Commit Graph

433 Commits

Author SHA1 Message Date
Philip Pfaffe 85cc5687df [IslAst] Untangle IslAst lit-testcases from specifics of the legacy-PM
Summary:
This consists instances of two changes:

- Accept any order of checks for a specific loop form, that appear in different order in the new vs legacy-PM.
- Remove checks for specific regions.

Reviewers: grosser

Reviewed By: grosser

Subscribers: pollydev, llvm-commits

Tags: #polly

Differential Revision: https://reviews.llvm.org/D35837

llvm-svn: 308976
2017-07-25 15:07:42 +00:00
Tobias Grosser 1eeedf4829 [IslNodeBuilder] Relax complexity check in invariant loads and run it early
When performing invariant load hoisting we check that invariant load expressions
are not too complex. Up to this commit, we performed this check by counting the
sum of dimensions in the access range as a very simple heuristic. This heuristic
is a little too conservative, as it prevents hoisting for any scops with a
very large number of parameters. Hence, we update the heuristic to only count
existentially quantified dimensions and set dimensions. We expect this to still
detect the problematic expressions in h264 because of which this check was
originally introduced.

For some unknown reason, this complexity check was originally committed in
IslNodeBuilder. It really belongs in ScopInfo, as there is no point in
optimizing a program which we could have known earlier cannot be code generated.
The benefit of running the check early is that we can avoid to even hoist checks
that are expensive to code generate as invariant loads. This can be seen in
the changed tests, where we now indeed detect the scop, but just not invariant
load hoist the complicated access.

We also improve the formatting of the code, document it, and use isl++ to
simplify expressions.

llvm-svn: 308659
2017-07-20 19:55:19 +00:00
Tobias Grosser 4556c9b8fe [ScopInfo] Simplify new access functions under domain context
Summary:
We do not keep domain constraints on access functions when building the
scop. Hence, for consistency reasons, it makes also sense to not include
them when storing a new access function. This change results in simpler
access functions that make output easier to read.

This patch also helps to make DeLICMed memory accesses to be understood by
our matrix multiplication pattern matching pass. Further changes to the
matrix multiplication pattern matching are needed for this to work, so the
corresponding test case will be added in a future commit.

Reviewers: Meinersbur, bollu, gareevroman, efriedma, huihuiz, sebpop, simbuerg

Subscribers: pollydev, llvm-commits

Tags: #polly

Differential Revision: https://reviews.llvm.org/D35237

llvm-svn: 308215
2017-07-17 20:47:10 +00:00
Tobias Grosser a3aa423fc3 [ScopDetection] If a loop is not part of a scop, none of it backedges can be
This patch makes sure that in case a loop is not fully contained within a region
that later forms a SCoP, none of the loop backedges are allowed to be part of
the region. We currently do not support the situation where only some of a loops
backedges are part of a scop. Today, this can break both scop modeling and code
generation. One such breaking test case is for example
test/ScopDetectionDiagnostics/loop_partially_in_scop-2.ll, where we totally
forgot to code generate some of the backedges. Fortunately, it is commonly not
necessary to support these partial loops, it is way more common that either
no backedge is included in a region or all loop backedge are included.

This fixes a recent miscompile in
MultiSource/Benchmarks/MiBench/consumer-typeset which was exposed after
r306477.

llvm-svn: 308113
2017-07-15 22:42:17 +00:00
Siddharth Bhat a1b2086a33 [Invariant Loads] Do not consider invariant loads to have dependences.
We need to relax constraints on invariant loads so that they do not
create fake RAW dependences. So, we do not consider invariant loads as
scalar dependences in a region.

During these changes, it turned out that we do not consider `llvm::Value`
replacements correctly within `PPCGCodeGeneration` and `ISLNodeBuilder`.
The replacements dictated by `ValueMap` were not being followed in all
places. This was fixed in this commit. There is no clean way to decouple
this change because this bug only seems to arise when the relaxed
version of invariant load hoisting was enabled.

