Subtarget::getBZeroEntry() const {
156   // Darwin 10 has a __bzero entry point for this purpose.
157   if (getTargetTriple().isMacOSX() &&
158       !getTargetTriple().isMacOSXVersionLT(10, 6))
159     return "__bzero";
160 
161   return nullptr;
162 }
163 
164 bool X86Subtarget::hasSinCos() const {
165   return getTargetTriple().isMacOSX() &&
166     !getTargetTriple().isMacOSXVersionLT(10, 9) &&
167     is64Bit();
168 }
169 
170 /// Return true if the subtarget allows calls to immediate address.
171 bool X86Subtarget::isLegalToCallImmediateAddr() const {
172   // FIXME: I386 PE/COFF supports PC relative calls using IMAGE_REL_I386_REL32
173   // but WinCOFFObjectWriter::RecordRelocation cannot emit them.  Once it does,
174   // the following check for Win32 should be removed.
175   if (In64BitMode || isTargetWin32())
176     return false;
177   return isTargetELF() || TM.getRelocationModel() == Reloc::Static;
178 }
179 
180 void X86Subtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
181   std::string CPUName = CPU;
182   if (CPUName.empty())
183     CPUName = "generic";
184 
185   // Make sure 64-bit features are available in 64-bit mode. (But make sure
186   // SSE2 can be turned off explicitly.)
187   std::string FullFS = FS;
188   if (In64BitMode) {
189     if (!FullFS.empty())
190       FullFS = "+64bit,+sse2," + FullFS;
191     else
192       FullFS = "+64bit,+sse2";
193   }
194 
195   // LAHF/SAHF are always supported in non-64-bit mode.
196   if (!In64BitMode) {
197     if (!FullFS.empty())
198       FullFS = "+sahf," + FullFS;
199     else
200       FullFS = "+sahf";
201   }
202 
203 
204   // Parse features string and set the CPU.
205   ParseSubtargetFeatures(CPUName, FullFS);
206 
207   // All CPUs that implement SSE4.2 or SSE4A support unaligned accesses of
208   // 16-bytes and under that are reasonably fast. These features were
209   // introduced with Intel's Nehalem/Silvermont and AMD's Family10h
210   // micro-architectures respectively.
211   if (hasSSE42() || hasSSE4A())
212     IsUAMem16Slow = false;
213 
214   InstrItins = getInstrItineraryForCPU(CPUName);
215 
216   // It's important to keep the MCSubtargetInfo feature bits in sync with
217   // target data structure which is shared with MC code emitter, etc.
218   if (In64BitMode)
219     ToggleFeature(X86::Mode64Bit);
220   else if (In32BitMode)
221     ToggleFeature(X86::Mode32Bit);
222   else if (In16BitMode)
223     ToggleFeature(X86::Mode16Bit);
224   else
225     llvm_unreachable("Not 16-bit, 32-bit or 64-bit mode!");
226 
227   DEBUG(dbgs() << "Subtarget features: SSELevel " << X86SSELevel
228                << ", 3DNowLevel " << X863DNowLevel
229                << ", 64bit " << HasX86_64 << "\n");
230   assert((!In64BitMode || HasX86_64) &&
231          "64-bit code requested on a subtarget that doesn't support it!");
232 
233   // Stack alignment is 16 bytes on Darwin, Linux, kFreeBSD and Solaris (both
234   // 32 and 64 bit) and for all 64-bit targets.
