[Mlir-commits] [mlir] [mlir][Vector] Promote buffers accessed via dynamic subviews and memref.copy (PR #217793)

[Jianhui Li]

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@@ -84,43 +92,156 @@ getPromotableSubViewOffsets(memref::SubViewOp subView) {
        llvm::zip_equal(subView.getMixedSizes(), resType.getShape())) {
     std::optional<int64_t> s = getConstantIntValue(size);
     if (!s || *s != dim)
-      return std::nullopt;
+      return false;
+  }
+  return true;
+}
+
+/// Returns the static offsets of `subView` within the parent vector for
+/// `vector.extract_strided_slice` and `vector.insert_strided_slice`.
+static SmallVector<int64_t> getStaticSubViewOffsets(memref::SubViewOp subView) {
+  SmallVector<int64_t> offsets;
+  for (OpFoldResult offset : subView.getMixedOffsets()) {
+    std::optional<int64_t> value = getConstantIntValue(offset);
+    assert(value && "expected a static offset");
+    offsets.push_back(*value);
   }
   return offsets;
 }
+
+/// Returns whether `subView` can be promoted as an alias of the whole parent
+/// vector. Static shapes are handled by `isAliasableStaticShapeSubView`
+/// instead.
+static bool isAliasableDynamicShapeSubView(memref::SubViewOp subView) {
+  // The parent must be statically shaped so the slot has a fixed-shape vector
+  // type; only the subview's sizes may be dynamic.
+  auto srcType = dyn_cast<MemRefType>(subView.getSource().getType());
+  auto resType = dyn_cast<MemRefType>(subView.getResult().getType());
+  if (!srcType || !resType || !srcType.hasStaticShape())
+    return false;
+
+  // At least one dynamic result dimension; a fully static sub-slice is handled
+  // by `isAliasableStaticShapeSubView` instead.
+  if (resType.hasStaticShape())
+    return false;
+
+  // Same rank: the read/write vector matches the parent rank.
+  if (srcType.getRank() != resType.getRank())
+    return false;
+
+  // Unit strides and zero offsets: a leading, contiguous sub-region starting at
+  // the parent's origin, so the valid region on each dim is exactly [0, size).
+  if (!subView.hasUnitStride() || !subView.hasZeroOffset())
+    return false;
+
+  return VectorType::isValidElementType(srcType.getElementType());
+}
+
+/// The vector type covering `subView`'s whole parent buffer, which is the type
+/// the alias slot of a dynamically-shaped subview takes.
+static VectorType getWholeParentVectorType(memref::SubViewOp subView) {
+  auto parentType = cast<MemRefType>(subView.getSource().getType());
----------------
Jianhui-Li wrote:

memref.subview can be applied on top of other subview (recursively), as long as the lower level subview are all static. This PR support such nested subview usage cases. 
There is a test: dyn_subview_of_static_subview in mem2reg-dynamic-subview.mlir

https://github.com/llvm/llvm-project/pull/217793