This option allows the user to provide additional information about parameter
values as an isl_set. To specify that N has the value 1024, we can provide
the context -polly-context='[N] -> {: N = 1024}'.
llvm-svn: 245175
This change extends the BlockGenerator to not only allow Instructions as
base elements of scalar dependences, but any llvm::Value. This allows
us to code-generate scalar dependences which reference function arguments, as
they arise when moddeling read-only scalar dependences.
llvm-svn: 244874
Before we only modeled PHI nodes if at least one incoming basic block was itself
part of the region, now we always model them except if all of their operands are
part of a single non-affine subregion which we model as a black-box.
This change only affects PHI nodes in the entry block, that have exactly one
incoming edge. Before this change, we did not model them and as a result code
generation would not know how to code generate them. With this change, code
generation can code generate them like any other PHI node.
This issue was exposed by r244606. Before this change simplifyRegion would have
moved these PHI nodes out of the SCoP, so we would never have tried to code
generate them. We could implement this behavior again, but changing the IR
after the scop has been modeled and transformed always adds a risk of us
invalidating earlier analysis results. It seems more save and overall also more
consistent to just model and handle this one-entry-edge PHI nodes like any
other PHI node in the scop.
Solution proposed by: Michael Kruse <llvm@meinersbur.de>
llvm-svn: 244721
This one was extracted from the test-suite's pifft and caused a
miscompilation because a scalar was not written to its alloca address.
llvm-svn: 244720
The previous code had several problems:
For newly created BasicBlocks it did not (always) call RegionInfo::setRegionFor in order to update its analysis. At the moment RegionInfo does not verify its BBMap, but will in the future. This is fixed by determining the region new BBs belong to and set it accordingly. The new executeScopConditionally() requires accurate getRegionFor information.
Which block is created by SplitEdge depends on the incoming and outgoing edges of the blocks it connects, which makes handling its output more difficult than it needs to be. Especially for finding which block has been created an to assign a region to it for the setRegionFor problem above. This patch uses an implementation for splitEdge that always creates a block between the predecessor and successor. simplifyRegion has also been simplified by using SplitBlockPredecessors instead of SplitEdge. Isolating the entries and exits have been refectored into individual functions.
Previously simplifyRegion did more than just ensuring that there is only one entering and one exiting edge. It ensured that the entering block had no other outgoing edge which was necessary for executeScopConditionally(). Now the latter uses the alternative splitEdge implementation which can handle this situation so simplifyRegion really only needs to simplify the region.
Also, executeScopConditionally assumed that there can be no PHI nodes in blocks with one incoming edge. This is wrong and LCSSA deliberately produces such edges. However, previous passes ensured that there can be no such PHIs in exit nodes, but which will no longer hold in the future.
The new code that the property that it preserves the identity of region block (the property that the memory address of the BasicBlock containing the instructions remains the same; new blocks only contain PHI nodes and a terminator), especially the entry block. As a result, there is no need to update the reference to the BasicBlock of ScopStmt that contain its instructions because they have been moved to other basic blocks.
Reviewers: grosser
Part of Differential Revision: http://reviews.llvm.org/D11867
llvm-svn: 244606
Besides other changes this version of isl contains a fundamental fix to memory
corruption issues we have seen with imath-32 backed isl_ints.
This update also contains a fix that ensures that the schedule-tree based
version of isl's dependence analysis takes the domain of the schedule into
account.
llvm-svn: 244585
Even though read-only accesses to scalars outside of a scop do not need to be
modeled to derive valid transformations or to generate valid sequential code,
but information about them is useful when we considering memory footprint
analysis and/or kernel offloading.
llvm-svn: 243981
We use the branch instruction as the location at which a PHI-node write takes
place, instead of the PHI-node itself. This allows us to identify the
basic-block in a region statement which is on the incoming edge of the PHI-node
and for which the write access was originally introduced. As a result we can,
during code generation, avoid generating PHI-node write accesses for basic
blocks that do not preceed the PHI node without having to look at the IR
again.
This change fixes a bug which was introduced in r243420, when we started to
explicitly model PHI-node reads and writes, but dropped some additional checks
that where still necessary during code generation to not emit PHI-node writes
for basic-blocks that are not on incoming edges of the original PHI node.
