MLIR  20.0.0git
IndependenceTransforms.cpp
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1 //===- IndependenceTransforms.cpp - Make ops independent of values --------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
10 
16 
17 using namespace mlir;
18 using namespace mlir::memref;
19 
20 /// Make the given OpFoldResult independent of all independencies.
21 static FailureOr<OpFoldResult> makeIndependent(OpBuilder &b, Location loc,
22  OpFoldResult ofr,
23  ValueRange independencies) {
24  if (ofr.is<Attribute>())
25  return ofr;
26  AffineMap boundMap;
27  ValueDimList mapOperands;
29  boundMap, mapOperands, presburger::BoundType::UB, ofr, independencies,
30  /*closedUB=*/true)))
31  return failure();
32  return affine::materializeComputedBound(b, loc, boundMap, mapOperands);
33 }
34 
35 FailureOr<Value> memref::buildIndependentOp(OpBuilder &b,
36  memref::AllocaOp allocaOp,
37  ValueRange independencies) {
39  b.setInsertionPoint(allocaOp);
40  Location loc = allocaOp.getLoc();
41 
43  for (OpFoldResult ofr : allocaOp.getMixedSizes()) {
44  auto ub = makeIndependent(b, loc, ofr, independencies);
45  if (failed(ub))
46  return failure();
47  newSizes.push_back(*ub);
48  }
49 
50  // Return existing memref::AllocaOp if nothing has changed.
51  if (llvm::equal(allocaOp.getMixedSizes(), newSizes))
52  return allocaOp.getResult();
53 
54  // Create a new memref::AllocaOp.
55  Value newAllocaOp =
56  b.create<AllocaOp>(loc, newSizes, allocaOp.getType().getElementType());
57 
58  // Create a memref::SubViewOp.
59  SmallVector<OpFoldResult> offsets(newSizes.size(), b.getIndexAttr(0));
60  SmallVector<OpFoldResult> strides(newSizes.size(), b.getIndexAttr(1));
61  return b
62  .create<SubViewOp>(loc, newAllocaOp, offsets, allocaOp.getMixedSizes(),
63  strides)
64  .getResult();
65 }
66 
67 /// Push down an UnrealizedConversionCastOp past a SubViewOp.
68 static UnrealizedConversionCastOp
70  UnrealizedConversionCastOp conversionOp, SubViewOp op) {
71  OpBuilder::InsertionGuard g(rewriter);
72  rewriter.setInsertionPoint(op);
73  auto newResultType = cast<MemRefType>(SubViewOp::inferRankReducedResultType(
74  op.getType().getShape(), op.getSourceType(), op.getMixedOffsets(),
75  op.getMixedSizes(), op.getMixedStrides()));
76  Value newSubview = rewriter.create<SubViewOp>(
77  op.getLoc(), newResultType, conversionOp.getOperand(0),
78  op.getMixedOffsets(), op.getMixedSizes(), op.getMixedStrides());
79  auto newConversionOp = rewriter.create<UnrealizedConversionCastOp>(
80  op.getLoc(), op.getType(), newSubview);
81  rewriter.replaceAllUsesWith(op.getResult(), newConversionOp->getResult(0));
82  return newConversionOp;
83 }
84 
85 /// Given an original op and a new, modified op with the same number of results,
86 /// whose memref return types may differ, replace all uses of the original op
87 /// with the new op and propagate the new memref types through the IR.
88 ///
89 /// Example:
90 /// %from = memref.alloca(%sz) : memref<?xf32>
91 /// %to = memref.subview ... : ... to memref<?xf32, strided<[1], offset: ?>>
92 /// memref.store %cst, %from[%c0] : memref<?xf32>
93 ///
94 /// In the above example, all uses of %from are replaced with %to. This can be
95 /// done directly for ops such as memref.store. For ops that have memref results
96 /// (e.g., memref.subview), the result type may depend on the operand type, so
97 /// we cannot just replace all uses. There is special handling for common memref
98 /// ops. For all other ops, unrealized_conversion_cast is inserted.
100  Operation *from, Operation *to) {
101  assert(from->getNumResults() == to->getNumResults() &&
102  "expected same number of results");
103  OpBuilder::InsertionGuard g(rewriter);
104  rewriter.setInsertionPointAfter(to);
105 
106  // Wrap new results in unrealized_conversion_cast and replace all uses of the
107  // original op.