Differential Revision: https://reviews.llvm.org/D35120

llvm-svn: 307907
2017-07-13 12:18:56 +00:00
Tobias Grosser e40c0fe3f8 [tests] Set -polly-import-jscop-dir=%S always
This simplifies the test cases.

llvm-svn: 307645
2017-07-11 10:39:01 +00:00
Tobias Grosser 153a508349 [IslAst] Print memory accesses in AST dump
When providing the option "-polly-ast-print-accesses" Polly also prints the
memory accesses that are generated:

    #pragma known-parallel
    for (int c0 = 0; c0 <= 1023; c0 += 4)
      #pragma simd
      for (int c1 = c0; c1 <= c0 + 3; c1 += 1)
        Stmt_for_body(
          /* read  */ &MemRef_B[0]
          /* write */  MemRef_A[c1]
        );

This makes writing and debugging memory layout transformations easier.

Based on a patch contributed by Thomas Lang (ETH Zurich)

llvm-svn: 307579
2017-07-10 20:13:06 +00:00
Michael Kruse b738ffa845 Heap allocation for new arrays.
This patch aims to implement the option of allocating new arrays created
by polly on heap instead of stack. To enable this option, a key named
'allocation' must be written in the imported json file with the value
'heap'.

We need such a feature because in a next iteration, we will implement a
mechanism of maximal static expansion which will need a way to allocate
arrays on heap. Indeed, the expansion is very costly in terms of memory
and doing the allocation on stack is not worth considering.

The malloc and the free are added respectively at polly.start and
polly.exiting such that there is no use-after-free (for instance in case
of Scop in a loop) and such that all memory cells allocated with a
malloc are free'd when we don't need them anymore.

We also add :

- In the class ScopArrayInfo, we add a boolean as member called IsOnHeap
  which represents the fact that the array in allocated on heap or not.
- A new branch in the method allocateNewArrays in the ISLNodeBuilder for
  the case of heap allocation. allocateNewArrays now takes a BBPair
  containing polly.start and polly.exiting. allocateNewArrays takes this
  two blocks and add the malloc and free calls respectively to
  polly.start and polly.exiting.
- As IntPtrTy for the malloc call, we use the DataLayout one.

To do that, we have modified :

- createScopArrayInfo and getOrCreateScopArrayInfo such that it returns
  a non-const SAI, in order to be able to call setIsOnHeap in the
  JSONImporter.
- executeScopConditionnaly such that it return both start block and end
  block of the scop, because we need this two blocs to be able to add
  the malloc and the free calls at the right position.

Differential Revision: https://reviews.llvm.org/D33688

llvm-svn: 306540
2017-06-28 13:02:43 +00:00
Michael Kruse 214deb7960 [CodeGen] Emit aliasing metadata for new arrays.
Ensure that all array base pointers are assigned before generating
aliasing metadata by allocating new arrays beforehand.

Before this patch, getBasePtr() returned nullptr for new arrays because
the arrays were created at a later point. Nullptr did not match to any
array after the created array base pointers have been assigned and when
the loads/stores are generated.

llvm-svn: 305675
2017-06-19 10:19:29 +00:00
Tobias Grosser deefbced96 [Polly] [BlockGen] Support partial writes in regions
Summary:
The RegionGenerator traditionally kept a BlockMap that mapped from original
basic blocks to newly generated basic blocks. With the introduction of partial
writes such a 1:1 mapping is not possible any more, as a single basic block
can be code generated into multiple basic blocks. Hence, depending on the use
case we need to either use the first basic block or the last basic block.

This is intended to address the last four cases of incorrect code generation
in our AOSP buildbot and hopefully should turn it green.

Reviewers: Meinersbur, bollu, gareevroman, efriedma, huihuiz, sebpop, simbuerg

Reviewed By: Meinersbur

Subscribers: pollydev, llvm-commits

Tags: #polly

Differential Revision: https://reviews.llvm.org/D33767

llvm-svn: 304808
2017-06-06 17:17:30 +00:00
Tobias Grosser 22be8a18f3 Add test coverage for regions with non-affine loops
This adds test coverage for regions with non-affine loops, which we
unfortunately missed when committing this features years ago. We will add
more test coverage over time.

llvm-svn: 304672
2017-06-03 23:39:02 +00:00
Siddharth Bhat 726c28f8c4 [CodeGen] Track trip counts per-scop for performance measurement.
- Add a counter that is incremented once on exit from a scop.

- Test cases got split into two: one to test the cycles, and another one
to test trip counts.