Compared to the code before r243420 the new code does not need to inspect the IR
any more and we also do not generate multiple redundant writes.
llvm-svn: 243852
The schedule map we derive from a schedule tree map may map statements into
schedule spaces of different dimensionality. This change adds zero padding
to ensure just a single schedule space is used and the translation from
a union_map to an isl_multi_union_pw_aff does not fail.
llvm-svn: 243849
SCEVExpander, which we are using during code generation, only allows
instructions as insert locations, but breaks in case BasicBlock->end() iterators
are passed to it due to it trying to obtain the basic block in which code should
be generated by calling Instruction->getParent(), which is not defined for
->end() iterators.
This change adds an assert to Polly that ensures we only pass valid instructions
to SCEVExpander and it fixes one case, where we used IRBuilder->SetInsertBlock()
to set an ->end() insert location which was later passed to SCEVExpander.
In general, Polly is always trying to build up the CFG first, before we actually
insert instructions into the CFG sceleton. As a result, each basic block should
already have at least one branch instruction before we start adding code. Hence,
always requiring the IRBuilder insert location to be set to a real instruction
should always be possible.
Thanks Utpal Bora <cs14mtech11017@iith.ac.in> for his help with test case
reduction.
llvm-svn: 243830
Such codes are not interesting to optimize and most likely never appear in the
normal compilation flow. However, they show up during test case reduction with
bugpoint and trigger -- without this change -- an assert in
polly::MemoryAccess::foldAccess(). It is better to detect them in
ScopDetection itself and just bail out.
Contributed-by: Utpal Bora <cs14mtech11017@iith.ac.in>
Reviewers: grosser
Subscribers: pollydev, llvm-commits
Differential Revision: http://reviews.llvm.org/D11425
llvm-svn: 243515
Schedule trees are a lot easier to work with, for both humans and machines. For
humans the more structured schedule representation is easier to reason about.
Together with the more abstract isl programming interface this can result in a
lot cleaner code (see this changeset). For machines, the structured schedule and
the fact that we now use explicit piecewise affine expressions instead of
integer maps makes it easier to generate code from this schedule tree. As a
result, we can already see a slight compile-time improvement -- for 3mm from
0m0.593s to 0m0.551s seconds (-7 %). More importantly, future optimizations such
as full-partial tile separation will most likely result in more streamlined code
to be generated.
Contributed-by: Roman Gareev <gareevroman@gmail.com>
llvm-svn: 243458
Summary:
When translating PHI nodes into memory dependences during code generation we
require two kinds of memory. 'Normal memory' as for all scalar dependences and
'PHI node memory' to store the incoming values of the PHI node. With this
patch we now mark and track these two kinds of memories, which we previously
incorrectly marked as a single memory object.
Being aware of PHI node storage makes code generation easier, as we do not need
to guess what kind of storage a scalar reference requires. This simplifies the
code nicely.
Reviewers: jdoerfert
Subscribers: pollydev, llvm-commits
Differential Revision: http://reviews.llvm.org/D11554
llvm-svn: 243420
These test cases check whether Polly still gives the same results if
LICM runs before. Currently, it does not and therefore these cases are
expected fails.
llvm-svn: 243037
As specified in PR23888, run-time alias check generation is expensive
in terms of compile-time. This reduces the compile time by computing
minimal/maximal access only once for each base pointer
Contributed-by: Pratik Bhatu <cs12b1010@iith.ac.in>
llvm-svn: 243024
Put all Polly targets into a single "Polly" category (i.e.
solution folder). Previously there was no recognizable scheme and most
categories contained just one or two targets or targets didn't belong
to any category.
Reviewers: grosser
llvm-svn: 242779
Instead of flat schedules, we now use so-called schedule trees to represent the
execution order of the statements in a SCoP. Schedule trees make it a lot easier
to analyze, understand and modify properties of a schedule, as specific nodes
in the tree can be choosen and possibly replaced.
This patch does not yet fully move our DependenceInfo pass to schedule trees,
as some additional performance analysis is needed here. (In general schedule
trees should be faster in compile-time, as the more structured representation
is generally easier to analyze and work with). We also can not yet perform the
reduction analysis on schedule trees.
