165 Commits

Author SHA1 Message Date
Uday Bondhugula
f94b15c247 Update dma-generate: update for multiple load/store op's per memref
- introduce a way to compute union using symbolic rectangular bounding boxes
- handle multiple load/store op's to the same memref by taking a union of the regions
- command-line argument to provide capacity of the fast memory space
- minor change to replaceAllMemRefUsesWith to not generate affine_apply if the
  supplied index remap was identity

PiperOrigin-RevId: 230848185
2019-03-29 15:35:38 -07:00
Uday Bondhugula
864d9e02a1 Update fusion cost model + some additional infrastructure and debug information for -loop-fusion
- update fusion cost model to fuse while tolerating a certain amount of redundant
  computation; add cl option -fusion-compute-tolerance
  evaluate memory footprint and intermediate memory reduction
- emit debug info from -loop-fusion showing what was fused and why
- introduce function to compute memory footprint for a loop nest
- getMemRefRegion readability update - NFC

PiperOrigin-RevId: 230541857
2019-03-29 15:32:06 -07:00
Uday Bondhugula
94a03f864f Allocate private/local buffers for slices accurately during fusion
- the size of the private memref created for the slice should be based on
  the memref region accessed at the depth at which the slice is being
  materialized, i.e., symbolic in the outer IVs up until that depth, as opposed
  to the region accessed based on the entire domain.

- leads to a significant contraction of the temporary / intermediate memref
  whenever the memref isn't reduced to a single scalar (through store fwd'ing).

Other changes

- update to promoteIfSingleIteration - avoid introducing unnecessary identity
  map affine_apply from IV; makes it much easier to write and read test cases
  and pass output for all passes that use promoteIfSingleIteration; loop-fusion
  test cases become much simpler

- fix replaceAllMemrefUsesWith bug that was exposed by the above update -
  'domInstFilter' could be one of the ops erased due to a memref replacement in
  it.

- fix getConstantBoundOnDimSize bug: a division by the coefficient of the identifier was
  missing (the latter need not always be 1); add lbFloorDivisors output argument

- rename getBoundingConstantSizeAndShape -> getConstantBoundingSizeAndShape

PiperOrigin-RevId: 230405218
2019-03-29 15:30:31 -07:00
Uday Bondhugula
d2aaa175ca Fix FlatAffineConstraints::removeIdRange
- the number of symbols/local ids was being incorrectly updated; the code in
  cl/230112574 exposes this.

PiperOrigin-RevId: 230358327
2019-03-29 15:29:44 -07:00
MLIR Team
27d067e164 LoopFusion improvements:
*) Adds support for fusing into consumer loop nests with multiple loads from the same memref.
*) Adds support for reducing slice loop trip count by projecting out destination loop IVs greater than destination loop depth.
*) Removes dependence on src loop depth and simplifies cost model computation.

PiperOrigin-RevId: 229575126
2019-03-29 15:21:59 -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
Uday Bondhugula
2370c601ba Add safeguard against FM explosion
- FM has a worst case exponential complexity. For our purposes, this worst case
  is rarely expected, but could still appear due to improperly constructed
  constraints (a logical/memory error in other methods for eg.) or artificially
  created arbitrarily complex integer sets (adversarial / fuzz tests).

  Add a check to detect such an explosion in the number of constraints and
  conservatively return false from isEmpty() (instead of running out of memory
  or running for too long).

- Add an artifical virus test case.

PiperOrigin-RevId: 228753496
2019-03-29 15:07:55 -07:00
Uday Bondhugula
303c09299f Fix affine expr flattener bug + improve simplification in a particular scenario
- fix visitDivExpr: constraints constructed for localVarCst used the original
  divisor instead of the simplified divisor; fix this. Add a simple test case
  in memref-bound-check that reproduces this bug - although this was encountered in the
  context of slicing for fusion.

