Re: redundant divmodsi4 not optimized away

[Ian Lance Taylor <iant at google dot com>]

Greg McGary <greg@mcgary.org> writes:

> I have a port without div or mod machine instructions.  I wrote
> divmodsi4 patterns that do the libcall directly, hoping that GCC would
> recognize the opportunity to use a single divmodsi4 to compute both
> quotient and remainder.  Alas, GCC calls divmodsi4 twice with the same
> divisor and dividend operands.  Is this supposed to work?  Is there a
> special trick to help the optimizer recognize the redundant insn?  I
> saw the 4yr-old thread regarding picochip's desire for the same effect
> and followed the same approach implemented in the current picochip.md
> (as well as my own approach) but no luck.

Using a divmodsi4 insn instead of divsi3/modsi3 insns ought to work.
You may need to give more information, such as the test case you are
using, and what your divmodsi4 insn looks like.

Ian