public inbox for gcc-cvs@sourceware.org help / color / mirror / Atom feed
From: Jakub Jelinek <jakub@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-3438] c++: Don't shortcut TREE_CONSTANT vector type CONSTRUCTORs in cxx_eval_constant_expression [PR107295 Date: Fri, 21 Oct 2022 16:07:52 +0000 (GMT) [thread overview] Message-ID: <20221021160752.EAFBD3856DC0@sourceware.org> (raw) https://gcc.gnu.org/g:2cc41601d9a948e8d612a21c3b9a44ce0b977747 commit r13-3438-g2cc41601d9a948e8d612a21c3b9a44ce0b977747 Author: Jakub Jelinek <jakub@redhat.com> Date: Fri Oct 21 18:04:54 2022 +0200 c++: Don't shortcut TREE_CONSTANT vector type CONSTRUCTORs in cxx_eval_constant_expression [PR107295] The excess precision support broke building skia (dependency of firefox) on ia32 (it has something like the a constexpr variable), but as the other cases show, it is actually a preexisting problem if one uses casts from constants with wider floating point types. The problem is that cxx_eval_constant_expression tries to short-cut processing of TREE_CONSTANT CONSTRUCTORs if they satisfy reduced_constant_expression_p - instead of calling cxx_eval_bare_aggregate on them it just verifies flags and if they are TREE_CONSTANT even after that, just fold. Now, on the testcase we have a TREE_CONSTANT CONSTRUCTOR containing TREE_CONSTANT NOP_EXPR of REAL_CST. And, fold, which isn't recursive, doesn't optimize that into VECTOR_CST, while later on we are only able to optimize VECTOR_CST arithmetics, not arithmetics with vector CONSTRUCTORs. The following patch fixes that by rejecting CONSTRUCTORs with vector type in reduced_constant_expression_p regardless of whether they have CONSTRUCTOR_NO_CLEARING set or not, folding result in cxx_eval_bare_aggregate even if nothing has changed but it wasn't non-constant and removing folding from the TREE_CONSTANT reduced_constant_expression_p short-cut. 2022-10-21 Jakub Jelinek <jakub@redhat.com> PR c++/107295 * constexpr.cc (reduced_constant_expression_p) <case CONSTRUCTOR>: Return false for VECTOR_TYPE CONSTRUCTORs even without CONSTRUCTOR_NO_CLEARING set on them. (cxx_eval_bare_aggregate): If constant but !changed, fold before returning VECTOR_TYPE_P CONSTRUCTOR. (cxx_eval_constant_expression) <case CONSTRUCTOR>: Don't fold TREE_CONSTANT CONSTRUCTOR, just return it. * g++.dg/ext/vector42.C: New test. Diff: --- gcc/cp/constexpr.cc | 21 +++++++++++++-------- gcc/testsuite/g++.dg/ext/vector42.C | 12 ++++++++++++ 2 files changed, 25 insertions(+), 8 deletions(-) diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index 03663961bb8..c3ee970a724 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -3104,12 +3104,12 @@ reduced_constant_expression_p (tree t) case CONSTRUCTOR: /* And we need to handle PTRMEM_CST wrapped in a CONSTRUCTOR. */ tree field; + if (TREE_CODE (TREE_TYPE (t)) == VECTOR_TYPE) + /* An initialized vector would have a VECTOR_CST. */ + return false; if (CONSTRUCTOR_NO_CLEARING (t)) { - if (TREE_CODE (TREE_TYPE (t)) == VECTOR_TYPE) - /* An initialized vector would have a VECTOR_CST. */ - return false; - else if (TREE_CODE (TREE_TYPE (t)) == ARRAY_TYPE) + if (TREE_CODE (TREE_TYPE (t)) == ARRAY_TYPE) { /* There must be a valid constant initializer at every array index. */ @@ -4956,8 +4956,14 @@ cxx_eval_bare_aggregate (const constexpr_ctx *ctx, tree t, TREE_SIDE_EFFECTS (ctx->ctor) = side_effects_p; } } - if (*non_constant_p || !changed) + if (*non_constant_p) return t; + if (!changed) + { + if (VECTOR_TYPE_P (type)) + t = fold (t); + return t; + } t = ctx->ctor; if (!t) t = build_constructor (type, NULL); @@ -7387,11 +7393,10 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t, case CONSTRUCTOR: if (TREE_CONSTANT (t) && reduced_constant_expression_p (t)) { - /* Don't re-process a constant CONSTRUCTOR, but do fold it to - VECTOR_CST if applicable. */ + /* Don't re-process a constant CONSTRUCTOR. */ verify_constructor_flags (t); if (TREE_CONSTANT (t)) - return fold (t); + return t; } r = cxx_eval_bare_aggregate (ctx, t, lval, non_constant_p, overflow_p); diff --git a/gcc/testsuite/g++.dg/ext/vector42.C b/gcc/testsuite/g++.dg/ext/vector42.C new file mode 100644 index 00000000000..e7810971ca1 --- /dev/null +++ b/gcc/testsuite/g++.dg/ext/vector42.C @@ -0,0 +1,12 @@ +// PR c++/107295 +// { dg-do compile { target c++11 } } + +template <typename T> struct A { + typedef T __attribute__((vector_size (sizeof (int)))) V; +}; +template <int, typename T> using B = typename A<T>::V; +template <typename T> using V = B<4, T>; +using F = V<float>; +constexpr F a = F () + 0.0f; +constexpr F b = F () + (float) 0.0; +constexpr F c = F () + (float) 0.0L;
reply other threads:[~2022-10-21 16:07 UTC|newest] Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20221021160752.EAFBD3856DC0@sourceware.org \ --to=jakub@gcc.gnu.org \ --cc=gcc-cvs@gcc.gnu.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).