This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: define_split


Quoting Ian Lance Taylor <iant@google.com>:

That said, this is not a very interesting use of splits these days and
it could probably be removed without doing any noticeable harm.  These
days most people just write the complex pattern using define_insn, and
then write a define_split (or a define_insn_and_split) which splits up
the insn just before register allocation or just before instruction
scheduling.

Although such patterns are justified in some cases, adding them willy-nilly can make your port worse, if such patterns that need to be split into multiple insns are generated by rtl passes from simpler instructions to increase the total instruction count after splitting, or when they hide scheduling opportunities.

combine-split patterns are still the pattern of choice when you want to
prevent the whole pattern tfrom being considered a single instruction.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]