Commit Graph

70 Commits

Author SHA1 Message Date
Nicolas Vasilache
a490d387e6 [mlir][Vector] Add ExtractOp folding when fed by a TransposeOp
TransposeOp are often followed by ExtractOp.
In certain cases however, it is unnecessary (and even detrimental) to lower a TransposeOp to either a flat transpose (llvm.matrix intrinsics) or to unrolled scalar insert / extract chains.

Providing foldings of ExtractOp mitigates some of the unnecessary complexity.

Differential revision: https://reviews.llvm.org/D83487
2020-07-10 11:09:27 -04:00
Nicolas Vasilache
24ed3a9403 [mlir][Vector] Add ExtractOp folding
This revision adds foldings for ExtractOp operations that come from previous InsertOp.
InsertOp have cumulative semantic where multiple chained inserts are necessary to produce the final value from which the extracts are obtained.
Additionally, TransposeOp may be interleaved and need to be tracked in order to follow the producer consumer relationships and properly compute positions.

Differential revision: https://reviews.llvm.org/D83150
2020-07-07 16:48:49 -04:00
River Riddle
9db53a1827 [mlir][NFC] Remove usernames and google bug numbers from TODO comments.
These were largely leftover from when MLIR was a google project, and don't really follow LLVM guidelines.
2020-07-07 01:40:52 -07:00
Chintan Kaur
78453e3705 Mark AffineMap::replaceDimsAndSymbols as const (NFC)
This is consistent to the other methods of the class, as well as
AffineExpr::replaceDimsAndSymbols.

Differential Revision: https://reviews.llvm.org/D80266
2020-05-20 03:11:41 +00:00
Mehdi Amini
051452bdb1 Remove spurious semicolon after function definition (NFC)
This fixes some GCC pedantic warnings.
2020-05-17 23:15:17 +00:00
Alex Zinenko
a87db48e6f [mlir] Support partial folding of affine.min/max
Originally, these operations were folded only if all expressions in their
affine maps could be folded to a constant expression that can be then subject
to numeric min/max computation. This introduces a more advanced version that
partially folds the affine map by lifting individual constant expression in it
even if some of the expressions remain variable. The folding can update the
operation in place to use a simpler map. Note that this is not as powerful as
canonicalization, in particular this does not remove dimensions or symbols that
became useless. This allows for better composition of Linalg tiling and
promotion transformation, where the latter can handle some canonical forms of
affine.min that the folding can now produce.

Differential Revision: https://reviews.llvm.org/D79502
2020-05-07 12:30:04 +02:00
Nicolas Vasilache
7a80139059 [mlir][Vector] Provide progressive lowering of masked n-D vector transfers
This revision allows masked vector transfers with m-D buffers and n-D vectors to
progressively lower to m-D buffer and 1-D vector transfers.

For a vector.transfer_read, assuming a `memref<(leading_dims) x (major_dims) x (minor_dims) x type>` and a `vector<(minor_dims) x type>` are involved in the transfer, this generates pseudo-IR resembling:
```
     if (any_of(%ivs_major + %offsets, <, major_dims)) {
       %v = vector_transfer_read(
         {%offsets_leading, %ivs_major + %offsets_major, %offsets_minor},
          %ivs_minor):
         memref<(leading_dims) x (major_dims) x (minor_dims) x type>,
         vector<(minor_dims) x type>;
     } else {
       %v = splat(vector<(minor_dims) x type>, %fill)
     }
```

Differential Revision: https://reviews.llvm.org/D79062
2020-04-29 21:28:27 -04:00
Jeremy Bruestle
9f3ab92ec8 [MLIR] Improve support for 0-dimensional Affine Maps.
Summary:
Modified AffineMap::get to remove support for the overload which allowed
an ArrayRef of AffineExpr but no context (and gathered the context from a
presumed first entry, resulting in bugs when there were 0 results).

Instead, we support only a ArrayRef and a context, and a version which
takes a single AffineExpr.

Additionally, removed some now needless case logic which previously
special cased which call to AffineMap::get to use.

