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* Limit COFF 'common' emission to <=32 alignment types.Erich Keane2019-01-081-0/+5
| | | | | | | | | | | | | | | | As reported in PR33035, LLVM crashes if given a common object with an alignment of greater than 32 bits. This is because the COFF file format does not support these alignments, so emitting them is broken anyway. This patch changes any global definitions greater than 32 bit alignment to no longer be in 'common'. https://bugs.llvm.org/show_bug.cgi?id=33035 Differential Revision: https://reviews.llvm.org/D56391 Change-Id: I48609289753b7f3b58c5e2bc1712756750fbd45a llvm-svn: 350643
* Don't emit DW_AT_enum_class unless it's actually an 'enum class'.Paul Robinson2019-01-081-1/+1
| | | | | | | | Finishes off the functional part of PR36168. Differential Revision: https://reviews.llvm.org/D56393 llvm-svn: 350636
* [OPENMP]Add call to __kmpc_push_target_tripcount() function.Alexey Bataev2019-01-074-2/+210
| | | | | | | | | | Each we create the target regions with the teams distribute inner region, we can better estimate number of the teams required to execute the target region. Function __kmpc_push_target_tripcount() is used for purpose, which accepts device_id and the number of the iterations, performed by the associated loop. llvm-svn: 350571
* Recommit r350555 "[X86] Use funnel shift intrinsics for the VBMI2 ↵Craig Topper2019-01-071-0/+46
| | | | | | | | vshld/vshrd builtins." The MSVC limit hit in AutoUpgrade.cpp has been worked around for now. llvm-svn: 350568
* Revert r350555 "[X86] Use funnel shift intrinsics for the VBMI2 vshld/vshrd ↵Craig Topper2019-01-071-46/+0
| | | | | | | | builtins." Had to revert the LLVM patch this depends on to fix a MSVC compiler limit in AutoUpgrade.cpp llvm-svn: 350563
* [X86] Use funnel shift intrinsics for the VBMI2 vshld/vshrd builtins.Craig Topper2019-01-071-0/+46
| | | | | | Differential Revision: https://reviews.llvm.org/D56365 llvm-svn: 350555
* [OPENMP][NVPTX]Reduce number of barriers in reductions.Alexey Bataev2019-01-071-7/+0
| | | | | | | After the fix for the syncthreads we don't need to generate extra barriers for the parallel reductions. llvm-svn: 350530
* [AST] Store some data of CXXNewExpr as trailing objectsBruno Ricci2019-01-071-2/+2
| | | | | | | | | | | | | | | | | Store the optional array size expression, optional initialization expression and optional placement new arguments in a trailing array. Additionally store the range for the parenthesized type-id in a trailing object if needed since in the vast majority of cases the type is not parenthesized (not a single new expression in the translation unit of SemaDecl.cpp has a parenthesized type-id). This saves 2 pointers per CXXNewExpr in all cases, and 2 pointers + 8 bytes per CXXNewExpr in the common case where the type is not parenthesized. Differential Revision: https://reviews.llvm.org/D56134 Reviewed By: rjmccall llvm-svn: 350527
* CodeGen: fix autolink emission on ELFSaleem Abdulrasool2019-01-051-5/+15
| | | | | | | | | The autolinking extension for ELF uses a slightly different format for encoding the autolink information compared to COFF and MachO. Account for this in the CGM to ensure that we do not assert when emitting assembly or an object file. llvm-svn: 350476
* CodeGen: switch iteration to range based for loop (NFC)Saleem Abdulrasool2019-01-051-6/+4
| | | | | | | Change a loop to range based instead while working on cleaning up some modules autolinking issues on Linux. NFC. llvm-svn: 350472
* hwasan: Implement lazy thread initialization for the interceptor ABI.Peter Collingbourne2019-01-041-0/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The problem is similar to D55986 but for threads: a process with the interceptor hwasan library loaded might have some threads started by instrumented libraries and some by uninstrumented libraries, and we need to be able to run instrumented code on the latter. The solution is to perform per-thread initialization lazily. If a function needs to access shadow memory or add itself to the per-thread ring buffer its prologue checks to see whether the value in the sanitizer TLS slot is null, and if so it calls __hwasan_thread_enter and reloads from the TLS slot. The runtime does the same thing if it needs to access this data structure. This change means that the code generator needs to know whether we are