This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [tree-ssa] Removal of gotos from cfg based ir


In message <1068848004.5920.23.camel@p4>, Andrew MacLeod writes:
 >I would suggest that maybe you could put the execution counts right in
 >the GOTO_EXPR's...  oh, we NULL out the fallthru ones now don't we. hmm.
 >why do we do that again? 
Because if you leave them in, you get a 40% increase in the number of
jumps created when you translate from trees into rtl.


 >> On RTL we used to represent profile by notes but it never worked very
 >> well (in fact we never managed to use that information).  My experience
 >> with any unrelated anotations on instruction stream is very bad.
 >> Perhaps it can be done somehow in significantly better way, but RTL
 >> scheme of REG_EQUIV/LOOP/SCOPE and similar notes has ever brought us
 >> headaches.
 >>
 >the attraction of the notes concept is that it is optional. If the note
 >isnt there, you dont have the information, so you dont use it. If you
 >are going to make up the information in the absence of notes, then you
 >are promoting the information from optional to necessary, its just that
 >you have to make up the values before proceeding, so notes kind of fall
 >apart there. PLus, in rtl there were lots of kinds of note, so you had
 >to hunt to see if there were there, etc etc. I didnt like notes much
 >either :-)
Notes suck.  Both the kind attached to insns and the kind which appear
between insns.    We've got the same fundamental problem with annoatations
right now that we're going to have to solve one day.


jeff


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]