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[Tensor] Simplify tenor.pad tiling length calculations. #119039

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merged 3 commits into from
Dec 12, 2024
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[Tensor] Simplify tenor.pad tiling length calculations. #119039

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[Tensor] Simplify tenor.pad tiling length calculations.
nirvedhmeshram Dec 6, 2024
473c00b
Address reviwer comments
nirvedhmeshram Dec 12, 2024
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nirvedhmeshram Dec 12, 2024
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23 changes: 8 additions & 15 deletions mlir/lib/Dialect/Tensor/IR/TensorTilingInterfaceImpl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -746,11 +746,6 @@ FailureOr<TilingResult> tensor::bubbleUpPadSlice(OpBuilder &b,
Location loc = padOp->getLoc();
AffineExpr dim0, dim1;
bindDims(b.getContext(), dim0, dim1);
// Add two integers.
auto addMap = AffineMap::get(2, 0, {dim0 + dim1});
auto add = [&](OpFoldResult v1, OpFoldResult v2) {
return affine::makeComposedFoldedAffineApply(b, loc, addMap, {v1, v2});
};
// Subtract two integers.
auto subMap = AffineMap::get(2, 0, {dim0 - dim1});
auto sub = [&](OpFoldResult v1, OpFoldResult v2) {
Expand Down Expand Up @@ -825,16 +820,14 @@ FailureOr<TilingResult> tensor::bubbleUpPadSlice(OpBuilder &b,
// The original read could also have stopped in the high padding zone.
// In that case, set the end positition of the read should be the end of
// the source tensor. (Similar to newOffset.)
//
// endLoc = min(max(offset - low + length, 0), srcSize)
//
// The new ExtractSliceOp length is `endLoc - newOffset`.
//
// Optimization: If low = 0, then the formula can be simplified.
OpFoldResult endLoc =
hasLowPad ? min(max(add(sub(offset, low), length), zero), srcSize)
: min(add(offset, length), srcSize);
OpFoldResult newLength = sub(endLoc, newOffset);
// srcSize - newOffset represents how much length we have available
// and length - newLow represents how much length we want at most.
// Note that there are many ways to order this indexing math to compute newLength, but we want to make sure that the final affine.min ops in the sequence are bounding the index to as small a value as possible. If ValueBoundsOpInterface is used, this calcuation will get upper bounds from the affine.min ops, so we want to use the smallest known value to set the bound at the end of the computation sequence. In this case, the index will be upper bounded by length - newLow.
OpFoldResult newLength = min(sub(srcSize, newOffset), sub(length, newLow));
// Optimization: If low = 0, then newLow = 0. then newLength >= 0 assuming
// length >= 0.
if (hasLowPad)
newLength = max(newLength, zero);
newLengths.push_back(newLength);

// Check if newLength is zero. In that case, no SubTensorOp should be
Expand Down
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