Instead of parallelizing every parallel outermost loop, we now use a very
minimalistic cost model. Specifically, we assume innermost loops are not
worth parallelising and all non-innermost loops are.
When parallelizing all loops in LNT we got several slowdowns/timeouts due to
us parallelizing innermost loops that are executed only a couple of times
(number of iterations not known statically). With this basic heuristic enabled
LNT does not show any more timeouts, while several interesting loops are still
parallelized.
There are many ways to obtain an improved heuristic. Constructing such an
improvide heuristic from a position of minimal slow-down and zero code size
increase seems to be the best, as it allows us to track progress on LNT.
llvm-svn: 222096
We introduces a new flag -polly-parallel and use it to annotate the for-nodes in
the isl ast that we want to execute thread parallel (e.g., using OpenMP). We
previously already emmitted openmp annotations, but we did this for various
kinds of parallel loops, including some which we can not run in parallel.
With this patch we now have three annotations:
1) #pragma known-parallel [reduction]
2) #pragma omp for
3) #pragma simd
meaning:
1) loop has no loop carried dependences
2) loop will be executed thread-parallel
3) loop can possibly be vectorized
This patch introduces 1) and reduces the use of 2) to only the cases where we
will actually generate thread parallel code.
It is in preparation of openmp code generation in our isl backend.
Legacy:
- We also have a command line option -enable-polly-openmp. This option controls
the OpenMP code generation in CLooG. It will become an alias of
-polly-parallel after the CLooG code generation has been dropped.
http://reviews.llvm.org/D6142
llvm-svn: 221479
This makes sure we consistently use dbgs() when printing debug output.
Previously, the code just mixed calls to isl_*_dump() with printing to dbgs()
and was relying for both methods to interact in predictable ways (same output
stream, no unexpected reordering of outputs).
llvm-svn: 220443
This change will build all alias groups (minimal/maximal accesses
to possible aliasing base pointers) we have to check before
we can assume an alias free environment. It will also use these
to create Runtime Alias Checks (RTC) in the ISL code generation
backend, thus allow us to optimize SCoPs despite possibly aliasing
pointers when this backend is used.
This feature will be enabled for the isl code generator, e.g.,
--polly-code-generator=isl, but disabled for:
- The cloog code generator (still the default).
- The case delinearization is enabled.
- The case non-affine accesses are allowed.
llvm-svn: 218046
During the IslAst parallelism check also compute the minimal dependency
distance and store it in the IstAst for node.
Reviewer: sebpop
Differential Revision: http://reviews.llvm.org/D4987
llvm-svn: 217729
There was a bug in the IslAst which caused that no more outermost
parallel loops were detected/checked after a parallel outermost loop
of depth 1.
+ Test case attached
llvm-svn: 217452
+ Remove the class IslGenerator which duplicates the functionality of
IslExprBuilder.
+ Use the IslExprBuilder to create code for memory access relations.
+ Also handle array types during access creation.
+ Enable scev codegen for one of the transformed memory access tests,
thus access creation without canonical induction variables available.
+ Update one test case to the new output.
llvm-svn: 214659
+ Split all reduction dependences and map them to the causing memory accesses.
+ Print the types & base addresses of broken reductions for each "reduction
parallel" marked loop (OpenMP style).
+ 3 test cases to show how reductions are now represented in the isl ast.
The mapping "(ast) loops -> broken reductions" is also needed to find the
memory accesses we need to privatize in a loop.
llvm-svn: 214489
The functions isParallel, isInnermostParallel and IsOutermostParallel in
IslAstInfo will now return true even in the presence of broken reductions.
To compensate for this change the negated result of isReductionParallel can
be used.
llvm-svn: 214488
+ Perform the parallelism check on the innermost loop only once.
+ Inline the markOpenmpParallel function.
+ Rename all IslAstUserPayload * into Payload to make it consistent.
llvm-svn: 214448
Whe we build the IslAst we visit for nodes (in pre and post order) as well as
user/domain nodes. As these two sets are non overlapping we do not need to
check if we annotated a node earlier when we visit it.
llvm-svn: 214170
Use the fact that if we visit a for node first in pre and next in post order
we know we did not visit any children, thus we found an innermost loop.
+ Test case for an innermost loop with a conditional inside
llvm-svn: 213870
+ Renamed context into build when it's the isl_ast_build
+ Use the IslAstInfo functions to extract the schedule of a node
+ Use the IslAstInfo functions to extract the build/context of a node
+ Move the payload struct into the IslAstInfo class
+ Use a constructor and destructor (also new and delete) to
allocate/initialize the payload struct
llvm-svn: 213792
Offer the static functions to extract information out of an IslAst for node
as members of IslAstInfo not as top level entities.
