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
ScopStmts were being used in the computation of the Domain of the SCoPs
in ScopInfo. Once statements are split, there will not be a 1-to-1
correspondence between Stmts and Basic blocks. Thus this patch avoids
the use of getStmtFor() by creating a map of BB to InvalidDomain and
using it to compute the domain of the statements.
Contributed-by: Nanidini Singhal <cs15mtech01004@iith.ac.in>
Differential Revision: https://reviews.llvm.org/D33942
llvm-svn: 306667
Summary:
My goal is to make the newly added `AllowWholeFunctions` options more usable/powerful.
The changes to ScopBuilder.cpp are exclusively checks to prevent `Region.getExit()` from being dereferenced, since Top Level Regions (TLRs) don't have an exit block.
In ScopDetection's `isValidCFG`, I removed a check that disallowed ReturnInstructions to have return values. This might of course have been intentional, so I would welcome your feedback on this and maybe a small explanation why return values are forbidden. Maybe it can be done but needs more changes elsewhere?
The remaining changes in ScopDetection are simply to consider the AllowWholeFunctions option in more places, i.e. allow TLRs when it is set and once again avoid derefererncing `getExit()` if it doesn't exist.
Finally, in ScopHelper.cpp I extended `polly::isErrorBlock` to handle regions without exit blocks as well: The original check was if a given BasicBlock dominates all predecessors of the exit block. Therefore I do the same for TLRs by regarding all BasicBlocks terminating with a ReturnInst as predecessors of a "virtual" function exit block.
Patch by: Lukas Boehm
Reviewers: philip.pfaffe, grosser, Meinersbur
Reviewed By: grosser
Subscribers: pollydev, llvm-commits, bollu
Tags: #polly
Differential Revision: https://reviews.llvm.org/D33411
llvm-svn: 303790
At the time of code generation, an instruction with an llvm intrinsic is ignored
in copyBB. However, if the value of the instruction is used later in the
program, the value needs to be synthesized. However, this is causing some issues
with the instructions being generated in a hoisted basic block.
Removing llvm.expect from the list of ignored intrinsics fixes this bug.
This resolves http://llvm.org/PR32324.
Contributed-by: Annanay Agarwal <cs14btech11001@iith.ac.in>
Tags: #polly
Differential Revision: https://reviews.llvm.org/D32992
llvm-svn: 303006
Introduce ScopStmt::getSurroundingLoop() to replace getFirstNonBoxedLoopFor.
getSurroundingLoop() returns the precomputed surrounding/first non-boxed
loop. Except in ScopDetection, the list of boxed loops is only used to
get the surrounding loop. getFirstNonBoxedLoopFor also requires LoopInfo
at every use which is not necessarily available everywhere where we may
want to use it.
Differential Revision: https://reviews.llvm.org/D30985
llvm-svn: 297899
Move the function getFirstNonBoxedLoopFor which is used in ScopBuilder
and in ScopInfo to Support/ScopHelpers to make it reusable in other
locations. No functionality change.
Patch by Sameer Abu Asal.
Differential Revision: https://reviews.llvm.org/D28754
llvm-svn: 292168
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
The declaration as an "error block" is currently aggressive and not very
smart. This patch allows to disable error blocks completely. This might
be useful to prevent SCoP expansion to a point where the assumed context
becomes infeasible, thus the SCoP has to be discarded.
llvm-svn: 287271
This makes polly generate a CFG which is closer to what we want
in LLVM IR, with a loop preheader for the original loop. This is
just a cleanup, but it exposes some fragile assumptions.
I'm not completely happy with the changes related to expandCodeFor;
RTCBB->getTerminator() is basically a random insertion point which
happens to work due to the way we generate runtime checks. I'm not
sure what the right answer looks like, though.
Differential Revision: https://reviews.llvm.org/D26053
llvm-svn: 285864
This function is used by both ScopInfo and ScopBuilder. A common
location for this function is required when ScopInfo and ScopBuilder are
separated into separate files in the next commit.
llvm-svn: 273981
IntToPtr and PtrToInt instructions are basically no-ops that we can handle as
such. In order to generate them properly as parameters we had to improve the
ScopExpander, though the change is the first in the direction of a more
aggressive scalar synthetization.
