implement a nice little efficiency hack in the inliner.  Since we're now
running IPSCCP early, and we run functionattrs interlaced with the inliner,
we often (particularly for small or noop functions) completely propagate
all of the information about a call to its call site in IPSSCP (making a call
dead) and functionattrs is smart enough to realize that the function is
readonly (because it is interlaced with inliner).

To improve compile time and make the inliner threshold more accurate, realize
that we don't have to inline dead readonly function calls.  Instead, just
delete the call.  This happens all the time for C++ codes, here are some
counters from opt/llvm-ld counting the number of times calls were deleted vs
inlined on various apps:

Tramp3d opt:
  5033 inline                - Number of call sites deleted, not inlined
 24596 inline                - Number of functions inlined
llvm-ld:
  667 inline           - Number of functions deleted because all callers found
  699 inline           - Number of functions inlined

483.xalancbmk opt:
  8096 inline                - Number of call sites deleted, not inlined
 62528 inline                - Number of functions inlined
llvm-ld:
   217 inline           - Number of allocas merged together
  2158 inline           - Number of functions inlined

471.omnetpp:
  331 inline                - Number of call sites deleted, not inlined
 8981 inline                - Number of functions inlined
llvm-ld:
  171 inline           - Number of functions deleted because all callers found
  629 inline           - Number of functions inlined

Deleting a call is much faster than inlining it, and is insensitive to the
size of the callee. :)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86975 91177308-0d34-0410-b5e6-96231b3b80d8

RegScavenger::enterBasicBlock should always reset register state.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86972 91177308-0d34-0410-b5e6-96231b3b80d8

- Teach LSR to avoid changing cmp iv stride if it will create an immediate that
  cannot be folded into target cmp instruction.
- Avoid a phase ordering issue where early cmp optimization would prevent the
  later count-to-zero optimization.
- Add missing checks which could cause LSR to reuse stride that does not have
  users.
- Fix a bug in count-to-zero optimization code which failed to find the pre-inc
  iv's phi node.
- Remove, tighten, loosen some incorrect checks disable valid transformations.
- Quite a bit of code clean up.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86969 91177308-0d34-0410-b5e6-96231b3b80d8

Use table to separate opcode from operands.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86965 91177308-0d34-0410-b5e6-96231b3b80d8

isLegalICmpImmediate should take a signed integer; code clean up.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86964 91177308-0d34-0410-b5e6-96231b3b80d8

CMake: Hopefully unbreak the build by mimicking the changes on the
other build system about the new C_INCLUDE_DIRS configure option.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86960 91177308-0d34-0410-b5e6-96231b3b80d8

Add the --with-c-include-dirs to llvm's configure.
The clang patch is next.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86955 91177308-0d34-0410-b5e6-96231b3b80d8

CMake: Pass -lm to check_symbol_exists for detecting several math
functions like floorf, ceilf, ... Add test for detecting nearbyintf.

This change was prompted by test/Transforms/SimplifyLibCalls/floor.ll

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86954 91177308-0d34-0410-b5e6-96231b3b80d8

use getPredicateOnEdge to fold comparisons through PHI nodes,
which implements GCC PR18046.  This also gets us 360 more
jump threads on 176.gcc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86953 91177308-0d34-0410-b5e6-96231b3b80d8

various fixes to the lattice transfer functions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86952 91177308-0d34-0410-b5e6-96231b3b80d8

switch jump threading to use getPredicateOnEdge in one place
making the new LVI stuff smart enough to subsume some special
cases in the old code.  Disable them when LVI is around, the
testcase still passes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86951 91177308-0d34-0410-b5e6-96231b3b80d8

Add a new getPredicateOnEdge method which returns more rich information for
constant constraints.  Improve the LVI lattice to include inequality
constraints.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86950 91177308-0d34-0410-b5e6-96231b3b80d8

Move the utility function UpdateTerminator() from CodePlacementOpt() into
MachineBasicBlock so other passes can utilize it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86947 91177308-0d34-0410-b5e6-96231b3b80d8

Revert 86857. It's causing consumer-typeset to fail, and there's a better way to do it forthcoming anyway.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86945 91177308-0d34-0410-b5e6-96231b3b80d8

Use stubs when we have them, otherwise use code we already have,
otherwise create a stub.