108  SmallVector<UnrealizedConversionCastOp> unrealizedConversions;
109  for (const auto &it :
110  llvm::enumerate(llvm::zip(from->getResults(), to->getResults()))) {
111  unrealizedConversions.push_back(rewriter.create<UnrealizedConversionCastOp>(
112  to->getLoc(), std::get<0>(it.value()).getType(),
113  std::get<1>(it.value())));
114  rewriter.replaceAllUsesWith(from->getResult(it.index()),
115  unrealizedConversions.back()->getResult(0));
116  }
117 
118  // Push unrealized_conversion_cast ops further down in the IR. I.e., try to
119  // wrap results instead of operands in a cast.
120  for (int i = 0; i < static_cast<int>(unrealizedConversions.size()); ++i) {
121  UnrealizedConversionCastOp conversion = unrealizedConversions[i];
122  assert(conversion->getNumOperands() == 1 &&
123  conversion->getNumResults() == 1 &&
124  "expected single operand and single result");
125  SmallVector<Operation *> users = llvm::to_vector(conversion->getUsers());
126  for (Operation *user : users) {
127  // Handle common memref dialect ops that produce new memrefs and must
128  // be recreated with the new result type.
129  if (auto subviewOp = dyn_cast<SubViewOp>(user)) {
130  unrealizedConversions.push_back(
131  propagateSubViewOp(rewriter, conversion, subviewOp));
132  continue;
133  }
134 
135  // TODO: Other memref ops such as memref.collapse_shape/expand_shape
136  // should also be handled here.
137 
138  // Skip any ops that produce MemRef result or have MemRef region block
139  // arguments. These may need special handling (e.g., scf.for).
140  if (llvm::any_of(user->getResultTypes(),
141  [](Type t) { return isa<MemRefType>(t); }))
142  continue;
143  if (llvm::any_of(user->getRegions(), [](Region &r) {
144  return llvm::any_of(r.getArguments(), [](BlockArgument bbArg) {
145  return isa<MemRefType>(bbArg.getType());
146  });
147  }))
148  continue;
149 
150  // For all other ops, we assume that we can directly replace the operand.
151  // This may have to be revised in the future; e.g., there may be ops that
152  // do not support non-identity layout maps.
153  for (OpOperand &operand : user->getOpOperands()) {
154  if ([[maybe_unused]] auto castOp =
155  operand.get().getDefiningOp<UnrealizedConversionCastOp>()) {
156  rewriter.modifyOpInPlace(
157  user, [&]() { operand.set(conversion->getOperand(0)); });
158  }
159  }
160  }
161  }
162 
163  // Erase all unrealized_conversion_cast ops without uses.
164  for (auto op : unrealizedConversions)
165  if (op->getUses().empty())
166  rewriter.eraseOp(op);
167 }
168 
170  memref::AllocaOp allocaOp,
171  ValueRange independencies) {
172  auto replacement =
173  memref::buildIndependentOp(rewriter, allocaOp, independencies);
174  if (failed(replacement))
175  return failure();
176  replaceAndPropagateMemRefType(rewriter, allocaOp,
177  replacement->getDefiningOp());
178  return replacement;
179 }
180 
181 memref::AllocaOp memref::allocToAlloca(
182  RewriterBase &rewriter, memref::AllocOp alloc,
183  function_ref<bool(memref::AllocOp, memref::DeallocOp)> filter) {
184  memref::DeallocOp dealloc = nullptr;
185  for (Operation &candidate :
186  llvm::make_range(alloc->getIterator(), alloc->getBlock()->end())) {
187  dealloc = dyn_cast<memref::DeallocOp>(candidate);
188  if (dealloc && dealloc.getMemref() == alloc.getMemref() &&
189  (!filter || filter(alloc, dealloc))) {
190  break;
191  }
192  }
193 
194  if (!dealloc)
195  return nullptr;
196 
197  OpBuilder::InsertionGuard guard(rewriter);
198  rewriter.setInsertionPoint(alloc);
199  auto alloca = rewriter.replaceOpWithNewOp<memref::AllocaOp>(
200  alloc, alloc.getMemref().getType(), alloc.getOperands());
201  rewriter.eraseOp(dealloc);
202  return alloca;
203 }
static void replaceAndPropagateMemRefType(RewriterBase &rewriter, Operation *from, Operation *to)
Given an original op and a new, modified op with the same number of results, whose memref return type...
static FailureOr< OpFoldResult > makeIndependent(OpBuilder &b, Location loc, OpFoldResult ofr, ValueRange independencies)
Make the given OpFoldResult independent of all independencies.
static UnrealizedConversionCastOp propagateSubViewOp(RewriterBase &rewriter, UnrealizedConversionCastOp conversionOp, SubViewOp op)
Push down an UnrealizedConversionCastOp past a SubViewOp.