- Sample output:
```name=sample-output.txt
scop function, entry block name, exit block name, total time, trip count
warmup, %entry.split, %polly.merge_new_and_old, 5180, 1
f, %entry.split, %polly.merge_new_and_old, 409944, 500
g, %entry.split, %polly.merge_new_and_old, 1226, 1
```

Differential Revision: https://reviews.llvm.org/D33822

llvm-svn: 304543
2017-06-02 11:36:52 +00:00
Siddharth Bhat a4dea6bb05 [CodeGen] Print performance counter information in CSV.
This ensures that tools can parse performance information which Polly
generates easily.

- Sample output:
```name=out.csv
scop function, entry block name, exit block name, total time
warmup, %entry.split, %polly.merge_new_and_old, 1960
f, %entry.split, %polly.merge_new_and_old, 1238
g, %entry.split, %polly.merge_new_and_old, 1218
```

- Example code to parse output:
```lang=python, name=example-parse.py
import asciitable
import sys

table = asciitable.read('out.csv', delimiter=',')
asciitable.write(table, sys.stdout, delimiter=',')
```

llvm-svn: 304533
2017-06-02 09:20:02 +00:00
Siddharth Bhat 07bee290de [CodeGen] Extend Performance Counter to track per-scop information.
Previously, we would generate one performance counter for all scops.
Now, we generate both the old information, as well as a per-scop
performance counter to generate finer grained information.

This patch needed a way to generate a unique name for a `Scop`.
The start region, end region, and function name combined provides a
unique `Scop` name. So, `Scop` has a new public API to provide its start
and end region names.

Differential Revision: https://reviews.llvm.org/D33723

llvm-svn: 304528
2017-06-02 08:01:22 +00:00
Tobias Grosser f51decb5fe [BlockGenerator] Take context into account when identifying partial writes
A partial write is a write where the domain of the values written is a subset of
the execution domain of the parent statement containing the write. Originally,
we directly checked this subset relation whereas it is indeed only important
that the subset relation holds for the parameter values that are known to be
valid in the execution context of the scop. We update our check to avoid the
unnecessary introduction of partial writes in situations where the write appears
to be partial without context information, but where context information allows
us to understand that a full write can be generated.

This change fixes (hides) a recent regression introduced in r303517, which broke
our AOSP builds. The part that is correctly fixed in this change is that we do
not any more unnecessarily generate a partial write. This is good performance
wise and, as we currently do not yet explicitly introduce partial writes in the
default configuration, this also hides possible bugs in the partial writes
implementation. The crashes that we have originally seen were caused by such
a bug, where partial writes were incorrectly generated in region statements. An
additional patch in a subsequent commit is needed to address this problem.

Reported-by: Reported-by: Eli Friedman <efriedma@codeaurora.org>

Differential Revision: https://reviews.llvm.org/D33759

llvm-svn: 304398
2017-06-01 09:34:20 +00:00
Michael Kruse 1aad76c18f [CodeGen] Add invalidation of the loop SCEVs after merge block generation.
The SCEVs of loops surrounding the escape users of a merge blocks are
forgotten, so that loop trip counts based on old values can be revoked.

This fixes llvm.org//PR32536

Contributed-by: Baranidharan Mohan <mbdharan@gmail.com>

Differential Revision: https://reviews.llvm.org/D33195

llvm-svn: 303561
2017-05-22 15:36:53 +00:00
Michael Kruse 706f79ab14 [CodeGen] Support partial write accesses.
Allow the BlockGenerator to generate memory writes that are not defined
over the complete statement domain, but only over a subset of it. It
generates a condition that evaluates to 1 if executing the subdomain,
and only then execute the access.

Only write accesses are supported. Read accesses would require a PHINode
which has a value if the access is not executed.

Partial write makes DeLICM able to apply mappings that are not defined
over the entire domain (for instance, a branch that leaves a loop with
a PHINode in its header; a MemoryKind::PHI write when leaving is never
read by its PHI read).

Differential Revision: https://reviews.llvm.org/D33255

llvm-svn: 303517
2017-05-21 22:46:57 +00:00
Tobias Grosser ee61ebb134 Fix buildbots after r303429
A test case with a GPU runline was added without setting 'REQUIRES=pollyacc'. We
drop the GPU run line, as the basic functionality can already be tested with
the normal code generation.

llvm-svn: 303485
2017-05-20 04:22:26 +00:00
Siddharth Bhat b7f68b8c9e [Fortran Support] Materialize outermost dimension for Fortran array.
- We use the outermost dimension of arrays since we need this
information to generate GPU transfers.

- In general, if we do not know the outermost dimension of the array
(because the indexing expression is non-affine, for example) then we
simply cannot generate transfer code.

