compiler: fix llvmcall segfault with zero-sized types

src/ccall.cpp

@@ -909,6 +909,11 @@ static jl_cgval_t emit_llvmcall(jl_codectx_t &ctx, jl_value_t **args, size_t nar
         jl_value_t *tti = jl_svecref(tt,i);
         bool toboxed;
         Type *t = julia_type_to_llvm(ctx, tti, &toboxed);
+        if (jl_is_datatype(tti) && jl_datatype_size((jl_datatype_t*)tti) == 0) {
+            emit_error(ctx, "llvmcall does not support zero-sized argument types");
+            JL_GC_POP();
+            return jl_cgval_t();
+        }
         argtypes.push_back(t);
         if (4 + i > nargs) {
             emit_error(ctx, "Missing arguments to llvmcall!");
@@ -927,6 +932,11 @@ static jl_cgval_t emit_llvmcall(jl_codectx_t &ctx, jl_value_t **args, size_t nar
     jl_value_t *rtt = rt;
     bool retboxed;
     Type *rettype = julia_type_to_llvm(ctx, rtt, &retboxed);
+    if (jl_is_datatype(rtt) && jl_datatype_size((jl_datatype_t*)rtt) == 0) {
+        emit_error(ctx, "llvmcall does not support zero-sized return types");
+        JL_GC_POP();
+        return jl_cgval_t();
+    }
 
     // Make sure to find a unique name
     std::string ir_name;

test/llvmcall.jl

@@ -218,3 +218,9 @@ s = MyStruct()
 @test eltype(supertype(Core.LLVMPtr{UInt8,1})) <: UInt8
 @test s.kern == 0
 @test reinterpret(Int, s.ptr) == 0
+
+f_zero_arg(x::T) where T = Base.llvmcall("ret i8 %0", Int8, Tuple{T}, x)
+@test_throws ErrorException f_zero_arg(nothing)
+
+f_zero_ret(x::Int8) = Base.llvmcall("ret void", Nothing, Tuple{Int8}, x)
+@test_throws ErrorException f_zero_ret(Int8(1))