On Tue, 18 Jul 2017, Jakub Jelinek wrote:
> Hi!
>
> The following patch implements the:
> /* Optimize (c>=1) && (c<=127) into (signed char)c > 0. */
> if (integer_onep (low) && TREE_CODE (high) == INTEGER_CST)
> {
> int prec = TYPE_PRECISION (etype);
>
> if (wi::mask (prec - 1, false, prec) == high)
> {
> if (TYPE_UNSIGNED (etype))
> {
> tree signed_etype = signed_type_for (etype);
> if (TYPE_PRECISION (signed_etype) != TYPE_PRECISION (etype))
> etype
> = build_nonstandard_integer_type (TYPE_PRECISION (etype),
> 0);
> else
> etype = signed_etype;
> exp = fold_convert_loc (loc, etype, exp);
> }
> return fold_build2_loc (loc, GT_EXPR, type, exp,
> build_int_cst (etype, 0));
> }
> }
> optimization from build_range_check in match.pd if we already have the
> less efficient x-1U <= 127U-1U. If somebody writes the range test
> as x>=1 && x <= 127, then it is already optimized well, but if somebody
> writes it as x-1U <= 126U, then it is not without this patch.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux.
>
> In the PR Marc noted that the optimization might be useful even for
> constants other than 1, by transforming
> x+C1 <= C2 if unsigned and C2-C1==INT_MAX into (int)x > (int)(-1-C1).
> Shall I do that immediately, or incrementally? Shall we also change
> build_range_check to do that (i.e. drop the integer_onep above and use
> right etype constant? Also, I think the build_nonstandard_integer_type
> above is unnecessary, I think signed_type_for does already call that.
Yeah, that's legacy from the times signed_type_for used the langhook.
Let's do any improvements incrementally. I, too, woudln't worry
about enhancing the fold-const.c variant unless proven necessary
by testcases from real-wrold code.
Patch is ok.
Thanks,
Richard.
> 2017-07-18 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/81346
> * match.pd: Optimize (X - 1U) <= INT_MAX-1U into (int) X > 0.
>
> * gcc.dg/tree-ssa/pr81346-5.c: New test.
>
> --- gcc/match.pd.jj 2017-07-17 16:25:20.000000000 +0200
> +++ gcc/match.pd 2017-07-18 12:32:52.896924558 +0200
> @@ -1125,6 +1125,19 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> && wi::neg_p (@1, TYPE_SIGN (TREE_TYPE (@1))))
> (cmp @2 @0))))))
>
> +/* (X - 1U) <= INT_MAX-1U into (int) X > 0. */
> +(for cmp (le gt)
> + icmp (gt le)
> + (simplify
> + (cmp (plus @0 integer_minus_onep@1) INTEGER_CST@2)
> + (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
> + && TYPE_UNSIGNED (TREE_TYPE (@0))
> + && TYPE_PRECISION (TREE_TYPE (@0)) > 1
> + && wi::eq_p (@2, wi::max_value (TYPE_PRECISION (TREE_TYPE (@0)),
> + SIGNED) - 1))
> + (with { tree stype = signed_type_for (TREE_TYPE (@0)); }
> + (icmp (convert:stype @0) { build_int_cst (stype, 0); })))))
> +
> /* X / 4 < Y / 4 iff X < Y when the division is known to be exact. */
> (for cmp (simple_comparison)
> (simplify
> --- gcc/testsuite/gcc.dg/tree-ssa/pr81346-5.c.jj 2017-07-18
> 12:35:27.406063800 +0200
> +++ gcc/testsuite/gcc.dg/tree-ssa/pr81346-5.c 2017-07-18 12:37:04.460894965
> +0200
> @@ -0,0 +1,17 @@
> +/* PR tree-optimization/81346 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +/* { dg-final { scan-tree-dump-times "\\(signed int\\) x" 10 "optimized" } }
> */
> +/* { dg-final { scan-tree-dump-times " <= 0;" 5 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times " > 0;" 5 "optimized" } } */
> +
> +int f1 (unsigned x) { return x - 1 <= __INT_MAX__ - 1; }
> +int f2 (unsigned x) { unsigned a = 1, b = __INT_MAX__ - 1; return x - a <=
> b; }
> +int f3 (unsigned x) { return x - 1 < __INT_MAX__; }
> +int f4 (unsigned x) { unsigned a = 1, b = __INT_MAX__; return x - a < b; }
> +int f5 (unsigned x) { return x >= 1 && x <= __INT_MAX__; }
> +int f6 (unsigned x) { return x - 1 > __INT_MAX__ - 1; }
> +int f7 (unsigned x) { unsigned a = 1, b = __INT_MAX__ - 1; return x - a > b;
> }
> +int f8 (unsigned x) { return x - 1 >= __INT_MAX__; }
> +int f9 (unsigned x) { unsigned a = 1, b = __INT_MAX__; return x - a >= b; }
> +int f10 (unsigned x) { return x < 1 || x > __INT_MAX__; }
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
