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IRForTarget.cpp
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1//===-- IRForTarget.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#include "IRForTarget.h"
10
12#include "ClangUtil.h"
13
15#include "llvm/IR/Constants.h"
16#include "llvm/IR/DataLayout.h"
17#include "llvm/IR/Operator.h"
18#include "llvm/IR/InstrTypes.h"
19#include "llvm/IR/Instructions.h"
20#include "llvm/IR/Intrinsics.h"
21#include "llvm/IR/LegacyPassManager.h"
22#include "llvm/IR/Metadata.h"
23#include "llvm/IR/Module.h"
24#include "llvm/IR/ValueSymbolTable.h"
25#include "llvm/Support/raw_ostream.h"
26#include "llvm/Transforms/IPO.h"
27
28#include "clang/AST/ASTContext.h"
29
30#include "lldb/Core/dwarf.h"
36#include "lldb/Utility/Endian.h"
38#include "lldb/Utility/Log.h"
39#include "lldb/Utility/Scalar.h"
41
42#include <map>
43#include <optional>
44
45using namespace llvm;
47
48typedef SmallVector<Instruction *, 2> InstrList;
49
51 : m_maker(maker), m_values() {}
52
54
55llvm::Value *
57 if (!m_values.count(function)) {
58 llvm::Value *ret = m_maker(function);
59 m_values[function] = ret;
60 return ret;
61 }
62 return m_values[function];
63}
64
65static llvm::Value *FindEntryInstruction(llvm::Function *function) {
66 if (function->empty())
67 return nullptr;
68
69 return function->getEntryBlock().getFirstNonPHIOrDbg();
70}
71
73 bool resolve_vars,
74 lldb_private::IRExecutionUnit &execution_unit,
75 lldb_private::Stream &error_stream,
76 const char *func_name)
77 : m_resolve_vars(resolve_vars), m_func_name(func_name),
78 m_decl_map(decl_map), m_error_stream(error_stream),
79 m_execution_unit(execution_unit),
81
82/* Handy utility functions used at several places in the code */
83
84static std::string PrintValue(const Value *value, bool truncate = false) {
85 std::string s;
86 if (value) {
87 raw_string_ostream rso(s);
88 value->print(rso);
89 rso.flush();
90 if (truncate)
91 s.resize(s.length() - 1);
92 }
93 return s;
94}
95
96static std::string PrintType(const llvm::Type *type, bool truncate = false) {
97 std::string s;
98 raw_string_ostream rso(s);
99 type->print(rso);
100 rso.flush();
101 if (truncate)
102 s.resize(s.length() - 1);
103 return s;
104}
105
106bool IRForTarget::FixFunctionLinkage(llvm::Function &llvm_function) {
107 llvm_function.setLinkage(GlobalValue::ExternalLinkage);
108
109 return true;
110}
111
112clang::NamedDecl *IRForTarget::DeclForGlobal(const GlobalValue *global_val,
113 Module *module) {
114 NamedMDNode *named_metadata =
115 module->getNamedMetadata("clang.global.decl.ptrs");
116
117 if (!named_metadata)
118 return nullptr;
119
120 unsigned num_nodes = named_metadata->getNumOperands();
121 unsigned node_index;
122
123 for (node_index = 0; node_index < num_nodes; ++node_index) {
124 llvm::MDNode *metadata_node =
125 dyn_cast<llvm::MDNode>(named_metadata->getOperand(node_index));
126 if (!metadata_node)
127 return nullptr;
128
129 if (metadata_node->getNumOperands() != 2)
130 continue;
131
132 if (mdconst::dyn_extract_or_null<GlobalValue>(
133 metadata_node->getOperand(0)) != global_val)
134 continue;
135
136 ConstantInt *constant_int =
137 mdconst::dyn_extract<ConstantInt>(metadata_node->getOperand(1));
138
139 if (!constant_int)
140 return nullptr;
141
142 uintptr_t ptr = constant_int->getZExtValue();
143
144 return reinterpret_cast<clang::NamedDecl *>(ptr);
145 }
146
147 return nullptr;
148}
149
150clang::NamedDecl *IRForTarget::DeclForGlobal(GlobalValue *global_val) {
151 return DeclForGlobal(global_val, m_module);
152}
153
154/// Returns true iff the mangled symbol is for a static guard variable.
155static bool isGuardVariableSymbol(llvm::StringRef mangled_symbol,
156 bool check_ms_abi = true) {
157 bool result = mangled_symbol.startswith("_ZGV"); // Itanium ABI guard variable
158 if (check_ms_abi)
159 result |= mangled_symbol.endswith("@4IA"); // Microsoft ABI
160 return result;
161}
162
163bool IRForTarget::CreateResultVariable(llvm::Function &llvm_function) {
164 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
165
166 if (!m_resolve_vars)
167 return true;
168
169 // Find the result variable. If it doesn't exist, we can give up right here.
170
171 ValueSymbolTable &value_symbol_table = m_module->getValueSymbolTable();
172
173 llvm::StringRef result_name;
174 bool found_result = false;
175
176 for (StringMapEntry<llvm::Value *> &value_symbol : value_symbol_table) {
177 result_name = value_symbol.first();
178
179 // Check if this is a guard variable. It seems this causes some hiccups
180 // on Windows, so let's only check for Itanium guard variables.
181 bool is_guard_var = isGuardVariableSymbol(result_name, /*MS ABI*/ false);
182
183 if (result_name.contains("$__lldb_expr_result_ptr") && !is_guard_var) {
184 found_result = true;
185 m_result_is_pointer = true;
186 break;
187 }
188
189 if (result_name.contains("$__lldb_expr_result") && !is_guard_var) {
190 found_result = true;
191 m_result_is_pointer = false;
192 break;
193 }
194 }
195
196 if (!found_result) {
197 LLDB_LOG(log, "Couldn't find result variable");
198
199 return true;
200 }
201
202 LLDB_LOG(log, "Result name: \"{0}\"", result_name);
203
204 Value *result_value = m_module->getNamedValue(result_name);
205
206 if (!result_value) {
207 LLDB_LOG(log, "Result variable had no data");
208
209 m_error_stream.Format("Internal error [IRForTarget]: Result variable's "
210 "name ({0}) exists, but not its definition\n",
211 result_name);
212
213 return false;
214 }
215
216 LLDB_LOG(log, "Found result in the IR: \"{0}\"",
217 PrintValue(result_value, false));
218
219 GlobalVariable *result_global = dyn_cast<GlobalVariable>(result_value);
220
221 if (!result_global) {
222 LLDB_LOG(log, "Result variable isn't a GlobalVariable");
223
224 m_error_stream.Format("Internal error [IRForTarget]: Result variable ({0}) "
225 "is defined, but is not a global variable\n",
226 result_name);
227
228 return false;
229 }
230
231 clang::NamedDecl *result_decl = DeclForGlobal(result_global);
232 if (!result_decl) {
233 LLDB_LOG(log, "Result variable doesn't have a corresponding Decl");
234
235 m_error_stream.Format("Internal error [IRForTarget]: Result variable ({0}) "
236 "does not have a corresponding Clang entity\n",
237 result_name);
238
239 return false;
240 }
241
242 if (log) {
243 std::string decl_desc_str;
244 raw_string_ostream decl_desc_stream(decl_desc_str);
245 result_decl->print(decl_desc_stream);
246 decl_desc_stream.flush();
247
248 LLDB_LOG(log, "Found result decl: \"{0}\"", decl_desc_str);
249 }
250
251 clang::VarDecl *result_var = dyn_cast<clang::VarDecl>(result_decl);
252 if (!result_var) {
253 LLDB_LOG(log, "Result variable Decl isn't a VarDecl");
254
255 m_error_stream.Format("Internal error [IRForTarget]: Result variable "
256 "({0})'s corresponding Clang entity isn't a "
257 "variable\n",
258 result_name);
259
260 return false;
261 }
262
263 // Get the next available result name from m_decl_map and create the
264 // persistent variable for it
265
266 // If the result is an Lvalue, it is emitted as a pointer; see
267 // ASTResultSynthesizer::SynthesizeBodyResult.
