https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106635
--- Comment #6 from Xiaoguang <xgchenshy at 126 dot com> ---
(In reply to Richard Earnshaw from comment #5)
> Your original code contains (after stripping out the volatile):
> u32 temp_32 = (u32)status_data_base_addr;
> *dst++ = temp_32;
> data_length++;
>
> if(sizeof(addr_t) == 8) {
> *dst++ = (u32)(((u64)status_data_base_addr)>>32);
> data_length++;
> }
>
> Which of course on a 64-bit machine simplifies to
>
> u32 temp_32 = (u32)status_data_base_addr;
> *dst++ = temp_32;
> data_length++;
>
> *dst++ = (u32)(((u64)status_data_base_addr)>>32);
> data_length++;
>
> And which the compiler then further simplifies to
>
> *([unaligned]u64*)dst = status_data_base_addr;
> data_length += 2;
> dst += 2;
>
> If the location that dst points to is in normal, cachable, memory, then this
> will be fine. But if you're writing to non-cachable memory, then you might
> get a trap.
Thanks Very much for the explaination, Can you tell me why unaligned access
only works in normal cachable memory? where does this constraint come from?
>
> the correct fix is to mark dst as volatile in this case.
>
> void CWLCollectReadRegData(volatile u32* dst,u16 reg_start, u32
> reg_length,u32*
> total_length, addr_t status_data_base_addr)
