[Mlir-commits] [mlir] [mlir][Vector] Add a rewrite pattern for gather over a strided memref (PR #72991)

[Cullen Rhodes]

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@@ -96,6 +96,89 @@ struct FlattenGather : OpRewritePattern<vector::GatherOp> {
   }
 };
 
+/// Rewrites a vector.gather of a strided MemRef as a gather of a non-strided
+/// MemRef with updated indices that model the strided access.
+///
+/// ```mlir
+///   %subview = memref.subview %M (...)
+///     : memref<100x3xf32> to memref<100xf32, strided<[3]>>
+///   %gather = vector.gather %subview[%idxs] (...) : memref<100xf32, strided<[3]>>
+/// ```
+/// ==>
+/// ```mlir
+///   %collapse_shape = memref.collapse_shape %M (...)
+///     : memref<100x3xf32> into memref<300xf32>
+///   %new_idxs = arith.muli %idxs, %c3 : vector<4xindex>
+///   %gather = vector.gather %collapse_shape[%new_idxs] (...)
+///     : memref<300xf32> (...)
+/// ```
+///
+/// ATM this is effectively limited to reading a 1D Vector from a 2D MemRef,
+/// but should be fairly straightforward to extend beyond that.
+struct RemoveStrideFromGatherSource : OpRewritePattern<vector::GatherOp> {
+  using OpRewritePattern::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(vector::GatherOp op,
+                                PatternRewriter &rewriter) const override {
+    Value base = op.getBase();
+    if (!base.getDefiningOp())
+      return failure();
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c-rhodes wrote:

this can be removed now

https://github.com/llvm/llvm-project/pull/72991