This is done by splitting the transformation into an analysis phase and a transformation phase (which does not use the dominator tree anymore).
The domintator tree is recalucated once after the whole function is processed.
This change eventually solves the compile time problem of rdar://problem/24410167.
The main intention for this change is to eliminate the use of the post/dominator trees in this transformation.
These were re-calculated on every conversion which caused long compile times for functions with lot of switch_enum instructions: rdar://problem/24410167
Beside that, the code for collecting the target-block's predecessors is now simpler. It's not necessary to handle arbitrary control flow pathes because jump threading is simplifying the CFG anyway.
Now SimplifyCFG does not use the PostDominanceAnalysis anymore.
SILValue.h/.cpp just defines the SIL base classes. Referring to specific instructions is a (small) kind of layering violation.
Also I want to keep SILValue small so that it is really just a type alias of ValueBase*.
NFC.
As there are no instructions left which produce multiple result values, this is a NFC regarding the generated SIL and generated code.
Although this commit is large, most changes are straightforward adoptions to the changes in the ValueBase and SILValue classes.
This change is needed for the next update to ToT LLVM. It can be put
into place now without breaking anything so I am committing it now.
The churn upstream on ilist_node is neccessary to remove undefined
behavior. Rather than updating the different ilist_node patches for the
hacky change required to not use iterators, just use iterators and keep
everything as ilist_nodes. Upstream they want to eventually do this, so
it makes sense for us to just do it now.
Please do not introduce new invocations of
ilist_node::get{Next,Prev}Node() into the tree.
In all of the cases where this is being used, we already immediately perform an
unreachable if we find a TermKind::Invalid. So simplify the code and move it
into the conversion switch itself.
This exposed the first interesting bug found by using TermKind, in DCE we were
not properly handling switch_enum_addr and checked_cast_addr_br.
SR-335
rdar://23980060
This check should not trigger, at least with the current definition of what a convert_function may do.
But still it's a good idea to make the check to be on the safe side.
This just runs a transform range on getSuccessor()'s ArrayRef<SILSuccessor> so
one does not need to always call Successor.getBB() when iterating over successor
blocks. Instead the transform range does that call for you.
I also updated some loops to use this new SILBasicBlock method to make sure that
the code is tested out by tests that are already in tree. All these places
should be functionally the same albeit a bit cleaner.
(libraries now)
It has been generally agreed that we need to do this reorg, and now
seems like the perfect time. Some major pass reorganization is in the
works.
This does not have to be the final word on the matter. The consensus
among those working on the code is that it's much better than what we
had and a better starting point for future bike shedding.
Note that the previous organization was designed to allow separate
analysis and optimization libraries. It turns out this is an
artificial distinction and not an important goal.
