Strictness in data declaration not matched in assembler?

[Lennart Augustsson]

I totally agree.  Getting the value of the field should just evaluate
x and then use a pointer indirection; there should be no conditional
jumps involved in getting the value.
GHC is just doing the wrong thing.

  -- Lennart

On Wed, Oct 15, 2008 at 3:58 PM, Tyson Whitehead <twhitehead at gmail.com> wrote:
> On Wednesday 15 October 2008 10:48:26 you wrote:
>> Strictness does not imply unboxing.
>>
>> To see why not, think about the fact that unboxing breaks sharing. By
>> keeping the pointer-indirection in place, we can share even strict
>> fields between related values.
>
> I believe I realize that.  What I was wondering about was the fact that it
> seemed to think the pointer might be to a thunk (instead of constructor
> closure).  Doesn't the strictness flag mean the following assembler would work
>
> sni_info:
>        movq 7(%rbx),%rbx
>        movq $snj_info,(%rbp)
>        jmp snj_info
>
> (which could be cleaned up further by combining it with snj_info) instead of
>
> sni_info:
>        movq 7(%rbx),%rbx
>        movq $snj_info,(%rbp)
>        testq $7,%rbx
>        jne snj_info
>        jmp *(%rbx)
>
> (i.e., the whole test if it is a thunk and conditionally evaluate it bit is
> unnecessary due to constructor the strictness flag).
>
> Cheers!  -Tyson
> _______________________________________________
> Glasgow-haskell-users mailing list
> Glasgow-haskell-users at haskell.org
> http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
>