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From: Jason Merrill <jason@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-2978] c++: reduce redundant TARGET_EXPR Date: Fri, 30 Sep 2022 01:28:30 +0000 (GMT) [thread overview] Message-ID: <20220930012830.B2F1B3857351@sourceware.org> (raw) https://gcc.gnu.org/g:43faf3e5445b571731e52faa1be085ecd0a09323 commit r13-2978-g43faf3e5445b571731e52faa1be085ecd0a09323 Author: Jason Merrill <jason@redhat.com> Date: Tue Sep 20 16:25:42 2022 +0200 c++: reduce redundant TARGET_EXPR An experiment led me to notice that in some cases we were ending up with TARGET_EXPR initialized by TARGET_EXPR, which isn't useful. The target_expr_needs_replace change won't make a difference in most cases, since cp_genericize_init will have already expanded VEC_INIT_EXPR by the time we consider it, but it is correct. gcc/cp/ChangeLog: * cp-gimplify.cc (cp_fold_r) [TARGET_EXPR]: Collapse TARGET_EXPR within TARGET_EXPR. * constexpr.cc (cxx_eval_outermost_constant_expr): Avoid adding redundant TARGET_EXPR. * cp-tree.h (target_expr_needs_replace): VEC_INIT_EXPR doesn't. Diff: --- gcc/cp/cp-tree.h | 3 ++- gcc/cp/constexpr.cc | 4 ++-- gcc/cp/cp-gimplify.cc | 16 +++++++++++++--- 3 files changed, 17 insertions(+), 6 deletions(-) diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h index 3cbcdf726ca..d696fd54a7a 100644 --- a/gcc/cp/cp-tree.h +++ b/gcc/cp/cp-tree.h @@ -5426,7 +5426,8 @@ target_expr_needs_replace (tree t) return false; while (TREE_CODE (init) == COMPOUND_EXPR) init = TREE_OPERAND (init, 1); - return TREE_CODE (init) != AGGR_INIT_EXPR; + return (TREE_CODE (init) != AGGR_INIT_EXPR + && TREE_CODE (init) != VEC_INIT_EXPR); } /* True if EXPR expresses direct-initialization of a TYPE. */ diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index ed41d755269..db7571d7d71 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -8065,8 +8065,8 @@ cxx_eval_outermost_constant_expr (tree t, bool allow_non_constant, if (TREE_CODE (t) == TARGET_EXPR && TARGET_EXPR_INITIAL (t) == r) return t; - else if (TREE_CODE (t) == CONSTRUCTOR) - ; + else if (TREE_CODE (t) == CONSTRUCTOR || TREE_CODE (t) == CALL_EXPR) + /* Don't add a TARGET_EXPR if our argument didn't have one. */; else if (TREE_CODE (t) == TARGET_EXPR && TARGET_EXPR_CLEANUP (t)) r = get_target_expr (r); else diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc index c05be833357..73548888783 100644 --- a/gcc/cp/cp-gimplify.cc +++ b/gcc/cp/cp-gimplify.cc @@ -1084,9 +1084,9 @@ cp_fold_r (tree *stmt_p, int *walk_subtrees, void *data_) } break; - /* These are only for genericize time; they're here rather than in - cp_genericize to avoid problems with the invisible reference - transition. */ + /* cp_genericize_{init,target}_expr are only for genericize time; they're + here rather than in cp_genericize to avoid problems with the invisible + reference transition. */ case INIT_EXPR: if (data->genericize) cp_genericize_init_expr (stmt_p); @@ -1095,6 +1095,16 @@ cp_fold_r (tree *stmt_p, int *walk_subtrees, void *data_) case TARGET_EXPR: if (data->genericize) cp_genericize_target_expr (stmt_p); + + /* Folding might replace e.g. a COND_EXPR with a TARGET_EXPR; in + that case, use it in place of this one. */ + if (tree &init = TARGET_EXPR_INITIAL (stmt)) + { + cp_walk_tree (&init, cp_fold_r, data, NULL); + *walk_subtrees = 0; + if (TREE_CODE (init) == TARGET_EXPR) + *stmt_p = init; + } break; default:
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