269 clang::QualType pointer_qual_type = result_var->getType();
270 const clang::Type *pointer_type = pointer_qual_type.getTypePtr();
271
272 const clang::PointerType *pointer_pointertype =
273 pointer_type->getAs<clang::PointerType>();
274 const clang::ObjCObjectPointerType *pointer_objcobjpointertype =
275 pointer_type->getAs<clang::ObjCObjectPointerType>();
276
277 if (pointer_pointertype) {
278 clang::QualType element_qual_type = pointer_pointertype->getPointeeType();
279
281 m_decl_map->GetTypeSystem()->GetType(element_qual_type));
282 } else if (pointer_objcobjpointertype) {
283 clang::QualType element_qual_type =
284 clang::QualType(pointer_objcobjpointertype->getObjectType(), 0);
285
287 m_decl_map->GetTypeSystem()->GetType(element_qual_type));
288 } else {
289 LLDB_LOG(log, "Expected result to have pointer type, but it did not");
290
291 m_error_stream.Format("Internal error [IRForTarget]: Lvalue result ({0}) "
292 "is not a pointer variable\n",
293 result_name);
294
295 return false;
296 }
297 } else {
299 m_decl_map->GetTypeSystem()->GetType(result_var->getType()));
300 }
301
303 std::optional<uint64_t> bit_size = m_result_type.GetBitSize(target_sp.get());
304 if (!bit_size) {
305 lldb_private::StreamString type_desc_stream;
306 m_result_type.DumpTypeDescription(&type_desc_stream);
307
308 LLDB_LOG(log, "Result type has unknown size");
309
310 m_error_stream.Printf("Error [IRForTarget]: Size of result type '%s' "
311 "couldn't be determined\n",
312 type_desc_stream.GetData());
313 return false;
314 }
315
316 if (log) {
317 lldb_private::StreamString type_desc_stream;
318 m_result_type.DumpTypeDescription(&type_desc_stream);
319
320 LLDB_LOG(log, "Result decl type: \"{0}\"", type_desc_stream.GetData());
321 }
322
324
325 LLDB_LOG(log, "Creating a new result global: \"{0}\" with size {1}",
327 m_result_type.GetByteSize(target_sp.get()).value_or(0));
328
329 // Construct a new result global and set up its metadata
330
331 GlobalVariable *new_result_global = new GlobalVariable(
332 (*m_module), result_global->getValueType(), false, /* not constant */
333 GlobalValue::ExternalLinkage, nullptr, /* no initializer */
335
336 // It's too late in compilation to create a new VarDecl for this, but we
337 // don't need to. We point the metadata at the old VarDecl. This creates an
338 // odd anomaly: a variable with a Value whose name is something like $0 and a
339 // Decl whose name is $__lldb_expr_result. This condition is handled in
340 // ClangExpressionDeclMap::DoMaterialize, and the name of the variable is
341 // fixed up.
342
343 ConstantInt *new_constant_int =
344 ConstantInt::get(llvm::Type::getInt64Ty(m_module->getContext()),
345 reinterpret_cast<uintptr_t>(result_decl), false);
346
347 llvm::Metadata *values[2];
348 values[0] = ConstantAsMetadata::get(new_result_global);
349 values[1] = ConstantAsMetadata::get(new_constant_int);
350
351 ArrayRef<Metadata *> value_ref(values, 2);
352
353 MDNode *persistent_global_md = MDNode::get(m_module->getContext(), value_ref);
354 NamedMDNode *named_metadata =
355 m_module->getNamedMetadata("clang.global.decl.ptrs");
356 named_metadata->addOperand(persistent_global_md);
357
358 LLDB_LOG(log, "Replacing \"{0}\" with \"{1}\"", PrintValue(result_global),
359 PrintValue(new_result_global));
360
361 if (result_global->use_empty()) {
362 // We need to synthesize a store for this variable, because otherwise
363 // there's nothing to put into its equivalent persistent variable.
364
365 BasicBlock &entry_block(llvm_function.getEntryBlock());
366 Instruction *first_entry_instruction(entry_block.getFirstNonPHIOrDbg());
367
368 if (!first_entry_instruction)
369 return false;
370
371 if (!result_global->hasInitializer()) {
372 LLDB_LOG(log, "Couldn't find initializer for unused variable");
373
374 m_error_stream.Format("Internal error [IRForTarget]: Result variable "
375 "({0}) has no writes and no initializer\n",
376 result_name);
377
378 return false;
379 }
380
381 Constant *initializer = result_global->getInitializer();
382
383 StoreInst *synthesized_store =
384 new StoreInst(initializer, new_result_global, first_entry_instruction);
385
386 LLDB_LOG(log, "Synthesized result store \"{0}\"\n",
387 PrintValue(synthesized_store));
388 } else {
389 result_global->replaceAllUsesWith(new_result_global);
390 }
391
393 result_decl, m_result_name, m_result_type, true, m_result_is_pointer))
394 return false;
395
396 result_global->eraseFromParent();
397
398 return true;
399}
400
401bool IRForTarget::RewriteObjCConstString(llvm::GlobalVariable *ns_str,
402 llvm::GlobalVariable *cstr) {
403 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
404
405 Type *ns_str_ty = ns_str->getType();
406
407 Type *i8_ptr_ty = PointerType::getUnqual(m_module->getContext());
408 Type *i32_ty = Type::getInt32Ty(m_module->getContext());
409 Type *i8_ty = Type::getInt8Ty(m_module->getContext());
410
412 lldb::addr_t CFStringCreateWithBytes_addr;
413
414 static lldb_private::ConstString g_CFStringCreateWithBytes_str(
415 "CFStringCreateWithBytes");
416
417 bool missing_weak = false;
418 CFStringCreateWithBytes_addr =
419 m_execution_unit.FindSymbol(g_CFStringCreateWithBytes_str,
420 missing_weak);
421 if (CFStringCreateWithBytes_addr == LLDB_INVALID_ADDRESS || missing_weak) {
422 LLDB_LOG(log, "Couldn't find CFStringCreateWithBytes in the target");
423
424 m_error_stream.Printf("Error [IRForTarget]: Rewriting an Objective-C "
425 "constant string requires "
426 "CFStringCreateWithBytes\n");
427
428 return false;
429 }
430
431 LLDB_LOG(log, "Found CFStringCreateWithBytes at {0}",
432 CFStringCreateWithBytes_addr);
433
434 // Build the function type:
435 //
436 // CFStringRef CFStringCreateWithBytes (
437 // CFAllocatorRef alloc,
438 // const UInt8 *bytes,
439 // CFIndex numBytes,
440 // CFStringEncoding encoding,
441 // Boolean isExternalRepresentation
442 // );
443 //
444 // We make the following substitutions:
445 //
446 // CFStringRef -> i8*
447 // CFAllocatorRef -> i8*
448 // UInt8 * -> i8*
449 // CFIndex -> long (i32 or i64, as appropriate; we ask the module for its
450 // pointer size for now) CFStringEncoding -> i32 Boolean -> i8
451
452 Type *arg_type_array[5];
453
454 arg_type_array[0] = i8_ptr_ty;
455 arg_type_array[1] = i8_ptr_ty;
456 arg_type_array[2] = m_intptr_ty;
457 arg_type_array[3] = i32_ty;
458 arg_type_array[4] = i8_ty;
459
460 ArrayRef<Type *> CFSCWB_arg_types(arg_type_array, 5);
461
462 llvm::FunctionType *CFSCWB_ty =
463 FunctionType::get(ns_str_ty, CFSCWB_arg_types, false);
464
465 // Build the constant containing the pointer to the function
466 PointerType *CFSCWB_ptr_ty = PointerType::getUnqual(CFSCWB_ty);
467 Constant *CFSCWB_addr_int =
468 ConstantInt::get(m_intptr_ty, CFStringCreateWithBytes_addr, false);
470 CFSCWB_ty, ConstantExpr::getIntToPtr(CFSCWB_addr_int, CFSCWB_ptr_ty)};
471 }
472
473 ConstantDataSequential *string_array = nullptr;
474
475 if (cstr)
476 string_array = dyn_cast<ConstantDataSequential>(cstr->getInitializer());
477
478 Constant *alloc_arg = Constant::getNullValue(i8_ptr_ty);
479 Constant *bytes_arg = cstr ? cstr : Constant::getNullValue(i8_ptr_ty);
480 Constant *numBytes_arg = ConstantInt::get(
481 m_intptr_ty, cstr ? (string_array->getNumElements() - 1) * string_array->getElementByteSize() : 0, false);
482 int encoding_flags = 0;
483 switch (cstr ? string_array->getElementByteSize() : 1) {
484 case 1:
485 encoding_flags = 0x08000100; /* 0x08000100 is kCFStringEncodingUTF8 */
486 break;
487 case 2:
488 encoding_flags = 0x0100; /* 0x0100 is kCFStringEncodingUTF16 */