targeting the interceptor runtime, since we don't want to pay the cost of lazy initialization when targeting a platform with native hwasan support. A flag -fsanitize-hwaddress-abi={interceptor,platform} has been introduced for selecting the runtime ABI to target. The default ABI is set to interceptor since it's assumed that it will be more common that users will be compiling application code than platform code. Because we can no longer assume that the TLS slot is initialized, the pthread_create interceptor is no longer necessary, so it has been removed. Ideally, lazy initialization should only cost one instruction in the hot path, but at present the call may cause us to spill arguments to the stack, which means more instructions in the hot path (or theoretically in the cold path if the spills are moved with shrink wrapping). With an appropriately chosen calling convention for the per-thread initialization function (TODO) the hot path should always need just one instruction and the cold path should need two instructions with no spilling required. Differential Revision: https://reviews.llvm.org/D56038 llvm-svn: 350429
* [ThinLTO] Clang changes to utilize new pass to handle chains of aliasesTeresa Johnson2019-01-041-2/+7
| | | | | | | | | | | | | | | | Summary: As with NameAnonGlobals, invoke the new CanonicalizeAliases via clang when using the new PM. Depends on D54507. Reviewers: pcc, davidxl Subscribers: mehdi_amini, inglorion, steven_wu, dexonsmith, cfe-commits Differential Revision: https://reviews.llvm.org/D55620 llvm-svn: 350424
* [ObjCARC] Add an new attribute, objc_externally_retainedErik Pilkington2019-01-042-15/+21
| | | | | | | | | | | | | | | | | | | | This attribute, called "objc_externally_retained", exposes clang's notion of pseudo-__strong variables in ARC. Pseudo-strong variables "borrow" their initializer, meaning that they don't retain/release it, instead assuming that someone else is keeping their value alive. If a function is annotated with this attribute, implicitly strong parameters of that function aren't implicitly retained/released in the function body, and are implicitly const. This is useful to expose for performance reasons, most functions don't need the extra safety of the retain/release, so programmers can opt out as needed. This attribute can also apply to declarations of local variables, with similar effect. Differential revision: https://reviews.llvm.org/D55865 llvm-svn: 350422
* [OPENMP][NVPTX]Use new functions from the runtime library.Alexey Bataev2019-01-041-30/+43
| | | | | | Updated codegen to use the new functions from the runtime library. llvm-svn: 350415
* Add two new pragmas for controlling software pipelining optimizations.Aaron Ballman2019-01-042-2/+50
| | | | | | | | This patch adds #pragma clang loop pipeline and #pragma clang loop pipeline_initiation_interval for debugging or reducing compile time purposes. It is possible to disable SWP for concrete loops to save compilation time or to find bugs by not doing SWP to certain loops. It is possible to set value of initiation interval to concrete number to save compilation time by not doing extra pipeliner passes or to check created schedule for specific initiation interval. Patch by Alexey Lapshin. llvm-svn: 350414
* Adopt SwiftABIInfo for WebAssembly.Daniel Dunbar2019-01-031-6/+17
| | | | | | | | | | | | | | | | | Summary: - This adopts SwiftABIInfo as the base class for WebAssemblyABIInfo, which is in keeping with what is done for other targets for which Swift is supported. - This is a minimal patch to unblock exploration of WASM support for Swift (https://bugs.swift.org/browse/SR-9307) Reviewers: rjmccall, sunfish Reviewed By: rjmccall Subscribers: ahti, dschuff, sbc100, jgravelle-google, aheejin, cfe-commits Differential Revision: https://reviews.llvm.org/D56188 llvm-svn: 350372
* [OPENMP][NVPTX]Use __kmpc_barrier_simple_spmd(nullptr, 0) instead ofAlexey Bataev2019-01-032-12/+32
| | | | | | | | | | nvvm_barrier0. Use runtime functions instead of the direct call to the nvvm intrinsics. It allows to prevent some dangerous LLVM optimizations, that breaks the code for the NVPTX target. llvm-svn: 350328
