[CIR][CIRGen] Change SignBitOp result type to !cir.bool

[PikachuHyA]

No description provided.

[PikachuHyA]

When I added support for __builtin_signbit, I found that returning !cir.bool from SignBitOp caused a crash during the lowering process to LLVM IR. This issue occurred because a builtin.unrealized_conversion_cast appeared during lowering and could not be eliminated. However, when I changed the return value of SignBitOp to !s32i, the lowering to LLVM IR proceeded without any issues.

error with return !cir.bool

$./bin/clang -fclangir -c ../clang/test/CIR/CodeGen/builtin-signbit.c -Xclang -emit-llvm -o t.ll
loc(fused["../clang/test/CIR/CodeGen/builtin-signbit.c":13:33, "../clang/test/CIR/CodeGen/builtin-signbit.c":13:34]): error: LLVM Translation failed for operation: builtin.unrealized_conversion_cast
fatal error: error in backend: Lowering from LLVMIR dialect to llvm IR failed!
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: ./bin/clang -fclangir -c ../clang/test/CIR/CodeGen/builtin-signbit.c -Xclang -emit-llvm -o t.ll
1.      <eof> parser at end of file
 #0 0x00000000020911e8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (./bin/clang+0x20911e8)
 #1 0x000000000208ecde llvm::sys::RunSignalHandlers() (./bin/clang+0x208ecde)
 #2 0x0000000002090579 llvm::sys::CleanupOnSignal(unsigned long) (./bin/clang+0x2090579)
 #3 0x00000000020092d7 (anonymous namespace)::CrashRecoveryContextImpl::HandleCrash(int, unsigned long) CrashRecoveryContext.cpp:0:0
 #4 0x000000000200926f llvm::CrashRecoveryContext::HandleExit(int) (./bin/clang+0x200926f)
 #5 0x000000000208b2f7 llvm::sys::Process::Exit(int, bool) (./bin/clang+0x208b2f7)
 #6 0x0000000000eb7db6 (./bin/clang+0xeb7db6)
 #7 0x000000000200f7e6 llvm::report_fatal_error(llvm::Twine const&, bool) (./bin/clang+0x200f7e6)
 #8 0x000000000200f6c6 (./bin/clang+0x200f6c6)
 #9 0x000000000336f4b2 (./bin/clang+0x336f4b2)
#10 0x0000000003345b12 cir::CIRGenConsumer::HandleTranslationUnit(clang::ASTContext&) (./bin/clang+0x3345b12)
#11 0x0000000005521379 clang::ParseAST(clang::Sema&, bool, bool) (./bin/clang+0x5521379)
#12 0x0000000002b05cbf clang::FrontendAction::Execute() (./bin/clang+0x2b05cbf)
#13 0x0000000002a7659d clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (./bin/clang+0x2a7659d)
#14 0x0000000002beb9de clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (./bin/clang+0x2beb9de)
#15 0x0000000000eb78e8 cc1_main(llvm::ArrayRef<char const*>, char const*, void*) (./bin/clang+0xeb78e8)
#16 0x0000000000eb3e3e ExecuteCC1Tool(llvm::SmallVectorImpl<char const*>&, llvm::ToolContext const&) driver.cpp:0:0
#17 0x00000000028c8379 void llvm::function_ref<void ()>::callback_fn<clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const::$_0>(long) Job.cpp:0:0
#18 0x0000000002009206 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref<void ()>) (./bin/clang+0x2009206)
#19 0x00000000028c7a42 clang::driver::CC1Command::Execute(llvm::ArrayRef<std::optional<llvm::StringRef>>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>*, bool*) const (./bin/clang+0x28c7a42)
#20 0x0000000002886cec clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (./bin/clang+0x2886cec)
#21 0x0000000002886ff7 clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&, bool) const (./bin/clang+0x2886ff7)
#22 0x00000000028a4408 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl<std::pair<int, clang::driver::Command const*>>&) (./bin/clang+0x28a4408)
#23 0x0000000000eb345c clang_main(int, char**, llvm::ToolContext const&) (./bin/clang+0xeb345c)
#24 0x0000000000ec2eb7 main (./bin/clang+0xec2eb7)
#25 0x00007f04f4bff192 __libc_start_main (/lib64/libc.so.6+0x28192)
#26 0x0000000000eb1a3e _start (./bin/clang+0xeb1a3e)

[PikachuHyA]

I think the error is related to #480

[Lancern]

It crashes because the result type of the zext instruction generated by the lowering of cir.signbit does not match what !cir.bool lowers to:

clangir/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp

Lines 3834 to 3836 in 888f00c

	auto converted = rewriter.create<mlir::LLVM::ZExtOp>(
	op.getLoc(), mlir::IntegerType::get(rewriter.getContext(), 32),
	cmpResult);

You could update it to:

auto converted = rewriter.create<mlir::LLVM::ZExtOp>(
    op.getLoc(), getTypeConverter()->convertType(op.getType()),
    cmpResult);

And it should be OK then.

[PikachuHyA]

Thank you very much, @orbiri and @Lancern .

The SignBitOp now returns a boolean value.

@bcardosolopes Please review this patch.

[bcardosolopes]

LGTM