489 break;
490 case 4:
491 encoding_flags = 0x0c000100; /* 0x0c000100 is kCFStringEncodingUTF32 */
492 break;
493 default:
494 encoding_flags = 0x0600; /* fall back to 0x0600, kCFStringEncodingASCII */
495 LLDB_LOG(log, "Encountered an Objective-C constant string with unusual "
496 "element size {0}",
497 string_array->getElementByteSize());
498 }
499 Constant *encoding_arg = ConstantInt::get(i32_ty, encoding_flags, false);
500 Constant *isExternal_arg =
501 ConstantInt::get(i8_ty, 0x0, false); /* 0x0 is false */
502
503 Value *argument_array[5];
504
505 argument_array[0] = alloc_arg;
506 argument_array[1] = bytes_arg;
507 argument_array[2] = numBytes_arg;
508 argument_array[3] = encoding_arg;
509 argument_array[4] = isExternal_arg;
510
511 ArrayRef<Value *> CFSCWB_arguments(argument_array, 5);
512
513 FunctionValueCache CFSCWB_Caller(
514 [this, &CFSCWB_arguments](llvm::Function *function) -> llvm::Value * {
515 return CallInst::Create(
516 m_CFStringCreateWithBytes, CFSCWB_arguments,
517 "CFStringCreateWithBytes",
518 llvm::cast<Instruction>(
520 });
521
522 if (!UnfoldConstant(ns_str, nullptr, CFSCWB_Caller, m_entry_instruction_finder,
524 LLDB_LOG(log, "Couldn't replace the NSString with the result of the call");
525
526 m_error_stream.Printf("error [IRForTarget internal]: Couldn't replace an "
527 "Objective-C constant string with a dynamic "
528 "string\n");
529
530 return false;
531 }
532
533 ns_str->eraseFromParent();
534
535 return true;
536}
537
539 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
540
541 ValueSymbolTable &value_symbol_table = m_module->getValueSymbolTable();
542
543 for (StringMapEntry<llvm::Value *> &value_symbol : value_symbol_table) {
544 llvm::StringRef value_name = value_symbol.first();
545
546 if (value_name.contains("_unnamed_cfstring_")) {
547 Value *nsstring_value = value_symbol.second;
548
549 GlobalVariable *nsstring_global =
550 dyn_cast<GlobalVariable>(nsstring_value);
551
552 if (!nsstring_global) {
553 LLDB_LOG(log, "NSString variable is not a GlobalVariable");
554
555 m_error_stream.Printf("Internal error [IRForTarget]: An Objective-C "
556 "constant string is not a global variable\n");
557
558 return false;
559 }
560
561 if (!nsstring_global->hasInitializer()) {
562 LLDB_LOG(log, "NSString variable does not have an initializer");
563
564 m_error_stream.Printf("Internal error [IRForTarget]: An Objective-C "
565 "constant string does not have an initializer\n");
566
567 return false;
568 }
569
570 ConstantStruct *nsstring_struct =
571 dyn_cast<ConstantStruct>(nsstring_global->getInitializer());
572
573 if (!nsstring_struct) {
574 LLDB_LOG(log,
575 "NSString variable's initializer is not a ConstantStruct");
576
577 m_error_stream.Printf("Internal error [IRForTarget]: An Objective-C "
578 "constant string is not a structure constant\n");
579
580 return false;
581 }
582
583 // We expect the following structure:
584 //
585 // struct {
586 // int *isa;
587 // int flags;
588 // char *str;
589 // long length;
590 // };
591
592 if (nsstring_struct->getNumOperands() != 4) {
593
594 LLDB_LOG(log,
595 "NSString variable's initializer structure has an "
596 "unexpected number of members. Should be 4, is {0}",
597 nsstring_struct->getNumOperands());
598
599 m_error_stream.Printf("Internal error [IRForTarget]: The struct for an "
600 "Objective-C constant string is not as "
601 "expected\n");
602
603 return false;
604 }
605
606 Constant *nsstring_member = nsstring_struct->getOperand(2);
607
608 if (!nsstring_member) {
609 LLDB_LOG(log, "NSString initializer's str element was empty");
610
611 m_error_stream.Printf("Internal error [IRForTarget]: An Objective-C "
612 "constant string does not have a string "
613 "initializer\n");
614
615 return false;
616 }
617
618 auto *cstr_global = dyn_cast<GlobalVariable>(nsstring_member);
619 if (!cstr_global) {
620 LLDB_LOG(log,
621 "NSString initializer's str element is not a GlobalVariable");
622
623 m_error_stream.Printf("Internal error [IRForTarget]: Unhandled"
624 "constant string initializer\n");
625
626 return false;
627 }
628
629 if (!cstr_global->hasInitializer()) {
630 LLDB_LOG(log, "NSString initializer's str element does not have an "
631 "initializer");
632
633 m_error_stream.Printf("Internal error [IRForTarget]: An Objective-C "
634 "constant string's string initializer doesn't "
635 "point to initialized data\n");
636
637 return false;
638 }
639
640 /*
641 if (!cstr_array)
642 {
643 if (log)
644 log->PutCString("NSString initializer's str element is not a
645 ConstantArray");
646
647 if (m_error_stream)
648 m_error_stream.Printf("Internal error [IRForTarget]: An
649 Objective-C constant string's string initializer doesn't point to an
650 array\n");
651
652 return false;
653 }
654
655 if (!cstr_array->isCString())
656 {
657 if (log)
658 log->PutCString("NSString initializer's str element is not a C
659 string array");
660
661 if (m_error_stream)
662 m_error_stream.Printf("Internal error [IRForTarget]: An
663 Objective-C constant string's string initializer doesn't point to a C
664 string\n");
665
666 return false;
667 }
668 */
669
670 ConstantDataArray *cstr_array =
671 dyn_cast<ConstantDataArray>(cstr_global->getInitializer());
672
673 if (cstr_array)
674 LLDB_LOG(log, "Found NSString constant {0}, which contains \"{1}\"",
675 value_name, cstr_array->getAsString());
676 else
677 LLDB_LOG(log, "Found NSString constant {0}, which contains \"\"",
678 value_name);
679
680 if (!cstr_array)
681 cstr_global = nullptr;
682
683 if (!RewriteObjCConstString(nsstring_global, cstr_global)) {
684 LLDB_LOG(log, "Error rewriting the constant string");
685
686 // We don't print an error message here because RewriteObjCConstString
687 // has done so for us.
688
689 return false;
690 }
691 }
692 }
693
694 for (StringMapEntry<llvm::Value *> &value_symbol : value_symbol_table) {
695 llvm::StringRef value_name = value_symbol.first();
696
697 if (value_name == "__CFConstantStringClassReference") {
698 GlobalVariable *gv = dyn_cast<GlobalVariable>(value_symbol.second);
699
700 if (!gv) {
701 LLDB_LOG(log,
702 "__CFConstantStringClassReference is not a global variable");
703
704 m_error_stream.Printf("Internal error [IRForTarget]: Found a "
705 "CFConstantStringClassReference, but it is not a "
706 "global object\n");
707
708 return false;
709 }
710
711 gv->eraseFromParent();
712
713 break;
714 }
715 }
716
717 return true;
718}
719
720static bool IsObjCSelectorRef(Value *value) {
721 GlobalVariable *global_variable = dyn_cast<GlobalVariable>(value);
722
723 return !(!global_variable || !global_variable->hasName() ||
724 !global_variable->getName().startswith("OBJC_SELECTOR_REFERENCES_"));
725}
726
727// This function does not report errors; its callers are responsible.
728bool IRForTarget::RewriteObjCSelector(Instruction *selector_load) {
729 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
730
731 LoadInst *load = dyn_cast<LoadInst>(selector_load);
732
733 if (!load)
734 return false;
735
736 // Unpack the message name from the selector. In LLVM IR, an objc_msgSend
737 // gets represented as
738 //
739 // %sel = load ptr, ptr @OBJC_SELECTOR_REFERENCES_, align 8
740 // call i8 @objc_msgSend(ptr %obj, ptr %sel, ...)
741 //
742 // where %obj is the object pointer and %sel is the selector.
743 //
744 // @"OBJC_SELECTOR_REFERENCES_" is a pointer to a character array called
745 // @"\01L_OBJC_METH_VAR_NAME_".
746 // @"\01L_OBJC_METH_VAR_NAME_" contains the string.
747
748 // Find the pointer's initializer and get the string from its target.
