Replace modulus with mask operation in over-aligned new

2016-09-16  Jonathan Wakely  <jwakely@redhat.com>
	    Marc Glisse  <marc.glisse@inria.fr>

	* libsupc++/new_opa.cc [_GLIBCXX_HAVE_ALIGNED_ALLOC]
	(operator new(size_t, align_val_t)): Replace modulus operator with
	mask.

Co-Authored-By: Marc Glisse <marc.glisse@inria.fr>
From-SVN: r240192

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index cddff99..21ee3fd 100644 (file)
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,4 +1,11 @@
 2016-09-16  Jonathan Wakely  <jwakely@redhat.com>
+           Marc Glisse  <marc.glisse@inria.fr>
+
+       * libsupc++/new_opa.cc [_GLIBCXX_HAVE_ALIGNED_ALLOC]
+       (operator new(size_t, align_val_t)): Replace modulus operator with
+       mask.
+
+2016-09-16  Jonathan Wakely  <jwakely@redhat.com>
 
        * libsupc++/new_opa.cc [_GLIBCXX_HAVE_POSIX_MEMALIGN] (aligned_alloc):
        Increase alignment if less than sizeof(void*).

diff --git a/libstdc++-v3/libsupc++/new_opa.cc b/libstdc++-v3/libsupc++/new_opa.cc
index 9c859c1..91e53a8 100644 (file)
--- a/libstdc++-v3/libsupc++/new_opa.cc
+++ b/libstdc++-v3/libsupc++/new_opa.cc
@@ -69,7 +69,7 @@ operator new (std::size_t sz, std::align_val_t al)
 
 #if _GLIBCXX_HAVE_ALIGNED_ALLOC
   /* C11: the value of size shall be an integral multiple of alignment.  */
-  if (std::size_t rem = sz % align)
+  if (std::size_t rem = sz & (align - 1))
     sz += align - rem;
 #endif