Reviewers: flaub, bondhugula, rriddle!, nicolasvasilache, ftynse, ulysseB, mravishankar, antiagainst, aartbik

Subscribers: mehdi_amini, jpienaar, burmako, shauheen, antiagainst, arpith-jacob, mgester, lucyrfox, liufengdb, Joonsoo, bader, grosul1, frgossen, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78226
2020-04-15 14:15:02 -07:00
River Riddle
d3588d0814 [mlir][NFC] Replace mlir/Support/Functional.h with llvm equivalents.
Summary: Functional.h contains many different methods that have a direct, and more efficient, equivalent in LLVM. This revision replaces all usages with the LLVM equivalent, and removes the header. This is part of larger cleanup, pr45513, merging MLIR support facilities into LLVM.

Differential Revision: https://reviews.llvm.org/D78053
2020-04-13 14:22:12 -07:00
Uday Bondhugula
5e8093134a [MLIR] Add method to drop duplicate result exprs from AffineMap
Add a method that given an affine map returns another with just its unique
results. Use this to drop redundant bounds in max/min for affine.for. Update
affine.for's canonicalization pattern and createCanonicalizedForOp to use
this.

Differential Revision: https://reviews.llvm.org/D77237
2020-04-02 03:00:19 +05:30
Uday Bondhugula
ad4b4acbb0 [MLIR][NFC] drop some unnecessary includes
Drop unnecessary includes

Differential Revision: https://reviews.llvm.org/D76898
2020-03-27 09:17:27 +05:30
Ahmed Taei
08a9147349 [mlir][LLVMIR] Fix fusion for rank-0 tensors
Summary: This diff fixes fusion craching for ops with rank-0 tensors

Reviewers: mravishankar, nicolasvasilache, rriddle!

Subscribers: mehdi_amini, rriddle, jpienaar, burmako, shauheen, antiagainst, arpith-jacob, mgester, lucyrfox, liufengdb, Joonsoo, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D76479
2020-03-20 13:17:19 -07:00
Nicolas Vasilache
47ec8702cb [mlir][Linalg] Revisit 0-D abstraction
This revision takes advantage of the empty AffineMap to specify the
0-D edge case. This allows removing a bunch of annoying corner cases
that ended up impacting users of Linalg.

Differential Revision: https://reviews.llvm.org/D75831
2020-03-10 15:14:09 -04:00
MaheshRavishankar
a8355b5c0f [mlir][Linalg] Allow specifiying zero-rank shaped type operands to linalg.generic ops.
Fixing a bug where using a zero-rank shaped type operand to
linalg.generic ops hit an unrelated assert. This also meant that
lowering the operation to loops was not supported. Adding roundtrip
tests and lowering to loops test for zero-rank shaped type operand
with fixes to make the test pass.

Differential Revision: https://reviews.llvm.org/D74638
2020-02-18 13:23:28 -08:00
Benjamin Kramer
564a9de28e Hide implementation details. NFC> 2020-02-17 17:55:23 +01:00
Nicolas Vasilache
8513ff05c8 [mlir][VectorOps][EDSC] Add EDSC for VectorOps
Summary:
This revision adds EDSC support for VectorOps to enable the creation of a `vector_matmul` declaratively. The `vector_matmul` is a simple configuration
 of the `vector.contract` op that follows the StructuredOps abstraction.

Differential Revision: https://reviews.llvm.org/D74284
2020-02-10 15:01:14 -05:00
Frank Laub
a248fa90a7 [MLIR][Affine] NFC: Move AffineValueMap and MutableAffineMap
Summary:
The `AffineValueMap` is moved into `Dialect/AffineOps` to prevent a cyclic
dependency between `Analysis` and `Dialect/AffineOps`.

