https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81356
--- Comment #5 from Qing Zhao <qing.zhao at oracle dot com> ---
the following code in config/aarch64/aarch64.c cause such behavior:
14143 static bool
14144 aarch64_use_by_pieces_infrastructure_p (unsigned HOST_WIDE_INT size,
14145 unsigned int align,
14146 enum by_pieces_operation op,
14147 bool speed_p)
14148 {
14149 /* STORE_BY_PIECES can be used when copying a constant string, but
14150 in that case each 64-bit chunk takes 5 insns instead of 2 (LDR/STR).
14151 For now we always fail this and let the move_by_pieces code copy
14152 the string from read-only memory. */
14153 if (op == STORE_BY_PIECES)
14154 return false;
when deleting line 14153 and 14154. and use this compiler to build the testing
case, I got:
f:
mov w1, 26952
movk w1, 0x21, lsl 16
str w1, [x0]
ret
looks like exactly we want.