For more information regarding schedule trees, please see Section 6 of
https://lirias.kuleuven.be/handle/123456789/497238
llvm-svn: 242130
Named isl sets can generally have any name if they remain within Polly, but only
certain strings can be parsed by isl. The new names we create ensure that we
can always copy-past isl strings from Polly to other isl tools, e.g. for
debugging.
llvm-svn: 241787
This is very preliminary support, but it seems to work for the most common case.
When observing more/different test cases, we can work on generalizing this.
llvm-svn: 240955
This removes old code that has been disabled since several weeks and was hidden
behind the flags -disable-polly-intra-scop-scalar-to-array=false and
-polly-model-phi-nodes=false. Earlier, Polly used to translate scalars and
PHI nodes to single element arrays, as this avoided the need for their special
handling in Polly. With Johannes' patches adding native support for such scalar
references to Polly, this code is not needed any more. After this commit both
-polly-prepare and -polly-independent are now mostly no-ops. Only a couple of
simple transformations still remain, but they are scheduled for removal too.
Thanks again to Johannes Doerfert for his nice work in making all this code
obsolete.
llvm-svn: 240766
Remainder operations with constant divisor can be modeled as quasi-affine
expression. This patch adds support for detecting and modeling them. We also
add a test that ensures they are correctly code generated.
This patch was extracted from a larger patch contributed by Johannes Doerfert
in http://reviews.llvm.org/D5293
llvm-svn: 240518
This makes the test cases nonaffine even if Polly some days gains support for
the srem instruction, an instruction which is currently not modeled but which
can clearly be modeled statically. A call to a function without definition
will always remain non-affine, as there is just insufficient static information
for it to be modeled more precisely.
llvm-svn: 240458
LLVM's instcombine already translates power-of-two sdivs that are known to be
exact to fast ashr instructions. Hence, there is no need to add this logic
ourselves.
Pointed-out-by: Johannes Doerfert
llvm-svn: 239025
We now verify that memory access functions imported via JSON are indeed defined
for the full iteration domain. Before this change we accidentally imported
memory mappings such as i -> i / 127, which only defined a mapped for values of
i that are evenly divisible by 127, but which did not define any mapping for the
remaining values, with the result that isl just generated an access expression
that had undefined behavior for all the unmapped values.
In the incorrect test cases, we now either use floor(i/127) or we use p/127 and
provide the information that p is indeed a multiple of 127.
llvm-svn: 239024
isl marks known non-negative numerators in modulo (and soon also division)
operations. We now exploit this by generating unsigned operations. This is
beneficial as unsigned operations with power-of-two denominators will be
translated by isl to fast bitshift or bitwise and operations.
llvm-svn: 238577
While looking through the test cases I realized we did not have a CHECK line
for a duplicate memory access which we may want to eliminate later. To ensure
we do not have (or later introduce) unnecessary memory accesses, we now tighten
the test cases to look for such a pattern (and add the CHECK: line that shows
the redundant memory access).
llvm-svn: 238227
This ensures we pass all tests independently of how we set the options
-disable-polly-intra-scop-scalar-to-array and -polly-model-phi-nodes.
(At least if we enable both or disable both. Enabling them individually makes
little sense, as they will hopefully disappear soon anyhow).
llvm-svn: 238087
To reduce compile time and to allow more and better quality SCoPs in
the long run we introduced scalar dependences and PHI-modeling. This
patch will now allow us to generate code if one or both of those
options are set. While the principle of demoting scalars as well as
PHIs to memory in order to communicate their value stays the same,
this allows to delay the demotion till the very end (the actual code
generation). Consequently:
- We __almost__ do not modify the code if we do not generate code
for an optimized SCoP in the end. Thus, the early exit as well as
the unprofitable option will now actually preven us from
introducing regressions in case we will probably not get better
code.
- Polly can be used as a "pure" analyzer tool as long as the code
generator is set to none.
- The original SCoP is almost not touched when the optimized version
is placed next to it. Runtime regressions if the runtime checks
chooses the original are not to be expected and later
optimizations do not need to revert the demotion for that part.
- We will generate direct accesses to the demoted values, thus there
are no "trivial GEPs" that select the first element of a scalar we
demoted and treated as an array.
