Specifically, `X & M ?= C --> (C << clz(M)) ?= (X << clz(M))` where M is
a non-empty sequence of ones starting at the least significant bit with
the remainder zero and C is a constant subset of M that cannot be
materialised into a SUBS (immediate). Proof:
https://alive2.llvm.org/ce/z/haqdJ4.

This improves the comparison in isinf, for example:
```cpp
int isinf(float x) {
  return __builtin_isinf(x);
}
```

Before:
```
isinf:
  fmov    w9, s0
  mov     w8, #2139095040
  and     w9, w9, #0x7fffffff
  cmp     w9, w8
  cset    w0, eq
  ret
```

After:
```
isinf:
  fmov    w9, s0
  mov     w8, #-16777216
  cmp     w8, w9, lsl #1
  cset    w0, eq
  ret
```

A recent change adding a new sanitizer kind (via Sanitizers.def) was
reverted in c74fa20 ("Revert "[Clang][CodeGen] Introduce the
AllocToken SanitizerKind" (llvm#162413)"). The reason was this ASan report,
when running the test cases in
clang/test/Preprocessor/print-header-json.c:

```
==clang==483265==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7d82b97e8b58 at pc 0x562cd432231f bp 0x7fff3fad0850 sp 0x7fff3fad0848
READ of size 16 at 0x7d82b97e8b58 thread T0
    #0 0x562cd432231e in __copy_non_overlapping_range<const unsigned long *, const unsigned long *> zorg-test/libcxx_install_asan_ubsan/include/c++/v1/string:2144:38
    #1 0x562cd432231e in void std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>::__init_with_size[abi:nn220000]<unsigned long const*, unsigned long const*>(unsigned long const*, unsigned long const*, unsigned long) zorg-test/libcxx_install_asan_ubsan/include/c++/v1/string:2685:18
    llvm#2 0x562cd41e2797 in __init<const unsigned long *, 0> zorg-test/libcxx_install_asan_ubsan/include/c++/v1/string:2673:3
    llvm#3 0x562cd41e2797 in basic_string<const unsigned long *, 0> zorg-test/libcxx_install_asan_ubsan/include/c++/v1/string:1174:5
    llvm#4 0x562cd41e2797 in clang::ASTReader::ReadString(llvm::SmallVectorImpl<unsigned long> const&, unsigned int&) clang/lib/Serialization/ASTReader.cpp:10171:15
    llvm#5 0x562cd41fd89a in clang::ASTReader::ParseLanguageOptions(llvm::SmallVector<unsigned long, 64u> const&, llvm::StringRef, bool, clang::ASTReaderListener&, bool) clang/lib/Serialization/ASTReader.cpp:6475:28
    llvm#6 0x562cd41eea53 in clang::ASTReader::ReadOptionsBlock(llvm::BitstreamCursor&, llvm::StringRef, unsigned int, bool, clang::ASTReaderListener&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>&) clang/lib/Serialization/ASTReader.cpp:3069:11
    llvm#7 0x562cd4204ab8 in clang::ASTReader::ReadControlBlock(clang::serialization::ModuleFile&, llvm::SmallVectorImpl<clang::ASTReader::ImportedModule>&, clang::serialization::ModuleFile const*, unsigned int) clang/lib/Serialization/ASTReader.cpp:3249:15
    llvm#8 0x562cd42097d2 in clang::ASTReader::ReadASTCore(llvm::StringRef, clang::serialization::ModuleKind, clang::SourceLocation, clang::serialization::ModuleFile*, llvm::SmallVectorImpl<clang::ASTReader::ImportedModule>&, long, long, clang::ASTFileSignature, unsigned int) clang/lib/Serialization/ASTReader.cpp:5182:15
    llvm#9 0x562cd421ec77 in clang::ASTReader::ReadAST(llvm::StringRef, clang::serialization::ModuleKind, clang::SourceLocation, unsigned int, clang::serialization::ModuleFile**) clang/lib/Serialization/ASTReader.cpp:4828:11
    llvm#10 0x562cd3d07b74 in clang::CompilerInstance::findOrCompileModuleAndReadAST(llvm::StringRef, clang::SourceLocation, clang::SourceLocation, bool) clang/lib/Frontend/CompilerInstance.cpp:1805:27
    llvm#11 0x562cd3d0b2ef in clang::CompilerInstance::loadModule(clang::SourceLocation, llvm::ArrayRef<clang::IdentifierLoc>, clang::Module::NameVisibilityKind, bool) clang/lib/Frontend/CompilerInstance.cpp:1956:31
    llvm#12 0x562cdb04eb1c in clang::Preprocessor::HandleHeaderIncludeOrImport(clang::SourceLocation, clang::Token&, clang::Token&, clang::SourceLocation, clang::detail::SearchDirIteratorImpl<true>, clang::FileEntry const*) clang/lib/Lex/PPDirectives.cpp:2423:49
    llvm#13 0x562cdb042222 in clang::Preprocessor::HandleIncludeDirective(clang::SourceLocation, clang::Token&, clang::detail::SearchDirIteratorImpl<true>, clang::FileEntry const*) clang/lib/Lex/PPDirectives.cpp:2101:17
