Dead code elimination

Dead code elimination removes unneeded instructions from the program.

Dead code is a section in the source code of a program, which is executed but whose result is never used in any other computation.

Dead code execution prevents from wastes of computation time and memory.

For example,

z = x*y;
a = x;  // dead code
w = x*y+6;

After dead code elimination above program become,

z = x*y;
w = x*y+6;