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* [LLVM-C] Improve Bindings For AliasesRobert Widmann2018-05-201-0/+45
| | | | | | | | | | | | | | Summary: Add wrappers for a module's alias iterators and a getter and setter for the aliasee value. Reviewers: whitequark, deadalnix Reviewed By: whitequark Subscribers: llvm-commits, harlanhaskins Differential Revision: https://reviews.llvm.org/D46808 llvm-svn: 332826
* [LLVM-C] Use Length-Providing Value Name Getters and SettersRobert Widmann2018-05-191-0/+10
| | | | | | | | | | | | | | | | Summary: - Provide LLVMGetValueName2 and LLVMSetValueName2 that return and take the length of the provided C string respectively - Deprecate LLVMGetValueName and LLVMSetValueName Reviewers: whitequark, deadalnix Reviewed By: whitequark Subscribers: llvm-commits, harlanhaskins Differential Revision: https://reviews.llvm.org/D46890 llvm-svn: 332810
* Rename DEBUG macro to LLVM_DEBUG.Nicola Zaghen2018-05-141-8/+11
| | | | | | | | | | | | | | | | The DEBUG() macro is very generic so it might clash with other projects. The renaming was done as follows: - git grep -l 'DEBUG' | xargs sed -i 's/\bDEBUG\s\?(/LLVM_DEBUG(/g' - git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM - Manual change to APInt - Manually chage DOCS as regex doesn't match it. In the transition period the DEBUG() macro is still present and aliased to the LLVM_DEBUG() one. Differential Revision: https://reviews.llvm.org/D43624 llvm-svn: 332240
* Fix "not all control paths return a value" MSVC warning. NFCI.Simon Pilgrim2018-05-141-0/+1
| | | | llvm-svn: 332238
* [LLVM-C] Add Bindings For Module FlagsRobert Widmann2018-05-141-0/+104
| | | | | | | | | | | | | | | | | | | Summary: The first foray into merging debug info into the echo tests. - Add bindings to Module::getModuleFlagsMetadata() in the form of LLVMCopyModuleFlagsMetadata - Add the opaque type LLVMModuleFlagEntry to represent Module::ModuleFlagEntry - Add accessors for LLVMModuleFlagEntry's behavior, key, and metadata node. Reviewers: whitequark, deadalnix Reviewed By: whitequark Subscribers: aprantl, JDevlieghere, llvm-commits, harlanhaskins Differential Revision: https://reviews.llvm.org/D46792 llvm-svn: 332219
* [LLVM-C] [PR34633] Avoid calling ->dump() methods from LLVMDump*.whitequark2018-04-171-5/+3
| | | | | | | | | | LLVMDump* functions are available in Release builds too. Patch by Brenton Bostick. Differential Revision: https://reviews.llvm.org/D44600 llvm-svn: 330189
* [LLVM-C] Add Missing 'break's in InlineAsm bindingsRobert Widmann2018-04-101-0/+2
| | | | | | | | | | | | | | Summary: Noticed by Andrea Di Biagio while reviewing r329369 Reviewers: whitequark, harlanhaskins Reviewed By: harlanhaskins Subscribers: llvm-commits, abergmeier-dsfishlabs Differential Revision: https://reviews.llvm.org/D45496 llvm-svn: 329731
* [LLVM-C] Audit Inline Assembly APIs for ConsistencyRobert Widmann2018-04-061-0/+32
| | | | | | | | | | | | | | | | | | Summary: - Add a missing getter for module-level inline assembly - Add a missing append function for module-level inline assembly - Deprecate LLVMSetModuleInlineAsm and replace it with LLVMSetModuleInlineAsm2 which takes an explicit length parameter - Deprecate LLVMConstInlineAsm and replace it with LLVMGetInlineAsm, a function that allows passing a dialect and is not mis-classified as a constant operation Reviewers: whitequark, deadalnix Reviewed By: whitequark Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D45346 llvm-svn: 329369
* [LLVM-C] Finish exception instruction bindings - Round 2Robert Widmann2018-03-301-2/+92
| | | | | | | | | | | | | | | | | | | Summary: Previous revision caused a leak in the echo test that got caught by the ASAN bots because of missing free of the handlers array and was reverted in r328759. Resubmitting the patch with that correction. Add support for cleanupret, catchret, catchpad, cleanuppad and catchswitch and their associated accessors. Test is modified from SimplifyCFG because it contains many diverse usages of these instructions. Reviewers: whitequark, deadalnix Reviewed By: whitequark Subscribers: llvm-commits, vlad.tsyrklevich Differential Revision: https://reviews.llvm.org/D45100 llvm-svn: 328883
