Tracking Issue for core compilation to C

[zlfn]

I tried core compilation with llvm-cbe, but the following problem occurs.

Missing intrinsics

• freeze
  Add support for the freeze instruction JuliaHubOSS/llvm-cbe#175
• llvm.fshl.i64
  Code generator does not support intrinsic function llvm.fshl.i32 JuliaHubOSS/llvm-cbe#111
• is.class.fpclass
  Code generator does not support intrinsic function 'llvm.is.fpclass.f32' JuliaHubOSS/llvm-cbe#195
  Support LLVM-19 JuliaHubOSS/llvm-cbe#211
  Originally, when no_fp_fmt_parse cfg is used, the instruction associated with the floating point should not be appeared, but something seems to be wrong in rust version nightly-2024-02-13.
  Resolved with rust nightly with LLVM-19
• llvm.uadd.sat.i32, llvm.usub.sat.i16
  Add support for the Saturation Arithmetic Intrinsics (llvm.uadd.sat.* and others) JuliaHubOSS/llvm-cbe#207
  Implement llvm.*.sat.* intrinsics JuliaHubOSS/llvm-cbe#210

u128/i128 (in core::{fmt, num, slice})

llvm-cbe does not support data types that exceed 64 bits, and of course SDCC does, so it must be removed before compilation.
There is already a function to turn off floating point fmt as a cfg option (no_fp_fmt_parse), so I'm going to make similar function and contribute to Rust. (like no_128_fmt_parse)
I think It can be solved by removing the 128bits parts that don't used with llvm-link.

• https://internals.rust-lang.org/t/core-add-cfg-no-128bits-fmt-parse/21701

LLVM-CBE error 1

• (In progress)
  When hiding all the above issues by editing llvm-ir, I get an llvm-cbe error.
  This error occured in CBackend.cpp#L4558

I think it's caused by an unsupported instruction, but I'm not sure exactly where it happened.

elemT == funT->getParamType(i) in:   ret void @
elemT == funT->getParamType(i)
UNREACHABLE executed at /home/zlfn/rust-z80/llvm-project/llvm/projects/llvm-cbe/lib/Target/CBackend/CBackend.cpp:5754!
 #0 0x000056109454cd72 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /home/zlfn/rust-z80/llvm-project/llvm/lib/Support/Unix/Signals.inc:602:22
 #1 0x000056109454d143 PrintStackTraceSignalHandler(void*) /home/zlfn/rust-z80/llvm-project/llvm/lib/Support/Unix/Signals.inc:675:1
 #2 0x000056109454a881 llvm::sys::RunSignalHandlers() /home/zlfn/rust-z80/llvm-project/llvm/lib/Support/Signals.cpp:104:20
 #3 0x000056109454c6cd SignalHandler(int) /home/zlfn/rust-z80/llvm-project/llvm/lib/Support/Unix/Signals.inc:413:1
 #4 0x00007efc0acc81d0 (/usr/lib/libc.so.6+0x3d1d0)
 #5 0x00007efc0ad213f4 (/usr/lib/libc.so.6+0x963f4)
 #6 0x00007efc0acc8120 raise (/usr/lib/libc.so.6+0x3d120)
 #7 0x00007efc0acaf4c3 abort (/usr/lib/libc.so.6+0x244c3)
 #8 0x0000561094484c6d bindingsErrorHandler(void*, char const*, bool) /home/zlfn/rust-z80/llvm-project/llvm/lib/Support/ErrorHandling.cpp:221:55
 #9 0x00005610932d6fc8 std::pair<std::__strip_reference_wrapper<std::decay<llvm::AttributeList>::type>::__type, std::__strip_reference_wrapper<std::decay<llvm::CallingConv::._anon_132>::type>::__type> std::make_pair<llvm::AttributeList, llvm::CallingConv::._anon_132>(llvm::AttributeList&&, llvm::CallingConv::._anon_132&&) /usr/include/c++/14.2.1/bits/stl_pair.h:1132:5
#10 0x00005610932d0b67 llvm_cbe::CWriter::printIntrinsicDefinition(llvm::FunctionType*, unsigned int, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>, llvm::raw_ostream&) /home/zlfn/rust-z80/llvm-project/llvm/projects/llvm-cbe/lib/Target/CBackend/CBackend.cpp:4563:7
#11 0x00005610932d2052 llvm_cbe::CWriter::printIntrinsicDefinition(llvm::Function&, llvm::raw_ostream&) /home/zlfn/rust-z80/llvm-project/llvm/projects/llvm-cbe/lib/Target/CBackend/CBackend.cpp:4777:27
#12 0x00005610932ca44e llvm_cbe::CWriter::generateHeader(llvm::Module&) /home/zlfn/rust-z80/llvm-project/llvm/projects/llvm-cbe/lib/Target/CBackend/CBackend.cpp:3398:3
#13 0x00005610932c3f17 llvm_cbe::CWriter::doFinalization(llvm::Module&) /home/zlfn/rust-z80/llvm-project/llvm/projects/llvm-cbe/lib/Target/CBackend/CBackend.cpp:2400:50
#14 0x0000561093cdf43b llvm::FPPassManager::doFinalization(llvm::Module&) /home/zlfn/rust-z80/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1499:13
#15 0x0000561093cdfa0e (anonymous namespace)::MPPassManager::runOnModule(llvm::Module&) /home/zlfn/rust-z80/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1586:13
#16 0x0000561093cda448 llvm::legacy::PassManagerImpl::run(llvm::Module&) /home/zlfn/rust-z80/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:535:13
#17 0x0000561093ce0045 llvm::legacy::PassManager::run(llvm::Module&) /home/zlfn/rust-z80/llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1678:1
#18 0x0000561090a3443c compileModule(char**, llvm::LLVMContext&) /home/zlfn/rust-z80/llvm-project/llvm/projects/llvm-cbe/tools/llvm-cbe/llvm-cbe.cpp:352:12
#19 0x0000561090a337cd main /home/zlfn/rust-z80/llvm-project/llvm/projects/llvm-cbe/tools/llvm-cbe/llvm-cbe.cpp:204:35
#20 0x00007efc0acb0e08 (/usr/lib/libc.so.6+0x25e08)
#21 0x00007efc0acb0ecc __libc_start_main (/usr/lib/libc.so.6+0x25ecc)
#22 0x0000561090a32fa5 _start (/home/zlfn/rust-gb/source/out/../../ext/llvm-cbe+0x922fa5)
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: /home/zlfn/rust-gb/source/out/../../ext/llvm-cbe core-2ed864bedde1aa0b.ll

