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This loosens the requirement of no passthrough function attribute being present to checking for specific attributes that prevent inlining. Since these attributes are no longer strictly passthrough, they should eventually be upgraded to some form of addressable attributes.

This loosens the requirement of no passthrough function attribute being
present to checking for specific attributes that prevent inlining. Since
these attributes are no longer strictly passthrough, they should
eventually be upgraded to some form of addressable attributes.
@definelicht definelicht changed the title [MLIR][LLVM] Disallow inlining for selected function attributes. Disallow inlining for selected function attributes Feb 15, 2023
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definelicht commented Feb 15, 2023

@gysit @Dinistro I tried making the change as innocent as possible, while not being dishonest ("should be upgraded..."). As Tobias also concluded, there doesn't seem to be an easy way of getting these strings from an enumeration, so it would be ideal to not solve this before there's a fully fledged solution for passthroughs.

definelicht pushed a commit that referenced this pull request Mar 20, 2023
This patch adds patterns to reduce redundant mov and sel instructions
for shift intrinsics with FalseLanesZero mode, when
FeatureExperimentalZeroingPseudosis supported.

For example, before:

mov     z1.b, #0
sel     z0.b, p0, z0.b, z1.b
asr     z0.b, p0/m, z0.b, #7
After:

movprfx z0.b, p0/z, z0.b
asr     z0.b, p0/m, z0.b, #7

Reviewed By: paulwalker-arm
Differential Revision: https://reviews.llvm.org/D145551
gysit pushed a commit that referenced this pull request Mar 23, 2023
This change prevents rare deadlocks observed for specific macOS/iOS GUI
applications which issue many `dlopen()` calls from multiple different
threads at startup and where TSan finds and reports a race during
startup.  Providing a reliable test for this has been deemed infeasible.

Although I've only observed this deadlock on Apple platforms,
conceptually the cause is not confined to Apple code so the fix lives in
platform-independent code.

Deadlock scenario:
```
Thread 2                    | Thread 4
ReportRace()                |
Lock internal TSan mutexes  |
  &ctx->slot_mtx            |
                            | dlopen() interceptor
                            | OnLibraryLoaded()
                            | MemoryMappingLayout::DumpListOfModules()
                            | calls dyld API, which takes internal lock
                            | lock() interceptor
                            | TSan tries to take internal mutexes again
                            |   &ctx->slot_mtx
call into symbolizer        |
MemoryMappingLayout::DumpListOfModules()
calls dyld API, which hangs on trying to take lock
```
Resulting in:
* Thread 2 has internal TSan mutex, blocked on dyld lock
* Thread 4 has dyld lock, blocked on internal TSan mutex

The fix prevents this situation by not intercepting any of the calls
originating from `MemoryMappingLayout::DumpListOfModules()`.