Differential Revision: http://reviews.llvm.org/D7513
llvm-svn: 238070
Being here, we extend the interface to return the element type and not a pointer
to the element type. We also provide a function to get the size (in bytes) of
the elements stored in this array.
We currently still store the element size as an innermost dimension in
ScopArrayInfo, which is somehow inconsistent and should be addressed in future
patches.
llvm-svn: 237779
Modified two test cases to adjust to the above change in renaming.
These two files were causing the buildbot failure in Polly, #30204 for example.
Details in http://reviews.llvm.org/D9483
This checkin goes with r237150 and r237151
llvm-svn: 237203
Besides class, function and file names, we also change the command line option
from -polly-codegen-isl to just -polly-codegen. The isl postfix is a leftover
from the times when we still had the CLooG based -polly-codegen. Today it is
just redundant and we drop it.
llvm-svn: 237099
In the lnt benchmark MultiSource/Benchmarks/MallocBench/gs/gs with
scalar and PHI modeling we detected the multidimensional accesses
with sizes variant in the SCoP. This will check the sizes for validity.
llvm-svn: 236395
This option is enabled since a long time and there does not seem to be a
situation in which we would not want to print alias scopes. Remove this option
to reduce the set of command-line option combinations that may expose bugs.
llvm-svn: 235861
I just learned that target triples prevent test cases to be run on other
architectures. Polly test cases are until now sufficiently target independent
to not require any target triples. Hence, we drop them.
llvm-svn: 235384
In Polly we used both the term 'scattering' and the term 'schedule' to describe
the execution order of a statement without actually distinguishing between them.
We now uniformly use the term 'schedule' for the execution order. This
corresponds to the terminology of isl.
History: CLooG introduced the term scattering as the generated code can be used
as a sequential execution order (schedule) or as a parallel dimension
enumerating different threads of execution (placement). In Polly and/or isl the
term placement was never used, but we uniformly refer to an execution order as a
schedule and only later introduce parallelism. When doing so we do not talk
about about specific placement dimensions.
llvm-svn: 235380
This will allow the ScopInfo to build the polyhedral representation for
non-affine regions that contain loops. Such loops are basically not visible
in the SCoP representation. Accesses that are variant in such loops are
therefor represented as non-affine accesses.
Differential Revision: http://reviews.llvm.org/D8153
llvm-svn: 234713
This will allow the ScopDetection to detect non-affine regions that
contain loops. All loops contained will be collected and are
accessible to later passes in order to adjust the access functions.
As the loops are non-affine and will not be part of the polyhedral
representation later, all accesses that are variant in these loops
have to be over approximated as non-affine accesses. They are
therefore handled the same way as other non-affine accesses.
Additionally, we do not count non-affine loops for the profitability
heuristic, thus a region with only a non-affine loop will only be
detected if the general detection of loop free regions is enabled.
Differential Revision: http://reviews.llvm.org/D8152
llvm-svn: 234711
This change ensures that we sign-extend integer types in case non-matching
operands are encountered when generating a multi-dimensional access offset.
This fixes http://llvm.org/PR23124
Reported-by: Jeremy Huddleston Sequoia <jeremyhu@apple.com>
llvm-svn: 234122
As soon as one operand of the product is invalid, the entire product is invalid.
This happens for example if one of the operands is not loop-invariant.
This fixes http://llvm.org/PR23125
Reported-by: Jeremy Huddleston Sequoia <jeremyhu@apple.com
llvm-svn: 234119
This allows us to delinerize code such as:
A[][n]
for (i
for (j
A[i][n-j-1] = ...
which would previously have been delinearize to an access A[i+1][-j-1].
To recover the correct access we apply the piecewise expression:
{ A[i][j] -> A[i-1][i+N]: i < 0; A[i][j] -> A[i][i]: i >= 0}
This approach generalizes to higher dimensions.
llvm-svn: 233566
This will strip the constant factor of a parameter befor we add it to
the SCoP. As a result the access functions are simplified, e.g., for
the attached test case.
llvm-svn: 233501
When creating parameters the SCEVexpander may introduce new induction variables,
that possibly create scalar dependences in the original scop, before we code
generate the scop. The resulting scalar dependences may then inhibit correct
code generation of the scop. To prevent this, we first version the code without
a run-time check and only then introduce new parameters and the run-time
condition. The if-condition that guards the original scop from being modified by
the SCEVexpander.
