Two changes: Make getDependency remove QueryInst for a dirty record's
ReverseLocalDeps when we update it.  This fixes a regression test
failure from my last commit.

Second, for each non-local cached information structure, keep a bit that
indicates whether it is dirty or not.  This saves us a scan over the whole
thing in the common case when it isn't dirty.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60274 91177308-0d34-0410-b5e6-96231b3b80d8

Fix a link issue I ran into trying compiling LLVM on MinGW with CMake.
Hopefully this doesn't break anyone else's build... it shouldn't unless
the MinGW variable means something other than compiling with MinGW.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60273 91177308-0d34-0410-b5e6-96231b3b80d8

introduce a typedef, no functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60272 91177308-0d34-0410-b5e6-96231b3b80d8

Change NonLocalDeps to be a densemap of pointers to densemap
instead of containing them by value.  This increases the density
(!) of NonLocalDeps as well as making the reallocation case
faster.  This speeds up gvn on 403.gcc by 2% and makes room for
future improvements.

I'm not super thrilled with having to explicitly manage the new/delete
of the map, but it is necesary for the next change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60271 91177308-0d34-0410-b5e6-96231b3b80d8

calls never depend on allocations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60268 91177308-0d34-0410-b5e6-96231b3b80d8

Fix a fixme by making memdep's handling of allocations more logical.
If we see that a load depends on the allocation of its memory with no
intervening stores, we now return a 'None' depedency instead of "Normal".
This tweaks GVN to do its optimization with the new result.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60267 91177308-0d34-0410-b5e6-96231b3b80d8

implement a fixme by introducing a new getDependencyFromInternal
method that returns its result as a DepResultTy instead of as a
MemDepResult.  This reduces conversion back and forth.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60266 91177308-0d34-0410-b5e6-96231b3b80d8

Move the getNonLocalDependency method to a more logical place in
the file, no functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60265 91177308-0d34-0410-b5e6-96231b3b80d8

REmove an old fixme, resolve another fixme by adding liberal
comments about what this class does.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60264 91177308-0d34-0410-b5e6-96231b3b80d8

remove a bit of incorrect code that tried to be tricky about speeding up
dependencies.  The basic situation was this: consider if we had:

  store1
  ...
  store2
  ...
  store3

Where memdep thinks that store3 depends on store2 and store2 depends
on store1.  The problem happens when we delete store2: The code in
question was updating dep info for store3 to be store1.  This is a
spiffy optimization, but is not safe at all, because aliasing isn't
transitive.  This bug isn't exposed today with DSE because DSE will only
zap store2 if it is identifical to store 3, and in this case, it is
safe to update it to depend on store1.  However, memcpyopt is not so
fortunate, which is presumably why the "dropInstruction" code used to
exist.

Since this doesn't actually provide a speedup in practice, just rip the
code out.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60263 91177308-0d34-0410-b5e6-96231b3b80d8

fix indentation.  std::pair is "isPod" if the first/second are both isPod.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60262 91177308-0d34-0410-b5e6-96231b3b80d8

Remove warning about declaration does not declare anything. This class was
already declared in the other headers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60261 91177308-0d34-0410-b5e6-96231b3b80d8

Eliminate the dropInstruction method, which is not needed any more.
Fix a subtle iterator invalidation bug I introduced in the last commit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60258 91177308-0d34-0410-b5e6-96231b3b80d8

Add protected visibility to libLTO.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60257 91177308-0d34-0410-b5e6-96231b3b80d8

implement some fixme's: when deleting an instruction with
an entry in the nonlocal deps map, don't reset entries
referencing that instruction to [dirty, null], instead, set
them to [dirty,next] where next is the instruction after the
deleted one.  Use this information in the non-local deps
code to avoid rescanning entire blocks.

This speeds up GVN slightly by avoiding pointless work.  On
403.gcc this makes GVN 1.5% faster.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60256 91177308-0d34-0410-b5e6-96231b3b80d8

Change MemDep::getNonLocalDependency to return its results as
a smallvector instead of a DenseMap.  This speeds up GVN by 5%
on 403.gcc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60255 91177308-0d34-0410-b5e6-96231b3b80d8

move MemoryDependenceAnalysis::verifyRemoved to the end of the file,
no functionality/code change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60254 91177308-0d34-0410-b5e6-96231b3b80d8

reimplement getNonLocalDependency with a simpler worklist
formulation that is faster and doesn't require nonLazyHelper.
Much less code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60253 91177308-0d34-0410-b5e6-96231b3b80d8

don't require GVN to work on dead values, just make the
test return the loaded value.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60252 91177308-0d34-0410-b5e6-96231b3b80d8