Reviewers: bondhugula, herhut, nicolasvasilache, rriddle, mehdi_amini

Reviewed By: rriddle, mehdi_amini

Subscribers: mgorny, mehdi_amini, rriddle, jpienaar, burmako, shauheen, antiagainst, arpith-jacob, mgester, lucyrfox, aartbik, liufengdb, Joonsoo, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74277
2020-02-10 02:26:27 -08:00
Mehdi Amini
308571074c Mass update the MLIR license header to mention "Part of the LLVM project"
This is an artifact from merging MLIR into LLVM, the file headers are
now aligned with the rest of the project.
2020-01-26 03:58:30 +00:00
Mehdi Amini
56222a0694 Adjust License.txt file to use the LLVM license
PiperOrigin-RevId: 286906740
2019-12-23 15:33:37 -08:00
River Riddle
4562e389a4 NFC: Remove unnecessary 'llvm::' prefix from uses of llvm symbols declared in mlir namespace.
Aside from being cleaner, this also makes the codebase more consistent.

PiperOrigin-RevId: 286206974
2019-12-18 09:29:20 -08:00
Jose Ignacio Gomez
f60bbb6c3b [Linalg] Add permutation information to tiling
This patch closes issue tensorflow/mlir#271.
It adds an optional permutation map to declarative tiling transformations.
The map is expressed as a list of integers.

Closes tensorflow/mlir#288

COPYBARA_INTEGRATE_REVIEW=https://github.com/tensorflow/mlir/pull/288 from tetuante:issue271 2df2938d6a1f01b3bc404ded08dea2dd1e10b588
PiperOrigin-RevId: 284064151
2019-12-05 15:14:59 -08:00
Diego Caballero
9e6cf0d025 Fix build of affine load/store with empty map
tensorflow/mlir#58 fixed and exercised
verification of load/store ops using empty affine maps. Unfortunately,
it didn't exercise the creation of them. This PR addresses that aspect.
It removes the assumption of AffineMap having at least one result and
stores a pointer to MLIRContext as member of AffineMap.

* Add empty map support to affine.store + test
* Move MLIRContext to AffineMapStorage

Closes tensorflow/mlir#74

PiperOrigin-RevId: 264416260
2019-08-20 10:44:18 -07:00
Nicolas Vasilache
600c47e77b Add a generic Linalg op
This CL introduces a linalg.generic op to represent generic tensor contraction operations on views.

A linalg.generic operation requires a numbers of attributes that are sufficient to emit the computation in scalar form as well as compute the appropriate subviews to enable tiling and fusion.

These attributes are very similar to the attributes for existing operations such as linalg.matmul etc and existing operations can be implemented with the generic form.

In the future, most existing operations can be implemented using the generic form.

This CL starts by splitting out most of the functionality of the linalg::NInputsAndOutputs trait into a ViewTrait that queries the per-instance properties of the op. This allows using the attribute informations.

This exposes an ordering of verifiers issue where ViewTrait::verify uses attributes but the verifiers for those attributes have not been run. The desired behavior would be for the verifiers of the attributes specified in the builder to execute first but it is not the case atm. As a consequence, to emit proper error messages and avoid crashing, some of the
linalg.generic methods are defensive as such:
```
    unsigned getNumInputs() {
      // This is redundant with the `n_views` attribute verifier but ordering of verifiers
      // may exhibit cases where we crash instead of emitting an error message.
      if (!getAttr("n_views") || n_views().getValue().size() != 2)
        return 0;
```

In pretty-printed form, the specific attributes required for linalg.generic are factored out in an independent dictionary named "_". When parsing its content is flattened and the "_name" is dropped. This allows using aliasing for reducing boilerplate at each linalg.generic invocation while benefiting from the Tablegen'd verifier form for each named attribute in the dictionary.

For instance, implementing linalg.matmul in terms of linalg.generic resembles:

```
func @mac(%a: f32, %b: f32, %c: f32) -> f32 {
  %d = mulf %a, %b: f32
  %e = addf %c, %d: f32
  return %e: f32
}
#matmul_accesses = [
  (m, n, k) -> (m, k),
  (m, n, k) -> (k, n),
  (m, n, k) -> (m, n)
]
#matmul_trait = {
  doc = "C(m, n) += A(m, k) * B(k, n)",
  fun = @mac,
  indexing_maps = #matmul_accesses,
  library_call = "linalg_matmul",
  n_views = [2, 1],
  n_loop_types = [2, 1, 0]
}
```

And can be used in multiple places as:
```
  linalg.generic #matmul_trait %A, %B, %C [other-attributes] :
    !linalg.view<?x?xf32>, !linalg.view<?x?xf32>, !linalg.view<?x?xf32>
```

In the future it would be great to have a mechanism to alias / register a new
linalg.op as a pair of linalg.generic, #trait.

