------- Additional Comments From mark at codesourcery dot com 2005-03-03 21:19 ------- Subject: Re: [3.4 Regression] const/pure functions result in bad asm
ebotcazou at gcc dot gnu dot org wrote: > ------- Additional Comments From ebotcazou at gcc dot gnu dot org 2005-03-03 > 21:12 ------- > >>I don't think I'd try to be that clever. We might want the >>stabilization to occur even in other cases. In looking at it more >>closely, it definitely looks like stabilize_reference should deal with >>CALL_EXPRs. > > > But then what's the difference with setting TREE_SIDE_EFFECTS on CALL_EXPRs? > Also for 3.4.x some FE don't use tree inlining at all so I don't think they > should be penalized because of the C++ FE. There are other places where TREE_SIDE_EFFECTS matters. (Like, "do we have to emit this expression at all, if its result is not used?") The counter to your argument is that I don't see why the C++ front end should be penalized because other front ends have a workaround for what seems to be a bug in the middle end. The stated purpose for stabilize_reference is to make it possible to use an expression more than once. If CALL_EXPRs can't be used more than once (which your research would seem to prove), then it seems like stabilize_reference should handle that. >>(I guess I was thinking that the problem with the duplicate labels could >>be avoided in the inliner by generating fresh labels. But, maybe that's >>not going to work for other reasons.) > > How would you do that exactly? In our present case, the inliner inlines > exactly > one CALL_EXPR, but it is referenced twice in another tree. OK, I'm confused, then -- I think that either we have to fix this problem in stabilize_reference (which seems better to me) or always set TREE_SIDE_EFFECTS on CALL_EXPRs in build3. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17972
