Commit Graph

353 Commits

Author SHA1 Message Date
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 134a572951 [ScopDetection] Do not detect scops that exit to an unreachable
Scops that exit with an unreachable are today still permitted, but make little
sense to optimize. We therefore can already skip them during scop detection.
This speeds up scop detection in certain cases and also ensures that bugpoint
does not introduce unreachables when reducing test cases.

In practice this change should have little impact, as the performance of
unreachable code is unlikely to matter.

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

llvm-svn: 297151
2017-03-07 15:50:43 +00:00
Tobias Grosser 1c787e0b49 [ScopDetection] Do not allow required-invariant loads in non-affine region
These loads cannot be savely hoisted as the condition guarding the
non-affine region cannot be duplicated to also protect the hoisted load
later on. Today they are dropped in ScopInfo. By checking for this early, we
do not even try to model them and possibly can still optimize smaller regions
not containing this specific required-invariant load.

llvm-svn: 296744
2017-03-02 12:15:37 +00:00
Michael Kruse 52ab4943b4 Remove all references to PostDominators. NFC.
Marking a pass as preserved is necessary if any Polly pass uses it, even
if it is not preserved within the generated code. Not marking it would
cause the the Polly pass chain to be interrupted. It is not used by any
Polly pass anymore, hence we can remove all references to it.

llvm-svn: 295983
2017-02-23 15:16:22 +00:00
Tobias Grosser cd01a363d6 [ScopInfo] Add statistics to count loops after scop modeling
llvm-svn: 295431
2017-02-17 08:12:36 +00:00
Tobias Grosser 65ce9362b8 [ScopDetection] Compute the maximal loop depth correctly
Before this change, we obtained loop depth numbers that were deeper then the
actual loop depth.

llvm-svn: 295430
2017-02-17 08:08:54 +00:00
Tobias Grosser 9fe37df27c [ScopDetection] Add statistics to count the maximal number of scops in loop
llvm-svn: 294893
2017-02-12 10:52:57 +00:00
Tobias Grosser 21a059af09 Adjust formatting to commit r292110 [NFC]
llvm-svn: 292123
2017-01-16 14:08:10 +00:00
Johannes Doerfert bda814350a Allow to disable unsigned operations (zext, icmp ugt, ...)
Unsigned operations are often useful to support but the heuristics are
not yet tuned. This options allows to disable them if necessary.

llvm-svn: 288521
2016-12-02 17:55:41 +00:00
Johannes Doerfert a94ae1aede Do not allow multiple possibly aliasing ptrs in an expression
Relational comparisons should not involve multiple potentially
  aliasing pointers. Similarly this should hold for switch conditions
  and the two conditions involved in equality comparisons (separately!).
  This is a heuristic based on the C semantics that does only allow such
  operations when the base pointers do point into the same object.
  Since this makes aliasing likely we will bail out early instead of
  producing a probably failing runtime check.

llvm-svn: 288516
2016-12-02 17:49:52 +00:00
Tobias Grosser b45ae5601b [ScopDetect] Expand statistics of the detected scops
We now collect:

  Number of total loops
  Number of loops in scops
  Number of scops
  Number of scops with maximal loop depth 1
  Number of scops with maximal loop depth 2
  Number of scops with maximal loop depth 3
  Number of scops with maximal loop depth 4
  Number of scops with maximal loop depth 5
  Number of scops with maximal loop depth 6 and larger
  Number of loops in scops (profitable scops only)
  Number of scops (profitable scops only)
  Number of scops with maximal loop depth 1 (profitable scops only)
  Number of scops with maximal loop depth 2 (profitable scops only)
  Number of scops with maximal loop depth 3 (profitable scops only)
  Number of scops with maximal loop depth 4 (profitable scops only)
  Number of scops with maximal loop depth 5 (profitable scops only)
  Number of scops with maximal loop depth 6 and larger (profitable scops only)

These statistics are certainly completely accurate as we might drop scops
when building up their polyhedral representation, but they should give a good
indication of the number of scops we detect.

llvm-svn: 287973
2016-11-26 07:37:46 +00:00
Tobias Grosser 1f0236d8e5 [ScopDetect] Use mayReadOrWriteMemory to shorten condition
llvm-svn: 287525
2016-11-21 09:07:30 +00:00
Tobias Grosser b94e9b31d0 [ScopDetect] Remove unnecessary namespace qualifier
llvm-svn: 287524
2016-11-21 09:04:45 +00:00
Johannes Doerfert 6cd59e9076 Probably overwritten loads should not be considered hoistable
Do not assume a load to be hoistable/invariant if the pointer is used by
another instruction in the SCoP that might write to memory and that is
always executed.

llvm-svn: 287272
2016-11-17 22:25:17 +00:00
Tobias Grosser 70d2709b1a [ScopDetect] Conservatively handle inaccessible memory alias attributes
Commit r286294 introduced support for inaccessiblememonly and
inaccessiblemem_or_argmemonly attributes to BasicAA, which we need to
support to avoid undefined behavior. This change just refuses all calls
which are annotated with these attributes, which is conservatively correct.
In the future we may consider to model and support such function calls
in Polly.

llvm-svn: 286771
2016-11-13 19:27:24 +00:00
Tobias Grosser a2f8fa33aa [ScopDetect] Evaluate and verify branches at branch condition, not icmp
The validity of a branch condition must be verified at the location of the
branch (the branch instruction), not the location of the icmp that is
used in the branch instruction. When verifying at the wrong location, we
may accept an icmp that is defined within a loop which itself dominates, but
does not contain the branch instruction. Such loops cannot be modeled as
we only introduce domain dimensions for surrounding loops. To address this
problem we change the scop detection to evaluate and verify SCEV expressions at
the right location.