* [NewPM] Port MsanPhilip Pfaffe2019-01-031-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | Summary: Keeping msan a function pass requires replacing the module level initialization: That means, don't define a ctor function which calls __msan_init, instead just declare the init function at the first access, and add that to the global ctors list. Changes: - Pull the actual sanitizer and the wrapper pass apart. - Add a newpm msan pass. The function pass inserts calls to runtime library functions, for which it inserts declarations as necessary. - Update tests. Caveats: - There is one test that I dropped, because it specifically tested the definition of the ctor. Reviewers: chandlerc, fedor.sergeev, leonardchan, vitalybuka Subscribers: sdardis, nemanjai, javed.absar, hiraditya, kbarton, bollu, atanasyan, jsji Differential Revision: https://reviews.llvm.org/D55647 llvm-svn: 350305
* [OpenMP] Added support for explicit mapping of classes using 'this' pointer. ↵Patrick Lyster2019-01-021-2/+9
| | | | | | Differential revision: https://reviews.llvm.org/D55982 llvm-svn: 350252
* Only convert objc messages to alloc to objc_alloc if the receiver is a class.Pete Cooper2019-01-021-3/+6
| | | | | | | | | | r348687 converted [Foo alloc] to objc_alloc(Foo). However the objc runtime method only takes a Class, not an arbitrary pointer. This makes sure we are messaging a class before we convert these messages. rdar://problem/46943703 llvm-svn: 350224
* [CodeGen] Replace '@' characters in block descriptors' symbol names withAkira Hatanaka2018-12-291-0/+3
| | | | | | | | | | | | | | '\1'. '@' can't be used in block descriptors' symbol names since it is reserved on ELF platforms as a separator between symbol names and symbol versions. See the discussion here: https://reviews.llvm.org/D50783. Differential Revision: https://reviews.llvm.org/D54539 llvm-svn: 350157
* [objc-gnustep2] Fix a bug in category generation.David Chisnall2018-12-281-6/+20
| | | | | | | | | We were not emitting a protocol definition while generating the category method list. This was fine in most cases, because something else in the library typically referenced any given protocol, but it caused linker failures if the category was the only reference to a given protocol. llvm-svn: 350130
* [objc-gnustep] Fix a copy-and-paste error.David Chisnall2018-12-271-1/+1
| | | | | | | We were emitting the null class symbol in the wrong section, which meant that programs that contained no Objective-C classes would fail to link. llvm-svn: 350092
* [CUDA] Treat extern global variable shadows same as regular extern vars.Artem Belevich2018-12-221-10/+5
| | | | | | | | | | | This fixes compiler crash when we attempted to compile this code: extern __device__ int data; __device__ int data = 1; Differential Revision: https://reviews.llvm.org/D56033 llvm-svn: 349981
* Convert some ObjC retain/release msgSends to runtime calls.Pete Cooper2018-12-213-0/+94
| | | | | | | | | | It is faster to directly call the ObjC runtime for methods such as retain/release instead of sending a message to those functions. Differential Revision: https://reviews.llvm.org/D55869 Reviewed By: rjmccall llvm-svn: 349952
* [AST] Store the callee and argument expressions of CallExpr in a trailing array.Bruno Ricci2018-12-211-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Since CallExpr::setNumArgs has been removed, it is now possible to store the callee expression and the argument expressions of CallExpr in a trailing array. This saves one pointer per CallExpr, CXXOperatorCallExpr, CXXMemberCallExpr, CUDAKernelCallExpr and UserDefinedLiteral. Given that CallExpr is used as a base of the above classes we cannot use llvm::TrailingObjects. Instead we store the offset in bytes from the this pointer to the start of the trailing objects and manually do the casts + arithmetic. Some notes: 1.) I did not try to fit the number of arguments in the bit-fields of Stmt. This leaves some space for future additions and avoid the discussion about whether x bits are sufficient to hold the number of arguments. 2.) It would be perfectly possible to recompute the offset to the trailing objects before accessing the trailing objects. However the trailing objects are frequently accessed and benchmarks show that it is slightly faster to just load the offset from the bit-fields. Additionally, because of 1), we have plenty of space in the bit-fields of Stmt. Differential Revision: https://reviews.llvm.org/D55771 Reviewed By: rjmccall llvm-svn: 349910
* [AST][NFC] Pass the AST context to one of the ctor of DeclRefExpr.Bruno Ricci2018-12-215-43/+46
