TMS320F28377D: Optimal RAM usage for CLA operations

// global variables, declared elsewhere
// float x_in; 	//input to IIR. In Cpu1ToCla1 message RAM
// float xn;		//copy of x_in. Accessed frequently by IIR code
// float D[6];		//shift register/accumulator for IIR
// float A[4]; 	//denominator coefficients of IIR
// float B[4]; 	//numerator coefficients of IIR
// float yn;		//output of IIR. Accessed frequently by IIR code
// float y_out;	//copy of yn. In Cla1ToCpu1 message RAM

static inline void run3p3z_CLA(void)
{   //transposed direct form II
    //     Network Diagram  :
    //
    // xn------>(x)--->(+)--------------->yn
    //      |    ^      ^             |
    //      |    |      |D[5]         |
    //      |    B(0)  (z)            |
    //      |           ^             |
    //      |           |D[4]         |
    //      |-->(x)--->(+)<-----(x)---|
    //      |    ^      ^        ^    |
    //      |    |      |D[3]    |    |
    //      |    B(1)  (z)       A(1) |
    //      |           ^             |
    //      |           |D[2]         |
    //      --->(x)--->(+)<-----(x)----
    //      |    ^      ^        ^    |
    //      |    |      |D[1]    |    |
    //      |    B(2)  (z)       A(2) |
    //      |           ^             |
    //      |           |D[0]         |
    //      --->(x)--->(+)<-----(x)----
    //           ^               ^
    //           |               |
    //           B(3)            A(3)
    //

    xn=x_in; //copy from shared message ram to local ram to reduce conflicts between cla and cpu!!!!
    yn = xn*B[0] + D[5];

    D[4] = xn*B[1] + yn*A[1] + D[3];
    D[5] = D[4];

    D[2] = xn*B[2] + yn*A[2] + D[1];
    D[3] = D[2];

    D[0] = xn*B[3] + yn*A[3];
    D[1] = D[0];
}