This issue has been around since at least r179148 "scop detection: properly
instantiate SCEVs to the place where they are used", where we explicitly
set the scope to the wrong location. Before this commit the scope
was not explicitly set, which probably also resulted in the scope around the
ICmp to be choosen.

This resolves http://llvm.org/PR30989

Reported-by: Eli Friedman <efriedma@codeaurora.org>
llvm-svn: 286769
2016-11-13 19:27:04 +00:00
Tobias Grosser bbaeda3fe5 Do not allow switch statements in loop latches
In r248701 "Allow switch instructions in SCoPs" support for switch statements
has been introduced, but support for switch statements in loop latches was
incomplete. This change completely disables switch statements in loop latches.

The original commit changed addLoopBoundsToHeaderDomain to support non-branch
terminator instructions, but this change was incorrect: it added a check for
BI != null to the if-branch of a condition, but BI was used in the else branch
es well. As a result, when a non-branch terminator instruction is encounted a
nullptr dereference is triggered. Due to missing test coverage, this bug was
overlooked.

r249273 "[FIX] Approximate non-affine loops correctly" added code to disallow
switch statements for non-affine loops, if they appear in either a loop latch
or a loop exit. We adapt this code to now prohibit switch statements in
loop latches even if the control condition is affine.

We could possibly add support for switch statements in loop latches, but such
support should be evaluated and tested separately.

This fixes llvm.org/PR30952

Reported-by: Eli Friedman <efriedma@codeaurora.org>
llvm-svn: 286426
2016-11-10 05:20:29 +00:00
Tobias Grosser ebb626e4b7 [ScopDetect] Use SCEVRewriteVisitor to simplify SCEVRemoveSMax rewriter
ScalarEvolution got at some pointer a SCEVRewriteVisitor. Use it to simplify
our SCEVRemoveSMax visitor.

llvm-svn: 285491
2016-10-29 06:19:34 +00:00
Michael Kruse 6a19d592da [ScopDetect] Depend transitively on ScalarEvolution.
ScopDetection might be queried by -dot-scops or -view-scops passes for which
it accesses ScalarEvolution.

llvm-svn: 284385
2016-10-17 13:29:20 +00:00
Tobias Grosser 349d1c3368 [ScopDetection] Remove redundant checks for endless loops
Summary:
Both `canUseISLTripCount()` and `addOverApproximatedRegion()` contained checks
to reject endless loops which are now removed and replaced by a single check
in `isValidLoop()`.

For reporting such loops the `ReportLoopOverlapWithNonAffineSubRegion` is
renamed to `ReportLoopHasNoExit`. The test case
`ReportLoopOverlapWithNonAffineSubRegion.ll` is adapted and renamed as well.

The schedule generation in `buildSchedule()` is based on the following
assumption:

Given some block B that is contained in a loop L and a SESE region R,
we assume that L is contained in R or the other way around.

However, this assumption is broken in the presence of endless loops that are
nested inside other loops. Therefore, in order to prevent erroneous behavior
in `buildSchedule()`, r265280 introduced a corresponding check in
`canUseISLTripCount()` to reject endless loops. Unfortunately, it was possible
to bypass this check with -polly-allow-nonaffine-loops which was fixed by adding
another check to reject endless loops in `allowOverApproximatedRegion()` in
r273905. Hence there existed two separate locations that handled this case.

Thank you Johannes Doerfert for helping to provide the above background
information.

Reviewers: Meinersbur, grosser

Subscribers: _jdoerfert, pollydev

Differential Revision: https://reviews.llvm.org/D24560

Contributed-by: Matthias Reisinger <d412vv1n@gmail.com>
llvm-svn: 281987
2016-09-20 17:05:22 +00:00
Tobias Grosser b316dc166f ScopDetection: Make sure we do not accidentally divide by zero
This code path is likely never triggered, but by still handling this case
locally we avoid warnings in clangs static analyzer.

llvm-svn: 280939
2016-09-08 14:08:05 +00:00
Tobias Grosser c80d6979bd Drop '@brief' from doxygen comments
LLVM's coding guideline suggests to not use @brief for one-sentence doxygen
comments to improve readability. Switch this once and for all to ensure people
do not copy @brief comments from other parts of Polly, when writing new code.

