I'm trying to cut my teeth on DMD hacking with a simple optimization ( http://d.puremagic.com/issues/show_bug.cgi?id=9477 ), but not having much luck so far - the backend is rejecting my attempts with asserts here or there. Since the asserts have no error messages, and the code is very terse, often un-straightforward and lacking in comments, I have no idea if I'm feeding it bad input or if it's some latent bug.

Here's my work so far:
https://github.com/CyberShadow/dmd/compare/fix9477-work

Could a DMD guru have a look and tell me what I'm doing wrong?

Tests:
https://gist.github.com/CyberShadow/5177509

What do the lines el_combine? I do not see them in the code structure comparison.

On Saturday, 16 March 2013 at 21:15:32 UTC, Igor Stepanov wrote:
> What do the lines el_combine? I do not see them in the code structure comparison.

Greetings Igor,

The el_combine calls are supposed to ensure correct order of evaluation.

I based that code from this fragment:

https://github.com/D-Programming-Language/dmd/blob/635c6b07/src/e2ir.c#L2702

On Saturday, 16 March 2013 at 21:21:51 UTC, Vladimir Panteleev wrote:
> On Saturday, 16 March 2013 at 21:15:32 UTC, Igor Stepanov wrote:
>> What do the lines el_combine? I do not see them in the code structure comparison.
>
> Greetings Igor,
>
> The el_combine calls are supposed to ensure correct order of evaluation.
>
> I based that code from this fragment:
>
> https://github.com/D-Programming-Language/dmd/blob/635c6b07/src/e2ir.c#L2702

Visually, it should work :)
I would try to make sure that the various components of expression are correctly calculated. In particular, I am concerned the calculation of the length of a dynamic array. You can try to do so, that would return the length of the entire expression.
/ ***** In DMD ***** /
if (t1->ty == Tarray)
{
  retrun el_una(I64 ? OP128_64 : OP64_32, TYsize_t, el_same(&earr1));
}
/ ***** In D ***** /
int[] arr = [1,2,3];
int[] arr3 = [1,2,3,4,5];
size_t len = cast(size_t)(arr == arr3);
assert(len == arr.length);

On Saturday, 16 March 2013 at 21:42:31 UTC, Igor Stepanov wrote:
> On Saturday, 16 March 2013 at 21:21:51 UTC, Vladimir Panteleev wrote:
>> On Saturday, 16 March 2013 at 21:15:32 UTC, Igor Stepanov wrote:
>>> What do the lines el_combine? I do not see them in the code structure comparison.
>>
>> Greetings Igor,
>>
>> The el_combine calls are supposed to ensure correct order of evaluation.
>>
>> I based that code from this fragment:
>>
>> https://github.com/D-Programming-Language/dmd/blob/635c6b07/src/e2ir.c#L2702
>
> Visually, it should work :)
> I would try to make sure that the various components of expression are correctly calculated. In particular, I am concerned the calculation of the length of a dynamic array. You can try to do so, that would return the length of the entire expression.
> / ***** In DMD ***** /
> if (t1->ty == Tarray)
> {
>   retrun el_una(I64 ? OP128_64 : OP64_32, TYsize_t, el_same(&earr1));
> }
> / ***** In D ***** /
> int[] arr = [1,2,3];
> int[] arr3 = [1,2,3,4,5];
> size_t len = cast(size_t)(arr == arr3);
> assert(len == arr.length);

Dynamic arrays work perfectly, it's the static ones I'm having trouble with... particularly, when they're being returned from a function.

From what I can tell, the situation is that I can neither copy them using el_same (it neither makes sense, as the arrays can be large, nor does the compiler let me to), nor can I take their address, because the code generator fails to process an OPaddr elem when its child is a function call. However, the same thing seems to work when calling the runtime function for array equality (the current implementation)...

