[AVR] crash: "Value is not an N-bit unsigned value" when enabling asserts

[aykevl]

Using the following IR:

target datalayout = "e-P1-p:16:8-i8:8-i16:8-i32:8-i64:8-f32:8-f64:8-n8-a:8"
target triple = "avr"

define float @__addsf3(i32 %0) addrspace(1) {
  %2 = icmp ult i32 %0, -2139095039
  br i1 %2, label %3, label %4

3:                                                ; preds = %1
  ret float 0.000000e+00

4:                                                ; preds = %1
  ret float 0.000000e+00
}

Results in a crash when compiled:

$ llvm-build.main/bin/llc reduced.ll
llc: /home/ayke/src/tinygo/tinygo/llvm-project.main/llvm/include/llvm/ADT/APInt.h:127: llvm::APInt::APInt(unsigned int, uint64_t, bool, bool): Assertion `llvm::isUIntN(BitWidth, val) && "Value is not an N-bit unsigned value"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: llvm-build.main/bin/llc reduced.ll
1.	Running pass 'Function Pass Manager' on module 'reduced.ll'.
2.	Running pass 'AVR DAG->DAG Instruction Selection' on function '@__addsf3'
 #0 0x0000000004d5abb0 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (llvm-build.main/bin/llc+0x4d5abb0)
 #1 0x0000000004d5842c SignalHandler(int) Signals.cpp:0:0
 #2 0x0000ffff66724840 (linux-vdso.so.1+0x840)
 #3 0x0000ffff661ff05c __pthread_kill_implementation (/lib64/libc.so.6+0x8f05c)
 #4 0x0000ffff661ab53c gsignal (/lib64/libc.so.6+0x3b53c)
 #5 0x0000ffff66195a48 abort (/lib64/libc.so.6+0x25a48)
 #6 0x0000ffff661a3f60 __assert_fail_base (/lib64/libc.so.6+0x33f60)
 #7 0x0000000004aeafa8 llvm::SelectionDAG::getConstant(unsigned long, llvm::SDLoc const&, llvm::EVT, bool, bool) (llvm-build.main/bin/llc+0x4aeafa8)
 #8 0x0000000002f8afb8 llvm::AVRTargetLowering::getAVRCmp(llvm::SDValue, llvm::SDValue, llvm::ISD::CondCode, llvm::SDValue&, llvm::SelectionDAG&, llvm::SDLoc) const AVRISelLowering.cpp:0:0
 #9 0x0000000002f8b8fc llvm::AVRTargetLowering::LowerSETCC(llvm::SDValue, llvm::SelectionDAG&) const AVRISelLowering.cpp:0:0
#10 0x0000000004a3dd24 llvm::TargetLowering::LowerOperationWrapper(llvm::SDNode*, llvm::SmallVectorImpl<llvm::SDValue>&, llvm::SelectionDAG&) const (llvm-build.main/bin/llc+0x4a3dd24)
#11 0x0000000004b371dc llvm::DAGTypeLegalizer::CustomLowerNode(llvm::SDNode*, llvm::EVT, bool) LegalizeTypes.cpp:0:0
#12 0x0000000004bb5704 llvm::DAGTypeLegalizer::ExpandIntegerOperand(llvm::SDNode*, unsigned int) LegalizeIntegerTypes.cpp:0:0
#13 0x0000000004b37e00 llvm::DAGTypeLegalizer::run() LegalizeTypes.cpp:0:0
#14 0x0000000004b38a80 llvm::SelectionDAG::LegalizeTypes() (llvm-build.main/bin/llc+0x4b38a80)
#15 0x0000000004b24c98 llvm::SelectionDAGISel::CodeGenAndEmitDAG() (llvm-build.main/bin/llc+0x4b24c98)
#16 0x0000000004b28208 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (llvm-build.main/bin/llc+0x4b28208)
#17 0x0000000004b29a38 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (llvm-build.main/bin/llc+0x4b29a38)
#18 0x0000000004b15bac llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) (llvm-build.main/bin/llc+0x4b15bac)
#19 0x0000000003abef9c llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.0) MachineFunctionPass.cpp:0:0
#20 0x0000000004124c00 llvm::FPPassManager::runOnFunction(llvm::Function&) (llvm-build.main/bin/llc+0x4124c00)
#21 0x0000000004124e1c llvm::FPPassManager::runOnModule(llvm::Module&) (llvm-build.main/bin/llc+0x4124e1c)
#22 0x0000000004125920 llvm::legacy::PassManagerImpl::run(llvm::Module&) (llvm-build.main/bin/llc+0x4125920)
#23 0x000000000252f5e0 compileModule(char**, llvm::LLVMContext&) llc.cpp:0:0
#24 0x0000000002530060 main (llvm-build.main/bin/llc+0x2530060)
#25 0x0000ffff6619625c __libc_start_call_main (/lib64/libc.so.6+0x2625c)
#26 0x0000ffff6619633c __libc_start_main@GLIBC_2.17 (/lib64/libc.so.6+0x2633c)
#27 0x00000000025244f0 _start (llvm-build.main/bin/llc+0x25244f0)
fish: Job 1, 'llvm-build.main/bin/llc reduced…' terminated by signal SIGABRT (Abort)

This is LLVM 20.x, at commit hash 87f0227. I did not test LLVM 21. Note that this only happens when LLVM is built with assertions enabled (they're disabled by default).