    llvm#14 0x562cdb043366 in clang::Preprocessor::HandleDirective(clang::Token&) clang/lib/Lex/PPDirectives.cpp:1338:14
    llvm#15 0x562cdafa84bc in clang::Lexer::LexTokenInternal(clang::Token&, bool) clang/lib/Lex/Lexer.cpp:4512:7
    llvm#16 0x562cdaf9f20b in clang::Lexer::Lex(clang::Token&) clang/lib/Lex/Lexer.cpp:3729:24
    llvm#17 0x562cdb0d4ffa in clang::Preprocessor::Lex(clang::Token&) clang/lib/Lex/Preprocessor.cpp:896:11
    llvm#18 0x562cd77da950 in clang::ParseAST(clang::Sema&, bool, bool) clang/lib/Parse/ParseAST.cpp:163:7
    [...]

0x7d82b97e8b58 is located 0 bytes after 3288-byte region [0x7d82b97e7e80,0x7d82b97e8b58)
allocated by thread T0 here:
    #0 0x562cca76f604 in malloc zorg-test/llvm-project/compiler-rt/lib/asan/asan_malloc_linux.cpp:67:3
    #1 0x562cd1cce452 in safe_malloc llvm/include/llvm/Support/MemAlloc.h:26:18
    llvm#2 0x562cd1cce452 in llvm::SmallVectorBase<unsigned int>::grow_pod(void*, unsigned long, unsigned long) llvm/lib/Support/SmallVector.cpp:151:15
    llvm#3 0x562cdbe1768b in grow_pod llvm/include/llvm/ADT/SmallVector.h:139:11
    llvm#4 0x562cdbe1768b in grow llvm/include/llvm/ADT/SmallVector.h:525:41
    llvm#5 0x562cdbe1768b in reserve llvm/include/llvm/ADT/SmallVector.h:665:13
    llvm#6 0x562cdbe1768b in llvm::BitstreamCursor::readRecord(unsigned int, llvm::SmallVectorImpl<unsigned long>&, llvm::StringRef*) llvm/lib/Bitstream/Reader/BitstreamReader.cpp:230:10
    llvm#7 0x562cd41ee8ab in clang::ASTReader::ReadOptionsBlock(llvm::BitstreamCursor&, llvm::StringRef, unsigned int, bool, clang::ASTReaderListener&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>&) clang/lib/Serialization/ASTReader.cpp:3060:49
    llvm#8 0x562cd4204ab8 in clang::ASTReader::ReadControlBlock(clang::serialization::ModuleFile&, llvm::SmallVectorImpl<clang::ASTReader::ImportedModule>&, clang::serialization::ModuleFile const*, unsigned int) clang/lib/Serialization/ASTReader.cpp:3249:15
    llvm#9 0x562cd42097d2 in clang::ASTReader::ReadASTCore(llvm::StringRef, clang::serialization::ModuleKind, clang::SourceLocation, clang::serialization::ModuleFile*, llvm::SmallVectorImpl<clang::ASTReader::ImportedModule>&, long, long, clang::ASTFileSignature, unsigned int) clang/lib/Serialization/ASTReader.cpp:5182:15
    llvm#10 0x562cd421ec77 in clang::ASTReader::ReadAST(llvm::StringRef, clang::serialization::ModuleKind, clang::SourceLocation, unsigned int, clang::serialization::ModuleFile**) clang/lib/Serialization/ASTReader.cpp:4828:11
    llvm#11 0x562cd3d07b74 in clang::CompilerInstance::findOrCompileModuleAndReadAST(llvm::StringRef, clang::SourceLocation, clang::SourceLocation, bool) clang/lib/Frontend/CompilerInstance.cpp:1805:27
    llvm#12 0x562cd3d0b2ef in clang::CompilerInstance::loadModule(clang::SourceLocation, llvm::ArrayRef<clang::IdentifierLoc>, clang::Module::NameVisibilityKind, bool) clang/lib/Frontend/CompilerInstance.cpp:1956:31
    llvm#13 0x562cdb04eb1c in clang::Preprocessor::HandleHeaderIncludeOrImport(clang::SourceLocation, clang::Token&, clang::Token&, clang::SourceLocation, clang::detail::SearchDirIteratorImpl<true>, clang::FileEntry const*) clang/lib/Lex/PPDirectives.cpp:2423:49
    llvm#14 0x562cdb042222 in clang::Preprocessor::HandleIncludeDirective(clang::SourceLocation, clang::Token&, clang::detail::SearchDirIteratorImpl<true>, clang::FileEntry const*) clang/lib/Lex/PPDirectives.cpp:2101:17
    llvm#15 0x562cdb043366 in clang::Preprocessor::HandleDirective(clang::Token&) clang/lib/Lex/PPDirectives.cpp:1338:14
    llvm#16 0x562cdafa84bc in clang::Lexer::LexTokenInternal(clang::Token&, bool) clang/lib/Lex/Lexer.cpp:4512:7
    llvm#17 0x562cdaf9f20b in clang::Lexer::Lex(clang::Token&) clang/lib/Lex/Lexer.cpp:3729:24
    llvm#18 0x562cdb0d4ffa in clang::Preprocessor::Lex(clang::Token&) clang/lib/Lex/Preprocessor.cpp:896:11
    llvm#19 0x562cd77da950 in clang::ParseAST(clang::Sema&, bool, bool) clang/lib/Parse/ParseAST.cpp:163:7
    [...]

SUMMARY: AddressSanitizer: heap-buffer-overflow clang/lib/Serialization/ASTReader.cpp:10171:15 in clang::ASTReader::ReadString(llvm::SmallVectorImpl<unsigned long> const&, unsigned int&)
```