This change causes some test case changes as the run-time conditions are now
introduced in the split basic block rather than in the entry basic block.
This fixes http://llvm.org/PR22069
Test case reduced by: Karthik Senthil
llvm-svn: 233477
This options was earlier used for experiments with the vectorizer, but to my
knowledge is not really used anymore. If anybody needs this, we can always
reintroduce this feature.
llvm-svn: 232934
Replacing the old band_tree based code with code that is based on the new
schedule tree [1] interface makes applying complex schedule transformations a lot
more straightforward. We now do not need to reason about the meaning of flat
schedules, but can use a more straightforward tree structure. We do not yet
exploit this a lot in the current code, but hopefully we will be able to do so
soon.
This change also allows us to drop some code, as isl now provides some higher
level interfaces to apply loop transformations such as tiling.
This change causes some small test case changes as isl uses a slightly different
way to perform loop tiling, but no significant functional changes are intended.
[1] http://impact.gforge.inria.fr/impact2014/papers/impact2014-verdoolaege.pdf
llvm-svn: 232911
These test cases did not verify the CHECK lines at all. We add the FileCheck
and also fix some broken CHECK lines. Being here, we extend the checks to
cover the whole loop structure.
llvm-svn: 232710
The BB vectorizer is deprecated and there is no point in generating code for it
any more. This option was introduced when there was not yet any loop vectorizer
in sight. Now being matured, Polly should target the loop vectorizer.
llvm-svn: 232099
This test case was supposed to test the range analysis but it became just
another delinearization test case after enabling delinearization.
Suggested-by: Johannes Doerfert
llvm-svn: 231599
When code generating array index expressions the types of the different
components of the index expressions may not always match. We extend the type of
the index expression (if possible) and assert otherwise.
llvm-svn: 231592
We rename the Dependences pass to DependenceInfo as a first step to a
caching pass policy. The new DependenceInfo pass will later provide
"Dependences" for a SCoP.
To keep consistency the test folder is renamed too.
llvm-svn: 231308
If a scalar was defined and used only in a non-affine subregion we do
not need to model the accesses. However, if the scalar was defined
inside the region and escapes the region we have to model the access.
The same is true if the scalar was defined outside and used inside the
region.
llvm-svn: 230960
When we generate code for a whole region we have to respect dominance
and update it too.
The first is achieved with multiple "BBMap"s. Each copied block in the
region gets its own map. It is initialized only with values mapped in
the immediate dominator block, if this block is in the region and was
therefor already copied. This way no values defined in a block that
doesn't dominate the current one will be used.
To update dominance information we check if the immediate dominator of
the original block we want to copy is in the region. If so we set the
immediate dominator of the current block to the copy of the immediate
dominator of the original block.
llvm-svn: 230774
isl recently introduced a new interface to create run-time checks from
constraint sets. Use this interface to simplify our run-time check generation.
llvm-svn: 230640
This update contains:
- Fixes of minor issues detected by clang's scan_build
- More schedule tree infrastructure additions
This update slightly changes the output of our dependence analysis, but these
changes are purely syntactially.
llvm-svn: 230528
This is the code generation for region statements that are created
when non-affine control flow was present in the input. A new
generator, similar to the block or vector generator, for regions is
used to traverse and copy the region statement and to adjust the
control flow inside the new region in the end.
llvm-svn: 230340
This allows us to model non-affine regions in the SCoP representation.
SCoP statements can now describe either basic blocks or non-affine
regions. In the latter case all accesses in the region are accumulated
for the statement and write accesses, except in the entry, have to be
marked as may-write.
Differential Revision: http://reviews.llvm.org/D7846
llvm-svn: 230329
With this patch we allow the SCoP detection to detect regions as SCoPs
which have non-affine control flow inside. All non-affine regions are
tracked and later accessible to the ScopInfo.
As there is no real difference, non-affine branches as well as
floating point branches are covered (and both called non-affine
control flow). However, the detection is restricted to
overapproximate only loop free regions.
llvm-svn: 230325
Scops that only read seem generally uninteresting and scops that only write are
most likely initializations where there is also little to optimize. To not
waste compile time we bail early.