749
750 GlobalVariable *_objc_selector_references_ =
751 dyn_cast<GlobalVariable>(load->getPointerOperand());
752
753 if (!_objc_selector_references_ ||
754 !_objc_selector_references_->hasInitializer())
755 return false;
756
757 Constant *osr_initializer = _objc_selector_references_->getInitializer();
758 if (!osr_initializer)
759 return false;
760
761 // Find the string's initializer (a ConstantArray) and get the string from it
762
763 GlobalVariable *_objc_meth_var_name_ =
764 dyn_cast<GlobalVariable>(osr_initializer);
765
766 if (!_objc_meth_var_name_ || !_objc_meth_var_name_->hasInitializer())
767 return false;
768
769 Constant *omvn_initializer = _objc_meth_var_name_->getInitializer();
770
771 ConstantDataArray *omvn_initializer_array =
772 dyn_cast<ConstantDataArray>(omvn_initializer);
773
774 if (!omvn_initializer_array->isString())
775 return false;
776
777 std::string omvn_initializer_string =
778 std::string(omvn_initializer_array->getAsString());
779
780 LLDB_LOG(log, "Found Objective-C selector reference \"{0}\"",
781 omvn_initializer_string);
782
783 // Construct a call to sel_registerName
784
785 if (!m_sel_registerName) {
786 lldb::addr_t sel_registerName_addr;
787
788 bool missing_weak = false;
789 static lldb_private::ConstString g_sel_registerName_str("sel_registerName");
790 sel_registerName_addr = m_execution_unit.FindSymbol(g_sel_registerName_str,
791 missing_weak);
792 if (sel_registerName_addr == LLDB_INVALID_ADDRESS || missing_weak)
793 return false;
794
795 LLDB_LOG(log, "Found sel_registerName at {0}", sel_registerName_addr);
796
797 // Build the function type: struct objc_selector
798 // *sel_registerName(uint8_t*)
799
800 // The below code would be "more correct," but in actuality what's required
801 // is uint8_t*
802 // Type *sel_type = StructType::get(m_module->getContext());
803 // Type *sel_ptr_type = PointerType::getUnqual(sel_type);
804 Type *sel_ptr_type = PointerType::getUnqual(m_module->getContext());
805
806 Type *type_array[1];
807
808 type_array[0] = llvm::PointerType::getUnqual(m_module->getContext());
809
810 ArrayRef<Type *> srN_arg_types(type_array, 1);
811
812 llvm::FunctionType *srN_type =
813 FunctionType::get(sel_ptr_type, srN_arg_types, false);
814
815 // Build the constant containing the pointer to the function
816 PointerType *srN_ptr_ty = PointerType::getUnqual(srN_type);
817 Constant *srN_addr_int =
818 ConstantInt::get(m_intptr_ty, sel_registerName_addr, false);
819 m_sel_registerName = {srN_type,
820 ConstantExpr::getIntToPtr(srN_addr_int, srN_ptr_ty)};
821 }
822
823 CallInst *srN_call =
824 CallInst::Create(m_sel_registerName, _objc_meth_var_name_,
825 "sel_registerName", selector_load);
826
827 // Replace the load with the call in all users
828
829 selector_load->replaceAllUsesWith(srN_call);
830
831 selector_load->eraseFromParent();
832
833 return true;
834}
835
836bool IRForTarget::RewriteObjCSelectors(BasicBlock &basic_block) {
837 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
838
839 InstrList selector_loads;
840
841 for (Instruction &inst : basic_block) {
842 if (LoadInst *load = dyn_cast<LoadInst>(&inst))
843 if (IsObjCSelectorRef(load->getPointerOperand()))
844 selector_loads.push_back(&inst);
845 }
846
847 for (Instruction *inst : selector_loads) {
848 if (!RewriteObjCSelector(inst)) {
849 m_error_stream.Printf("Internal error [IRForTarget]: Couldn't change a "
850 "static reference to an Objective-C selector to a "
851 "dynamic reference\n");
852
853 LLDB_LOG(log, "Couldn't rewrite a reference to an Objective-C selector");
854
855 return false;
856 }
857 }
858
859 return true;
860}
861
862// This function does not report errors; its callers are responsible.
863bool IRForTarget::RewritePersistentAlloc(llvm::Instruction *persistent_alloc) {
864 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
865
866 AllocaInst *alloc = dyn_cast<AllocaInst>(persistent_alloc);
867
868 MDNode *alloc_md = alloc->getMetadata("clang.decl.ptr");
869
870 if (!alloc_md || !alloc_md->getNumOperands())
871 return false;
872
873 ConstantInt *constant_int =
874 mdconst::dyn_extract<ConstantInt>(alloc_md->getOperand(0));
875
876 if (!constant_int)
877 return false;
878
879 // We attempt to register this as a new persistent variable with the DeclMap.
880
881 uintptr_t ptr = constant_int->getZExtValue();
882
883 clang::VarDecl *decl = reinterpret_cast<clang::VarDecl *>(ptr);
884
885 lldb_private::TypeFromParser result_decl_type(
886 m_decl_map->GetTypeSystem()->GetType(decl->getType()));
887
888 StringRef decl_name(decl->getName());
889 lldb_private::ConstString persistent_variable_name(decl_name.data(),
890 decl_name.size());
891 if (!m_decl_map->AddPersistentVariable(decl, persistent_variable_name,
892 result_decl_type, false, false))
893 return false;
894
895 GlobalVariable *persistent_global = new GlobalVariable(
896 (*m_module), alloc->getType(), false, /* not constant */
897 GlobalValue::ExternalLinkage, nullptr, /* no initializer */
898 alloc->getName().str());
899
900 // What we're going to do here is make believe this was a regular old
901 // external variable. That means we need to make the metadata valid.
902
903 NamedMDNode *named_metadata =
904 m_module->getOrInsertNamedMetadata("clang.global.decl.ptrs");
905
906 llvm::Metadata *values[2];
907 values[0] = ConstantAsMetadata::get(persistent_global);
908 values[1] = ConstantAsMetadata::get(constant_int);
909
910 ArrayRef<llvm::Metadata *> value_ref(values, 2);
911
912 MDNode *persistent_global_md = MDNode::get(m_module->getContext(), value_ref);
913 named_metadata->addOperand(persistent_global_md);
914
915 // Now, since the variable is a pointer variable, we will drop in a load of
916 // that pointer variable.
917
918 LoadInst *persistent_load = new LoadInst(persistent_global->getValueType(),
919 persistent_global, "", alloc);
920
921 LLDB_LOG(log, "Replacing \"{0}\" with \"{1}\"", PrintValue(alloc),
922 PrintValue(persistent_load));
923
924 alloc->replaceAllUsesWith(persistent_load);
925 alloc->eraseFromParent();
926
927 return true;
928}
929
930bool IRForTarget::RewritePersistentAllocs(llvm::BasicBlock &basic_block) {
931 if (!m_resolve_vars)
932 return true;
933
934 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
935
936 InstrList pvar_allocs;
937
938 for (Instruction &inst : basic_block) {
939
940 if (AllocaInst *alloc = dyn_cast<AllocaInst>(&inst)) {
941 llvm::StringRef alloc_name = alloc->getName();
942
943 if (alloc_name.startswith("$") && !alloc_name.startswith("$__lldb")) {
944 if (alloc_name.find_first_of("0123456789") == 1) {
945 LLDB_LOG(log, "Rejecting a numeric persistent variable.");
946
947 m_error_stream.Printf("Error [IRForTarget]: Names starting with $0, "
948 "$1, ... are reserved for use as result "
949 "names\n");
950
951 return false;
952 }
953
954 pvar_allocs.push_back(alloc);
955 }
956 }
957 }
958
959 for (Instruction *inst : pvar_allocs) {
960 if (!RewritePersistentAlloc(inst)) {
961 m_error_stream.Printf("Internal error [IRForTarget]: Couldn't rewrite "
962 "the creation of a persistent variable\n");
963
964 LLDB_LOG(log, "Couldn't rewrite the creation of a persistent variable");
965
966 return false;
967 }
968 }
969
970 return true;
971}
972
973// This function does not report errors; its callers are responsible.
974bool IRForTarget::MaybeHandleVariable(Value *llvm_value_ptr) {
975 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
976
977 LLDB_LOG(log, "MaybeHandleVariable ({0})", PrintValue(llvm_value_ptr));
978
979 if (ConstantExpr *constant_expr = dyn_cast<ConstantExpr>(llvm_value_ptr)) {
980 switch (constant_expr->getOpcode()) {
981 default:
982 break;
983 case Instruction::GetElementPtr:
984 case Instruction::BitCast:
985 Value *s = constant_expr->getOperand(0);
986 if (!MaybeHandleVariable(s))
987 return false;
988 }
989 } else if (GlobalVariable *global_variable =
990 dyn_cast<GlobalVariable>(llvm_value_ptr)) {
991 if (!GlobalValue::isExternalLinkage(global_variable->getLinkage()))
992 return true;
993
994 clang::NamedDecl *named_decl = DeclForGlobal(global_variable);
995
996 if (!named_decl) {
997 if (IsObjCSelectorRef(llvm_value_ptr))
998 return true;
999
1000 if (!global_variable->hasExternalLinkage())
1001 return true;
1002
1003 LLDB_LOG(log, "Found global variable \"{0}\" without metadata",
1004 global_variable->getName());
1005
1006 return false;
1007 }
1008
1009 llvm::StringRef name(named_decl->getName());
1010
1011 clang::ValueDecl *value_decl = dyn_cast<clang::ValueDecl>(named_decl);
1012 if (value_decl == nullptr)
1013 return false;
1014
1015 lldb_private::CompilerType compiler_type =
1016 m_decl_map->GetTypeSystem()->GetType(value_decl->getType());
1017
1018 const Type *value_type = nullptr;
1019
1020 if (name.startswith("$")) {
1021 // The $__lldb_expr_result name indicates the return value has allocated
1022 // as a static variable. Per the comment at
1023 // ASTResultSynthesizer::SynthesizeBodyResult, accesses to this static
1024 // variable need to be redirected to the result of dereferencing a
1025 // pointer that is passed in as one of the arguments.
