On 7/27/2021 12:27 AM, Richard Biener wrote:
On Fri, 23 Jul 2021, Jeff Law wrote:
On 7/15/2021 4:08 AM, Jiufu Guo via Gcc-patches wrote:
Refine code for V2 according to review comments:
* Use if check instead assert, and refine assert
* Use better RE check for test case, e.g. (?n)/(?p)
* Use better wording for target.def
Currently, doloop.xx variable is using the type as niter which may be
shorter than word size. For some targets, it would be better to use
word size type. For example, on 64bit system, to access 32bit value,
subreg maybe used. Then using 64bit type maybe better for niter if
it can be present in both 32bit and 64bit.
This patch add target hook for querg perferred mode for doloop IV.
And update mode accordingly.
Bootstrap and regtest pass on powerpc64le, is this ok for trunk?
BR.
Jiufu
gcc/ChangeLog:
2021-07-15 Jiufu Guo <guoji...@linux.ibm.com>
PR target/61837
* config/rs6000/rs6000.c (TARGET_PREFERRED_DOLOOP_MODE): New hook.
(rs6000_preferred_doloop_mode): New hook.
* doc/tm.texi: Regenerate.
* doc/tm.texi.in: Add hook preferred_doloop_mode.
* target.def (preferred_doloop_mode): New hook.
* targhooks.c (default_preferred_doloop_mode): New hook.
* targhooks.h (default_preferred_doloop_mode): New hook.
* tree-ssa-loop-ivopts.c (compute_doloop_base_on_mode): New function.
(add_iv_candidate_for_doloop): Call targetm.preferred_doloop_mode
and compute_doloop_base_on_mode.
gcc/testsuite/ChangeLog:
2021-07-15 Jiufu Guo <guoji...@linux.ibm.com>
PR target/61837
* gcc.target/powerpc/pr61837.c: New test.
My first reaction was that whatever type corresponds to the target's word_mode
would be the right choice. But then I remembered things like dbCC on m68k
which had a more limited range. While I don't think m68k uses the doloop
bits, it's a clear example that the most desirable type may not correspond to
the word type for the target.
So my concern with this patch is its introducing more target dependencies into
the gimple pipeline which is generally considered undesirable from a design
standpoint. Is there any way to lower from whatever type is chosen by ivopts
to the target's desired type at the gimple->rtl border rather than doing it in
ivopts?
I think that's difficult - after all we want to base other IV uses on
the doloop IV if possible. So IMHO it's not different from IVOPTs
choosing different IVs based on RTL costing and target addressing mode
availability so I wasn't worried about those additional target
dependences at this point of the GIMPLE pipeline.
Yea, you're probably right on both accounts. With that resolved I
think this is OK for the trunk.
Thanks for your patience Jiufu and thanks for chiming in Richi.
jeff