This patch was originally contributed by Johannes Doerfert in r271888, but was
in conflict with the revert in r272483. This is a recommit with some minor
adjustment to the test cases to take care of differing instruction names.
llvm-svn: 272485
The recent expression type changes still need more discussion, which will happen
on phabricator or on the mailing list. The precise list of commits reverted are:
- "Refactor division generation code"
- "[NFC] Generate runtime checks after the SCoP"
- "[FIX] Determine insertion point during SCEV expansion"
- "Look through IntToPtr & PtrToInt instructions"
- "Use minimal types for generated expressions"
- "Temporarily promote values to i64 again"
- "[NFC] Avoid unnecessary comparison for min/max expressions"
- "[Polly] Fix -Wunused-variable warnings (NFC)"
- "[NFC] Simplify min/max expression generation"
- "Simplify the type adjustment in the IslExprBuilder"
Some of them are just reverted as we would otherwise get conflicts. I will try
to re-commit them if possible.
llvm-svn: 272483
IntToPtr and PtrToInt instructions are basically no-ops that we can handle as
such. In order to generate them properly as parameters we had to improve the
ScopExpander, though the change is the first in the direction of a more
aggressive scalar synthetization.
llvm-svn: 271888
When we materialize parameter SCEVs we did so without considering the
side effects they might have, e.g., both division and modulo are
undefined if the right hand side is zero. This is a problem because we
potentially extended the domain under which we evaluate parameters,
thus we might have introduced such undefined behaviour. To prevent
that from happening we will now guard divisions and modulo operations
in the parameters with a compare and select.
llvm-svn: 268023
This reverts commit 2879c53e80e05497f408f21ce470d122e9f90f94.
Additionally, it adds SDiv and SRem instructions to the set of values
discovered by the findValues function even if we add the operands to
be able to recompute the SCEVs. In subfunctions we do not want to
recompute SDiv and SRem instructions but pass them instead as they
might have been created through the IslExprBuilder and are more
complicated than simple SDiv/SRem instructions in the code.
llvm-svn: 265873
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
The previously implemented approach is to follow value definitions and
create write accesses ("push defs") while searching for uses. This
requires the same relatively validity- and requirement conditions to be
replicated at multiple locations (PHI instructions, other instructions,
uses by PHIs).
We replace this by iterating over the uses in a SCoP ("pull in
requirements"), and add writes only when at least one read has been
added. It turns out to be simpler code because each use is only iterated
over once and writes are added for the first access that reads it. We
need another iteration to identify escaping values (uses not in the
SCoP), which also makes the difference between such accesses more
obvious. As a side-effect, the order of scalar MemoryAccess can change.
Differential Revision: http://reviews.llvm.org/D15706
llvm-svn: 259987
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
Basic blocks that are always executed can not be error blocks as their execution
can not possibly be an unlikely event. In this commit we tighten the check
if an error block to basic blcoks that do not dominate the exit condition, but
that dominate all exiting blocks of the scop.
llvm-svn: 252726
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
Remove all the implicit ilist iterator conversions from polly, in
preparation for making them illegal in ADT. There was one oddity I came
across: at line 95 of lib/CodeGen/LoopGenerators.cpp, there was a
post-increment `Builder.GetInsertPoint()++`.
Since it was a no-op, I removed it, but I admit I wonder if it might be
a bug (both before and after this change)? Perhaps it should be a
pre-increment?
llvm-svn: 252357
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
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
This patch allows invariant loads to be used in the SCoP description,
e.g., as loop bounds, conditions or in memory access functions.
First we collect "required invariant loads" during SCoP detection that
would otherwise make an expression we care about non-affine. To this
end a new level of abstraction was introduced before
SCEVValidator::isAffineExpr() namely ScopDetection::isAffine() and
ScopDetection::onlyValidRequiredInvariantLoads(). Here we can decide
if we want a load inside the region to be optimistically assumed
invariant or not. If we do, it will be marked as required and in the
SCoP generation we bail if it is actually not invariant. If we don't
it will be a non-affine expression as before. At the moment we
optimistically assume all "hoistable" (namely non-loop-carried) loads
to be invariant. This causes us to expand some SCoPs and dismiss them
later but it also allows us to detect a lot we would dismiss directly
if we would ask e.g., AliasAnalysis::canBasicBlockModify(). We also
allow potential aliases between optimistically assumed invariant loads
and other pointers as our runtime alias checks are sound in case the
loads are actually invariant. Together with the invariant checks this
combination allows to handle a lot more than LICM can.