- improve mod expr flattening: when flattening mod expressions,
  cancel out the GCD of the numerator and denominator so that we can get a
  simpler flattened form along with a simpler floordiv local var for it

PiperOrigin-RevId: 228539928
2019-03-29 15:06:11 -07:00
Uday Bondhugula
21baf86a2f Extend loop-fusion's slicing utility + other fixes / updates
- refactor toAffineFromEq and the code surrounding it; refactor code into
  FlatAffineConstraints::getSliceBounds
- add FlatAffineConstraints methods to detect identifiers as mod's and div's of other
  identifiers
- add FlatAffineConstraints::getConstantLower/UpperBound
- Address b/122118218 (don't assert on invalid fusion depths cmdline flags -
  instead, don't do anything; change cmdline flags
  src-loop-depth -> fusion-src-loop-depth
- AffineExpr/Map print method update: don't fail on null instances (since we have
  a wrapper around a pointer, it's avoidable); rationale: dump/print methods should
  never fail if possible.
- Update memref-dataflow-opt to add an optimization to avoid a unnecessary call to
  IsRangeOneToOne when it's trivially going to be true.
- Add additional test cases to exercise the new support
- update a few existing test cases since the maps are now generated uniformly with
  all destination loop operands appearing for the backward slice
- Fix projectOut - fix wrong range for getBestElimCandidate.
- Fix for getConstantBoundOnDimSize() - didn't show up in any test cases since
  we didn't have any non-hyperrectangular ones.

PiperOrigin-RevId: 228265152
2019-03-29 15:03:20 -07:00
Uday Bondhugula
56b3640b94 Misc readability and doc / code comment related improvements - NFC
- when SSAValue/MLValue existed, code at several places was forced to create additional
  aggregate temporaries of SmallVector<SSAValue/MLValue> to handle the conversion; get
  rid of such redundant code

- use filling ctors instead of explicit loops

- for smallvectors, change insert(list.end(), ...) -> append(...

- improve comments at various places

- turn getMemRefAccess into MemRefAccess ctor and drop duplicated
  getMemRefAccess. In the next CL, provide getAccess() accessors for load,
  store, DMA op's to return a MemRefAccess.

PiperOrigin-RevId: 228243638
2019-03-29 15:02:41 -07:00
Uday Bondhugula
8496f2c30b Complete TODOs / cleanup for loop-fusion utility
- this is CL 1/2 that does a clean up and gets rid of one limitation in an
  underlying method - as a result, fusion works for more cases.
- fix bugs/incomplete impl. in toAffineMapFromEq
- fusing across rank changing reshapes for example now just works

  For eg. given a rank 1 memref to rank 2 memref reshape (64 -> 8 x 8) like this,
  -loop-fusion -memref-dataflow-opt now completely fuses and inlines/store-forward
  to get rid of the temporary:

INPUT

  // Rank 1 -> Rank 2 reshape
  for %i0 = 0 to 64 {
     %v = load %A[%i0]
     store %v, %B[%i0 floordiv 8, i0 mod 8]
  }

  for %i1 = 0 to 8
    for %i2 = 0 to 8
      %w = load %B[%i1, i2]
      "foo"(%w) : (f32) -> ()

OUTPUT

$ mlir-opt -loop-fusion -memref-dataflow-opt fuse_reshape.mlir

#map0 = (d0, d1) -> (d0 * 8 + d1)
mlfunc @fuse_reshape(%arg0: memref<64xf32>) {
  for %i0 = 0 to 8 {
    for %i1 = 0 to 8 {
      %0 = affine_apply #map0(%i0, %i1)
      %1 = load %arg0[%0] : memref<64xf32>
      "foo"(%1) : (f32) -> ()
    }
  }
}

AFAIK, there is no polyhedral tool / compiler that can perform such fusion -
because it's not really standard loop fusion, but possible through a
generalized slicing-based approach such as ours.

PiperOrigin-RevId: 227918338
2019-03-29 14:57:22 -07:00
Nicolas Vasilache
17f96ea3dd [MLIR] Fix uninitialized value found with msan
The omission of an early exit created opportunities for unitialized memory
reads. This CL fixes the issue.