Fix a thinko that manifested as a crash on clamav last night.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60251 91177308-0d34-0410-b5e6-96231b3b80d8

Fix spelling mistake.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60250 91177308-0d34-0410-b5e6-96231b3b80d8

tidy up some variable names.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60243 91177308-0d34-0410-b5e6-96231b3b80d8

rename some maps.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60242 91177308-0d34-0410-b5e6-96231b3b80d8

rename some variables.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60241 91177308-0d34-0410-b5e6-96231b3b80d8

eliminate a bunch of code in favor of using AliasAnalysis::getModRefInfo.
Put a some code back to handle buggy behavior that GVN expects: it wants
loads to depend on each other, and accesses to depend on their allocations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60240 91177308-0d34-0410-b5e6-96231b3b80d8

protect against negative values that would exceed allowed bit width

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60239 91177308-0d34-0410-b5e6-96231b3b80d8

simplify some code and rename some variables.  Reduce nesting.
Use getTypeStoreSize instead of ABITypeSize for in-memory size
in a couple places.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60238 91177308-0d34-0410-b5e6-96231b3b80d8

apparently GCC doesn't believe that I understand C
precedence rules.  Pacify it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60237 91177308-0d34-0410-b5e6-96231b3b80d8

Typo fix.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60236 91177308-0d34-0410-b5e6-96231b3b80d8

Split getDependency into getDependency and getDependencyFrom, the
former does caching, the later doesn't.  This dramatically simplifies
the logic in getDependency and getDependencyFrom.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60234 91177308-0d34-0410-b5e6-96231b3b80d8

Temporarily revert r60195. It's causing an optimized bootstrap of llvm-gcc to fail.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60233 91177308-0d34-0410-b5e6-96231b3b80d8

Now that DepType is private, we can start cleaning up some of its uses:
Document the Dirty value more precisely, use it for the uninitialized
DepResultTy value.  Change reverse mappings to be from an instruction*
instead of DepResultTy, and stop tracking other forms.  This makes it more
clear that we only care about the instruction cases.

Eliminate a DepResultTy,bool pair by using Dirty in the local case as well,
shrinking the map and simplifying the code.

This speeds up GVN by ~3% on 403.gcc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60232 91177308-0d34-0410-b5e6-96231b3b80d8

Introduce and use a new MemDepResult class to hold the results of a memdep
query.  This makes it crystal clear what cases can escape from MemDep that
the clients have to handle.  This also gives the clients a nice simplified
interface to it that is easy to poke at.

This patch also makes DepResultTy and MemoryDependenceAnalysis::DepType
private, yay.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60231 91177308-0d34-0410-b5e6-96231b3b80d8

Reimplement the internal abstraction used by MemDep in terms
of a pointer/int pair instead of a manually bitmangled pointer.
This forces clients to think a little more about checking the
appropriate pieces and will be useful for internal
implementation improvements later.

I'm not particularly happy with this.  After going through this
I don't think that the clients of memdep should be exposed to
the internal type at all.  I'll fix this in a subsequent commit.

This has no functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60230 91177308-0d34-0410-b5e6-96231b3b80d8

Fix sentinels to use correctly 'aligned' pointers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60229 91177308-0d34-0410-b5e6-96231b3b80d8

Fix spello, add DenseMapInfo specialization for PointerIntPair.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60228 91177308-0d34-0410-b5e6-96231b3b80d8

fix comment typo

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60227 91177308-0d34-0410-b5e6-96231b3b80d8

fix a bug.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60225 91177308-0d34-0410-b5e6-96231b3b80d8

add a generic "bitmangled pointer" class, which allows a parameterized
pointer and integer type to be used.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60224 91177308-0d34-0410-b5e6-96231b3b80d8

Fix PR3141 by ensuring that MemoryDependenceAnalysis::removeInstruction
properly updates the reverse dependency map when it installs updated
dependencies for instructions that depend on the removed instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60222 91177308-0d34-0410-b5e6-96231b3b80d8

don't revisit instructions off the beginning of the block.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60221 91177308-0d34-0410-b5e6-96231b3b80d8

comment cleanups.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60220 91177308-0d34-0410-b5e6-96231b3b80d8

more cleanups for MemoryDependenceAnalysis::removeInstruction,
no functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60219 91177308-0d34-0410-b5e6-96231b3b80d8

random cleanups, no functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60218 91177308-0d34-0410-b5e6-96231b3b80d8

forward declare CallSite instead of #includ'ing it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60217 91177308-0d34-0410-b5e6-96231b3b80d8

Run verifyRemoved from removeInstruction when -debug is specified.
This shows the root problem behind PR3141.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60216 91177308-0d34-0410-b5e6-96231b3b80d8

rename "ping" to "verifyRemoved".  I don't know why 'ping' what chosen,
but it doesn't make any sense at all.