Differential Revision: http://reviews.llvm.org/D7735
llvm-svn: 229820
This commit imports the latest isl version into lib/External/isl. The changes
relavant for Polly are:
1) Schedule trees [1] have been introduced as a more structured way to
describe schedules. Polly does not yet use them, but we may switch to them
in the near future.
2) Another set of coalescing changes [2] simplifies some data dependences and
removes a couple of code generation artifacts.
We now understand that the following sets can be merged:
{ Stmt_S1[i0, i1] -> Stmt_S2[i0 + i1] :
i0 >= 0 and i1 <= 1023 - i0 and i1 >= 1
Stmt_S1[i0, 0] -> Stmt_S2[i0] : i0 <= 1023 and i0 >= 1}
into:
{ Stmt_S1[i0, i1] -> Stmt_S2[i0 + i1] : i1 <= 1023 - i0 and i1 >= 0 and
i1 >= 1 - i0 and i0 >= 0 }
Changes of this kind reduce unnecessary specialization during code
generation.
- for (int c3 = 0; c3 <= 1023; c3 += 1) {
- if (c3 % 2 == 0) {
- Stmt_for_body3(c1, c3);
- } else
- Stmt_for_body3(c1, c3);
- }
+ for (int c3 = 0; c3 <= 1023; c3 += 1)
+ Stmt_for_body3(c1, c3);
[1] http://impact.gforge.inria.fr/impact2014/papers/impact2014-verdoolaege.pdf
[2] http://impact.gforge.inria.fr/impact2015/papers/impact2015-verdoolaege.pdf
llvm-svn: 229423
This allows us to skip ast and code generation if we did not optimize
a SCoP and will not generate parallel or alias annotations. The
initial heuristic to exit is simple but allows improvements later on.
All failing test cases have been modified to disable early exit, thus
to keep their coverage.
Differential Revision: http://reviews.llvm.org/D7254
llvm-svn: 228851
These write are important as they will force the scheduling and code
generation of an otherwise trivial statement and also impose an order of
execution needed to guarantee the correct final value for a scalar in a loop.
Added test case modeled after ClamAV/clamscan.
llvm-svn: 228847
This allows us to model PHI nodes in the polyhedral description
without demoting them. The modeling however will result in the
same accesses as the demotion would have introduced.
Differential Revision: http://reviews.llvm.org/D7415
llvm-svn: 228433
The support is currently limited as we only allow them in the input but do
not emit them in the transformed SCoP due to the possible semantic changes.
Differential Revision: http://reviews.llvm.org/D5225
llvm-svn: 227054
lets 'ninja check-polly' pass for me with a lib64 build of LLVM.
I've not updated the standalone side as I don't use it and don't have an
easy way to test any changes I've made there. I mostly wanted to be able
to actually run Polly's tests when I update its use of LLVM's APIs
during my refactorings on the (very unlikely) off chance that I make
a change which compiles but does the wrong thing.
llvm-svn: 226420
This change ensures that the values that represent the array size of a
multi-dimensional access are correctly sign-extended when used to compute a
memory address used in the run-time alias check.
To make the test case more readable, we name the instructions that we generate.
llvm-svn: 225818
The max loop depth was incorrectly computed for scops that contain a
block from a loop but do not contain the entire loop. We need to
check that the full loop is contained in the region when computing
the max loop depth.
These scops occur when a region containing an inner loop is expanded
to include some blocks from the outer loop, but it cannot be fully
expanded to contain the outer loop because the region containing the
outer loop is invalid.
Differential Revision: http://reviews.llvm.org/D6913
llvm-svn: 225812
This support is still incomplete and consequently hidden behind a switch that
needs to be enabled. One problem is ATM that we incorrectly interpret very large
unsigned values as negative values even if used in an unsigned comparision.
llvm-svn: 225480
Schedule dimensions that have the same constant value accross all statements do
not carry any information, but due to the increased dimensionality of the
schedule cost compile time. To not pay this cost, we remove constant dimensions
if possible.
llvm-svn: 225067
Isl now specifically marks modulo operations that are compared against zero.
They can be implemented with the C/LLVM remainder operation.
