5. TIPS

Here are a few guidelines that will help the compiler generate more efficient code, some of the tips are specific to this compiler others are generally good programming practice.

• Use the smallest data type to represent your data-value. If it is known in advance that the value is going to be less than 256 then use a 'char' instead of a 'short' or 'int'.
• Use unsigned when it is known in advance that the value is not going to be negative. This helps especially if you are doing division or multiplication.
• NEVER jump into a LOOP.
• Declare the variables to be local whenever possible, especially loop control variables (induction).
• Since the compiler does not do implicit integral promotion, the programmer should do an explicit cast when integral promotion is required.
• Reducing the size of division, multiplication & modulus operations can reduce code size substantially. Take the following code for example. 
   
  foobar(unsigned int p1, unsigned char ch) 
  { 
  unsigned char ch1 = p1 % ch ; 
  ....  
  } 
  
  For the modulus operation the variable ch will be promoted to unsigned int first then the modulus operation will be performed (this will lead to a call to support routine _muduint()), and the result will be casted to an int. If the code is changed to
   
  foobar(unsigned int p1, unsigned char ch) 
  { 
  unsigned char ch1 = (unsigned char)p1 % ch ; 
  ....  
  } 
  
  It would substantially reduce the code generated (future versions of the compiler will be smart enough to detect such optimization oppurtunities).