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[pull] main from MaxMood96:main #18

Merged
merged 29 commits into from
Aug 28, 2021
Merged

[pull] main from MaxMood96:main #18

merged 29 commits into from
Aug 28, 2021

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@pull pull bot commented Aug 27, 2021

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Created by pull[bot]

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lhames and others added 29 commits August 27, 2021 14:41
This should fix the bot error in
https://lab.llvm.org/buildbot/#/builders/112/builds/8599
which forced reversion of the ELFNixPlatform in 45ac5f5.

This should allow us to re-enable the ELFNixPlatform in a follow-up patch.
…th fixes.

This reapplies e256445, which was reverted in 45ac5f5 due to bot errors
(e.g. https://lab.llvm.org/buildbot/#/builders/112/builds/8599). The issue that
caused the bot failure was fixed in 2e6a4fc.
Currently, it is a bit buried in the file even if this is
pretty important for distro.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D108533
Not only global variables can hold references to dead stack variables.
Consider this example:

  void write_stack_address_to(char **q) {
    char local;
    *q = &local;
  }

  void test_stack() {
    char *p;
    write_stack_address_to(&p);
  }

The address of 'local' is assigned to 'p', which becomes a dangling
pointer after 'write_stack_address_to()' returns.

The StackAddrEscapeChecker was looking for bindings in the store which
referred to variables of the popped stack frame, but it only considered
global variables in this regard. This patch relaxes this, catching
stack variable bindings as well.

---

This patch also works for temporary objects like:

  struct Bar {
    const int &ref;
    explicit Bar(int y) : ref(y) {
      // Okay.
    } // End of the constructor call, `ref` is dangling now. Warning!
  };

  void test() {
    Bar{33}; // Temporary object, so the corresponding memregion is
             // *not* a VarRegion.
  }

---

The return value optimization aka. copy-elision might kick in but that
is modeled by passing an imaginary CXXThisRegion which refers to the
parent stack frame which is supposed to be the 'return slot'.
Objects residing in the 'return slot' outlive the scope of the inner
call, thus we should expect no warning about them - except if we
explicitly disable copy-elision.

Reviewed By: NoQ, martong

Differential Revision: https://reviews.llvm.org/D107078
…tudio page

Since Visual Studio 2017 the DIA libs are not registered by default, see:
https://docs.microsoft.com/en-us/visualstudio/extensibility/breaking-changes-2017?view=vs-2019#change-reduce-registry-impact
LLDB building instruction already specify registering these DLLs, required
both the LLVM PDB tests and LLDB build.

Differential Revision: https://reviews.llvm.org/D108811
…r high part

As per llvm-exegesis measurements.
…reg op

Exegesis is faulty and sometimes when measuring throughput^-1
produces snippets that have loop-carried dependencies,
which must be what caused me to incorrectly measure it originally.

After looking much more carefully, the inverse throughput should match
that of the MULX w/ reg op.

As per llvm-exegesis measurements.
Fixes PR51626.

The M68k requires that all instruction, word and long word reads are
aligned to word boundaries. From the 68020 onwards, there is a
performance benefit from aligning long words to long word boundaries.

The M68k uses the same data layout for pointers and integers.

In line with this, this commit updates the pointer data layout to
match the layout already set for 32-bit integers: 32:16:32.

Differential Revision: https://reviews.llvm.org/D108792
Without this change only the preferred fusion opcode is tested
when attempting to combine FMA operations.
If both FMA and FMAD are available then FMA ops formed prior to
legalization will not be merged post legalization as FMAD becomes
the preferred fusion opcode.

Reviewed By: foad

Differential Revision: https://reviews.llvm.org/D108619
There are no paths into LowerFormalParms that have already specified
the sret register. We always materialize a virtual and then assign it
to the physical reg at the point of the return.

Differential Revision: https://reviews.llvm.org/D108762
x86_fp80 format allows values that do not fit any of IEEE-754 category.
Previously they were recognized by intrinsic __builtin_isnan as NaNs.
Now this intrinsic is implemented using instruction FXAM, which
distinguish between NaNs and unsupported values. It can make some
programs behave differently.

