[Mlir-commits] [mlir] [mlir][tensor] Loosen restrictions on folding dynamic reshapes (PR #137963)

[Ian Wood]

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@@ -31,64 +31,128 @@ mlir::getReassociationIndicesForReshape(ShapedType sourceType,
 std::optional<SmallVector<ReassociationIndices>>
 mlir::getReassociationIndicesForCollapse(ArrayRef<int64_t> sourceShape,
                                          ArrayRef<int64_t> targetShape) {
-  if (sourceShape.size() <= targetShape.size())
+  unsigned numSourceDims = sourceShape.size(),
+           numTargetDims = targetShape.size();
+  if (numSourceDims <= numTargetDims)
     return std::nullopt;
-  unsigned sourceDim = 0;
-  SmallVector<ReassociationIndices> reassociationMap;
-  reassociationMap.reserve(targetShape.size());
-
-  ReassociationIndices currIndices;
-  int64_t prodOfCollapsedDims = 1;
-  while (sourceDim < sourceShape.size()) {
-    unsigned targetDim = reassociationMap.size();
-    // If we have mapped all the target dimensions stop and handle the remaining
-    // tail of size-1 dimensions explicitly.
-    if (targetDim == targetShape.size())
-      break;
-
-    int64_t currTargetShape = targetShape[targetDim];
-    while (sourceDim < (sourceShape.size() - 1) &&
-           sourceShape[sourceDim] != ShapedType::kDynamic &&
-           prodOfCollapsedDims * sourceShape[sourceDim] < currTargetShape) {
-      prodOfCollapsedDims *= sourceShape[sourceDim];
-      currIndices.push_back(sourceDim++);
+  SmallVector<ReassociationIndices, 4> reassociationMap;
+  reassociationMap.reserve(numTargetDims);
+
+  unsigned sourceDimIdx = 0, targetDimIdx = 0;
+  // Source dimensions iteration logic for static target dimensions.
+  // FIXME: Instead of lambda-capturing this function's source shape index "in
+  // place", consider refactoring this into a separate function.
+  auto collectSourceIndicesForStaticTargetDim =
+      [&](int64_t targetShape,
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IanWood1 wrote:

This `targetShape` shadows `ArrayRef<int64_t> targetShape`. Also, its just a single integer so maybe `targetSize` is better?

https://github.com/llvm/llvm-project/pull/137963