LLVM 19.0.0git
HexagonTargetObjectFile.cpp
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1//===-- HexagonTargetObjectFile.cpp ---------------------------------------===//
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 contains the declarations of the HexagonTargetAsmInfo properties.
10//
11//===----------------------------------------------------------------------===//
12
15#include "llvm/ADT/StringRef.h"
16#include "llvm/ADT/Twine.h"
18#include "llvm/IR/DataLayout.h"
21#include "llvm/IR/GlobalValue.h"
23#include "llvm/IR/Module.h"
24#include "llvm/IR/Type.h"
25#include "llvm/MC/MCContext.h"
26#include "llvm/MC/SectionKind.h"
29#include "llvm/Support/Debug.h"
32
33#define DEBUG_TYPE "hexagon-sdata"
34
35using namespace llvm;
36
37static cl::opt<unsigned> SmallDataThreshold("hexagon-small-data-threshold",
39 cl::desc("The maximum size of an object in the sdata section"));
40
41static cl::opt<bool> NoSmallDataSorting("mno-sort-sda", cl::init(false),
42 cl::Hidden, cl::desc("Disable small data sections sorting"));
43
44static cl::opt<bool>
45 StaticsInSData("hexagon-statics-in-small-data", cl::Hidden,
46 cl::desc("Allow static variables in .sdata"));
47
48static cl::opt<bool> TraceGVPlacement("trace-gv-placement",
49 cl::Hidden, cl::init(false),
50 cl::desc("Trace global value placement"));
51
52static cl::opt<bool>
53 EmitJtInText("hexagon-emit-jt-text", cl::Hidden, cl::init(false),
54 cl::desc("Emit hexagon jump tables in function section"));
55
56static cl::opt<bool>
57 EmitLutInText("hexagon-emit-lut-text", cl::Hidden, cl::init(false),
58 cl::desc("Emit hexagon lookup tables in function section"));
59
60// TraceGVPlacement controls messages for all builds. For builds with assertions
61// (debug or release), messages are also controlled by the usual debug flags
62// (e.g. -debug and -debug-only=globallayout)
63#define TRACE_TO(s, X) s << X
64#ifdef NDEBUG
65#define TRACE(X) \
66 do { \
67 if (TraceGVPlacement) { \
68 TRACE_TO(errs(), X); \
69 } \
70 } while (false)
71#else
72#define TRACE(X) \
73 do { \
74 if (TraceGVPlacement) { \
75 TRACE_TO(errs(), X); \
76 } else { \
77 LLVM_DEBUG(TRACE_TO(dbgs(), X)); \
78 } \
79 } while (false)
80#endif
81
82// Returns true if the section name is such that the symbol will be put
83// in a small data section.
84// For instance, global variables with section attributes such as ".sdata"
85// ".sdata.*", ".sbss", and ".sbss.*" will go into small data.
86static bool isSmallDataSection(StringRef Sec) {
87 // sectionName is either ".sdata" or ".sbss". Looking for an exact match
88 // obviates the need for checks for section names such as ".sdatafoo".
89 if (Sec == ".sdata" || Sec == ".sbss" || Sec == ".scommon")
90 return true;
91 // If either ".sdata." or ".sbss." is a substring of the section name
92 // then put the symbol in small data.
93 return Sec.contains(".sdata.") || Sec.contains(".sbss.") ||
94 Sec.contains(".scommon.");
95}
96
97static const char *getSectionSuffixForSize(unsigned Size) {
98 switch (Size) {
99 default:
100 return "";
101 case 1:
102 return ".1";
103 case 2:
104 return ".2";
105 case 4:
106 return ".4";
107 case 8:
108 return ".8";
109 }
110}
111
113 const TargetMachine &TM) {
115
116 SmallDataSection =
120 SmallBSSSection =
124}
125
127 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
128 TRACE("[SelectSectionForGlobal] GO(" << GO->getName() << ") ");
129 TRACE("input section(" << GO->getSection() << ") ");
130
131 TRACE((GO->hasPrivateLinkage() ? "private_linkage " : "")
132 << (GO->hasLocalLinkage() ? "local_linkage " : "")
133 << (GO->hasInternalLinkage() ? "internal " : "")
134 << (GO->hasExternalLinkage() ? "external " : "")
135 << (GO->hasCommonLinkage() ? "common_linkage " : "")
136 << (GO->hasCommonLinkage() ? "common " : "" )
137 << (Kind.isCommon() ? "kind_common " : "" )
138 << (Kind.isBSS() ? "kind_bss " : "" )
139 << (Kind.isBSSLocal() ? "kind_bss_local " : "" ));
140
141 // If the lookup table is used by more than one function, do not place
142 // it in text section.
