Backported from mainline

	2013-11-06  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/58970
	* expr.c (get_bit_range): Handle *offset == NULL_TREE.
	(expand_assignment): If *bitpos is negative, set *offset
	and adjust *bitpos, so that it is not negative.

	* gcc.c-torture/compile/pr58970-1.c: New test.
	* gcc.c-torture/compile/pr58970-2.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_8-branch@204663 138bc75d-0d04-0410-961f-82ee72b054a4

5 files changed, 51 insertions, 7 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1b8fd391a8b..c9e0feee51f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,6 +1,13 @@
 2013-11-11  Jakub Jelinek  <jakub@redhat.com>
 
 	Backported from mainline
+	2013-11-06  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/58970
+	* expr.c (get_bit_range): Handle *offset == NULL_TREE.
+	(expand_assignment): If *bitpos is negative, set *offset
+	and adjust *bitpos, so that it is not negative.
+
 	2013-11-05  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/58997
diff --git a/gcc/expr.c b/gcc/expr.c
index 7e909bc0f5c..785747be8d0 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -4551,19 +4551,19 @@ get_bit_range (unsigned HOST_WIDE_INT *bitstart,
 		- tree_low_cst (DECL_FIELD_BIT_OFFSET (repr), 1));
 
   /* If the adjustment is larger than bitpos, we would have a negative bit
-     position for the lower bound and this may wreak havoc later.  This can
-     occur only if we have a non-null offset, so adjust offset and bitpos
-     to make the lower bound non-negative.  */
+     position for the lower bound and this may wreak havoc later.  Adjust
+     offset and bitpos to make the lower bound non-negative in that case.  */
   if (bitoffset > *bitpos)
     {
       HOST_WIDE_INT adjust = bitoffset - *bitpos;
-
       gcc_assert ((adjust % BITS_PER_UNIT) == 0);
-      gcc_assert (*offset != NULL_TREE);
 
       *bitpos += adjust;
-      *offset
-	= size_binop (MINUS_EXPR, *offset, size_int (adjust / BITS_PER_UNIT));
+      if (*offset == NULL_TREE)
+	*offset = size_int (-adjust / BITS_PER_UNIT);
+      else
+	*offset
+	  = size_binop (MINUS_EXPR, *offset, size_int (adjust / BITS_PER_UNIT));
       *bitstart = 0;
     }
   else
@@ -4698,6 +4698,15 @@ expand_assignment (tree to, tree from, bool nontemporal)
       tem = get_inner_reference (to, &bitsize, &bitpos, &offset, &mode1,
 				 &unsignedp, &volatilep, true);
 
+      /* Make sure bitpos is not negative, it can wreak havoc later.  */
+      if (bitpos < 0)
+	{
+	  gcc_assert (offset == NULL_TREE);
+	  offset = size_int (bitpos >> (BITS_PER_UNIT == 8
+					? 3 : exact_log2 (BITS_PER_UNIT)));
+	  bitpos &= BITS_PER_UNIT - 1;
+	}
+
       if (TREE_CODE (to) == COMPONENT_REF
 	  && DECL_BIT_FIELD_TYPE (TREE_OPERAND (to, 1)))
 	get_bit_range (&bitregion_start, &bitregion_end, to, &bitpos, &offset);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index f50ecc48547..5cef1aff591 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,6 +1,12 @@
 2013-11-11  Jakub Jelinek  <jakub@redhat.com>
 
 	Backported from mainline
+	2013-11-06  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/58970
+	* gcc.c-torture/compile/pr58970-1.c: New test.
+	* gcc.c-torture/compile/pr58970-2.c: New test.
+
 	2013-11-05  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/58997
diff --git a/gcc/testsuite/gcc.c-torture/compile/pr58970-1.c b/gcc/testsuite/gcc.c-torture/compile/pr58970-1.c
new file mode 100644
index 00000000000..45aad2b2e65
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr58970-1.c
@@ -0,0 +1,11 @@
+/* PR middle-end/58970 */
+
+struct T { int b : 1; };
+struct S { struct T t[1]; };
+
+void
+foo (int x, struct S *s)
+{
+  if (x == -1)
+    s->t[x].b = 0;
+}
diff --git a/gcc/testsuite/gcc.c-torture/compile/pr58970-2.c b/gcc/testsuite/gcc.c-torture/compile/pr58970-2.c
new file mode 100644
index 00000000000..3103b31e179
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr58970-2.c
@@ -0,0 +1,11 @@
+/* PR middle-end/58970 */
+
+struct T { char a : 8; char b : 1; };
+struct S { char x; struct T t[1]; };
+
+void
+foo (int x, struct S *s)
+{
+  if (x == -1)
+    s->t[x].b = 0;
+}