235   if (StackAlignOverride)
236     stackAlignment = StackAlignOverride;
237   else if (isTargetDarwin() || isTargetLinux() || isTargetSolaris() ||
238            isTargetKFreeBSD() || In64BitMode)
239     stackAlignment = 16;
240 }
241 
242 void X86Subtarget::initializeEnvironment() {
243   X86SSELevel = NoSSE;
244   X863DNowLevel = NoThreeDNow;
245   HasX87 = false;
246   HasCMov = false;
247   HasX86_64 = false;
248   HasPOPCNT = false;
249   HasSSE4A = false;
250   HasAES = false;
251   HasFXSR = false;
252   HasXSAVE = false;
253   HasXSAVEOPT = false;
254   HasXSAVEC = false;
255   HasXSAVES = false;
256   HasPCLMUL = false;
257   HasFMA = false;
258   HasFMA4 = false;
259   HasXOP = false;
260   HasTBM = false;
261   HasMOVBE = false;
262   HasRDRAND = false;
263   HasF16C = false;
264   HasFSGSBase = false;
265   HasLZCNT = false;
266   HasBMI = false;
267   HasBMI2 = false;
268   HasVBMI = false;
269   HasIFMA = false;
270   HasRTM = false;
271   HasHLE = false;
272   HasERI = false;
273   HasCDI = false;
274   HasPFI = false;
275   HasDQI = false;
276   HasBWI = false;
277   HasVLX = false;
278   HasADX = false;
279   HasPKU = false;
280   HasSHA = false;
281   HasPRFCHW = false;
282   HasRDSEED = false;
283   HasLAHFSAHF = false;
284   HasMWAITX = false;
285   HasMPX = false;
286   IsBTMemSlow = false;
287   IsSHLDSlow = false;
288   IsUAMem16Slow = false;
289   IsUAMem32Slow = false;
290   HasSSEUnalignedMem = false;
291   HasCmpxchg16b = false;
292   UseLeaForSP = false;
293   HasFastPartialYMMWrite = false;
294   HasSlowDivide32 = false;
295   HasSlowDivide64 = false;
296   PadShortFunctions = false;
297   CallRegIndirect = false;
298   LEAUsesAG = false;
299   SlowLEA = false;
300   SlowIncDec = false;
301   stackAlignment = 4;
302   // FIXME: this is a known good value for Yonah. How about others?
303   MaxInlineSizeThreshold = 128;
304   UseSoftFloat = false;
305 }
306 
307 X86Subtarget &X86Subtarget::initializeSubtargetDependencies(StringRef CPU,
308                                                             StringRef FS) {
309   initializeEnvironment();
310   initSubtargetFeatures(CPU, FS);
311   return *this;
312 }
313 
314 X86Subtarget::X86Subtarget(const Triple &TT, StringRef CPU, StringRef FS,
315                            const X86TargetMachine &TM,
316                            unsigned StackAlignOverride)
317     : X86GenSubtargetInfo(TT, CPU, FS), X86ProcFamily(Others),
318       PICStyle(PICStyles::None), TM(TM), TargetTriple(TT),
319       StackAlignOverride(StackAlignOverride),
320       In64BitMode(TargetTriple.getArch() == Triple::x86_64),
321       In32BitMode(TargetTriple.getArch() == Triple::x86 &&
322                   TargetTriple.getEnvironment() != Triple::CODE16),
323       In16BitMode(TargetTriple.getArch() == Triple::x86 &&
324                   TargetTriple.getEnvironment() == Triple::CODE16),
325       TSInfo(), InstrInfo(initializeSubtargetDependencies(CPU, FS)),
326       TLInfo(TM, *this), FrameLowering(*this, getStackAlignment()) {
327   // Determine the PICStyle based on the target selected.
328   if (TM.getRelocationModel() == Reloc::Static) {
329     // Unless we're in PIC or DynamicNoPIC mode, set the PIC style to None.
330     setPICStyle(PICStyles::None);
331   } else if (is64Bit()) {
332     // PIC in 64 bit mode is always rip-rel.
333     setPICStyle(PICStyles::RIPRel);
334   } else if (isTargetCOFF()) {
335     setPICStyle(PICStyles::None);
336   } else if (isTargetDarwin()) {
337     if (TM.getRelocationModel() == Reloc::PIC_)
338       setPICStyle(PICStyles::StubPIC);
339     else {
340       assert(TM.getRelocationModel() == Reloc::DynamicNoPIC);
341       setPICStyle(PICStyles::StubDynamicNoPIC);
342     }
343   } else if (isTargetELF()) {
344     setPICStyle(PICStyles::GOT);
345   }
346 }
347 
348 bool X86Subtarget::enableEarlyIfConversion() const {
349   return hasCMov() && X86EarlyIfConv;
350 }
351 
352