From: "Cui, Lili" <lili.cui@intel.com>
To: Jan Hubicka <hubicka@kam.mff.cuni.cz>
Cc: "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>,
"Liu, Hongtao" <hongtao.liu@intel.com>,
"Lu, Hongjiu" <hongjiu.lu@intel.com>
Subject: RE: [PATCH] Add a heuristic for eliminate redundant load and store in inline pass.
Date: Sun, 10 Jul 2022 14:04:45 +0000 [thread overview]
Message-ID: <SJ0PR11MB5600A247DEFA7693C673C4C89E849@SJ0PR11MB5600.namprd11.prod.outlook.com> (raw)
In-Reply-To: <Ysb9b/x+i1nlTa79@kam.mff.cuni.cz>
> -----Original Message-----
> From: Jan Hubicka <hubicka@kam.mff.cuni.cz>
> This is interesting idea. Basically we want to guess if inlining will
> make SRA and or strore->load propagation possible. I think the
> solution using INLINE_HINT may be bit too trigger happy, since it is very
> common that this happens and with -O3 the hints are taken quite sriously.
>
> We already have mechanism to predict this situaiton by simply expeciting
> that stores to addresses pointed to by function parameter will be
> eliminated by 50%. See eliminated_by_inlining_prob.
>
> I was thinking that we may combine it with a knowledge that the parameter
> points to caller local memory (which is done by llvm's
> heuristics) which can be added to IPA predicates.
>
> The idea of checking that the actual sotre in question is paired with load at
> caller side is bit harder: one needs to invent representation for such
> conditions. So I wonder how much extra help we need for critical inlning to
> happen at imagemagics?
Hi Honza,
Really appreciate for the feedback. I found that eliminated_by_inlining_prob does eliminated the stmt 50% of the time, but the gap is still big.
SRA cannot split callee's parameter for "Do not decompose non-BLKmode parameters in a way that would create a BLKmode parameter. Especially for pass-by-reference (hence, pointer type parameters), it's not worth it."
Critical inline function information
Caller: GetVirtualPixelsFromNexus
size: 541
time: 484.08
e->freq: 0.83
Callee: SetPixelCacheNexusPixels
nonspec time: 46.60
time : 36.18
size: 87
Since the insns number 87 of callee function is bigger than inline_insns_auto (30) and there is no hint, so inline depends on "big_speedup_p (e)". 484.08 (caller_time) * 0.15 (param_inline_min_speedup == 15) = 72.61, which means callee's time should be at least 72.61, but callee's time is 46.60, so we need to lower param_inline_min_speedup to 3 or 4. I checked the history(https://gcc.gnu.org/bugzilla/show_bug.cgi?format=multiple&id=83665), that you tried changing it to 8, but that increases the gzip code size by 2.5KB. so I want to add a heuristic hit for it.
Thanks,
Lili.
>
> Honza
next prev parent reply other threads:[~2022-07-10 14:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-06 10:50 Cui,Lili
2022-07-07 15:36 ` Jan Hubicka
2022-07-10 14:04 ` Cui, Lili [this message]
2022-07-18 22:38 ` Cui, Lili
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