Incorrect results in optimization mode

The problem is the source code violates what is called the strict aliasing rule.  Speaking loosely, the strict aliasing rule says the type used to write to memory must be closely compatible with the type used to read from memory.  For all the details, see the C99 ANSI Standard for C, section 6.5, paragraph 7.  (While the TI compiler is documented to adhere to the C89 standard, the C99 standard is substantially the same in language matters such as this, and is much easier to find online).  

Here is one example ...

doubleNumbers_Re = Y_dist_Core0_Re[i][j];
void_Pointer = (void *) &doubleNumbers_Re;
uLLInt_Pointer = (unsigned long long int *) void_Pointer;
uLLInt_Number = (unsigned long long int) *uLLInt_Pointer;
sumOfuLLInt_Numbers_Re = sumOfuLLInt_Numbers_Re + uLLInt_Number;

The memory location doubleNumbers_Re is written with type double.  But on line 4, this same memory location is read with type unsigned long long.  One of the advantages of the strict aliasing rule is it allows the compiler to presume, in this specific case, that void_Pointer and uLLInt_Pointer cannot point to the same memory location.  It is likely the compiler takes advantage of that presumption in scheduling the instructions for the loop which encloses the above lines.  However, that presumption is wrong.  And it could lead to the behavior described for this case: it works when built with no optimization, but fails when built with high levels of optimization.

The general term for this programming technique is type punning.  An internet search on that term yields some promising links that further explain the details, and offers suggestions for safer ways to implement type punning.

Thanks and regards,

-George