PR rtl-optimization/33796

	* sparseset.c (sparseset_alloc): Use xcalloc rather than xmalloc.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@131589 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 6 insertions, 1 deletions

diff --git a/gcc/sparseset.c b/gcc/sparseset.c
index f556c4dc05c..c8a9a301b59 100644
--- a/gcc/sparseset.c
+++ b/gcc/sparseset.c
@@ -30,7 +30,12 @@ sparseset_alloc (SPARSESET_ELT_TYPE n_elms)
   unsigned int n_bytes = sizeof (struct sparseset_def)
 			 + ((n_elms - 1) * 2 * sizeof (SPARSESET_ELT_TYPE));
 
-  sparseset set = (sparseset) xmalloc (n_bytes);
+  /* We use xcalloc rather than xmalloc to silence some valgrind uninitialized
+     read errors when accessing set->sparse[n] when "n" is not, and never has
+     been, in the set.  These uninitialized reads are expected, by design and
+     harmless.  If this turns into a performance problem due to some future
+     additional users of sparseset, we can revisit this decision.  */
+  sparseset set = (sparseset) xcalloc (1, n_bytes);
   set->dense = &(set->elms[0]);
   set->sparse = &(set->elms[n_elms]);
   set->size = n_elms;