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))))))
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
