On 03/08/06 11:54, Richard Guenther wrote: > i.e. we see that for a = b it's a killing def, while the assignment to > a.x[2] is only > partial. So what will we have in mem-ssa for the killing a = b and > the partial def? > Right now, nothing. Memory SSA gives you an identical IL in this case.
Removing V_MUST_DEFs is orthogonal to memory SSA. Taking your example, what wouldn't you be able to do if the code was: # a_3 = VDEF <a_2> # VUSE <b_1> a = b; # VUSE <b_1> D.1284_4 = b.x[2]; # a_5 = VDEF <a_3> a.x[2] = D.1284_4; I'm trying to look for cases where replacing V_MUST_DEF with V_MAY_DEF would cause the optimizers to take over-conservative decisions, and those over-conservative decisions are *impossible* to fix without the notion of V_MUST_DEF.