1026 //
1027 // Consequently, when reporting the size of the type, we report a pointer
1028 // type pointing to the type of $__lldb_expr_result, not the type itself.
1029 //
1030 // We also do this for any user-declared persistent variables.
1031 compiler_type = compiler_type.GetPointerType();
1032 value_type = PointerType::get(global_variable->getType(), 0);
1033 } else {
1034 value_type = global_variable->getType();
1035 }
1036
1037 auto *target = m_execution_unit.GetTarget().get();
1038 std::optional<uint64_t> value_size = compiler_type.GetByteSize(target);
1039 if (!value_size)
1040 return false;
1041 std::optional<size_t> opt_alignment = compiler_type.GetTypeBitAlign(target);
1042 if (!opt_alignment)
1043 return false;
1044 lldb::offset_t value_alignment = (*opt_alignment + 7ull) / 8ull;
1045
1046 LLDB_LOG(log,
1047 "Type of \"{0}\" is [clang \"{1}\", llvm \"{2}\"] [size {3}, "
1048 "align {4}]",
1049 name,
1050 lldb_private::ClangUtil::GetQualType(compiler_type).getAsString(),
1051 PrintType(value_type), *value_size, value_alignment);
1052
1053 if (named_decl)
1055 llvm_value_ptr, *value_size,
1056 value_alignment);
1057 } else if (isa<llvm::Function>(llvm_value_ptr)) {
1058 LLDB_LOG(log, "Function pointers aren't handled right now");
1059
1060 return false;
1061 }
1062
1063 return true;
1064}
1065
1066// This function does not report errors; its callers are responsible.
1067bool IRForTarget::HandleSymbol(Value *symbol) {
1068 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
1069
1070 lldb_private::ConstString name(symbol->getName().str().c_str());
1071
1072 lldb::addr_t symbol_addr =
1074
1075 if (symbol_addr == LLDB_INVALID_ADDRESS) {
1076 LLDB_LOG(log, "Symbol \"{0}\" had no address", name);
1077
1078 return false;
1079 }
1080
1081 LLDB_LOG(log, "Found \"{0}\" at {1}", name, symbol_addr);
1082
1083 Type *symbol_type = symbol->getType();
1084
1085 Constant *symbol_addr_int = ConstantInt::get(m_intptr_ty, symbol_addr, false);
1086
1087 Value *symbol_addr_ptr =
1088 ConstantExpr::getIntToPtr(symbol_addr_int, symbol_type);
1089
1090 LLDB_LOG(log, "Replacing {0} with {1}", PrintValue(symbol),
1091 PrintValue(symbol_addr_ptr));
1092
1093 symbol->replaceAllUsesWith(symbol_addr_ptr);
1094
1095 return true;
1096}
1097
1099 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
1100
1101 LLDB_LOG(log, "MaybeHandleCallArguments({0})", PrintValue(Old));
1102
1103 for (unsigned op_index = 0, num_ops = Old->arg_size();
1104 op_index < num_ops; ++op_index)
1105 // conservatively believe that this is a store
1106 if (!MaybeHandleVariable(Old->getArgOperand(op_index))) {
1107 m_error_stream.Printf("Internal error [IRForTarget]: Couldn't rewrite "
1108 "one of the arguments of a function call.\n");
1109
1110 return false;
1111 }
1112
1113 return true;
1114}
1115
1116bool IRForTarget::HandleObjCClass(Value *classlist_reference) {
1117 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
1118
1119 GlobalVariable *global_variable =
1120 dyn_cast<GlobalVariable>(classlist_reference);
1121
1122 if (!global_variable)
1123 return false;
1124
1125 Constant *initializer = global_variable->getInitializer();
1126
1127 if (!initializer)
1128 return false;
1129
1130 if (!initializer->hasName())
1131 return false;
1132
1133 StringRef name(initializer->getName());
1134 lldb_private::ConstString name_cstr(name.str().c_str());
1135 lldb::addr_t class_ptr =
1137
1138 LLDB_LOG(log, "Found reference to Objective-C class {0} ({1})", name,
1139 (unsigned long long)class_ptr);
1140
1141 if (class_ptr == LLDB_INVALID_ADDRESS)
1142 return false;
1143
1144 if (global_variable->use_empty())
1145 return false;
1146
1147 SmallVector<LoadInst *, 2> load_instructions;
1148
1149 for (llvm::User *u : global_variable->users()) {
1150 if (LoadInst *load_instruction = dyn_cast<LoadInst>(u))
1151 load_instructions.push_back(load_instruction);
1152 }
1153
1154 if (load_instructions.empty())
1155 return false;
1156
1157 Constant *class_addr = ConstantInt::get(m_intptr_ty, (uint64_t)class_ptr);
1158
1159 for (LoadInst *load_instruction : load_instructions) {
1160 Constant *class_bitcast =
1161 ConstantExpr::getIntToPtr(class_addr, load_instruction->getType());
1162
1163 load_instruction->replaceAllUsesWith(class_bitcast);
1164
1165 load_instruction->eraseFromParent();
1166 }
1167
1168 return true;
1169}
1170
1171bool IRForTarget::RemoveCXAAtExit(BasicBlock &basic_block) {
1172 std::vector<CallInst *> calls_to_remove;
1173
1174 for (Instruction &inst : basic_block) {
1175 CallInst *call = dyn_cast<CallInst>(&inst);
1176
1177 // MaybeHandleCallArguments handles error reporting; we are silent here
1178 if (!call)
1179 continue;
1180
1181 bool remove = false;
1182
1183 llvm::Function *func = call->getCalledFunction();
1184
1185 if (func && func->getName() == "__cxa_atexit")
1186 remove = true;
1187
1188 llvm::Value *val = call->getCalledOperand();
1189
1190 if (val && val->getName() == "__cxa_atexit")
1191 remove = true;
1192
1193 if (remove)
1194 calls_to_remove.push_back(call);
1195 }
1196
1197 for (CallInst *ci : calls_to_remove)
1198 ci->eraseFromParent();
1199
1200 return true;
1201}
1202
1203bool IRForTarget::ResolveCalls(BasicBlock &basic_block) {
1204 // Prepare the current basic block for execution in the remote process
1205
1206 for (Instruction &inst : basic_block) {
1207 CallInst *call = dyn_cast<CallInst>(&inst);
1208
1209 // MaybeHandleCallArguments handles error reporting; we are silent here
1210 if (call && !MaybeHandleCallArguments(call))
1211 return false;
1212 }
1213
1214 return true;
1215}
1216
1217bool IRForTarget::ResolveExternals(Function &llvm_function) {
1218 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
1219
1220 for (GlobalVariable &global_var : m_module->globals()) {
1221 llvm::StringRef global_name = global_var.getName();
1222
1223 LLDB_LOG(log, "Examining {0}, DeclForGlobalValue returns {1}", global_name,
1224 static_cast<void *>(DeclForGlobal(&global_var)));
1225
1226 if (global_name.startswith("OBJC_IVAR")) {
1227 if (!HandleSymbol(&global_var)) {
1228 m_error_stream.Format("Error [IRForTarget]: Couldn't find Objective-C "
1229 "indirect ivar symbol {0}\n",
1230 global_name);
1231
1232 return false;
1233 }
1234 } else if (global_name.contains("OBJC_CLASSLIST_REFERENCES_$")) {
1235 if (!HandleObjCClass(&global_var)) {
1236 m_error_stream.Printf("Error [IRForTarget]: Couldn't resolve the class "
1237 "for an Objective-C static method call\n");
1238
1239 return false;
1240 }
1241 } else if (global_name.contains("OBJC_CLASSLIST_SUP_REFS_$")) {
1242 if (!HandleObjCClass(&global_var)) {
1243 m_error_stream.Printf("Error [IRForTarget]: Couldn't resolve the class "
1244 "for an Objective-C static method call\n");
1245
1246 return false;
1247 }
1248 } else if (DeclForGlobal(&global_var)) {
1249 if (!MaybeHandleVariable(&global_var)) {
1250 m_error_stream.Format("Internal error [IRForTarget]: Couldn't rewrite "
1251 "external variable {0}\n",
1252 global_name);
1253
1254 return false;
1255 }
1256 }
1257 }
1258
1259 return true;
1260}
1261
1262static bool isGuardVariableRef(Value *V) {
1263 GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
1264
1265 if (!GV || !GV->hasName() || !isGuardVariableSymbol(GV->getName()))
1266 return false;
1267
1268 return true;
1269}
1270
1271void IRForTarget::TurnGuardLoadIntoZero(llvm::Instruction *guard_load) {
1272 Constant *zero(Constant::getNullValue(guard_load->getType()));
1273 guard_load->replaceAllUsesWith(zero);
1274 guard_load->eraseFromParent();
1275}
1276
1277static void ExciseGuardStore(Instruction *guard_store) {
1278 guard_store->eraseFromParent();
1279}
1280
1281bool IRForTarget::RemoveGuards(BasicBlock &basic_block) {
1282 // Eliminate any reference to guard variables found.
