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
David Nielsen said:
> The -mcpu flag is depricated in GCC 3.3 - and should not be used
anymore. So in all fairness it would be best not to record it's usage, it might mislead some users. The only depreciation I could find concerning mcpu is in the mips port, where it might not me appropriate. For x86 architectures it is available though and it also serves a needed option as it determines instruction scheduling. The march option does not, the march option determines which instructions are used. As scheduling for an architecture lower than the instructions is pointless implying mcpu makes sense. It is perfectly legal though to specify CFLAGS="-march=pentium -mcpu=pentium4" This would create code that runs on anything bigger than a pentium, but is optimally scheduled for the pentium4 processor. Scheduling has become increasingly important with the newer (pentium and further) processors as they have the ability to run some (but not all) instructions paralel to eachother. A p4 though provides more pipelines than a p1, so instructions need to be scheduled differently to optimally use all pipelines. Paul -- Paul de Vrieze Researcher Mail: pauldv@××××××.nl Homepage: -- Paul de Vrieze Researcher Mail: pauldv@××××××.nl Homepage: -- gentoo-dev@g.o mailing list