143 if (EmitLutInText && GO->getName().starts_with("switch.table")) {
144 if (const Function *Fn = getLutUsedFunction(GO))
145 return selectSectionForLookupTable(GO, TM, Fn);
146 }
147
148 if (isGlobalInSmallSection(GO, TM))
149 return selectSmallSectionForGlobal(GO, Kind, TM);
150
151 if (Kind.isCommon()) {
152 // This is purely for LTO+Linker Script because commons don't really have a
153 // section. However, the BitcodeSectionWriter pass will query for the
154 // sections of commons (and the linker expects us to know their section) so
155 // we'll return one here.
156 return BSSSection;
157 }
158
159 TRACE("default_ELF_section\n");
160 // Otherwise, we work the same as ELF.
162}
163
165 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
166 TRACE("[getExplicitSectionGlobal] GO(" << GO->getName() << ") from("
167 << GO->getSection() << ") ");
168 TRACE((GO->hasPrivateLinkage() ? "private_linkage " : "")
169 << (GO->hasLocalLinkage() ? "local_linkage " : "")
170 << (GO->hasInternalLinkage() ? "internal " : "")
171 << (GO->hasExternalLinkage() ? "external " : "")
172 << (GO->hasCommonLinkage() ? "common_linkage " : "")
173 << (GO->hasCommonLinkage() ? "common " : "" )
174 << (Kind.isCommon() ? "kind_common " : "" )
175 << (Kind.isBSS() ? "kind_bss " : "" )
176 << (Kind.isBSSLocal() ? "kind_bss_local " : "" ));
177
178 if (GO->hasSection()) {
179 StringRef Section = GO->getSection();
180 if (Section.contains(".access.text.group"))
183 if (Section.contains(".access.data.group"))
186 }
187
188 if (isGlobalInSmallSection(GO, TM))
189 return selectSmallSectionForGlobal(GO, Kind, TM);
190
191 // Otherwise, we work the same as ELF.
192 TRACE("default_ELF_section\n");
194}
195
196/// Return true if this global value should be placed into small data/bss
197/// section.
199 const TargetMachine &TM) const {
200 bool HaveSData = isSmallDataEnabled(TM);
201 if (!HaveSData)
202 LLVM_DEBUG(dbgs() << "Small-data allocation is disabled, but symbols "
203 "may have explicit section assignments...\n");
204 // Only global variables, not functions.
205 LLVM_DEBUG(dbgs() << "Checking if value is in small-data, -G"
206 << SmallDataThreshold << ": \"" << GO->getName() << "\": ");
207 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GO);
208 if (!GVar) {
209 LLVM_DEBUG(dbgs() << "no, not a global variable\n");
210 return false;
211 }
212
213 // Globals with external linkage that have an original section set must be
214 // emitted to that section, regardless of whether we would put them into
215 // small data or not. This is how we can support mixing -G0/-G8 in LTO.
216 if (GVar->hasSection()) {
217 bool IsSmall = isSmallDataSection(GVar->getSection());
218 LLVM_DEBUG(dbgs() << (IsSmall ? "yes" : "no")
219 << ", has section: " << GVar->getSection() << '\n');
220 return IsSmall;
221 }
222
223 // If sdata is disabled, stop the checks here.
224 if (!HaveSData) {
225 LLVM_DEBUG(dbgs() << "no, small-data allocation is disabled\n");
226 return false;
227 }
228
229 if (GVar->isConstant()) {
230 LLVM_DEBUG(dbgs() << "no, is a constant\n");
231 return false;
232 }
233
234 bool IsLocal = GVar->hasLocalLinkage();
235 if (!StaticsInSData && IsLocal) {
236 LLVM_DEBUG(dbgs() << "no, is static\n");
237 return false;
238 }
239
240 Type *GType = GVar->getValueType();
241 if (isa<ArrayType>(GType)) {
242 LLVM_DEBUG(dbgs() << "no, is an array\n");
243 return false;
244 }
245
246 // If the type is a struct with no body provided, treat is conservatively.
247 // There cannot be actual definitions of object of such a type in this CU
248 // (only references), so assuming that they are not in sdata is safe. If
249 // these objects end up in the sdata, the references will still be valid.