[aykevl]

Yes, also reproduces in LLVM 21 (80a6bc7):

$ llvm-build.main/bin/llc reduced.ll
llc: /home/ayke/src/tinygo/tinygo/llvm-project.main/llvm/include/llvm/ADT/APInt.h:127: llvm::APInt::APInt(unsigned int, uint64_t, bool, bool): Assertion `llvm::isUIntN(BitWidth, val) && "Value is not an N-bit unsigned value"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: llvm-build.main/bin/llc reduced.ll
1.	Running pass 'Function Pass Manager' on module 'reduced.ll'.
2.	Running pass 'AVR DAG->DAG Instruction Selection' on function '@__addsf3'
 #0 0x00000000053423d0 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (llvm-build.main/bin/llc+0x53423d0)
 #1 0x000000000533fc0c SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
 #2 0x0000ffff6fc40840 (linux-vdso.so.1+0x840)
 #3 0x0000ffff6f71f05c __pthread_kill_implementation (/lib64/libc.so.6+0x8f05c)
 #4 0x0000ffff6f6cb53c gsignal (/lib64/libc.so.6+0x3b53c)
 #5 0x0000ffff6f6b5a48 abort (/lib64/libc.so.6+0x25a48)
 #6 0x0000ffff6f6c3f60 __assert_fail_base (/lib64/libc.so.6+0x33f60)
 #7 0x00000000050cba68 llvm::SelectionDAG::getConstant(unsigned long, llvm::SDLoc const&, llvm::EVT, bool, bool) (llvm-build.main/bin/llc+0x50cba68)
 #8 0x00000000034f5238 llvm::AVRTargetLowering::getAVRCmp(llvm::SDValue, llvm::SDValue, llvm::ISD::CondCode, llvm::SDValue&, llvm::SelectionDAG&, llvm::SDLoc) const AVRISelLowering.cpp:0:0
 #9 0x00000000034f5b7c llvm::AVRTargetLowering::LowerSETCC(llvm::SDValue, llvm::SelectionDAG&) const AVRISelLowering.cpp:0:0
#10 0x000000000501b684 llvm::TargetLowering::LowerOperationWrapper(llvm::SDNode*, llvm::SmallVectorImpl<llvm::SDValue>&, llvm::SelectionDAG&) const (llvm-build.main/bin/llc+0x501b684)
#11 0x0000000005116e64 llvm::DAGTypeLegalizer::CustomLowerNode(llvm::SDNode*, llvm::EVT, bool) LegalizeTypes.cpp:0:0
#12 0x0000000005198a84 llvm::DAGTypeLegalizer::ExpandIntegerOperand(llvm::SDNode*, unsigned int) LegalizeIntegerTypes.cpp:0:0
#13 0x0000000005117aa0 llvm::DAGTypeLegalizer::run() LegalizeTypes.cpp:0:0
#14 0x0000000005118694 llvm::SelectionDAG::LegalizeTypes() (llvm-build.main/bin/llc+0x5118694)
#15 0x00000000051048fc llvm::SelectionDAGISel::CodeGenAndEmitDAG() (llvm-build.main/bin/llc+0x51048fc)
#16 0x0000000005107e0c llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) (llvm-build.main/bin/llc+0x5107e0c)
#17 0x000000000510967c llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) (llvm-build.main/bin/llc+0x510967c)
#18 0x00000000050f536c llvm::SelectionDAGISelLegacy::runOnMachineFunction(llvm::MachineFunction&) (llvm-build.main/bin/llc+0x50f536c)
#19 0x0000000004071364 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.0) MachineFunctionPass.cpp:0:0
#20 0x000000000470dc40 llvm::FPPassManager::runOnFunction(llvm::Function&) (llvm-build.main/bin/llc+0x470dc40)
#21 0x000000000470de5c llvm::FPPassManager::runOnModule(llvm::Module&) (llvm-build.main/bin/llc+0x470de5c)
#22 0x000000000470e920 llvm::legacy::PassManagerImpl::run(llvm::Module&) (llvm-build.main/bin/llc+0x470e920)
#23 0x0000000002a95790 compileModule(char**, llvm::LLVMContext&) llc.cpp:0:0
#24 0x0000000002a961e4 main (llvm-build.main/bin/llc+0x2a961e4)
#25 0x0000ffff6f6b625c __libc_start_call_main (/lib64/libc.so.6+0x2625c)
#26 0x0000ffff6f6b633c __libc_start_main@GLIBC_2.17 (/lib64/libc.so.6+0x2633c)
#27 0x0000000002a8a1b0 _start (llvm-build.main/bin/llc+0x2a8a1b0)
fish: Job 1, 'llvm-build.main/bin/llc reduced…' terminated by signal SIGABRT (Abort)

[aykevl]

Not an issue in LLVM 19, so it's a regression in LLVM 20.

[RKSimon]

This was probably missed in the getConstant/getSignedConstant refactor

[aykevl]

Bisected this bug, and the first bad commit is 3e1b55c (#117558). So yeah looks like you're right @RKSimon.

[aykevl]

The following line is the line that causes the crash:

llvm-project/llvm/lib/Target/AVR/AVRISelLowering.cpp

Line 716 in 90d1d23

RHS = DAG.getConstant(C->getSExtValue() + 1, DL, VT);