Stack traces for deadlock between ReportRace() and dlopen() interceptor:
```
thread #2, queue = 'com.apple.root.default-qos'
  frame #0: libsystem_kernel.dylib
  frame #1: libclang_rt.tsan_osx_dynamic.dylib`::wrap_os_unfair_lock_lock_with_options(lock=<unavailable>, options=<unavailable>) at tsan_interceptors_mac.cpp:306:3
  frame #2: dyld`dyld4::RuntimeLocks::withLoadersReadLock(this=0x000000016f21b1e0, work=0x00000001814523c0) block_pointer) at DyldRuntimeState.cpp:227:28
  frame #3: dyld`dyld4::APIs::_dyld_get_image_header(this=0x0000000101012a20, imageIndex=614) at DyldAPIs.cpp:240:11
  frame #4: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::MemoryMappingLayout::CurrentImageHeader(this=<unavailable>) at sanitizer_procmaps_mac.cpp:391:35
  frame #5: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::MemoryMappingLayout::Next(this=0x000000016f2a2800, segment=0x000000016f2a2738) at sanitizer_procmaps_mac.cpp:397:51
  frame #6: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::MemoryMappingLayout::DumpListOfModules(this=0x000000016f2a2800, modules=0x00000001011000a0) at sanitizer_procmaps_mac.cpp:460:10
  frame #7: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::ListOfModules::init(this=0x00000001011000a0) at sanitizer_mac.cpp:610:18
  frame #8: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::Symbolizer::FindModuleForAddress(unsigned long) [inlined] __sanitizer::Symbolizer::RefreshModules(this=0x0000000101100078) at sanitizer_symbolizer_libcdep.cpp:185:12
  frame #9: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::Symbolizer::FindModuleForAddress(this=0x0000000101100078, address=6465454512) at sanitizer_symbolizer_libcdep.cpp:204:5
  frame #10: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::Symbolizer::SymbolizePC(this=0x0000000101100078, addr=6465454512) at sanitizer_symbolizer_libcdep.cpp:88:15
  frame #11: libclang_rt.tsan_osx_dynamic.dylib`__tsan::SymbolizeCode(addr=6465454512) at tsan_symbolize.cpp:106:35
  frame #12: libclang_rt.tsan_osx_dynamic.dylib`__tsan::SymbolizeStack(trace=StackTrace @ 0x0000600002d66d00) at tsan_rtl_report.cpp:112:28
  frame #13: libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedReportBase::AddMemoryAccess(this=0x000000016f2a2a90, addr=4381057136, external_tag=<unavailable>, s=<unavailable>, tid=<unavailable>, stack=<unavailable>, mset=0x00000001012fc310) at tsan_rtl_report.cpp:190:16
  frame #14: libclang_rt.tsan_osx_dynamic.dylib`__tsan::ReportRace(thr=0x00000001012fc000, shadow_mem=0x000008020a4340e0, cur=<unavailable>, old=<unavailable>, typ0=1) at tsan_rtl_report.cpp:795:9
  frame #15: libclang_rt.tsan_osx_dynamic.dylib`__tsan::DoReportRace(thr=0x00000001012fc000, shadow_mem=0x000008020a4340e0, cur=Shadow @ x22, old=Shadow @ 0x0000600002d6b4f0, typ=1) at tsan_rtl_access.cpp:166:3
  frame #16: libclang_rt.tsan_osx_dynamic.dylib`::__tsan_read8(void *) at tsan_rtl_access.cpp:220:5
  frame #17: libclang_rt.tsan_osx_dynamic.dylib`::__tsan_read8(void *) [inlined] __tsan::MemoryAccess(thr=0x00000001012fc000, pc=<unavailable>, addr=<unavailable>, size=8, typ=1) at tsan_rtl_access.cpp:442:3
  frame llvm#18: libclang_rt.tsan_osx_dynamic.dylib`::__tsan_read8(addr=<unavailable>) at tsan_interface.inc:34:3
  <call into TSan from from instrumented code>

thread #4, queue = 'com.apple.dock.fullscreen'
  frame #0:  libsystem_kernel.dylib
  frame #1:  libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::FutexWait(p=<unavailable>, cmp=<unavailable>) at sanitizer_mac.cpp:540:3
  frame #2:  libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::Semaphore::Wait(this=<unavailable>) at sanitizer_mutex.cpp:35:7
  frame #3:  libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::Mutex::Lock(this=0x0000000102992a80) at sanitizer_mutex.h:196:18
  frame #4:  libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor() [inlined] __sanitizer::GenericScopedLock<__sanitizer::Mutex>::GenericScopedLock(this=<unavailable>, mu=0x0000000102992a80) at sanitizer_mutex.h:383:10
  frame #5:  libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor() [inlined] __sanitizer::GenericScopedLock<__sanitizer::Mutex>::GenericScopedLock(this=<unavailable>, mu=0x0000000102992a80) at sanitizer_mutex.h:382:77
  frame #6:  libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor() at tsan_rtl.h:708:10
  frame #7:  libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor() [inlined] __tsan::TryTraceFunc(thr=0x000000010f084000, pc=0) at tsan_rtl.h:751:7
  frame #8:  libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor() [inlined] __tsan::FuncExit(thr=0x000000010f084000) at tsan_rtl.h:798:7
  frame #9:  libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor(this=0x000000016f3ba280) at tsan_interceptors_posix.cpp:300:5
  frame #10: libclang_rt.tsan_osx_dynamic.dylib`__tsan::ScopedInterceptor::~ScopedInterceptor(this=<unavailable>) at tsan_interceptors_posix.cpp:293:41
  frame #11: libclang_rt.tsan_osx_dynamic.dylib`::wrap_os_unfair_lock_lock_with_options(lock=0x000000016f21b1e8, options=OS_UNFAIR_LOCK_NONE) at tsan_interceptors_mac.cpp:310:1
  frame #12: dyld`dyld4::RuntimeLocks::withLoadersReadLock(this=0x000000016f21b1e0, work=0x00000001814525d4) block_pointer) at DyldRuntimeState.cpp:227:28
  frame #13: dyld`dyld4::APIs::_dyld_get_image_vmaddr_slide(this=0x0000000101012a20, imageIndex=412) at DyldAPIs.cpp:273:11
  frame #14: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::MemoryMappingLayout::Next(__sanitizer::MemoryMappedSegment*) at sanitizer_procmaps_mac.cpp:286:17
  frame #15: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::MemoryMappingLayout::Next(this=0x000000016f3ba560, segment=0x000000016f3ba498) at sanitizer_procmaps_mac.cpp:432:15
  frame #16: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::MemoryMappingLayout::DumpListOfModules(this=0x000000016f3ba560, modules=0x000000016f3ba618) at sanitizer_procmaps_mac.cpp:460:10
  frame #17: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::ListOfModules::init(this=0x000000016f3ba618) at sanitizer_mac.cpp:610:18
  frame llvm#18: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::LibIgnore::OnLibraryLoaded(this=0x0000000101f3aa40, name="<some library>") at sanitizer_libignore.cpp:54:11
  frame llvm#19: libclang_rt.tsan_osx_dynamic.dylib`::wrap_dlopen(filename="<some library>", flag=<unavailable>) at sanitizer_common_interceptors.inc:6466:3
  <library code>
```