As a solution, this fix changes lowering of the intrinsic. If floating
point exceptions are ignored, llvm.isnan is lowered into unordered
comparison, as __buildtin_isnan was implemented earlier. In strictfp
functions the intrinsic is lowered using FXAM, which does not raise
exceptions even for signaling NaN, as required by IEEE-754 and C
standards.

Differential Revision: https://reviews.llvm.org/D108037
Lets wavefront size be 32 for amdgpu openmp, as well as 64.

Fixes up as little as possible to pass that through the libraries. This change
is end to end, as opposed to updating clang/devicertl/plugin separately. It can
be broken up for review/commit if preferred. Posting as-is so that others with
a gfx10 can try it out. It works roughly as well as gfx9 for me, but there are
probably bugs remaining as well as the todo: for letting grid values vary more.

Reviewed By: ronlieb

Differential Revision: https://reviews.llvm.org/D108708
The coverity issue was reported agaist class MCAOperand
due to the lack of proper initialization for field Index.

No functional change intended.
…nd element number. NFC

This patch solely moves convert operation between SVE predicate pattern
and element number into two small functions. It's pre-commit patch for optimize
pture with known sve register width.

Differential Revision: https://reviews.llvm.org/D108705
…er width.

For vectors that are exactly equal to getMaxSVEVectorSizeInBits, just use
AArch64SVEPredPattern::all, which can enable the use of unpredicated ptrue when available.

TestPlan: check-llvm

Differential Revision: https://reviews.llvm.org/D108706
We try to forward a stored-once-constant-value from one global access
to another, but that's not safe if the constant value is an expression
that can trap.

The tests are reduced from the miscompile examples in:
https://llvm.org/PR47578

Differential Revision: https://reviews.llvm.org/D108771
…malloc

MallocOverflow works in two phases:

1) Collects suspicious malloc calls, whose argument is a multiplication
2) Filters the aggregated list of suspicious malloc calls by iterating
   over the BasicBlocks of the CFG looking for comparison binary
   operators over the variable constituting in any suspicious malloc.

Consequently, it suppressed true-positive cases when the comparison
check was after the malloc call.
In this patch the checker will consider the relative position of the
relation check to the malloc call.

E.g.:

```lang=C++
void *check_after_malloc(int n, int x) {
  int *p = NULL;
  if (x == 42)
    p = malloc(n * sizeof(int)); // Previously **no** warning, now it
                                 // warns about this.

  // The check is after the allocation!
  if (n > 10) {
    // Do something conditionally.
  }
  return p;
}
```

Reviewed By: martong

Differential Revision: https://reviews.llvm.org/D107804
P_priv does the same as the old QF further down. Standardize on P_priv.

No behavior change.

Differential Revision: https://reviews.llvm.org/D108798
We currently complain "could not open /LTCG: no such file or directory",
which isn't very useful.  We could emit a warning when we see this flag, but
just ignoring it seems fine.

Final missing part of PR38799.

Differential Revision: https://reviews.llvm.org/D108799
Add a new option PackConstructorInitializers and deprecate the
related options ConstructorInitializerAllOnOneLineOrOnePerLine and
AllowAllConstructorInitializersOnNextLine. Below is the mapping:

PackConstructorInitializers  ConstructorInitializer... AllowAll...
        Never                            -                  -
        BinPack                        false                -
        CurrentLine                    true               false
        NextLine                       true               true

The option value Never fixes PR50549 by always placing each
constructor initializer on its own line.

Differential Revision: https://reviews.llvm.org/D108752
…on Linux"

This reverts commit abb9563, which broke
the libc++ CI on Linux.
Summary of changes:
- Added f16 omod modifier (bug 51386).
- Corrected names of data types (bug 48638).
- Enabled a16 with most GFX10 MIMG opcodes (see https://reviews.llvm.org/D102231).
- Corrected description of integer operands (bug 51130).
- Corrected description of 8-bit DS offsets (bug 51536).
- Improved PERMLANE op_sel description.
- Corrected *SAD* opcode types.
@pull pull bot added the ⤵️ pull label Aug 27, 2021
@pull pull bot merged commit 8ea3e9d into Mement-Mori:main Aug 28, 2021
pull bot pushed a commit that referenced this pull request Oct 7, 2021
Although THREADLOCAL variables are supported on Darwin they cannot be
used very early on during process init (before dyld has set it up).

