Artem-B wrote:
This is breaking CUDA/NVPTX.
Enabling PGO results in compiler generating PGO-related data which references
itself, and NVPTX can't compile those.
E.g. we see data like this which includes a reference to itself:
```
@__profd__ZN12cuda_helpers13memcmp_kernelEPjS0_mPb = protected global { i64,
i64, i64, i64, ptr, ptr, i32, [3 x i16], i32 } { i64 322482019142718985, i64
287486624882456055, i64 sub (i64 ptrtoint (ptr
@__profc__ZN12cuda_helpers13memcmp_kernelEPjS0_mPb to i64), i64 ptr
toint (ptr @__profd__ZN12cuda_helpers13memcmp_kernelEPjS0_mPb to i64)), i64 0,
ptr @_ZN12cuda_helpers13memcmp_kernelEPjS0_mPb, ptr null, i32 5, [3 x i16]
zeroinitializer, i32 0 }, section "__llvm_prf_data",
comdat($__profc__ZN12cuda_helpers13memcmp_kernelEPjS0_mPb), a
lign 8
```
When LLVM sees such self-reference, it crashes. https://godbolt.org/z/o6PTqr1ca
```
LLVM ERROR: Circular dependency found in global variable set
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and
include the crash backtrace.
Stack dump:
0. Program arguments: /opt/compiler-explorer/clang-trunk/bin/llc -o
/app/output.s -x86-asm-syntax=intel -march=nvptx64 -mcpu=sm_20 <source>
#0 0x0000000003ab1a88 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int)
(/opt/compiler-explorer/clang-trunk/bin/llc+0x3ab1a88)
#1 0x0000000003aaf644 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
#2 0x00007a9fa6c42520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
#3 0x00007a9fa6c969fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
#4 0x00007a9fa6c42476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
#5 0x00007a9fa6c287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
#6 0x000000000077d6a2 llvm::UniqueStringSaver::save(llvm::Twine const&)
(.cold) StringSaver.cpp:0:0
#7 0x0000000003a079d8 (/opt/compiler-explorer/clang-trunk/bin/llc+0x3a079d8)
#8 0x00000000017dc57e (/opt/compiler-explorer/clang-trunk/bin/llc+0x17dc57e)
#9 0x00000000017dc3dd VisitGlobalVariableForEmission(llvm::GlobalVariable
const*, llvm::SmallVectorImpl<llvm::GlobalVariable const*>&,
llvm::DenseSet<llvm::GlobalVariable const*,
llvm::DenseMapInfo<llvm::GlobalVariable const*, void>>&,
llvm::DenseSet<llvm::GlobalVariable const*,
llvm::DenseMapInfo<llvm::GlobalVariable const*, void>>&) NVPTXAsmPrinter.cpp:0:0
#10 0x00000000017dc6dc llvm::NVPTXAsmPrinter::emitGlobals(llvm::Module const&)
(/opt/compiler-explorer/clang-trunk/bin/llc+0x17dc6dc)
#11 0x00000000017dcf7d llvm::NVPTXAsmPrinter::doFinalization(llvm::Module&)
(/opt/compiler-explorer/clang-trunk/bin/llc+0x17dcf7d)
#12 0x00000000030a916d llvm::FPPassManager::doFinalization(llvm::Module&)
(/opt/compiler-explorer/clang-trunk/bin/llc+0x30a916d)
#13 0x00000000030b48f0 llvm::legacy::PassManagerImpl::run(llvm::Module&)
(/opt/compiler-explorer/clang-trunk/bin/llc+0x30b48f0)
#14 0x00000000008b4a08 compileModule(char**, llvm::LLVMContext&) llc.cpp:0:0
#15 0x000000000079237e main
(/opt/compiler-explorer/clang-trunk/bin/llc+0x79237e)
#16 0x00007a9fa6c29d90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#17 0x00007a9fa6c29e40 __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#18 0x00000000008ac9c5 _start
(/opt/compiler-explorer/clang-trunk/bin/llc+0x8ac9c5)
Program terminated with signal: SIGSEGV
Compiler returned: 139
```
https://github.com/llvm/llvm-project/pull/94268
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