https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90773
--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
Something like this:
diff --git a/gcc/expr.c b/gcc/expr.c
index c78bc74c0d9..4412aa7518c 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -1090,10 +1090,13 @@ op_by_pieces_d::op_by_pieces_d (rtx to, bool to_load,
void
op_by_pieces_d::run ()
{
+ bool started = false;
+
while (m_max_size > 1 && m_len > 0)
{
scalar_int_mode mode = widest_int_mode_for_size (m_max_size);
+repeat:
if (prepare_mode (mode, m_align))
{
unsigned int size = GET_MODE_SIZE (mode);
@@ -1101,6 +1104,8 @@ op_by_pieces_d::run ()
while (m_len >= size)
{
+ started = true;
+
if (m_reverse)
m_offset -= size;
@@ -1124,6 +1129,24 @@ op_by_pieces_d::run ()
finish_mode (mode);
}
+ if (m_len == 0)
+ break;
+
+ if (started)
+ {
+ mode = smallest_int_mode_for_size (m_len * BITS_PER_UNIT);
+ unsigned int last_gap = GET_MODE_SIZE (mode) - m_len;
+ if (last_gap)
+ {
+ if (m_reverse)
+ m_offset += last_gap;
+ else
+ m_offset -= last_gap;
+ m_len += last_gap;
+ goto repeat;
+ }
+ }
+
m_max_size = GET_MODE_SIZE (mode);
}
which should be opt-in by target.
