LLVM 17.0.0git
X86Subtarget.cpp
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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"
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"
26#include "llvm/IR/Attributes.h"
28#include "llvm/IR/Function.h"
29#include "llvm/IR/GlobalValue.h"
33#include "llvm/Support/Debug.h"
37
38#if defined(_MSC_VER)
39#include <intrin.h>
40#endif
41
42using namespace llvm;
43
44#define DEBUG_TYPE "subtarget"
45
46#define GET_SUBTARGETINFO_TARGET_DESC
47#define GET_SUBTARGETINFO_CTOR
48#include "X86GenSubtargetInfo.inc"
49
50// Temporary option to control early if-conversion for x86 while adding machine
51// models.
52static cl::opt<bool>
53X86EarlyIfConv("x86-early-ifcvt", cl::Hidden,
54 cl::desc("Enable early if-conversion on X86"));
55
56
57/// Classify a blockaddress reference for the current subtarget according to how
58/// we should reference it in a non-pcrel context.
60 return classifyLocalReference(nullptr);
61}
62
63/// Classify a global variable reference for the current subtarget according to
64/// how we should reference it in a non-pcrel context.
65unsigned char
67 return classifyGlobalReference(GV, *GV->getParent());
68}
69
70unsigned char
72 // Tagged globals have non-zero upper bits, which makes direct references
73 // require a 64-bit immediate. On the small code model this causes relocation
74 // errors, so we go through the GOT instead.
75 if (AllowTaggedGlobals && TM.getCodeModel() == CodeModel::Small && GV &&
76 !isa<Function>(GV))
78
79 // If we're not PIC, it's not very interesting.
81 return X86II::MO_NO_FLAG;
82
83 if (is64Bit()) {
84 // 64-bit ELF PIC local references may use GOTOFF relocations.
85 if (isTargetELF()) {
86 switch (TM.getCodeModel()) {
87 // 64-bit small code model is simple: All rip-relative.
88 case CodeModel::Tiny:
89 llvm_unreachable("Tiny codesize model not supported on X86");
92 return X86II::MO_NO_FLAG;
93
94 // The large PIC code model uses GOTOFF.
96 return X86II::MO_GOTOFF;
97
98 // Medium is a hybrid: RIP-rel for code, GOTOFF for DSO local data.
100 // Constant pool and jump table handling pass a nullptr to this
101 // function so we need to use isa_and_nonnull.
102 if (isa_and_nonnull<Function>(GV))
103 return X86II::MO_NO_FLAG; // All code is RIP-relative
104 return X86II::MO_GOTOFF; // Local symbols use GOTOFF.
105 }
106 llvm_unreachable("invalid code model");
107 }
108
109 // Otherwise, this is either a RIP-relative reference or a 64-bit movabsq,
110 // both of which use MO_NO_FLAG.
111 return X86II::MO_NO_FLAG;
112 }
113
114 // The COFF dynamic linker just patches the executable sections.
115 if (isTargetCOFF())
116 return X86II::MO_NO_FLAG;
117
118 if (isTargetDarwin()) {
119 // 32 bit macho has no relocation for a-b if a is undefined, even if
120 // b is in the section that is being relocated.
121 // This means we have to use o load even for GVs that are known to be
122 // local to the dso.
123 if (GV && (GV->isDeclarationForLinker() || GV->hasCommonLinkage()))
125
127 }
128
129 return X86II::MO_GOTOFF;
130}
131
133 const Module &M) const {
134 // The static large model never uses stubs.
136 return X86II::MO_NO_FLAG;
137
138 // Absolute symbols can be referenced directly.
139 if (GV) {
140 if (std::optional<ConstantRange> CR = GV->getAbsoluteSymbolRange()) {
141 // See if we can use the 8-bit immediate form. Note that some instructions
142 // will sign extend the immediate operand, so to be conservative we only
143 // accept the range [0,128).
