* C++ PATCH for c++/56481 (time hog with repeated &&)
@ 2013-02-28 20:21 Jason Merrill
2013-03-17 1:34 ` Jason Merrill
0 siblings, 1 reply; 2+ messages in thread
From: Jason Merrill @ 2013-02-28 20:21 UTC (permalink / raw)
To: gcc-patches List
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The problem with this testcase was that for a repeated &&, each call of
potential_constant_expression_1 led to two calls for the LHS, giving it
O(N^2) complexity. Fixed by avoiding the redundant call in
maybe_constant_value by calling cxx_eval_outermost_constant_expr directly.
Tested x86_64-pc-linux-gnu, applying to trunk.
[-- Attachment #2: 56481.patch --]
[-- Type: text/x-patch, Size: 2174 bytes --]
commit 001c03d979ea1aaa9bc9565f2b9c82371cc481f1
Author: Jason Merrill <jason@redhat.com>
Date: Thu Feb 28 12:30:40 2013 -0500
PR c++/56481
* semantics.c (potential_constant_expression_1): Use
cxx_eval_outermost_constant_expr rather than maybe_constant_value.
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 9446f83..8038aa2 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -8683,10 +8683,12 @@ potential_constant_expression_1 (tree t, bool want_rval, tsubst_flags_t flags)
case ROUND_MOD_EXPR:
{
tree denom = TREE_OPERAND (t, 1);
- /* We can't call maybe_constant_value on an expression
+ if (!potential_constant_expression_1 (denom, rval, flags))
+ return false;
+ /* We can't call cxx_eval_outermost_constant_expr on an expression
that hasn't been through fold_non_dependent_expr yet. */
if (!processing_template_decl)
- denom = maybe_constant_value (denom);
+ denom = cxx_eval_outermost_constant_expr (denom, true);
if (integer_zerop (denom))
{
if (flags & tf_error)
@@ -8696,7 +8698,8 @@ potential_constant_expression_1 (tree t, bool want_rval, tsubst_flags_t flags)
else
{
want_rval = true;
- goto binary;
+ return potential_constant_expression_1 (TREE_OPERAND (t, 0),
+ want_rval, flags);
}
}
@@ -8731,7 +8734,7 @@ potential_constant_expression_1 (tree t, bool want_rval, tsubst_flags_t flags)
if (!potential_constant_expression_1 (op, rval, flags))
return false;
if (!processing_template_decl)
- op = maybe_constant_value (op);
+ op = cxx_eval_outermost_constant_expr (op, true);
if (tree_int_cst_equal (op, tmp))
return potential_constant_expression_1 (TREE_OPERAND (t, 1), rval, flags);
else
@@ -8793,7 +8796,7 @@ potential_constant_expression_1 (tree t, bool want_rval, tsubst_flags_t flags)
if (!potential_constant_expression_1 (tmp, rval, flags))
return false;
if (!processing_template_decl)
- tmp = maybe_constant_value (tmp);
+ tmp = cxx_eval_outermost_constant_expr (tmp, true);
if (integer_zerop (tmp))
return potential_constant_expression_1 (TREE_OPERAND (t, 2),
want_rval, flags);
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: C++ PATCH for c++/56481 (time hog with repeated &&)
2013-02-28 20:21 C++ PATCH for c++/56481 (time hog with repeated &&) Jason Merrill
@ 2013-03-17 1:34 ` Jason Merrill
0 siblings, 0 replies; 2+ messages in thread
From: Jason Merrill @ 2013-03-17 1:34 UTC (permalink / raw)
To: gcc-patches List
[-- Attachment #1: Type: text/plain, Size: 166 bytes --]
It is also the case that using 'this' in a non-constexpr function should
prevent the expression from being constant.
Tested x86_64-pc-linux-gnu, applying to trunk.
[-- Attachment #2: 56481-2.patch --]
[-- Type: text/x-patch, Size: 897 bytes --]
commit e0f26a1998f2cb404e58bcf8a9f22e29401312e0
Author: Jason Merrill <jason@redhat.com>
Date: Thu Feb 28 11:58:44 2013 -0500
PR c++/56481
* semantics.c (potential_constant_expression_1): Use of 'this' in
a non-constexpr function makes the expression not potentially
constant.
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 1cf060e..9d2f3f4 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -8497,6 +8497,13 @@ potential_constant_expression_1 (tree t, bool want_rval, tsubst_flags_t flags)
STRIP_NOPS (x);
if (is_this_parameter (x))
{
+ if (DECL_CONTEXT (x)
+ && !DECL_DECLARED_CONSTEXPR_P (DECL_CONTEXT (x)))
+ {
+ if (flags & tf_error)
+ error ("use of %<this%> in a constant expression");
+ return false;
+ }
if (want_rval && DECL_CONTEXT (x)
&& DECL_CONSTRUCTOR_P (DECL_CONTEXT (x)))
{
^ permalink raw reply [flat|nested] 2+ messages in thread
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