Hi Richard, Thanks so much for your comments.
>> patch.diff >> diff --git a/gcc/config/rs6000/rs6000-string.cc >> b/gcc/config/rs6000/rs6000-string.cc >> index 7f777666ba9..4c9b2cbeefc 100644 >> --- a/gcc/config/rs6000/rs6000-string.cc >> +++ b/gcc/config/rs6000/rs6000-string.cc >> @@ -140,7 +140,9 @@ expand_block_clear (rtx operands[]) >> } >> >> dest = adjust_address (orig_dest, mode, offset); >> - >> + /* Set the alignment of dest to the size of mode in order to >> + avoid unnecessary byte swaps on LE. */ >> + set_mem_align (dest, GET_MODE_SIZE (mode) * BITS_PER_UNIT); > > but the alignment is now wrong which might cause ripple-down > wrong-code effects, no? > > It's probably bad to hide the byte-swapping in the move patterns (I'm > just guessing > you do that) Here I just change the alignment of "dest" which is temporary used for move. The orig_dest is untouched and keep the original alignment. The subsequent insns which use orig_dest are not affected. I am not sure if it causes ripple-down effects. Do you mean the dest might be reused later? But I think the alignment is different even though the mode and offset is the same. Looking forward to your advice. Thanks Gui Haochen
