Commit Graph

17 Commits

Author SHA1 Message Date
Fangrui Song a36ddf0aa9 Migrate function attribute "no-frame-pointer-elim"="false" to "frame-pointer"="none" as cleanups after D56351 2019-12-24 16:27:51 -08:00
Michael Kruse a43ba2d84f [ScopBuilder] Make -polly-stmt-granularity=scalar-indep the default.
Splitting basic blocks into multiple statements if there are now
additional scalar dependencies gives more freedom to the scheduler, but
more statements also means higher compile-time complexity. Switch to
finer statement granularity, the additional compile time should be
limited by the number of operations quota.

The regression tests are written for the -polly-stmt-granularity=bb
setting, therefore we add that flag to those tests that break with the
new default. Some of the tests only fail because the statements are
named differently due to a basic block resulting in multiple statements,
but which are removed during simplification of statements without
side-effects. Previous commits tried to reduce this effect, but it is
not completely avoidable.

Differential Revision: https://reviews.llvm.org/D42151

llvm-svn: 324169
2018-02-03 06:59:47 +00:00
Philip Pfaffe 00fd43b327 Port ScopInfo to the isl cpp bindings
Summary:
Most changes are mechanical, but in one place I changed the program semantics
by fixing a likely bug:

In `Scop::hasFeasibleRuntimeContext()`, I'm now explicitely handling the
error-case. Before, when the call to `addNonEmptyDomainConstraints()`
returned a null set, this (probably) accidentally worked because
isl_bool_error converts to true. I'm checking for nullptr now.

Reviewers: grosser, Meinersbur, bollu

Reviewed By: Meinersbur

Subscribers: nemanjai, kbarton, pollydev, llvm-commits

Differential Revision: https://reviews.llvm.org/D39971

llvm-svn: 318632
2017-11-19 22:13:34 +00:00
Michael Kruse 68821a8b91 [ZoneAlgo/ForwardOpTree] Normalize PHIs to their known incoming values.
Represent PHIs by their incoming values instead of an opaque value of
themselves. This allows ForwardOpTree to "look through" the PHIs and
forward the incoming values since forwardings PHIs is currently not
supported.

This is particularly useful to cope with PHIs inserted by GVN LoadPRE.
The incoming values all resolve to a load from a single array element
which then can be forwarded.

It should in theory also reduce spurious conflicts in value mapping
(DeLICM), but I have not yet found a profitable case yet, so it is
not included here.

To avoid transitive closure and potentially necessary overapproximations
of those, PHIs that may reference themselves are excluded from
normalization and keep their opaque self-representation.

Differential Revision: https://reviews.llvm.org/D39333

llvm-svn: 317008
2017-10-31 16:11:46 +00:00
Michael Kruse 822dfe271b [ForwardOpTree] Reload know values.
For scalar accesses, change the access target to an array element that
is known to contain the same value.

This may become an alternative to forwardKnownLoad which creates new
loads (and therefore closer to forwarding speculatives). Reloading does
not require the known value originating from a load, but can be a store
as well.

Differential Revision: https://reviews.llvm.org/D39325

llvm-svn: 316766
2017-10-27 14:26:14 +00:00
Michael Kruse ef8325ba50 [ForwardOpTree] Test the max operations quota.
cl::opt<unsigned long> is not specialized and hence the option
-polly-optree-max-ops impossible to use.

Replace by supported option cl::opt<unsigned>.

Also check for an error state when computing the written value, which
happens when the quota runs out.

llvm-svn: 313546
2017-09-18 17:43:50 +00:00
Michael Kruse bd84ce8931 [ZoneAlgo] Handle non-StoreInst/LoadInst MemoryAccesses including memset.
Up to now ZoneAlgo considered array elements access by something else
than a LoadInst or StoreInst as not analyzable. This patch removes that
restriction by using the unknown ValInst to describe the written
content, repectively the element type's null value in case of memset.

Differential Revision: https://reviews.llvm.org/D37362

llvm-svn: 312630
2017-09-06 12:40:55 +00:00
Tobias Grosser d6e0679c4e [ForwardOp] Remove read accesses for all instructions that have been moved
Before this patch, OpTree did not consider forwarding an operand tree consisting
of only single LoadInst as useful. The motivation was that, like an access to a
read-only variable, it would just replace one MemoryAccess by another. However,
in contrast to read-only accesses, this would replace a scalar access by an
array access, which is something worth doing.

In addition, leaving scalar MemoryAccess is problematic in that VirtualUse
prioritizes inter-Stmt use over intra-Stmt. It was possible that the same LLVM
value has a MemoryAccess for accessing the remote Stmt's LoadInst as well as
having the same LoadInst in its own instruction list (due to being forwarded
from another operand tree).

With this patch we ensure that if a LoadInst is forwarded is any operand tree,
also the operand tree containing just the LoadInst is forwarded as well, which
effectively removes the scalar MemoryAccess such that only the array access
remains, not both.