PiperOrigin-RevId: 227761814
2019-03-29 14:54:36 -07:00
Uday Bondhugula
b9fe6be6d4 Introduce memref store to load forwarding - a simple memref dataflow analysis
- the load/store forwarding relies on memref dependence routines as well as
  SSA/dominance to identify the memref store instance uniquely supplying a value
  to a memref load, and replaces the result of that load with the value being
  stored. The memref is also deleted when possible if only stores remain.

- add methods for post dominance for MLFunction blocks.

- remove duplicated getLoopDepth/getNestingDepth - move getNestingDepth,
  getMemRefAccess, getNumCommonSurroundingLoops into Analysis/Utils (were
  earlier static)

- add a helper method in FlatAffineConstraints - isRangeOneToOne.

PiperOrigin-RevId: 227252907
2019-03-29 14:47:28 -07:00
Uday Bondhugula
6e3462d251 Fix b/122139732; update FlatAffineConstraints::isEmpty() to eliminate IDs in a
better order.

- update isEmpty() to eliminate IDs in a better order. Speed improvement for
  complex cases (for eg. high-d reshape's involving mod's/div's).
- minor efficiency update to projectOut (was earlier making an extra albeit
  benign call to gaussianEliminateIds) (NFC).
- move getBestIdToEliminate further up in the file (NFC).
- add the failing test case.
- add debug info to checkMemRefAccessDependence.

PiperOrigin-RevId: 227244634
2019-03-29 14:47:13 -07:00
Chris Lattner
456ad6a8e0 Standardize naming of statements -> instructions, revisting the code base to be
consistent and moving the using declarations over.  Hopefully this is the last
truly massive patch in this refactoring.

This is step 21/n towards merging instructions and statements, NFC.

PiperOrigin-RevId: 227178245
2019-03-29 14:44:30 -07:00
Uday Bondhugula
b1d9cc4d1e Extend/complete dependence tester to utilize local var info.
- extend/complete dependence tester to utilize local var info while adding
  access function equality constraints; one more step closer to get slicing
  based fusion working in the general case of affine_apply's involving mod's/div's.
- update test case to reflect more accurate dependence information; remove
  inaccurate comment on test case mod_deps.
- fix a minor "bug" in equality addition in addMemRefAccessConstraints (doesn't
  affect correctness, but the fixed version is more intuitive).
- some more surrounding code clean up
- move simplifyAffineExpr out of anonymous AffineExprFlattener class - the
  latter has state, and the former should reside outside.

PiperOrigin-RevId: 227175600
2019-03-29 14:44:14 -07:00
Chris Lattner
5187cfcf03 Merge Operation into OperationInst and standardize nomenclature around
OperationInst.  This is a big mechanical patch.

This is step 16/n towards merging instructions and statements, NFC.

PiperOrigin-RevId: 227093712
2019-03-29 14:42:23 -07:00
Chris Lattner
3f190312f8 Merge SSAValue, CFGValue, and MLValue together into a single Value class, which
is the new base of the SSA value hierarchy.  This CL also standardizes all the
nomenclature and comments to use 'Value' where appropriate.  This also eliminates a large number of cast<MLValue>(x)'s, which is very soothing.

This is step 11/n towards merging instructions and statements, NFC.

PiperOrigin-RevId: 227064624
2019-03-29 14:40:06 -07:00
Uday Bondhugula
14d2618f63 Simplify memref-dependence-check's meta data structures / drop duplication and
reuse existing ones.

- drop IterationDomainContext, redundant since FlatAffineConstraints has
  MLValue information associated with its dimensions.
- refactor to use existing support
- leads to a reduction in LOC
- as a result of these changes, non-constant loop bounds get naturally
  supported for dep analysis.
- update test cases to include a couple with non-constant loop bounds
- rename addBoundsFromForStmt -> addForStmtDomain
- complete TODO for getLoopIVs (handle 'if' statements)

PiperOrigin-RevId: 226082008
2019-03-29 14:32:46 -07:00
Uday Bondhugula
1d72f2e47e Update / complete a TODO for addBoundsForForStmt
- when adding constraints from a 'for' stmt into FlatAffineConstraints,
  correctly add bound operands of the 'for' stmt as a dimensional identifier or
  a symbolic identifier depending on whether the bound operand is a valid
  MLFunction symbol
- update test case to exercise this.