* Revert "[LLVM-C] Finish exception instruction bindings"Vlad Tsyrklevich2018-03-301-92/+2
| | | | | | This reverts commit r328759. It was causing LSan failures on sanitizer-x86_64-linux-bootstrap llvm-svn: 328858
* [LLVM-C] Finish exception instruction bindingsRobert Widmann2018-03-291-2/+92
| | | | | | | | | | | | | | | | | Summary: Add support for cleanupret, catchret, catchpad, cleanuppad and catchswitch and their associated accessors. Test is modified from SimplifyCFG because it contains many diverse usages of these instructions. Reviewers: whitequark, deadalnix, echristo Reviewed By: echristo Subscribers: llvm-commits, harlanhaskins Differential Revision: https://reviews.llvm.org/D44496 llvm-svn: 328759
* Fix 'not all control paths return a value' MSVC warning. NFCI.Simon Pilgrim2018-03-141-0/+1
| | | | llvm-svn: 327502
* [LLVM-C] Redo unnamed_address attribute bindingsRobert Widmann2018-03-141-0/+24
| | | | | | | | | | | | | | | | | | | Summary: The old bindings should have used an enum instead of a boolean. This deprecates LLVMHasUnnamedAddr and LLVMSetUnnamedAddr , replacing them with LLVMGetUnnamedAddress and LLVMSetUnnamedAddress respectively that do. Though it is unlikely LLVM will gain more supported global value linker hints, the new API can scale to accommodate this. Reviewers: deadalnix, whitequark Reviewed By: whitequark Subscribers: llvm-commits, harlanhaskins Differential Revision: https://reviews.llvm.org/D43448 llvm-svn: 327479
* [LLVM-C] Add Accessors For A Module's Source File NameRobert Widmann2018-01-301-0/+9
| | | | | | | | | | | | | | Summary: Also unblocks some cleanup in the echo-test. Reviewers: whitequark, deadalnix Reviewed By: whitequark Subscribers: harlanhaskins, llvm-commits Differential Revision: https://reviews.llvm.org/D42618 llvm-svn: 323819
* [LLVM-C] Publicly expose getters of MetadataType, TokenTypewhitequark2017-10-271-3/+6
| | | | | | | | | | | Patch by Robert Widmann. Expose getters for MetadataType and TokenType publicly in the C API. Discovered a need for these while trying to wrap the intrinsics API. Differential Revision: https://reviews.llvm.org/D38809 llvm-svn: 316762
* [raw_fd_ostream] report actual error in error messagesBob Haarman2017-10-241-1/+2
| | | | | | | | | | | | | | | | | Summary: Previously, we would emit error messages like "IO failure on output stream". This change causes use to include information about what actually went wrong, e.g. "No space left on device". Reviewers: sunfish, rnk Reviewed By: rnk Subscribers: mehdi_amini, llvm-commits, hiraditya Differential Revision: https://reviews.llvm.org/D39203 llvm-svn: 316404
* Reverting r315590; it did not include changes for llvm-tblgen, which is ↵Aaron Ballman2017-10-151-1/+1
| | | | | | | | causing link errors for several people. Error LNK2019 unresolved external symbol "public: void __cdecl `anonymous namespace'::MatchableInfo::dump(void)const " (?dump@MatchableInfo@?A0xf4f1c304@@QEBAXXZ) referenced in function "public: void __cdecl `anonymous namespace'::AsmMatcherEmitter::run(class llvm::raw_ostream &)" (?run@AsmMatcherEmitter@?A0xf4f1c304@@QEAAXAEAVraw_ostream@llvm@@@Z) llvm-tblgen D:\llvm\2017\utils\TableGen\AsmMatcherEmitter.obj 1 llvm-svn: 315854
* [dump] Remove NDEBUG from test to enable dump methods [NFC]Don Hinton2017-10-121-1/+1
| | | | | | | | | | | | | | | Summary: Add LLVM_FORCE_ENABLE_DUMP cmake option, and use it along with LLVM_ENABLE_ASSERTIONS to set LLVM_ENABLE_DUMP. Remove NDEBUG and only use LLVM_ENABLE_DUMP to enable dump methods. Move definition of LLVM_ENABLE_DUMP from config.h to llvm-config.h so it'll be picked up by public headers. Differential Revision: https://reviews.llvm.org/D38406 llvm-svn: 315590
* This patch fixes https://bugs.llvm.org/show_bug.cgi?id=32352 Vivek Pandya2017-09-151-3/+3
| | | | | | | | | | | It enables OptimizationRemarkEmitter::allowExtraAnalysis and MachineOptimizationRemarkEmitter::allowExtraAnalysis to return true not only for -fsave-optimization-record but when specific remarks are requested with command line options. The diagnostic handler used to be callback now this patch adds a class DiagnosticHandler. It has virtual method to provide custom diagnostic handler and methods to control which particular remarks are enabled. However LLVM-C API users can still provide callback function for diagnostic handler. llvm-svn: 313390
