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Re: [PATCH ppc64,aarch64,alpha 00/15] Improve backend constant generation
- From: Richard Henderson <rth at redhat dot com>
- To: Wilco Dijkstra <wdijkstr at arm dot com>
- Cc: "'GCC Patches'" <gcc-patches at gcc dot gnu dot org>, Richard Earnshaw <Richard dot Earnshaw at arm dot com>, Marcus Shawcroft <Marcus dot Shawcroft at arm dot com>, dje dot gcc at gmail dot com
- Date: Wed, 12 Aug 2015 09:08:58 -0700
- Subject: Re: [PATCH ppc64,aarch64,alpha 00/15] Improve backend constant generation
- Authentication-results: sourceware.org; auth=none
- References: <A610E03AD50BFC4D95529A36D37FA55E7B006D6780 at GEORGE dot Emea dot Arm dot com> <005301d0d517$ddd8a030$9989e090$ at com>
On 08/12/2015 08:59 AM, Wilco Dijkstra wrote:
> I looked at the statistics of AArch64 immediate generation a while ago.
> The interesting thing is ~95% of calls are queries, and the same query is on
> average repeated 10 times in a row. So (a) it is not important to cache the
> expansions, and (b) the high repetition rate means a single-entry cache
> has a 90% hitrate. We already have a patch for this and could collect stats
> comparing the approaches. If a single-entry cache can provide a similar
> benefit as caching all immediates then my preference would be to keep things
> simple and just cache the last query.
Interesting. That's already more detailed investigation than I'd done. I had
no idea the queries were so clustered. I assumed that the queries would be
scattered across various passes, and so the various constants across the
function would get checked in sequence.
I would be very interested in seeing those stats when you've done.
r~