rdar://106766395

Differential Revision: https://reviews.llvm.org/D146593
definelicht pushed a commit that referenced this pull request Mar 23, 2023
I noticed, when examining the generated Asm Matcher table, that some of
these custom immediate operands are missing, and so we are not parsing
some hint aliases into the correct MCInst.

Where this becomes apparent is when you parse e.g. `hint #7` into an
MCInst - without these cases, it becomes the MCInst `(HINT 17)`, which
will always be printed as `hint #17`. With these cases, it becomes the
MCInst `XPACLRI`, which will be printed as `xpaclri` with pauth, or
`hint #17` without, matching how `xpaclri` is parsed.

We only handle some specific hint aliases in this manner, usually where
these hints have specific effects that need to be modelled for accurate
code-generation. Otherwise, we just use the normal `InstAlias` system
to have the aliases parsed into a `(HINT N)` MCInst.

Differential Revision: https://reviews.llvm.org/D146630
definelicht pushed a commit that referenced this pull request May 9, 2023
…callback

The `TypeSystemMap::m_mutex` guards against concurrent modifications
of members of `TypeSystemMap`. In particular, `m_map`.

`TypeSystemMap::ForEach` iterates through the entire `m_map` calling
a user-specified callback for each entry. This is all done while
`m_mutex` is locked. However, there's nothing that guarantees that
the callback itself won't call back into `TypeSystemMap` APIs on the
same thread. This lead to double-locking `m_mutex`, which is undefined
behaviour. We've seen this cause a deadlock in the swift plugin with
following backtrace:

```

int main() {
    std::unique_ptr<int> up = std::make_unique<int>(5);

    volatile int val = *up;
    return val;
}

clang++ -std=c++2a -g -O1 main.cpp

./bin/lldb -o “br se -p return” -o run -o “v *up” -o “expr *up” -b
```

```
frame #4: std::lock_guard<std::mutex>::lock_guard
frame #5: lldb_private::TypeSystemMap::GetTypeSystemForLanguage <<<< Lock #2
frame #6: lldb_private::TypeSystemMap::GetTypeSystemForLanguage
frame #7: lldb_private::Target::GetScratchTypeSystemForLanguage
...
frame llvm#26: lldb_private::SwiftASTContext::LoadLibraryUsingPaths
frame llvm#27: lldb_private::SwiftASTContext::LoadModule
frame llvm#30: swift::ModuleDecl::collectLinkLibraries
frame llvm#31: lldb_private::SwiftASTContext::LoadModule
frame llvm#34: lldb_private::SwiftASTContext::GetCompileUnitImportsImpl
frame llvm#35: lldb_private::SwiftASTContext::PerformCompileUnitImports
frame llvm#36: lldb_private::TypeSystemSwiftTypeRefForExpressions::GetSwiftASTContext
frame llvm#37: lldb_private::TypeSystemSwiftTypeRefForExpressions::GetPersistentExpressionState
frame llvm#38: lldb_private::Target::GetPersistentSymbol
frame llvm#41: lldb_private::TypeSystemMap::ForEach                 <<<< Lock #1
frame llvm#42: lldb_private::Target::GetPersistentSymbol
frame llvm#43: lldb_private::IRExecutionUnit::FindInUserDefinedSymbols
frame llvm#44: lldb_private::IRExecutionUnit::FindSymbol
frame llvm#45: lldb_private::IRExecutionUnit::MemoryManager::GetSymbolAddressAndPresence
frame llvm#46: lldb_private::IRExecutionUnit::MemoryManager::findSymbol
frame llvm#47: non-virtual thunk to lldb_private::IRExecutionUnit::MemoryManager::findSymbol
frame llvm#48: llvm::LinkingSymbolResolver::findSymbol
frame llvm#49: llvm::LegacyJITSymbolResolver::lookup
frame llvm#50: llvm::RuntimeDyldImpl::resolveExternalSymbols
frame llvm#51: llvm::RuntimeDyldImpl::resolveRelocations
frame llvm#52: llvm::MCJIT::finalizeLoadedModules
frame llvm#53: llvm::MCJIT::finalizeObject
frame llvm#54: lldb_private::IRExecutionUnit::ReportAllocations
frame llvm#55: lldb_private::IRExecutionUnit::GetRunnableInfo
frame llvm#56: lldb_private::ClangExpressionParser::PrepareForExecution
frame llvm#57: lldb_private::ClangUserExpression::TryParse
frame llvm#58: lldb_private::ClangUserExpression::Parse
```