144 if (CR->getUnsignedMax().ult(128))
145 return X86II::MO_ABS8;
146 else
147 return X86II::MO_NO_FLAG;
148 }
149 }
150
151 if (TM.shouldAssumeDSOLocal(M, GV))
152 return classifyLocalReference(GV);
153
154 if (isTargetCOFF()) {
155 // ExternalSymbolSDNode like _tls_index.
156 if (!GV)
157 return X86II::MO_NO_FLAG;
158 if (GV->hasDLLImportStorageClass())
159 return X86II::MO_DLLIMPORT;
160 return X86II::MO_COFFSTUB;
161 }
162 // Some JIT users use *-win32-elf triples; these shouldn't use GOT tables.
163 if (isOSWindows())
164 return X86II::MO_NO_FLAG;
165
166 if (is64Bit()) {
167 // ELF supports a large, truly PIC code model with non-PC relative GOT
168 // references. Other object file formats do not. Use the no-flag, 64-bit
169 // reference for them.
170 if (TM.getCodeModel() == CodeModel::Large)
172 // Tagged globals have non-zero upper bits, which makes direct references
173 // require a 64-bit immediate. So we can't let the linker relax the
174 // relocation to a 32-bit RIP-relative direct reference.
175 if (AllowTaggedGlobals && GV && !isa<Function>(GV))
177 return X86II::MO_GOTPCREL;
178 }
179
180 if (isTargetDarwin()) {
184 }
185
186 // 32-bit ELF references GlobalAddress directly in static relocation model.
187 // We cannot use MO_GOT because EBX may not be set up.
189 return X86II::MO_NO_FLAG;
190 return X86II::MO_GOT;
191}
192
193unsigned char
196}
197
198unsigned char
200 const Module &M) const {
201 if (TM.shouldAssumeDSOLocal(M, GV))
202 return X86II::MO_NO_FLAG;
203
204 // Functions on COFF can be non-DSO local for three reasons:
205 // - They are intrinsic functions (!GV)
206 // - They are marked dllimport
207 // - They are extern_weak, and a stub is needed
208 if (isTargetCOFF()) {
209 if (!GV)
210 return X86II::MO_NO_FLAG;
211 if (GV->hasDLLImportStorageClass())
212 return X86II::MO_DLLIMPORT;
213 return X86II::MO_COFFSTUB;
214 }
215
216 const Function *F = dyn_cast_or_null<Function>(GV);
217
218 if (isTargetELF()) {
219 if (is64Bit() && F && (CallingConv::X86_RegCall == F->getCallingConv()))
220 // According to psABI, PLT stub clobbers XMM8-XMM15.
221 // In Regcall calling convention those registers are used for passing
222 // parameters. Thus we need to prevent lazy binding in Regcall.
223 return X86II::MO_GOTPCREL;
224 // If PLT must be avoided then the call should be via GOTPCREL.
225 if (((F && F->hasFnAttribute(Attribute::NonLazyBind)) ||
226 (!F && M.getRtLibUseGOT())) &&
227 is64Bit())
228 return X86II::MO_GOTPCREL;
229 // Reference ExternalSymbol directly in static relocation model.
230 if (!is64Bit() && !GV && TM.getRelocationModel() == Reloc::Static)
231 return X86II::MO_NO_FLAG;
232 return X86II::MO_PLT;
233 }
234
235 if (is64Bit()) {
236 if (F && F->hasFnAttribute(Attribute::NonLazyBind))
237 // If the function is marked as non-lazy, generate an indirect call
238 // which loads from the GOT directly. This avoids runtime overhead
239 // at the cost of eager binding (and one extra byte of encoding).
240 return X86II::MO_GOTPCREL;
241 return X86II::MO_NO_FLAG;
242 }
243
244 return X86II::MO_NO_FLAG;
245}
246
247/// Return true if the subtarget allows calls to immediate address.
249 // FIXME: I386 PE/COFF supports PC relative calls using IMAGE_REL_I386_REL32
250 // but WinCOFFObjectWriter::RecordRelocation cannot emit them. Once it does,
251 // the following check for Win32 should be removed.