- However, for Fortran arrays, we can use the Fortran array
representation which stores the dimensions of all arrays.

- This patch uses the Fortran array representation to generate code that
computes the outermost dimension size.

Differential Revision: https://reviews.llvm.org/D32967

llvm-svn: 303429
2017-05-19 15:07:45 +00:00
Hongbin Zheng 4fe342cb75 [Polly] Generate more 'canonical' induction variable
Today Polly generates induction variable in this way:

polly.indvar = phi 0, polly.indvar.next
...
polly.indvar.next = polly.indvar + stide
polly.loop_cond = predicate polly.indvar, (UB - stride)

Instead of:

polly.indvar = phi 0, polly.indvar.next
...
polly.indvar.next = polly.indvar + stide
polly.loop_cond = predicate polly.indvar.next, UB

The way Polly generate induction variable cause some problem in the indvar simplify pass.
This patch make polly generate the later form, by assuming the induction variable never overflow

Differential Revision: https://reviews.llvm.org/D33089

llvm-svn: 302866
2017-05-12 02:17:15 +00:00
Tobias Grosser f3adab4c20 [Polly] Canonicalize arrays according to base-ptr equivalence class
Summary:
    In case two arrays share base pointers in the same invariant load equivalence
    class, we canonicalize all memory accesses to the first of these arrays
    (according to their order in the equivalence class).

    This enables us to optimize kernels such as boost::ublas by ensuring that
    different references to the C array are interpreted as accesses to the same
    array. Before this change the runtime alias check for ublas would fail, as it
    would assume models of the C array with differing (but identically valued) base
    pointers would reference distinct regions of memory whereas the referenced
    memory regions were indeed identical.

    As part of this change we remove most of the MemoryAccess::get*BaseAddr
    interface. We removed already all references to get*BaseAddr in previous
    commits to ensure that no code relies on matching base pointers between
    memory accesses and scop arrays -- except for three remaining uses where we
    need the original base pointer. We document for these situations that
    MemoryAccess::getOriginalBaseAddr may return a base pointer that is distinct
    to the base pointer of the scop array referenced by this memory access.

Reviewers: sebpop, Meinersbur, zinob, gareevroman, pollydev, huihuiz, efriedma, jdoerfert

Reviewed By: Meinersbur

Subscribers: etherzhhb

Tags: #polly

Differential Revision: https://reviews.llvm.org/D28518

llvm-svn: 302636
2017-05-10 10:59:58 +00:00
Tobias Grosser 1859463876 Adjust test case to not trigger the SCEV optimization committed in r302096
This makes sure we still test the case that a PHI-NODE cannot be analyzed by
scalar evolution and consequently must be code generated explicitly.  As
Michael's optimization triggers only on a very specific "add %iv, %step"
pattern, just changing 'add' to 'mul' adds back test coverage.

llvm-svn: 302132
2017-05-04 08:56:54 +00:00
Tobias Grosser 3d76f2ccd3 [tests] Ensure all test cases use named variables
This makes it easier to read and possibly even modify the test cases, as there
is no need to keep the variable increment in steps of one. More importantly, by
using explicit variable names we do not need to rely on the implicit numbering
of statements when dumping the scop information.

This makes it easier to read and possibly even modify the test cases.
Furthermore, by using explicit variables we do not need to rely on the implicit
numbering of statements when dumping the scop information. In a future commit,
this implicit numbering will likely not be used any more to refer to LLVM-IR
values as it is very expensive to construct.

llvm-svn: 301689
2017-04-28 21:16:29 +00:00
Tobias Grosser c96c1d8c87 [ScopInfo] Consider only write-free dereferencable loads as invariant
When we introduced in r297375 support for hoisting loads that are known
to be dereferencable without any conditional guard, we forgot to keep the check
to verify that no other write into the very same location exists. This
change ensures now that dereferencable loads are allowed to access everything,
but can only be hoisted in case no conflicting write exists.

This resolves llvm.org/PR32778

Reported-by: Huihui Zhang <huihuiz@codeaurora.org>
llvm-svn: 301582
2017-04-27 20:08:16 +00:00
Hongbin Zheng 0f8f177682 [Polly] Do not introduce address space cast
Do not introduce address space cast in IslNodeBuilder::preloadUnconditionally.

