Kenneth Zadeck <zadeck@naturalbridge.com> writes:
+ It would be trivial to define a similar set of functions that work
+ in the forwards direction. The only changes would be to process
+ the uses before the defs and properly rename the functions. This
+ has so far not been necessary.
But this isn't true, is it? The comment seems to describe what
the removed function does, but I think the removed function is wrong.
With forward scanning, a value is born at the point of definition and
dies after the last use (if any). The point of death is indicated
by REG_DEAD and REG_UNUSED notes.
So the forward version of df_simulate_on_insn would do something like:
- kill all values in REG_DEAD notes
- make all defined values live
- kill all values in REG_UNUSED notes
Despite what the comment says, I don't think it would look at the
DF_REF_USES at all.
I'm not saying you should say all that in the comment ;) But I think
it's one of those comments that's more misleading than helpful.
Richard