ldiv! invokes undefined behavior when calling m_thread_block_size with nthreads == static(0).

[KristofferC]

TriangularSolve.jl/src/TriangularSolve.jl

Line 264 in e425ff5

div_dispatch!(transpose(C), transpose(A), transpose(parent(U)), static(0), Val(true))

and many more places ends up calling m_thread_block_size with nthreads == static(0).

The compiler can then prove that

TriangularSolve.jl/src/TriangularSolve.jl

Line 335 in e425ff5

min(M, VectorizationBase.vcld(M, nb*W)*W)

is called as VectorizationBase.vcld(M, 0) (which ends up calling Base.sdiv_int(x, 0) which is undefined behavior https://llvm.org/docs/LangRef.html#sdiv-instruction) and returns llvm's poison value.

Maybe this should just have been static(1)?

[chriselrod]

Yeah, definitely looks like it should have been 1.