Segfault with llvmcall and @eval

[thomasfaingnaert]

I'm wrapping a series of related LLVM IR snippets using llvmcall and @eval, and stumbled upon a segmentation fault if llvmcall is invoked with a list of declarations.

As an illustrative example, suppose we want to wrap addition and substraction:

for func in (:add, :sub)
    func_name = Symbol("do_", func)
    llvm_inst = string(func)

    @eval $func_name(x, y) = Base.llvmcall(
        "%res = $($(llvm_inst)) i64 %0, %1
         ret i64 %res", Int64, Tuple{Int64, Int64}, x, y)
end

Now, do_add(1, 2) and do_sub(1, 2) return 3 and -1, as expected.

However, I need the second form of llvmcall, which includes declarations (just an empty string for this example to not complicate matters):

for func in (:add, :sub)
    func_name = Symbol("do_", func)
    llvm_inst = string(func)

    @eval $func_name(x, y) = Base.llvmcall(("",
        "%res = $($(llvm_inst)) i64 %0, %1
         ret i64 %res"), Int64, Tuple{Int64, Int64}, x, y)
end

Executing do_add(1, 2) now results in a segfault:

signal (11): Segmentation fault
in expression starting at REPL[2]:1
eval_value at /buildworker/worker/package_linux64/build/src/interpreter.c:374
do_call at /buildworker/worker/package_linux64/build/src/interpreter.c:322
eval_value at /buildworker/worker/package_linux64/build/src/interpreter.c:411
unknown function (ip: 0xfffffffffffffffe)
unknown function (ip: 0x7fdb04b1310f)
unknown function (ip: 0x3100000005)
jl_interpret_toplevel_expr_in at /buildworker/worker/package_linux64/build/src/interpreter.c:927
try_eval at /buildworker/worker/package_linux64/build/src/ccall.cpp:637
emit_llvmcall at /buildworker/worker/package_linux64/build/src/ccall.cpp:861
emit_intrinsic at /buildworker/worker/package_linux64/build/src/intrinsics.cpp:875
emit_call at /buildworker/worker/package_linux64/build/src/codegen.cpp:3243
emit_expr at /buildworker/worker/package_linux64/build/src/codegen.cpp:4029
emit_ssaval_assign at /buildworker/worker/package_linux64/build/src/codegen.cpp:3734
emit_stmtpos at /buildworker/worker/package_linux64/build/src/codegen.cpp:3926 [inlined]
emit_function at /buildworker/worker/package_linux64/build/src/codegen.cpp:6404
jl_compile_linfo at /buildworker/worker/package_linux64/build/src/codegen.cpp:1196
jl_compile_method_internal at /buildworker/worker/package_linux64/build/src/gf.c:1775
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2196
do_call at /buildworker/worker/package_linux64/build/src/interpreter.c:323
eval_value at /buildworker/worker/package_linux64/build/src/interpreter.c:411
eval_stmt_value at /buildworker/worker/package_linux64/build/src/interpreter.c:362 [inlined]
eval_body at /buildworker/worker/package_linux64/build/src/interpreter.c:772
jl_interpret_toplevel_thunk_callback at /buildworker/worker/package_linux64/build/src/interpreter.c:884
unknown function (ip: 0xfffffffffffffffe)
unknown function (ip: 0x7fdb04b1308f)
unknown function (ip: 0xffffffffffffffff)
jl_interpret_toplevel_thunk at /buildworker/worker/package_linux64/build/src/interpreter.c:893
jl_toplevel_eval_flex at /buildworker/worker/package_linux64/build/src/toplevel.c:815
jl_toplevel_eval_flex at /buildworker/worker/package_linux64/build/src/toplevel.c:764
jl_toplevel_eval_in at /buildworker/worker/package_linux64/build/src/toplevel.c:844
eval at ./boot.jl:330
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2191
eval_user_input at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.2/REPL/src/REPL.jl:86
run_backend at /home/thomas/.julia/packages/Revise/cbX7Q/src/Revise.jl:973
#79 at ./task.jl:268
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2197
jl_apply at /buildworker/worker/package_linux64/build/src/julia.h:1614 [inlined]
start_task at /buildworker/worker/package_linux64/build/src/task.c:596
unknown function (ip: 0xffffffffffffffff)
Allocations: 4831791 (Pool: 4830554; Big: 1237); GC: 10
Segmentation fault (core dumped)

However, explicitly declaring do_add and do_sub works:

do_add(x, y) = Base.llvmcall(("", "%res = add i64 %0, %1
                                   ret i64 %res"), Int64, Tuple{Int64, Int64}, x, y)
do_sub(x, y) = Base.llvmcall(("", "%res = sub i64 %0, %1
                                   ret i64 %res"), Int64, Tuple{Int64, Int64}, x, y)

do_add(1, 2) returns 3, as expected.

Is this a bug or am I doing something wrong here?

Output of versioninfo():

Julia Version 1.2.0
Commit c6da87ff4b (2019-08-20 00:03 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i7-6500U CPU @ 2.50GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.1 (ORCJIT, skylake)
Environment:
  JULIA_EDITOR = gvim --remote-silent

[maleadt]

#25041, arguments to llvmcall need to be literals.

julia> for func in (:add, :sub)
           func_name = Symbol("do_", func)
           llvm_inst = string(func)

           x = ("",
                "%res = $llvm_inst i64 %0, %1
                 ret i64 %res")
           @eval $func_name(x, y) = Base.llvmcall($x, Int64, Tuple{Int64, Int64}, x, y)
       end

julia> do_add(1, 2)
3