Also, note that with one could theoretically only specify the `doc` string and parse all the attributes from it.

PiperOrigin-RevId: 261338740
2019-08-02 09:53:41 -07:00
Nicolas Vasilache
28fb743798 More general subview calculation in tiling
This CL refactors tiling to enable tiling of views that are not just specified by a simple permutation. This allows the tiling of convolutions for which a new example is added.

PiperOrigin-RevId: 256346028
2019-07-03 14:36:42 -07:00
Nicolas Vasilache
4a1df48f44 Add a Linalg convolution op.
This CL adds a conv op that corresponds to the TF description along with its lowering to loops (https://www.tensorflow.org/api_docs/python/tf/nn/convolution).

The dimension of the convolution is inferred from the rank of the views. The other logical
dimensions correspond to the TF description.

The computation of tiled views need to be updated to work for the input tensor. This is left for a future CL.

PiperOrigin-RevId: 254505644
2019-06-22 09:18:06 -07:00
Nicolas Vasilache
235e2fe030 Support for 0-D case in Linalg ops
This CL adds support for O-D ops in Linalg ops by:
1. making the CopyOp maps optional instead of default valued
2. allowing certain map operations to accept and return empty maps
3. making linalg::LowerToLoops aware of these changes
4. providing a proper 0-D impl for CopyOp and FillOp
5. adding the relevant tests

PiperOrigin-RevId: 254381908
2019-06-22 09:15:36 -07:00
Nicolas Vasilache
e7e03cee1f Add Linalg CopyOp
This CL adds a generic CopyOp to Linalg and its lowering to loops.
The CopyOp supports input and output permutation maps.
When combined with tiling and allocating a new local buffer, this should provide basic support for implementing simple memory transfers with coalescing.

At the moment, lowering copies to a library call is not supported.

PiperOrigin-RevId: 253250497
2019-06-19 23:02:31 -07:00
MLIR Team
5a91b9896c Remove "size" property of affine maps.
--

PiperOrigin-RevId: 250572818
2019-06-01 20:09:02 -07:00
Mehdi Amini
ff5d021c39 Add llvm_unreachable in unreachable path to silence GCC warning (NFC)
The switch is supposed to be fully covered, but GCC warns that:
     "control reaches end of non-void function"

--

PiperOrigin-RevId: 247672430
2019-05-10 19:30:06 -07:00
Nicolas Vasilache
21d9dc4f29 [Linalg] Add a primitive tiling pass
This CL adds a primitive tiling pass for Linalg.
    The tiling pass uses the loopToOperandRangesMaps property which should be ideally Tablegen'd and in-class.

    The tiling specification uses 0 as a convention to skip loops that should not be tiled.

    Tiling proceeds in 3 steps, for each op:
    1. Pad tile sizes with 0 to match the number of loops, this simplifies the implementation and avoids affine map manipulations to align dimensions.
    2. Create loop ranges that represent the min/max/step by which to iterate. This should be later complemented by a range intersection to avoid the out-of-bounds case.
    3. Map the loop ranges to view ranges in order to create subviews on which the op can be called.

    Relevant utility and helper functions are added separately that support writing the transformation in a declarative fashion.
    Simplifying assumptions are made for now on the views and the ranges that are constructed
    in the function and are not passed as function arguments. This restriction will be lifted
    in the future.

