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[mlir] Expose linearize/delinearize lowering transforms (#144156)
Moves the transformation logic from the AffineLinearizeOp and AffineDelinearizeOp lowerings into separate transform functions that can now be called separately. This provides a more controlled way to apply the op lowerings. --------- Signed-off-by: Max Dawkins <[email protected]>
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lines changed

2 files changed

+125
-107
lines changed

‎mlir/include/mlir/Dialect/Affine/Transforms/Transforms.h

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Original file line numberDiff line numberDiff line change
@@ -32,6 +32,20 @@ enum class BoundType;
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namespace affine {
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class AffineApplyOp;
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class AffineDelinearizeIndexOp;
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class AffineLinearizeIndexOp;
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/// Lowers `affine.delinearize_index` into a sequence of division and remainder
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/// operations.
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LogicalResult lowerAffineDelinearizeIndexOp(RewriterBase &rewriter,
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AffineDelinearizeIndexOp op);
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/// Lowers `affine.linearize_index` into a sequence of multiplications and
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/// additions. Make a best effort to sort the input indices so that
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/// the most loop-invariant terms are at the left of the additions
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/// to enable loop-invariant code motion.
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LogicalResult lowerAffineLinearizeIndexOp(RewriterBase &rewriter,
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AffineLinearizeIndexOp op);
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/// Populate patterns that expand affine index operations into more fundamental
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/// operations (not necessarily restricted to Affine dialect).

