Fix C++0x memory model for unaligned fields in packed...

2013-12-02  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        Fix C++0x memory model for unaligned fields in packed, aligned(4)
        structures with -fno-strict-volatile-bitfields on STRICT_ALIGNMENT
        targets like arm-none-eabi.
        * expr.c (expand_assignment): Handle normal fields like bit regions.

testsuite:
2013-12-02  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * gcc.dg/pr56997-4.c: New testcase.

From-SVN: r205597

1 files changed, 11 insertions, 0 deletions

diff --git a/gcc/expr.c b/gcc/expr.c
index aeff2ca..c0539da 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -4824,6 +4824,17 @@ expand_assignment (tree to, tree from, bool nontemporal)
       if (TREE_CODE (to) == COMPONENT_REF
 	  && DECL_BIT_FIELD_TYPE (TREE_OPERAND (to, 1)))
 	get_bit_range (&bitregion_start, &bitregion_end, to, &bitpos, &offset);
+      /* The C++ memory model naturally applies to byte-aligned fields.
+	 However, if we do not have a DECL_BIT_FIELD_TYPE but BITPOS or
+	 BITSIZE are not byte-aligned, there is no need to limit the range
+	 we can access.  This can occur with packed structures in Ada.  */
+      else if (bitsize > 0
+	       && bitsize % BITS_PER_UNIT == 0
+	       && bitpos % BITS_PER_UNIT == 0)
+	{
+	  bitregion_start = bitpos;
+	  bitregion_end = bitpos + bitsize - 1;
+	}
 
       to_rtx = expand_expr (tem, NULL_RTX, VOIDmode, EXPAND_WRITE);