> One suggests using -O3 -pipe, the other, -O2 without > the pipe. > > How much difference does this make? Is the extra level > of optimization with pipe the equivalent of the lower > level without?
From the gcc manpage: -pipe Use pipes rather than temporary files for communication between the various stages of compilation. This fails to work on some systems where the assembler is unable to read from a pipe; but the GNU assembler has no trouble. The pipe is only for speeding up the compiling process. It does not speed up binaries. The -O3 contains some more optimizations than -O2, which can result in much bigger applications and may be contraproductive. The -O2 is widely recommended, but I guess you won't feel a big difference anyway. See man gcc for a more detailled description. - Sascha
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