| | | | | | | | | All of the other constructors already take a reference to the AST context. This avoids calling Decl::getASTContext in most cases. Additionally move the definition of the constructor from Expr.h to Expr.cpp since it is calling DeclRefExpr::computeDependence. NFC. llvm-svn: 349901
* [CodeGen] Fix assertion on emitting cleanup for object with inlined ↵Volodymyr Sapsai2018-12-201-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | inherited constructor and non-trivial destructor. Fixes assertion > Assertion failed: (isa<X>(Val) && "cast<Ty>() argument of incompatible type!"), function cast, file llvm/Support/Casting.h, line 255. It was triggered by trying to cast `FunctionDecl` to `CXXMethodDecl` as `CGF.CurCodeDecl` in `CallBaseDtor::Emit`. It was happening because cleanups were emitted in `ScalarExprEmitter::VisitExprWithCleanups` after destroying `InlinedInheritingConstructorScope`, so `CodeGenFunction.CurCodeDecl` didn't correspond to expected cleanup decl. Fix the assertion by emitting cleanups before leaving `InlinedInheritingConstructorScope` and changing `CurCodeDecl`. Test cases based on a patch by Shoaib Meenai. Fixes PR36748. rdar://problem/45805151 Reviewers: rsmith, rjmccall Reviewed By: rjmccall Subscribers: jkorous, dexonsmith, cfe-commits, smeenai, compnerd Differential Revision: https://reviews.llvm.org/D55543 llvm-svn: 349848
* Declares __cpu_model as dso localHaibo Huang2018-12-201-0/+7
| | | | | | | | __builtin_cpu_supports and __builtin_cpu_is use information in __cpu_model to decide cpu features. Before this change, __cpu_model was not declared as dso local. The generated code looks up the address in GOT when reading __cpu_model. This makes it impossible to use these functions in ifunc, because at that time GOT entries have not been relocated. This change makes it dso local. Differential Revision: https://reviews.llvm.org/D53850 llvm-svn: 349825
* [CodeGen] Generate llvm.loop.parallel_accesses instead of ↵Michael Kruse2018-12-202-16/+29
| | | | | | | | | | | | | | llvm.mem.parallel_loop_access metadata. Instead of generating llvm.mem.parallel_loop_access metadata, generate llvm.access.group on instructions and llvm.loop.parallel_accesses on loops. There is one access group per generated loop. This is clang part of D52116/r349725. Differential Revision: https://reviews.llvm.org/D52117 llvm-svn: 349823
* [X86] Auto upgrade XOP/AVX512 rotation intrinsics to generic funnel shift ↵Simon Pilgrim2018-12-201-1/+53
| | | | | | | | | | | | intrinsics (clang) This emits FSHL/FSHR generic intrinsics for the XOP VPROT and AVX512 VPROL/VPROR rotation intrinsics. LLVM counterpart: https://reviews.llvm.org/D55938 Differential Revision: https://reviews.llvm.org/D55937 llvm-svn: 349796
* Use @llvm.objc.clang.arc.use intrinsic instead of clang.arc.use function.Pete Cooper2018-12-201-5/+2
| | | | | | | | Calls to this function are deleted in the ARC optimizer. However when the ARC optimizer was updated to use intrinsics instead of functions (r349534), the corresponding clang change (r349535) to use intrinsics missed this one so it wasn't being deleted. llvm-svn: 349782
* [X86][SSE] Auto upgrade PADDS/PSUBS intrinsics to SADD_SAT/SSUB_SAT generic ↵Simon Pilgrim2018-12-201-6/+21
| | | | | | | | | | | | intrinsics (clang) This emits SADD_SAT/SSUB_SAT generic intrinsics for the SSE signed saturated math intrinsics. LLVM counterpart: https://reviews.llvm.org/D55894 Differential Revision: https://reviews.llvm.org/D55890 llvm-svn: 349743
* [X86][SSE] Auto upgrade PADDUS/PSUBUS intrinsics to UADD_SAT/USUB_SAT ↵Simon Pilgrim2018-12-191-25/+8
| | | | | | | | | | generic intrinsics (clang) Sibling patch to D55855, this emits UADD_SAT/USUB_SAT generic intrinsics for the SSE saturated math intrinsics instead of expanding to a IR code sequence that could be difficult to reassemble. Differential Revision: https://reviews.llvm.org/D55879 llvm-svn: 349631
* Emit ASM input in a constant contextBill Wendling2018-12-181-2/+5
| | | | | | | | | | | | | | | | | Summary: Some ASM input constraints (e.g., "i" and "n") require immediate values. At O0, very few code transformations are performed. So if we cannot resolve to an immediate when emitting the ASM input we shouldn't delay its processing. Reviewers: rsmith, efriedma Reviewed By: efriedma Subscribers: rehana, efriedma, craig.topper, jyknight, cfe-commits Differential Revision: https://reviews.llvm.org/D55616 llvm-svn: 349561