On Saturday, 16 March 2013 at 21:49:33 UTC, Vladimir Panteleev wrote:
> On Saturday, 16 March 2013 at 21:42:31 UTC, Igor Stepanov wrote:
>> On Saturday, 16 March 2013 at 21:21:51 UTC, Vladimir Panteleev wrote:
>>> On Saturday, 16 March 2013 at 21:15:32 UTC, Igor Stepanov wrote:
>>>> What do the lines el_combine? I do not see them in the code structure comparison.
>>>
>>> Greetings Igor,
>>>
>>> The el_combine calls are supposed to ensure correct order of evaluation.
>>>
>>> I based that code from this fragment:
>>>
>>> https://github.com/D-Programming-Language/dmd/blob/635c6b07/src/e2ir.c#L2702
>>
>> Visually, it should work :)
>> I would try to make sure that the various components of expression are correctly calculated. In particular, I am concerned the calculation of the length of a dynamic array. You can try to do so, that would return the length of the entire expression.
>> / ***** In DMD ***** /
>> if (t1->ty == Tarray)
>> {
>>  retrun el_una(I64 ? OP128_64 : OP64_32, TYsize_t, el_same(&earr1));
>> }
>> / ***** In D ***** /
>> int[] arr = [1,2,3];
>> int[] arr3 = [1,2,3,4,5];
>> size_t len = cast(size_t)(arr == arr3);
>> assert(len == arr.length);
>
> Dynamic arrays work perfectly, it's the static ones I'm having trouble with... particularly, when they're being returned from a function.
>
> From what I can tell, the situation is that I can neither copy them using el_same (it neither makes sense, as the arrays can be large, nor does the compiler let me to), nor can I take their address, because the code generator fails to process an OPaddr elem when its child is a function call. However, the same thing seems to work when calling the runtime function for array equality (the current implementation)...

Probably a stupid question, but why do you want to use el_same? As I understand it, el_same creates a copy. Why not use the original, if we know that it will not change anything.

On Saturday, 16 March 2013 at 22:14:22 UTC, Igor Stepanov wrote:
> Probably a stupid question, but why do you want to use el_same? As I understand it, el_same creates a copy. Why not use the original, if we know that it will not change anything.

As I understand, one "elem" can appear only once in the backend tree. When I tried otherwise, I got asserts in the optimizer, and I've never seen code that reuses elem nodes.

"Vladimir Panteleev" <vladimir@thecybershadow.net> wrote in message news:pzqxkiigdvvicqkqahpn@forum.dlang.org...
> I'm trying to cut my teeth on DMD hacking with a simple optimization ( http://d.puremagic.com/issues/show_bug.cgi?id=9477 ), but not having much luck so far - the backend is rejecting my attempts with asserts here or there. Since the asserts have no error messages, and the code is very terse, often un-straightforward and lacking in comments, I have no idea if I'm feeding it bad input or if it's some latent bug.
>
> Here's my work so far: https://github.com/CyberShadow/dmd/compare/fix9477-work
>
> Could a DMD guru have a look and tell me what I'm doing wrong?
>
> Tests:
> https://gist.github.com/CyberShadow/5177509

Instead of copying elems, try to generate something like this:

(auto tmp1 = e1, auto tmp2 = e2, tmp1.length == tmp2.length && !memcmp(tmp1.ptr, tmp2.ptr))

There is code in e2ir that already does stuff like this.

Not really the easiest part of dmd to hack on....

On Sunday, 17 March 2013 at 02:35:30 UTC, Daniel Murphy wrote:
> "Vladimir Panteleev" <vladimir@thecybershadow.net> wrote in message
> news:pzqxkiigdvvicqkqahpn@forum.dlang.org...
>> I'm trying to cut my teeth on DMD hacking with a simple optimization ( http://d.puremagic.com/issues/show_bug.cgi?id=9477 ), but not having much luck so far - the backend is rejecting my attempts with asserts here or there. Since the asserts have no error messages, and the code is very terse, often un-straightforward and lacking in comments, I have no idea if I'm feeding it bad input or if it's some latent bug.
>>
>> Here's my work so far:
>> https://github.com/CyberShadow/dmd/compare/fix9477-work
>>
>> Could a DMD guru have a look and tell me what I'm doing wrong?
>>
>> Tests:
>> https://gist.github.com/CyberShadow/5177509
>
> Instead of copying elems, try to generate something like this:
>
> (auto tmp1 = e1, auto tmp2 = e2, tmp1.length == tmp2.length &&
> !memcmp(tmp1.ptr, tmp2.ptr))

That's pretty much what my first attempt was. It asserts when I try to save a temporary copy of a static array. Also, it is undesirable if the array happens to be large...

On Saturday, 16 March 2013 at 18:15:06 UTC, Vladimir Panteleev wrote:
> Could a DMD guru have a look and tell me what I'm doing wrong?

Gaaah! My test program doesn't compile even without my patches!

I was fighting against pre-existing bugs in DMD...

Even more embarrassing, is that I had found and filed this bug myself:
http://d.puremagic.com/issues/show_bug.cgi?id=9402