LLVM-CBE errror 2

• (In Progress)
  After upgrading the version to LLVM-19, the following error occurs. It seems to be an error related to LegacyPassManager, and I think it will be resolved by migrating to ModulePassManager. (but not sure)

#0 0x000055d2da99280c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/zlfn/rust-gb/ext/./llvm-cbe+0x22ea80c)
#1 0x000055d2da98fc9b SignalHandler(int) Signals.cpp:0:0
#2 0x00007fabac4bf1d0 (/usr/lib/libc.so.6+0x3d1d0)
#3 0x000055d2d99625a5 llvm_cbe::CWriter::generateHeader(llvm::Module&) (/home/zlfn/rust-gb/ext/./llvm-cbe+0x12ba5a5)
#4 0x000055d2da1a23b0 std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> llvm::function_ref<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>> ()>::callback_fn<llvm::FPPassManager::runOnFunction(llvm::Function&)::'lambda'()>(long) LegacyPassManager.cpp:0:0
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: /home/zlfn/rust-gb/ext/./llvm-cbe core-c7f0b5febd1c5ff8.ll
1.      Running pass 'Function Pass Manager' on module 'core-c7f0b5febd1c5ff8.ll'.
2.      Running pass 'C backend' on function '@_ZN4core3num3fmt4Part5write17h3ba8354fc9370b66E'

[zlfn]

If we raise the Rust version to the latest Nightly, no_fp_fmt_parse works properly, so we don't have to worry about llvm.is.fpclass. But for this, llvm-cbe's LLVM version must be upgraded to LLVM-19.

[zlfn]

Implementation PR for llvm.uadd.sat.i32 and llvm.usub.sat.i16 submitted.
JuliaHubOSS/llvm-cbe#210

[zlfn]

If we raise the Rust version to the latest Nightly, no_fp_fmt_parse works properly, so we don't have to worry about llvm.is.fpclass. But for this, llvm-cbe's LLVM version must be upgraded to LLVM-19.

LLVM-19 Support PR for llvm-cbe submitted.
JuliaHubOSS/llvm-cbe#211

[zlfn]

Partial compilation of the core via llvm-link succeeded. core::fmt is now available for u8/u16/i8/i16

[zlfn]

Thanks to the latest optimize_for_size flag, It looks like we can reduce the size of fmt a little bit. However, since llvm-cbe causes Pass related errors, we need to resolve LLVM-CBE error2.
rust-lang/rust#125612