llvm-svn: 280468
2016-09-02 06:33:33 +00:00
Tobias Grosser 74814e1a07 Disable invariant load hoisting temporarily
With invariant load hoisting enabled the LLVM buildbots currently show some
miscompiles, which are possibly caused by invariant load hosting itself.
Confirming and fixing this requires a more in-depth analysis. To meanwhile get
back green buildbots that allow us to observe other regressions, we disable
invariant code hoisting temporarily. The relevant bug is tracked at:

http://llvm.org/PR28985

llvm-svn: 278681
2016-08-15 16:43:36 +00:00
Michael Kruse a6cc0d3a2d [ScopDetection] Remove unused DetectionContexts during expansion.
The function expandRegion() frees Region* objects again when it determines that
these are not valid SCoPs. However, the DetectionContext added to the
DetectionContextMap still holds a reference. The validity is checked using the
ValidRegions lookup table. When a new Region is added to that list, it might
share the same address, such that the DetectionContext contains two
Region* associations that are in ValidRegions, but that are unrelated and of
which one has already been free.

Also remove the DetectionContext when not a valid expansion.

llvm-svn: 278062
2016-08-08 22:39:32 +00:00
Tobias Grosser 629109b633 GPGPU: Mark kernel functions as polly.skip
Otherwise, we would try to re-optimize them with Polly-ACC and possibly even
generate kernels that try to offload themselves, which does not work as the
GPURuntime is not available on the accelerator and also does not make any
sense.

llvm-svn: 277589
2016-08-03 12:00:07 +00:00
Weiming Zhao 7614e178cb Fix a build warning of unhandled enum in switch
Summary: LLVM adds a new value FMRB_DoesNotReadMemory in the enumeration.

Reviewers: andrew.w.kaylor, chrisj, zinob, grosser, jdoerfert

Subscribers: Meinersbur, pollydev

Differential Revision: http://reviews.llvm.org/D22109

llvm-svn: 275085
2016-07-11 18:27:52 +00:00
Michael Kruse a1a303f31e Add comment on why loops/regions can overlap. NFC.
The case is described in llvm.org/PR28071 which was fixed in the
previous commit.

llvm-svn: 273906
2016-06-27 19:00:55 +00:00
Michael Kruse 41f046a282 Fix assertion due to loop overlap with nonaffine region.
Reject and report regions that contains loops overlapping nonaffine region.
This situation typically happens in the presence of inifinite loops.

This addresses bug llvm.org/PR28071.

Differential Revision: http://reviews.llvm.org/D21312

Contributed-by: Huihui Zhang <huihuiz@codeaurora.org>
llvm-svn: 273905
2016-06-27 19:00:49 +00:00
Tobias Grosser 8dd653d983 clang-tidy: apply modern-use-nullptr fixes
Instead of using 0 or NULL use the C++11 nullptr symbol when referencing null
pointers.

This cleanup was suggested by Eugene Zelenko <eugene.zelenko@gmail.com> in
http://reviews.llvm.org/D21488 and was split out to increase readability.

llvm-svn: 273435
2016-06-22 16:22:00 +00:00
Tobias Grosser ef6ae7030d ScopDetection: Make enum function-local
The 'Color' enum is only used for irreducible control flow detection. Johannes
already moved this enum in r270054 from ScopDetection.h to ScopDetection.cpp to
limit its scope to a single cpp file. We now move it into the only function
where this enum is needed to make clear that it is only needed locally in this
single function.

Thanks to Johannes for pointing out this cleanup opportunity.

llvm-svn: 272462
2016-06-11 09:00:37 +00:00
Johannes Doerfert 1dafea4114 Make the detection context non-constant [NFC]
llvm-svn: 270410
2016-05-23 09:07:08 +00:00
Johannes Doerfert 469db6a247 Move internal enum out of class declaration [NFC]
llvm-svn: 270054
2016-05-19 12:36:43 +00:00
Johannes Doerfert ffd222f2d6 Propagate the DetectionContext to the SCoP [NFC]
The SCoP now holds a reference to the ScopDetection::DetectionContext
  which allows to simplify the type of various methods and remove code.

llvm-svn: 270053
2016-05-19 12:34:57 +00:00
Johannes Doerfert f5841a66af Remove leftover debug output [NFC]
llvm-svn: 270051
2016-05-19 12:32:54 +00:00
Johannes Doerfert e6e3c9246a Check late for profitability
Before this patch we only expanded valid __and__ profitable region. Therefor
  we did not allow the expansion to create a profitable region from a
  non-profitable one.  With this patch we will remember and expand all valid
  regions and check for profitability only at the end.

  This patch increases the number of valid SCoPs in the LLVM-TS and SPEC
  2000/2006 by 28% (from 303 to 390), including the hot loop in hmmer.

llvm-svn: 269343
2016-05-12 20:21:50 +00:00
Johannes Doerfert 6c7639b380 Cleanup rejection log handling [NFC]
This patch cleans up the rejection log handling during the
  ScopDetection. It consists of two interconnected parts:
    - We keep all detection contexts for a function in order to provide
      more information to the user, e.g., about the rejection of
      extended/intermediate regions.
    - We remove the mutable "RejectLogs" member as the information is
      available through the detection contexts.

