On Fri, 2024-12-20 at 15:34 -0700, Nathan Chancellor wrote: > > Now, the thing is, these ASSERT()s are checking for divide-by-zero, I > > suspect clang figured that out and invokes UB on us and just stops > > code-gen. > > Yeah, I think your analysis is spot on, as this was introduced by a > change in clang from a few months ago according to my bisect: > > https://github.com/llvm/llvm-project/commit/37932643abab699e8bb1def08b7eb4eae7ff1448 > > Since the ASSERT does not do anything to prevent the divide by zero (it > just flags it with WARN_ON) and the rest of the code doesn't either, I > assume that the codegen stops as soon as it encounters the unreachable > that change created from the path where divide by zero would occur via > > dc_fixpt_recip() -> > dc_fixpt_from_fraction() -> > complete_integer_division_u64() -> > div64_u64_rem() > > Shouldn't callers of division functions harden them against dividing by > zero? Yes I think it'd be the correct solution. -- Xi Ruoyao <xry111@xxxxxxxxxxx> School of Aerospace Science and Technology, Xidian University