A multi-dimensional affine map Affine map's are immutable like Type's, and they are uniqued.
Definition: AffineMap.h:46
Attributes are known-constant values of operations.
Definition: Attributes.h:25
IntegerAttr getIndexAttr(int64_t value)
Definition: Builders.cpp:148
This class defines the main interface for locations in MLIR and acts as a non-nullable wrapper around...
Definition: Location.h:66
RAII guard to reset the insertion point of the builder when destroyed.
Definition: Builders.h:357
This class helps build Operations.
Definition: Builders.h:216
void setInsertionPoint(Block *block, Block::iterator insertPoint)
Set the insertion point to the specified location.
Definition: Builders.h:407
Operation * create(const OperationState &state)
Creates an operation given the fields represented as an OperationState.
Definition: Builders.cpp:497
void setInsertionPointAfter(Operation *op)
Sets the insertion point to the node after the specified operation, which will cause subsequent inser...
Definition: Builders.h:421
This class represents a single result from folding an operation.
Definition: OpDefinition.h:268
This class represents an operand of an operation.
Definition: Value.h:267
Operation is the basic unit of execution within MLIR.
Definition: Operation.h:88
OpResult getResult(unsigned idx)
Get the 'idx'th result of this operation.
Definition: Operation.h:402
Location getLoc()
The source location the operation was defined or derived from.
Definition: Operation.h:223
result_range getResults()
Definition: Operation.h:410
unsigned getNumResults()
Return the number of results held by this operation.
Definition: Operation.h:399
This class contains a list of basic blocks and a link to the parent operation it is attached to.
Definition: Region.h:26
This class coordinates the application of a rewrite on a set of IR, providing a way for clients to tr...
Definition: PatternMatch.h:400
void replaceAllUsesWith(Value from, Value to)
Find uses of from and replace them with to.
Definition: PatternMatch.h:644
virtual void eraseOp(Operation *op)
This method erases an operation that is known to have no uses.
void modifyOpInPlace(Operation *root, CallableT &&callable)
This method is a utility wrapper around an in-place modification of an operation.
Definition: PatternMatch.h:636
OpTy replaceOpWithNewOp(Operation *op, Args &&...args)
Replace the results of the given (original) op with a new op that is created without verification (re...
Definition: PatternMatch.h:542
Instances of the Type class are uniqued, have an immutable identifier and an optional mutable compone...
Definition: Types.h:74
static LogicalResult computeIndependentBound(AffineMap &resultMap, ValueDimList &mapOperands, presburger::BoundType type, const Variable &var, ValueRange independencies, bool closedUB=false)
Compute a bound in that is independent of all values in independencies.
This class provides an abstraction over the different types of ranges over Values.
Definition: ValueRange.h:381
This class represents an instance of an SSA value in the MLIR system, representing a computable value...
Definition: Value.h:96
OpFoldResult materializeComputedBound(OpBuilder &b, Location loc, AffineMap boundMap, ArrayRef< std::pair< Value, std::optional< int64_t >>> mapOperands)
Materialize an already computed bound with Affine dialect ops.
constexpr void enumerate(std::tuple< Tys... > &tuple, CallbackT &&callback)
Definition: Matchers.h:344
FailureOr< Value > buildIndependentOp(OpBuilder &b, AllocaOp allocaOp, ValueRange independencies)
Build a new memref::AllocaOp whose dynamic sizes are independent of all given independencies.
FailureOr< Value > replaceWithIndependentOp(RewriterBase &rewriter, memref::AllocaOp allocaOp, ValueRange independencies)
Build a new memref::AllocaOp whose dynamic sizes are independent of all given independencies.
memref::AllocaOp allocToAlloca(RewriterBase &rewriter, memref::AllocOp alloc, function_ref< bool(memref::AllocOp, memref::DeallocOp)> filter=nullptr)
Replaces the given alloc with the corresponding alloca and returns it if the following conditions are...
Include the generated interface declarations.
SmallVector< std::pair< Value, std::optional< int64_t > >> ValueDimList