--

PiperOrigin-RevId: 246124419
2019-05-06 08:23:43 -07:00
River Riddle
e472f5b3d9 Optimize the implementation of AffineExprConstantFolder to avoid the redundant creation of IntegerAttrs and IndexType. This becomes a much bigger performance issue when MLIRContext is thread-safe; as each unnecessary call may need to lock a mutex.
PiperOrigin-RevId: 238484632
2019-03-29 17:18:22 -07:00
River Riddle
5e1f1d2cab Update the constantFold/fold API to use LogicalResult instead of bool.
PiperOrigin-RevId: 237719658
2019-03-29 17:10:50 -07:00
River Riddle
4755774d16 Make IndexType a standard type instead of a builtin. This also cleans up some unnecessary factory methods on the Type class.
PiperOrigin-RevId: 233640730
2019-03-29 16:25:38 -07:00
River Riddle
10237de8eb Refactor the affine analysis by moving some functionality to IR and some to AffineOps. This is important for allowing the affine dialect to define canonicalizations directly on the operations instead of relying on transformation passes, e.g. ComposeAffineMaps. A summary of the refactoring:
* AffineStructures has moved to IR.

* simplifyAffineExpr/simplifyAffineMap/getFlattenedAffineExpr have moved to IR.

* makeComposedAffineApply/fullyComposeAffineMapAndOperands have moved to AffineOps.

* ComposeAffineMaps is replaced by AffineApplyOp::canonicalize and deleted.

PiperOrigin-RevId: 232586468
2019-03-29 16:15:41 -07:00
Nicolas Vasilache
362557e11c Simplify compositions of AffineApply
This CL is the 6th and last on the path to simplifying AffineMap composition.
This removes `AffineValueMap::forwardSubstitutions` and replaces it by simple
calls to `fullyComposeAffineMapAndOperands`.

PiperOrigin-RevId: 228962580
2019-03-29 15:11:56 -07:00
Nicolas Vasilache
c6f798a976 Introduce AffineMap::compose(AffineMap)
This CL is the 2nd on the path to simplifying AffineMap composition.
This CL uses the now accepted `AffineExpr::compose(AffineMap)` to
implement `AffineMap::compose(AffineMap)`.

Implications of keeping the simplification function in
Analysis are documented where relevant.

PiperOrigin-RevId: 228276646
2019-03-29 15:04:20 -07:00
Chris Lattner
7983bbc251 Introduce a simple canonicalization of affine_apply that drops unused dims and
symbols.

Included with this is some other infra:
 - Testcases for other canonicalizations that I will implement next.
 - Some helpers in AffineMap/Expr for doing simple walks without defining whole
   visitor classes.
 - A 'replaceDimsAndSymbols' facility that I'll be using to simplify maps and
   exprs, e.g. to fold one constant into a mapping and to drop/renumber unused dims.
 - Allow index (and everything else) to work in memref's, as we previously
   discussed, to make the testcase easier to write.
 - A "getAffineBinaryExpr" helper to produce a binop when you know the kind as
   an enum.

This line of work will eventually subsume the ComposeAffineApply pass, but it is no where close to that yet :-)

PiperOrigin-RevId: 227852951
2019-03-29 14:56:07 -07:00
Jacques Pienaar
711047c0cd Add Type to int/float attributes.
* Optionally attach the type of integer and floating point attributes to the attributes, this allows restricting a int/float to specific width.
  - Currently this allows suffixing int/float constant with type [this might be revised in future].
  - Default to i64 and f32 if not specified.
* For index types the APInt width used is 64.
* Change callers to request a specific attribute type.
* Store iN type with APInt of width N.
* This change does not handle the folding of constants of different types (e.g., doing int type promotions to support constant folding i3 and i32), and instead restricts the constant folding to only operate on the same types.

PiperOrigin-RevId: 221722699
2019-03-29 13:59:23 -07:00
Jacques Pienaar
25e6b541cd Switch IntegerAttr to use APInt.
Change the storage type to APInt from int64_t for IntegerAttr (following the change to APFloat storage in FloatAttr). Effectively a direct change from int64_t to 64-bit APInt throughout (the bitwidth hardcoded). This change also adds a getInt convenience method to IntegerAttr and replaces previous getValue calls with getInt calls.

While this changes updates the storage type, it does not update all constant folding calls.

