On June 11, 2015 10:09:11 PM GMT+02:00, Marc Glisse <marc.gli...@inria.fr>
wrote:
>On Thu, 11 Jun 2015, Marek Polacek wrote:
>
>> On Thu, Jun 11, 2015 at 01:09:05PM +0200, Jakub Jelinek wrote:
>>> What about some nop type conversions in between?
>>> int
>>> fn1 (unsigned int x, unsigned int y)
>>> {
>>> int a = x;
>>> int b = y;
>>> unsigned int c = x & y;
>>> int d = a | b;
>>> return (int) (c ^ d);
>>> }
>>> ? Also wonder, if some testcases for match.pd shouldn't be
>>
>> It doesn't work then. Adding some convert?s into the pattern didn't
>help
>> either.
>
>Not judging at all whether it is desirable or not, but you might have
>hit
>the issue that when you want several convert?, you need to use the
>spelling convert1?, convert2?, and it stops there, while here you would
>
>probably want at least 4 (maybe 6?) for this case. You might be able to
>
>work around it with a user-defined predicate, but I keep getting errors
>
>like
>generic-match.c:6655:16: error: redeclaration of ‘tree_node* o20_pops
>[2]’
>
>If you want to reproduce the error (this is probably not good as is, it
>is
>only provided as a reproducer)
>
>(match (nopand @0 @1)
> (bit_and (convert1? @0) (convert2? @1))
> (if (tree_nop_conversion_p (type, TREE_TYPE (@0))
> && tree_nop_conversion_p (type, TREE_TYPE (@1)))))
>(match (nopior @0 @1)
> (bit_ior (convert1? @0) (convert2? @1))
> (if (tree_nop_conversion_p (type, TREE_TYPE (@0))
> && tree_nop_conversion_p (type, TREE_TYPE (@1)))))
>(simplify
> (bit_xor:c (convert1? (nopand@2 @0 @1))
> (convert2? (nopior@3 @0 @1)))
> (if (tree_nop_conversion_p (type, TREE_TYPE (@2))
> && tree_nop_conversion_p (type, TREE_TYPE (@3)))
> (bit_xor (convert @0) (convert @1))))
>
>
>fold-const.c traditionally avoided the combinatorial explosion by using
>
>strip_nops.
Yeah. We can probably special case conditional conversions in code generation
instead of lowering it. And then go the full way and special case nop
conversions so you can avoid writing the predicate as well.
Richard.