1283
1284 InstrList guard_loads;
1285 InstrList guard_stores;
1286
1287 for (Instruction &inst : basic_block) {
1288
1289 if (LoadInst *load = dyn_cast<LoadInst>(&inst))
1290 if (isGuardVariableRef(load->getPointerOperand()))
1291 guard_loads.push_back(&inst);
1292
1293 if (StoreInst *store = dyn_cast<StoreInst>(&inst))
1294 if (isGuardVariableRef(store->getPointerOperand()))
1295 guard_stores.push_back(&inst);
1296 }
1297
1298 for (Instruction *inst : guard_loads)
1300
1301 for (Instruction *inst : guard_stores)
1302 ExciseGuardStore(inst);
1303
1304 return true;
1305}
1306
1307// This function does not report errors; its callers are responsible.
1308bool IRForTarget::UnfoldConstant(Constant *old_constant,
1309 llvm::Function *llvm_function,
1310 FunctionValueCache &value_maker,
1311 FunctionValueCache &entry_instruction_finder,
1312 lldb_private::Stream &error_stream) {
1313 SmallVector<User *, 16> users;
1314
1315 // We do this because the use list might change, invalidating our iterator.
1316 // Much better to keep a work list ourselves.
1317 for (llvm::User *u : old_constant->users())
1318 users.push_back(u);
1319
1320 for (size_t i = 0; i < users.size(); ++i) {
1321 User *user = users[i];
1322
1323 if (Constant *constant = dyn_cast<Constant>(user)) {
1324 // synthesize a new non-constant equivalent of the constant
1325
1326 if (ConstantExpr *constant_expr = dyn_cast<ConstantExpr>(constant)) {
1327 switch (constant_expr->getOpcode()) {
1328 default:
1329 error_stream.Printf("error [IRForTarget internal]: Unhandled "
1330 "constant expression type: \"%s\"",
1331 PrintValue(constant_expr).c_str());
1332 return false;
1333 case Instruction::BitCast: {
1334 FunctionValueCache bit_cast_maker(
1335 [&value_maker, &entry_instruction_finder, old_constant,
1336 constant_expr](llvm::Function *function) -> llvm::Value * {
1337 // UnaryExpr
1338 // OperandList[0] is value
1339
1340 if (constant_expr->getOperand(0) != old_constant)
1341 return constant_expr;
1342
1343 return new BitCastInst(
1344 value_maker.GetValue(function), constant_expr->getType(),
1345 "", llvm::cast<Instruction>(
1346 entry_instruction_finder.GetValue(function)));
1347 });
1348
1349 if (!UnfoldConstant(constant_expr, llvm_function, bit_cast_maker,
1350 entry_instruction_finder, error_stream))
1351 return false;
1352 } break;
1353 case Instruction::GetElementPtr: {
1354 // GetElementPtrConstantExpr
1355 // OperandList[0] is base
1356 // OperandList[1]... are indices
1357
1358 FunctionValueCache get_element_pointer_maker(
1359 [&value_maker, &entry_instruction_finder, old_constant,
1360 constant_expr](llvm::Function *function) -> llvm::Value * {
1361 auto *gep = cast<llvm::GEPOperator>(constant_expr);
1362 Value *ptr = gep->getPointerOperand();
1363
1364 if (ptr == old_constant)
1365 ptr = value_maker.GetValue(function);
1366
1367 std::vector<Value *> index_vector;
1368 for (Value *operand : gep->indices()) {
1369 if (operand == old_constant)
1370 operand = value_maker.GetValue(function);
1371
1372 index_vector.push_back(operand);
1373 }
1374
1375 ArrayRef<Value *> indices(index_vector);
1376
1377 return GetElementPtrInst::Create(
1378 gep->getSourceElementType(), ptr, indices, "",
1379 llvm::cast<Instruction>(
1380 entry_instruction_finder.GetValue(function)));
1381 });
1382
1383 if (!UnfoldConstant(constant_expr, llvm_function,
1384 get_element_pointer_maker,
1385 entry_instruction_finder, error_stream))
1386 return false;
1387 } break;
1388 }
1389 } else {
1390 error_stream.Printf(
1391 "error [IRForTarget internal]: Unhandled constant type: \"%s\"",
1392 PrintValue(constant).c_str());
1393 return false;
1394 }
1395 } else {
1396 if (Instruction *inst = llvm::dyn_cast<Instruction>(user)) {
1397 if (llvm_function && inst->getParent()->getParent() != llvm_function) {
1398 error_stream.PutCString("error: Capturing non-local variables in "
1399 "expressions is unsupported.\n");
1400 return false;
1401 }
1402 inst->replaceUsesOfWith(
1403 old_constant, value_maker.GetValue(inst->getParent()->getParent()));
1404 } else {
1405 error_stream.Printf(
1406 "error [IRForTarget internal]: Unhandled non-constant type: \"%s\"",
1407 PrintValue(user).c_str());
1408 return false;
1409 }
1410 }
1411 }
1412
1413 if (!isa<GlobalValue>(old_constant)) {
1414 old_constant->destroyConstant();
1415 }
1416
1417 return true;
1418}
1419
1420bool IRForTarget::ReplaceVariables(Function &llvm_function) {
1421 if (!m_resolve_vars)
1422 return true;
1423
1424 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
1425
1427
1428 LLDB_LOG(log, "Element arrangement:");
1429
1430 uint32_t num_elements;
1431 uint32_t element_index;
1432
1433 size_t size;
1434 lldb::offset_t alignment;
1435
1436 if (!m_decl_map->GetStructInfo(num_elements, size, alignment))
1437 return false;
1438
1439 Function::arg_iterator iter(llvm_function.arg_begin());
1440
1441 if (iter == llvm_function.arg_end()) {
1442 m_error_stream.Printf("Internal error [IRForTarget]: Wrapper takes no "
1443 "arguments (should take at least a struct pointer)");
1444
1445 return false;
1446 }
1447
1448 Argument *argument = &*iter;
1449
1450 if (argument->getName().equals("this")) {
1451 ++iter;
1452
1453 if (iter == llvm_function.arg_end()) {
1454 m_error_stream.Printf("Internal error [IRForTarget]: Wrapper takes only "
1455 "'this' argument (should take a struct pointer "
1456 "too)");
1457
1458 return false;
1459 }
1460
1461 argument = &*iter;
1462 } else if (argument->getName().equals("self")) {
1463 ++iter;
1464
1465 if (iter == llvm_function.arg_end()) {
1466 m_error_stream.Printf("Internal error [IRForTarget]: Wrapper takes only "
1467 "'self' argument (should take '_cmd' and a struct "
1468 "pointer too)");
1469
1470 return false;
1471 }
1472
1473 if (!iter->getName().equals("_cmd")) {
1474 m_error_stream.Format("Internal error [IRForTarget]: Wrapper takes '{0}' "
1475 "after 'self' argument (should take '_cmd')",
1476 iter->getName());
1477
1478 return false;
1479 }
1480
1481 ++iter;
1482
1483 if (iter == llvm_function.arg_end()) {
1484 m_error_stream.Printf("Internal error [IRForTarget]: Wrapper takes only "
1485 "'self' and '_cmd' arguments (should take a struct "
1486 "pointer too)");
1487
1488 return false;
1489 }
1490
1491 argument = &*iter;
1492 }
1493
1494 if (!argument->getName().equals("$__lldb_arg")) {
1495 m_error_stream.Format("Internal error [IRForTarget]: Wrapper takes an "
1496 "argument named '{0}' instead of the struct pointer",
1497 argument->getName());
1498
1499 return false;
1500 }
1501
1502 LLDB_LOG(log, "Arg: \"{0}\"", PrintValue(argument));
1503
1504 BasicBlock &entry_block(llvm_function.getEntryBlock());
1505 Instruction *FirstEntryInstruction(entry_block.getFirstNonPHIOrDbg());
1506
1507 if (!FirstEntryInstruction) {
1508 m_error_stream.Printf("Internal error [IRForTarget]: Couldn't find the "
1509 "first instruction in the wrapper for use in "
1510 "rewriting");
1511
1512 return false;
1513 }
1514
1515 LLVMContext &context(m_module->getContext());
1516 IntegerType *offset_type(Type::getInt32Ty(context));
1517
1518 if (!offset_type) {
1520 "Internal error [IRForTarget]: Couldn't produce an offset type");
1521
1522 return false;
1523 }
1524
1525 for (element_index = 0; element_index < num_elements; ++element_index) {
1526 const clang::NamedDecl *decl = nullptr;
1527 Value *value = nullptr;
1528 lldb::offset_t offset;
1530
1531 if (!m_decl_map->GetStructElement(decl, value, offset, name,
1532 element_index)) {
1534 "Internal error [IRForTarget]: Structure information is incomplete");
1535
1536 return false;
1537 }
1538
1539 LLDB_LOG(log, " \"{0}\" (\"{1}\") placed at {2}", name,
1540 decl->getNameAsString(), offset);
1541
1542 if (value) {
1543 LLDB_LOG(log, " Replacing [{0}]", PrintValue(value));
1544
1545 FunctionValueCache body_result_maker(
1546 [this, name, offset_type, offset, argument,
1547 value](llvm::Function *function) -> llvm::Value * {
1548 // Per the comment at ASTResultSynthesizer::SynthesizeBodyResult,
1549 // in cases where the result variable is an rvalue, we have to
1550 // synthesize a dereference of the appropriate structure entry in
1551 // order to produce the static variable that the AST thinks it is
1552 // accessing.