PiperOrigin-RevId: 221082788
2019-03-29 13:55:08 -07:00
MLIR Team
f28e4df666 Adds a dependence check to test whether two accesses to the same memref access the same element.
- Builds access functions and iterations domains for each access.
- Builds dependence polyhedron constraint system which has equality constraints for equated access functions and inequality constraints for iteration domain loop bounds.
- Runs elimination on the dependence polyhedron to test if no dependence exists between the accesses.
- Adds a trivial LoopFusion transformation pass with a simple test policy to test dependence between accesses to the same memref in adjacent loops.
- The LoopFusion pass will be extended in subsequent CLs.

PiperOrigin-RevId: 219630898
2019-03-29 13:47:13 -07:00
River Riddle
792d1c25e4 Implement value type abstraction for attributes.
This is done by changing Attribute to be a POD interface around an underlying pointer storage and adding in-class support for isa/dyn_cast/cast.

PiperOrigin-RevId: 218764173
2019-03-29 13:39:19 -07:00
Uday Bondhugula
80610c2f49 Introduce Fourier-Motzkin variable elimination + other cleanup/support
- Introduce Fourier-Motzkin variable elimination to eliminate a dimension from
  a system of linear equalities/inequalities. Update isEmpty to use this.
  Since FM is only exact on rational/real spaces, an emptiness check based on
  this is guaranteed to be exact whenever it says the underlying set is empty;
  if it says, it's not empty, there may still be no integer points in it.
  Also, supports a version that computes "dark shadows".

- Test this by checking for "always false" conditionals in if statements.

- Unique IntegerSet's that are small (few constraints, few variables). This
  basically means the canonical empty set and other small sets that are
  likely commonly used get uniqued; allows checking for the canonical empty set
  by pointer. IntegerSet::kUniquingThreshold gives the threshold constraint size
  for uniqui'ing.

- rename simplify-affine-expr -> simplify-affine-structures

Other cleanup

- IntegerSet::numConstraints, AffineMap::numResults are no longer needed;
  remove them.
- add copy assignment operators for AffineMap, IntegerSet.
- rename Invalid() -> Null() on AffineExpr, AffineMap, IntegerSet
- Misc cleanup for FlatAffineConstraints API

PiperOrigin-RevId: 218690456
2019-03-29 13:38:24 -07:00
Chris Lattner
50cc57e25a Random cleanups:
- Change AllocOp to have a getType() that always returns a MemRefType, since
   that is what it requires.
 - Rename StandardOps/StandardOpRegistration.cpp ->
   StandardOps/OpRegistration.cpp to align with other op sets.
 - Add AffineMap::getContext() helper and use it in the asmprinter.

PiperOrigin-RevId: 218205527
2019-03-29 13:35:19 -07:00
Nicolas Vasilache
1d3e7e2616 [MLIR] AffineMap value type
This CL applies the same pattern as AffineExpr to AffineMap: a simple struct
that acts as the storage is allocated in the bump pointer. The AffineMap is
immutable and accessed everywhere by value.

PiperOrigin-RevId: 216445930
2019-03-29 13:26:24 -07:00
Nicolas Vasilache
8ebb6ff171 [MLIR] Sketch AffineExpr value type
This CL sketches what it takes for AffineExpr to fully have by-value semantics
and not be a not-so-smart pointer anymore.

This essentially makes the underyling class a simple storage struct and
implements the operations on the value type directly. Since there is no
forwarding of operations anymore, we can full isolate the storage class and
make a hard visibility barrier by moving detail::AffineExpr into
AffineExprDetail.h.

AffineExprDetail.h is only included where storage-related information is
needed.

PiperOrigin-RevId: 216385459
2019-03-29 13:25:42 -07:00
Nicolas Vasilache
6707c7bea1 [MLIR] AffineExpr final cleanups
This CL:
1. performs the global codemod AffineXExpr->AffineXExprClass and
AffineXExprRef -> AffineXExpr;
2. simplifies function calls by removing the redundant MLIRContext parameter;
3. adds missing binary operator versions of scalar op AffineExpr where it
makes sense.