The reason is this particular RUN line:
```
// RUN: env CC_PRINT_HEADERS_FORMAT=json CC_PRINT_HEADERS_FILTERING=direct-per-file CC_PRINT_HEADERS_FILE=%t.txt %clang -fsyntax-only -I %S/Inputs/print-header-json -isystem %S/Inputs/print-header-json/system -fmodules -fimplicit-module-maps -fmodules-cache-path=%t %s -o /dev/null
```

which was added in 8df194f ("[Clang] Support includes translated to
module imports in -header-include-filtering=direct-per-file (llvm#156756)").

The problem is caused by an incremental build reusing stale cached
module files (.pcm) that are no longer binary-compatible with the
updated compiler. Adding a new sanitizer option altered the implicit
binary layout of the serialized LangOptions data structure. The build +
test system is oblivious to such changes. When the new compiler
attempted to read the old module file (from the previous test
invocation), it misinterpreted the data due to the layout mismatch,
resulting in a heap-buffer-overflow. Unfortunately Clang's PCM format
does not encode nor detect version mismatches here; a more graceful
failure mode would be preferable.

For now, fix the test to be more robust with incremental build + test.

Otherwise debug-info is stripped, which influences the language of the
current frame.

Also, set explicit breakpoint because Windows seems to not obey the
debugtrap.

