AssertionError: useidx !== nothing #319
Comments
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I've managed to figure out what's going on here, and have discussed it in here . The upshot is that you can patch this with the following code: # Apply fix from Jules Merck.
@eval CC function populate_def_use_map!(tpdum::TwoPhaseDefUseMap, scanner::BBScanner)
scan!(scanner, false) do inst::Instruction, lstmt::Int, bb::Int
for ur in userefs(inst[:stmt]) # replace inst with inst[:stmt]
val = ur[]
if isa(val, SSAValue)
push!(tpdum[val.id], inst.idx)
end
end
return true
end
end
@eval CC function ((; sv)::ScanStmt)(inst::Instruction, lstmt::Int, bb::Int)
stmt = inst[:stmt]
if isa(stmt, EnterNode)
# try/catch not yet modeled
give_up_refinements!(sv)
return true # don't bail out early -- replaces `nothing` with `true`
end
scan_non_dataflow_flags!(inst, sv)
stmt_inconsistent = scan_inconsistency!(inst, sv)
if stmt_inconsistent
if !has_flag(inst[:flag], IR_FLAG_NOTHROW)
# Taint :consistent if this statement may raise since :consistent requires
# consistent termination. TODO: Separate :consistent_return and :consistent_termination from :consistent.
sv.all_retpaths_consistent = false
end
if inst.idx == lstmt
if isa(stmt, ReturnNode) && isdefined(stmt, :val)
sv.all_retpaths_consistent = false
elseif isa(stmt, GotoIfNot)
# Conditional Branch with inconsistent condition.
# If we do not know this function terminates, taint consistency, now,
# :consistent requires consistent termination. TODO: Just look at the
# inconsistent region.
if !sv.result.ipo_effects.terminates
sv.all_retpaths_consistent = false
elseif visit_conditional_successors(sv.lazypostdomtree, sv.ir, bb) do succ::Int
return any_stmt_may_throw(sv.ir, succ)
end
# check if this `GotoIfNot` leads to conditional throws, which taints consistency
sv.all_retpaths_consistent = false
else
(; cfg, domtree) = get!(sv.lazyagdomtree)
for succ in iterated_dominance_frontier(cfg, BlockLiveness(sv.ir.cfg.blocks[bb].succs, nothing), domtree)
if succ == length(cfg.blocks)
# Phi node in the virtual exit -> We have a conditional
# return. TODO: Check if all the retvals are egal.
sv.all_retpaths_consistent = false
else
visit_bb_phis!(sv.ir, succ) do phiidx::Int
push!(sv.inconsistent, phiidx)
end
end
end
end
end
end
end
# Do not bail out early, as this can cause tpdum counts to be off.
# # bail out early if there are no possibilities to refine the effects
# if !any_refinable(sv)
# return nothing
# end
return true
end
@eval CC function scan_inconsistency!(inst::Instruction, sv::PostOptAnalysisState)
flag = inst[:flag]
stmt_inconsistent = !has_flag(flag, IR_FLAG_CONSISTENT)
stmt = inst[:stmt]
# Special case: For `getfield` and memory operations, we allow inconsistency of the :boundscheck argument
(; inconsistent, tpdum) = sv
# Main.@show stmt
if iscall_with_boundscheck(stmt, sv)
for i = 1:length(stmt.args) # explore all args -- don't assume boundscheck is not an SSA
val = stmt.args[i]
if isa(val, SSAValue)
stmt_inconsistent |= val.id in inconsistent
count!(tpdum, val)
end
end
else
for ur in userefs(stmt)
val = ur[]
if isa(val, SSAValue)
stmt_inconsistent |= val.id in inconsistent
count!(tpdum, val)
end
end
end
stmt_inconsistent && push!(inconsistent, inst.idx)
return stmt_inconsistent
end
I've verified locally that this seems to fix the problem (there are two examples commented out that are tagging with this issue's number, and they are both fixed with the above patch). edit2: patches updated to cover another couple of holes I found while trying to get this to work on TemporalGPs.jl. See comment on julia lined above for more discussion. |
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Since this problem occurs in the compiler, the best option for users at the minute is literally to copy + paste the above patch as part of their session (if they encounter this problem). Now that I think I know what's going on, I'm going to push to get the fix in and released in the next patch versions of 1.10 and 1.11. This issue needs to remain open until this happens, so it will open for at least a couple more months. |
There is a known issue with
Core.Compiler.populate_use_def_map!, as discussed here: JuliaLang/julia#56193This can result in problems like that encountered by @penelopeysm in this PR: TuringLang/Bijectors.jl#338
For posterity, here is the kind of error that you see if you encounter it:
As you can see from the stack trace, the problem occurs in
_ir_abstract_constant_propagation, which is the function which performs type inference, performs constant propagation, and a few other things (I think).A minimal reproducer on Julia 1.11.1 is:
We could do with a general strategy for working around this whenever it is encountered, or fixing it by patching the compiler internals until it is fixed more widely. Unfortunately, just fixing
CC.populate_use_def_map!does not appear to resolve the problem, so I'm assuming that this is the surface of the problem. In slack, Keno mentioned that the code path on which this occurs is likely under-tested :(edit: I've managed to find a more minimal reproducer:
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