* This reverts r313381Vivek Pandya2017-09-151-3/+3
| | | | llvm-svn: 313387
* This patch fixes https://bugs.llvm.org/show_bug.cgi?id=32352 Vivek Pandya2017-09-151-3/+3
| | | | | | | | | | | It enables OptimizationRemarkEmitter::allowExtraAnalysis and MachineOptimizationRemarkEmitter::allowExtraAnalysis to return true not only for -fsave-optimization-record but when specific remarks are requested with command line options. The diagnostic handler used to be callback now this patch adds a class DiagnosticHandler. It has virtual method to provide custom diagnostic handler and methods to control which particular remarks are enabled. However LLVM-C API users can still provide callback function for diagnostic handler. llvm-svn: 313382
* IR/Core.cpp: Prune unused "llvm/Bitcode/BitcodeReader.h".NAKAMURA Takumi2017-07-171-1/+0
| | | | llvm-svn: 308161
* Enhance synchscope representationKonstantin Zhuravlyov2017-07-111-8/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | OpenCL 2.0 introduces the notion of memory scopes in atomic operations to global and local memory. These scopes restrict how synchronization is achieved, which can result in improved performance. This change extends existing notion of synchronization scopes in LLVM to support arbitrary scopes expressed as target-specific strings, in addition to the already defined scopes (single thread, system). The LLVM IR and MIR syntax for expressing synchronization scopes has changed to use *syncscope("<scope>")*, where <scope> can be "singlethread" (this replaces *singlethread* keyword), or a target-specific name. As before, if the scope is not specified, it defaults to CrossThread/System scope. Implementation details: - Mapping from synchronization scope name/string to synchronization scope id is stored in LLVM context; - CrossThread/System and SingleThread scopes are pre-defined to efficiently check for known scopes without comparing strings; - Synchronization scope names are stored in SYNC_SCOPE_NAMES_BLOCK in the bitcode. Differential Revision: https://reviews.llvm.org/D21723 llvm-svn: 307722
* [SafepointIRVerifier] Add verifier pass for finding GC relocation bugsAnna Thomas2017-07-051-0/+1
| | | | | | | | | | | | | | | | | | | | Original Patch and summary by Philip Reames. RewriteStatepointsForGC tries to rewrite a function in a manner where the optimizer can't end up using a pointer value after it might have been relocated by a safepoint. This pass checks the invariant that RSForGC is supposed to establish and that (if we constructed semantics correctly) later passes must preserve. This has been a really useful diagnostic tool when initially developing the rewriting scheme and has found numerous bugs. Differential Revision: https://reviews.llvm.org/D15940 Reviewed by: swaroop.sridhar, mjacob Subscribers: llvm-commits llvm-svn: 307112
* [LLVM-C] [OCaml] Expose Type::subtypes.whitequark2017-06-051-0/+12
| | | | | | | | | | | | | The C functions added are LLVMGetNumContainedTypes and LLVMGetSubtypes. The OCaml function added is Llvm.subtypes. Patch by Ekaterina Vaartis. Differential Revision: https://reviews.llvm.org/D33677 llvm-svn: 304709
* Prefer addAttr(Attribute::AttrKind) over the AttributeList overloadReid Kleckner2017-04-191-15/+5
| | | | | | | | This should simplify the call sites, which typically want to tweak one attribute at a time. It should also avoid creating ephemeral AttributeLists that live forever. llvm-svn: 300718
* Introducing LLVMMetadataRefAmaury Sechet2017-04-171-0/+13
| | | | | | | | | | | | | | | | | | | Summary: This seems like an uncontroversial first step toward providing access to the metadata hierarchy that now exists in LLVM. This should allow for good debug info support from C. Future plans are to deprecate API that take mixed bags of values and metadata (mainly the LLVMMDNode family of functions) and migrate the rest toward the use of LLVMMetadataRef. Once this is in place, mapping of DIBuilder will be able to start. Reviewers: mehdi_amini, echristo, whitequark, jketema, Wallbraker Reviewed By: Wallbraker Subscribers: Eugene.Zelenko, axw, mehdi_amini, llvm-commits Differential Revision: https://reviews.llvm.org/D19448 llvm-svn: 300447