PiperOrigin-RevId: 216242674
2019-03-29 13:25:14 -07:00
Nicolas Vasilache
ce2edea135 [MLIR] Cleanup AffineExpr
This CL introduces a series of cleanups for AffineExpr value types:
1. to make it clear that the value types should be used, the pointer
AffineExpr types are put in the detail namespace. Unfortunately, since the
value type operator-> only forwards to the underlying pointer type, we
still
need to expose this in the include file for now;
2. AffineExprKind is ok to use, it thus comes out of detail and thus of
AffineExpr
3. getAffineDimExpr, getAffineSymbolExpr, getAffineConstantExpr are
similarly
extracted as free functions and their naming is mande consistent across
Builder, MLContext and AffineExpr
4. AffineBinaryOpEx::simplify functions are made into static free
functions.
In particular it is moved away from AffineMap.cpp where it does not belong
5. operator AffineExprType is made explicit
6. uses the binary operators everywhere possible
7. drops the pointer usage everywhere outside of AffineExpr.cpp,
MLIRContext.cpp and AsmPrinter.cpp

PiperOrigin-RevId: 216207212
2019-03-29 13:24:45 -07:00
Nicolas Vasilache
4911978f7e [MLIR] Value types for AffineXXXExpr
This CL makes AffineExprRef into a value type.

Notably:
1. drops llvm isa, cast, dyn_cast on pointer type and uses member functions on
the value type. It may be possible to still use classof  (in a followup CL)
2. AffineBaseExprRef aggressively casts constness away: if we mean the type is
immutable then let's jump in with both feet;
3. Drop implicit casts to the underlying pointer type because that always
results in surprising behavior and is not needed in practice once enough
cleanup has been applied.

The remaining negative I see is that we still need to mix operator. and
operator->. There is an ugly solution that forwards the methods but that ends
up duplicating the class hierarchy which I tried to avoid as much as
possible. But maybe it's not that bad anymore since AffineExpr.h would still
contain a single class hierarchy (the duplication would be impl detail in.cpp)

PiperOrigin-RevId: 216188003
2019-03-29 13:24:31 -07:00
Uday Bondhugula
d18ae9e2c7 Constant folding for loop bounds.
- Fold the lower/upper bound of a loop to a constant whenever the result of the
  application of the bound's affine map on the operand list yields a constant.

- Update/complete 'for' stmt's API to set lower/upper bounds with operands.
  Resolve TODOs for ForStmt::set{Lower,Upper}Bound.

- Moved AffineExprConstantFolder into AffineMap.cpp and added
  AffineMap::constantFold to be used by both AffineApplyOp and
  ForStmt::constantFoldBound.

PiperOrigin-RevId: 215997346
2019-03-29 13:24:01 -07:00
Nicolas Vasilache
b55b407601 [RFC][MLIR] Use AffineExprRef in place of AffineExpr* in IR
This CL starts by replacing AffineExpr* with value-type AffineExprRef in a few
places in the IR. By a domino effect that is pretty telling of the
inconsistencies in the codebase, const is removed where it makes sense.

The rationale is that the decision was concisously made that unique'd types
have pointer semantics without const specifier. This is fine but we should be
consistent. In the end, the only logical invariant is that there should never
be such a thing as a const AffineExpr*, const AffineMap* or const IntegerSet*
in our codebase.

This CL takes a number of shortcuts to killing const with fire, in particular
forcing const AffineExprRef to return the underlying non-const
AffineExpr*. This will be removed once AffineExpr* has disappeared in
containers but for now such shortcuts allow a bit of sanity in this long quest
for cleanups.

The **only** places where const AffineExpr*, const AffineMap* or const
IntegerSet* may still appear is by transitive needs from containers,
comparison operators etc.

There is still one major thing remaining here: figure out why cast/dyn_cast
return me a const AffineXXX*, which in turn requires a bunch of ugly
const_casts. I suspect this is due to the classof
taking const AffineXXXExpr*. I wonder whether this is a side effect of 1., if
it is coming from llvm itself (I'd doubt it) or something else (clattner@?)

In light of this, the whole discussion about const makes total sense to me now
and I would systematically apply the rule that in the end, we should never
have any const XXX in our codebase for unique'd types (assuming we can remove
them all in containers and no additional constness constraint is added on us
from the outside world).

PiperOrigin-RevId: 215811554
2019-03-29 13:23:05 -07:00