PiperOrigin-RevId: 225988511
2019-03-29 14:32:31 -07:00
Uday Bondhugula
20531932f4 Refactor/update memref-dep-check's addMemRefAccessConstraints and
addDomainConstraints; add support for mod/div for dependence testing.

- add support for mod/div expressions in dependence analysis
- refactor addMemRefAccessConstraints to use getFlattenedAffineExprs (instead
  of getFlattenedAffineExpr); update addDomainConstraints.
- rename AffineExprFlattener::cst -> localVarCst

PiperOrigin-RevId: 225933306
2019-03-29 14:31:58 -07:00
MLIR Team
3b69230b3a Loop Fusion pass update: introduce utilities to perform generalized loop fusion based on slicing; encompasses standard loop fusion.
*) Adds simple greedy fusion algorithm to drive experimentation. This algorithm greedily fuses loop nests with single-writer/single-reader memref dependences to improve locality.
*) Adds support for fusing slices of a loop nest computation: fusing one loop nest into another by adjusting the source loop nest's iteration bounds (after it is fused into the destination loop nest). This is accomplished by solving for the source loop nest's IVs in terms of the destination loop nests IVs and symbols using the dependece polyhedron, then creating AffineMaps of these functions for the loop bounds of the fused source loop.
*) Adds utility function 'insertMemRefComputationSlice' which computes and inserts computation slice from loop nest surrounding a source memref access into the loop nest surrounding the destingation memref access.
*) Adds FlatAffineConstraints::toAffineMap function which returns and AffineMap which represents an equality contraint where one dimension identifier is represented as a function of all others in the equality constraint.
*) Adds multiple fusion unit tests.

PiperOrigin-RevId: 225842944
2019-03-29 14:30:13 -07:00
Uday Bondhugula
45a0f52519 Expression flattening improvement - reuse local expressions.
- if a local id was already for a specific mod/div expression, just reuse it if
  the expression repeats (instead of adding a new one).
- drastically reduces the number of local variables added during flattening for
  real use cases - since the same div's and mod expressions often repeat.
- add getFlattenedAffineExprs for AffineMap, IntegerSet based on the above

As a natural result of the above:

- FlatAffineConstraints(IntegerSet) ctor now deals with integer sets that have mod
  and div constraints as well, and these get simplified as well from -simplify-affine-structures

PiperOrigin-RevId: 225452174
2019-03-29 14:28:13 -07:00
Uday Bondhugula
8365bdc17f FlatAffineConstraints - complete TODOs: add method to remove duplicate /
trivially redundant constraints. Update projectOut to eliminate identifiers in
a more efficient order. Fix b/120801118.

- add method to remove duplicate / trivially redundant constraints from
  FlatAffineConstraints (use a hashing-based approach with DenseSet)
- update projectOut to eliminate identifiers in a more efficient order

(A sequence of affine_apply's like this (from a real use case) finally exposed
the lack of the above trivial/low hanging simplifications).

  for %ii = 0 to 64 {
    for %jj = 0 to 9 {
      %a0 = affine_apply (d0, d1) -> (d0 * (9 * 1024) + d1 * 128) (%ii, %jj)
      %a1 = affine_apply (d0) ->
        (d0 floordiv (2 * 3 * 3 * 128 * 128),
        (d0 mod 294912) floordiv (3 * 3 * 128 * 128),
        (((d0 mod 294912) mod 147456) floordiv 1152) floordiv 8,
        (((d0 mod 294912) mod 147456) mod 1152) floordiv 384,
        ((((d0 mod 294912) mod 147456) mod 1152) mod 384) floordiv 128,
        (((((d0 mod 294912) mod 147456) mod 1152) mod 384) mod 128)
          floordiv 128) (%a0)
      %v0 = load %in[%a1tensorflow/mlir#0, %a1tensorflow/mlir#1, %a1tensorflow/mlir#3, %a1tensorflow/mlir#4, %a1tensorflow/mlir#2, %a1tensorflow/mlir#5]
        : memref<2x2x3x3x16x1xi32>
    }
  }

- update FlatAffineConstraints::print to print number of constraints.