* [IR] Add AttributeSet to hide AttributeSetNode* again, NFCReid Kleckner2017-04-121-17/+8
| | | | | | | | | | | | | | | | | Summary: For now, it just wraps AttributeSetNode*. Eventually, it will hold AvailableAttrs as an inline bitset, and adding and removing enum attributes will be super cheap. This sinks AttributeSetNode back down to lib/IR/AttributeImpl.h. Reviewers: pete, chandlerc Subscribers: llvm-commits, jfb Differential Revision: https://reviews.llvm.org/D31940 llvm-svn: 300014
* Remove AttributeSetNode::get(AttributeList, unsigned) and sink constructorReid Kleckner2017-04-101-4/+4
| | | | | | | | | | | The getter was equivalent to AttributeList::getAttributes(unsigned), which seems like a better way to express getting the AttributeSet for a given index. This static helper was only used in one place anyway. The constructor doesn't benefit from inlining and doesn't need to be in a header. llvm-svn: 299900
* Reland "[IR] Make AttributeSetNode public, avoid temporary AttributeList copies"Reid Kleckner2017-04-101-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | This re-lands r299875. I introduced a bug in Clang code responsible for replacing K&R, no prototype declarations with a real function definition with a prototype. The bug was here: // Collect any return attributes from the call. - if (oldAttrs.hasAttributes(llvm::AttributeList::ReturnIndex)) - newAttrs.push_back(llvm::AttributeList::get(newFn->getContext(), - oldAttrs.getRetAttributes())); + newAttrs.push_back(oldAttrs.getRetAttributes()); Previously getRetAttributes() carried AttributeList::ReturnIndex in its AttributeList. Now that we return the AttributeSetNode* directly, it no longer carries that index, and we call this overload with a single node: AttributeList::get(LLVMContext&, ArrayRef<AttributeSetNode*>) That aborted with an assertion on x86_32 targets. I added an explicit triple to the test and added CHECKs to help find issues like this in the future sooner. llvm-svn: 299899
* Revert "[IR] Make AttributeSetNode public, avoid temporary AttributeList copies"Reid Kleckner2017-04-101-1/+1
| | | | | | | This reverts r299875. A Linux bot came back with a test failure: http://bb.pgr.jp/builders/test-clang-i686-linux-RA/builds/741/steps/test_clang/logs/Clang%20%3A%3A%20CodeGen__2006-05-19-SingleEltReturn.c llvm-svn: 299878
* [IR] Make AttributeSetNode public, avoid temporary AttributeList copiesReid Kleckner2017-04-101-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: AttributeList::get(Fn|Ret|Param)Attributes no longer creates a temporary AttributeList just to hide the AttributeSetNode type. I've also added a factory method to create AttributeLists from a parallel array of AttributeSetNodes. I think this simplifies construction of AttributeLists when rewriting function prototypes. Previously we would test if a particular index had attributes, and conditionally add a temporary attribute list to a vector. Now the attribute set vector is parallel to the argument vector already that these passes already construct. My long term vision is to wrap AttributeSetNode* inside an AttributeSet type that holds the enum attributes, but that will come in a follow up change. I haven't done any performance measurements for this change because profiling hasn't shown that any of the affected code is hot. Reviewers: pete, chandlerc, sanjoy, hfinkel Reviewed By: pete Subscribers: jfb, llvm-commits Differential Revision: https://reviews.llvm.org/D31198 llvm-svn: 299875
* Rename AttributeSet to AttributeListReid Kleckner2017-03-211-8/+7
| | | | | | | | | | | | | | | | | | | | | | | | | Summary: This class is a list of AttributeSetNodes corresponding the function prototype of a call or function declaration. This class used to be called ParamAttrListPtr, then AttrListPtr, then AttributeSet. It is typically accessed by parameter and return value index, so "AttributeList" seems like a more intuitive name. Rename AttributeSetImpl to AttributeListImpl to follow suit. It's useful to rename this class so that we can rename AttributeSetNode to AttributeSet later. AttributeSet is the set of attributes that apply to a single function, argument, or return value. Reviewers: sanjoy, javed.absar, chandlerc, pete Reviewed By: pete Subscribers: pete, jholewinski, arsenm, dschuff, mehdi_amini, jfb, nhaehnle, sbc100, void, llvm-commits Differential Revision: https://reviews.llvm.org/D31102 llvm-svn: 298393