Unfortunately the checked lock is used before dyld has setup TLS leading
to an abort call (`_tlv_boostrap()` is never supposed to be called at
runtime).

To avoid this problem `SANITIZER_CHECK_DEADLOCKS` is now disabled on
Darwin platforms. This fixes running TSan tests (an possibly other
Sanitizers) when `COMPILER_RT_DEBUG=ON`.

For reference the crashing backtrace looks like this:

```
* thread #1, stop reason = signal SIGABRT
  * frame #0: 0x00000002044da0ae dyld`__abort_with_payload + 10
    frame #1: 0x00000002044f01af dyld`abort_with_payload_wrapper_internal + 80
    frame #2: 0x00000002044f01e1 dyld`abort_with_payload + 9
    frame #3: 0x000000010c989060 dyld_sim`abort_with_payload + 26
    frame #4: 0x000000010c94908b dyld_sim`dyld4::halt(char const*) + 375
    frame #5: 0x000000010c988f5c dyld_sim`abort + 16
    frame #6: 0x000000010c96104f dyld_sim`dyld4::APIs::_tlv_bootstrap() + 9
    frame #7: 0x000000010cd8d6d2 libclang_rt.tsan_iossim_dynamic.dylib`__sanitizer::CheckedMutex::LockImpl(this=<unavailable>, pc=<unavailable>) at sanitizer_mutex.cpp:218:58 [opt]
    frame #8: 0x000000010cd8a0f7 libclang_rt.tsan_iossim_dynamic.dylib`__sanitizer::Mutex::Lock() [inlined] __sanitizer::CheckedMutex::Lock(this=0x000000010d733c90) at sanitizer_mutex.h:124:5 [opt]
    frame #9: 0x000000010cd8a0ee libclang_rt.tsan_iossim_dynamic.dylib`__sanitizer::Mutex::Lock(this=0x000000010d733c90) at sanitizer_mutex.h:162:19 [opt]
    frame #10: 0x000000010cd8a0bf libclang_rt.tsan_iossim_dynamic.dylib`__sanitizer::GenericScopedLock<__sanitizer::Mutex>::GenericScopedLock(this=0x000000030c7479a8, mu=<unavailable>) at sanitizer_mutex.h:364:10 [opt]
    frame #11: 0x000000010cd89819 libclang_rt.tsan_iossim_dynamic.dylib`__sanitizer::GenericScopedLock<__sanitizer::Mutex>::GenericScopedLock(this=0x000000030c7479a8, mu=<unavailable>) at sanitizer_mutex.h:363:67 [opt]
    frame #12: 0x000000010cd8985b libclang_rt.tsan_iossim_dynamic.dylib`__sanitizer::LibIgnore::OnLibraryLoaded(this=0x000000010d72f480, name=0x0000000000000000) at sanitizer_libignore.cpp:39:8 [opt]
    frame #13: 0x000000010cda7aaa libclang_rt.tsan_iossim_dynamic.dylib`__tsan::InitializeLibIgnore() at tsan_interceptors_posix.cpp:219:16 [opt]
    frame #14: 0x000000010cdce0bb libclang_rt.tsan_iossim_dynamic.dylib`__tsan::Initialize(thr=0x0000000110141400) at tsan_rtl.cpp:403:3 [opt]
    frame #15: 0x000000010cda7b8e libclang_rt.tsan_iossim_dynamic.dylib`__tsan::ScopedInterceptor::ScopedInterceptor(__tsan::ThreadState*, char const*, unsigned long) [inlined] __tsan::LazyInitialize(thr=0x0000000110141400) at tsan_rtl.h:665:5 [opt]
    frame #16: 0x000000010cda7b86 libclang_rt.tsan_iossim_dynamic.dylib`__tsan::ScopedInterceptor::ScopedInterceptor(this=0x000000030c747af8, thr=0x0000000110141400, fname=<unavailable>, pc=4568918787) at tsan_interceptors_posix.cpp:247:3 [opt]
    frame #17: 0x000000010cda7bb9 libclang_rt.tsan_iossim_dynamic.dylib`__tsan::ScopedInterceptor::ScopedInterceptor(this=0x000000030c747af8, thr=<unavailable>, fname=<unavailable>, pc=<unavailable>) at tsan_interceptors_posix.cpp:246:59 [opt]
    frame #18: 0x000000010cdb72b7 libclang_rt.tsan_iossim_dynamic.dylib`::wrap_strlcpy(dst="\xd2", src="0xd1d398d1bb0a007b", size=20) at sanitizer_common_interceptors.inc:7386:3 [opt]
    frame #19: 0x0000000110542b03 libsystem_c.dylib`__guard_setup + 140
    frame #20: 0x00000001104f8ab4 libsystem_c.dylib`_libc_initializer + 65
    ...
```