1553
1554 llvm::Instruction *entry_instruction = llvm::cast<Instruction>(
1556
1557 Type *int8Ty = Type::getInt8Ty(function->getContext());
1558 ConstantInt *offset_int(
1559 ConstantInt::get(offset_type, offset, true));
1560 GetElementPtrInst *get_element_ptr = GetElementPtrInst::Create(
1561 int8Ty, argument, offset_int, "", entry_instruction);
1562
1563 if (name == m_result_name && !m_result_is_pointer) {
1564 LoadInst *load = new LoadInst(value->getType(), get_element_ptr,
1565 "", entry_instruction);
1566
1567 return load;
1568 } else {
1569 return get_element_ptr;
1570 }
1571 });
1572
1573 if (Constant *constant = dyn_cast<Constant>(value)) {
1574 if (!UnfoldConstant(constant, &llvm_function, body_result_maker,
1576 return false;
1577 }
1578 } else if (Instruction *instruction = dyn_cast<Instruction>(value)) {
1579 if (instruction->getParent()->getParent() != &llvm_function) {
1580 m_error_stream.PutCString("error: Capturing non-local variables in "
1581 "expressions is unsupported.\n");
1582 return false;
1583 }
1584 value->replaceAllUsesWith(
1585 body_result_maker.GetValue(instruction->getParent()->getParent()));
1586 } else {
1587 LLDB_LOG(log, "Unhandled non-constant type: \"{0}\"",
1588 PrintValue(value));
1589 return false;
1590 }
1591
1592 if (GlobalVariable *var = dyn_cast<GlobalVariable>(value))
1593 var->eraseFromParent();
1594 }
1595 }
1596
1597 LLDB_LOG(log, "Total structure [align {0}, size {1}]", (int64_t)alignment,
1598 (uint64_t)size);
1599
1600 return true;
1601}
1602
1603bool IRForTarget::runOnModule(Module &llvm_module) {
1604 lldb_private::Log *log(GetLog(LLDBLog::Expressions));
1605
1606 m_module = &llvm_module;
1607 m_target_data = std::make_unique<DataLayout>(m_module);
1608 m_intptr_ty = llvm::Type::getIntNTy(m_module->getContext(),
1609 m_target_data->getPointerSizeInBits());
1610
1611 if (log) {
1612 std::string s;
1613 raw_string_ostream oss(s);
1614
1615 m_module->print(oss, nullptr);
1616
1617 oss.flush();
1618
1619 LLDB_LOG(log, "Module as passed in to IRForTarget: \n\"{0}\"", s);
1620 }
1621
1622 Function *const main_function =
1623 m_func_name.IsEmpty() ? nullptr
1624 : m_module->getFunction(m_func_name.GetStringRef());
1625
1626 if (!m_func_name.IsEmpty() && !main_function) {
1627 LLDB_LOG(log, "Couldn't find \"{0}()\" in the module", m_func_name);
1628
1629 m_error_stream.Format("Internal error [IRForTarget]: Couldn't find wrapper "
1630 "'{0}' in the module",
1631 m_func_name);
1632
1633 return false;
1634 }
1635
1636 if (main_function) {
1637 if (!FixFunctionLinkage(*main_function)) {
1638 LLDB_LOG(log, "Couldn't fix the linkage for the function");
1639
1640 return false;
1641 }
1642 }
1643
1644 ////////////////////////////////////////////////////////////
1645 // Replace $__lldb_expr_result with a persistent variable
1646 //
1647
1648 if (main_function) {
1649 if (!CreateResultVariable(*main_function)) {
1650 LLDB_LOG(log, "CreateResultVariable() failed");
1651
1652 // CreateResultVariable() reports its own errors, so we don't do so here
1653
1654 return false;
1655 }
1656 }
1657
1658 if (log && log->GetVerbose()) {
1659 std::string s;
1660 raw_string_ostream oss(s);
1661
1662 m_module->print(oss, nullptr);
1663
1664 oss.flush();
1665
1666 LLDB_LOG(log, "Module after creating the result variable: \n\"{0}\"", s);
1667 }
1668
1669 for (llvm::Function &function : *m_module) {
1670 for (BasicBlock &bb : function) {
1671 if (!RemoveGuards(bb)) {
1672 LLDB_LOG(log, "RemoveGuards() failed");
1673
1674 // RemoveGuards() reports its own errors, so we don't do so here
1675
1676 return false;
1677 }
1678
1679 if (!RewritePersistentAllocs(bb)) {
1680 LLDB_LOG(log, "RewritePersistentAllocs() failed");
1681
1682 // RewritePersistentAllocs() reports its own errors, so we don't do so
1683 // here
1684
1685 return false;
1686 }
1687
1688 if (!RemoveCXAAtExit(bb)) {
1689 LLDB_LOG(log, "RemoveCXAAtExit() failed");
1690
1691 // RemoveCXAAtExit() reports its own errors, so we don't do so here
1692
1693 return false;
1694 }
1695 }
1696 }
1697
1698 ///////////////////////////////////////////////////////////////////////////////
1699 // Fix all Objective-C constant strings to use NSStringWithCString:encoding:
1700 //
1701
1702 if (!RewriteObjCConstStrings()) {
1703 LLDB_LOG(log, "RewriteObjCConstStrings() failed");
1704
1705 // RewriteObjCConstStrings() reports its own errors, so we don't do so here
1706
1707 return false;
1708 }
1709
1710 for (llvm::Function &function : *m_module) {
1711 for (llvm::BasicBlock &bb : function) {
1712 if (!RewriteObjCSelectors(bb)) {
1713 LLDB_LOG(log, "RewriteObjCSelectors() failed");
1714
1715 // RewriteObjCSelectors() reports its own errors, so we don't do so
1716 // here
1717
1718 return false;
1719 }
1720 }
1721 }
1722
1723 for (llvm::Function &function : *m_module) {
1724 for (BasicBlock &bb : function) {
1725 if (!ResolveCalls(bb)) {
1726 LLDB_LOG(log, "ResolveCalls() failed");
1727
1728 // ResolveCalls() reports its own errors, so we don't do so here
1729
1730 return false;
1731 }
1732 }
1733 }
1734
1735 ////////////////////////////////////////////////////////////////////////
1736 // Run function-level passes that only make sense on the main function
1737 //
1738
1739 if (main_function) {
1740 if (!ResolveExternals(*main_function)) {
1741 LLDB_LOG(log, "ResolveExternals() failed");
1742
1743 // ResolveExternals() reports its own errors, so we don't do so here
1744
1745 return false;
1746 }
1747
1748 if (!ReplaceVariables(*main_function)) {
1749 LLDB_LOG(log, "ReplaceVariables() failed");
1750
1751 // ReplaceVariables() reports its own errors, so we don't do so here
1752
1753 return false;
1754 }
1755 }
1756
1757 if (log && log->GetVerbose()) {
1758 std::string s;
1759 raw_string_ostream oss(s);
1760
1761 m_module->print(oss, nullptr);
1762
1763 oss.flush();
1764
1765 LLDB_LOG(log, "Module after preparing for execution: \n\"{0}\"", s);
1766 }
1767
1768 return true;
1769}
static bool isGuardVariableSymbol(llvm::StringRef mangled_symbol, bool check_ms_abi=true)
Returns true iff the mangled symbol is for a static guard variable.
static std::string PrintValue(const Value *value, bool truncate=false)
Definition: IRForTarget.cpp:84
static void ExciseGuardStore(Instruction *guard_store)
static llvm::Value * FindEntryInstruction(llvm::Function *function)
Definition: IRForTarget.cpp:65
static bool IsObjCSelectorRef(Value *value)
SmallVector< Instruction *, 2 > InstrList
Definition: IRForTarget.cpp:48
static bool isGuardVariableRef(Value *V)
static std::string PrintType(const llvm::Type *type, bool truncate=false)
Definition: IRForTarget.cpp:96
static std::string PrintValue(const Value *value, bool truncate=false)
static std::string PrintType(const Type *type, bool truncate=false)
#define LLDB_LOG(log,...)