* Store Arguments in a flat array instead of an iplistReid Kleckner2017-03-171-10/+7
| | | | | | | | | | | | | | | | | | | | This saves two pointers from Argument and eliminates some extra allocations. Arguments cannot be inserted or removed from a Function because that would require changing its Type, which LLVM does not allow. Instead, passes that change prototypes, like DeadArgElim, create a new Function and copy over argument names and attributes. The primary benefit of iplist is O(1) random insertion and removal. We just don't need that for arguments, so don't use it. Reviewed By: chandlerc Subscribers: dlj, inglorion, llvm-commits Differential Revision: https://reviews.llvm.org/D31058 llvm-svn: 298105
* Include LLVMDumpValue in release builds.Sam McCall2017-01-301-3/+1
| | | | | | This part of the C API is still used in language bindings. llvm-svn: 293460
* llvm-c: Keep LLVMDumpModule() even in release buildsMatthias Braun2017-01-291-4/+3
| | | | | | | | While this probably should be considered a dump debugger utility, the C API currently has no other ways to print a module to stderr for error reporting purposes, so keep it even in release builds. llvm-svn: 293436
* Cleanup dump() functions.Matthias Braun2017-01-281-3/+9
| | | | | | | | | | | | | | | | | | We had various variants of defining dump() functions in LLVM. Normalize them (this should just consistently implement the things discussed in http://lists.llvm.org/pipermail/cfe-dev/2014-January/034323.html For reference: - Public headers should just declare the dump() method but not use LLVM_DUMP_METHOD or #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) - The definition of a dump method should look like this: #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) LLVM_DUMP_METHOD void MyClass::dump() { // print stuff to dbgs()... } #endif llvm-svn: 293359
* Replace APFloatBase static fltSemantics data members with getter functionsStephan Bergmann2016-12-141-1/+1
| | | | | | | | | | | | | At least the plugin used by the LibreOffice build (<https://wiki.documentfoundation.org/Development/Clang_plugins>) indirectly uses those members (through inline functions in LLVM/Clang include files in turn using them), but they are not exported by utils/extract_symbols.py on Windows, and accessing data across DLL/EXE boundaries on Windows is generally problematic. Differential Revision: https://reviews.llvm.org/D26671 llvm-svn: 289647
* IR: Change PointerType to derive from Type rather than SequentialType.Peter Collingbourne2016-12-021-2/+5
| | | | | | | | | | | | | | | | | | | As proposed on llvm-dev: http://lists.llvm.org/pipermail/llvm-dev/2016-October/106640.html This is for a couple of reasons: - Values of type PointerType are unlike the other SequentialTypes (arrays and vectors) in that they do not hold values of the element type. By moving PointerType we can unify certain aspects of how the other SequentialTypes are handled. - PointerType will have no place in the SequentialType hierarchy once pointee types are removed, so this is a necessary step towards removing pointee types. Differential Revision: https://reviews.llvm.org/D26595 llvm-svn: 288462
* [C API] Fix several null pointer dereferences.whitequark2016-11-121-0/+8
| | | | llvm-svn: 286704
* Split Bitcode/ReaderWriter.h into separate reader and writer headersTeresa Johnson2016-11-111-1/+1
| | | | | | | | | | | | | | | | | | | | | Summary: Split ReaderWriter.h which contains the APIs into both the BitReader and BitWriter libraries into BitcodeReader.h and BitcodeWriter.h. This is to address Chandler's concern about sharing the same API header between multiple libraries (BitReader and BitWriter). That concern is why we create a single bitcode library in our downstream build of clang, which led to r286297 being reverted as it added a dependency that created a cycle only when there is a single bitcode library (not two as in upstream). Reviewers: mehdi_amini Subscribers: dlj, mehdi_amini, llvm-commits Differential Revision: https://reviews.llvm.org/D26502 llvm-svn: 286566
* Kill deprecated attribute APIAmaury Sechet2016-11-061-66/+0