Also make the method const, private, and fit in 80 cols while we're at it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60215 91177308-0d34-0410-b5e6-96231b3b80d8

comment and indentation improvements.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60214 91177308-0d34-0410-b5e6-96231b3b80d8

simplify some code, remove escaped newline.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60213 91177308-0d34-0410-b5e6-96231b3b80d8

remove mysterious escaped newlines.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60211 91177308-0d34-0410-b5e6-96231b3b80d8

don't call MergeBasicBlockIntoOnlyPred on a block whose only
predecessor is itself.  This doesn't make sense, and this is
a dead infinite loop anyway.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60210 91177308-0d34-0410-b5e6-96231b3b80d8

Add include files needed when building with
gcc 4.4 (due to use of sprintf).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60209 91177308-0d34-0410-b5e6-96231b3b80d8

Fix build with gcc-4.4: it doesn't like PICStyle
being both a namespace and a variable name.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60208 91177308-0d34-0410-b5e6-96231b3b80d8

rewrite RecursivelyDeleteTriviallyDeadInstructions to use a more efficient
formulation that doesn't require set lookups or scanning a set.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60203 91177308-0d34-0410-b5e6-96231b3b80d8

remove some weirdness that came from the LSR code that has
nothing to do with dead instruction elimination.  No tests in
dejagnu depend on this, so I don't know what it was needed for.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60202 91177308-0d34-0410-b5e6-96231b3b80d8

rewrite a big chunk of how DSE does recursive dead operand
elimination to use more modern infrastructure.  Also do a bunch
of small cleanups.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60201 91177308-0d34-0410-b5e6-96231b3b80d8

Scrap some boilerplate.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60200 91177308-0d34-0410-b5e6-96231b3b80d8

Support multiple compilation graph definitions. Not terribly useful, but makes the code more generic.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60199 91177308-0d34-0410-b5e6-96231b3b80d8

Add 'hidden' and 'really_hidden' option properties.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60198 91177308-0d34-0410-b5e6-96231b3b80d8

Documentation: clarify what is meant by 'multiple edges'.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60197 91177308-0d34-0410-b5e6-96231b3b80d8

delete ErasePossiblyDeadInstructionTree, replacing uses of it with
RecursivelyDeleteTriviallyDeadInstructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60196 91177308-0d34-0410-b5e6-96231b3b80d8

Simplify LoopStrengthReduce::DeleteTriviallyDeadInstructions by
making it use RecursivelyDeleteTriviallyDeadInstructions to do
the heavy lifting.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60195 91177308-0d34-0410-b5e6-96231b3b80d8

enhance RecursivelyDeleteTriviallyDeadInstructions to make
PHIs dead if they are single-value.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60194 91177308-0d34-0410-b5e6-96231b3b80d8

Enhance RecursivelyDeleteTriviallyDeadInstructions to optionally
return a list of deleted instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60193 91177308-0d34-0410-b5e6-96231b3b80d8

use continue to reduce indentation

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60192 91177308-0d34-0410-b5e6-96231b3b80d8

remove doConstantPropagation and dceInstruction, they are just
wrappers around the interesting code and use an obscure iterator
abstraction that dates back many many years.

Move EraseDeadInstructions to Transforms/Utils and name it
RecursivelyDeleteTriviallyDeadInstructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60191 91177308-0d34-0410-b5e6-96231b3b80d8

simplify code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60190 91177308-0d34-0410-b5e6-96231b3b80d8

simplify this logic.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60189 91177308-0d34-0410-b5e6-96231b3b80d8

Also update the README.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60188 91177308-0d34-0410-b5e6-96231b3b80d8

Chris prefers icmp/select over udiv!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60187 91177308-0d34-0410-b5e6-96231b3b80d8

Add a synthetic missed optimization.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60186 91177308-0d34-0410-b5e6-96231b3b80d8

Add a couple of missed optimizations on integer vectors. Multiply and divide
by 1, as well as multiply by -1.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60182 91177308-0d34-0410-b5e6-96231b3b80d8

defensive patch: if CGP is merging a block with the entry block, make sure
it ends up being the entry block.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60180 91177308-0d34-0410-b5e6-96231b3b80d8

Fix PR3138: if we merge the entry block into another block, make sure to
move the other block back up into the entry position!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60179 91177308-0d34-0410-b5e6-96231b3b80d8

Silence a warning.

