(store_bit_field): If VALUE needs to be narrowed, do

it with gen_lowpart, not an explicit SUBREG.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@2920 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/expmed.c b/gcc/expmed.c
index 5819ce4..2c95a86 100644 (file)
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -402,12 +402,18 @@ store_bit_field (str_rtx, bitsize, bitnum, fieldmode, value, align, total_size)
          if (GET_MODE_BITSIZE (GET_MODE (value)) >= bitsize)
            {
              /* Optimization: Don't bother really extending VALUE
-                if it has all the bits we will actually use.  */
+                if it has all the bits we will actually use.  However,
+                if we must narrow it, be sure we do it correctly.  */
 
-             /* Avoid making subreg of a subreg, or of a mem.  */
-             if (GET_CODE (value1) != REG)
+             if (GET_MODE_SIZE (GET_MODE (value)) < GET_MODE_SIZE (maxmode))
+               {
+                 /* Avoid making subreg of a subreg, or of a mem.  */
+                 if (GET_CODE (value1) != REG)
                value1 = copy_to_reg (value1);
-             value1 = gen_rtx (SUBREG, maxmode, value1, 0);
+                 value1 = gen_rtx (SUBREG, maxmode, value1, 0);
+               }
+             else
+               value1 = gen_lowpart (maxmode, value1);
            }
          else if (!CONSTANT_P (value))
            /* Parse phase is supposed to make VALUE's data type