Differential Revision: https://reviews.llvm.org/D32581

llvm-svn: 301519
2017-04-27 06:42:14 +00:00
Michael Kruse 895f5d8080 Remove llvm.lifetime.start/end in original region.
The current StackColoring algorithm does not correctly handle the
situation when some, but not all paths from a BB to the entry node
cross a llvm.lifetime.start. According to an interpretation of the
language reference at
http://llvm.org/docs/LangRef.html#llvm-lifetime-start-intrinsic
this might be correct, but it would cost too much effort to handle
in StackColoring.

To be on the safe side, remove all lifetime markers even in the original
code version (they have never been copied to the optimized version)
to ensure that no path to the entry block will cross a
llvm.lifetime.start.

The same principle applies to paths the a function return and the
llvm.lifetime.end marker, so we remove them as well.

This fixes llvm.org/PR32251.

Also see the discussion at
http://lists.llvm.org/pipermail/llvm-dev/2017-March/111551.html

llvm-svn: 299585
2017-04-05 20:09:59 +00:00
Tobias Grosser 65371af2e1 [CodeGen] Add Performance Monitor
Add support for -polly-codegen-perf-monitoring. When performance monitoring
is enabled, we emit performance monitoring code during code generation that
prints after program exit statistics about the total number of cycles executed
as well as the number of cycles spent in scops. This gives an estimate on how
useful polyhedral optimizations might be for a given program.

Example output:

  Polly runtime information
  -------------------------
  Total: 783110081637
  Scops: 663718949365

In the future, we might also add functionality to measure how much time is spent
in optimized scops and how many cycles are spent in the fallback code.

Reviewers: bollu,sebpop

Tags: #polly

Differential Revision: https://reviews.llvm.org/D31599

llvm-svn: 299359
2017-04-03 14:55:37 +00:00
Michael Kruse 0b8949e6ed [test] Fix two testcases. NFC.
Trivial fix for two testcases. When Polly isn't linked into opt,
independent of whether it's built in-tree or not, these testcases forget
to load the appropriate library.

Contributed-by: Philip Pfaffe <philip.pfaffe@gmail.com>

Differential Revision: https://reviews.llvm.org/D31596

llvm-svn: 299357
2017-04-03 12:37:10 +00:00
Tobias Grosser bd96c73a1a Add test case for r299352.
llvm-svn: 299353
2017-04-03 07:44:23 +00:00
Roman Gareev 23df27682a Map the new load to the base pointer of the invariant load hoisted load
Map the new load to the base pointer of the invariant load hoisted load
to be able to find the alias information for it.

Reviewed-by: Tobias Grosser <tobias@grosser.es>

Differential Revision: https://reviews.llvm.org/D30605

llvm-svn: 298507
2017-03-22 13:57:53 +00:00
Tobias Grosser b28f86e9e6 [CodeGen] Remove need for all parameters to be in scop context for load hoisting.
When not adding constraints on parameters using -polly-ignore-parameter-bounds,
the context may not necessarily list all parameter dimensions. To support code
generation in this situation, we now always iterate over the actual parameter
list, rather than relying on the context to list all parameter dimensions.

llvm-svn: 298197
2017-03-18 23:12:49 +00:00
Tobias Grosser 7693b116a1 [OpenMP] Do not emit lifetime markers for context
In commit r219005 lifetime markers have been introduced to mark the lifetime of
the OpenMP context data structure. However, their use seems incorrect and
recently caused a miscompile in ASC_Sequoia/CrystalMk after r298053 which was
not at all related to r298053. r298053 only caused a change in the loop order,
as this change resulted in a different isl internal representation which caused
the scheduler to derive a different schedule. This change then caused the IR to
change, which apparently created a pattern in which LLVM exploites the lifetime
markers. It seems we are using the OpenMP context outside of the lifetime
markers. Even though CrystalMk could probably be fixed by expanding the scope of
the lifetime markers, it is not clear what happens in case the OpenMP function
call is in a loop which will cause a sequence of starting and ending lifetimes.
As it is unlikely that the lifetime markers give any performance benefit, we
just drop them to remove complexity.

llvm-svn: 298192
2017-03-18 20:10:07 +00:00
Tobias Grosser 8bd7f3c0a5 [ScopDetect/Info] Allow unconditional hoisting of loads from dereferenceable ptrs
In case LLVM pointers are annotated with !dereferencable attributes/metadata
or LLVM can look at the allocation from which a pointer is derived, we can know
that dereferencing pointers is safe and can be done unconditionally. We use this
information to proof certain pointers as save to hoist and then hoist them
unconditionally.

llvm-svn: 297375
2017-03-09 11:36:00 +00:00
Michael Kruse 6744efa8d8 [ScopDetection] Only allow SCoP-wide available base pointers.
Simplify ScopDetection::isInvariant(). Essentially deny everything that
is defined within the SCoP and is not load-hoisted.