Our solution is to simply iterate over a local copy of `m_map`.

**Testing**

* Confirmed on manual reproducer (would reproduce 100% of the time
  before the patch)

Differential Revision: https://reviews.llvm.org/D149949
definelicht pushed a commit that referenced this pull request Dec 13, 2023
… on (llvm#74207)

lld string tail merging interacts badly with ASAN on Windows, as is
reported in llvm#62078.
A similar error was found when building LLVM with
`-DLLVM_USE_SANITIZER=Address`:
```console
[2/2] Building GenVT.inc...
FAILED: include/llvm/CodeGen/GenVT.inc C:/Dev/llvm-project/Build_asan/include/llvm/CodeGen/GenVT.inc
cmd.exe /C "cd /D C:\Dev\llvm-project\Build_asan && C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe -gen-vt -I C:/Dev/llvm-project/llvm/include/llvm/CodeGen -IC:/Dev/llvm-project/Build_asan/include -IC:/Dev/llvm-project/llvm/include C:/Dev/llvm-project/llvm/include/llvm/CodeGen/ValueTypes.td --write-if-changed -o include/llvm/CodeGen/GenVT.inc -d include/llvm/CodeGen/GenVT.inc.d"       
=================================================================
==31944==ERROR: AddressSanitizer: global-buffer-overflow on address 0x7ff6cff80d20 at pc 0x7ff6cfcc7378 bp 0x00e8bcb8e990 sp 0x00e8bcb8e9d8
READ of size 1 at 0x7ff6cff80d20 thread T0
    #0 0x7ff6cfcc7377 in strlen (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1400a7377)
    #1 0x7ff6cfde50c2 in operator delete(void *, unsigned __int64) (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1401c50c2)
    #2 0x7ff6cfdd75ef in operator delete(void *, unsigned __int64) (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1401b75ef)
    #3 0x7ff6cfde59f9 in operator delete(void *, unsigned __int64) (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1401c59f9)
    #4 0x7ff6cff03f6c in operator delete(void *, unsigned __int64) (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1402e3f6c)
    #5 0x7ff6cfefbcbc in operator delete(void *, unsigned __int64) (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1402dbcbc)
    #6 0x7ffb7f247343  (C:\WINDOWS\System32\KERNEL32.DLL+0x180017343)
    #7 0x7ffb800826b0  (C:\WINDOWS\SYSTEM32\ntdll.dll+0x1800526b0)

0x7ff6cff80d20 is located 31 bytes after global variable '"#error \"ArgKind is not defined\"\n"...' defined in 'C:\Dev\llvm-project\llvm\utils\TableGen\IntrinsicEmitter.cpp' (0x7ff6cff80ce0) of size 33
  '"#error \"ArgKind is not defined\"\n"...' is ascii string '#error "ArgKind is not defined"
'
0x7ff6cff80d20 is located 0 bytes inside of global variable '""' defined in 'C:\Dev\llvm-project\llvm\utils\TableGen\IntrinsicEmitter.cpp' (0x7ff6cff80d20) of size 1
  '""' is ascii string ''
SUMMARY: AddressSanitizer: global-buffer-overflow (C:\Dev\llvm-project\Build_asan\bin\llvm-min-tblgen.exe+0x1400a7377) in strlen
Shadow bytes around the buggy address:
  0x7ff6cff80a80: 01 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 01 f9 f9 f9
  0x7ff6cff80b00: f9 f9 f9 f9 00 00 00 00 00 00 00 00 01 f9 f9 f9
  0x7ff6cff80b80: f9 f9 f9 f9 00 00 00 00 01 f9 f9 f9 f9 f9 f9 f9
  0x7ff6cff80c00: 00 00 00 00 01 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
  0x7ff6cff80c80: 00 00 00 00 01 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
=>0x7ff6cff80d00: 01 f9 f9 f9[f9]f9 f9 f9 00 00 00 00 00 00 00 00
  0x7ff6cff80d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7ff6cff80e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7ff6cff80e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7ff6cff80f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7ff6cff80f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==31944==ABORTING
```
This is reproducible with the 17.0.3 release:
```console
$ clang-cl --version
clang version 17.0.3
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:\Program Files\LLVM\bin
