PR c++/38410

        * gimplify.c (gimplify_init_constructor): Don't write out a static
        copy of the CONSTRUCTOR for TREE_ADDRESSABLE types or small sparse
        initializers.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@142580 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 31 insertions, 4 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index c43bbde608b..a8b338f59da 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2008-12-09  Jason Merrill  <jason@redhat.com>
+
+	PR c++/38410
+	* gimplify.c (gimplify_init_constructor): Don't write out a static
+	copy of the CONSTRUCTOR for TREE_ADDRESSABLE types or small sparse
+	initializers.
+
 2008-12-09 Tobias Grosser  <grosser@fim.uni-passau.de>
 
 	PR middle-end/38084
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 2fea882811f..01b2fbef6b7 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -3502,7 +3502,7 @@ gimplify_init_constructor (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
 	struct gimplify_init_ctor_preeval_data preeval_data;
 	HOST_WIDE_INT num_type_elements, num_ctor_elements;
 	HOST_WIDE_INT num_nonzero_elements;
-	bool cleared, valid_const_initializer;
+	bool cleared, valid_const_initializer, sparse;
 
 	/* Aggregate types must lower constructors to initialization of
 	   individual elements.  The exception is that a CONSTRUCTOR node
@@ -3558,6 +3558,9 @@ gimplify_init_constructor (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
 
 	num_type_elements = count_type_elements (type, true);
 
+	/* Are there significantly more zeros than non-zeros?  */
+	sparse = (num_nonzero_elements <= num_type_elements/4);
+
 	/* If count_type_elements could not determine number of type elements
 	   for a constant-sized object, assume clearing is needed.
 	   Don't do this for variable-sized objects, as store_constructor
@@ -3567,7 +3570,7 @@ gimplify_init_constructor (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
 	/* If there are "lots" of zeros, then block clear the object first.  */
 	else if (num_type_elements - num_nonzero_elements
 		 > CLEAR_RATIO (optimize_function_for_speed_p (cfun))
-		 && num_nonzero_elements < num_type_elements/4)
+		 && sparse)
 	  cleared = true;
 	/* ??? This bit ought not be needed.  For any element not present
 	   in the initializer, we should simply set them to zero.  Except
@@ -3582,8 +3585,10 @@ gimplify_init_constructor (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
 	   be dropped to memory, and then memcpy'd out.  Don't do this
 	   for sparse arrays, though, as it's more efficient to follow
 	   the standard CONSTRUCTOR behavior of memset followed by
-	   individual element initialization.  */
-	if (valid_const_initializer && !cleared)
+	   individual element initialization.  Also don't try to do
+	   bitwise copies of TREE_ADDRESSABLE types.  */
+	if (valid_const_initializer && !(cleared || sparse)
+	    && !TREE_ADDRESSABLE (type))
 	  {
 	    HOST_WIDE_INT size = int_size_in_bytes (type);
 	    unsigned int align;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 57a14fcdfab..07c5eb0c8ef 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2008-12-08  Jason Merrill  <jason@redhat.com>
+
+	PR c++/38410
+	* gcc.dg/ctor1.c: New test.
+
 2008-12-08  Uros Bizjak  <ubizjak@gmail.com>
 
 	* gcc.target/mips/fix-r10000-6.c: Add dg-message to look for
diff --git a/gcc/testsuite/gcc.dg/ctor1.c b/gcc/testsuite/gcc.dg/ctor1.c
new file mode 100644
index 00000000000..6c1cd72cc77
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ctor1.c
@@ -0,0 +1,10 @@
+/* Related to PR c++/38410.
+   We shouldn't write out a static variable for an all-zero aggregate
+   initializer.  The variable named C.0 was created by
+   gimplify_init_constructor. */
+/* { dg-final { scan-assembler-not "C\\.0" } } */
+
+int main()
+{
+  int a[] = { 0,0 };
+}