Opaque pointer handling

[vchuravy]

On #2675 we see many errors like

ERROR: Taking the type of an opaque pointer is illegal
│ │ Stacktrace:
│ │   [1] error(s::String)
│ │     @ Base ./error.jl:44
│ │   [2] eltype
│ │     @ ~/.julia/packages/LLVM/iza6e/src/core/type.jl:293 [inlined]
│ │   [3] propagate_returned!(mod::LLVM.Module)
│ │     @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/llvm/transforms.jl:1688
│ │   [4] removeDeadArgs!(mod::LLVM.Module, tm::LLVM.TargetMachine)
│ │     @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/llvm/transforms.jl:2563
│ │   [5] macro expansion
│ │     @ ~/work/Enzyme.jl/Enzyme.jl/src/compiler/optimize.jl:138 [inlined]
│ │   [6] macro expansion
│ │     @ ~/.julia/packages/LLVM/iza6e/src/base.jl:97 [inlined]
│ │   [7] optimize!(mod::LLVM.Module, tm::LLVM.TargetMachine)
│ │     @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/compiler/optimize.jl:29
│ │   [8] compile_unhooked(output::Symbol, job::GPUCompiler.CompilerJob{Enzyme.Compiler.EnzymeTarget{GPUCompiler.NativeCompilerTarget}, Enzyme.Compiler.EnzymeCompilerParams{Enzyme.Compiler.PrimalCompilerParams}})
│ │     @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/compiler.jl:4774
│ │   [9] compile(target::Symbol, job::GPUCompiler.CompilerJob; kwargs::@Kwargs{})
│ │     @ GPUCompiler ~/.julia/packages/GPUCompiler/Gp8bZ/src/driver.jl:67
│ │  [10] compile
│ │     @ ~/.julia/packages/GPUCompiler/Gp8bZ/src/driver.jl:55 [inlined]
│ │  [11] _thunk(job::GPUCompiler.CompilerJob{Enzyme.Compiler.EnzymeTarget{GPUCompiler.NativeCompilerTarget}, Enzyme.Compiler.EnzymeCompilerParams{Enzyme.Compiler.PrimalCompilerParams}}, postopt::Bool)
│ │     @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/compiler.jl:5960
│ │  [12] _thunk
│ │     @ ~/work/Enzyme.jl/Enzyme.jl/src/compiler.jl:5958 [inlined]
│ │  [13] cached_compilation
│ │     @ ~/work/Enzyme.jl/Enzyme.jl/src/compiler.jl:6015 [inlined]
│ │  [14] thunkbase(mi::Core.MethodInstance, World::UInt64, FA::Type{<:Annotation}, A::Type{<:Annotation}, TT::Type, Mode::Enzyme.API.CDerivativeMode, width::Int64, ModifiedBetween::NTuple{N, Bool} where N, ReturnPrimal::Bool, ShadowInit::Bool, ABI::Type, ErrIfFuncWritten::Bool, RuntimeActivity::Bool, StrongZero::Bool, edges::Vector{Any})
│ │     @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/compiler.jl:6131
│ │  [15] thunk_generator(world::UInt64, source::Union{LineNumberNode, Method}, FA::Type, A::Type, TT::Type, Mode::Enzyme.API.CDerivativeMode, Width::Int64, ModifiedBetween::NTuple{N, Bool} where N, ReturnPrimal::Bool, ShadowInit::Bool, ABI::Type, ErrIfFuncWritten::Bool, RuntimeActivity::Bool, StrongZero::Bool, self::Any, fakeworld::Any, fa::Type, a::Type, tt::Type, mode::Type, width::Type, modifiedbetween::Type, returnprimal::Type, shadowinit::Type, abi::Type, erriffuncwritten::Type, runtimeactivity::Type, strongzero::Type)
│ │     @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/compiler.jl:6275
│ │  [16] autodiff
│ │     @ ~/work/Enzyme.jl/Enzyme.jl/src/Enzyme.jl:658 [inlined]
│ │  [17] autodiff
│ │     @ ~/work/Enzyme.jl/Enzyme.jl/src/Enzyme.jl:562 [inlined]
│ │  [18] autodiff
│ │     @ ~/work/Enzyme.jl/Enzyme.jl/src/Enzyme.jl:534 [inlined]
│ │  [19] hvp!(res::Vector{Float64}, f::typeof(f), x::Vector{Float64}, v::Vector{Float64})
│ │     @ Enzyme ~/work/Enzyme.jl/Enzyme.jl/src/sugar.jl:1312