PiperOrigin-RevId: 225397480
2019-03-29 14:27:29 -07:00
Uday Bondhugula
c86c414765 Remove dead code from FlatAffineConstraints
- getDimensionBounds() was added initially for quick experimentation - no
  longer used (getConstantBoundOnDimSize is the more powerful/complete
  replacement).
- FlatAffineConstraints::getConstantLower/UpperBound are incomplete,
  functionality/naming-wise misleading, and not used currently. Removing these;
  complete/fixed version will be added in an upcoming CL.

PiperOrigin-RevId: 225075061
2019-03-29 14:25:52 -07:00
Uday Bondhugula
6757fb151d FlatAffineConstraints API cleanup; add normalizeConstraintsByGCD().
- add method normalizeConstraintsByGCD
- call normalizeConstraintsByGCD() and GCDTightenInequalities() at the end of
  projectOut.
- remove call to GCDTightenInequalities() from getMemRefRegion
- change isEmpty() to check isEmptyByGCDTest() / hasInvalidConstraint() each
  time an identifier is eliminated (to detect emptiness early).
- make FourierMotzkinEliminate, gaussianEliminateId(s),
  GCDTightenInequalities() private
- improve / update stale comments

PiperOrigin-RevId: 224866741
2019-03-29 14:24:37 -07:00
Uday Bondhugula
dfc752e42b Generate strided DMAs from -dma-generate
- generate DMAs correctly now using strided DMAs where needed
- add support for multi-level/nested strides; op still supports one level of
  stride for now.

Other things
- add test case for  symbolic lower/upper bound; cases where the DMA buffer
  size can't be bounded by a known constant
- add test case for dynamic shapes where the DMA buffers are however bounded by
  constants
- refactor some of the '-dma-generate' code

PiperOrigin-RevId: 224584529
2019-03-29 14:23:19 -07:00
Uday Bondhugula
73fc0223e4 Fix cases where unsigned / signed arithmetic was being mixed (following up on
cl/224246657); eliminate repeated evaluation of exprs in loop upper bounds.

- while on this, sweep through and fix potential repeated evaluation of
  expressions in loop upper bounds

PiperOrigin-RevId: 224268918
2019-03-29 14:19:22 -07:00
Uday Bondhugula
a92130880e Complete multiple unhandled cases for DmaGeneration / getMemRefRegion;
update/improve/clean up API.

- update FlatAffineConstraints::getConstBoundDifference; return constant
  differences between symbolic affine expressions, look at equalities as well.
- fix buffer size computation when generating DMAs symbolic in outer loops,
  correctly handle symbols at various places (affine access maps, loop bounds,
  loop IVs outer to the depth at which DMA generation is being done)
- bug fixes / complete some TODOs for getMemRefRegion
- refactor common code b/w memref dependence check and getMemRefRegion
- FlatAffineConstraints API update; added methods employ trivial checks /
  detection - sufficient to handle hyper-rectangular cases in a precise way
  while being fast / low complexity. Hyper-rectangular cases fall out as
  trivial cases for these methods while other cases still do not cause failure
  (either return conservative or return failure that is handled by the caller).

PiperOrigin-RevId: 224229879
2019-03-29 14:18:22 -07:00
Uday Bondhugula
f9af62998b Remove duplicate FlatAffineConstraints::removeId - refactor to use
removeColumnRange

- remove functionally duplicate code in removeId.

- rename removeColumnRange -> removeIdRange - restrict valid input to just the
  identifier columns (not the constant term column).

PiperOrigin-RevId: 224054064
2019-03-29 14:17:24 -07:00
Uday Bondhugula
7c2347266d FlatAffineConstraints::removeId() fix.
This is an obvious bug, but none of the test cases exposed it since numIds was
correctly updated, and the dimensional identifiers were always eliminated
before the symbolic identifiers in all cases that removeId was getting
called from. However, other work in progress exercises the other scenarios and
exposes this bug.

