LLVM assertion showing Dict of Union{}

[JeffBezanson]

julia> Dict{Union{},Union{}}()
julia: /home/jeff/src/julia-master/julia/deps/srccache/llvm-3.7.1/lib/CodeGen/LiveVariables.cpp:114: void llvm::LiveVariables::MarkVirtRegAliveInBlock(llvm::LiveVariables::VarInfo&, llvm::MachineBasicBlock*, llvm::MachineBasicBlock*, std::vector<llvm::MachineBasicBlock*>&): Assertion `MBB != &MF->front() && "Can't find reaching def for virtreg"' failed.
Aborted (core dumped)

Works in 0.4.

[vtjnash]

seems to work for me (llvm 3.3 and 3.7.1 on OS X). is this perhaps a llvm regression or linux-specific?

[Keno]

I can reproduce this on both Linux/OSX with

override LLVM_ASSERTIONS=1
override USE_LLVM_SHLIB=1

[yuyichao]

With julia-debug

julia> Dict{Union{},Union{}}()
Instruction does not dominate all uses!
  %840 = call %jl_value_t* @jl_apply_generic(%jl_value_t** %34, i32 3), !dbg !222
  store %jl_value_t* %840, %jl_value_t** %286, !dbg !234
LLVM ERROR: Broken function found, compilation aborted!

[vtjnash]

ah, ok. it seems i couldn't reproduce because i was on the #15444 branch (in particular, that branch never uses SSA values directly for variables and lets mem2reg make them SSA only if it considers that possible )

[JeffBezanson]

fixed by #15444.

[tkelman]

add as a test