Added flag for legacy RISCV extension ordering #14
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Added a flag to enable legacy extension name ordering when fowarding RISCV extensions to -march option of asm Usage: clang -menable-legacy-march-order ...
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djtodoro
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Dec 21, 2023
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…onger cause a crash (#116569)
This PR fixes a bug introduced by #110199, which causes any half float
argument to crash the compiler on MIPS64.
Currently compiling this bit of code with `llc -mtriple=mips64`:
```
define void @half_args(half %a) nounwind {
entry:
ret void
}
```
Crashes with the following log:
```
LLVM ERROR: unable to allocate function argument #0
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0. Program arguments: llc -mtriple=mips64
1. Running pass 'Function Pass Manager' on module '<stdin>'.
2. Running pass 'MIPS DAG->DAG Pattern Instruction Selection' on function '@half_args'
#0 0x000055a3a4013df8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x32d0df8)
#1 0x000055a3a401199e llvm::sys::RunSignalHandlers() (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x32ce99e)
#2 0x000055a3a40144a8 SignalHandler(int) Signals.cpp:0:0
#3 0x00007f00bde558c0 __restore_rt libc_sigaction.c:0:0
#4 0x00007f00bdea462c __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
#5 0x00007f00bde55822 gsignal ./signal/../sysdeps/posix/raise.c:27:6
#6 0x00007f00bde3e4af abort ./stdlib/abort.c:81:7
#7 0x000055a3a3f80e3c llvm::report_fatal_error(llvm::Twine const&, bool) (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x323de3c)
#8 0x000055a3a2e20dfa (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x20dddfa)
#9 0x000055a3a2a34e20 llvm::MipsTargetLowering::LowerFormalArguments(llvm::SDValue, unsigned int, bool, llvm::SmallVectorImpl<llvm::ISD::InputArg> const&, llvm::SDLoc const&, llvm::SelectionDAG&, llvm::SmallVectorImpl<llvm::SDValue>&) const MipsISelLowering.cpp:0:0
#10 0x000055a3a3d896a9 llvm::SelectionDAGISel::LowerArguments(llvm::Function const&) (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x30466a9)
#11 0x000055a3a3e0b3ec llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x30c83ec)
#12 0x000055a3a3e09e21 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x30c6e21)
#13 0x000055a3a2aae1ca llvm::MipsDAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) MipsISelDAGToDAG.cpp:0:0
#14 0x000055a3a3e07706 llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x30c4706)
#15 0x000055a3a3051ed6 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x230eed6)
#16 0x000055a3a35a3ec9 llvm::FPPassManager::runOnFunction(llvm::Function&) (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x2860ec9)
#17 0x000055a3a35ac3b2 llvm::FPPassManager::runOnModule(llvm::Module&) (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x28693b2)
#18 0x000055a3a35a499c llvm::legacy::PassManagerImpl::run(llvm::Module&) (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x286199c)
#19 0x000055a3a262abbb main (/home/davide/Ps2/rps2-tools/prefix/bin/llc+0x18e7bbb)
#20 0x00007f00bde3fc4c __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#21 0x00007f00bde3fd05 call_init ./csu/../csu/libc-start.c:128:20
#22 0x00007f00bde3fd05 __libc_start_main@GLIBC_2.2.5 ./csu/../csu/libc-start.c:347:5
#23 0x000055a3a2624921 _start /builddir/glibc-2.39/csu/../sysdeps/x86_64/start.S:117:0
```
This is caused by the fact that after the change, `f16`s are no longer
lowered as `f32`s in calls.
Two possible fixes are available:
- Update calling conventions to properly support passing `f16` as
integers.
- Update `useFPRegsForHalfType()` to return `true` so that `f16` are
still kept in `f32` registers, as before #110199.
This PR implements the first solution to not introduce any more ABI
changes as #110199 already did.
As of what is the correct ABI for halfs, I don't think there is a
correct answer. GCC doesn't support halfs on MIPS, and I couldn't find
any information on old MIPS ABI manuals either.
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