The LLDB_LOG* macros defined below are the way to emit log messages.
Definition: Log.h:342
FunctionValueCache(Maker const &maker)
Definition: IRForTarget.cpp:50
llvm::Value * GetValue(llvm::Function *function)
Definition: IRForTarget.cpp:56
std::function< llvm::Value *(llvm::Function *)> Maker
Definition: IRForTarget.h:357
std::unique_ptr< llvm::DataLayout > m_target_data
The target data for the module being processed, or NULL if there is no module.
Definition: IRForTarget.h:336
lldb_private::ConstString m_func_name
The name of the function to translate.
Definition: IRForTarget.h:327
bool MaybeHandleVariable(llvm::Value *value)
A function-level pass to find all external variables and functions used in the IR.
bool FixFunctionLinkage(llvm::Function &llvm_function)
Ensures that the current function's linkage is set to external.
lldb_private::IRExecutionUnit & m_execution_unit
The execution unit containing the IR being created.
Definition: IRForTarget.h:350
bool CreateResultVariable(llvm::Function &llvm_function)
The top-level pass implementation.
llvm::Module * m_module
The module being processed, or NULL if that has not been determined yet.
Definition: IRForTarget.h:333
IRForTarget(lldb_private::ClangExpressionDeclMap *decl_map, bool resolve_vars, lldb_private::IRExecutionUnit &execution_unit, lldb_private::Stream &error_stream, const char *func_name="$__lldb_expr")
Constructor.
Definition: IRForTarget.cpp:72
bool HandleSymbol(llvm::Value *symbol)
Handle a single externally-defined symbol.
bool RewriteObjCConstStrings()
The top-level pass implementation.
bool ResolveCalls(llvm::BasicBlock &basic_block)
Resolve variable references in calls to external functions.
bool m_result_is_pointer
True if the function's result in the AST is a pointer (see comments in ASTResultSynthesizer::Synthesi...
Definition: IRForTarget.h:353
bool RewriteObjCConstString(llvm::GlobalVariable *NSStr, llvm::GlobalVariable *CStr)
A module-level pass to find Objective-C constant strings and transform them to calls to CFStringCreat...
bool RemoveGuards(llvm::BasicBlock &basic_block)
The top-level pass implementation.
lldb_private::Stream & m_error_stream
The stream on which errors should be printed.
Definition: IRForTarget.h:348
bool HandleObjCClass(llvm::Value *classlist_reference)
Handle a single externally-defined Objective-C class.
bool m_resolve_vars
True if external variable references and persistent variable references should be resolved.
Definition: IRForTarget.h:325
static clang::NamedDecl * DeclForGlobal(const llvm::GlobalValue *global_val, llvm::Module *module)
A function-level pass to take the generated global value $__lldb_expr_result and make it into a persi...
lldb_private::TypeFromParser m_result_type
The type of the result variable.
Definition: IRForTarget.h:331
llvm::FunctionCallee m_CFStringCreateWithBytes
The address of the function CFStringCreateWithBytes, cast to the appropriate function pointer type.
Definition: IRForTarget.h:341
bool MaybeHandleCallArguments(llvm::CallInst *call_inst)
Handle all the arguments to a function call.
bool runOnModule(llvm::Module &llvm_module)
Run this IR transformer on a single module.
bool RewriteObjCSelectors(llvm::BasicBlock &basic_block)
The top-level pass implementation.
lldb_private::ConstString m_result_name
The name of the result variable ($0, $1, ...)
Definition: IRForTarget.h:329
lldb_private::ClangExpressionDeclMap * m_decl_map
The DeclMap containing the Decls.
Definition: IRForTarget.h:338
bool RemoveCXAAtExit(llvm::BasicBlock &basic_block)
Remove calls to __cxa_atexit, which should never be generated by expressions.
bool RewritePersistentAllocs(llvm::BasicBlock &basic_block)
The top-level pass implementation.
bool RewritePersistentAlloc(llvm::Instruction *persistent_alloc)
A basic block-level pass to find all newly-declared persistent variables and register them with the C...
void TurnGuardLoadIntoZero(llvm::Instruction *guard_load)
A basic block-level pass to excise guard variables from the code.
FunctionValueCache m_entry_instruction_finder
Definition: IRForTarget.h:369
llvm::FunctionCallee m_sel_registerName
The address of the function sel_registerName, cast to the appropriate function pointer type.
Definition: IRForTarget.h:344
llvm::IntegerType * m_intptr_ty
The type of an integer large enough to hold a pointer.
Definition: IRForTarget.h:346
bool RewriteObjCSelector(llvm::Instruction *selector_load)
A basic block-level pass to find all Objective-C method calls and rewrite them to use sel_registerNam...
bool ResolveExternals(llvm::Function &llvm_function)
The top-level pass implementation.
bool ReplaceVariables(llvm::Function &llvm_function)
A function-level pass to make all external variable references point at the correct offsets from the ...
static bool UnfoldConstant(llvm::Constant *old_constant, llvm::Function *llvm_function, FunctionValueCache &value_maker, FunctionValueCache &entry_instruction_finder, lldb_private::Stream &error_stream)
UnfoldConstant operates on a constant [Old] which has just been replaced with a value [New].
TypeSystemClang * GetTypeSystem() const
Returns the TypeSystem that uses this ClangASTSource instance as it's ExternalASTSource.
"lldb/Expression/ClangExpressionDeclMap.h" Manages named entities that are defined in LLDB's debug in...
bool AddPersistentVariable(const clang::NamedDecl *decl, ConstString name, TypeFromParser type, bool is_result, bool is_lvalue)
[Used by IRForTarget] Add a variable to the list of persistent variables for the process.
bool GetStructElement(const clang::NamedDecl *&decl, llvm::Value *&value, lldb::offset_t &offset, ConstString &name, uint32_t index)
[Used by IRForTarget] Get specific information about one field of the laid-out struct after DoStructL...
bool DoStructLayout()
[Used by IRForTarget] Finalize the struct, laying out the position of each object in it.
bool AddValueToStruct(const clang::NamedDecl *decl, ConstString name, llvm::Value *value, size_t size, lldb::offset_t alignment)
[Used by IRForTarget] Add a variable to the struct that needs to be materialized each time the expres...
lldb::addr_t GetSymbolAddress(Target &target, Process *process, ConstString name, lldb::SymbolType symbol_type, Module *module=nullptr)
[Used by IRForTarget] Get the address of a symbol given nothing but its name.
bool GetStructInfo(uint32_t &num_elements, size_t &size, lldb::offset_t &alignment)
[Used by IRForTarget] Get general information about the laid-out struct after DoStructLayout() has be...
Generic representation of a type in a programming language.
Definition: CompilerType.h:36
std::optional< uint64_t > GetByteSize(ExecutionContextScope *exe_scope) const
Return the size of the type in bytes.
CompilerType GetPointerType() const
Return a new CompilerType that is a pointer to this type.
std::optional< size_t > GetTypeBitAlign(ExecutionContextScope *exe_scope) const
A uniqued constant string class.
Definition: ConstString.h:40
bool IsEmpty() const
Test for empty string.
Definition: ConstString.h:293
llvm::StringRef GetStringRef() const
Get the string value as a llvm::StringRef.
Definition: ConstString.h:191
const char * GetCString() const
Get the string value as a C string.
Definition: ConstString.h:205
"lldb/Expression/IRExecutionUnit.h" Contains the IR and, optionally, JIT- compiled code for a module.
lldb::addr_t FindSymbol(ConstString name, bool &missing_weak)
lldb::TargetSP GetTarget()
Definition: IRMemoryMap.h:80
bool GetVerbose() const
Definition: Log.cpp:313
const char * GetData() const
Definition: StreamString.h:43
A stream class that can stream formatted output to a file.
Definition: Stream.h:28
void Format(const char *format, Args &&... args)
Definition: Stream.h:309
size_t Printf(const char *format,...) __attribute__((format(printf
Output printf formatted output to the stream.
Definition: Stream.cpp:107
size_t PutCString(llvm::StringRef cstr)
Output a C string to the stream.
Definition: Stream.cpp:63
CompilerType GetType(clang::QualType qt)
Creates a CompilerType from the given QualType with the current TypeSystemClang instance as the Compi...
#define LLDB_INVALID_ADDRESS
Definition: lldb-defines.h:82
TaggedASTType< 0 > TypeFromParser
Definition: TaggedASTType.h:40
uint64_t offset_t
Definition: lldb-types.h:83
@ eSymbolTypeObjCClass
uint64_t addr_t
Definition: lldb-types.h:79
std::shared_ptr< lldb_private::Target > TargetSP
Definition: lldb-forward.h:432
Definition: Debugger.h:53
static clang::QualType GetQualType(const CompilerType &ct)
Definition: ClangUtil.cpp:36