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Re: [RFC] Don't completely scalarize a record if it contains bit-field (PR tree-optimization/45144)
- From: Mark Mitchell <mark at codesourcery dot com>
- To: Jie Zhang <jie at codesourcery dot com>
- Cc: Richard Guenther <richard dot guenther at gmail dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 02 Aug 2010 09:52:38 -0700
- Subject: Re: [RFC] Don't completely scalarize a record if it contains bit-field (PR tree-optimization/45144)
- References: <4C52F946.firstname.lastname@example.org> <AANLkTimbiUfL5EmxEczuo6jhLroLvFpY78tgU1Gx3JJy@mail.gmail.com> <4C5307CE.email@example.com> <4C563B34.firstname.lastname@example.org>
Jie Zhang wrote:
> My patch prevents several full scalarizations of records with bit-field
> when compiling Linux kernel for x86_64, but none of these causes
> differences in final assemblies. I use 126.96.36.199 and the default config
> for x86_64. I checked -O2 and -Os.
That seems at odds with the statement made previously in this thread
that this optimization was essential for Linux kernel performance.
If Jie's statement is accurate, then, whether or not this is a "hack",
it seems like a win. I don't see anything wrong with accepting a small,
local improvement that has no user-observable negative impact; we can
always rip it out and replace it with something better when something
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