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Eric Botcazou wrote:
> 2007-01-06 Eric Botcazou <ebotcazou@adacore.com> > > * tree-sra.c (sra_walk_fns) <ldst>: Document new restriction. > (sra_walk_modify_expr) <rhs_elt>: Treat the reference as a use > if the lhs has side-effects. > <lhs_elt>: Treat the reference as a use if the rhs has side-effects. > > :ADDPATCH Tree-SRA:
I've read through this thread, and I think Eric's patch makes sense. (I think Richard G. eventually came to the same conclusion, so I'm not claiming this is some brilliant insight on my part.) Even in C, keeping volatile accesses "more atomic" seems like a good thing. And, certainly, any possible pessimization by not doing individual accesses to move data out of volatile structures is going to be insignificant, to overall program runtime.
I agreed to fix the (possible) regression on the branches with Eric's patch. I didn't agree to put the same fix on the mainline until we first had a precise definition of what constraints the Ada frontend (seems to) put on the middle-end. And with the further conversation it looks to me what the Ada frontend does/wants isn't what it communicates to the middle-end.
So I'm against applying the patch to the mainline without proper texi documentation of what Ada does here (it should make little sense, too, of course).
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