llvm-svn: 269323
2016-05-12 18:50:01 +00:00
Johannes Doerfert bf9473b2d8 Weaken profitability constraints during ScopDetection
Regions with one affine loop can be profitable if the loop is
  distributable. To this end we will allow them to be treated as
  profitable if they contain at least two non-trivial basic blocks.

llvm-svn: 269064
2016-05-10 14:42:30 +00:00
Johannes Doerfert 792374b941 Allow unsigned comparisons
With this patch we will optimistically assume that the result of an unsigned
  comparison is the same as the result of the same comparison interpreted as
  signed.

llvm-svn: 267559
2016-04-26 14:33:12 +00:00
Johannes Doerfert 517d8d2f94 Check only loop control of loops that are part of the region
This also removes a duplicated line of code in the region generator
  that caused a SPEC benchmark to fail with the new SCoPs.

llvm-svn: 267404
2016-04-25 13:37:24 +00:00
Johannes Doerfert ec8a217729 Remove unnecessary argument of the SCEVValidator [NFC]
llvm-svn: 267400
2016-04-25 13:32:36 +00:00
Johannes Doerfert 561d36b320 Allow pointer expressions in SCEVs again.
In r247147 we disabled pointer expressions because the IslExprBuilder did not
  fully support them. This patch reintroduces them by simply treating them as
  integers. The only special handling for pointers that is left detects the
  comparison of two address_of operands and uses an unsigned compare.

llvm-svn: 265894
2016-04-10 09:50:10 +00:00
Johannes Doerfert fbb63b8028 [FIX] Do not allow select as a base pointer in the SCoP region
llvm-svn: 265884
2016-04-09 21:57:13 +00:00
Johannes Doerfert 81c41b99a7 Do not allow exception handling code in SCoPs
llvm-svn: 265883
2016-04-09 21:55:58 +00:00
Johannes Doerfert d5edbd61a1 [FIX] Do not create a SCoP in the presence of infinite loops
If a loop has no exiting blocks the region covering we use during
  schedule genertion might not cover that loop properly. For now we bail
  out as we would not optimize these loops anyway.

llvm-svn: 265280
2016-04-03 23:09:06 +00:00
Tobias Grosser 151ae32dba Revert "[FIX] Do not create a SCoP in the presence of infinite loops"
This reverts commit r265260, as it caused the following 'make check-polly'
failures:

    Polly :: ScopDetect/index_from_unpredictable_loop.ll
    Polly :: ScopInfo/multiple_exiting_blocks.ll
    Polly :: ScopInfo/multiple_exiting_blocks_two_loop.ll
    Polly :: ScopInfo/schedule-const-post-dominator-walk-2.ll
    Polly :: ScopInfo/schedule-const-post-dominator-walk.ll
    Polly :: ScopInfo/switch-5.ll

llvm-svn: 265272
2016-04-03 19:36:52 +00:00
Johannes Doerfert 7dcceb82e9 [FIX] Do not create a SCoP in the presence of infinite loops
If a loop has no exiting blocks the region covering we use during
  schedule genertion might not cover that loop properly. For now we bail
  out as we would not optimize these loops anyway.

llvm-svn: 265260
2016-04-03 11:12:39 +00:00
Tobias Grosser db6db505c9 ScoPDetection: Obtain a known free diagnostic ID
... instead of hardcoding something that has been free at some point. This fixes
a crash triggered by r265084, where the diagnostic IDs have been shifted in a
way that resulted our hardcode ID to not be assigned any implementation.  Our ID
was likely already wrong earlier on, but this time we really crashed nicely.

llvm-svn: 265114
2016-04-01 07:15:19 +00:00
Johannes Doerfert 733ea34f38 [FIX] Handle accesses to "null" in MemIntrinsics
This fixes PR27035. While we now exclude MemIntrinsics from the
  polyhedral model if they would access "null" we could exploit this
  even more, e.g., remove all parameter combinations that would lead to
  the execution of this statement from the context.

llvm-svn: 264284
2016-03-24 13:50:04 +00:00
Johannes Doerfert 13d5d5b184 Remove weird comment [NFC]
llvm-svn: 264268
2016-03-24 13:16:49 +00:00
Tobias Grosser 898a636210 Add option to disallow modref function calls in scops.
This might be useful to evaluate the benefit of us handling modref funciton
calls. Also, a new bug that was triggered by modref function calls was
recently reported http://llvm.org/PR27035. To ensure the same issue does not
cause troubles for other people, we temporarily disable this until the bug
is resolved.

llvm-svn: 264140
2016-03-23 06:40:15 +00:00
Michael Kruse 09eb4451d2 Pass scope and LoopInfo to SCEVValidator. NFC.
The scope will be required in the following fix. This commit separates
the large changes that do not change behaviour from the small, but
functional change.

llvm-svn: 262664
2016-03-03 22:10:47 +00:00
Michael Kruse c7e0d9c216 Fix non-synthesizable loop exit values.
Polly recognizes affine loops that ScalarEvolution does not, in
particular those with loop conditions that depend on hoisted invariant
loads. Check for SCEVAddRec dependencies on such loops and do not
consider their exit values as synthesizable because SCEVExpander would
generate them as expressions that depend on the original induction
variables. These are not available in generated code.

llvm-svn: 262404
2016-03-01 21:44:06 +00:00
Michael Kruse 0b56681d21 [ScopDetection] Fix use-after-free.
removeCachedResults deletes the DetectionContext from
DetectionContextMap such that any it cannot be used anymore.
Unfortunately invalid<ReportUnprofitable> and RejectLogs.insert still do
use it. Because the memory is part of a map and not returned to to the
OS immediatly, such that the observable effect was only a memory leak
due to reference counters not decreased when the second call to
removeCachedResults does not remove the DetectionContext because because
it already has been removed.

