This is the mail archive of the
mailing list for the GCC project.
Re: [patch] Fix PR rtl-optimization/87727
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Eric Botcazou <ebotcazou at adacore dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 20 Dec 2018 13:15:53 +0100
- Subject: Re: [patch] Fix PR rtl-optimization/87727
- References: <3499484.ePniFpkjG6@polaris>
On Thu, Dec 20, 2018 at 12:43 PM Eric Botcazou <email@example.com> wrote:
> this is a regression introduced on the SPARC by the somewhat controversial
> combiner change for hard registers: the compiler can no longer apply the leaf
> registers optimization to a small function so a register window is now used.
> The combiner change might be an overall win, but my understanding is that it's
> dependent on the target and SPARC seems to be in the wrong basket: almost all
> changes to the gcc.c-torture/compile testsuite at -O2 are pessimizations in
> the form of additional move instructions between registers on function entry.
> Clearly that's counter-productive for a LEAF_REGISTERS target like SPARC so
> the proposed fix is to re-enable hard register combining for leaf registers.
> Tested on SPARC/Solaris 11, OK for the mainline?
This only affects xtensa besides sparc so unless Segher objects this is OK.
Does this solve most of the pessimizations?
Please add a testcase if it doesn't solve existing FAILs.
> 2018-12-20 Eric Botcazou <firstname.lastname@example.org>
> PR rtl-optimization/87727
> * combine.c (cant_combine_insn_p): On a LEAF_REGISTERS target, combine
> again moves from leaf hard registers.
> Eric Botcazou