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From: "glisse at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/57742] New: memset(malloc(n),0,n) -> calloc(n,1) Date: Thu, 27 Jun 2013 22:28:00 -0000 [thread overview] Message-ID: <bug-57742-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57742 Bug ID: 57742 Summary: memset(malloc(n),0,n) -> calloc(n,1) Product: gcc Version: 4.9.0 Status: UNCONFIRMED Severity: enhancement Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: glisse at gcc dot gnu.org Hello, calloc can sometimes be significantly faster than malloc+bzero because it has special knowledge that some memory is already zero. When other optimizations simplify some code to malloc+memset(0), it would thus be nice to replace it with calloc. Sadly, I don't think there is a way to do a similar optimization in C++ with new, which is where such code most easily appears (creating std::vector<int>(10000) for instance). And there would also be the complication there that the size of the memset would be a bit smaller than that of the malloc (using calloc would still be fine, but it gets harder to know if it is an improvement).
next reply other threads:[~2013-06-27 22:28 UTC|newest] Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-06-27 22:28 glisse at gcc dot gnu.org [this message] 2013-10-11 16:44 ` [Bug tree-optimization/57742] " glisse at gcc dot gnu.org 2013-10-14 8:55 ` rguenth at gcc dot gnu.org 2013-10-14 9:51 ` Joost.VandeVondele at mat dot ethz.ch 2013-10-14 10:07 ` glisse at gcc dot gnu.org 2013-10-14 10:46 ` rguenth at gcc dot gnu.org 2013-10-14 11:48 ` glisse at gcc dot gnu.org 2013-10-14 20:51 ` glisse at gcc dot gnu.org 2013-10-14 20:53 ` glisse at gcc dot gnu.org 2013-10-15 7:57 ` rguenth at gcc dot gnu.org 2013-10-15 14:11 ` glisse at gcc dot gnu.org 2013-10-15 16:38 ` glisse at gcc dot gnu.org 2013-10-16 14:11 ` rguenth at gcc dot gnu.org 2014-02-22 15:44 ` glisse at gcc dot gnu.org 2014-02-23 18:46 ` glisse at gcc dot gnu.org 2014-06-24 19:04 ` glisse at gcc dot gnu.org 2014-06-25 6:46 ` Joost.VandeVondele at mat dot ethz.ch 2014-06-25 7:41 ` Joost.VandeVondele at mat dot ethz.ch 2014-06-25 7:53 ` glisse at gcc dot gnu.org 2014-06-25 8:09 ` glisse at gcc dot gnu.org 2014-06-25 12:27 ` glisse at gcc dot gnu.org 2014-06-25 12:29 ` glisse at gcc dot gnu.org 2015-09-17 19:32 ` daniel.gutson at tallertechnologies dot com
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