$ cmake -S llvm -B Build -G Ninja -DLLVM_USE_SANITIZER=Address -DCMAKE_C_COMPILER=clang-cl -DCMAKE_CXX_COMPILER=clang-cl -DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded -DCMAKE_BUILD_TYPE=Release
$ cd Build
$ ninja all
```
definelicht pushed a commit that referenced this pull request Jan 5, 2024
This has been flaky for a while, for example
https://lab.llvm.org/buildbot/#/builders/96/builds/50350

```
Command Output (stdout):
--
lldb version 18.0.0git (https://github.com/llvm/llvm-project.git revision 3974d89)
  clang revision 3974d89
  llvm revision 3974d89
"can't evaluate expressions when the process is running."
```

```
  PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
   #0 0x0000ffffa46191a0 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x529a1a0)
   #1 0x0000ffffa4617144 llvm::sys::RunSignalHandlers() (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x5298144)
   #2 0x0000ffffa46198d0 SignalHandler(int) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x529a8d0)
   #3 0x0000ffffab25b7dc (linux-vdso.so.1+0x7dc)
   #4 0x0000ffffab13d050 /build/glibc-Q8DG8B/glibc-2.31/string/../sysdeps/aarch64/multiarch/memcpy_advsimd.S:92:0
   #5 0x0000ffffa446f420 lldb_private::process_gdb_remote::GDBRemoteRegisterContext::PrivateSetRegisterValue(unsigned int, llvm::ArrayRef<unsigned char>) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x50f0420)
   #6 0x0000ffffa446f7b8 lldb_private::process_gdb_remote::GDBRemoteRegisterContext::GetPrimordialRegister(lldb_private::RegisterInfo const*, lldb_private::process_gdb_remote::GDBRemoteCommunicationClient&) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x50f07b8)
   #7 0x0000ffffa446f308 lldb_private::process_gdb_remote::GDBRemoteRegisterContext::ReadRegisterBytes(lldb_private::RegisterInfo const*) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x50f0308)
   #8 0x0000ffffa446ec1c lldb_private::process_gdb_remote::GDBRemoteRegisterContext::ReadRegister(lldb_private::RegisterInfo const*, lldb_private::RegisterValue&) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x50efc1c)
   #9 0x0000ffffa412eaa4 lldb_private::RegisterContext::ReadRegisterAsUnsigned(lldb_private::RegisterInfo const*, unsigned long) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x4dafaa4)
  #10 0x0000ffffa420861c ReadLinuxProcessAddressMask(std::shared_ptr<lldb_private::Process>, llvm::StringRef) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x4e8961c)
  #11 0x0000ffffa4208430 ABISysV_arm64::FixCodeAddress(unsigned long) (/home/tcwg-buildbot/worker/lldb-aarch64-ubuntu/build/lib/python3.8/site-packages/lldb/_lldb.cpython-38-aarch64-linux-gnu.so+0x4e89430)
```

Judging by the backtrace something is trying to read the pointer authentication address/code mask
registers. This explains why I've not seen this issue locally, as the buildbot runs on Graviton
3 with has the pointer authentication extension.

I will try to reproduce, fix and re-enable the test.
definelicht pushed a commit that referenced this pull request Jan 18, 2024
…8055)

This fixes a crash where `path::parent_path` causes an invalid access on
a string upon receiving a path that consists of a single colon.

On Windows machine, with runtime checks enabled build, upon `clang -I:
test.cc` produces:
```
Assertion failed: Index < Length && "Invalid index!", file llvm\include\llvm/ADT/StringRef.h, line 232
...
 #6 0x00007ff7816201eb `anonymous namespace'::parent_path_end llvm\lib\Support\Path.cpp:144:0
 #7 0x00007ff781620135 llvm::sys::path::parent_path(class llvm::StringRef, enum llvm::sys::path::Style) llvm\lib\Support\Path.cpp:470:0
```

Ideally, we can look for the last colon starting from the last
character, but we can instead start from second to last, and handle
empty paths by abusing `0 - 1 == npos`.
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