The code generation of the invariant loads had to be extended as we
can now have dependences between parameters and invariant (hoisted)
loads as well as the other way around, e.g.,
test/Isl/CodeGen/invariant_load_parameters_cyclic_dependence.ll
First, it is important to note that we cannot have real cycles but
only dependences from a hoisted load to a parameter and from another
parameter to that hoisted load (and so on). To handle such cases we
materialize llvm::Values for parameters that are referred by a hoisted
load on demand and then materialize the remaining parameters. Second,
there are new kinds of dependences between hoisted loads caused by the
constraints on their execution. If a hoisted load is conditionally
executed it might depend on the value of another hoisted load. To deal
with such situations we sort them already in the ScopInfo such that
they can be generated in the order they are listed in the
Scop::InvariantAccesses list (see compareInvariantAccesses). The
dependences between hoisted loads caused by indirect accesses are
handled the same way as before.
llvm-svn: 249607
There have been various places where llvm::DenseMap<const llvm::Value *,
llvm::Value *> types have been defined, but all types have been expected to be
identical. We make this more clear by consolidating the different types and use
BlockGenerator::ValueMapT wherever there is a need for types to match
BlockGenerator::ValueMapT.
llvm-svn: 249264
The user can provide function names with
-polly-error-functions=name1,name2,name3
that will be treated as error functions. Any call to them is assumed
not to be executed.
This feature is mainly for developers to play around with the new
"error block" feature.
llvm-svn: 249098
Because we handle more than SCEV does it is not possible to rewrite an
expression on the top-level using the SCEVParameterRewriter only. With
this patch we will do the rewriting on demand only and also
recursively, thus not only on the top-level.
llvm-svn: 248916
This patch allows switch instructions with affine conditions in the
SCoP. Also switch instructions in non-affine subregions are allowed.
Both did not require much changes to the code, though there was some
refactoring needed to integrate them without code duplication.
In the llvm-test suite the number of profitable SCoPs increased from
135 to 139 but more importantly we can handle more benchmarks and user
inputs without preprocessing.
Differential Revision: http://reviews.llvm.org/D13200
llvm-svn: 248701
Hoist runtime checks in the loop nest if they guard an "error" like event.
Such events are recognized as blocks with an unreachable terminator or a call
to the ubsan function that deals with out of bound accesses. Other "error"
events can be added easily.
We will ignore these blocks when we detect/model/optmize and code generate SCoPs
but we will make sure that they would not have been executed using the assumption
framework.
llvm-svn: 247310
As we do not rely on ScalarEvolution any more we do not need to get
the backedge taken count. Additionally, our domain generation handles
everything that is affine and has one latch and our ScopDetection will
over-approximate everything else.
This change will therefor allow loops with:
- one latch
- exiting conditions that are affine
Additionally, it will not check for structured control flow anymore.
Hence, loops and conditionals are not necessarily single entry single
exit regions any more.
Differential Version: http://reviews.llvm.org/D12758
llvm-svn: 247289
The SCEVExpander cannot deal with all SCEVs Polly allows in all kinds
of expressions. To this end we introduce a ScopExpander that handles
the additional expressions separatly and falls back to the
SCEVExpander for everything else.
Reviewers: grosser, Meinersbur
Subscribers: #polly
Differential Revision: http://reviews.llvm.org/D12066
llvm-svn: 245288
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
RegionInfo::splitBlock did not update RegionInfo correctly. Specifically, it tried to make the new block the entry block if possible. This breaks for nested regions that have edges to the old block.
We simply do not change the entry block. Updating RegionInfo becomes trivial as both block will always be in the same region.
splitEntryBlockForAlloca makes use of the new splitBlock.
Reviewers: grosser
Part of Differential Revision: http://reviews.llvm.org/D11867
llvm-svn: 244600
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
Siddharth Bhat