252 if (Is64Bit || isTargetWin32())
253 return false;
254 return isTargetELF() || TM.getRelocationModel() == Reloc::Static;
255}
256
257void X86Subtarget::initSubtargetFeatures(StringRef CPU, StringRef TuneCPU,
258 StringRef FS) {
259 if (CPU.empty())
260 CPU = "generic";
261
262 if (TuneCPU.empty())
263 TuneCPU = "i586"; // FIXME: "generic" is more modern than llc tests expect.
264
265 std::string FullFS = X86_MC::ParseX86Triple(TargetTriple);
266 assert(!FullFS.empty() && "Failed to parse X86 triple");
267
268 if (!FS.empty())
269 FullFS = (Twine(FullFS) + "," + FS).str();
270
271 // Parse features string and set the CPU.
272 ParseSubtargetFeatures(CPU, TuneCPU, FullFS);
273
274 // All CPUs that implement SSE4.2 or SSE4A support unaligned accesses of
275 // 16-bytes and under that are reasonably fast. These features were
276 // introduced with Intel's Nehalem/Silvermont and AMD's Family10h
277 // micro-architectures respectively.
278 if (hasSSE42() || hasSSE4A())
279 IsUnalignedMem16Slow = false;
280
281 LLVM_DEBUG(dbgs() << "Subtarget features: SSELevel " << X86SSELevel
282 << ", 3DNowLevel " << X863DNowLevel << ", 64bit "
283 << HasX86_64 << "\n");
284 if (Is64Bit && !HasX86_64)
285 report_fatal_error("64-bit code requested on a subtarget that doesn't "
286 "support it!");
287
288 // Stack alignment is 16 bytes on Darwin, Linux, kFreeBSD, NaCl, and for all
289 // 64-bit targets. On Solaris (32-bit), stack alignment is 4 bytes
290 // following the i386 psABI, while on Illumos it is always 16 bytes.
291 if (StackAlignOverride)
292 stackAlignment = *StackAlignOverride;
293 else if (isTargetDarwin() || isTargetLinux() || isTargetKFreeBSD() ||
294 isTargetNaCl() || Is64Bit)
295 stackAlignment = Align(16);
296
297 // Consume the vector width attribute or apply any target specific limit.
298 if (PreferVectorWidthOverride)
299 PreferVectorWidth = PreferVectorWidthOverride;
300 else if (Prefer128Bit)
301 PreferVectorWidth = 128;
302 else if (Prefer256Bit)
303 PreferVectorWidth = 256;
304}
305
306X86Subtarget &X86Subtarget::initializeSubtargetDependencies(StringRef CPU,
307 StringRef TuneCPU,
308 StringRef FS) {
309 initSubtargetFeatures(CPU, TuneCPU, FS);
310 return *this;
311}
312
314 StringRef FS, const X86TargetMachine &TM,
315 MaybeAlign StackAlignOverride,
316 unsigned PreferVectorWidthOverride,
317 unsigned RequiredVectorWidth)
318 : X86GenSubtargetInfo(TT, CPU, TuneCPU, FS),
319 PICStyle(PICStyles::Style::None), TM(TM), TargetTriple(TT),
320 StackAlignOverride(StackAlignOverride),
321 PreferVectorWidthOverride(PreferVectorWidthOverride),
322 RequiredVectorWidth(RequiredVectorWidth),
323 InstrInfo(initializeSubtargetDependencies(CPU, TuneCPU, FS)),
324 TLInfo(TM, *this), FrameLowering(*this, getStackAlignment()) {
325 // Determine the PICStyle based on the target selected.
