Linux系统中使用GCC CPU参数优化代码编译
使用特定的GCC参数可以使编译出的程序执行效率有较大提升。具体如下: 1、优化原理: 在编译程序时,借助参数传递的方法,使用与系统CPU相匹配的gcc参数,编译出的程序就是为系统CPU而进行特定优化过的,因而执行速度和效率都会是最好。 2、注意事项 (1) 经过大量测试发现,在RedHat, CentOS系统中通常只能通过参数传递的方法进行编译优化,当然,如果愿意并且能够修改程序的MakeFile也可以达到这一效果,只不过比较复杂,工 作量较大。其他在网上广为流传的方法(例如:直接通过.bashrc, /etc/profile声明参数系统变量、写入/etc/make.conf等)经过测试均没有效果。 (2) 对于Gentoo Linux或FreeBSD可以通过修改/etc/make.conf添加参数的方法来实现,而不必使用参数传递法。 3、优化步骤: (1)确定系统CPU类型: # cat /proc/cpuinfo | grep "model name" 执行后会看到系统中CPU的具体型号,记下CPU型号。 (2)使用参数传递方法进行编译:(以Pentium4 CPU为例) 此处以编译Apache为例说明如何使用参数传递: # tar xzvf httpd-2.0.55.tar.gz # cd httpd-2.0.55 CHOST="i686-pc-linux-gnu" \ CFLAGS="-O3 \ -msse2 \ -mmmx \ -mfpmath=sse \ -mcpu=pentium4 \ -march=pentium4 \ -pipe \ -fomit-frame-pointer" \ CXXFLAGS="-O3 \ -msse2 \ -mmmx \ -mfpmath=sse \ -funroll-loops \ -mcpu=pentium4 \ -march=pentium4 \ -pipe \ -fomit-frame-pointer" \ ./configure ...... # make # make install 这样就通过函数传递方法实现了编译优化。下面对其中的一些参数进行具体说明: -O3:相对于-O、-O1、-O2,-O3开启了所有GCC支持的优化特性; -msse2:开启CPU所支持的sse2指令集; -mmmx:参考-msse2 -mfpmath=sse:为指定指令集生成浮点运算特性(优化浮点运算功能); -mcpu:指定CPU型号; -march:指定CPU型号,基本同-mcpu,GCC根据-march设定的CPU型号决定在生成代码时可以使用哪些种类的指令。(注意!-march参数在某些CPU型号中不可用!) -pipe:使用管道(pipe)方法替代临时文件方法在编译的不同阶段之间进行通讯。 附:常见CPU优化参数 386: CHOST="i386-pc-linux-gnu" CFLAGS="-march=i386 -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=i386 -O3 -pipe -fomit-frame-pointer" 486: CHOST="i486-pc-linux-gnu" CFLAGS="-march=i486 -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=i486 -O3 -pipe -fomit-frame-pointer" Pentium (Intel): CHOST="i586-pc-linux-gnu" CFLAGS="-march=pentium -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=pentium -O3 -pipe -fomit-frame-pointer" Pentium MMX (Intel): CHOST="i586-pc-linux-gnu" CFLAGS="-march=pentium-mmx -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=pentium-mmx -O3 -pipe -fomit-frame-pointer" Pentium PRO (Intel): CHOST="i686-pc-linux-gnu" CFLAGS="-march=pentiumpro -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=pentiumpro -O3 -pipe -fomit-frame-pointer" Pentium II (Intel): CHOST="i686-pc-linux-gnu" CFLAGS="-march=pentium2 -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=pentium2 -O3 -pipe -fomit-frame-pointer" Celeron (Intel): CHOST="i686-pc-linux-gnu" CFLAGS="-march=pentium2 -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=pentium2 -O3 -pipe -fomit-frame-pointer" Pentium III (Intel): CHOST="i686-pc-linux-gnu" CFLAGS="-march=pentium3 -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=pentium3 -O3 -pipe -fomit-frame-pointer" Celeron2 (Intel): CHOST="i686-pc-linux-gnu" CFLAGS="-march=pentium3 -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=pentium3 -O3 -pipe -fomit-frame-pointer" Celeron (Willamette-Intel): CHOST="i686-pc-linux-gnu" CFLAGS="-march=pentium4 -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=pentium4 -O3 -pipe -fomit-frame-pointer" Pentium 4 (Intel): CHOST="i686-pc-linux-gnu" CFLAGS="-march=pentium4 -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=pentium4 -O3 -pipe -fomit-frame-pointer" K6 (AMD): CHOST="i586-pc-linux-gnu" CFLAGS="-march=k6 -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=k6 -O3 -pipe -fomit-frame-pointer" K6-2 (AMD): CHOST="i586-pc-linux-gnu" CFLAGS="-march=k6-2 -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=k6-2 -O3 -pipe -fomit-frame-pointer" K6-3 (AMD): CHOST="i586-pc-linux-gnu" CFLAGS="-march=k6-3 -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=k6-3 -O3 -pipe -fomit-frame-pointer" Athlon (AMD): CHOST="i686-pc-linux-gnu" CFLAGS="-march=athlon -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=athlon -O3 -pipe -fomit-frame-pointer" Athlon-tbird, aka K7 (AMD): CHOST="i686-pc-linux-gnu" CFLAGS="-march=athlon-tbird -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=athlon-tbird -O3 -pipe -fomit-frame-pointer" Athlon-tbird XP (AMD): CHOST="i686-pc-linux-gnu" CFLAGS="-march=athlon-xp -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=athlon-xp -O3 -pipe -fomit-frame-pointer" Athlon 4(AMD): CHOST="i686-pc-linux-gnu" CFLAGS="-march=athlon-4 -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=athlon-4 -O3 -pipe -fomit-frame-pointer" Athlon XP (AMD): CHOST="i686-pc-linux-gnu" CFLAGS="-march=athlon-xp -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=athlon-xp -O3 -pipe -fomit-frame-pointer" Athlon MP (AMD): CHOST="i686-pc-linux-gnu" CFLAGS="-march=athlon-mp -O3 -pipe -fomit-frame-pointer" CXXFLAGS="-march=athlon-mp -O3 -pipe -fomit-frame-pointer" 603 (PowerPC): CHOST="powerpc-unknown-linux-gnu" CFLAGS="-O3 -pipe -fomit-frame-pointer -fsigned-char" CXXFLAGS="-O3 -pipe -fomit-frame-pointer -fsigned-char" 603e (PowerPC): CHOST="powerpc-unknown-linux-gnu" CFLAGS="-O3 -pipe -fomit-frame-pointer -fsigned-char" CXXFLAGS="-O3 -pipe -fomit-frame-pointer -fsigned-char" 604 (PowerPC): CHOST="powerpc-unknown-linux-gnu" CFLAGS="-O3 -pipe -fomit-frame-pointer -fsigned-char" CXXFLAGS="-O3 -pipe -fomit-frame-pointer -fsigned-char" 604e (PowerPC): CHOST="powerpc-unknown-linux-gnu" CFLAGS="-O3 -pipe -fomit-frame-pointer -fsigned-char" CXXFLAGS="-O3 -pipe -fomit-frame-pointer -fsigned-char" 750 aka as G3 (PowerPC): CHOST="powerpc-unknown-linux-gnu" CFLAGS="-mcpu=750 -O3 -pipe -fomit-frame-pointer -fsigned-char" CXXFLAGS="-mcpu=750 -O3 -pipe -fomit-frame-pointer -fsigned-char" 7400, aka G4 (PowerPC): CHOST="powerpc-unknown-linux-gnu" CFLAGS="-mcpu=7400 -O3 -pipe -fomit-frame-pointer -fsigned-char -maltivec" CXXFLAGS="-mcpu=7400 -O3 -pipe -fomit-frame-pointer -fsigned-char -maltivec" 7450, aka G4 second generation (PowerPC): CHOST="powerpc-unknown-linux-gnu" CFLAGS="-mcpu=7450 -O3 -pipe -fomit-frame-pointer -fsigned-char -maltivec" CXXFLAGS="-mcpu=7450 -O3 -pipe -fomit-frame-pointer -fsigned-char -maltivec" PowerPC (If you don't know which one): CHOST="powerpc-unknown-linux-gnu" CFLAGS="-O3 -pipe -fomit-frame-pointer -fsigned-char" CXXFLAGS="-O3 -pipe -fomit-frame-pointer -fsigned-char" Sparc: CHOST="sparc-unknown-linux-gnu" CFLAGS="-O3 -pipe -fomit-frame-pointer" CXXFLAGS="-O3 -pipe -fomit-frame-pointer" Sparc 64: CHOST="sparc64-unknown-linux-gnu" CFLAGS="-O3 -pipe -fomit-frame-pointer" CXXFLAGS="-O3 -pipe -fomit-frame-pointer" |