rdar://83723445

Differential Revision: https://reviews.llvm.org/D111243
pull bot pushed a commit that referenced this pull request Oct 31, 2022
Found by msan -fsanitize-memory-use-after-dtor.

==8259==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x55dbec54d2b8 in dtorRecord(clang::interp::Block*, char*, clang::interp::Descriptor*) clang/lib/AST/Interp/Descriptor.cpp:150:22
    #1 0x55dbec54bfcf in dtorArrayDesc(clang::interp::Block*, char*, clang::interp::Descriptor*) clang/lib/AST/Interp/Descriptor.cpp:97:7
    #2 0x55dbec508578 in invokeDtor clang/lib/AST/Interp/InterpBlock.h:79:7
    #3 0x55dbec508578 in clang::interp::Program::~Program() clang/lib/AST/Interp/Program.h:55:19
    #4 0x55dbec50657a in operator() third_party/crosstool/v18/stable/toolchain/bin/../include/c++/v1/__memory/unique_ptr.h:55:5
    #5 0x55dbec50657a in std::__msan::unique_ptr<clang::interp::Program, std::__msan::default_delete<clang::interp::Program>>::~unique_ptr() third_party/crosstool/v18/stable/toolchain/bin/../include/c++/v1/__memory/unique_ptr.h:261:7
    #6 0x55dbec5035a1 in clang::interp::Context::~Context() clang/lib/AST/Interp/Context.cpp:27:22
    #7 0x55dbebec1daa in operator() third_party/crosstool/v18/stable/toolchain/bin/../include/c++/v1/__memory/unique_ptr.h:55:5
    #8 0x55dbebec1daa in std::__msan::unique_ptr<clang::interp::Context, std::__msan::default_delete<clang::interp::Context>>::~unique_ptr() third_party/crosstool/v18/stable/toolchain/bin/../include/c++/v1/__memory/unique_ptr.h:261:7
    #9 0x55dbebe285f9 in clang::ASTContext::~ASTContext() clang/lib/AST/ASTContext.cpp:1038:40
    #10 0x55dbe941ff13 in llvm::RefCountedBase<clang::ASTContext>::Release() const llvm/include/llvm/ADT/IntrusiveRefCntPtr.h:101:7
    #11 0x55dbe94353ef in release llvm/include/llvm/ADT/IntrusiveRefCntPtr.h:159:38
    #12 0x55dbe94353ef in release llvm/include/llvm/ADT/IntrusiveRefCntPtr.h:224:7
    #13 0x55dbe94353ef in ~IntrusiveRefCntPtr llvm/include/llvm/ADT/IntrusiveRefCntPtr.h:191:27
    #14 0x55dbe94353ef in clang::CompilerInstance::setASTContext(clang::ASTContext*) clang/lib/Frontend/CompilerInstance.cpp:178:3
    #15 0x55dbe95ad0ad in clang::FrontendAction::EndSourceFile() clang/lib/Frontend/FrontendAction.cpp:1100:8
    #16 0x55dbe9445fcf in clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) clang/lib/Frontend/CompilerInstance.cpp:1047:11
    #17 0x55dbe6b3afef in clang::ExecuteCompilerInvocation(clang::CompilerInstance*) clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp:266:25
    #18 0x55dbe6b13288 in cc1_main(llvm::ArrayRef<char const*>, char const*, void*) clang/tools/driver/cc1_main.cpp:250:15
    #19 0x55dbe6b0095f in ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&) clang/tools/driver/driver.cpp:319:12
    #20 0x55dbe6aff41c in clang_main(int, char**) clang/tools/driver/driver.cpp:395:12
    #21 0x7f9be07fa632 in __libc_start_main
    #22 0x55dbe6a702e9 in _start