250 if (StructType *ST = dyn_cast<StructType>(GType)) {
251 if (ST->isOpaque()) {
252 LLVM_DEBUG(dbgs() << "no, has opaque type\n");
253 return false;
254 }
255 }
256
257 unsigned Size = GVar->getParent()->getDataLayout().getTypeAllocSize(GType);
258 if (Size == 0) {
259 LLVM_DEBUG(dbgs() << "no, has size 0\n");
260 return false;
261 }
262 if (Size > SmallDataThreshold) {
263 LLVM_DEBUG(dbgs() << "no, size exceeds sdata threshold: " << Size << '\n');
264 return false;
265 }
266
267 LLVM_DEBUG(dbgs() << "yes\n");
268 return true;
269}
270
272 const {
274}
275
277 return SmallDataThreshold;
278}
279
281 bool UsesLabelDifference, const Function &F) const {
282 return EmitJtInText;
283}
284
285/// Descends any type down to "elementary" components,
286/// discovering the smallest addressable one.
287/// If zero is returned, declaration will not be modified.
288unsigned HexagonTargetObjectFile::getSmallestAddressableSize(const Type *Ty,
289 const GlobalValue *GV, const TargetMachine &TM) const {
290 // Assign the smallest element access size to the highest
291 // value which assembler can handle.
292 unsigned SmallestElement = 8;
293
294 if (!Ty)
295 return 0;
296 switch (Ty->getTypeID()) {
297 case Type::StructTyID: {
298 const StructType *STy = cast<const StructType>(Ty);
299 for (auto &E : STy->elements()) {
300 unsigned AtomicSize = getSmallestAddressableSize(E, GV, TM);
301 if (AtomicSize < SmallestElement)
302 SmallestElement = AtomicSize;
303 }
304 return (STy->getNumElements() == 0) ? 0 : SmallestElement;
305 }
306 case Type::ArrayTyID: {
307 const ArrayType *ATy = cast<const ArrayType>(Ty);
308 return getSmallestAddressableSize(ATy->getElementType(), GV, TM);
309 }
312 const VectorType *PTy = cast<const VectorType>(Ty);
313 return getSmallestAddressableSize(PTy->getElementType(), GV, TM);
314 }
316 case Type::HalfTyID:
317 case Type::FloatTyID:
318 case Type::DoubleTyID:
319 case Type::IntegerTyID: {
320 const DataLayout &DL = GV->getParent()->getDataLayout();
321 // It is unfortunate that DL's function take non-const Type*.
322 return DL.getTypeAllocSize(const_cast<Type*>(Ty));
323 }
325 case Type::VoidTyID:
326 case Type::BFloatTyID:
328 case Type::FP128TyID:
330 case Type::LabelTyID:
334 case Type::TokenTyID:
337 return 0;
338 }
339
340 return 0;
341}
342
343MCSection *HexagonTargetObjectFile::selectSmallSectionForGlobal(
344 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
345 const Type *GTy = GO->getValueType();
346 unsigned Size = getSmallestAddressableSize(GTy, GO, TM);
347
348 // If we have -ffunction-section or -fdata-section then we should emit the
349 // global value to a unique section specifically for it... even for sdata.
350 bool EmitUniquedSection = TM.getDataSections();
351
352 TRACE("Small data. Size(" << Size << ")");
353 // Handle Small Section classification here.
354 if (Kind.isBSS() || Kind.isBSSLocal()) {
355 // If -mno-sort-sda is not set, find out smallest accessible entity in
356 // declaration and add it to the section name string.
357 // Note. It does not track the actual usage of the value, only its de-
358 // claration. Also, compiler adds explicit pad fields to some struct
359 // declarations - they are currently counted towards smallest addres-
360 // sable entity.
361 if (NoSmallDataSorting) {
362 TRACE(" default sbss\n");
363 return SmallBSSSection;
364 }
365
366 StringRef Prefix(".sbss");
367 SmallString<128> Name(Prefix);
369
370 if (EmitUniquedSection) {
371 Name.append(".");
372 Name.append(GO->getName());
373 }
374 TRACE(" unique sbss(" << Name << ")\n");
377 }
378
379 if (Kind.isCommon()) {
380 // This is purely for LTO+Linker Script because commons don't really have a
381 // section. However, the BitcodeSectionWriter pass will query for the
382 // sections of commons (and the linker expects us to know their section) so
383 // we'll return one here.
385 return BSSSection;
386
388 TRACE(" small COMMON (" << Name << ")\n");
389
393 }
394
395 // We could have changed sdata object to a constant... in this
396 // case the Kind could be wrong for it.