Fix by not removing the DetectionContext prematurely. The second call to
removeCachedResults will handle it anyway.

llvm-svn: 262235
2016-02-29 16:54:18 +00:00
Hongbin Zheng 8efb22ef25 Enable llvm's isa/cast/dyn_cast on MemAccInst.
Differential Revision: http://reviews.llvm.org/D17250

llvm-svn: 262100
2016-02-27 01:49:58 +00:00
Tobias Grosser 8fa3e4c3fb ScopDetect/Info: Add option to disable invariant load hoisting
This is helpful for test case reduction and other experiments.

llvm-svn: 262033
2016-02-26 16:43:35 +00:00
Michael Kruse 0ac2d3e217 ScopDetection: Fix mix-up of isLoad and isStore.
This was accidentally introduced in r258947.

Thanks to Hongbin Zheng for finding this.

Found-by: etherzhhb
llvm-svn: 262032
2016-02-26 16:40:35 +00:00
Hongbin Zheng f3d6612c0a [MemAccInst] Introduce the '->' operator and remove the simple wrapper functions. NFC
llvm-svn: 261994
2016-02-26 09:47:11 +00:00
Johannes Doerfert a792098047 Support calls with known ModRef function behaviour
Check the ModRefBehaviour of functions in order to decide whether or
  not a call instruction might be acceptable.

Differential Revision: http://reviews.llvm.org/D5227

llvm-svn: 261866
2016-02-25 14:08:48 +00:00
Johannes Doerfert 8c83078449 Simplify code [NFC]
llvm-svn: 261864
2016-02-25 14:07:49 +00:00
Johannes Doerfert 9dd42ee7c1 Try to build alias checks even when non-affine accesses are allowed
From now on we bail only if a non-trivial alias group contains a non-affine
  access, not when we discover aliasing and non-affine accesses are allowed.

llvm-svn: 261863
2016-02-25 14:06:11 +00:00
Johannes Doerfert cea6193b79 Support memory intrinsics
This patch adds support for memcpy, memset and memmove intrinsics. They are
  represented as one (memset) or two (memcpy, memmove) memory accesses in the
  polyhedral model. These accesses have an access range that describes the
  summarized effect of the intrinsic, i.e.,
    memset(&A[i], '$', N);
  is represented as a write access from A[i] to A[i+N].

Differential Revision: http://reviews.llvm.org/D5226

llvm-svn: 261489
2016-02-21 19:13:19 +00:00
Tobias Grosser a2ee003239 ScopDectect: Allow memory accesses with different element types by default (try 3)
First support for this feature was committed in r259784. Support for
loop invariant load hoisting with different types was added by
Johannes Doerfert in r260045 and r260886.

llvm-svn: 260965
2016-02-16 14:37:24 +00:00
Hongbin Zheng 226232044a [Refactor] Eliminate the global variable "InsnToMemAcc".
Eliminate the global variable "InsnToMemAcc" to make Scop/ScopInfo become
  more protable, such that we can safely use them in a CallGraphSCC pass.

Differential Revision: http://reviews.llvm.org/D17238

llvm-svn: 260863
2016-02-15 00:20:58 +00:00
Tobias Grosser 5e27ec33ea Revert "[ScopDectect] Allow memory accesses with different element types by default"
This reverts commit https://llvm.org/svn/llvm-project/polly/trunk@260853

We unfortunately still have two bugs left which show only up with
-polly-process-unprofitable and which I forgot to test before committing.

llvm-svn: 260854
2016-02-14 19:59:29 +00:00
Tobias Grosser 5f105f9bdd [ScopDectect] Allow memory accesses with different element types by default
First support for this feature was committed in r259784. Support for
loop invariant load hoisting with different types was added by Johannes
Doerfert in r260045. This fixed the last known bug.

llvm-svn: 260853
2016-02-14 19:11:16 +00:00
Tobias Grosser 8ebdc2dd53 Make memory accesses with different element types optional
We also disable this feature by default, as there are still some issues in
combination with invariant load hoisting that slipped through my initial
testing.

llvm-svn: 260025
2016-02-07 08:48:57 +00:00
Tobias Grosser d840fc7277 Support accesses with differently sized types to the same array
This allows code such as:

void multiple_types(char *Short, char *Float, char *Double) {
  for (long i = 0; i < 100; i++) {
    Short[i] = *(short *)&Short[2 * i];
    Float[i] = *(float *)&Float[4 * i];
    Double[i] = *(double *)&Double[8 * i];
  }
}

To model such code we use as canonical element type of the modeled array the
smallest element type of all original array accesses, if type allocation sizes
are multiples of each other. Otherwise, we use a newly created iN type, where N
is the gcd of the allocation size of the types used in the accesses to this
array. Accesses with types larger as the canonical element type are modeled as
multiple accesses with the smaller type.

