1//===-- X86Subtarget.cpp - X86 Subtarget Information ----------------------===//
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// This file implements the X86 specific subclass of TargetSubtargetInfo.
10//
11//===----------------------------------------------------------------------===//
12
13#include "X86Subtarget.h"
14#include "MCTargetDesc/X86BaseInfo.h"
15#include "X86.h"
16#include "X86CallLowering.h"
17#include "X86LegalizerInfo.h"
18#include "X86MacroFusion.h"
19#include "X86RegisterBankInfo.h"
20#include "X86TargetMachine.h"
21#include "llvm/ADT/Triple.h"
22#include "llvm/CodeGen/GlobalISel/CallLowering.h"
23#include "llvm/CodeGen/GlobalISel/InstructionSelect.h"
24#include "llvm/IR/Attributes.h"
25#include "llvm/IR/ConstantRange.h"
26#include "llvm/IR/Function.h"
27#include "llvm/IR/GlobalValue.h"
28#include "llvm/Support/Casting.h"
29#include "llvm/Support/CodeGen.h"
30#include "llvm/Support/CommandLine.h"
31#include "llvm/Support/Debug.h"
32#include "llvm/Support/ErrorHandling.h"
33#include "llvm/Support/raw_ostream.h"
34#include "llvm/Target/TargetMachine.h"
35
36#if defined(_MSC_VER)
37#include <intrin.h>
38#endif
39
40using namespace llvm;
41
42#define DEBUG_TYPE "subtarget"
43
44#define GET_SUBTARGETINFO_TARGET_DESC
45#define GET_SUBTARGETINFO_CTOR
46#include "X86GenSubtargetInfo.inc"
47
48// Temporary option to control early if-conversion for x86 while adding machine
49// models.
50static cl::opt<bool>
51X86EarlyIfConv("x86-early-ifcvt", cl::Hidden,
52               cl::desc("Enable early if-conversion on X86"));
53
54
55/// Classify a blockaddress reference for the current subtarget according to how
56/// we should reference it in a non-pcrel context.
57unsigned char X86Subtarget::classifyBlockAddressReference() const {
58  return classifyLocalReference(nullptr);
59}
60
61/// Classify a global variable reference for the current subtarget according to
62/// how we should reference it in a non-pcrel context.
63unsigned char
64X86Subtarget::classifyGlobalReference(const GlobalValue *GV) const {
65  return classifyGlobalReference(GV, *GV->getParent());
66}
67
68unsigned char
69X86Subtarget::classifyLocalReference(const GlobalValue *GV) const {
70  // If we're not PIC, it's not very interesting.
71  if (!isPositionIndependent())
72    return X86II::MO_NO_FLAG;
73
74  if (is64Bit()) {
75    // 64-bit ELF PIC local references may use GOTOFF relocations.
76    if (isTargetELF()) {
77      switch (TM.getCodeModel()) {
78      // 64-bit small code model is simple: All rip-relative.
79      case CodeModel::Tiny:
80        llvm_unreachable("Tiny codesize model not supported on X86");
81      case CodeModel::Small:
82      case CodeModel::Kernel:
83        return X86II::MO_NO_FLAG;
84
85      // The large PIC code model uses GOTOFF.
86      case CodeModel::Large:
87        return X86II::MO_GOTOFF;
88
89      // Medium is a hybrid: RIP-rel for code, GOTOFF for DSO local data.
90      case CodeModel::Medium:
91        // Constant pool and jump table handling pass a nullptr to this
92        // function so we need to use isa_and_nonnull.
93        if (isa_and_nonnull<Function>(GV))
94          return X86II::MO_NO_FLAG; // All code is RIP-relative
95        return X86II::MO_GOTOFF;    // Local symbols use GOTOFF.
96      }
97      llvm_unreachable("invalid code model");
98    }
99
100    // Otherwise, this is either a RIP-relative reference or a 64-bit movabsq,
101    // both of which use MO_NO_FLAG.
102    return X86II::MO_NO_FLAG;
103  }
104
105  // The COFF dynamic linker just patches the executable sections.
106  if (isTargetCOFF())
107    return X86II::MO_NO_FLAG;
108
109  if (isTargetDarwin()) {
110    // 32 bit macho has no relocation for a-b if a is undefined, even if
111    // b is in the section that is being relocated.
112    // This means we have to use o load even for GVs that are known to be
113    // local to the dso.
114    if (GV && (GV->isDeclarationForLinker() || GV->hasCommonLinkage()))
115      return X86II::MO_DARWIN_NONLAZY_PIC_BASE;
116
117    return X86II::MO_PIC_BASE_OFFSET;
118  }
119
120  return X86II::MO_GOTOFF;
121}
122
123unsigned char X86Subtarget::classifyGlobalReference(const GlobalValue *GV,
124                                                    const Module &M) const {
125  // The static large model never uses stubs.
126  if (TM.getCodeModel() == CodeModel::Large && !isPositionIndependent())
127    return X86II::MO_NO_FLAG;
128
129  // Absolute symbols can be referenced directly.