397 if (Kind.isMergeableConst()) {
398 TRACE(" const_object_as_data ");
399 const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GO);
400 if (GVar->hasSection() && isSmallDataSection(GVar->getSection()))
402 }
403
404 if (Kind.isData()) {
405 if (NoSmallDataSorting) {
406 TRACE(" default sdata\n");
407 return SmallDataSection;
408 }
409
410 StringRef Prefix(".sdata");
411 SmallString<128> Name(Prefix);
413
414 if (EmitUniquedSection) {
415 Name.append(".");
416 Name.append(GO->getName());
417 }
418 TRACE(" unique sdata(" << Name << ")\n");
421 }
422
423 TRACE("default ELF section\n");
424 // Otherwise, we work the same as ELF.
426}
427
428// Return the function that uses the lookup table. If there are more
429// than one live function that uses this look table, bail out and place
430// the lookup table in default section.
431const Function *
433 const Function *ReturnFn = nullptr;
434 for (const auto *U : GO->users()) {
435 // validate each instance of user to be a live function.
436 auto *I = dyn_cast<Instruction>(U);
437 if (!I)
438 continue;
439 auto *Bb = I->getParent();
440 if (!Bb)
441 continue;
442 auto *UserFn = Bb->getParent();
443 if (!ReturnFn)
444 ReturnFn = UserFn;
445 else if (ReturnFn != UserFn)
446 return nullptr;
447 }
448 return ReturnFn;
449}
450
451MCSection *HexagonTargetObjectFile::selectSectionForLookupTable(
452 const GlobalObject *GO, const TargetMachine &TM, const Function *Fn) const {
453
455 // If the function has explicit section, place the lookup table in this
456 // explicit section.
457 if (Fn->hasSection())
458 return getExplicitSectionGlobal(Fn, Kind, TM);
459
460 const auto *FuncObj = dyn_cast<GlobalObject>(Fn);
461 return SelectSectionForGlobal(FuncObj, Kind, TM);
462}
MachineBasicBlock MachineBasicBlock::iterator DebugLoc DL
#define LLVM_DEBUG(X)
Definition: Debug.h:101
std::string Name
uint64_t Size
static cl::opt< bool > TraceGVPlacement("trace-gv-placement", cl::Hidden, cl::init(false), cl::desc("Trace global value placement"))
static cl::opt< bool > EmitJtInText("hexagon-emit-jt-text", cl::Hidden, cl::init(false), cl::desc("Emit hexagon jump tables in function section"))
static cl::opt< unsigned > SmallDataThreshold("hexagon-small-data-threshold", cl::init(8), cl::Hidden, cl::desc("The maximum size of an object in the sdata section"))
static cl::opt< bool > StaticsInSData("hexagon-statics-in-small-data", cl::Hidden, cl::desc("Allow static variables in .sdata"))
#define TRACE(X)
static const char * getSectionSuffixForSize(unsigned Size)
static cl::opt< bool > EmitLutInText("hexagon-emit-lut-text", cl::Hidden, cl::init(false), cl::desc("Emit hexagon lookup tables in function section"))
static cl::opt< bool > NoSmallDataSorting("mno-sort-sda", cl::init(false), cl::Hidden, cl::desc("Disable small data sections sorting"))
static bool isSmallDataSection(StringRef Sec)
#define F(x, y, z)
Definition: MD5.cpp:55
#define I(x, y, z)
Definition: MD5.cpp:58
Module.h This file contains the declarations for the Module class.
const char LLVMTargetMachineRef TM
This file defines the SmallString class.
A parsed version of the target data layout string in and methods for querying it.
Definition: DataLayout.h:110
TypeSize getTypeAllocSize(Type *Ty) const
Returns the offset in bytes between successive objects of the specified type, including alignment pad...
Definition: DataLayout.h:504
StringRef getSection() const
Get the custom section of this global if it has one.
Definition: GlobalObject.h:118
bool hasSection() const
Check if this global has a custom object file section.
Definition: GlobalObject.h:110
bool hasExternalLinkage() const
Definition: GlobalValue.h:510
bool hasLocalLinkage() const
Definition: GlobalValue.h:527
bool hasPrivateLinkage() const
Definition: GlobalValue.h:526
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:655
bool hasInternalLinkage() const
Definition: GlobalValue.h:525
bool hasCommonLinkage() const
Definition: GlobalValue.h:531
Type * getValueType() const
Definition: GlobalValue.h:295
bool isConstant() const
If the value is a global constant, its value is immutable throughout the runtime execution of the pro...
bool shouldPutJumpTableInFunctionSection(bool UsesLabelDifference, const Function &F) const override
bool isSmallDataEnabled(const TargetMachine &TM) const
void Initialize(MCContext &Ctx, const TargetMachine &TM) override
This method must be called before any actual lowering is done.
bool isGlobalInSmallSection(const GlobalObject *GO, const TargetMachine &TM) const
Return true if this global value should be placed into small data/bss section.