  Member fields were destroyed
    #0 0x55dbe6a7da5d in __sanitizer_dtor_callback_fields compiler-rt/lib/msan/msan_interceptors.cpp:949:5
    #1 0x55dbec5094ac in ~SmallVectorImpl llvm/include/llvm/ADT/SmallVector.h:479:7
    #2 0x55dbec5094ac in ~SmallVectorImpl llvm/include/llvm/ADT/SmallVector.h:612:3
    #3 0x55dbec5094ac in llvm::SmallVector<clang::interp::Record::Base, 8u>::~SmallVector() llvm/include/llvm/ADT/SmallVector.h:1207:3
    #4 0x55dbec508e79 in clang::interp::Record::~Record() clang/lib/AST/Interp/Record.h:24:7
    #5 0x55dbec508612 in clang::interp::Program::~Program() clang/lib/AST/Interp/Program.h:49:26
    #6 0x55dbec50657a in operator() third_party/crosstool/v18/stable/toolchain/bin/../include/c++/v1/__memory/unique_ptr.h:55:5
    #7 0x55dbec50657a in std::__msan::unique_ptr<clang::interp::Program, std::__msan::default_delete<clang::interp::Program>>::~unique_ptr() third_party/crosstool/v18/stable/toolchain/bin/../include/c++/v1/__memory/unique_ptr.h:261:7
    #8 0x55dbec5035a1 in clang::interp::Context::~Context() clang/lib/AST/Interp/Context.cpp:27:22
    #9 0x55dbebec1daa in operator() third_party/crosstool/v18/stable/toolchain/bin/../include/c++/v1/__memory/unique_ptr.h:55:5
    #10 0x55dbebec1daa in std::__msan::unique_ptr<clang::interp::Context, std::__msan::default_delete<clang::interp::Context>>::~unique_ptr() third_party/crosstool/v18/stable/toolchain/bin/../include/c++/v1/__memory/unique_ptr.h:261:7
    #11 0x55dbebe285f9 in clang::ASTContext::~ASTContext() clang/lib/AST/ASTContext.cpp:1038:40
    #12 0x55dbe941ff13 in llvm::RefCountedBase<clang::ASTContext>::Release() const llvm/include/llvm/ADT/IntrusiveRefCntPtr.h:101:7
    #13 0x55dbe94353ef in release llvm/include/llvm/ADT/IntrusiveRefCntPtr.h:159:38
    #14 0x55dbe94353ef in release llvm/include/llvm/ADT/IntrusiveRefCntPtr.h:224:7
    #15 0x55dbe94353ef in ~IntrusiveRefCntPtr llvm/include/llvm/ADT/IntrusiveRefCntPtr.h:191:27
    #16 0x55dbe94353ef in clang::CompilerInstance::setASTContext(clang::ASTContext*) clang/lib/Frontend/CompilerInstance.cpp:178:3
    #17 0x55dbe95ad0ad in clang::FrontendAction::EndSourceFile() clang/lib/Frontend/FrontendAction.cpp:1100:8
    #18 0x55dbe9445fcf in clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) clang/lib/Frontend/CompilerInstance.cpp:1047:11
    #19 0x55dbe6b3afef in clang::ExecuteCompilerInvocation(clang::CompilerInstance*) clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp:266:25
    #20 0x55dbe6b13288 in cc1_main(llvm::ArrayRef<char const*>, char const*, void*) clang/tools/driver/cc1_main.cpp:250:15
    #21 0x55dbe6b0095f in ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&) clang/tools/driver/driver.cpp:319:12
    #22 0x55dbe6aff41c in clang_main(int, char**) clang/tools/driver/driver.cpp:395:12
    #23 0x7f9be07fa632 in __libc_start_main
    #24 0x55dbe6a702e9 in _start
pull bot pushed a commit that referenced this pull request Dec 20, 2022
…D112621

It seems like `LHS` and `RHS` could be empty range sets.
This caused an assertion failure inside RangeConstraintManager.

I'm hoisting out the check from the function into the call-site.
This way we could assert that we only want to deal with non-empty range
sets.

