> > Hi! > > > > If TREE_BINFO has BV_VCALL_INDEX set, this needs to be dynamically > > adjusted, but none of the callers are prepared to handle that. > > Thus, this patch makes devirtualization give up in those cases. > > > > Bootstrapped/regtested on x86_64-linux and i686-linux, trunk and 4.6. > > On the trunk the testcase ICEs before and after the patch in some new > > callgraph > > checking (added today or so, Honza?), on the branch it works just fine. > > The ICE for me is: > jakub.C:77:1: error: a call to thunk improperly represented in the call graph: > # VUSE <.MEM_11> > D.2319_3 = D::_ZTv0_n24_NK1D1mEv (&q.D.2159); > > void test()/26(14) @0x7ffff77066f0 (asm: _Z4testv) availability:available > analyzed needed reachable body externally_visible finalized > called by: int main()/28 (1.00 per call) (can throw external) > calls: void bar(int)/1 (1.00 per call) void bar(int)/1 (1.00 per call) > virtual int D::m() const/15 (1.00 per call) D::D(const A&)/14 (1.00 per call) > References: > Refering this function: > has 3 outgoing edges for indirect calls. > > this is not my snaity check, but Martins and I think it means that somehow > your > change is ineffective on mainline and we still devirtualize. > Martin, I declare this problem yours.
Actually what happens here is that CCP devirtualize by propagating the constructors and due to Richard's new code to drop OBJ_TYPE_REF we finally get a direct call. This is all good and desirable. I think good solution would be to fold further and inline the thunk adjustment, just like the type based devirtualization does. Even once I get far enough with my cgraph cleanuping project to make cgraph represent thunks nicely, we would win if in these cases ccp and other passes simply inlined the this adjustment, like we do with type based devirtualization already. Martin, I guess it is matter of looking up the thunk info by associated cgraph node alias and extending fold_stmts of passes that now drop the OBJ_TYPE_REF wrappers? Honza
