On Fri, Jun 4, 2021 at 4:18 PM Marc Glisse <marc.gli...@inria.fr> wrote:
>
> On Fri, 4 Jun 2021, Hongtao Liu via Gcc-patches wrote:
>
> > On Tue, Jun 1, 2021 at 6:17 PM Marc Glisse <marc.gli...@inria.fr> wrote:
> >>
> >> On Tue, 1 Jun 2021, Hongtao Liu via Gcc-patches wrote:
> >>
> >>> Hi:
> >>> This patch is about to simplify (view_convert:type ~a) < 0 to
> >>> (view_convert:type a) >= 0 when type is signed integer. Similar for
> >>> (view_convert:type ~a) >= 0.
> >>> Bootstrapped and regtested on x86_64-linux-gnu{-m32,}.
> >>> Ok for the trunk?
> >>>
> >>> gcc/ChangeLog:
> >>>
> >>> PR middle-end/100738
> >>> * match.pd ((view_convert ~a) < 0 --> (view_convert a) >= 0,
> >>> (view_convert ~a) >= 0 --> (view_convert a) < 0): New GIMPLE
> >>> simplification.
> >>
> >> We already have
> >>
> >> /* Fold ~X op C as X op' ~C, where op' is the swapped comparison. */
> >> (for cmp (simple_comparison)
> >> scmp (swapped_simple_comparison)
> >> (simplify
> >> (cmp (bit_not@2 @0) CONSTANT_CLASS_P@1)
> >> (if (single_use (@2)
> >> && (TREE_CODE (@1) == INTEGER_CST || TREE_CODE (@1) == VECTOR_CST))
> >> (scmp @0 (bit_not @1)))))
> >>
> >> Would it make sense to try and generalize it a bit, say with
> >>
> >> (cmp (nop_convert1? (bit_not @0)) CONSTANT_CLASS_P)
> >>
> >> (scmp (view_convert:XXX @0) (bit_not @1))
> >>
> > Thanks for your advice, it looks great.
> > And can I use *view_convert1?* instead of *nop_convert1?* here,
> > because the original case is view_convert, and nop_convert would fail
> > to simplify the case.
>
> Near the top of match.pd, you can see
>
> /* With nop_convert? combine convert? and view_convert? in one pattern
> plus conditionalize on tree_nop_conversion_p conversions. */
> (match (nop_convert @0)
> (convert @0)
> (if (tree_nop_conversion_p (type, TREE_TYPE (@0)))))
> (match (nop_convert @0)
> (view_convert @0)
> (if (VECTOR_TYPE_P (type) && VECTOR_TYPE_P (TREE_TYPE (@0))
> && known_eq (TYPE_VECTOR_SUBPARTS (type),
> TYPE_VECTOR_SUBPARTS (TREE_TYPE (@0)))
> && tree_nop_conversion_p (TREE_TYPE (type), TREE_TYPE (TREE_TYPE
> (@0))))))
>
Oh, it's restricted to the same number of elements which is not the
case i tested.
That's why nop_convert failed to simplify the case.
Guess we can define another nop1_convert to handle vector types with
different number of elements, but still tree_nop_convertion_p?
> So at least the intention is that it can handle both NOP_EXPR for scalars
> and VIEW_CONVERT_EXPR for vectors, and I think we alread use it that way
> in some places in match.pd, like
>
> (simplify
> (negate (nop_convert? (bit_not @0)))
> (plus (view_convert @0) { build_each_one_cst (type); }))
>
> (simplify
> (bit_xor:c (nop_convert?:s (bit_not:s @0)) @1)
> (if (tree_nop_conversion_p (type, TREE_TYPE (@0)))
> (bit_not (bit_xor (view_convert @0) @1))))
>
> (the 'if' seems redundant for this one)
>
> (simplify
> (negate (nop_convert? (negate @1)))
> (if (!TYPE_OVERFLOW_SANITIZED (type)
> && !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@1)))
> (view_convert @1)))
>
> etc.
>
>
> At some point this got some genmatch help, to handle '?' and numbers, so I
> don't remember all the details, but following these examples should work.
>
> --
> Marc Glisse
--
BR,
Hongtao
