"minimal" SSA form (in other words, it doesn't insert dead PHIs).  This
speeds up the mem2reg pass very significantly because it doesn't have to
do a lot of frivolous work in many common cases.

In the 252.eon function I have been playing with, this doesn't even insert
the 120 PHI nodes that it used to which were trivially dead (in the process
of promoting 356 alloca instructions overall).  This speeds up the mem2reg
pass from 1.2459s to 0.1284s.  More significantly, the DCE pass used to take
2.4138s to remove the 120 dead PHI nodes that mem2reg constructed, now it
takes 0.0134s (which is the time to scan the function and decide that there
is nothing dead).  So overall, on this one function, we speed things up a
total of 3.5179s, which is a 24.8x speedup!  :)

This change is tested by the Mem2Reg/2003-10-05-DeadPHIInsertion.ll test,
which now passes.

llvm-svn: 8884

llvm-svn: 8883

basic block.  This is amazingly common in code generated by the C/C++ front-ends.
This change makes it not have to insert ANY phi nodes, whereas before it would insert
a ton of dead ones which DCE would have to clean up.

Thus, this fix improves compile-time performance of these trivial allocas in two ways:
  1. It doesn't have to do the walking and book-keeping for renaming
  2. It does not insert dead phi nodes for them which would have to
     subsequently be cleaned up.

On my favorite testcase from 252.eon, this special case handles 305 out of
356 promoted allocas in the function.  It speeds up the mem2reg pass from 7.5256s
to 1.2505s.  It inserts 677 fewer dead PHI nodes, which speeds up a subsequent
-dce pass from 18.7524s to 2.4806s.

There are still 120 trivially dead PHI nodes being inserted for variables used
in multiple basic blocks, but they are not handled by this patch.

llvm-svn: 8881

do not support stack unwinding yet

llvm-svn: 8869

llvm-svn: 8868

llvm-svn: 8865

The VersionNumbers vector is only used during PHI placement.  Turn it into an argument, allowing us to get rid of the vector.

llvm-svn: 8864

*** Revamp the code which handled unreachable code in the function.  Now the
    code is much more efficient for high-degree basic blocks, such as those
    that occur in the 252.eon SPEC benchmark.

For the interested, the time to promote a SINGLE alloca in _ZN7mrScene4ReadERSi
function used to be > 3.5s.  Now it is < .075s.  The function has a LOT of
allocas in it, so it appeared to be infinite looping, this should make it much
nicer.  :)

llvm-svn: 8863

llvm-svn: 8862

work-list of value definitions.  This allows elimination of the explicit
'iterative' step of the algorithm, and also reuses temporary memory better.

llvm-svn: 8861

need to be an instance variable!

llvm-svn: 8860

* Fuse two parallel loops
* Use a more specific type for AllocaLookup

llvm-svn: 8859

 * Do not insert a new entry into NewPhiNodes during the rename pass if there are no PHIs in a block.
 * Do not compute WriteSets in parallel

llvm-svn: 8858

* Eliminate the KillList instance variable, instead, just delete loads and
  stores as they are "renamed", and delete allocas when they are done
* Make the 'visited' set an instance variable to avoid passing it on the stack.

llvm-svn: 8857

llvm-svn: 8817

llvm-svn: 8703

Isn't updating copy and pasted code a joy

llvm-svn: 8702

llvm-svn: 8689

llvm-svn: 8667

llvm-svn: 8666

... by making sure to update PHI nodes to take into consideration the
extra edges we get if we inline a call instruction through an invoke.

llvm-svn: 8664

llvm-svn: 8662

llvm-svn: 8661

llvm-svn: 8659

llvm-svn: 8632

llvm-svn: 8625

Rename Function::getEntryNode -> getEntryBlock

llvm-svn: 8623

llvm-svn: 8620

llvm-svn: 8619

llvm-svn: 8618

llvm-svn: 8607

llvm-svn: 8605

llvm-svn: 8604

Thanks to brg for tracking down the problem so precisely!

llvm-svn: 8568

in it being both shorter and more effective.  It no longer depends on the
callgraph, so one FIXME has been fixed.

Additionally, this pass was not able to delete recursive (but dead) functions
if they were pointed to by global variables which were also dead.  In fact
this pass had a lot of problems deleting functions which were only pointed
to by dead globals and other stuff.

Fixing this means that the entire EH library should be stripped away now from
programs that don't use sjlj or exceptions.

llvm-svn: 8567

was a "major hack"  :)

llvm-svn: 8524

contributed by the masterful Bill Wendling!

llvm-svn: 8520

llvm-svn: 8519

llvm-svn: 8516

llvm-svn: 8514