* [OPENMP] parsing and sema support for 'close' map-type-modifierKelvin Li2018-12-181-32/+33
| | | | | | | | | | | | A map clause with the close map-type-modifier is a hint to prefer that the variables are mapped using a copy into faster memory. Patch by Ahsan Saghir (saghir) Differential Revision: https://reviews.llvm.org/D55719 llvm-svn: 349551
* [CodeGen] Handle mixed-width ops in mixed-sign mul-with-overflow loweringVedant Kumar2018-12-181-5/+14
| | | | | | | | | | | | | | | | | | | | | | The special lowering for __builtin_mul_overflow introduced in r320902 fixed an ICE seen when passing mixed-sign operands to the builtin. This patch extends the special lowering to cover mixed-width, mixed-sign operands. In a few common scenarios, calls to muloti4 will no longer be emitted. This should address the latest comments in PR34920 and work around the link failure seen in: https://bugzilla.redhat.com/show_bug.cgi?id=1657544 Testing: - check-clang - A/B output comparison with: https://gist.github.com/vedantk/3eb9c88f82e5c32f2e590555b4af5081 Differential Revision: https://reviews.llvm.org/D55843 llvm-svn: 349542
* [OPENMP][NVPTX]Emit shared memory buffer for reduction as 128 bytesAlexey Bataev2018-12-181-0/+16
| | | | | | | | | | | buffer. Seems to me, nvlink has a bug with the proper support of the weakly linked symbols. It does not allow to define several shared memory buffer with the different sizes even with the weak linkage. Instead we always use 128 bytes buffer to prevent nvlink from the error message emission. llvm-svn: 349540
* Generate objc intrinsics instead of runtime calls as the ARC optimizer now ↵Pete Cooper2018-12-182-75/+94
| | | | | | | | | works only on intrinsics Differential Revision: https://reviews.llvm.org/D55802 Reviewers: rjmccall llvm-svn: 349535
* [OPENMP][NVPTX]Added extra sync point to the inter-warp copy function.Alexey Bataev2018-12-181-0/+5
| | | | | | | The parallel reduction operation requires an extra synchronization point in the inter-warp copy function to avoid divergence. llvm-svn: 349525
* [NFC] Fix usage of Builder.insert(new Bitcast...)in CodeGenFunctionErich Keane2018-12-181-1/+1
| | | | | | | | | | | | This is exactly a "CreateBitCast", so refactor this to get rid of a 'new'. Note that this slightly changes the test, as the Builder is now seemingly smart enough to fold one of the bitcasts into the annotation call. Change-Id: I1733fb1fdf91f5c9d88651067130b9a4e7b5ab67 llvm-svn: 349506
* Automatic variable initializationJF Bastien2018-12-181-13/+244
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: Add an option to initialize automatic variables with either a pattern or with zeroes. The default is still that automatic variables are uninitialized. Also add attributes to request uninitialized on a per-variable basis, mainly to disable initialization of large stack arrays when deemed too expensive. This isn't meant to change the semantics of C and C++. Rather, it's meant to be a last-resort when programmers inadvertently have some undefined behavior in their code. This patch aims to make undefined behavior hurt less, which security-minded people will be very happy about. Notably, this means that there's no inadvertent information leak when: - The compiler re-uses stack slots, and a value is used uninitialized. - The compiler re-uses a register, and a value is used uninitialized. - Stack structs / arrays / unions with padding are copied. This patch only addresses stack and register information leaks. There's many more infoleaks that we could address, and much more undefined behavior that could be tamed. Let's keep this patch focused, and I'm happy to address related issues elsewhere. To keep the patch simple, only some `undef` is removed for now, see `replaceUndef`. The padding-related infoleaks are therefore not all gone yet. This will be addressed in a follow-up, mainly because addressing padding-related leaks should be a stand-alone option which is implied by variable initialization. There are three options when it comes to automatic variable initialization: 0. Uninitialized This is C and C++'s default. It's not changing. Depending on code generation, a programmer who runs into undefined behavior by using an uninialized automatic variable may observe any previous value (including program secrets), or any value which the compiler saw fit to materialize on the stack or in a register (this could be to synthesize an immediate, to refer to code or data locations, to generate cookies, etc). 