For example the second load access is modeled as:

  { Stmt_bb2[i0] -> MemRef_Float[o0] : 4i0 <= o0 <= 3 + 4i0 }

To support code-generating these memory accesses, we introduce a new method
getAccessAddressFunction that assigns each statement instance a single memory
location, the address we load from/store to. Currently we obtain this address by
taking the lexmin of the access function. We may consider keeping track of the
memory location more explicitly in the future.

We currently do _not_ handle multi-dimensional arrays and also keep the
restriction of not supporting accesses where the offset expression is not a
multiple of the access element type size. This patch adds tests that ensure
we correctly invalidate a scop in case these accesses are found. Both types of
accesses can be handled using the very same model, but are left to be added in
the future.

We also move the initialization of the scop-context into the constructor to
ensure it is already available when invalidating the scop.

Finally, we add this as a new item to the 2.9 release notes

Reviewers: jdoerfert, Meinersbur

Differential Revision: http://reviews.llvm.org/D16878

llvm-svn: 259784
2016-02-04 13:18:42 +00:00
Tobias Grosser e2c31210b2 Revert "Support loads with differently sized types from a single array"
This reverts commit (@259587). It needs some further discussions.

llvm-svn: 259629
2016-02-03 05:53:27 +00:00
Tobias Grosser 5d3fc1ea43 Support loads with differently sized types from a single array
We support now code such as:

void multiple_types(char *Short, char *Float, char *Double) {
  for (long i = 0; i < 100; i++) {
    Short[i] = *(short *)&Short[2 * i];
    Float[i] = *(float *)&Float[4 * i];
    Double[i] = *(double *)&Double[8 * i];
  }
}

To support such code we use as element type of the modeled array the smallest
element type of all original array accesses. Accesses with larger types are
modeled as multiple accesses with the smaller type.

For example the second load access is modeled as:

  { Stmt_bb2[i0] -> MemRef_Float[o0] : 4i0 <= o0 <= 3 + 4i0 }

To support jscop-rewritable memory accesses we need each statement instance to
only be assigned a single memory location, which will be the address at which
we load the value. Currently we obtain this address by taking the lexmin of
the access function. We may consider keeping track of the memory location more
explicitly in the future.

llvm-svn: 259587
2016-02-02 22:05:29 +00:00
Michael Kruse 70131d3416 Introduce MemAccInst helper class; NFC
MemAccInst wraps the common members of LoadInst and StoreInst. Also use
of this class in:
- ScopInfo::buildMemoryAccess
- BlockGenerator::generateLocationAccessed
- ScopInfo::addArrayAccess
- Scop::buildAliasGroups
- Replace every use of polly::getPointerOperand

Reviewers: jdoerfert, grosser

Differential Revision: http://reviews.llvm.org/D16530

llvm-svn: 258947
2016-01-27 17:09:17 +00:00
Tobias Grosser 1c3a6d7808 ScopDetection: Do not detect regions with irreducible control as scops
Polly currently does not support irreducible control and it is probably not
worth supporting. This patch adds code that checks for irreducible control
and refuses regions containing irreducible control.

Polly traditionally had rather restrictive checks on the control flow structure
which would have refused irregular control, but within the last couple of months
most of the control flow restrictions have been removed. As part of this
generalization we accidentally allowed irregular control flow.

Contributed-by: Karthik Senthil and Ajith Pandel
llvm-svn: 258497
2016-01-22 09:44:37 +00:00
Tobias Grosser c6424ae46c ScopDetection: Simplify std::distance(....) to BB->size()
Suggested by: Johannes Doerfert <doerfert@cs.uni-saarland.de>

llvm-svn: 256260
2015-12-22 17:38:59 +00:00
Tobias Grosser c1a269bf0e Add option to assume single-loop scops with sufficient compute are profitable
If a loop has a sufficiently large amount of compute instruction in its loop
body, it is unlikely that our rewrite of the loop iterators introduces large
performance changes. As Polly can also apply beneficical optimizations (such
as parallelization) to such loop nests, we mark them as profitable.

This option is currently "disabled" by default, but can be used to run
experiments. If enabled by setting it e.g. to 40 instructions, we currently
see some compile-time increases on LNT without any significant run-time
changes.

llvm-svn: 256199
2015-12-21 21:00:43 +00:00
Tobias Grosser 5624d3c978 Adjust formatting to clang-format changes in 256149
llvm-svn: 256151
2015-12-21 12:38:56 +00:00
Tobias Grosser 97fc5bb7f7 ScopDetect: Extract profitability check into subfunction
.. and add some documentation. We also simplify the code by dropping an early
check that is also covered by the the later checks. This might have a small
compile time impact, but as the scops that are skipped are small we should
probably only add this back in the unlikely case that this has a notable
compile-time cost.