Add a test to make sure we don't create extraneous stubs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86941 91177308-0d34-0410-b5e6-96231b3b80d8

Add the braces gcc suggested.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86933 91177308-0d34-0410-b5e6-96231b3b80d8

Add CreateNUWAdd and CreateNUWSub to complement the existing CreateNSWAdd and
CreateNSWSub functions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86930 91177308-0d34-0410-b5e6-96231b3b80d8

should not commit when distracted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86929 91177308-0d34-0410-b5e6-96231b3b80d8

Make the BranchFolderPass class local to BranchFolding.cpp.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86928 91177308-0d34-0410-b5e6-96231b3b80d8

We now thread some impossible condition information with LVI.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86927 91177308-0d34-0410-b5e6-96231b3b80d8

Minor code cleanups.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86926 91177308-0d34-0410-b5e6-96231b3b80d8

with the new code we can thread non-instruction values.  This
allows us to handle the test10 testcase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86924 91177308-0d34-0410-b5e6-96231b3b80d8

this argument can be an arbitrary value, it doesn't need to be an instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86923 91177308-0d34-0410-b5e6-96231b3b80d8

expose edge information and switch j-t to use it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86920 91177308-0d34-0410-b5e6-96231b3b80d8

Fixed an iteration condition in PreAllocSplitting. This should fix some miscompilations casued by PreAllocSplitting.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86919 91177308-0d34-0410-b5e6-96231b3b80d8

move some stuff into DEBUG's and turn on lazy-value-info for
the basic.ll testcase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86918 91177308-0d34-0410-b5e6-96231b3b80d8

Fix typo, cleanup whitespace.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86917 91177308-0d34-0410-b5e6-96231b3b80d8

Do not use StringRef in DebugInfo interface.
This allows StringRef to skip controversial if(str) check in constructor.
Buildbots, wait for corresponding clang and llvm-gcc FE check-ins!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86914 91177308-0d34-0410-b5e6-96231b3b80d8

Tail merge at any size when there are two potentials blocks and one
can be made to fall through into the other.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86909 91177308-0d34-0410-b5e6-96231b3b80d8

Don't mark a call as potentially throwing if the function it's calling has the
"nounwind" attribute.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86897 91177308-0d34-0410-b5e6-96231b3b80d8

A real solution for the first part of PR5445

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86895 91177308-0d34-0410-b5e6-96231b3b80d8

make LazyValueInfo actually to some stuff.  This isn't very tested but improves
strswitch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86889 91177308-0d34-0410-b5e6-96231b3b80d8

pass TD into a SimplifyCmpInst call.  Add another case that
uses LVI info when -enable-jump-threading-lvi is passed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86886 91177308-0d34-0410-b5e6-96231b3b80d8

Promote MergePotentialsElt and SameTailElt to be regular classes
instead of typedefs for std::pair. This simplifies the type of
SameTails, which previously was std::vector<std::pair<std::vector<std::pair<unsigned, MachineBasicBlock *> >::iterator, MachineBasicBlock::iterator>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86885 91177308-0d34-0410-b5e6-96231b3b80d8

x86 users can now return arbitrary sized structs.  Structs too large to fit in return registers will be returned through a hidden sret parameter introduced during SelectionDAG construction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86876 91177308-0d34-0410-b5e6-96231b3b80d8

Revert this line of 86871.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86875 91177308-0d34-0410-b5e6-96231b3b80d8

If doesSupportDebugInformation() is false then do not try to emit dwarf debug info.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86874 91177308-0d34-0410-b5e6-96231b3b80d8

Check in the changes to this file too.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86873 91177308-0d34-0410-b5e6-96231b3b80d8

Add support for tail duplication to BranchFolding, and extend
tail merging support to handle more cases.
 - Recognize several cases where tail merging is beneficial even when
   the tail size is smaller than the generic threshold.
 - Make use of MachineInstrDesc::isBarrier to help detect
   non-fallthrough blocks.
 - Check for and avoid disrupting fall-through edges in more cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86871 91177308-0d34-0410-b5e6-96231b3b80d8

Fix liveness calculation when splitting critical edges during PHI elimination.

- Edges are split before any phis are eliminated, so the code is SSA.

- Create a proper IR BasicBlock for the split edges.

- LiveVariables::addNewBlock now has same syntax as
  MachineDominatorTree::addNewBlock. Algorithm calculates predecessor live-out
  set rather than successor live-in set.