‎mlir/lib/Dialect/Affine/Transforms/AffineExpandIndexOps.cpp

Lines changed: 111 additions & 107 deletions
Original file line numberDiff line numberDiff line change
@@ -84,126 +84,130 @@ static SmallVector<Value> computeStrides(Location loc, RewriterBase &rewriter,
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return result;
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}
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LogicalResult
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affine::lowerAffineDelinearizeIndexOp(RewriterBase &rewriter,
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AffineDelinearizeIndexOp op) {
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Location loc = op.getLoc();
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Value linearIdx = op.getLinearIndex();
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unsigned numResults = op.getNumResults();
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ArrayRef<int64_t> staticBasis = op.getStaticBasis();
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if (numResults == staticBasis.size())
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staticBasis = staticBasis.drop_front();
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if (numResults == 1) {
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rewriter.replaceOp(op, linearIdx);
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return success();
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}
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SmallVector<Value> results;
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results.reserve(numResults);
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SmallVector<Value> strides =
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computeStrides(loc, rewriter, op.getDynamicBasis(), staticBasis,
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/*knownNonNegative=*/true);
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Value zero = rewriter.createOrFold<arith::ConstantIndexOp>(loc, 0);
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Value initialPart =
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rewriter.create<arith::FloorDivSIOp>(loc, linearIdx, strides.front());
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results.push_back(initialPart);
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auto emitModTerm = [&](Value stride) -> Value {
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Value remainder = rewriter.create<arith::RemSIOp>(loc, linearIdx, stride);
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Value remainderNegative = rewriter.create<arith::CmpIOp>(
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loc, arith::CmpIPredicate::slt, remainder, zero);
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// If the correction is relevant, this term is <= stride, which is known
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// to be positive in `index`. Otherwise, while 2 * stride might overflow,
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// this branch won't be taken, so the risk of `poison` is fine.
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Value corrected = rewriter.create<arith::AddIOp>(
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loc, remainder, stride, arith::IntegerOverflowFlags::nsw);
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Value mod = rewriter.create<arith::SelectOp>(loc, remainderNegative,
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corrected, remainder);
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return mod;
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};
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// Generate all the intermediate parts
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for (size_t i = 0, e = strides.size() - 1; i < e; ++i) {
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Value thisStride = strides[i];
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Value nextStride = strides[i + 1];
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Value modulus = emitModTerm(thisStride);
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// We know both inputs are positive, so floorDiv == div.
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// This could potentially be a divui, but it's not clear if that would
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// cause issues.
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Value divided = rewriter.create<arith::DivSIOp>(loc, modulus, nextStride);
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results.push_back(divided);
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}
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results.push_back(emitModTerm(strides.back()));
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rewriter.replaceOp(op, results);
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return success();
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}
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LogicalResult affine::lowerAffineLinearizeIndexOp(RewriterBase &rewriter,
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AffineLinearizeIndexOp op) {
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// Should be folded away, included here for safety.
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if (op.getMultiIndex().empty()) {
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rewriter.replaceOpWithNewOp<arith::ConstantIndexOp>(op, 0);
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return success();
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}
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Location loc = op.getLoc();
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ValueRange multiIndex = op.getMultiIndex();
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size_t numIndexes = multiIndex.size();
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ArrayRef<int64_t> staticBasis = op.getStaticBasis();
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if (numIndexes == staticBasis.size())
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staticBasis = staticBasis.drop_front();
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SmallVector<Value> strides =
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computeStrides(loc, rewriter, op.getDynamicBasis(), staticBasis,
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/*knownNonNegative=*/op.getDisjoint());
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SmallVector<std::pair<Value, int64_t>> scaledValues;
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scaledValues.reserve(numIndexes);
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// Note: strides doesn't contain a value for the final element (stride 1)
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// and everything else lines up. We use the "mutable" accessor so we can get
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// our hands on an `OpOperand&` for the loop invariant counting function.
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for (auto [stride, idxOp] :
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llvm::zip_equal(strides, llvm::drop_end(op.getMultiIndexMutable()))) {
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Value scaledIdx = rewriter.create<arith::MulIOp>(
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loc, idxOp.get(), stride, arith::IntegerOverflowFlags::nsw);
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int64_t numHoistableLoops = numEnclosingInvariantLoops(idxOp);
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scaledValues.emplace_back(scaledIdx, numHoistableLoops);
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}
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scaledValues.emplace_back(
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multiIndex.back(),
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numEnclosingInvariantLoops(op.getMultiIndexMutable()[numIndexes - 1]));
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// Sort by how many enclosing loops there are, ties implicitly broken by
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// size of the stride.
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llvm::stable_sort(scaledValues,
184+
[&](auto l, auto r) { return l.second > r.second; });
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Value result = scaledValues.front().first;
187+
for (auto [scaledValue, numHoistableLoops] : llvm::drop_begin(scaledValues)) {
188+
std::ignore = numHoistableLoops;
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result = rewriter.create<arith::AddIOp>(loc, result, scaledValue,
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arith::IntegerOverflowFlags::nsw);
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}
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rewriter.replaceOp(op, result);
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return success();
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}
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87196
namespace {
88-
/// Lowers `affine.delinearize_index` into a sequence of division and remainder
89-
/// operations.
90197
struct LowerDelinearizeIndexOps
91198
: public OpRewritePattern<AffineDelinearizeIndexOp> {
92199
using OpRewritePattern<AffineDelinearizeIndexOp>::OpRewritePattern;
93200
LogicalResult matchAndRewrite(AffineDelinearizeIndexOp op,
94201
PatternRewriter &rewriter) const override {
95-
Location loc = op.getLoc();
96-
Value linearIdx = op.getLinearIndex();
97-
unsigned numResults = op.getNumResults();
98-
ArrayRef<int64_t> staticBasis = op.getStaticBasis();
99-
if (numResults == staticBasis.size())
100-
staticBasis = staticBasis.drop_front();
101-
102-
if (numResults == 1) {
103-
rewriter.replaceOp(op, linearIdx);
104-
return success();
105-
}
106-
107-
SmallVector<Value> results;
108-
results.reserve(numResults);
109-
SmallVector<Value> strides =
110-
computeStrides(loc, rewriter, op.getDynamicBasis(), staticBasis,
111-
/*knownNonNegative=*/true);
112-
113-
Value zero = rewriter.createOrFold<arith::ConstantIndexOp>(loc, 0);
114-
115-
Value initialPart =
116-
rewriter.create<arith::FloorDivSIOp>(loc, linearIdx, strides.front());
117-
results.push_back(initialPart);
118-
119-
auto emitModTerm = [&](Value stride) -> Value {
120-
Value remainder = rewriter.create<arith::RemSIOp>(loc, linearIdx, stride);
121-
Value remainderNegative = rewriter.create<arith::CmpIOp>(
122-
loc, arith::CmpIPredicate::slt, remainder, zero);
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// If the correction is relevant, this term is <= stride, which is known
124-
// to be positive in `index`. Otherwise, while 2 * stride might overflow,
125-
// this branch won't be taken, so the risk of `poison` is fine.
126-
Value corrected = rewriter.create<arith::AddIOp>(
127-
loc, remainder, stride, arith::IntegerOverflowFlags::nsw);
128-
Value mod = rewriter.create<arith::SelectOp>(loc, remainderNegative,
129-
corrected, remainder);
130-
return mod;
131-
};
132-
133-
// Generate all the intermediate parts
134-
for (size_t i = 0, e = strides.size() - 1; i < e; ++i) {
135-
Value thisStride = strides[i];
136-
Value nextStride = strides[i + 1];
137-
Value modulus = emitModTerm(thisStride);
138-
// We know both inputs are positive, so floorDiv == div.
139-
// This could potentially be a divui, but it's not clear if that would
140-
// cause issues.
141-
Value divided = rewriter.create<arith::DivSIOp>(loc, modulus, nextStride);
142-
results.push_back(divided);
143-
}
144-
145-
results.push_back(emitModTerm(strides.back()));
146-
147-
rewriter.replaceOp(op, results);
148-
return success();
202+
return affine::lowerAffineDelinearizeIndexOp(rewriter, op);
149203
}
150204
};
151205

