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From: "matt at use dot net" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/51233] New: [ipa-iterations] running multiple passes of early IPA on zlib produces more optimal code Date: Sun, 20 Nov 2011 03:31:00 -0000 [thread overview] Message-ID: <bug-51233-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51233 Bug #: 51233 Summary: [ipa-iterations] running multiple passes of early IPA on zlib produces more optimal code Classification: Unclassified Product: gcc Version: 4.7.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: middle-end AssignedTo: unassigned@gcc.gnu.org ReportedBy: matt@use.net Using current trunk, with Maxim's eipa-iterations patch. I modified the zlib 1.2.3.4 makefile (from Ubuntu 11.10's source package) as such for building on my Ubuntu 11.10/amd64 system: CC=gcc CFLAGS=--param eipa-iterations=3 -flto -Ofast SFLAGS=$(CFLAGS) -shared -fPIC LDFLAGS=-flto -L. libz.a And then built and tested the resulting minigzip utility both at the macro-level (total runtime), and the micro-level (using callgrind's cache miss and branch misprediction benchmarks). Macro level, when run a single 50MB file on a ramdisk in single user mode shows minor improvements that may qualify as noise. At the micro level, callgrind shows 0.4% fewer branch mispredictions, and a dramatic decrease in data accesses (but a slight uptick in data cache misses). While there are some notable code differences between 2 and 3 iterations, they don't appear to have an effect on the performance at the macro- or micro-level. Given the relative simplicity of the code in the library, these additional optimizations could possibly have been gotten within a single iteration.
next reply other threads:[~2011-11-20 1:04 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-11-20 3:31 matt at use dot net [this message] 2012-08-10 9:52 ` [Bug middle-end/51233] " rguenth at gcc dot gnu.org 2012-08-14 0:26 ` matt at use dot net 2012-08-14 8:23 ` rguenth at gcc dot gnu.org 2012-08-14 17:43 ` matt at use dot net 2012-12-04 20:35 ` matt at use dot net 2012-12-05 9:24 ` richard.guenther at gmail dot com
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