328 else if (is64Bit())
330 else if (isTargetCOFF())
332 else if (isTargetDarwin())
334 else if (isTargetELF())
336
337 CallLoweringInfo.reset(new X86CallLowering(*getTargetLowering()));
338 Legalizer.reset(new X86LegalizerInfo(*this, TM));
339
340 auto *RBI = new X86RegisterBankInfo(*getRegisterInfo());
341 RegBankInfo.reset(RBI);
342 InstSelector.reset(createX86InstructionSelector(TM, *this, *RBI));
343}
344
346 return CallLoweringInfo.get();
347}
348
350 return InstSelector.get();
351}
352
354 return Legalizer.get();
355}
356
358 return RegBankInfo.get();
359}
360
362 return canUseCMOV() && X86EarlyIfConv;
363}
364
366 std::vector<std::unique_ptr<ScheduleDAGMutation>> &Mutations) const {
367 Mutations.push_back(createX86MacroFusionDAGMutation());
368}
369
371 return TM.isPositionIndependent();
372}
This header is deprecated in favour of llvm/TargetParser/Triple.h.
This file contains the simple types necessary to represent the attributes associated with functions a...
This file describes how to lower LLVM calls to machine code calls.
#define LLVM_DEBUG(X)
Definition: Debug.h:101
#define F(x, y, z)
Definition: MD5.cpp:55
const char LLVMTargetMachineRef TM
return InstrInfo
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This file describes how to lower LLVM calls to machine code calls.
static bool is64Bit(const char *name)
This file declares the targeting of the Machinelegalizer class for X86.
This file declares the targeting of the RegisterBankInfo class for X86.
static cl::opt< bool > X86EarlyIfConv("x86-early-ifcvt", cl::Hidden, cl::desc("Enable early if-conversion on X86"))
bool hasDLLImportStorageClass() const
Definition: GlobalValue.h:274
bool isDeclarationForLinker() const
Definition: GlobalValue.h:614
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:652
std::optional< ConstantRange > getAbsoluteSymbolRange() const
If this is an absolute symbol reference, returns the range of the symbol, otherwise returns std::null...
Definition: Globals.cpp:382
bool hasCommonLinkage() const
Definition: GlobalValue.h:527
Provides the logic to select generic machine instructions.
A Module instance is used to store all the information related to an LLVM module.
Definition: Module.h:65
Holds all the information related to register banks.
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
constexpr bool empty() const
empty - Check if the string is empty.
Definition: StringRef.h:134
bool isPositionIndependent() const
Reloc::Model getRelocationModel() const
Returns the code generation relocation model.
bool shouldAssumeDSOLocal(const Module &M, const GlobalValue *GV) const
CodeModel::Model getCodeModel() const
Returns the code model.
Triple - Helper class for working with autoconf configuration names.
Definition: Triple.h:44
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
This class provides the information for the target register banks.
This class provides the information for the target register banks.
bool enableEarlyIfConversion() const override
bool isOSWindows() const
Definition: X86Subtarget.h:322
bool isTargetKFreeBSD() const
Definition: X86Subtarget.h:291
bool hasSSE42() const
Definition: X86Subtarget.h:204
InstructionSelector * getInstructionSelector() const override
const X86TargetLowering * getTargetLowering() const override
Definition: X86Subtarget.h:124
bool canUseCMOV() const
Definition: X86Subtarget.h:198
bool isLegalToCallImmediateAddr() const
Return true if the subtarget allows calls to immediate address.
bool isTargetDarwin() const
Definition: X86Subtarget.h:280
const RegisterBankInfo * getRegBankInfo() const override
bool isTargetCOFF() const
Definition: X86Subtarget.h:287
bool isTargetNaCl() const
Definition: X86Subtarget.h:294
bool isTargetELF() const
Definition: X86Subtarget.h:286
unsigned char classifyGlobalReference(const GlobalValue *GV, const Module &M) const
const LegalizerInfo * getLegalizerInfo() const override
bool isPositionIndependent() const
unsigned char classifyLocalReference(const GlobalValue *GV) const
Classify a global variable reference for the current subtarget according to how we should reference i...
unsigned char classifyBlockAddressReference() const
Classify a blockaddress reference for the current subtarget according to how we should reference it i...