This feature still causes some miscompilations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86867 91177308-0d34-0410-b5e6-96231b3b80d8

Reenable StackTracke.cpp test.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86861 91177308-0d34-0410-b5e6-96231b3b80d8

Add SetDebugLocation() variant to
add debug info location to an instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86859 91177308-0d34-0410-b5e6-96231b3b80d8

Add TargetLowering::isLegalICmpImmediate. It tells LSR what immediate can be folded into target icmp instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86858 91177308-0d34-0410-b5e6-96231b3b80d8

Do jump table adjustment before constant island allocation

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86857 91177308-0d34-0410-b5e6-96231b3b80d8

Fix indentation level.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86856 91177308-0d34-0410-b5e6-96231b3b80d8

Whitespace cleanups.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86855 91177308-0d34-0410-b5e6-96231b3b80d8

Prefix MBB numbers with "BB#" in debug output to make it clear what
the numbers mean.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86854 91177308-0d34-0410-b5e6-96231b3b80d8

Minor code simplification.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86853 91177308-0d34-0410-b5e6-96231b3b80d8

Fix a copy+pasto in a comment.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86852 91177308-0d34-0410-b5e6-96231b3b80d8

Set isBarrier = 1 on return instructions, as they are control barriers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86851 91177308-0d34-0410-b5e6-96231b3b80d8

Use a tab in INT3's asm string, for consistency.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86850 91177308-0d34-0410-b5e6-96231b3b80d8

another const prop failure.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86848 91177308-0d34-0410-b5e6-96231b3b80d8

add a note

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86847 91177308-0d34-0410-b5e6-96231b3b80d8

Reject duplicate case values in a switch, PR5450.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86846 91177308-0d34-0410-b5e6-96231b3b80d8

Don't trivially delete unused calls to llvm.invariant.start.  This allows
llvm.invariant.start to be used without necessarily being paired with a call
to llvm.invariant.end.  If you run the entire optimization pipeline then such
calls are in fact deleted (adce does it), but that's actually a good thing since
we probably do want them to be zapped late in the game.  There should really be
an integration test that checks that the llvm.invariant.start call lasts long
enough that all passes that do interesting things with it get to do their stuff
before it is deleted.  But since no passes do anything interesting with it yet
this will have to wait for later.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86840 91177308-0d34-0410-b5e6-96231b3b80d8

Add nounwind.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86814 91177308-0d34-0410-b5e6-96231b3b80d8

remove the now dead condprop pass, PR3906.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86810 91177308-0d34-0410-b5e6-96231b3b80d8

Fix JITTest.ModuleDeletion in -Asserts mode (which turns off JITEmitDebugInfo
by default).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86807 91177308-0d34-0410-b5e6-96231b3b80d8

remove condprop testcases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86804 91177308-0d34-0410-b5e6-96231b3b80d8

Add StringRef::split(StringRef), to complement StringRef::split(char).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86803 91177308-0d34-0410-b5e6-96231b3b80d8

Remove dead code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86802 91177308-0d34-0410-b5e6-96231b3b80d8

Show command-line args and features passed into backend in debug output. Approved by Evan Cheng.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86797 91177308-0d34-0410-b5e6-96231b3b80d8

Add missing run line. Devang, please check.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86795 91177308-0d34-0410-b5e6-96231b3b80d8

Fix -Asserts warning.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86794 91177308-0d34-0410-b5e6-96231b3b80d8

The TBB and TBH instructions for Thumb2 are really handy for jump tables, but
can only branch forward. To best take advantage of them, we'd like to adjust
the basic blocks around a bit when reasonable. This patch puts basics in place
to do that, with a super-simple algorithm for backwards jump table targets that
creates a new branch after the jump table which branches backwards. Real
heuristics for reordering blocks or other modifications rather than inserting
branches will follow.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86791 91177308-0d34-0410-b5e6-96231b3b80d8

stub out some LazyValueInfo interfaces, and have JumpThreading
start using them in a trivial way when -enable-jump-threading-lvi
is passed.  enable-jump-threading-lvi will be my playground for
awhile.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86789 91177308-0d34-0410-b5e6-96231b3b80d8

Fix test to work on every platform.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86786 91177308-0d34-0410-b5e6-96231b3b80d8

Fix test to work on every platform.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86785 91177308-0d34-0410-b5e6-96231b3b80d8

XFAIL for now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86784 91177308-0d34-0410-b5e6-96231b3b80d8

Make sure that the exception handling data has the same visibility as the
function it's generated for.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86779 91177308-0d34-0410-b5e6-96231b3b80d8

Add Triple::str() which returns the contents of the Triple as a string, as a more readable alternative to getTriple().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86773 91177308-0d34-0410-b5e6-96231b3b80d8

Do not assume first function scope seen represents current function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86771 91177308-0d34-0410-b5e6-96231b3b80d8

Add From arguments to StringRef search functions, and tweak doxyments.