MCSection * SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const override
MCSection * getExplicitSectionGlobal(const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const override
Targets should implement this method to assign a section to globals with an explicit section specfied...
const Function * getLutUsedFunction(const GlobalObject *GO) const
Context object for machine code objects.
Definition: MCContext.h:81
MCSectionELF * getELFSection(const Twine &Section, unsigned Type, unsigned Flags)
Definition: MCContext.h:562
MCSection * BSSSection
Section that is default initialized to zero.
MCContext & getContext() const
Instances of this class represent a uniqued identifier for a section in the current translation unit.
Definition: MCSection.h:39
const DataLayout & getDataLayout() const
Get the data layout for the module's target platform.
Definition: Module.h:293
SectionKind - This is a simple POD value that classifies the properties of a section.
Definition: SectionKind.h:22
static SectionKind getText()
Definition: SectionKind.h:190
static SectionKind getData()
Definition: SectionKind.h:213
SmallString - A SmallString is just a SmallVector with methods and accessors that make it work better...
Definition: SmallString.h:26
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
bool starts_with(StringRef Prefix) const
Check if this string starts with the given Prefix.
Definition: StringRef.h:258
bool contains(StringRef Other) const
Return true if the given string is a substring of *this, and false otherwise.
Definition: StringRef.h:417
Class to represent struct types.
Definition: DerivedTypes.h:216
ArrayRef< Type * > elements() const
Definition: DerivedTypes.h:333
unsigned getNumElements() const
Random access to the elements.
Definition: DerivedTypes.h:341
void Initialize(MCContext &Ctx, const TargetMachine &TM) override
This method must be called before any actual lowering is done.
MCSection * SelectSectionForGlobal(const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const override
MCSection * getExplicitSectionGlobal(const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const override
Targets should implement this method to assign a section to globals with an explicit section specfied...
Primary interface to the complete machine description for the target machine.
Definition: TargetMachine.h:76
bool isPositionIndependent() const
bool getDataSections() const
Return true if data objects should be emitted into their own section, corresponds to -fdata-sections.
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
The instances of the Type class are immutable: once they are created, they are never changed.
Definition: Type.h:45
@ X86_MMXTyID
MMX vectors (64 bits, X86 specific)
Definition: Type.h:66
@ X86_AMXTyID
AMX vectors (8192 bits, X86 specific)
Definition: Type.h:67
@ FunctionTyID
Functions.
Definition: Type.h:72
@ ArrayTyID
Arrays.
Definition: Type.h:75
@ TypedPointerTyID
Typed pointer used by some GPU targets.
Definition: Type.h:78
@ HalfTyID
16-bit floating point type
Definition: Type.h:56
@ TargetExtTyID
Target extension type.
Definition: Type.h:79
@ VoidTyID
type with no size
Definition: Type.h:63
@ ScalableVectorTyID
Scalable SIMD vector type.
Definition: Type.h:77
@ LabelTyID
Labels.
Definition: Type.h:64
@ FloatTyID
32-bit floating point type
Definition: Type.h:58
@ StructTyID
Structures.
Definition: Type.h:74
@ IntegerTyID
Arbitrary bit width integers.
Definition: Type.h:71
@ FixedVectorTyID
Fixed width SIMD vector type.
Definition: Type.h:76
@ BFloatTyID
16-bit floating point type (7-bit significand)
Definition: Type.h:57
@ DoubleTyID
64-bit floating point type
Definition: Type.h:59
@ X86_FP80TyID
80-bit floating point type (X87)
Definition: Type.h:60
@ PPC_FP128TyID
128-bit floating point type (two 64-bits, PowerPC)
Definition: Type.h:62
@ MetadataTyID
Metadata.
Definition: Type.h:65
@ TokenTyID
Tokens.
Definition: Type.h:68
@ PointerTyID
Pointers.
Definition: Type.h:73
@ FP128TyID
128-bit floating point type (112-bit significand)
Definition: Type.h:61
TypeID getTypeID() const
Return the type id for the type.
Definition: Type.h:137
iterator_range< user_iterator > users()
Definition: Value.h:421
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:309
@ SHF_ALLOC
Definition: ELF.h:1159
@ SHF_HEX_GPREL
Definition: ELF.h:1226
@ SHF_WRITE
Definition: ELF.h:1156
@ SHF_EXECINSTR
Definition: ELF.h:1162
@ SHT_PROGBITS
Definition: ELF.h:1065
@ SHT_NOBITS
Definition: ELF.h:1072
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:450
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:163