152-
/// Lowers `affine.linearize_index` into a sequence of multiplications and
153-
/// additions. Make a best effort to sort the input indices so that
154-
/// the most loop-invariant terms are at the left of the additions
155-
/// to enable loop-invariant code motion.
156206
struct LowerLinearizeIndexOps final : OpRewritePattern<AffineLinearizeIndexOp> {
157207
using OpRewritePattern::OpRewritePattern;
158208
LogicalResult matchAndRewrite(AffineLinearizeIndexOp op,
159209
PatternRewriter &rewriter) const override {
160-
// Should be folded away, included here for safety.
161-
if (op.getMultiIndex().empty()) {
162-
rewriter.replaceOpWithNewOp<arith::ConstantIndexOp>(op, 0);
163-
return success();
164-
}
165-
166-
Location loc = op.getLoc();
167-
ValueRange multiIndex = op.getMultiIndex();
168-
size_t numIndexes = multiIndex.size();
169-
ArrayRef<int64_t> staticBasis = op.getStaticBasis();
170-
if (numIndexes == staticBasis.size())
171-
staticBasis = staticBasis.drop_front();
172-
173-
SmallVector<Value> strides =
174-
computeStrides(loc, rewriter, op.getDynamicBasis(), staticBasis,
175-
/*knownNonNegative=*/op.getDisjoint());
176-
SmallVector<std::pair<Value, int64_t>> scaledValues;
177-
scaledValues.reserve(numIndexes);
178-
179-
// Note: strides doesn't contain a value for the final element (stride 1)
180-
// and everything else lines up. We use the "mutable" accessor so we can get
181-
// our hands on an `OpOperand&` for the loop invariant counting function.
182-
for (auto [stride, idxOp] :
183-
llvm::zip_equal(strides, llvm::drop_end(op.getMultiIndexMutable()))) {
184-
Value scaledIdx = rewriter.create<arith::MulIOp>(
185-
loc, idxOp.get(), stride, arith::IntegerOverflowFlags::nsw);
186-
int64_t numHoistableLoops = numEnclosingInvariantLoops(idxOp);
187-
scaledValues.emplace_back(scaledIdx, numHoistableLoops);
188-
}
189-
scaledValues.emplace_back(
190-
multiIndex.back(),
191-
numEnclosingInvariantLoops(op.getMultiIndexMutable()[numIndexes - 1]));
192-
193-
// Sort by how many enclosing loops there are, ties implicitly broken by
194-
// size of the stride.
195-
llvm::stable_sort(scaledValues,
196-
[&](auto l, auto r) { return l.second > r.second; });
197-
198-
Value result = scaledValues.front().first;
199-
for (auto [scaledValue, numHoistableLoops] :
200-
llvm::drop_begin(scaledValues)) {
201-
std::ignore = numHoistableLoops;
202-
result = rewriter.create<arith::AddIOp>(loc, result, scaledValue,
203-
arith::IntegerOverflowFlags::nsw);
204-
}
205-
rewriter.replaceOp(op, result);
206-
return success();
210+
return affine::lowerAffineLinearizeIndexOp(rewriter, op);
207211
}
208212
};
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