130  if (GV) {
131    if (Optional<ConstantRange> CR = GV->getAbsoluteSymbolRange()) {
132      // See if we can use the 8-bit immediate form. Note that some instructions
133      // will sign extend the immediate operand, so to be conservative we only
134      // accept the range [0,128).
135      if (CR->getUnsignedMax().ult(128))
136        return X86II::MO_ABS8;
137      else
138        return X86II::MO_NO_FLAG;
139    }
140  }
141
142  if (TM.shouldAssumeDSOLocal(M, GV))
143    return classifyLocalReference(GV);
144
145  if (isTargetCOFF()) {
146    if (GV->hasDLLImportStorageClass())
147      return X86II::MO_DLLIMPORT;
148    return X86II::MO_COFFSTUB;
149  }
150  // Some JIT users use *-win32-elf triples; these shouldn't use GOT tables.
151  if (isOSWindows())
152    return X86II::MO_NO_FLAG;
153
154  if (is64Bit()) {
155    // ELF supports a large, truly PIC code model with non-PC relative GOT
156    // references. Other object file formats do not. Use the no-flag, 64-bit
157    // reference for them.
158    if (TM.getCodeModel() == CodeModel::Large)
159      return isTargetELF() ? X86II::MO_GOT : X86II::MO_NO_FLAG;
160    return X86II::MO_GOTPCREL;
161  }
162
163  if (isTargetDarwin()) {
164    if (!isPositionIndependent())
165      return X86II::MO_DARWIN_NONLAZY;
166    return X86II::MO_DARWIN_NONLAZY_PIC_BASE;
167  }
168
169  // 32-bit ELF references GlobalAddress directly in static relocation model.
170  // We cannot use MO_GOT because EBX may not be set up.
171  if (TM.getRelocationModel() == Reloc::Static)
172    return X86II::MO_NO_FLAG;
173  return X86II::MO_GOT;
174}
175
176unsigned char
177X86Subtarget::classifyGlobalFunctionReference(const GlobalValue *GV) const {
178  return classifyGlobalFunctionReference(GV, *GV->getParent());
179}
180
181unsigned char
182X86Subtarget::classifyGlobalFunctionReference(const GlobalValue *GV,
183                                              const Module &M) const {
184  if (TM.shouldAssumeDSOLocal(M, GV))
185    return X86II::MO_NO_FLAG;
186
187  // Functions on COFF can be non-DSO local for two reasons:
188  // - They are marked dllimport
189  // - They are extern_weak, and a stub is needed
190  if (isTargetCOFF()) {
191    if (GV->hasDLLImportStorageClass())
192      return X86II::MO_DLLIMPORT;
193    return X86II::MO_COFFSTUB;
194  }
195
196  const Function *F = dyn_cast_or_null<Function>(GV);
197
198  if (isTargetELF()) {
199    if (is64Bit() && F && (CallingConv::X86_RegCall == F->getCallingConv()))
200      // According to psABI, PLT stub clobbers XMM8-XMM15.
201      // In Regcall calling convention those registers are used for passing
202      // parameters. Thus we need to prevent lazy binding in Regcall.
203      return X86II::MO_GOTPCREL;
204    // If PLT must be avoided then the call should be via GOTPCREL.
205    if (((F && F->hasFnAttribute(Attribute::NonLazyBind)) ||
206         (!F && M.getRtLibUseGOT())) &&
207        is64Bit())
208       return X86II::MO_GOTPCREL;
209    // Reference ExternalSymbol directly in static relocation model.
210    if (!is64Bit() && !GV && TM.getRelocationModel() == Reloc::Static)
211      return X86II::MO_NO_FLAG;
212    return X86II::MO_PLT;
213  }
214
215  if (is64Bit()) {
216    if (F && F->hasFnAttribute(Attribute::NonLazyBind))
217      // If the function is marked as non-lazy, generate an indirect call
218      // which loads from the GOT directly. This avoids runtime overhead
219      // at the cost of eager binding (and one extra byte of encoding).
220      return X86II::MO_GOTPCREL;
221    return X86II::MO_NO_FLAG;
222  }
223
224  return X86II::MO_NO_FLAG;
225}
226
227/// Return true if the subtarget allows calls to immediate address.
228bool X86Subtarget::isLegalToCallImmediateAddr() const {
229  // FIXME: I386 PE/COFF supports PC relative calls using IMAGE_REL_I386_REL32
230  // but WinCOFFObjectWriter::RecordRelocation cannot emit them.  Once it does,
231  // the following check for Win32 should be removed.
232  if (In64BitMode || isTargetWin32())
233    return false;
234  return isTargetELF() || TM.getRelocationModel() == Reloc::Static;
235}
236
237void X86Subtarget::initSubtargetFeatures(StringRef CPU, StringRef TuneCPU,
238                                         StringRef FS) {
239  if (CPU.empty())
240    CPU = "generic";
241
242  if (TuneCPU.empty())
243    TuneCPU = "i586"; // FIXME: "generic" is more modern than llc tests expect.
244
245  std::string FullFS = X86_MC::ParseX86Triple(TargetTriple);
246  assert(!FullFS.empty() && "Failed to parse X86 triple");
247
248  if (!FS.empty())
249    FullFS = (Twine(FullFS) + "," + FS).str();
250
251  // Parse features string and set the CPU.
