> Thanks. Another question I have is that, in this case, will the following > > http://gcc.gnu.org/wiki/Sign_Extension_Removal > > help in removal of the sign / zero extension ?
First, it seems to me that in your case: (1) a = a | 1 /* a |= 1 */ (2) a = a | 1 /* a |= 1 */ the expressions "a | 1" in (1) and (2) are different as the "a" is not the same. So there is nothing to do for CSE. If the architecture has an instruction that does both the store and the zero extension, the zero extension instructions become redundant. The sign extension algorithm is supposed to catch such cases, but I suspect that in this simple case the regular combine is enough. Mircea
