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Re: [C++ PATCH] Fix ICEs with #pragma GCC ivdep (PR c++/79379)
- From: Jason Merrill <jason at redhat dot com>
- To: Jakub Jelinek <jakub at redhat dot com>
- Cc: gcc-patches List <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 6 Feb 2017 14:54:22 -0500
- Subject: Re: [C++ PATCH] Fix ICEs with #pragma GCC ivdep (PR c++/79379)
- Authentication-results: sourceware.org; auth=none
- References: <20170206193002.GM1849@tucnak>
OK.
On Mon, Feb 6, 2017 at 2:30 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> #pragma GCC ivdep can make it through into potential_constant_expression_1
> as the following testcase shows. As it is just a hint to the compiler,
> I think it isn't needed to make loops with that pragma non-constexpr, so
> the patch just ignores the hint for determination of what is a potential
> constant expression and ditto in cxx_eval_constant_expression. The pragma
> is represented by ANNOTATE_EXPR with first operand being the condition
> of the loop and second operand annot_expr_ivdep_kind.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2017-02-06 Jakub Jelinek <jakub@redhat.com>
>
> PR c++/79379
> * constexpr.c (cxx_eval_constant_expression): Handle ANNOTATE_EXPR.
> (potential_constant_expression_1): Likewise.
>
> * g++.dg/cpp1y/constexpr-79379.C: New test.
>
> --- gcc/cp/constexpr.c.jj 2017-02-03 23:35:37.000000000 +0100
> +++ gcc/cp/constexpr.c 2017-02-06 16:00:21.903921006 +0100
> @@ -4518,6 +4518,14 @@ cxx_eval_constant_expression (const cons
> *non_constant_p = true;
> return t;
>
> + case ANNOTATE_EXPR:
> + gcc_assert (tree_to_uhwi (TREE_OPERAND (t, 1)) == annot_expr_ivdep_kind);
> + r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0),
> + lval,
> + non_constant_p, overflow_p,
> + jump_target);
> + break;
> +
> default:
> if (STATEMENT_CODE_P (TREE_CODE (t)))
> {
> @@ -5689,6 +5697,10 @@ potential_constant_expression_1 (tree t,
> return false;
> }
>
> + case ANNOTATE_EXPR:
> + gcc_assert (tree_to_uhwi (TREE_OPERAND (t, 1)) == annot_expr_ivdep_kind);
> + return RECUR (TREE_OPERAND (t, 0), rval);
> +
> default:
> if (objc_is_property_ref (t))
> return false;
> --- gcc/testsuite/g++.dg/cpp1y/constexpr-79379.C.jj 2017-02-06 16:09:30.457863715 +0100
> +++ gcc/testsuite/g++.dg/cpp1y/constexpr-79379.C 2017-02-06 16:08:49.000000000 +0100
> @@ -0,0 +1,19 @@
> +// PR c++/79379
> +// { dg-do compile { target c++14 } }
> +// { dg-options "-O2" }
> +
> +template <int N>
> +constexpr int
> +foo (int x)
> +{
> + int q[64] = { 0 }, r = 0;
> +#pragma GCC ivdep
> + for (int i = 0; i < x; ++i)
> + q[i] += 2;
> + for (int i = 0; i < x; ++i)
> + r += q[i];
> + return r + N;
> +}
> +
> +constexpr int a = foo<0> (17);
> +static_assert (a == 34, "");
>
> Jakub