No functional change intended.

llvm-svn: 256149
2015-12-21 12:14:48 +00:00
Tobias Grosser 594882573e ScopInfo: Return immediately if scop is unprofitable and marked invalid
As we already log an error when calling invalid, scops unprofitable scops are in
any case marked invalid, but returning immediately safes (a tiny bit of) compile
time and is consistent with our use of 'invalid' in the remainder of the file.

Found by inspection.

llvm-svn: 256140
2015-12-21 09:09:44 +00:00
Tobias Grosser bfaf1ae309 ScopInfo: Return in case we found an invalid array size
Without this return we still log the incorrect array size (and do not detect
this scop), but we would unnecessarily continue to verify that access functions
are affine. As we do not need to do this, we can return right ahead and
consequently safe compile time.

This issue was found by inspection.

llvm-svn: 256139
2015-12-21 09:09:39 +00:00
Michael Kruse 8fc2896ee0 Compile fix: Use "&&" operator instead of "and"
llvm-svn: 256124
2015-12-20 14:42:32 +00:00
Roman Gareev 8aa437503c Fix delinearization of fortran arrays
The patch fixes Bug 25759 produced by inappropriate handling of unsigned
maximum SCEV expressions by SCEVRemoveMax. Without a fix, we get an infinite
loop and a segmentation fault, if we try to process, for example,
'((-1 + (-1 * %b1)) umax {(-1 + (-1 * %yStart)),+,-1}<%.preheader>)'.
It also fixes a potential issue related to signed maximum SCEV expressions.

Tested-by: Roman Gareev <gareevroman@gmail.com>
Fixed-by: Tobias Grosser <tobias@grosser.es>

Differential Revision: http://reviews.llvm.org/D15563

llvm-svn: 255922
2015-12-17 20:37:17 +00:00
Tobias Grosser 2f8e43d677 ScopInfo: Add support for delinearizing fortran arrays
gfortran (and fortran in general?) does not compute the address of an array
element directly from the array sizes (e.g., %s0, %s1), but takes first the
maximum of the sizes and 0 (e.g., max(0, %s0)) before multiplying the resulting
value with the per-dimension array subscript expressions. To successfully
delinearize index expressions as we see them in fortran, we first filter 'smax'
expressions out of the SCEV expression, use them to guess array size parameters
and only then continue with the existing delinearization.

llvm-svn: 253995
2015-11-24 17:06:38 +00:00
Tobias Grosser d68ba42556 ScopInfo: Split hasAffineMemoryAccesses() into multiple functions [NFC]
This makes the overall code more readable.

llvm-svn: 253951
2015-11-24 05:00:36 +00:00
Johannes Doerfert a2a74f09fc Do not enforce lcssa
At some point we enforced lcssa for the loop surrounding the entry block.
  This is not only questionable as it does not check any other loop but also
  not needed any more.

llvm-svn: 253789
2015-11-21 17:00:02 +00:00
Johannes Doerfert 48fe86f1ff Emit SCoP source location as remark during ScopInfo
This removes a similar feature from ScopDetection, though with
  -polly-report that feature present twice anyway.

llvm-svn: 252846
2015-11-12 02:32:32 +00:00
Tobias Grosser b12b006c4b ScopDetection: Do not allow blocks to reference operands in error blocks
r252713 introduced a couple of regressions due to later basic blocks refering
to instructions defined in error blocks which have not yet been modeled.

This commit is currently just encoding limitations of our modeling and code
generation backends to ensure correctness. In theory, we should be able to
generate and optimize such regions, as everything that is dominated by an error
region is assumed to not be executed anyhow. We currently just lack the code
to make this happen in practice.

llvm-svn: 252725
2015-11-11 12:44:18 +00:00
Tobias Grosser b76cd3cc56 ScopInfo: Pass domain constraints through error blocks
Previously, we just skipped error blocks during scop construction. With
this change we make sure we can construct domains for error blocks such that
these domains can be forwarded to subsequent basic blocks.

This change ensures that basic blocks that post-dominate and are dominated by
a basic block that branches to an error condition have the very same iteration
domain as the branching basic block. Before, this change we would construct
a domain that excludes all error conditions. Such domains could become _very_
complex and were undesirable to build.

Another solution would have been to drop these constraints using a
dominance/post-dominance check instead of modeling the error blocks. Such
a solution could also work in case of unreachable statements or infinite
loops in the scop. However, as we currently (to my believe incorrectly) model
unreachable basic blocks in the post-dominance tree, such a solution is not
yet feasible and requires first a change to LLVM's post-dominance tree
construction.

