isha Kandaswamy <isha.kandaswamy@xxxxxxxxx> writes: > When I was compiling gcc 4.4.2 for a certain machine description, I realized > that it needed a nop pattern in the md. This was being called by cfglayout.c > in the function fixup_reorder_chain. This call was not made in the previous > version of gcc I was using namely gcc-4.3.1. My doubt is whay do we need the > nop pattern in gcc-4.4.2 and not in gcc-4.3.1. I also have another doubt. > What does the function copy_to_reg do? Why does it require a movsi pattern > in the machine descriptions ? I've Bcc'ed almost everybody. Please don't send messages to a huge group of people like this. Please don't send messages to both gcc@xxxxxxxxxxx and gcc-patches@xxxxxxxxxxxx Thanks. New versions of gcc impose new requirements on backends. That's just the way it works. The gen_nop call in cfglayout.c is to improve debuggability of code compiled with -O0, by giving debuggers a place to set a breakpoint on an edge which otherwise contains no instructions. The copy_to_reg function copies a value into a register. It requires a movMM insn where MM is the mode of the value. In general a gcc backend must have a movMM insn for all supported modes. Ian
