In some cases, the compiler cannot optimize code to completely avoid data hazards. However, it is often possible to change the source code to achieve this, mainly by better utilization of the general purpose registers.
The following C code example shows the multiplication of a static array in
memory:
static int a[4], b[4], c[4];
register int a0, a1, a2, a3, b0, b1, b2, b3, c0, c1, c2, c3;
a0 = a[0]; a1 = a[1]; a2 = a[2]; a3 = a[3];
b0 = b[0]; b1 = b[1]; b2 = b[2]; b3 = b[3];
c0 = a0 * b0; c1 = a1 * b1; c2 = a2 * b2; c3 = a3 * b3;
c[3] = c3; c2 = c[2]; c1 = c[1]; c0 = c[0];This code ensures that load instructions are first executed to load operands into separate registers, which are then multiplied and finally stored. The code can be extended up to eight multiplications without running out of general purpose registers.