On 3/14/19 10:46 PM, JiangNing OS wrote: > This patch is to fix a missing ifcvt opportunity in back-end. For the simple > case below, > > if (...) > x = a; /* x is memory */ > /* no else */ > > We can generate conditional move and remove the branch as below if the target > cost is acceptable. > > r1 = x > r2 = a > cmp ... > csel r3, r1, r2, cond > x = r3 > > This could be safe if x is a stack variable, and there isn't any address > taken in current function, so the store speculation can be avoided. > > In practice, this optimization can improve a real application performance by > %4 on aarch64. This seems like something that should be addressed for gcc-10 rather than gcc-9. Can we come back to it once gcc-10 development starts?
jeff
