Gentoo Archives: gentoo-dev

From: Paul de Vrieze <pauldv@g.o>
To: gentoo-dev@g.o
Subject: Re: [gentoo-dev] [ANN] CFLAGS Builder
Date: Mon, 19 May 2003 11:13:25
1 David Nielsen said:
2 > The -mcpu flag is depricated in GCC 3.3 - and should not be used
3 anymore. So in all fairness it would be best not to record it's usage,
4 it might mislead some users.
6 The only depreciation I could find concerning mcpu is in the mips port,
7 where it might not me appropriate. For x86 architectures it is available
8 though and it also serves a needed option as it determines instruction
9 scheduling. The march option does not, the march option determines which
10 instructions are used. As scheduling for an architecture lower than the
11 instructions is pointless implying mcpu makes sense. It is perfectly legal
12 though to specify
13 CFLAGS="-march=pentium -mcpu=pentium4" This would create code that runs on
14 anything bigger than a pentium, but is optimally scheduled for the
15 pentium4 processor. Scheduling has become increasingly important with the
16 newer (pentium and further) processors as they have the ability to run
17 some (but not all) instructions paralel to eachother. A p4 though provides
18 more pipelines than a p1, so instructions need to be scheduled differently
19 to optimally use all pipelines.
21 Paul
23 --
24 Paul de Vrieze
25 Researcher
26 Mail: pauldv@××××××.nl
27 Homepage:
30 --
31 Paul de Vrieze
32 Researcher
33 Mail: pauldv@××××××.nl
34 Homepage:
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40 gentoo-dev@g.o mailing list