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LLVM asserts in ARM ISel with "This value type is not natively supported!" while compiling Gecko #39429

Open Quuxplusone opened 5 years ago

Quuxplusone commented 5 years ago
Bugzilla Link PR40458
Status CONFIRMED
Importance P normal
Reported by changyihsin (changyihsin@gmail.com)
Reported on 2019-01-25 01:48:41 -0800
Last modified on 2019-02-25 01:41:20 -0800
Version 6.0
Hardware PC Linux
CC florian_hahn@apple.com, htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk, rnk@google.com, smithp352@googlemail.com, Ties.Stuij@arm.com
Fixed by commit(s)
Attachments clangCrash.log (8925 bytes, text/plain)
Blocks
Blocked by
See also 
Created attachment 21379
clang crash log

When I compiler firefox gecko48 with clang, I encounter the clang crash when
compiling gecko/js/src/ctypes/CTypes.cpp.

Looks like clang is crashed while compiling this function.

js::ctypes::GetDeflatedUTF8StringLength()

Not quite sure how to debug further or how to find exactly line of code leads
to clang crash.
Quuxplusone commented 5 years ago

Attached clangCrash.log (8925 bytes, text/plain): clang crash log

Quuxplusone commented 5 years ago

Looks like the segfault is in the backend (Machine Loop Invariant Code Motion) building for thumbv4t--linux-android. It would be helpful if you could attach the bitcode file generated by passing '-emit-llvm' to Clang.

Also, it looks like you are using clang 6, which is about a year old. Any chance you could try with a more recent build/release? If you could use a build with assertions enabled, that would be helpful too, as the issue might appear earlier.

Quuxplusone commented 5 years ago 
Preprocessed source(s) and associated run script(s) are located at:
https://drive.google.com/file/d/195yKyGQ6jxJpid2H9Uknd2vwizDWDe71/view?usp=sharing
Quuxplusone commented 5 years ago 
> It would be helpful if you
> could attach the bitcode file generated by passing '-emit-llvm' to Clang.

I use the command in below URL to generate bitcode.
https://pastebin.com/Qbj93zkS

The bitcode is located in
https://drive.google.com/file/d/1OOCxpTcmY_AVIhp8uvkxzaG8iUbMIxJP/view?usp=sharing
Quuxplusone commented 5 years ago

I repro'd and started a reduction.

Quuxplusone commented 5 years ago 
Stack says it's crashing in ARM ISel:

