From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolai Stange Subject: [PATCH v2 03/13] expression: examine constness of binops and alike at evaluation only Date: Mon, 25 Jan 2016 15:52:14 +0100 Message-ID: <87h9i1g19d.fsf@gmail.com> References: <87twm1g1go.fsf@gmail.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from mail-wm0-f66.google.com ([74.125.82.66]:36468 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757132AbcAYOwT (ORCPT ); Mon, 25 Jan 2016 09:52:19 -0500 Received: by mail-wm0-f66.google.com with SMTP id l65so11734357wmf.3 for ; Mon, 25 Jan 2016 06:52:18 -0800 (PST) In-Reply-To: <87twm1g1go.fsf@gmail.com> (Nicolai Stange's message of "Mon, 25 Jan 2016 15:47:51 +0100") Sender: linux-sparse-owner@vger.kernel.org List-Id: linux-sparse@vger.kernel.org To: linux-sparse@vger.kernel.org Cc: Nicolai Stange , Christopher Li , Josh Triplett , Luc Van Oostenryck Currently, the propagation of expressions' constness flags through binary operations, compare and logical expressions is done in two steps: - Several flags are speculatively set at expression parsing time - and possibly cleared again at evaluation time. Set aside this unfortunate split of code, the early propagation of constness flags is not able to recognize constant expressions such as 0 + __builtin_choose_expr(0, 0, 0) 0 < __builtin_choose_expr(0, 0, 0) 0 && __builtin_choose_expr(0, 0, 0) since the final expression to be thrown into the binop-like expression is known only after evaluation. Move the whole calculation of binary operations', compare and logical expressions' constness flags to the evaluation phase. Introduce support for tracking arithmetic constness propagation through binop-like expressions. Signed-off-by: Nicolai Stange --- evaluate.c | 25 +++++++++---------------- expression.c | 3 --- validation/constexpr-binop.c | 33 +++++++++++++++++++++++++++++++++ 3 files changed, 42 insertions(+), 19 deletions(-) create mode 100644 validation/constexpr-binop.c diff --git a/evaluate.c b/evaluate.c index 11917ee..5e3e2ca 100644 --- a/evaluate.c +++ b/evaluate.c @@ -878,11 +878,9 @@ static struct symbol *evaluate_logical(struct expression *expr) /* the result is int [6.5.13(3), 6.5.14(3)] */ expr->ctype = &int_ctype; - if (expr->flags) { - if (!(expr->left->flags & expr->right->flags & - EXPR_FLAG_INT_CONST_EXPR)) - expr->flags = EXPR_FLAG_NONE; - } + expr->flags = expr->left->flags & expr->right->flags; + expr_flags_decay_consts(&expr->flags); + expr_clear_flag(&expr->flags, EXPR_FLAG_ADDR_CONST_EXPR); return &int_ctype; } @@ -893,14 +891,11 @@ static struct symbol *evaluate_binop(struct expression *expr) int rclass = classify_type(expr->right->ctype, &rtype); int op = expr->op; - if (expr->flags) { - if (!(expr->left->flags & expr->right->flags & - EXPR_FLAG_INT_CONST_EXPR)) - expr->flags = EXPR_FLAG_NONE; - } - /* number op number */ if (lclass & rclass & TYPE_NUM) { + expr->flags = expr->left->flags & expr->right->flags; + expr_flags_decay_consts(&expr->flags); + if ((lclass | rclass) & TYPE_FLOAT) { switch (op) { case '+': case '-': case '*': case '/': @@ -1001,11 +996,9 @@ static struct symbol *evaluate_compare(struct expression *expr) struct symbol *ctype; const char *typediff; - if (expr->flags) { - if (!(expr->left->flags & expr->right->flags & - EXPR_FLAG_INT_CONST_EXPR)) - expr->flags = EXPR_FLAG_NONE; - } + expr->flags = left->flags & right->flags; + expr_flags_decay_consts(&expr->flags); + expr_clear_flag(&expr->flags, EXPR_FLAG_ADDR_CONST_EXPR); /* Type types? */ if (is_type_type(ltype) && is_type_type(rtype)) diff --git a/expression.c b/expression.c index 33f4581..e49a19d 100644 --- a/expression.c +++ b/expression.c @@ -146,7 +146,6 @@ static struct token *builtin_types_compatible_p_expr(struct token *token, { struct expression *expr = alloc_expression( token->pos, EXPR_COMPARE); - expr_set_flag(&expr->flags, EXPR_FLAG_INT_CONST_EXPR); expr->op = SPECIAL_EQUAL; token = token->next; if (!match_op(token, '(')) @@ -761,8 +760,6 @@ static struct token *cast_expression(struct token *token, struct expression **tr sparse_error(next->pos, "No right hand side of '%s'-expression", show_special(op)); \ break; \ } \ - top->flags = left->flags & right->flags; \ - expr_flags_decay_consts(&top->flags); \ top->op = op; \ top->left = left; \ top->right = right; \ diff --git a/validation/constexpr-binop.c b/validation/constexpr-binop.c new file mode 100644 index 0000000..85a88e3 --- /dev/null +++ b/validation/constexpr-binop.c @@ -0,0 +1,33 @@ +static int a[] = { + [0 + 0] = 0, // OK + [0 + 0.] = 0, // KO + [(void*)0 + 0] = 0, // KO + [0 + __builtin_choose_expr(0, 0, 0)] = 0, // OK + [0 + __builtin_choose_expr(0, 0., 0)] = 0, // OK + [0 + __builtin_choose_expr(0, 0, 0.)] = 0, // KO + [0 < 0] = 0, // OK + [0 < 0.] = 0, // KO + [0 < __builtin_choose_expr(0, 0, 0)] = 0, // OK + [0 < __builtin_choose_expr(0, 0., 0)] = 0, // OK + [0 < __builtin_choose_expr(0, 0, 0.)] = 0, // KO + [0 && 0] = 0, // OK + [0 && 0.] = 0, // KO + [0 && __builtin_choose_expr(0, 0, 0)] = 0, // OK + [0 && __builtin_choose_expr(0, 0., 0)] = 0, // OK + [0 && __builtin_choose_expr(0, 0, 0.)] = 0, // KO + [0 + __builtin_types_compatible_p(int, float)] = 0, // OK +}; + +/* + * check-name: Expression constness propagation in binops and alike + * + * check-error-start +constexpr-binop.c:3:12: error: bad constant expression +constexpr-binop.c:4:19: error: bad integer constant expression +constexpr-binop.c:7:12: error: bad constant expression +constexpr-binop.c:9:12: error: bad integer constant expression +constexpr-binop.c:12:12: error: bad integer constant expression +constexpr-binop.c:14:12: error: bad integer constant expression +constexpr-binop.c:17:12: error: bad integer constant expression + * check-error-end + */ -- 2.7.0