------- Comment #5 from roger at eyesopen dot com 2006-07-06 19:47 ------- No the rtx_costs for a DImode shift really are wrong. The use of the constant 10000 in sh.c:shift_costs instructs the middle-end to avoid using DImode shifts at all costs. The semantics of rtx_costs is that it is expected to provide an estimate of the cost of performing an instruction (either in size when optimize_size or in performance whrn !optimize_size) even if the hardware doesn't support that operation directly. For example, a backend may even need to provide estimates of the time taken for a libcall to libgcc, if such an operation is necessary, or when optimizing for size, how large such setting up and executing such a call sequence should be.
It's only by providing accurate information such as this that an embedded backend such as SH is able to provide fine control over the code sequences selected by the GCC middle-end. As for the little-endian vs. big-endian issue that looks like a second bug. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28283