Add an hasConsistentState() private method to move common assertion checks, and call it
from several base methods. Make hasInvalidConstraint() a private method as
well (from a file static one).

PiperOrigin-RevId: 224032721
2019-03-29 14:17:10 -07:00
MLIR Team
753109547d During forward substitution, merge symbols from input AffineMap with the symbol list of the target AffineMap.
Symbols can be used as dim identifiers and symbolic identifiers, and so we must preserve the symbolic identifies from the input AffineMap during forward substitution, even if that same identifier is used as a dimension identifier in the target AffineMap.
Test case added.

Going forward, we may want to explore solutions where we do not maintain this split between dimensions and symbols, and instead verify the validity of each use of each AffineMap operand AffineMap in the context where the AffineMap operand usage is required to be a symbol: in the denominator of floordiv/ceildiv/mod for semi-affine maps, and in instructions that can capture symbols (i.e. alloc)

PiperOrigin-RevId: 224017364
2019-03-29 14:16:40 -07:00
Uday Bondhugula
89c41fdca1 FlatAffineConstraints::composeMap: return failure instead of asserting on semi-affine maps
FlatAffineConstraints::composeMap: should return false instead of asserting on
a semi-affine map. Make getMemRefRegion just propagate false when encountering
semi-affine maps (instead of crashing!)
PiperOrigin-RevId: 223828743
2019-03-29 14:14:56 -07:00
Uday Bondhugula
2631b155a9 Fix bugs in DMA generation and FlatAffineConstraints; add more test
cases.

- fix bug in calculating index expressions for DMA buffers in certain cases
  (affected tiled loop nests); add more test cases for better coverage.
- introduce an additional optional argument to replaceAllMemRefUsesWith;
  additional operands to the index remap AffineMap can now be supplied by the
  client.
- FlatAffineConstraints::addBoundsForStmt - fix off by one upper bound,
  ::composeMap - fix position bug.
- Some clean up and more comments

PiperOrigin-RevId: 222434628
2019-03-29 14:07:31 -07:00
Uday Bondhugula
fff1efbaf5 Updates to transformation/analysis passes/utilities. Update DMA generation pass
and getMemRefRegion() to work with specified loop depths; add support for
outgoing DMAs, store op's.

- add support for getMemRefRegion symbolic in outer loops - hence support for
  DMAs symbolic in outer surrounding loops.

- add DMA generation support for outgoing DMAs (store op's to lower memory
  space); extend getMemoryRegion to store op's. -memref-bound-check now works
  with store op's as well.

- fix dma-generate (references to the old memref in the dma_start op were also
  being replaced with the new buffer); we need replace all memref uses to work
  only on a subset of the uses - add a new optional argument for
  replaceAllMemRefUsesWith. update replaceAllMemRefUsesWith to take an optional
  'operation' argument to serve as a filter - if provided, only those uses that
  are dominated by the filter are replaced.

- Add missing print for attributes for dma_start, dma_wait op's.

- update the FlatAffineConstraints API

PiperOrigin-RevId: 221889223
2019-03-29 14:00:51 -07:00
MLIR Team
cd051dc634 Bug fixes in FlatAffineConstraints. Tests cases that discovered these in follow up CL on memref dependence checks.
PiperOrigin-RevId: 220632386
2019-03-29 13:51:47 -07:00
Uday Bondhugula
6cd5d5c544 Introduce loop tiling code generation (hyper-rectangular case)
- simple perfectly nested band tiling with fixed tile sizes.
- only the hyper-rectangular case is handled, with other limitations of
  getIndexSet applying (constant loop bounds, etc.);  once
  the latter utility is extended, tiled code generation should become more
  general.
- Add FlatAffineConstraints::isHyperRectangular()

PiperOrigin-RevId: 220324933
2019-03-29 13:49:05 -07:00
Uday Bondhugula
4269a01863 Clean up memref dep check utilities; update FlatAffineConstraints API, add
simple utility methods.

