Ensuring the correctness of our compilers is our number one priority. We take pride in our work, and employ solid software engineering techniques to minimize the number of defects. Moreover, we license an industrial strength front end (the part of the compiler that understands the syntax and semantic of the C language), so that rarely have any C language bugs been discovered since our first product was shipped in 1994.
Code generators (the part of the compiler that understands the target machines) are especially difficult to test since there are many special cases and code patterns. To ensure the correctness of our compilers, we have engineered automated test suites and populated them with tests that we have written over the years. These tests touch on various aspect of the compiler, from handling different types of expressions to library function correctness.
In 2003, we went a step further by developing a test suite that allows testing a compiler for correct handling of the integer operations such as addition, subtraction, multiplication, and division in a pseudo-exhaustive manner.
These test operations are in the form of:

 c = a + b; 

  and 

 a += b;