The previous understanding of "invariant" has a few holes:

- Expressions without side-effects with only invariant arguments, but
  are defined withing the SCoP's region with the exception of selects
  and PHIs. These should be part of the index expression derived by
  ScalarEvolution and not of the base pointer.

- Function calls with that are !mayHaveSideEffects() (typically
  functions with "readnone nounwind" attributes). An example is given
  below.

      @C = external global i32
      declare float* @getNextBasePtr(float*) readnone nounwind
      ...
      %ptr = call float* @getNextBasePtr(float* %A, float %B)

  The call might return:

  * %A, so %ptr aliases with it in the SCoP
  * %B, so %ptr aliases with it in the SCoP
  * @C, so %ptr aliases with it in the SCoP
  * a new pointer everytime it is called, such as malloc()
  * a pointer into the allocated block of one of the aforementioned
  * any of the above, at random at each call

  Hence and contrast to a comment in the base_pointer.ll regression
  test, %ptr is not necessarily the same all the time. It might also
  alias with anything and no AliasAnalysis can tell otherwise if the
  definition is external. It is hence not suitable in the role of a
  base pointer.

The practical problem with base pointers defined in SCoP statements is
that it is not available globally in the SCoP. The statement instance
must be executed first before the base pointer can be used. This is no
problem if the base pointer is transferred as a scalar value between
statements. Uses of MemoryAccess::setNewAccessRelation may add a use of
the base pointer anywhere in the array. setNewAccessRelation is used by
JSONImporter, DeLICM and D28518. Indeed, BlockGenerator currently
assumes that base pointers are available globally and generates invalid
code for new access relation (referring to the base pointer of the
original code) if not, even if the base pointer would be available in
the statement.

This could be fixed with some added complexity and restrictions. The
ExprBuilder must lookup the local BBMap and code that call
setNewAccessRelation must check whether the base pointer is available
first.

The code would still be incorrect in the presence of aliasing. There
is the switch -polly-ignore-aliasing to explicitly allow this, but
it is hardly a justification for the additional complexity. It would
still be mostly useless because in most cases either getNextBasePtr()
has external linkage in which case the readnone nounwind attributes
cannot be derived in the translation unit itself, or is defined in the
same translation unit and gets inlined.

Reviewed By: grosser

Differential Revision: https://reviews.llvm.org/D30695

llvm-svn: 297281
2017-03-08 15:14:46 +00:00
Michael Kruse 5a4ec5c42b [ScopDetection] Require LoadInst base pointers to be hoisted.
Only when load-hoisted we can be sure the base pointer is invariant
during the SCoP's execution. Most of the time it would be added to
the required hoists for the alias checks anyway, except with
-polly-ignore-aliasing, -polly-use-runtime-alias-checks=0 or if
AliasAnalysis is already sure it doesn't alias with anything
(for instance if there is no other pointer to alias with).

Two more parts in Polly assume that this load-hoisting took place:
- setNewAccessRelation() which contains an assert which tests this.
- BlockGenerator which would use to the base ptr from the original
  code if not load-hoisted (if the access expression is regenerated)

Differential Revision: https://reviews.llvm.org/D30694

llvm-svn: 297195
2017-03-07 20:28:43 +00:00
Tobias Grosser 6c9958e0b3 [tests] Make sure tests do not end in 'unreachable' - Part III
There is no point in optimizing unreachable code, hence our test cases should
always return.

This commit is part of a series that makes Polly more robust on the presence of
unreachables.

llvm-svn: 297158
2017-03-07 16:28:53 +00:00
Tobias Grosser 87dcd46aa7 [tests] Make sure tests do not end in 'unreachable' - Part II
There is no point in optimizing unreachable code, hence our test cases should
always return.

This commit is part of a series that makes Polly more robust on the presence of
unreachables.

llvm-svn: 297150
2017-03-07 15:23:30 +00:00
Tobias Grosser 2dc1f547ae [tests] Make sure tests do not end in 'unreachable'
There is no point in optimizing unreachable code, hence our test cases should
always return.

