SLP Vectorier:  Don't vectorize really short chains because they are already handled by the SelectionDAG store-vectorizer, which does a better job in deciding when to vectorize.

llvm-svn: 187267

SLP Vectorizer: Disable the vectorization of non power of two chains, such as <3 x float>, because we dont have a good cost model for these types.

llvm-svn: 187265

llvm-svn: 187253

also worthwhile for it to look through FP extensions and truncations, whose
application commutes with fneg.

llvm-svn: 187249

llvm-svn: 187225

robust. It now uses an InstVisitor and worklist to actually walk the
uses of the Alloca transitively and detect the pattern which we can
directly promote: loads & stores of the whole alloca and instructions we
can completely ignore.

Also, with this new implementation teach both the predicate for testing
whether we can promote and the promotion engine itself to use the same
code so we no longer have strange divergence between the two code paths.

I've added some silly test cases to demonstrate that we can handle
slightly more degenerate code patterns now. See the below for why this
is even interesting.

Performance impact: roughly 1% regression in the performance of SROA or
ScalarRepl on a large C++-ish test case where most of the allocas are
basically ready for promotion. The reason is because of silly redundant
work that I've left FIXMEs for and which I'll address in the next
commit. I wanted to separate this commit as it changes the behavior.
Once the redundant work in removing the dead uses of the alloca is
fixed, this code appears to be faster than the old version. =]

So why is this useful? Because the previous requirement for promotion
required a *specific* visit pattern of the uses of the alloca to verify:
we *had* to look for no more than 1 intervening use. The end goal is to
have SROA automatically detect when an alloca is already promotable and
directly hand it to the mem2reg machinery rather than trying to
partition and rewrite it. This is a 25% or more performance improvement
for SROA, and a significant chunk of the delta between it and
ScalarRepl. To get there, we need to make mem2reg actually capable of
promoting allocas which *look* promotable to SROA without have SROA do
tons of work to massage the code into just the right form.

This is actually the tip of the iceberg. There are tremendous potential
savings we can realize here by de-duplicating work between mem2reg and
SROA.

llvm-svn: 187191

This patch provides basic support for powerpc64le as an LLVM target.
However, use of this target will not actually generate little-endian
code.  Instead, use of the target will cause the correct little-endian
built-in defines to be generated, so that code that tests for
__LITTLE_ENDIAN__, for example, will be correctly parsed for
syntax-only testing.  Code generation will otherwise be the same as
powerpc64 (big-endian), for now.

The patch leaves open the possibility of creating a little-endian
PowerPC64 back end, but there is no immediate intent to create such a
thing.

The LLVM portions of this patch simply add ppc64le coverage everywhere
that ppc64 coverage currently exists.  There is nothing of any import
worth testing until such time as little-endian code generation is
implemented.  In the corresponding Clang patch, there is a new test
case variant to ensure that correct built-in defines for little-endian
code are generated.

llvm-svn: 187179

The language reference says that:

"If a symbol appears in the @llvm.used list, then the compiler,
assembler, and linker are required to treat the symbol as if there is
a reference to the symbol that it cannot see"

Since even the linker cannot see the reference, we must assume that
the reference can be using the symbol table. For example, a user can add
__attribute__((used)) to a debug helper function like dump and use it from
a debugger.

llvm-svn: 187103

llvm-svn: 187099

Thanks to Nick Lewycky for noticing it.

llvm-svn: 187098

While there shrink a dangerously large SmallPtrSet.

llvm-svn: 187050

schedule an alloca for another iteration in SROA. This only showed up
with a mixture of promotable and unpromotable selects and phis. Added
a test case for this.

llvm-svn: 187031

pending speculation for a phi node. The problem here is that we were
using growth of the specluation set as an indicator of whether
speculation would occur, and if the phi node is already in the set we
don't see it grow. This is a symptom of the fact that this signal is
a total hack.

Unfortunately, I couldn't really come up with a non-hacky way of
signaling that promotion remains valid *after* speculation occurs, such
that we only speculate when all else looks good for promotion. In the
end, I went with at least a much more explicit approach of doing the
work of queuing inside the phi and select processing and setting
a preposterously named flag to convey that we're in the special state of
requiring speculating before promotion.

Thanks to Richard Trieu and Nick Lewycky for the excellent work reducing
a testcase for this from a pretty giant, nasty assert in a big
application. =] The testcase was excellent.

llvm-svn: 187029

llvm-svn: 186997

llvm-svn: 186893

llvm-svn: 186892

llvm-svn: 186890

When we vectorize across multiple basic blocks we may vectorize PHINodes that create a cycle. We already break the cycle on phi-nodes, but arithmetic operations are still uplicated. This patch adds code that checks if the operation that we are vectorizing was vectorized during the visit of the operands and uses this value if it can.

llvm-svn: 186883

llvm-svn: 186880

llvm-svn: 186877

llvm-svn: 186858

Fix an obvious typo in the loop vectorizer where the cost model uses the wrong variable. The variable BlockCost is ignored.
We don't have tests for the effect of if-conversion loops because it requires a big test (that includes if-converted loops) and it is difficult to find and balance a loop to do the right thing.

llvm-svn: 186845

llvm-svn: 186808

llvm-svn: 186790

to iterate over.

llvm-svn: 186788

llvm-svn: 186786

helper function. This leaves both trivial cases handled entirely in
helper functions and merely manages the list of allocas to process in
the run method.

The next step will be to handle all of the trivial promotion work prior
to even creating the core class and the subsequent simplifications that
enables.

llvm-svn: 186784

a single block into the helper routine. This takes advantage of the fact
that we can directly replace uses prior to any store with undef to
simplify matters and unconditionally promote allocas only used within
one block.

I've removed the special handling for the case of no stores existing.
This has no semantic effect but might slow things down. I'll fix that in
a later patch when I refactor this entire thing to be easier to manage
the different cases.

llvm-svn: 186783

llvm-svn: 186782

handles the general cases.

The hope is to refactor this so that we don't end up building the entire
class for the trivial cases. I also want to lift a lot of the early
pre-processing in the initial segment of run() into a separate routine,
and really none of it needs to happen inside the primary promotion
class.

These routines in particular used none of the actual state in the
promotion class, so they don't really make sense as members.

llvm-svn: 186781

This struct is nicely independent of everything else, and we already
needed a foward declaration here. It's simpler to just define it
immediately.

llvm-svn: 186780

llvm-svn: 186779

GlobalOpt simplifies llvm.compiler.used by removing any members that are also
in the more strict llvm.used. Handle the special case where llvm.compiler.used
becomes empty.

llvm-svn: 186778

that ensued from that.

llvm-svn: 186777

pattern and conform to the naming conventions.

llvm-svn: 186776

subsequent changes don't introduce inconsistencies.

llvm-svn: 186775

those baked into DenseMap now.

llvm-svn: 186773

functionality changed.

llvm-svn: 186772

While there replace an explicit struct with std::mem_fun.

llvm-svn: 186761

llvm-svn: 186759