The -fdiv_check option enables a software patch for the floating-point division flaw which exists on some steppings of the PentiumŪ processor. This patch ensures that the precision of your floating-point division calculations are correct. This option is enabled by default or if you specify the -tpp5 option.
When the -fdiv_check option is enabled, the compiler uses libm_chk.a (or libmmtck.a, if -mt is also specified; and libmmdck.a if -md is also specified), which are special versions of the library to link your programs. These files are linked automatically. The libm_chk.a (or libmmtck.a or libmmdck.a) libraries contain the support routines for the floating-point division software patch and checked versions of the affected math library functions.
The -fdiv_check option disables the software patch for the floating-point division flaw regardless of whatever other options are specified. When you specify -fdiv_check, the compiler uses simple hardware instructions for floating-point division and affected intrinsics. If you specify the -fdiv_check option, the compiler does not need a special version of optimized math library to link your programs. Similarly, if you choose not to use the optimized math library, you must specify -fdiv_check. This option is the default if you specify the -tpp6 option.