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Re: Short-circuit some bitmap lookups
- From: "David S. Miller" <davem at redhat dot com>
- To: Richard dot Earnshaw at arm dot com, rearnsha at arm dot com
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Fri, 24 May 2002 05:09:28 -0700 (PDT)
- Subject: Re: Short-circuit some bitmap lookups
- References: <200205211448.PAA20689@cam-mail2.cambridge.arm.com>
From: Richard Earnshaw <rearnsha@arm.com>
Date: Tue, 21 May 2002 15:48:16 +0100
As discussed on the recent thread on compile-time performance:
On Mon, May 20, 2002 at 02:34:12PM +0100, Richard Earnshaw wrote:
> Here's some more relatively low hanging fruit to pick. bitmap_find_bit is
> probably the most-called function in the compiler (ok, it is inlined, but
> it is still effectively called). This cuts the execution time of the
> function by about 45% (according to gprof). It simply notes that if head->
> current is the element we want, we don't have to go and do a lot of
> grunging to reposition the current element to itself!
Bootstrapped on i686-linux.
2002-05-21 Richard Earnshaw <rearnsha@arm.com>
* bitmap.c (bitmap_find_bit): Return early if we have the correct
element cached.
Richard, after some discussion with Mark I've installed your change on
the branch as well after doing bootstrap/regtesting on sparc-linux and
sparc64-linux.
Franks a lot,
David S. Miller
davem@redhat.com