| Issue |
183850
|
| Summary |
[hexagon] Machine Copy Propagation assertion failure with HVX debug info
|
| Labels |
bug,
backend:Hexagon
|
| Assignees |
|
| Reporter |
androm3da
|
The Hexagon backend crashes with an assertion failure in `MachineRegisterInfo::updateDbgUsersToReg` in 21.1.8 when compiling Eigen's `test/packetmath.cpp` at `-O2 -g` targeting HVX v68 128B.
Assertion:
```
llvm/include/llvm/CodeGen/MachineRegisterInfo.h:883:
void llvm::MachineRegisterInfo::updateDbgUsersToReg(
llvm::MCRegister, llvm::MCRegister, ArrayRef<llvm::MachineInstr *>) const:
Assertion `MI->hasDebugOperandForReg(NewReg) &&
"Expected debug value to have some overlap with OldReg"' failed.
...
#11 llvm::MachineRegisterInfo::updateDbgUsersToReg MachineCopyPropagation.cpp:0:0
#12 (anonymous namespace)::MachineCopyPropagation::run MachineCopyPropagation.cpp:0:0
#13 (anonymous namespace)::MachineCopyPropagationLegacy::runOnMachineFunction MachineCopyPropagation.cpp:0:0
```
The crash occurs in the `Machine Copy Propagation Pass` on a function performing a 32×32 HVX vector transpose using `V6_vshuffvdd` intrinsics.
The original preprocessed source `compiler_crash_packetmath.cpp` was from Eigen's `packetmath.cpp`. Reduced with `llvm-extract` / `llvm-reduce` - [eig_packetmath_reduced.ll.txt](https://github.com/user-attachments/files/25615997/eig_packetmath_reduced.ll.txt)
### Reproducer command
```bash
llc -mtriple=hexagon-unknown-linux-musl -mcpu=hexagonv68 \
-mattr=+hvxv68,+hvx-length128b -O2 -relocation-model=pic \
-frame-pointer=all -hexagon-small-data-threshold=0 \
-machine-sink-split=0 eig_packetmath_reduced.ll -o /dev/null
```
- `-strip-debug-info` eliminates the crash.
Originally found in `test/packetmath.cpp` w `-DEIGEN_TEST_PART_1=1` and
`-target hexagon-unknown-linux-musl -mv68 -mhvx -mhvx-length=128B -O2 -g -DNDEBUG -DEIGEN_FAST_MATH=1 -fstrict-aliasing -std=c++14`
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