const X86RegisterInfo * getRegisterInfo() const override
Definition: X86Subtarget.h:138
void setPICStyle(PICStyles::Style Style)
Definition: X86Subtarget.h:189
X86Subtarget(const Triple &TT, StringRef CPU, StringRef TuneCPU, StringRef FS, const X86TargetMachine &TM, MaybeAlign StackAlignOverride, unsigned PreferVectorWidthOverride, unsigned RequiredVectorWidth)
This constructor initializes the data members to match that of the specified triple.
const CallLowering * getCallLowering() const override
Methods used by Global ISel.
void ParseSubtargetFeatures(StringRef CPU, StringRef TuneCPU, StringRef FS)
ParseSubtargetFeatures - Parses features string setting specified subtarget options.
void getPostRAMutations(std::vector< std::unique_ptr< ScheduleDAGMutation > > &Mutations) const override
bool isTargetWin32() const
Definition: X86Subtarget.h:326
unsigned char classifyGlobalFunctionReference(const GlobalValue *GV, const Module &M) const
Classify a global function reference for the current subtarget.
bool isTargetLinux() const
Definition: X86Subtarget.h:290
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
@ X86_RegCall
Register calling convention used for parameters transfer optimization.
Definition: CallingConv.h:204
@ MO_GOTPCREL_NORELAX
MO_GOTPCREL_NORELAX - Same as MO_GOTPCREL except that R_X86_64_GOTPCREL relocations are guaranteed to...
Definition: X86BaseInfo.h:447
@ MO_GOTOFF
MO_GOTOFF - On a symbol operand this indicates that the immediate is the offset to the location of th...
Definition: X86BaseInfo.h:434
@ MO_DARWIN_NONLAZY_PIC_BASE
MO_DARWIN_NONLAZY_PIC_BASE - On a symbol operand "FOO", this indicates that the reference is actually...
Definition: X86BaseInfo.h:547
@ MO_COFFSTUB
MO_COFFSTUB - On a symbol operand "FOO", this indicates that the reference is actually to the "....
Definition: X86BaseInfo.h:575
@ MO_DARWIN_NONLAZY
MO_DARWIN_NONLAZY - On a symbol operand "FOO", this indicates that the reference is actually to the "...
Definition: X86BaseInfo.h:542
@ MO_GOT
MO_GOT - On a symbol operand this indicates that the immediate is the offset to the GOT entry for the...
Definition: X86BaseInfo.h:427
@ MO_ABS8
MO_ABS8 - On a symbol operand this indicates that the symbol is known to be an absolute symbol in ran...
Definition: X86BaseInfo.h:570
@ MO_PLT
MO_PLT - On a symbol operand this indicates that the immediate is offset to the PLT entry of symbol n...
Definition: X86BaseInfo.h:454
@ MO_DLLIMPORT
MO_DLLIMPORT - On a symbol operand "FOO", this indicates that the reference is actually to the "__imp...
Definition: X86BaseInfo.h:537
@ MO_PIC_BASE_OFFSET
MO_PIC_BASE_OFFSET - On a symbol operand this indicates that the immediate should get the value of th...
Definition: X86BaseInfo.h:420
@ MO_GOTPCREL
MO_GOTPCREL - On a symbol operand this indicates that the immediate is offset to the GOT entry for th...
Definition: X86BaseInfo.h:442
std::string ParseX86Triple(const Triple &TT)
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
InstructionSelector * createX86InstructionSelector(const X86TargetMachine &TM, X86Subtarget &, X86RegisterBankInfo &)
std::unique_ptr< ScheduleDAGMutation > createX86MacroFusionDAGMutation()
Note that you have to add: DAG.addMutation(createX86MacroFusionDAGMutation()); to X86PassConfig::crea...
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:163
void report_fatal_error(Error Err, bool gen_crash_diag=true)
Report a serious error, calling any installed error handler.
Definition: Error.cpp:145
constexpr std::nullopt_t None
Definition: None.h:28
This struct is a compact representation of a valid (non-zero power of two) alignment.
Definition: Alignment.h:39
This struct is a compact representation of a valid (power of two) or undefined (0) alignment.
Definition: Alignment.h:117