◄Up► ◄Contents► ◄Index► ◄Back► ─────C/C++ Compiler───────────────────────────────────────────────────────── Syntax: /Oc /Og Use of either the /Oc or the /Og option allows the compiler to calculate the value of a common subexpression once. For example, "b + c" is common to the following code. If the values of b and c do not change between the three expressions, the compiler can calculate the value of b + c once, assign the calculation to a temporary variable, and substitute the variable as appropriate. a = b + c; d = b + c; e = b + c; When you use the /Oc option (default common subexpression optimization) the compiler examines short sections of code (basic blocks) for common subexpressions. When you use the /Og option (enable global common subexpression optimization) the compiler searches entire functions for common subexpressions. You can disable the default common subexpression optimization with the /Od option. NOTE: You can enable or disable block-scope common subexpression optimization on a function-by-function basis using the optimize pragma with the c option. You can enable or disable global common subexpression optimization on a function-by- function basis using the optimize pragma with the g option. -♦-