252  ParseSubtargetFeatures(CPU, TuneCPU, FullFS);
253
254  // All CPUs that implement SSE4.2 or SSE4A support unaligned accesses of
255  // 16-bytes and under that are reasonably fast. These features were
256  // introduced with Intel's Nehalem/Silvermont and AMD's Family10h
257  // micro-architectures respectively.
258  if (hasSSE42() || hasSSE4A())
259    IsUAMem16Slow = false;
260
261  LLVM_DEBUG(dbgs() << "Subtarget features: SSELevel " << X86SSELevel
262                    << ", 3DNowLevel " << X863DNowLevel << ", 64bit "
263                    << HasX86_64 << "\n");
264  if (In64BitMode && !HasX86_64)
265    report_fatal_error("64-bit code requested on a subtarget that doesn't "
266                       "support it!");
267
268  // Stack alignment is 16 bytes on Darwin, Linux, kFreeBSD, NaCl, and for all
269  // 64-bit targets.  On Solaris (32-bit), stack alignment is 4 bytes
270  // following the i386 psABI, while on Illumos it is always 16 bytes.
271  if (StackAlignOverride)
272    stackAlignment = *StackAlignOverride;
273  else if (isTargetDarwin() || isTargetLinux() || isTargetKFreeBSD() ||
274           isTargetNaCl() || In64BitMode)
275    stackAlignment = Align(16);
276
277  // Consume the vector width attribute or apply any target specific limit.
278  if (PreferVectorWidthOverride)
279    PreferVectorWidth = PreferVectorWidthOverride;
280  else if (Prefer128Bit)
281    PreferVectorWidth = 128;
282  else if (Prefer256Bit)
283    PreferVectorWidth = 256;
284}
285
286X86Subtarget &X86Subtarget::initializeSubtargetDependencies(StringRef CPU,
287                                                            StringRef TuneCPU,
288                                                            StringRef FS) {
289  initSubtargetFeatures(CPU, TuneCPU, FS);
290  return *this;
291}
292
293X86Subtarget::X86Subtarget(const Triple &TT, StringRef CPU, StringRef TuneCPU,
294                           StringRef FS, const X86TargetMachine &TM,
295                           MaybeAlign StackAlignOverride,
296                           unsigned PreferVectorWidthOverride,
297                           unsigned RequiredVectorWidth)
298    : X86GenSubtargetInfo(TT, CPU, TuneCPU, FS),
299      PICStyle(PICStyles::Style::None), TM(TM), TargetTriple(TT),
300      StackAlignOverride(StackAlignOverride),
301      PreferVectorWidthOverride(PreferVectorWidthOverride),
302      RequiredVectorWidth(RequiredVectorWidth),
303      InstrInfo(initializeSubtargetDependencies(CPU, TuneCPU, FS)),
304      TLInfo(TM, *this), FrameLowering(*this, getStackAlignment()) {
305  // Determine the PICStyle based on the target selected.
306  if (!isPositionIndependent())
307    setPICStyle(PICStyles::Style::None);
308  else if (is64Bit())
309    setPICStyle(PICStyles::Style::RIPRel);
310  else if (isTargetCOFF())
311    setPICStyle(PICStyles::Style::None);
312  else if (isTargetDarwin())
313    setPICStyle(PICStyles::Style::StubPIC);
314  else if (isTargetELF())
315    setPICStyle(PICStyles::Style::GOT);
316
317  CallLoweringInfo.reset(new X86CallLowering(*getTargetLowering()));
318  Legalizer.reset(new X86LegalizerInfo(*this, TM));
319
320  auto *RBI = new X86RegisterBankInfo(*getRegisterInfo());
321  RegBankInfo.reset(RBI);
322  InstSelector.reset(createX86InstructionSelector(TM, *this, *RBI));
323}
324
325const CallLowering *X86Subtarget::getCallLowering() const {
326  return CallLoweringInfo.get();
327}
328
329InstructionSelector *X86Subtarget::getInstructionSelector() const {
330  return InstSelector.get();
331}
332
333const LegalizerInfo *X86Subtarget::getLegalizerInfo() const {
334  return Legalizer.get();
335}
336
337const RegisterBankInfo *X86Subtarget::getRegBankInfo() const {
338  return RegBankInfo.get();
339}
340
341bool X86Subtarget::enableEarlyIfConversion() const {
342  return hasCMov() && X86EarlyIfConv;
343}
344
345void X86Subtarget::getPostRAMutations(
346    std::vector<std::unique_ptr<ScheduleDAGMutation>> &Mutations) const {
347  Mutations.push_back(createX86MacroFusionDAGMutation());
348}
349
350bool X86Subtarget::isPositionIndependent() const {
351  return TM.isPositionIndependent();
352}
353