This commit is part of a series that makes Polly more robust on the presence of
unreachables.

llvm-svn: 297147
2017-03-07 15:17:23 +00:00
Tobias Grosser c2f151084d [ScopInfo] Disable memory folding in case it results in multi-disjunct relations
Multi-disjunct access maps can easily result in inbound assumptions which
explode in case of many memory accesses and many parameters. This change reduces
compilation time of some larger kernel from over 15 minutes to less than 16
seconds.

Interesting is the test case test/ScopInfo/multidim_param_in_subscript.ll
which has a memory access

  [n] -> { Stmt_for_body3[i0, i1] -> MemRef_A[i0, -1 + n - i1] }

which requires folding, but where only a single disjunct remains. We can still
model this test case even when only using limited memory folding.

For people only reading commit messages, here the comment that explains what
memory folding is:

To recover memory accesses with array size parameters in the subscript
expression we post-process the delinearization results.

We would normally recover from an access A[exp0(i) * N + exp1(i)] into an
array A[][N] the 2D access A[exp0(i)][exp1(i)]. However, another valid
delinearization is A[exp0(i) - 1][exp1(i) + N] which - depending on the
range of exp1(i) - may be preferrable. Specifically, for cases where we
know exp1(i) is negative, we want to choose the latter expression.

As we commonly do not have any information about the range of exp1(i),
we do not choose one of the two options, but instead create a piecewise
access function that adds the (-1, N) offsets as soon as exp1(i) becomes
negative. For a 2D array such an access function is created by applying
the piecewise map:

[i,j] -> [i, j] :      j >= 0
[i,j] -> [i-1, j+N] :  j <  0

After this patch we generate only the first case, except for situations where
we can proove the first case to be invalid and can consequently select the
second without introducing disjuncts.

llvm-svn: 296679
2017-03-01 21:11:27 +00:00
Tobias Grosser d7c4975349 [ScopInfo] Simplify inbounds assumptions under domain constraints
Without this simplification for a loop nest:

  void foo(long n1_a, long n1_b, long n1_c, long n1_d,
           long p1_b, long p1_c, long p1_d,
           float A_1[][p1_b][p1_c][p1_d]) {
    for (long i = 0; i < n1_a; i++)
      for (long j = 0; j < n1_b; j++)
        for (long k = 0; k < n1_c; k++)
          for (long l = 0; l < n1_d; l++)
            A_1[i][j][k][l] += i + j + k + l;
 }

the assumption:

  n1_a <= 0 or (n1_a > 0 and n1_b <= 0) or
  (n1_a > 0 and n1_b > 0 and n1_c <= 0) or
  (n1_a > 0 and n1_b > 0 and n1_c > 0 and n1_d <= 0) or
  (n1_a > 0 and n1_b > 0 and n1_c > 0 and n1_d > 0 and
   p1_b >= n1_b and p1_c >= n1_c and p1_d >= n1_d)

is taken rather than the simpler assumption:

  p9_b >= n9_b and p9_c >= n9_c and p9_d >= n9_d.

The former is less strict, as it allows arbitrary values of p1_* in case, the
loop is not executed at all. However, in practice these precise constraints
explode when combined across different accesses and loops. For now it seems
to make more sense to take less precise, but more scalable constraints by
default. In case we find a practical example where more precise constraints
are needed, we can think about allowing such precise constraints in specific
situations where they help.

This change speeds up the new test case from taking very long (waited at least
a minute, but it probably takes a lot more) to below a second.

llvm-svn: 296456
2017-02-28 09:45:54 +00:00
Tobias Grosser 72745c2ef5 Updated isl to isl-0.18-254-g6bc184d
This update includes a couple more coalescing changes as well as a large
number of isl-internal code cleanups (dead assigments, ...).

llvm-svn: 295419
2017-02-17 05:11:16 +00:00
Tobias Grosser 4553463be4 [IRBuilder] Extract base pointers directly from ScopArray
Instead of iterating over statements and their memory accesses to extract the
set of available base pointers, just directly iterate over all ScopArray
objects. This reflects more the actual intend of the code: collect all arrays
(and their base pointers) to emit alias information that specifies that accesses
to different arrays cannot alias.

