search for: subexpresion

...n gcc or ICC. Consider the following trivial function: void foo(int a, int b, int c, int d, int e, int *res) { res[0] = (e * a) * d; res[1] = (e * b) * d; res[2] = (e * c) * d; } This function can be optimized down to 4 multiplies instead of 6 by reassociating such that (e*d) is the common subexpresion. However, no compiler I’ve tested does this. I wrote a slightly hacky heuristic algorithm to augment reassociate to do this and tested it. First, before the details, the results: on a large offline test suite of graphics shaders it cut down total instruction count by ~0.9% (!) and float math instr...