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Bug 26630 - [SRPM] curious '-mcpu=k6' optimizations
[SRPM] curious '-mcpu=k6' optimizations
Product: Red Hat Raw Hide
Classification: Retired
Component: zlib (Show other bugs)
i386 Linux
medium Severity medium
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Assigned To: Trond Eivind Glomsrxd
Aaron Brown
Depends On:
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Reported: 2001-02-07 20:22 EST by Enrico Scholz
Modified: 2007-04-18 12:31 EDT (History)
1 user (show)

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Doc Type: Bug Fix
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Last Closed: 2001-02-08 22:20:23 EST
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Description Enrico Scholz 2001-02-07 20:22:28 EST
zlib compiles with a '-mcpu=k6' on all (non-k6) ix86-platforms.

It would make more sense when writing

%ifarch i386 i486 i586 i686
ZLIB_OPT_FLAGS="$ZLIB_OPT_FLAGS -O2 -fschedule-insns -fschedule-insns2
-malign-loops=1 -malign-jumps=1 -fomit

instead of the formerly

%ifarch i386 i486 i586 i686
ZLIB_OPT_FLAGS="-mcpu=k6 -O2 -fschedule-insns -fschedule-insns2
-malign-loops=1 -malign-jumps=1 -fomit

code in zlib.spec. Because $RPM_OPT_FLAGS contains architecture specific
optimizations, an option corresponding to '-mcpu=k6' will be set by this
variant also.
Comment 1 Trond Eivind Glomsrxd 2001-02-08 22:20:19 EST
This (the k6 flag) was added when Ben went on an optimization spree for zlib...
Ben, should the -march=k6 be there?
Comment 2 Ben LaHaise 2001-02-08 22:48:19 EST
This is intentional.  Specifying K6 optimizations seems to have the best overall
performance for the Athlon/PIII/Pentium/K6 mix of CPUs (it makes a 30%
difference on K6s but only a ~3% difference for other cpus).  -march=k6 can't be
specified as the resulting code wouldn't run on 386/486s.

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