- clean up some of the analysis utilities used by memref dep checking
- add additional asserts / comments at places in analysis utilities
- add additional simple methods to the FlatAffineConstraints API.

PiperOrigin-RevId: 220124523
2019-03-29 13:48:35 -07:00
Uday Bondhugula
74c62c8ce0 Complete memref bound checker for arbitrary affine expressions. Handle local
variables from mod's and div's when converting to flat form.

- propagate mod, floordiv, ceildiv / local variables constraint information
  when flattening affine expressions and converting them into flat affine
  constraints; resolve multiple TODOs.
- enables memref bound checker to work with arbitrary affine expressions
- update FlatAffineConstraints API with several new methods
- test/exercise functionality mostly through -memref-bound-check
- other analyses such as dependence tests, etc. should now be able to work in the
  presence of any affine composition of add, mul, floor, ceil, mod.

PiperOrigin-RevId: 219711806
2019-03-29 13:47:29 -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
Uday Bondhugula
8201e19e3d Introduce memref bound checking.
Introduce analysis to check memref accesses (in MLFunctions) for out of bound
ones. It works as follows:

$ mlir-opt -memref-bound-check test/Transforms/memref-bound-check.mlir

/tmp/single.mlir:10:12: error: 'load' op memref out of upper bound access along dimension tensorflow/mlir#1
      %x = load %A[%idxtensorflow/mlir#0, %idxtensorflow/mlir#1] : memref<9 x 9 x i32>
           ^
/tmp/single.mlir:10:12: error: 'load' op memref out of lower bound access along dimension tensorflow/mlir#1
      %x = load %A[%idxtensorflow/mlir#0, %idxtensorflow/mlir#1] : memref<9 x 9 x i32>
           ^
/tmp/single.mlir:10:12: error: 'load' op memref out of upper bound access along dimension tensorflow/mlir#2
      %x = load %A[%idxtensorflow/mlir#0, %idxtensorflow/mlir#1] : memref<9 x 9 x i32>
           ^
/tmp/single.mlir:10:12: error: 'load' op memref out of lower bound access along dimension tensorflow/mlir#2
      %x = load %A[%idxtensorflow/mlir#0, %idxtensorflow/mlir#1] : memref<9 x 9 x i32>
           ^
/tmp/single.mlir:12:12: error: 'load' op memref out of upper bound access along dimension tensorflow/mlir#1
      %y = load %B[%idy] : memref<128 x i32>
           ^
/tmp/single.mlir:12:12: error: 'load' op memref out of lower bound access along dimension tensorflow/mlir#1
      %y = load %B[%idy] : memref<128 x i32>
           ^
#map0 = (d0, d1) -> (d0, d1)
#map1 = (d0, d1) -> (d0 * 128 - d1)
mlfunc @test() {
  %0 = alloc() : memref<9x9xi32>
  %1 = alloc() : memref<128xi32>
  for %i0 = -1 to 9 {
    for %i1 = -1 to 9 {
      %2 = affine_apply #map0(%i0, %i1)
      %3 = load %0[%2tensorflow/mlir#0, %2tensorflow/mlir#1] : memref<9x9xi32>
      %4 = affine_apply #map1(%i0, %i1)
      %5 = load %1[%4] : memref<128xi32>
    }
  }
  return
}

- Improves productivity while manually / semi-automatically developing MLIR for
  testing / prototyping; also provides an indirect way to catch errors in
  transformations.

- This pass is an easy way to test the underlying affine analysis
  machinery including low level routines.

Some code (in getMemoryRegion()) borrowed from @andydavis cl/218263256.

While on this:

- create mlir/Analysis/Passes.h; move Pass.h up from mlir/Transforms/ to mlir/

- fix a bug in AffineAnalysis.cpp::toAffineExpr

TODO: extend to non-constant loop bounds (straightforward). Will transparently
work for all accesses once floordiv, mod, ceildiv are supported in the
AffineMap -> FlatAffineConstraints conversion.
PiperOrigin-RevId: 219397961
2019-03-29 13:46:08 -07:00
Uday Bondhugula
c5128e152a FlatAffineConstraints API update - additional methods
- add methods addConstantLowerBound, addConstantUpperBound, setIdToConstant,
  addDimsForMap
- update coefficient storage to use numReservedCols * rows instead of numCols *
  rows (makes the code simpler/natural; reduces movement of data when new
  columns are added, eliminates movement of data when columns are added to the
  end).