1.      <eof> parser at end of file
2.      Code generation
3.      Running pass 'Function Pass Manager' on module 'ctypes.cpp'.
4.      Running pass 'ARM Instruction Selection' on function
'@_ZN2js6ctypes27GetDeflatedUTF8StringLengthIhEEjP9JSContextPKT_j'
 #0 0x0000000004099179 PrintStackTrace /usr/local/google/home/rnk/llvm-project/llvm/lib/Support/Unix/Signals.inc:494:13
 #1 0x0000000004099179 PrintStackTraceSignalHandler(void*) /usr/local/google/home/rnk/llvm-project/llvm/lib/Support/Unix/Signals.inc:557:0
 #2 0x0000000004096f38 llvm::sys::RunSignalHandlers() /usr/local/google/home/rnk/llvm-project/llvm/lib/Support/Signals.cpp:69:18
 #3 0x0000000004099596 SignalHandler(int) /usr/local/google/home/rnk/llvm-project/llvm/lib/Support/Unix/Signals.inc:357:1
 #4 0x00007fb3764340c0 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x110c0)
 #5 0x00007fb374fc5fcf gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x32fcf)
 #6 0x00007fb374fc73fa abort (/lib/x86_64-linux-gnu/libc.so.6+0x343fa)
 #7 0x00007fb374fbee37 (/lib/x86_64-linux-gnu/libc.so.6+0x2be37)
 #8 0x00007fb374fbeee2 (/lib/x86_64-linux-gnu/libc.so.6+0x2bee2)
 #9 0x0000000002aa8dce (/usr/local/google/home/rnk/llvm-project/build/bin/clang+0x2aa8dce)
#10 0x0000000004de633c llvm::InstrEmitter::getVR(llvm::SDValue,
llvm::DenseMap<llvm::SDValue, unsigned int, llvm::DenseMapInfo<llvm::SDValue>,
llvm::detail::DenseMapPair<llvm::SDValue, unsigned int> >&)
/usr/local/google/home/rnk/llvm-project/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp:294:14
#11 0x0000000004de651d
llvm::InstrEmitter::AddRegisterOperand(llvm::MachineInstrBuilder&,
llvm::SDValue, unsigned int, llvm::MCInstrDesc const*,
llvm::DenseMap<llvm::SDValue, unsigned int, llvm::DenseMapInfo<llvm::SDValue>,
llvm::detail::DenseMapPair<llvm::SDValue, unsigned int> >&, bool, bool, bool)
/usr/local/google/home/rnk/llvm-project/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp:321:19
#12 0x0000000004de68c7
llvm::InstrEmitter::AddOperand(llvm::MachineInstrBuilder&, llvm::SDValue,
unsigned int, llvm::MCInstrDesc const*, llvm::DenseMap<llvm::SDValue, unsigned
int, llvm::DenseMapInfo<llvm::SDValue>,
llvm::detail::DenseMapPair<llvm::SDValue, unsigned int> >&, bool, bool, bool)
/usr/local/google/home/rnk/llvm-project/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp:464:1
#13 0x0000000004de9111 llvm::InstrEmitter::EmitMachineNode(llvm::SDNode*, bool,
bool, llvm::DenseMap<llvm::SDValue, unsigned int,
llvm::DenseMapInfo<llvm::SDValue>, llvm::detail::DenseMapPair<llvm::SDValue,
unsigned int> >&) /usr/local/google/home/rnk/llvm-
project/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp:911:5
#14 0x0000000004de0bfe
llvm::ScheduleDAGSDNodes::EmitSchedule(llvm::MachineInstrBundleIterator<llvm::MachineInstr,
false>&)::$_0::operator()(llvm::SDNode*, bool, bool,
llvm::DenseMap<llvm::SDValue, unsigned int, llvm::DenseMapInfo<llvm::SDValue>,
llvm::detail::DenseMapPair<llvm::SDValue, unsigned int> >&) const
/usr/local/google/home/rnk/llvm-project/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp:831:53
#15 0x0000000004de0404
llvm::ScheduleDAGSDNodes::EmitSchedule(llvm::MachineInstrBundleIterator<llvm::MachineInstr,
false>&) /usr/local/google/home/rnk/llvm-
project/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp:892:9
#16 0x0000000004d6029f llvm::SelectionDAGISel::CodeGenAndEmitDAG()
/usr/local/google/home/rnk/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:968:42
#17 0x0000000004d5caea
llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&)
/usr/local/google/home/rnk/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:1813:7
#18 0x0000000004d59003
llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&)
/usr/local/google/home/rnk/llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp:497:7
Quuxplusone commented 5 years ago 
A reduction:

$ cat ctypes.cpp
char *a, *c;
int b;
unsigned int d;
int e() {
  int f;
  c = a + b;
  for (; a != c; a++) {
    d = *a;
    f++;
  }
  return f;
}

$ clang -cc1 -triple thumbv4t--linux-android -emit-obj -target-cpu arm7tdmi -
target-feature +soft-float-abi -target-feature -fp-only-sp -target-feature -d16
-target-feature +vfp3 -target-feature -fp16 -target-feature -vfp4 -target-
feature -fp-armv8 -target-feature +neon -target-feature -crypto -target-feature
+strict-align -target-abi aapcs-linux -mfloat-abi soft -O3 -std=gnu++14 -
vectorize-loops -vectorize-slp -x c++ -w ctypes.cpp
...
clang: /usr/local/google/home/rnk/llvm-
project/llvm/include/llvm/CodeGen/TargetLowering.h:627: virtual const
llvm::TargetRegisterClass *llvm::TargetLoweringBase::getRegClassFor(llvm::MVT)
const: Assertion `RC && "This value type is not natively supported!"' failed.
...
Quuxplusone commented 5 years ago

I haven't looked into the crash in any great detail, just picking on the target feature string.

There is a combination of armv4-t with a -target-feature +vfp3 and -target-feature +neon. This is not a legal ARM Architecture. The target-feature +neon requires armv7-a or armv7-r. I don't believe vfp3 is not supported on armv4-t either but I don't think that is the problem as we have -mfloat-abi=soft.

If I remove the +neon this will compile correctly, as is also the case if we raise the target architecture to armv7a v9a --triple thumbv7a-linux-android (remember to remove or alter --target-cpu to a v7a cpu like cortex-a9. There is still a problem here as we shouldn't get as far as an assertion, but I'd be willing to bet that this something to do with something not supported on v4t being introduced by neon.

As far as I know the earliest Android supported architecture is armv6 for the arm1176. This does not support neon either. I think the latest versions of Android require armv7-a and neon.