Log from failing test on Windows:
```
(lldb) command source -s 0 'lit-lldb-init-quiet'
Executing commands in 'D:\test\lit-lldb-init-quiet'.
(lldb) command source -C --silent-run true lit-lldb-init
(lldb) target create "main.out"
Current executable set to 'D:\test\main.out' (x86_64).
(lldb) settings set interpreter.stop-command-source-on-error false
(lldb) command source -s 0 'with-target.input'
Executing commands in 'D:\test\with-target.input'.
(lldb) expr blah
            ^
            error: use of undeclared identifier 'blah'
note: Falling back to default language. Ran expression as 'Objective C++'.
(lldb) run
Process 29404 launched: 'D:\test\main.out' (x86_64)
Process 29404 stopped
* thread #1, stop reason = Exception 0x80000003 encountered at address 0x7ff7b3df7189
    frame #0: 0x00007ff7b3df718a main.out
->  0x7ff7b3df718a: xorl   %eax, %eax
    0x7ff7b3df718c: popq   %rcx
    0x7ff7b3df718d: retq
    0x7ff7b3df718e: int3
(lldb) expr blah
            ^
            error: use of undeclared identifier 'blah'
note: Falling back to default language. Ran expression as 'Objective C++'.
(lldb) expr -l objc -- blah
                       ^
                       error: use of undeclared identifier 'blah'
note: Expression evaluation in pure Objective-C not supported. Ran expression as 'Objective C++'.
(lldb) expr -l c -- blah
                    ^
                    error: use of undeclared identifier 'blah'
note: Expression evaluation in pure C not supported. Ran expression as 'ISO C++'.
```

The Tkinter module was renamed to tkinter in Python 3.0.

https://docs.python.org/2/library/tkinter.html
https://docs.python.org/3/library/tkinter.html

Rest of it appears to work when imported inside of LLDB:
```
$ ./bin/lldb /tmp/test.o
(lldb) target create "/tmp/test.o"
Current executable set to '/tmp/test.o' (x86_64).
(lldb) b main
Breakpoint 1: where = test.o`main + 8 at test.c:1:18, address = 0x0000000000001131
(lldb) run
Process 121572 launched: '/tmp/test.o' (x86_64)
Process 121572 stopped
* thread #1, name = 'test.o', stop reason = breakpoint 1.1
    frame #0: 0x0000555555555131 test.o`main at test.c:1:18
-> 1   	int main() { int a = 1; char b = '?'; return 0; }
(lldb) command script import <...>/llvm-project/lldb/examples/python/lldbtk.py
(lldb) tk-
Available completions:
        tk-process   -- For more information run 'help tk-process'
        tk-target    -- For more information run 'help tk-target'
        tk-variables -- For more information run 'help tk-variables'
(lldb) tk-process
(lldb) tk-target
(lldb) tk-variables
```

…ypes (llvm#162278)

When we take the following C program:
```
int main() {
  return 0;
}
```
and create a statically-linked executable from it:
```
clang -static -g -o main main.c
```
Then we can observe the following `lldb` behavior:
```
$ lldb
(lldb) target create main
Current executable set to '.../main' (x86_64).
(lldb) breakpoint set --name main
Breakpoint 1: where = main`main + 11 at main.c:2:3, address = 0x000000000022aa7b
(lldb) process launch
Process 3773637 launched: '/home/me/tmp/built-in/main' (x86_64)
Process 3773637 stopped
* thread #1, name = 'main', stop reason = breakpoint 1.1
    frame #0: 0x000000000022aa7b main`main at main.c:2:3
   1   	int main() {
-> 2   	  return 0;
   3   	}
(lldb) script lldb.debugger.GetSelectedTarget().FindFirstType("__int128").size
0
(lldb) script lldb.debugger.GetSelectedTarget().FindFirstType("unsigned __int128").size
0
(lldb) quit
```
The value return by the `SBTarget::FindFirstType` method is wrong for
the `__int128` and `unsigned __int128` basic types.

The proposed changes make the `TypeSystemClang::GetBasicTypeEnumeration`
method consistent with `gcc` and `clang` C [language
extension](https://gcc.gnu.org/onlinedocs/gcc/_005f_005fint128.html)
related to 128-bit integer types as well as with the
`BuiltinType::getName` method in the LLVM codebase itself.