1. Pattern initialization This is the recommended initialization approach. Pattern initialization's goal is to initialize automatic variables with values which will likely transform logic bugs into crashes down the line, are easily recognizable in a crash dump, without being values which programmers can rely on for useful program semantics. At the same time, pattern initialization tries to generate code which will optimize well. You'll find the following details in `patternFor`: - Integers are initialized with repeated 0xAA bytes (infinite scream). - Vectors of integers are also initialized with infinite scream. - Pointers are initialized with infinite scream on 64-bit platforms because it's an unmappable pointer value on architectures I'm aware of. Pointers are initialize to 0x000000AA (small scream) on 32-bit platforms because 32-bit platforms don't consistently offer unmappable pages. When they do it's usually the zero page. As people try this out, I expect that we'll want to allow different platforms to customize this, let's do so later. - Vectors of pointers are initialized the same way pointers are. - Floating point values and vectors are initialized with a negative quiet NaN with repeated 0xFF payload (e.g. 0xffffffff and 0xffffffffffffffff). NaNs are nice (here, anways) because they propagate on arithmetic, making it more likely that entire computations become NaN when a single uninitialized value sneaks in. - Arrays are initialized to their homogeneous elements' initialization value, repeated. Stack-based Variable-Length Arrays (VLAs) are runtime-initialized to the allocated size (no effort is made for negative size, but zero-sized VLAs are untouched even if technically undefined). - Structs are initialized to their heterogeneous element's initialization values. Zero-size structs are initialized as 0xAA since they're allocated a single byte. - Unions are initialized using the initialization for the largest member of the union. Expect the values used for pattern initialization to change over time, as we refine heuristics (both for performance and security). The goal is truly to avoid injecting semantics into undefined behavior, and we should be comfortable changing these values when there's a worthwhile point in doing so. Why so much infinite scream? Repeated byte patterns tend to be easy to synthesize on most architectures, and otherwise memset is usually very efficient. For values which aren't entirely repeated byte patterns, LLVM will often generate code which does memset + a few stores. 2. Zero initialization Zero initialize all values. This has the unfortunate side-effect of providing semantics to otherwise undefined behavior, programs therefore might start to rely on this behavior, and that's sad. However, some programmers believe that pattern initialization is too expensive for them, and data might show that they're right. The only way to make these programmers wrong is to offer zero-initialization as an option, figure out where they are right, and optimize the compiler into submission. Until the compiler provides acceptable performance for all security-minded code, zero initialization is a useful (if blunt) tool. I've been asked for a fourth initialization option: user-provided byte value. This might be useful, and can easily be added later. Why is an out-of band initialization mecanism desired? We could instead use -Wuninitialized! Indeed we could, but then we're forcing the programmer to provide semantics for something which doesn't actually have any (it's uninitialized!). It's then unclear whether `int derp = 0;` lends meaning to `0`, or whether it's just there to shut that warning up. It's also way easier to use a compiler flag than it is to manually and intelligently initialize all values in a program. Why not just rely on static analysis? Because it cannot reason about all dynamic code paths effectively, and it has false positives. It's a great tool, could get even better, but it's simply incapable of catching all uses of uninitialized values. Why not just rely on memory sanitizer? Because it's not universally available, has a 3x performance cost, and shouldn't be deployed in production. Again, it's a great tool, it'll find the dynamic uses of