[tree-ssa] Merge results as of 2003-05-06

[law@redhat.com]

In message <wvly91i53p6.fsf@prospero.boston.redhat.com>, Jason Merrill writes:
 >On Thu, 08 May 2003 00:29:36 -0600, law@redhat.com wrote:
 >Actually, now that I think about it we can't really free temp slots,
 >because in GIMPLE all temporaries look like automatic variables in the
 >outer block of the function.  In this testcase, we don't see a single temp
 >that we don't want to keep forever.
Ouch.

 >A simple solution may just be to disable all the temp_slots management code
 >when we're using the tree optimizers.  A better solution would be to fix
 >the temp_slots data structure so that we don't keep slogging through the
 >whole list when we're only interested in slots from a particular level.
Yup.  We also want to eliminate the variables we don't actually use.  Gimple
likes to create lots of temporaries.  Many of them can goaway as a result
of our optimizers.

The only thing standing in our way is we mis-handle gimplification of
SAVE_EXPRs when they have a context which is not the current function.
[ Yes, I have resolved all the other pesky little issues with incorrect
  dataflow information being generated. ]


 >My expression temps patch should help to cut down on the number of temps we
 >have to deal with; it cuts the number in this testcase by 75%.
What's the status of this -- I know you mentioned it needed further work,
but it sounds quite promising.

jeff