The relevant part of the trace:
```
 #6 0x00007fe6ff5f81a6 __assert_fail_base (/lib64/libc.so.6+0x2f1a6)
 #7 0x00007fe6ff5f8252 (/lib64/libc.so.6+0x2f252)
 #8 0x00000000049caed2 (anonymous namespace)::SymbolicRangeInferrer::VisitBinaryOperator(clang::ento::RangeSet, clang::BinaryOperatorKind, clang::ento::RangeSet, clang::QualType) RangeConstraintManager.cpp:0:0
 #9 0x00000000049c9867 (anonymous namespace)::SymbolicRangeInferrer::infer(clang::ento::SymExpr const*) RangeConstraintManager.cpp:0:0
#10 0x00000000049bebf5 (anonymous namespace)::RangeConstraintManager::assumeSymNE(llvm::IntrusiveRefCntPtr<clang::ento::ProgramState const>, clang::ento::SymExpr const*, llvm::APSInt const&, llvm::APSInt const&) RangeConstraintManager.cpp:0:0
#11 0x00000000049d368c clang::ento::RangedConstraintManager::assumeSymUnsupported(llvm::IntrusiveRefCntPtr<clang::ento::ProgramState const>, clang::ento::SymExpr const*, bool) (../../main-github/llvm/build-all/bin/clang+0x49d368c)
#12 0x00000000049f0b09 clang::ento::SimpleConstraintManager::assumeAux(llvm::IntrusiveRefCntPtr<clang::ento::ProgramState const>, clang::ento::NonLoc, bool) (../../main-github/llvm/build-all/bin/clang+0x49f0b09)
#13 0x00000000049f096a clang::ento::SimpleConstraintManager::assume(llvm::IntrusiveRefCntPtr<clang::ento::ProgramState const>, clang::ento::NonLoc, bool) (../../main-github/llvm/build-all/bin/clang+0x49f096a)
#14 0x00000000049f086d clang::ento::SimpleConstraintManager::assumeInternal(llvm::IntrusiveRefCntPtr<clang::ento::ProgramState const>, clang::ento::DefinedSVal, bool) (../../main-github/llvm/build-all/bin/clang+0x49f086d)
#15 0x000000000492d3e3 clang::ento::ConstraintManager::assumeDual(llvm::IntrusiveRefCntPtr<clang::ento::ProgramState const>, clang::ento::DefinedSVal) (../../main-github/llvm/build-all/bin/clang+0x492d3e3)
#16 0x0000000004955b6d clang::ento::ExprEngine::evalEagerlyAssumeBinOpBifurcation(clang::ento::ExplodedNodeSet&, clang::ento::ExplodedNodeSet&, clang::Expr const*) (../../main-github/llvm/build-all/bin/clang+0x4955b6d)
#17 0x00000000049514b6 clang::ento::ExprEngine::Visit(clang::Stmt const*, clang::ento::ExplodedNode*, clang::ento::ExplodedNodeSet&) (../../main-github/llvm/build-all/bin/clang+0x49514b6)
#18 0x000000000494c73e clang::ento::ExprEngine::ProcessStmt(clang::Stmt const*, clang::ento::ExplodedNode*) (../../main-github/llvm/build-all/bin/clang+0x494c73e)
#19 0x000000000494c459 clang::ento::ExprEngine::processCFGElement(clang::CFGElement, clang::ento::ExplodedNode*, unsigned int, clang::ento::NodeBuilderContext*) (../../main-github/llvm/build-all/bin/clang+0x494c459)
#20 0x000000000492f3d0 clang::ento::CoreEngine::HandlePostStmt(clang::CFGBlock const*, unsigned int, clang::ento::ExplodedNode*) (../../main-github/llvm/build-all/bin/clang+0x492f3d0)
#21 0x000000000492e1f6 clang::ento::CoreEngine::ExecuteWorkList(clang::LocationContext const*, unsigned int, llvm::IntrusiveRefCntPtr<clang::ento::ProgramState const>) (../../main-github/llvm/build-all/bin/clang+0x492e1f6)
```

Differential Revision: https://reviews.llvm.org/D112621
pull bot pushed a commit that referenced this pull request Mar 28, 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 #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 #18: libclang_rt.tsan_osx_dynamic.dylib`__sanitizer::LibIgnore::OnLibraryLoaded(this=0x0000000101f3aa40, name="<some library>") at sanitizer_libignore.cpp:54:11
  frame #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
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