uninitialized variables that your test coverage hits, but it won't find the ones that you encounter in production. What's the performance like? Not too bad! Previous publications [0] have cited 2.7 to 4.5% averages. We've commmitted a few patches over the last few months to address specific regressions, both in code size and performance. In all cases, the optimizations are generally useful, but variable initialization benefits from them a lot more than regular code does. We've got a handful of other optimizations in mind, but the code is in good enough shape and has found enough latent issues that it's a good time to get the change reviewed, checked in, and have others kick the tires. We'll continue reducing overheads as we try this out on diverse codebases. Is it a good idea? Security-minded folks think so, and apparently so does the Microsoft Visual Studio team [1] who say "Between 2017 and mid 2018, this feature would have killed 49 MSRC cases that involved uninitialized struct data leaking across a trust boundary. It would have also mitigated a number of bugs involving uninitialized struct data being used directly.". They seem to use pure zero initialization, and claim to have taken the overheads down to within noise. Don't just trust Microsoft though, here's another relevant person asking for this [2]. It's been proposed for GCC [3] and LLVM [4] before. What are the caveats? A few! - Variables declared in unreachable code, and used later, aren't initialized. This goto, Duff's device, other objectionable uses of switch. This should instead be a hard-error in any serious codebase. - Volatile stack variables are still weird. That's pre-existing, it's really the language's fault and this patch keeps it weird. We should deprecate volatile [5]. - As noted above, padding isn't fully handled yet. I don't think these caveats make the patch untenable because they can be addressed separately. Should this be on by default? Maybe, in some circumstances. It's a conversation we can have when we've tried it out sufficiently, and we're confident that we've eliminated enough of the overheads that most codebases would want to opt-in. Let's keep our precious undefined behavior until that point in time. How do I use it: 1. On the command-line: -ftrivial-auto-var-init=uninitialized (the default) -ftrivial-auto-var-init=pattern -ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang 2. Using an attribute: int dont_initialize_me __attribute((uninitialized)); [0]: https://users.elis.ugent.be/~jsartor/researchDocs/OOPSLA2011Zero-submit.pdf [1]: https://twitter.com/JosephBialek/status/1062774315098112001 [2]: https://outflux.net/slides/2018/lss/danger.pdf [3]: https://gcc.gnu.org/ml/gcc-patches/2014-06/msg00615.html [4]: https://github.com/AndroidHardeningArchive/platform_external_clang/commit/776a0955ef6686d23a82d2e6a3cbd4a6a882c31c [5]: http://wg21.link/p1152 I've also posted an RFC to cfe-dev: http://lists.llvm.org/pipermail/cfe-dev/2018-November/060172.html <rdar://problem/39131435> Reviewers: pcc, kcc, rsmith Subscribers: JDevlieghere, jkorous, dexonsmith, cfe-commits Differential Revision: https://reviews.llvm.org/D54604 llvm-svn: 349442
* [darwin] parse the SDK settings from SDKSettings.json if it exists andAlex Lorenz2018-12-171-0/+3
| | | | | | | | | | | | | | | | | | | | pass in the -target-sdk-version to the compiler and backend This commit adds support for reading the SDKSettings.json file in the Darwin driver. This file is used by the driver to determine the SDK's version, and it uses that information to pass it down to the compiler using the new -target-sdk-version= option. This option is then used to set the appropriate SDK Version module metadata introduced in r349119. Note: I had to adjust the two ast tests as the SDKROOT environment variable on macOS caused SDK version to be picked up for the compilation of source file but not the AST. rdar://45774000 Differential Revision: https://reviews.llvm.org/D55673 llvm-svn: 349380
* [Clang] Add __builtin_launderEric Fiselier2018-12-141-0/+46
| | | | | | | | | | | | | | | | | Summary: This patch adds `__builtin_launder`, which is required to implement `std::launder`. Additionally GCC provides `__builtin_launder`, so thing brings Clang in-line with GCC. I'm not exactly sure what magic `__builtin_launder` requires, but based on previous discussions this patch applies a `@llvm.invariant.group.barrier`. As noted in previous discussions, this may not be enough to correctly handle vtables. Reviewers: rnk, majnemer, rsmith Reviewed By: rsmith Subscribers: kristina, Romain-Geissler-1A, erichkeane, amharc, jroelofs, cfe-commits, Prazek Differential Revision: https://reviews.llvm.org/D40218 llvm-svn: 349195