Thanks Michael for the detailed explanation.

Reviewers: Meinersbur, bellu, singam-sanjay, gareevroman

Subscribers: hfinkel, pollydev, llvm-commits

Tags: #polly

Differential Revision: https://reviews.llvm.org/D37424

llvm-svn: 312456
2017-09-03 19:52:15 +00:00
Tobias Grosser 2307f86c47 [ForwardOpTree] Allow forwarding in the presence of region statements
Summary:
After region statements now also have instruction lists, this is a
straightforward extension.

Reviewers: Meinersbur, bollu, singam-sanjay, gareevroman

Reviewed By: Meinersbur

Subscribers: hfinkel, pollydev, llvm-commits

Tags: #polly

Differential Revision: https://reviews.llvm.org/D37298

llvm-svn: 312249
2017-08-31 16:04:49 +00:00
Michael Kruse 4728184342 [ZoneAlgo] More fine-grained bail-out.
ZoneAlgo used to bail out for the complete SCoP if it encountered
something violating its assumption. This meant the neither OpTree can
forward any load nor DeLICM do anything in such cases, even if their
transformations are unrelated to the violations.

This patch adds a list of compatible elements (currently with the
granularity of entire arrays) that can be used for analysis. OpTree
and DeLICM can then check whether their transformations only concern
compatible elements, and skip non-compatible ones.

This will be useful for e.g. Polybench's benchmarks covariance,
correlation, bicg, doitgen, durbin, gramschmidt, adi that have
assumption violation, but which are not necessarily relevant
for all transformations.

Differential Revision: https://reviews.llvm.org/D37219

llvm-svn: 311929
2017-08-28 20:39:07 +00:00
Michael Kruse 235726ee4b [test] Add descriptions and pseudocode to tests. NFC.
llvm-svn: 310385
2017-08-08 17:26:19 +00:00
Tobias Grosser 2ef378120d [ZoneAlgo] Allow two writes that write identical values into same array slot
Two write statements which write into the very same array slot generally are
conflicting. However, in case the value that is written is identical, this
does not cause any problem. Hence, allow such write pairs in this specific
situation.

llvm-svn: 310311
2017-08-07 22:01:29 +00:00
Michael Kruse 70af4f579d [ForwardOpTree] Use known array content analysis to forward load instructions.
This is an addition to the -polly-optree pass that reuses the array
content analysis from DeLICM to find array elements that contain the
same value as the value loaded when the target statement instance
is executed.

The analysis is now enabled by default.

The known content analysis could also be used to rematerialize any
llvm::Value that was written to some array element, but currently
only loads are forwarded.

Differential Revision: https://reviews.llvm.org/D36380

llvm-svn: 310279
2017-08-07 18:40:29 +00:00
Michael Kruse 9f6e41cdba [ForwardOpTree] Support synthesizable values.
This allows -polly-optree to move instructions that depend on
synthesizable values.

The difficulty for synthesizable values is that their value depends on
the location. When it is moved over a loop header, and the SCEV
expression depends on the loop induction variable (SCEVAddRecExpr), it
would use the current induction variable instead of the last one.

At the moment we cannot forward PHI nodes such that crossing the header
of loops referenced by SCEVAddRecExpr is not possible (assuming the loop
header has at least two incoming blocks: for entering the loop and the
backedge, such any instruction to be forwarded must have a phi between
use and definition).

A remaining issue is when the forwarded value is used after the loop,
but is only synthesizable inside the loop. This happens e.g. if
ScalarEvolution is unable to determine the number of loop iterations or
the initial loop value. We do not forward in this situation.

Differential Revision: https://reviews.llvm.org/D36102

llvm-svn: 309609
2017-07-31 19:46:21 +00:00
Michael Kruse 07e8c36dc7 [ForwardOpTree] Support read-only value uses.
Read-only values (values defined before the SCoP) require special
handing with -polly-analyze-read-only-scalars=true (which is the
default). If active, each use of a value requires a read access.
When a copied value uses a read-only value, we must also ensure that
such a MemoryAccess is available or is created.

Differential Revision: https://reviews.llvm.org/D35764

llvm-svn: 308876
2017-07-24 12:43:27 +00:00
Michael Kruse e5f4706a55 [ForwardOpTree] Support hoisted invariant loads.
Hoisted loads can be trivially supported because there are no
MemoryAccess to be modified, the loaded value is just available
at code generation.

llvm-svn: 308826
2017-07-22 14:30:02 +00:00
Michael Kruse a6b2de3b59 [ForwardOpTree] Introduce the -polly-optree pass.
This pass 'forwards' operand trees into statements that use them in
order to avoid scalar dependencies.

This minimal implementation handles only the case of speculatable
instructions. We will successively add support for:
- Hoisted loads
- Read-only values
- Synthesizable values
- Loads
- PHIs
- Forwarding only parts of the tree

Differential Revision: https://reviews.llvm.org/D35754

llvm-svn: 308825
2017-07-22 14:02:47 +00:00