Also, add unittests for find_first_of and find_first_not_of.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86770 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-gcc/clang don't (won't?) need this hack.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86769 91177308-0d34-0410-b5e6-96231b3b80d8

oops, didn't mean to commit this, no harm, but add a todoops, didn't mean to commit this, no harm, but add a todoo

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86768 91177308-0d34-0410-b5e6-96231b3b80d8

Stub out a new lazy value info pass, which will eventually
vend value constraint information to the optimizer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86767 91177308-0d34-0410-b5e6-96231b3b80d8

add a fixme

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86766 91177308-0d34-0410-b5e6-96231b3b80d8

remove redundant foward declaration.  This function is already in
Analysis/Passes.h

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86765 91177308-0d34-0410-b5e6-96231b3b80d8

While creating DbgScopes, do not forget parent scope.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86763 91177308-0d34-0410-b5e6-96231b3b80d8

Block terminator may be a switch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86761 91177308-0d34-0410-b5e6-96231b3b80d8

jump threading does everything that condprop does any more.  This passes
bootstrap on darwin i386.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86758 91177308-0d34-0410-b5e6-96231b3b80d8

add a note

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86756 91177308-0d34-0410-b5e6-96231b3b80d8

I did this a week or two ago

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86754 91177308-0d34-0410-b5e6-96231b3b80d8

Ignore variable if scope info is not available.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86753 91177308-0d34-0410-b5e6-96231b3b80d8

Test this on Darwin only.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86752 91177308-0d34-0410-b5e6-96231b3b80d8

Emit correct code when making a ConstantPool entry for a vector
constant whose component type is not a legal type for the target.
(If the target ConstantPool cannot handle this type either, it has
an opportunity to merge elements.  In practice any target with
8-bit bytes must support i8 *as data*).  7320806 (partial).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86751 91177308-0d34-0410-b5e6-96231b3b80d8

Implement support to debug inlined functions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86748 91177308-0d34-0410-b5e6-96231b3b80d8

in -dot-cfg and -dot-cfg-only, when rendering switch instructions,
put the switch value in the successor boxes like we put T/F for branches.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86747 91177308-0d34-0410-b5e6-96231b3b80d8

implement a TODO by teaching jump threading about "xor x, 1".

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86739 91177308-0d34-0410-b5e6-96231b3b80d8

move some generally useful functions out of jump threading
into libanalysis and transformutils.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86735 91177308-0d34-0410-b5e6-96231b3b80d8

Don't mark conditional branch instructions as control barriers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86732 91177308-0d34-0410-b5e6-96231b3b80d8

Modify how the prologue encoded the "move" information for the FDE. GCC
generates a sequence similar to this:

__Z4funci:
LFB2:
        mflr r0
LCFI0:
        stmw r30,-8(r1)
LCFI1:
        stw r0,8(r1)
LCFI2:
        stwu r1,-80(r1)
LCFI3:
        mr r30,r1
LCFI4:

where LCFI3 and LCFI4 are used by the FDE to indicate what the FP, LR, and other
things are. We generated something more like this:

Leh_func_begin1:
        mflr r0
        stw r31, 20(r1)
        stw r0, 8(r1)
Llabel1:
        stwu r1, -80(r1)
Llabel2:
        mr r31, r1

Note that we are missing the "mr" instruction. This patch makes it more like the
GCC output.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86729 91177308-0d34-0410-b5e6-96231b3b80d8

Process InlinedAt location info.
Update InsertDeclare to return newly inserted llvm.dbg.declare intrinsic.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86727 91177308-0d34-0410-b5e6-96231b3b80d8

fix a crash in SCCP handling extractvalue of an array, pointed out and
tracked down by Stephan Reiter!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86726 91177308-0d34-0410-b5e6-96231b3b80d8

Teach PHIElimination to split critical edges when -split-phi-edges is enabled.

Critical edges leading to a PHI node are split when the PHI source variable is
live out from the predecessor block. This help the coalescer eliminate more
PHI joins.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86725 91177308-0d34-0410-b5e6-96231b3b80d8

Refactoring: Extract method PHIElimination::isLiveOut().
Clean up some whitespace.
No functional changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86724 91177308-0d34-0410-b5e6-96231b3b80d8

improve comment.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86723 91177308-0d34-0410-b5e6-96231b3b80d8

Make jump threading eliminate blocks that just contain phi nodes,
debug intrinsics, and an unconditional branch when possible.  This
reuses the TryToSimplifyUncondBranchFromEmptyBlock function split
out of simplifycfg.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86722 91177308-0d34-0410-b5e6-96231b3b80d8

Generalize lsr code that optimize loop to count down towards zero.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86715 91177308-0d34-0410-b5e6-96231b3b80d8

Optimize test more.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86714 91177308-0d34-0410-b5e6-96231b3b80d8