* [OPENMP][NVPTX]Improved interwarp copy function.Alexey Bataev2018-12-141-33/+12
| | | | | | | | | Inlined runtime with the current implementation of the interwarp copy function leads to the undefined behavior because of the not quite correct implementation of the barriers. Start using generic __kmpc_barier function instead of the custom made barriers. llvm-svn: 349192
* Implement -frecord-command-line (-frecord-gcc-switches)Scott Linder2018-12-142-0/+16
| | | | | | | | | | | | | | | | | | | | | | | | Implement options in clang to enable recording the driver command-line in an ELF section. Implement a new special named metadata, llvm.commandline, to support frontends embedding their command-line options in IR/ASM/ELF. This differs from the GCC implementation in some key ways: * In GCC there is only one command-line possible per compilation-unit, in LLVM it mirrors llvm.ident and multiple are allowed. * In GCC individual options are separated by NULL bytes, in LLVM entire command-lines are separated by NULL bytes. The advantage of the GCC approach is to clearly delineate options in the face of embedded spaces. The advantage of the LLVM approach is to support merging multiple command-lines unambiguously, while handling embedded spaces with escaping. Differential Revision: https://reviews.llvm.org/D54487 Clang Differential Revision: https://reviews.llvm.org/D54489 llvm-svn: 349155
* [Builltins][X86] Provide implementations of __lzcnt16, __lzcnt, __lzcnt64 ↵Craig Topper2018-12-141-0/+15
| | | | | | | | | | | | | | | | | | for MS compatibility. Remove declarations from intrin.h and implementations from lzcntintrin.h intrin.h had forward declarations for these and lzcntintrin.h had implementations that were only available with -mlzcnt or a -march that supported the lzcnt feature. For MS compatibility we should always have these builtins available regardless of X86 being the target or the CPU support the lzcnt instruction. The backends should be able to gracefully fallback to something support even if its just shifts and bit ops. Unfortunately, gcc also implements 2 of the 3 function names here on X86 when lzcnt feature is enabled. This patch adds builtins for these for MSVC compatibility and drops the forward declarations from intrin.h. To keep the gcc compatibility the two intrinsics that collided have been turned into macros that use the X86 specific builtins with the lzcnt feature check. These macros are only defined when _MSC_VER is not defined. Without them being macros we can get a redefinition error because -ms-extensions doesn't seem to set _MSC_VER but does make the MS builtins available. Should fix PR40014 Differential Revision: https://reviews.llvm.org/D55677 llvm-svn: 349098
* [CUDA] Make all host-side shadows of device-side variables undef.Artem Belevich2018-12-131-2/+9
| | | | | | | | | | The host-side code can't (and should not) access the values that may only exist on the device side. E.g. address of a __device__ function does not exist on the host side as we don't generate the code for it there. Differential Revision: https://reviews.llvm.org/D55663 llvm-svn: 349087
* Reinstate DW_AT_comp_dir support after D55519.Adrian Prantl2018-12-131-7/+11
| | | | | | | | | | | | The DIFile used by the CU is special and distinct from the main source file. Its directory part specifies what becomes the DW_AT_comp_dir (the compilation directory), even if the source file was specified with an absolute path. To support the .dwo workflow, a valid DW_AT_comp_dir is necessary even if source files were specified with an absolute path. llvm-svn: 349065
* [OpenCL] Add generic AS to 'this' pointerMikael Nilsson2018-12-136-14/+34
| | | | | | | | | | | | | Address spaces are cast into generic before invoking the constructor. Added support for a trailing Qualifiers object in FunctionProtoType. Note: This recommits the previously reverted patch, but now it is commited together with a fix for lldb. Differential Revision: https://reviews.llvm.org/D54862 llvm-svn: 349019
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