When the above change is applied, the behavior of the `lldb` changes in
the following (desired) way:
```
$ lldb
(lldb) target create main
Current executable set to '.../main' (x86_64).
(lldb) breakpoint set --name main
Breakpoint 1: where = main`main + 11 at main.c:2:3, address = 0x000000000022aa7b
(lldb) process launch
Process 3773637 launched: '/home/me/tmp/built-in/main' (x86_64)
Process 3773637 stopped
* thread #1, name = 'main', stop reason = breakpoint 1.1
    frame #0: 0x000000000022aa7b main`main at main.c:2:3
   1   	int main() {
-> 2   	  return 0;
   3   	}
(lldb) script lldb.debugger.GetSelectedTarget().FindFirstType("__int128").size
16
(lldb) script lldb.debugger.GetSelectedTarget().FindFirstType("unsigned __int128").size
16
(lldb) quit
```

---------

Co-authored-by: Matej Košík <[email protected]>

**Mitigation for:** google/sanitizers#749

**Disclosure:** I'm not an ASan compiler expert yet (I'm trying to
learn!), I primarily work in the runtime. Some of this PR was developed
with the help of AI tools (primarily as a "fuzzy `grep` engine"), but
I've manually refined and tested the output, and can speak for every
line. In general, I used it only to orient myself and for
"rubberducking".

**Context:**

The msvc ASan team (👋 ) has received an internal request to improve
clang's exception handling under ASan for Windows. Namely, we're
interested in **mitigating** this bug:
google/sanitizers#749

To summarize, today, clang + ASan produces a false-positive error for
this program:

```C++
#include <cstdio>
#include <exception>
int main()
{
	try	{
		throw std::exception("test");
	}catch (const std::exception& ex){
		puts(ex.what());
	}
	return 0;
}
```

The error reads as such:


```
C:\Users\dajusto\source\repros\upstream>type main.cpp
#include <cstdio>
#include <exception>
int main()
{
        try     {
                throw std::exception("test");
        }catch (const std::exception& ex){
                puts(ex.what());
        }
        return 0;
}
C:\Users\dajusto\source\repros\upstream>"C:\Users\dajusto\source\repos\llvm-project\build.runtimes\bin\clang.exe" -fsanitize=address -g -O0 main.cpp

C:\Users\dajusto\source\repros\upstream>a.exe
=================================================================
==19112==ERROR: AddressSanitizer: access-violation on unknown address 0x000000000000 (pc 0x7ff72c7c11d9 bp 0x0080000ff960 sp 0x0080000fcf50 T0)
==19112==The signal is caused by a READ memory access.
==19112==Hint: address points to the zero page.
    #0 0x7ff72c7c11d8 in main C:\Users\dajusto\source\repros\upstream\main.cpp:8
    #1 0x7ff72c7d479f in _CallSettingFrame C:\repos\msvc\src\vctools\crt\vcruntime\src\eh\amd64\handlers.asm:49
    llvm#2 0x7ff72c7c8944 in __FrameHandler3::CxxCallCatchBlock(struct _EXCEPTION_RECORD *) C:\repos\msvc\src\vctools\crt\vcruntime\src\eh\frame.cpp:1567
    llvm#3 0x7ffb4a90e3e5  (C:\WINDOWS\SYSTEM32\ntdll.dll+0x18012e3e5)
    llvm#4 0x7ff72c7c1128 in main C:\Users\dajusto\source\repros\upstream\main.cpp:6
    llvm#5 0x7ff72c7c33db in invoke_main C:\repos\msvc\src\vctools\crt\vcstartup\src\startup\exe_common.inl:78
    llvm#6 0x7ff72c7c33db in __scrt_common_main_seh C:\repos\msvc\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288
    llvm#7 0x7ffb49b05c06  (C:\WINDOWS\System32\KERNEL32.DLL+0x180035c06)
    llvm#8 0x7ffb4a8455ef  (C:\WINDOWS\SYSTEM32\ntdll.dll+0x1800655ef)

==19112==Register values:
rax = 0  rbx = 80000ff8e0  rcx = 27d76d00000  rdx = 80000ff8e0
rdi = 80000fdd50  rsi = 80000ff6a0  rbp = 80000ff960  rsp = 80000fcf50
r8  = 100  r9  = 19930520  r10 = 8000503a90  r11 = 80000fd540
r12 = 80000fd020  r13 = 0  r14 = 80000fdeb8  r15 = 0
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: access-violation C:\Users\dajusto\source\repros\upstream\main.cpp:8 in main
==19112==ABORTING
```

The root of the issue _appears to be_ that ASan's instrumentation is
incompatible with Window's assumptions for instantiating `catch`-block's
parameters (`ex` in the snippet above).