We also update a couple of test cases where the output of isl has slightly
changed.
llvm-svn: 223607
This commit drops the Cloog support for Polly. The scripts and
documentation are changed to only use isl as prerequisity. In the code
all Cloog specific parts have been removed and all relevant tests have
been ported to the isl backend when it was created.
llvm-svn: 223141
SCEV based code generation has been the default for two weeks after having
been tested for a long time. We now drop the support the non-scev-based code
generation.
llvm-svn: 222978
In TempScopInfo::buildCondition we extract the conditions to guard the
BB *in addition of* loop bounds. This means we should only consider the
conditions in the paths (in CFG) that do not contain cycles (loops).
At the same time, we set the invert flag if the FalseBB of the current
branch dominates our target BB to indicate that we reach the target BB
with an inverted condition from the current branch.
In this case, the path from the FalseBB contains a cycle if the FalseBB
is the target of a backedge. The conditions implied by such a path should
not be consider. We can identify such a case by checking if the TrueBB
also dominates our target BB, which means we can also reach our target
BB from the TrueBB, without going through the backedge.
llvm-svn: 222907
In case a GEP instruction references into a fixed size array e.g., an access
A[i][j] into an array A[100x100], LLVM-IR does not guarantee that the subscripts
always compute values that are within array bounds. We now derive the set of
parameter values for which all accesses are within bounds and add the assumption
that the scop is only every executed with this set of parameter values.
Example:
void foo(float A[][20], long n, long m {
for (long i = 0; i < n; i++)
for (long j = 0; j < m; j++)
A[i][j] = ...
This loop yields out-of-bound accesses if m is at least 20 and at the same time
at least one iteration of the outer loop is executed. Hence, we assume:
n <= 0 or m <= 20.
Doing so simplifies the dependence analysis problem, allows us to perform
more optimizations and generate better code.
TODO: The location where the GEP instruction is executed is not necessarily the
location where the memory is actually accessed. As a result scanning for GEP[s]
is imprecise. Even though this is not a correctness problem, this imprecision
may result in missed optimizations or non-optimal run-time checks.
In polybench where this mismatch between parametric loop bounds and fixed size
arrays is common, we see with this patch significant reductions in compile time
(up to 50%) and execution time (up to 70%). We see two significant compile time
regressions (fdtd-2d, jacobi-2d-imper), and one execution time regression
(trmm). Both regressions arise due to additional optimizations that have been
enabled by this patch. They can be addressed in subsequent commits.
http://reviews.llvm.org/D6369
llvm-svn: 222754
This patch includes tests where we actually need to adjust the CHECK lines
for SCEV based code generation. Besides these adjustments we add explicit
calls to -polly-codegen-scev=[true|false] and make sure we test both cases.
llvm-svn: 222112
This prevents SCEVs to reference values not valid any more and as a consequence
solves a bug where such values reintroduced during ast generation caused the
independent blocks pass to fail validation.
http://llvm.org/PR21204
llvm-svn: 222103
The isl based backend has been tested since a long time and with the recently
commited OpenMP support the last missing piece of functionality was ported from
the CLooG backend.
The isl based backend gives us interesting new functionality:
- Run-time alias checks (enabled by default)
Optimize scops that contain possibly aliasing pointers. This feature has
largely increased the number of loop nests we consider for optimization.
Thanks Johannes!
- Delinearization (not yet enabled by default)
Model accesses to multi-dimensional arrays precisely. This will allow us to
understand kernels with multi-dimensional VLAs written in Julia, boost::ublas,
coremark or C99.
Thanks Sebastian!
- Generation of higher quality code
Sven and me spent a long time to optimize the quality of the generated code. A
major focus were expressions as they result from modulos/divisions or
piecewise affine expressions (a ? b : c).
- Full/Partial tile separation, polyhedral unrolling
The isl code generation provides functionality to generate specialized code
for core and cleanup loops and to specialize code using polyhedral context
information while unrolling statements.
(not yet exploited in Polly)
- Modifieable access functions
We can now use standard isl functionality to remap memory accesses to new
data locations. A standard use case is the use of shared memory, where
accesses to a larger region in global memory need to be mapped to a smaller
shared memory region using a modulo mapping.
(not yet exploited in Polly)
The cloog based code generation is still available for comparision, but is
scheduled for removal.
llvm-svn: 222101
Tobias Grosser