julia> bitstype 8 Foo
julia> convert(Foo, 100)
ERROR: `convert` has no method matching convert(::Type{Foo}, ::Int64)
in convert at base.jl:9
How fast do you want to raise an error? ;-)
On Mon, Oct 20, 2014 at 11:18 AM, Sebastian Good <
[email protected]> wrote:
> When I've run benchmarks with custom bitstypes, they seem to run very
> quickly. But I wouldn't have guessed it from the machine code I can preview
> at the REPL. Can anyone explain what I'm seeing here? (I'm dumping
> @code_llvm as it's more instructive; the @code_native is very large).
> Converting a constant number to a Uint8 is a one-operation function.
> Converting a constant number to a bitstype of the same size seems to do a
> lot more.
>
> julia> @code_llvm convert(Uint8, 100)
>
> define i8 @"julia_convert;19720"(%jl_value_t*, i64) {
> top:
> %2 = trunc i64 %1 to i8, !dbg !772, !julia_type !773
> ret i8 %2, !dbg !772
> }
>
> julia> bitstype 8 Foo
> julia> @code_llvm convert(Foo, 100)
>
> ; Function Attrs: noreturn
> define void @"julia_convert;19725"(%jl_value_t*, i64) #0 {
> top:
> %2 = alloca [5 x %jl_value_t*], align 8
> %.sub = getelementptr inbounds [5 x %jl_value_t*]* %2, i64 0, i64 0
> %3 = getelementptr [5 x %jl_value_t*]* %2, i64 0, i64 2, !dbg !776
> store %jl_value_t* inttoptr (i64 6 to %jl_value_t*), %jl_value_t**
> %.sub, align 8
> %4 = load %jl_value_t*** @jl_pgcstack, align 8, !dbg !776
> %5 = getelementptr [5 x %jl_value_t*]* %2, i64 0, i64 1, !dbg !776
> %.c = bitcast %jl_value_t** %4 to %jl_value_t*, !dbg !776
> store %jl_value_t* %.c, %jl_value_t** %5, align 8, !dbg !776
> store %jl_value_t** %.sub, %jl_value_t*** @jl_pgcstack, align 8, !dbg
> !776
> store %jl_value_t* null, %jl_value_t** %3, align 8
> %6 = getelementptr [5 x %jl_value_t*]* %2, i64 0, i64 3
> store %jl_value_t* null, %jl_value_t** %6, align 8
> %7 = getelementptr [5 x %jl_value_t*]* %2, i64 0, i64 4
> store %jl_value_t* null, %jl_value_t** %7, align 8
> %8 = load %jl_value_t** inttoptr (i64 140384830597872 to %jl_value_t**),
> align 16, !dbg !777
> %9 = getelementptr inbounds %jl_value_t* %8, i64 1, i32 0, !dbg !777
> %10 = load %jl_value_t** %9, align 8, !dbg !777, !tbaa %jtbaa_func
> %11 = bitcast %jl_value_t* %10 to %jl_value_t* (%jl_value_t*,
> %jl_value_t**, i32)*, !dbg !777
> store %jl_value_t* %0, %jl_value_t** %3, align 8, !dbg !777
> %12 = call %jl_value_t* @jl_box_int64(i64 %1), !dbg !777
> store %jl_value_t* %12, %jl_value_t** %6, align 8, !dbg !777
> %13 = load %jl_value_t** inttoptr (i64 140384825150528 to
> %jl_value_t**), align 64, !dbg !777
> store %jl_value_t* %13, %jl_value_t** %7, align 8, !dbg !777
> %14 = call %jl_value_t* %11(%jl_value_t* %8, %jl_value_t** %3, i32 3),
> !dbg !777
> %15 = load %jl_value_t** %5, align 8, !dbg !777
> %16 = getelementptr inbounds %jl_value_t* %15, i64 0, i32 0, !dbg !777
> store %jl_value_t** %16, %jl_value_t*** @jl_pgcstack, align 8, !dbg !777
> ret void, !dbg !777
> }
>
>