The nitty gritty details are lost on me, but I understand that to make
this work without loss of ASan coverage, a "serious" refactoring is
needed. In the meantime, users risk false positive errors when pairing
ASan + catch-block parameters on Windows.

**To mitigate this** I think we should avoid instrumenting catch-block
parameters on Windows. It appears to me this is as "simple" as marking
catch block parameters as "uninteresting" in
`AddressSanitizer::isInterestingAlloca`. My manual tests seem to confirm
this.

I believe this is strictly better than today's status quo, where the
runtime generates false positives. Although we're now explicitly
choosing to instrument less, the benefit is that now more programs can
run with ASan without _funky_ macros that disable ASan on exception
blocks.

**This PR:** implements the mitigation above, and creates a simple new
test for it.

_Thanks!_

---------

Co-authored-by: Antonio Frighetto <[email protected]>

…nteger registers (llvm#163646)

Fix the `RegisterValue::SetValueFromData` method so that it works also
for 128-bit registers that contain integers.

Without this change, the `RegisterValue::SetValueFromData` method does
not work correctly
for 128-bit registers that contain (signed or unsigned) integers.

---

Steps to reproduce the problem:

(1)

Create a program that writes a 128-bit number to a 128-bit registers
`xmm0`. E.g.:
```
#include <stdint.h>

int main() {
  __asm__ volatile (
      "pinsrq $0, %[lo], %%xmm0\n\t"  // insert low 64 bits
      "pinsrq $1, %[hi], %%xmm0"    // insert high 64 bits
      :
      : [lo]"r"(0x7766554433221100),
        [hi]"r"(0xffeeddccbbaa9988)
  );
  return 0;
}
```

(2)

Compile this program with LLVM compiler:
```
$ $YOUR/clang -g -o main main.c
```

(3)

Modify LLDB so that when it will be reading value from the `xmm0`
register, instead of assuming that it is vector register, it will treat
it as if it contain an integer. This can be achieved e.g. this way:
```
diff --git a/lldb/source/Utility/RegisterValue.cpp b/lldb/source/Utility/RegisterValue.cpp
index 0e99451..a4b51db3e56d 100644
--- a/lldb/source/Utility/RegisterValue.cpp
+++ b/lldb/source/Utility/RegisterValue.cpp
@@ -188,6 +188,7 @@ Status RegisterValue::SetValueFromData(const RegisterInfo &reg_info,
     break;
   case eEncodingUint:
   case eEncodingSint:
+  case eEncodingVector:
     if (reg_info.byte_size == 1)
       SetUInt8(src.GetMaxU32(&src_offset, src_len));
     else if (reg_info.byte_size <= 2)
@@ -217,23 +218,6 @@ Status RegisterValue::SetValueFromData(const RegisterInfo &reg_info,
     else if (reg_info.byte_size == sizeof(long double))
       SetLongDouble(src.GetLongDouble(&src_offset));
     break;
-  case eEncodingVector: {
-    m_type = eTypeBytes;
-    assert(reg_info.byte_size <= kMaxRegisterByteSize);
-    buffer.bytes.resize(reg_info.byte_size);
-    buffer.byte_order = src.GetByteOrder();
-    if (src.CopyByteOrderedData(
-            src_offset,          // offset within "src" to start extracting data
-            src_len,             // src length
-            buffer.bytes.data(), // dst buffer
-            buffer.bytes.size(), // dst length
-            buffer.byte_order) == 0) // dst byte order
-    {
-      error = Status::FromErrorStringWithFormat(
-          "failed to copy data for register write of %s", reg_info.name);
-      return error;
-    }
-  }
   }
 
   if (m_type == eTypeInvalid)
```

(4)

Rebuild the LLDB.