Enzyme.jl/src/llvm/transforms.jl

Lines 1683 to 1688 in 27294f3

	argeltype = if LLVM.version().major >= 12
	# TODO try to get sret element type if possible
	# note currently opaque pointers has this break [and we need to doa check if opaque
	# and if so get inner piece]
	eltype(value_type(arg))
	else

[vchuravy]

Same for lower_convention

 Error During Test at /home/runner/work/Enzyme.jl/Enzyme.jl/test/usermixed.jl:30
  Got exception outside of a @test
  Taking the type of an opaque pointer is illegal
  Stacktrace:
    [1] error(s::String)
      @ Base ./error.jl:44
    [2] eltype
      @ ~/.julia/packages/LLVM/iza6e/src/core/type.jl:293 [inlined]
    [3] lower_convention(functy::Type, mod::LLVM.Module, entry_f::LLVM.Function, actualRetType::Type, RetActivity::Type, TT::Union{Nothing, Type}, run_enzyme::Bool, world::UInt64)
      @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/compiler.jl:3891
    [4] compile_unhooked(output::Symbol, job::GPUCompiler.CompilerJob{Enzyme.Compiler.EnzymeTarget{GPUCompiler.NativeCompilerTarget}, Enzyme.Compiler.EnzymeCompilerParams{Enzyme.Compiler.PrimalCompilerParams}})
      @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/compiler.jl:4725
    [5] compile(target::Symbol, job::GPUCompiler.CompilerJob; kwargs::@Kwargs{})
      @ GPUCompiler ~/.julia/packages/GPUCompiler/Gp8bZ/src/driver.jl:67
    [6] compile
      @ ~/.julia/packages/GPUCompiler/Gp8bZ/src/driver.jl:55 [inlined]
    [7] _thunk(job::GPUCompiler.CompilerJob{Enzyme.Compiler.EnzymeTarget{GPUCompiler.NativeCompilerTarget}, Enzyme.Compiler.EnzymeCompilerParams{Enzyme.Compiler.PrimalCompilerParams}}, postopt::Bool)
      @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/compiler.jl:5960
    [8] _thunk
      @ ~/work/Enzyme.jl/Enzyme.jl/src/compiler.jl:5958 [inlined]

[vchuravy]

Same for removeDeadArgs

Error During Test at /home/runner/work/Enzyme.jl/Enzyme.jl/test/usermixed.jl:59
  Got exception outside of a @test
  Taking the type of an opaque pointer is illegal
  Stacktrace:
    [1] error(s::String)
      @ Base ./error.jl:44
    [2] eltype
      @ ~/.julia/packages/LLVM/iza6e/src/core/type.jl:293 [inlined]
    [3] sret_ty(fn::LLVM.Function, idx::Int64)
      @ Enzyme ~/work/Enzyme.jl/Enzyme.jl/src/utils.jl:490
    [4] removeDeadArgs!(mod::LLVM.Module, tm::LLVM.TargetMachine)
      @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/llvm/transforms.jl:2521
    [5] post_optimize!(mod::LLVM.Module, tm::LLVM.TargetMachine, machine::Bool)
      @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/compiler/optimize.jl:304
    [6] post_optimize!
      @ ~/work/Enzyme.jl/Enzyme.jl/src/compiler/optimize.jl:303 [inlined]
    [7] _thunk(job::GPUCompiler.CompilerJob{Enzyme.Compiler.EnzymeTarget{GPUCompiler.NativeCompilerTarget}, Enzyme.Compiler.EnzymeCompilerParams{Enzyme.Compiler.PrimalCompilerParams}}, postopt::Bool)
      @ Enzyme.Compiler ~/work/Enzyme.jl/Enzyme.jl/src/compiler.jl:5988
    [8] _thunk

[wsmoses]

yeah so re the first we need to parse the sret eltype iirc. Incidentally this is where we are almost certainly going to hit the "LLVM made our life worse as the enzyme_sret attribute cannot be a type attribute and we lost the type"

[wsmoses]

okay this is mostly resolved here: #2764

on 1.10 and 1.11 [which we now have in CI with opaque pointers], some tests do segfault which CI either locally or remotely will just timeout on indefinitely and needs help. relevant mwe here: #2770