This commit addresses the most sever compile time issue reported in:
http://llvm.org/PR25458

llvm-svn: 252713
2015-11-11 08:42:20 +00:00
Tobias Grosser f423c1200f Remove old and redundant options
We remove -polly-detect-unprofitable and -polly-no-early-exit. Both have been
superseeded by -polly-process-unprofitable and were only kept as aliases for
our buildbots to continue to work. As all buildbots have been moved to the new
options, we can now remove the old ones for good.

llvm-svn: 251787
2015-11-02 10:13:32 +00:00
Tobias Grosser bf45e74254 ScopDetect: Bail out for non-simple memory accesses
Volatile or atomic memory accesses are currently not supported. Neither did
we think about any special handling needed nor do we support the unknown
instructions the alias set tracker turns them into sometimes. Before this
patch, us not supporting unkown instructions in an alias set caused the
following assertion failures:

Assertion `AG.size() > 1 && "Alias groups should contain at least two accesses"'
failed

llvm-svn: 251234
2015-10-25 13:48:40 +00:00
Tobias Grosser 907090c37c ScopDetection: Update DetectionContextMap accordingly
When verifying if a scop is still valid we rerun all analysis, but did not
update DetectionContextMap. This change ensures that information, e.g. about
non-affine regions, is correctly updated

llvm-svn: 251227
2015-10-25 10:55:35 +00:00
Tobias Grosser 51174cca30 ScopDetection: Do not crash if we find zero array size candidates for delinearization
llvm-svn: 251226
2015-10-25 08:40:44 +00:00
Tobias Grosser 5528dcdf25 ScopDetection: Always refuse multi-dimensional memory accesses with 'undef' in
the size expression.

We previously only checked if the size expression is 'undef', but allowed size
expressions of the form 'undef * undef' by accident. After this change we now
require size expressions to be affine which implies no 'undef' appears anywhere
in the expression.

llvm-svn: 251225
2015-10-25 08:40:38 +00:00
Johannes Doerfert 9c28bfa72c [FIX] Only constant integer branch conditions are always affine
There are several different kinds of constants that could occur in a
  branch condition, however we can only handle the most interesting one
  namely constant integers. To this end we have to treat others as
  non-affine.

  This fixes bug 25244.

llvm-svn: 250669
2015-10-18 22:56:42 +00:00
Johannes Doerfert 01978cfa0c Remove independent blocks pass
Polly can now be used as a analysis only tool as long as the code
  generation is disabled. However, we do not have an alternative to the
  independent blocks pass in place yet, though in the relevant cases
  this does not seem to impact the performance much. Nevertheless, a
  virtual alternative that allows the same transformations without
  changing the input region will follow shortly.

llvm-svn: 250652
2015-10-18 12:28:00 +00:00
Tobias Grosser e2c8275346 ScopInfo: Allow simple 'AddRec * Parameter' products in delinearization
We also allow such products for cases where 'Parameter' is loaded within the
scop, but where we can dynamically verify that the value of 'Parameter' remains
unchanged during the execution of the scop.

This change relies on Polly's new RequiredILS tracking infrastructure recently
contributed by Johannes.

llvm-svn: 250019
2015-10-12 08:02:30 +00:00
Tobias Grosser 3ecb71696b Add back -polly-detect-unprofitable as alias of -polly-process-unprofitable
This flag was still used in our LNT server. We leave it until it has been
removed from LNT as well.

llvm-svn: 249973
2015-10-11 13:39:17 +00:00
Johannes Doerfert 9b1f9c8b61 Allow eager evaluated binary && and || conditions
The domain generation can handle lazy && and || by default but eager
  evaluated expressions were dismissed as non-affine. With this patch we
  will allow arbitrary combinations of and/or bit-operations in the
  conditions of branches.

Differential Revision: http://reviews.llvm.org/D13624

llvm-svn: 249971
2015-10-11 13:21:03 +00:00
Johannes Doerfert f363ed9804 [NFC] Move helper functions to ScopHelper
Helper functions in the BlockGenerators.h/cpp introduce dependences
  from the frontend to the backend of Polly. As they are used in
  ScopDetection, ScopInfo, etc. we move them to the ScopHelper file.

llvm-svn: 249919
2015-10-09 23:40:24 +00:00
Johannes Doerfert c7ab83dfb7 Remove unused flag polly-allow-non-scev-backedge-taken-count
Drop an unused flag polly-allow-non-scev-backedge-taken-count and also
  its occurrences from the tests.

Contributed-by: Chris Jenneisch <chrisj@codeaurora.org>

Differential Revision: http://reviews.llvm.org/D13400

llvm-svn: 249675
2015-10-08 10:05:48 +00:00
Johannes Doerfert c06b7d67cd Expose the detection context to ScopDetection users
ScopDetection users are interested in the detection context and access
  these via different get-methods. However, not all information was
  exposed though the number of maps to hold it was increasing steadily.
  With this change only the detection contexts the rejection log and the
  ValidRegions set are mapped. The former is needed, the second could be
  integrated in the first and the ValidRegions set is only needed for the
  deterministic order of the regions.

llvm-svn: 249614
2015-10-07 20:46:06 +00:00
Johannes Doerfert 08d90a3cee Treat conditionally executed non-pure calls as errors
This replaces the support for user defined error functions by a
  heuristic that tries to determine if a call to a non-pure function
  should be considered "an error". If so the block is assumed not to be
  executed at runtime. While treating all non-pure function calls as
  errors will allow a lot more regions to be analyzed, it will also
  cause us to dismiss a lot again due to an infeasible runtime context.
  This patch tries to limit that effect. A non-pure function call is
  considered an error if it is executed only in conditionally with
  regards to a cheap but simple heuristic.

llvm-svn: 249611
2015-10-07 20:32:43 +00:00