+/* Copy BLKmode value SRC into a register of mode MODE. Return the
+ register if it contains any data, otherwise return null.
+
+ This is used on targets that return BLKmode values in registers. */
+
+rtx
+copy_blkmode_to_reg (enum machine_mode mode, tree src)
+{
+ int i, n_regs;
+ unsigned HOST_WIDE_INT bitpos, xbitpos, padding_correction = 0, bytes;
+ unsigned int bitsize;
+ rtx *dst_words, dst, x, src_word = NULL_RTX, dst_word = NULL_RTX;
+ enum machine_mode dst_mode;
+
+ gcc_assert (TYPE_MODE (TREE_TYPE (src)) == BLKmode);
+
+ x = expand_normal (src);
+
+ bytes = int_size_in_bytes (TREE_TYPE (src));
+ if (bytes == 0)
+ return NULL_RTX;
+
+ /* If the structure doesn't take up a whole number of words, see
+ whether the register value should be padded on the left or on
+ the right. Set PADDING_CORRECTION to the number of padding
+ bits needed on the left side.
+
+ In most ABIs, the structure will be returned at the least end of
+ the register, which translates to right padding on little-endian
+ targets and left padding on big-endian targets. The opposite
+ holds if the structure is returned at the most significant
+ end of the register. */
+ if (bytes % UNITS_PER_WORD != 0
+ && (targetm.calls.return_in_msb (TREE_TYPE (src))
+ ? !BYTES_BIG_ENDIAN
+ : BYTES_BIG_ENDIAN))
+ padding_correction = (BITS_PER_WORD - ((bytes % UNITS_PER_WORD)
+ * BITS_PER_UNIT));
+
+ n_regs = (bytes + UNITS_PER_WORD - 1) / UNITS_PER_WORD;
+ dst_words = XALLOCAVEC (rtx, n_regs);
+ bitsize = MIN (TYPE_ALIGN (TREE_TYPE (src)), BITS_PER_WORD);
+
+ /* Copy the structure BITSIZE bits at a time. */
+ for (bitpos = 0, xbitpos = padding_correction;
+ bitpos < bytes * BITS_PER_UNIT;
+ bitpos += bitsize, xbitpos += bitsize)
+ {
+ /* We need a new destination pseudo each time xbitpos is
+ on a word boundary and when xbitpos == padding_correction
+ (the first time through). */
+ if (xbitpos % BITS_PER_WORD == 0
+ || xbitpos == padding_correction)
+ {
+ /* Generate an appropriate register. */
+ dst_word = gen_reg_rtx (word_mode);
+ dst_words[xbitpos / BITS_PER_WORD] = dst_word;
+
+ /* Clear the destination before we move anything into it. */
+ emit_move_insn (dst_word, CONST0_RTX (word_mode));
+ }
+
+ /* We need a new source operand each time bitpos is on a word
+ boundary. */
+ if (bitpos % BITS_PER_WORD == 0)
+ src_word = operand_subword_force (x, bitpos / BITS_PER_WORD, BLKmode);
+
+ /* Use bitpos for the source extraction (left justified) and
+ xbitpos for the destination store (right justified). */
+ store_bit_field (dst_word, bitsize, xbitpos % BITS_PER_WORD,
+ 0, 0, word_mode,
+ extract_bit_field (src_word, bitsize,
+ bitpos % BITS_PER_WORD, 1, false,
+ NULL_RTX, word_mode, word_mode));
+ }
+
+ if (mode == BLKmode)
+ {
+ /* Find the smallest integer mode large enough to hold the
+ entire structure. */
+ for (mode = GET_CLASS_NARROWEST_MODE (MODE_INT);
+ mode != VOIDmode;
+ mode = GET_MODE_WIDER_MODE (mode))
+ /* Have we found a large enough mode? */
+ if (GET_MODE_SIZE (mode) >= bytes)
+ break;
+
+ /* A suitable mode should have been found. */
+ gcc_assert (mode != VOIDmode);
+ }
+
+ if (GET_MODE_SIZE (mode) < GET_MODE_SIZE (word_mode))
+ dst_mode = word_mode;
+ else
+ dst_mode = mode;
+ dst = gen_reg_rtx (dst_mode);
+
+ for (i = 0; i < n_regs; i++)
+ emit_move_insn (operand_subword (dst, i, 0, dst_mode), dst_words[i]);
+
+ if (mode != dst_mode)
+ dst = gen_lowpart (mode, dst);
+
+ return dst;
+}
+