(5)

Observe what happens how LLDB will print the content of this register
after it was initialized with 128-bit value.
```
$YOUR/lldb --source ./main
(lldb) target create main
Current executable set to '.../main' (x86_64).
(lldb) breakpoint set --file main.c --line 11
Breakpoint 1: where = main`main + 45 at main.c:11:3, address = 0x000000000000164d
(lldb) settings set stop-line-count-before 20
(lldb) process launch
Process 2568735 launched: '.../main' (x86_64)
Process 2568735 stopped
* thread #1, name = 'main', stop reason = breakpoint 1.1
    frame #0: 0x000055555555564d main`main at main.c:11:3
   1   	#include <stdint.h>
   2   	
   3   	int main() {
   4   	  __asm__ volatile (
   5   	      "pinsrq $0, %[lo], %%xmm0\n\t"  // insert low 64 bits
   6   	      "pinsrq $1, %[hi], %%xmm0"    // insert high 64 bits
   7   	      :
   8   	      : [lo]"r"(0x7766554433221100),
   9   	        [hi]"r"(0xffeeddccbbaa9988)
   10  	  );
-> 11  	  return 0;
   12  	}
(lldb) register read --format hex xmm0
    xmm0 = 0x7766554433221100ffeeddccbbaa9988
```

You can see that the upper and lower 64-bit wide halves are swapped.

---------

Co-authored-by: Matej Košík <[email protected]>

…lvm#162993)

Early if conversion can create instruction sequences such as
```
mov  x1, #1
csel x0, x1, x2, eq
```
which could be simplified into the following instead
```
csinc x0, x2, xzr, ne
```

One notable example that generates code like this is `cmpxchg weak`.

This is fixed by handling an immediate value of 1 as `add(wzr, 1)` so
that the addition can be folded into CSEL by using CSINC instead.

In `Driver.cpp` `std::atomic<uint64_t>` is used which may need
libatomic.