| | | | | | | | | | | | | | | Summary: This kill various depreacated API related to attribute : - The deprecated C API attribute based on LLVMAttribute enum. - The Raw attribute set format (planned to be removed in 4.0). Reviewers: bkramer, echristo, mehdi_amini, void Subscribers: mehdi_amini, llvm-commits Differential Revision: https://reviews.llvm.org/D23039 llvm-svn: 286062
* [C API] Add LLVMConstExactUDiv and LLVMBuildExactUDiv functions.Manuel Jacob2016-10-041-0/+11
| | | | | | | | | | | | | | Summary: These are analog to the existing LLVMConstExactSDiv and LLVMBuildExactSDiv functions. Reviewers: deadalnix, majnemer Subscribers: majnemer, llvm-commits Differential Revision: https://reviews.llvm.org/D25259 llvm-svn: 283269
* IR: Don't cast the end iterator to Instruction*Duncan P. N. Exon Smith2016-08-111-2/+2
| | | | | | | | | | | End iterators are usually sentinels, not actually Instruction* at all. Stop casting to it just to get an iterator back. There is likely no observable functionality change here right now (although this is relying on UB, I doubt it was triggering anything), but I'll be removing the cast soon. llvm-svn: 278346
* Expose AttributeSetNode, use it to provide aggregate getter for attribute in ↵Amaury Sechet2016-07-211-0/+28
| | | | | | | | | | | | | | the C API. Summary: See D19181 for context. Reviewers: whitequark, Wallbraker, jyknight, echristo, bkramer, void Subscribers: mehdi_amini Differential Revision: http://reviews.llvm.org/D21265 llvm-svn: 276236
* Apply clang-tidy's modernize-loop-convert to most of lib/IR.Benjamin Kramer2016-06-261-2/+2
| | | | | | Only minor manual fixes. No functionality change intended. llvm-svn: 273813
* Add support for string attributes in the C API.Amaury Sechet2016-06-151-1/+23
| | | | | | | | | | | | Summary: As per title. This completes the C API Attribute support. Reviewers: Wallbraker, whitequark, echristo, rafael, jyknight Subscribers: mehdi_amini Differential Revision: http://reviews.llvm.org/D21365 llvm-svn: 272811
* Add support for callsite in the new C API for attributesAmaury Sechet2016-06-151-0/+18
| | | | | | | | | | | | Summary: The second consumer of attributes. Reviewers: Wallbraker, whitequark, echristo, rafael, jyknight Subscribers: mehdi_amini Differential Revision: http://reviews.llvm.org/D21266 llvm-svn: 272754
* Remove unused import. NFCAmaury Sechet2016-06-141-1/+0
| | | | llvm-svn: 272731
* IR: Introduce local_unnamed_addr attribute.Peter Collingbourne2016-06-141-2/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If a local_unnamed_addr attribute is attached to a global, the address is known to be insignificant within the module. It is distinct from the existing unnamed_addr attribute in that it only describes a local property of the module rather than a global property of the symbol. This attribute is intended to be used by the code generator and LTO to allow the linker to decide whether the global needs to be in the symbol table. It is possible to exclude a global from the symbol table if three things are true: - This attribute is present on every instance of the global (which means that the normal rule that the global must have a unique address can be broken without being observable by the program by performing comparisons against the global's address) - The global has linkonce_odr linkage (which means that each linkage unit must have its own copy of the global if it requires one, and the copy in each linkage unit must be the same) - It is a constant or a function (which means that the program cannot observe that the unique-address rule has been broken by writing to the global) Although this attribute could in principle be computed from the module contents, LTO clients (i.e. linkers) will normally need to be able to compute this property as part of symbol resolution, and it would be inefficient to materialize every module just to compute it. See: http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160509/356401.html http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160516/356738.html for earlier discussion. Part of the fix for PR27553. Differential Revision: http://reviews.llvm.org/D20348 llvm-svn: 272709
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