Despite changing the order of evaluation, this doesn't actually change the
meaning of the statement.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60177 91177308-0d34-0410-b5e6-96231b3b80d8

fix build on some machines. thanks buildbot

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60175 91177308-0d34-0410-b5e6-96231b3b80d8

fix my previous commit r60064: compare strings instead of pointers

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60174 91177308-0d34-0410-b5e6-96231b3b80d8

switch InstCombine::visitLoadInst to use
FindAvailableLoadedValue

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60169 91177308-0d34-0410-b5e6-96231b3b80d8

improve const correctness.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60168 91177308-0d34-0410-b5e6-96231b3b80d8

enhance FindAvailableLoadedValue to make use of AliasAnalysis
if it has it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60167 91177308-0d34-0410-b5e6-96231b3b80d8

move FindAvailableLoadedValue from JumpThreading to Transforms/Utils.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60166 91177308-0d34-0410-b5e6-96231b3b80d8

Get rid of bogus "control may reach end of non-void function ‘...’ being
inlined" message.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60165 91177308-0d34-0410-b5e6-96231b3b80d8

simplify this code a bit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60164 91177308-0d34-0410-b5e6-96231b3b80d8

Use the new MergeBasicBlockIntoOnlyPred function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60163 91177308-0d34-0410-b5e6-96231b3b80d8

move MergeBasicBlockIntoOnlyPred to Transforms/Utils.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60162 91177308-0d34-0410-b5e6-96231b3b80d8

XFAil test due to reverting of patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60161 91177308-0d34-0410-b5e6-96231b3b80d8

rename ThreadBlock to ProcessBlock, since it does other things than
just simple threading.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60157 91177308-0d34-0410-b5e6-96231b3b80d8

Comment out code that isn't entirely correct.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60156 91177308-0d34-0410-b5e6-96231b3b80d8

Fixed HTML closing tag, cleaned up some spacing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60153 91177308-0d34-0410-b5e6-96231b3b80d8

Removing redundant semicolons. No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60149 91177308-0d34-0410-b5e6-96231b3b80d8

Make jump threading substantially more powerful, in the following ways:

1. Make it fold blocks separated by an unconditional branch.  This enables
   jump threading to see a broader scope.
2. Make jump threading able to eliminate locally redundant loads when they
   feed the branch condition of a block.  This frequently occurs due to
   reg2mem running.
3. Make jump threading able to eliminate *partially redundant* loads when
   they feed the branch condition of a block.  This is common in code with
   lots of loads and stores like C++ code and 255.vortex.

This implements thread-loads.ll and rdar://6402033.

Per the fixme's, several pieces of this should be moved into Transforms/Utils.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60148 91177308-0d34-0410-b5e6-96231b3b80d8

Eliminate a compile time warning.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60145 91177308-0d34-0410-b5e6-96231b3b80d8

Avoid inserting noop's in the middle of a loop.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60141 91177308-0d34-0410-b5e6-96231b3b80d8

On x86 favors folding short immediate into some arithmetic operations (e.g. add, and, xor, etc.) because materializing an immediate in a register is expensive in turns of code size.
e.g.
movl 4(%esp), %eax
addl $4, %eax

is 2 bytes shorter than

movl $4, %eax
addl 4(%esp), %eax

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60139 91177308-0d34-0410-b5e6-96231b3b80d8

Add a missing case in visitADD.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60137 91177308-0d34-0410-b5e6-96231b3b80d8

Add -march=x86.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60135 91177308-0d34-0410-b5e6-96231b3b80d8

Add typedef to StringMapEntry.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60134 91177308-0d34-0410-b5e6-96231b3b80d8

Disallow multiple edges.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60127 91177308-0d34-0410-b5e6-96231b3b80d8

Add x86-specific test for add-with-overflow intrinsics.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60125 91177308-0d34-0410-b5e6-96231b3b80d8

Generate something sensible for an [SU]ADDO op when the overflow/carry flag is
the conditional for the BRCOND statement. For instance, it will generate:

    addl %eax, %ecx
    jo LOF

instead of

    addl %eax, %ecx
    ; About 10 instructions to compare the signs of LHS, RHS, and sum.
    jl LOF

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60123 91177308-0d34-0410-b5e6-96231b3b80d8