This change removes unnecessary uses of MemoryAddress::getBaseAddr() in
preparation for https://reviews.llvm.org/D28518.

llvm-svn: 294574
2017-02-09 09:34:42 +00:00
Tobias Grosser 26fb7d7517 [IslAst] Print the ScopArray name to mark reductions
Before this change we used the name of the base pointer to mark reductions. This
is imprecise as the canonical reference is the ScopArray itself and not the
basepointer of a reduction. Using the base pointer of reductions is problematic
in cases where a single ScopArray is referenced through two different base
pointers.

This change removes unnecessary uses of MemoryAddress::getBaseAddr() in
preparation for https://reviews.llvm.org/D28518.

llvm-svn: 294568
2017-02-09 08:06:15 +00:00
Tobias Grosser 75dfaa1dbe BlockGenerator: Do not redundantly reload from PHI-allocas in non-affine stmts
Before this change we created an additional reload in the copy of the incoming
block of a PHI node to reload the incoming value, even though the necessary
value has already been made available by the normally generated scalar loads.
In this change, we drop the code that generates this redundant reload and
instead just reuse the scalar value already available.

Besides making the generated code slightly cleaner, this change also makes sure
that scalar loads go through the normal logic, which means they can be remapped
(e.g. to array slots) and corresponding code is generated to load from the
remapped location. Without this change, the original scalar load at the
beginning of the non-affine region would have been remapped, but the redundant
scalar load would continue to load from the old PHI slot location.

It might be possible to further simplify the code in addOperandToPHI,
but this would not only mean to pull out getNewValue, but to also change the
insertion point update logic. As this did not work when trying it the first
time, this change is likely not trivial. To not introduce bugs last minute, we
postpone further simplications to a subsequent commit.

We also document the current behavior a little bit better.

Reviewed By: Meinersbur

Differential Revision: https://reviews.llvm.org/D28892

llvm-svn: 292486
2017-01-19 14:12:45 +00:00
Tobias Grosser a989a8b84c Improve test coverage in test/Isl/CodeGen/loop_partially_in_scop.ll [NFC]
We rename the test case with -metarenamer to make the variable names easier to
read and add additional check lines that verify the code we currently generate
for PHI nodes. This code is interesting as it contains a PHI node in a
non-affine sub-region, where some incoming blocks are within the non-affine
sub-region and others are outside of the non-affine subregion.

As can be seen in the check lines we currently load the PHI-node value twice.
This commit documents this behavior. In a subsequent patch we will try to
improve this.

llvm-svn: 292470
2017-01-19 04:54:45 +00:00
Tobias Grosser e1ff0cf2eb Relax assert when setting access functions with invariant base pointers
Summary:
Instead of forbidding such access functions completely, we verify that their
base pointer has been hoisted and only assert in case the base pointer was
not hoisted.

I was trying for a little while to get a test case that ensures the assert is
correctly fired in case of invariant load hoisting being disabled, but I could
not find a good way to do so, as llvm-lit immediately aborts if a command
yields a non-zero return value. As we do not generally test our asserts,
not having a test case here seems OK.

This resolves http://llvm.org/PR31494

Suggested-by: Michael Kruse <llvm@meinersbur.de>

Reviewers: efriedma, jdoerfert, Meinersbur, gareevroman, sebpop, zinob, huihuiz, pollydev

Reviewed By: Meinersbur

Differential Revision: https://reviews.llvm.org/D28798

llvm-svn: 292213
2017-01-17 12:00:42 +00:00
Tobias Grosser 7fcb689ea8 test: harden test case to fail even in non-asserts build
The original test case was added in r292147.

Suggested-by: Michael Kruse <llvm@meinersbur.de>
llvm-svn: 292202
2017-01-17 07:03:25 +00:00
Tobias Grosser eec7f6daa1 Add test showing the update of access functions with in-scop defined base ptrs
This feature is currently not supported and an explicit assert to prevent the
introduction of such accesses has been added in r282893. This test case allows
to reproduce the assert (and without the assert the miscompile) added in
r282893. It will help when adding such support at some point.

llvm-svn: 292147
2017-01-16 17:51:28 +00:00
Adrian Prantl abd69332e2 Fix debug info metadata for upstream change in LLVM.
llvm-svn: 290154
2016-12-20 02:09:59 +00:00
Adrian Prantl 80d13b4545 Revert "Fix debug info metadata for upstream change in LLVM."
llvm-svn: 289983
2016-12-16 19:39:18 +00:00