Build failure (if that is of interest):
```
[127/135] Linking CXX shared library lib/liblldMachO.so.20.1
ninja: job failed: : && /usr/lib/ccache/bin/clang++-20 -fPIC -Os -fstack-clash-protection -Wformat -Werror=format-security -D_GLIBCXX_ASSERTIONS=1 -D_LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS=1 -D_LIBCPP_ENABLE_HARDENED_MODE=1 -g -O2 -DNDEBUG -g1 -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections  -Wl,--as-needed,-O1,--sort-common -Wl,-z,defs -Wl,-z,nodelete   -Wl,-rpath-link,/home/user/aports/main/lld20/src/lld-20.1.5.src/build/./lib  -Wl,--gc-sections -shared -Wl,-soname,liblldMachO.so.20.1 -o lib/liblldMachO.so.20.1 MachO/CMakeFiles/lldMachO.dir/Arch/ARM64.cpp.o MachO/CMakeFiles/lldMachO.dir/Arch/ARM64Common.cpp.o MachO/CMakeFiles/lldMachO.dir/Arch/ARM64_32.cpp.o MachO/CMakeFiles/lldMachO.dir/Arch/X86_64.cpp.o MachO/CMakeFiles/lldMachO.dir/ConcatOutputSection.cpp.o MachO/CMakeFiles/lldMachO.dir/Driver.cpp.o MachO/CMakeFiles/lldMachO.dir/DriverUtils.cpp.o MachO/CMakeFiles/lldMachO.dir/Dwarf.cpp.o MachO/CMakeFiles/lldMachO.dir/EhFrame.cpp.o MachO/CMakeFiles/lldMachO.dir/ExportTrie.cpp.o MachO/CMakeFiles/lldMachO.dir/ICF.cpp.o MachO/CMakeFiles/lldMachO.dir/InputFiles.cpp.o MachO/CMakeFiles/lldMachO.dir/InputSection.cpp.o MachO/CMakeFiles/lldMachO.dir/LTO.cpp.o MachO/CMakeFiles/lldMachO.dir/MapFile.cpp.o MachO/CMakeFiles/lldMachO.dir/MarkLive.cpp.o MachO/CMakeFiles/lldMachO.dir/ObjC.cpp.o MachO/CMakeFiles/lldMachO.dir/OutputSection.cpp.o MachO/CMakeFiles/lldMachO.dir/OutputSegment.cpp.o MachO/CMakeFiles/lldMachO.dir/Relocations.cpp.o MachO/CMakeFiles/lldMachO.dir/BPSectionOrderer.cpp.o MachO/CMakeFiles/lldMachO.dir/SectionPriorities.cpp.o MachO/CMakeFiles/lldMachO.dir/Sections.cpp.o MachO/CMakeFiles/lldMachO.dir/SymbolTable.cpp.o MachO/CMakeFiles/lldMachO.dir/Symbols.cpp.o MachO/CMakeFiles/lldMachO.dir/SyntheticSections.cpp.o MachO/CMakeFiles/lldMachO.dir/Target.cpp.o MachO/CMakeFiles/lldMachO.dir/UnwindInfoSection.cpp.o MachO/CMakeFiles/lldMachO.dir/Writer.cpp.o -L/usr/lib/llvm20/lib -Wl,-rpath,"\$ORIGIN/../lib:/usr/lib/llvm20/lib:/home/user/aports/main/lld20/src/lld-20.1.5.src/build/lib:"  lib/liblldCommon.so.20.1  /usr/lib/llvm20/lib/libLLVM.so.20.1 && :
/usr/lib/gcc/powerpc-alpine-linux-musl/14.3.0/../../../../powerpc-alpine-linux-musl/bin/ld: MachO/CMakeFiles/lldMachO.dir/Driver.cpp.o: in function `handleExplicitExports()':
/usr/lib/gcc/powerpc-alpine-linux-musl/14.3.0/../../../../include/c++/14.3.0/bits/atomic_base.h:501:(.text._ZL21handleExplicitExportsv+0xb8): undefined reference to `__atomic_load_8'
/usr/lib/gcc/powerpc-alpine-linux-musl/14.3.0/../../../../powerpc-alpine-linux-musl/bin/ld: /usr/lib/gcc/powerpc-alpine-linux-musl/14.3.0/../../../../include/c++/14.3.0/bits/atomic_base.h:501:(.text._ZL21handleExplicitExportsv+0x180): undefined reference to `__atomic_load_8'
/usr/lib/gcc/powerpc-alpine-linux-musl/14.3.0/../../../../powerpc-alpine-linux-musl/bin/ld: MachO/CMakeFiles/lldMachO.dir/Driver.cpp.o: in function `void llvm::function_ref<void (unsigned int)>::callback_fn<llvm::parallelForEach<lld::macho::Symbol* const*, handleExplicitExports()::$_0>(lld::macho::Symbol* const*, lld::macho::Symbol* const*, handleExplicitExports()::$_0)::{lambda(unsigned int)#1}>(int, unsigned int)':
/usr/lib/gcc/powerpc-alpine-linux-musl/14.3.0/../../../../include/c++/14.3.0/bits/atomic_base.h:631:(.text._ZN4llvm12function_refIFvjEE11callback_fnIZNS_15parallelForEachIPKPN3lld5macho6SymbolEZL21handleExplicitExportsvE3$_0EEvT_SC_T0_EUljE_EEvij+0xd4): undefined reference to `__atomic_fetch_add_8'
clang++-20: error: linker command failed with exit code 1 (use -v to see invocation)
```

CC @int3 @gkmhub @smeenai

Similar to
llvm@f0b451c

llvm#164955 has a use-after-scope
(https://lab.llvm.org/buildbot/#/builders/169/builds/16454):

```
==mlir-opt==3940651==ERROR: AddressSanitizer: stack-use-after-scope on address 0x6e1f6ba5c878 at pc 0x6336b214912a bp 0x7ffe607f1670 sp 0x7ffe607f1668
READ of size 4 at 0x6e1f6ba5c878 thread T0
    #0 0x6336b2149129 in size /home/b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/include/llvm/ADT/SmallVector.h:80:32
    #1 0x6336b2149129 in operator[] /home/b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/include/llvm/ADT/SmallVector.h:299:5
    llvm#2 0x6336b2149129 in populateBoundsForShapedValueDim /home/b/sanitizer-x86_64-linux-fast/build/llvm-project/mlir/lib/Dialect/MemRef/IR/ValueBoundsOpInterfaceImpl.cpp:113:43
...
```

This patch attempts to fix-forward by stack-allocating reassocIndices,
instead of taking a reference to a return value.