+ Refactor common code
+ Add isParallel and isReductionParallel
+ Rename IslAstUser to IslAstUserPayload to make it clear this is just a (or
the) payload struct.
llvm-svn: 213272
+ Introduced dependency type TYPE_TC_RED to represent the transitive closure
(& the reverse) of reduction dependences. These are used when we check for
reduction parallel loops.
+ Test cases including loop reversals and modulo schedules which compute
reductions in a alternated order.
llvm-svn: 213019
As our delinearization works optimistically, we need in some cases run-time
checks that verify our optimistic assumptions. A simple example is the
following code:
void foo(long n, long m, long o, double A[n][m][o]) {
for (long i = 0; i < 100; i++)
for (long j = 0; j < 150; j++)
for (long k = 0; k < 200; k++)
A[i][j][k] = 1.0;
}
After clang linearized the access to A and we delinearized it again to
A[i][j][k] we need to ensure that we do not access the delinearized array
out of bounds (this information is not available in LLVM-IR). Hence, we
need to verify the following constraints at run-time:
CHECK: Assumed Context:
CHECK: [o, m] -> { : m >= 150 and o >= 200 }
llvm-svn: 212198
To translate the old induction variables as they exist before Polly to new
new induction variables introduced during AST code generation we need to
generate code that computes the new values from the old ones. We can do this
by just looking at the arguments isl generates in each scheduled statement.
Example:
// Old
for i
S(i)
// New
for c0
for c1
S(c0 + c1)
To get the value of i, we need to compute 'c0 + c1'. This expression is readily
available in the user statements generated by isl and just needs to be
translated to LLVM-IR.
This replaces an old confusing construct that constructed during ast generation
an isl multi affine expression that described this relation and which was then
again ast generated for each statement and argument when translating the isl ast
to LLVM-IR. This approach was difficult to understand and the additional ast
generation calls where entirely redundant as isl provides the relevant
expressions as arguments of the generated user statements.
llvm-svn: 212186
+ Collect reduction dependences
+ Introduced TYPE_RED in Dependences.h which can be used to obtain the
reduction dependences
+ Used TYPE_RED to prevent parallelization while we do not have a privatizing
code generation
+ Relax the dependences for non-parallel code generation
+ Add privatization dependences to ensure correctness
+ 12 Test cases to check for reduction and privatization dependences
llvm-svn: 211369
definition below all of the header #include lines, Polly edition.
If you want to know more details about this, you can see the recent
commits to Debug.h in LLVM. This is just the Polly segment of a cleanup
I'm doing globally for this macro.
llvm-svn: 206852
For complex examples it may happen that we do not compute dependences. In this
case we do not want to crash, but just not detect parallel loops.
llvm-svn: 204470
When constructing a scop sometimes the exact representation of a statement or
condition would be very complex, but there is a common case which is a lot
simpler, but which is only valid under certain assumptions. The assumed context
records the assumptions taken during the construction of this scop and that need
to be code generated as a run-time test.
At the moment, we do not yet model any assumptions, but only added the
AssumedContext as well as the isl-ast generation support. As a next step,
this needs to be hooked up with the isl code generation.
if (1) /* run-time condition */
{ /* optimized code */ }
else
{ /* original code */ }
llvm-svn: 193652
Use the new cl::OptionCategory support to move the Polly options into a separate
option category. The aim is to hide most options and show by default only the
options a user needs to influence '-O3 -polly'. The available options probably
need some care, but here is the current status:
Polly Options:
Configure the polly loop optimizer
-enable-polly-openmp - Generate OpenMP parallel code
-polly - Enable the polly optimizer (only at -O3)
-polly-no-tiling - Disable tiling in the scheduler
-polly-only-func=<function-name> - Only run on a single function
-polly-report - Print information about the activities
of Polly
-polly-vectorizer - Select the vectorization strategy
=none - No Vectorization
=polly - Polly internal vectorizer
=unroll-only - Only grouped unroll the vectorize
candidate loops
=bb - The Basic Block vectorizer driven by
Polly
llvm-svn: 181295
After this commit, polly is clang-format clean. This can be tested with
'ninja polly-check-format'. Updates to clang-format may change this, but the
differences will hopefully be both small and general improvements to the
formatting.
We currently have some not very nice formatting for a couple of items, DEBUG()
stmts for example. I believe the benefit of being clang-format clean outweights
the not perfect layout of this code.
llvm-svn: 177796
Recent changes in isl:
- Allow analysis of loops during code generation
This simplifies the detection of parallel loops.
- Simplify the way costumized ast printers are defined
This enables us to highlight parallel / vector loops in our debug output.
- Compile time improvements for codegen contexts that include parameters
- Various bug fixes
This update also gets us in sync for the isl 0.11 release.
llvm-svn: 169100
This change ensures that isl is only detected if it includes code generation
support. This allows us to remove a lot of conditional compilation and also
avoids missing test cases in case the feature is not available.
llvm-svn: 166403
Tobias Grosser