(addDimsForMap is tested in the child CL on memref bound checking: cl/219000460)

PiperOrigin-RevId: 219358376
2019-03-29 13:45:14 -07:00
Uday Bondhugula
1ec77cecf2 FourierMotzkinEliminate trivial bug fix
PiperOrigin-RevId: 219148982
2019-03-29 13:43:30 -07:00
River Riddle
6e6e40ae79 Move AffineMap.h/IntegerSet.h from Attributes.h to AttributeDetail.h where they belong.
PiperOrigin-RevId: 218806426
2019-03-29 13:41:05 -07:00
MLIR Team
13f6cc0187 Run GCD test before elimination. Adds test case with rational solutions, but no integer solutions.
PiperOrigin-RevId: 218772332
2019-03-29 13:39:34 -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
MLIR Team
5413239350 Adds Gaussian Elimination to FlatAffineConstraints.
- Adds FlatAffineConstraints::isEmpty method to test if there are no solutions to the system.
- Adds GCD test check if equality constraints have no solution.
- Adds unit test cases.

PiperOrigin-RevId: 218546319
2019-03-29 13:38:10 -07:00
Nicolas Vasilache
3013dadb7c [MLIR] Basic infrastructure for vectorization test
This CL implements a very simple loop vectorization **test** and the basic
infrastructure to support it.

The test simply consists in:
1. matching the loops in the MLFunction and all the Load/Store operations
nested under the loop;
2. testing whether all the Load/Store are contiguous along the innermost
memory dimension along that particular loop. If any reference is
non-contiguous (i.e. the ForStmt SSAValue appears in the expression), then
the loop is not-vectorizable.

The simple test above can gradually be extended with more interesting
behaviors to account for the fact that a layout permutation may exist that
enables contiguity etc. All these will come in due time but it is worthwhile
noting that the test already supports detection of outer-vetorizable loops.

In implementing this test, I also added a recursive MLFunctionMatcher and some
sugar that can capture patterns
such as `auto gemmLike = Doall(Doall(Red(LoadStore())))` and allows iterating
on the matched IR structures. For now it just uses in order traversal but
post-order DFS will be useful in the future once IR rewrites start occuring.

One may note that the memory management design decision follows a different
pattern from MLIR. After evaluating different designs and how they quickly
increase cognitive overhead, I decided to opt for the simplest solution in my
view: a class-wide (threadsafe) RAII context.

This way, a pass that needs MLFunctionMatcher can just have its own locally
scoped BumpPtrAllocator and everything is cleaned up when the pass is destroyed.
If passes are expected to have a longer lifetime, then the contexts can easily
be scoped inside the runOnMLFunction call and storage lifetime reduced.
Lastly, whatever the scope of threading (module, function, pass), this is
expected to also be future-proof wrt concurrency (but this is a detail atm).

PiperOrigin-RevId: 217622889
2019-03-29 13:32:13 -07:00
MLIR Team
0114e232d8 Adds method to AffineApplyOp which forward substitutes its results into any of its users which are also AffineApplyOps.
Updates ComposeAffineMaps test pass to use this method.
Updates affine map composition test cases to handle the new pass, which can be reused when this method is used in a future instruction combine pass.

PiperOrigin-RevId: 217163351
2019-03-29 13:30:49 -07:00
Jacques Pienaar
764fd035b0 Split BuiltinOps out of StandardOps.
* Move Return, Constant and AffineApply out into BuiltinOps;
* BuiltinOps are always registered, while StandardOps follow the same dynamic registration;
* Kept isValidX in MLValue as we don't have a verify on AffineMap so need to keep it callable from Parser (I wanted to move it to be called in verify instead);

PiperOrigin-RevId: 216592527
2019-03-29 13:28:12 -07:00