[mlir][Vector] Support vector.insert in bubbling bitcast patterns (#82843)

This PR is adds support for `vector.insert` to the patterns that bubble up and down `vector.bitcat` ops across `vector.extract/extract_slice/insert_slice` ops.

1 files changed, 72 insertions, 2 deletions

diff --git a/mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp b/mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp
index 74dd1dfaca0d..a2d4e2166331 100644
--- a/mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp
+++ b/mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp
@@ -713,6 +713,76 @@ struct BubbleDownBitCastForStridedSliceExtract
 // Shuffles vector.bitcast op before vector.insert_strided_slice op.
 //
 // This transforms IR like:
+//   %0 = vector.insert %val, %dst[4] : vector<32xi4> into vector<8x32xi4>
+//   %1 = vector.bitcast %0 : vector<8x32xi4> to vector<8x16xi8>
+// Into:
+//   %0 = vector.bitcast %val : vector<32xi4> to vector<16xi8>
+//   %1 = vector.bitcast %dst : vector<8x32xi4> to vector<8x16xi8>
+//   %2 = vector.insert %0, %1 [4] : vector<16xi8> into vector<8x16xi8>
+//
+struct BubbleUpBitCastForInsert : public OpRewritePattern<vector::BitCastOp> {
+  using OpRewritePattern::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(vector::BitCastOp bitcastOp,
+                                PatternRewriter &rewriter) const override {
+    VectorType castSrcType = bitcastOp.getSourceVectorType();
+    VectorType castDstType = bitcastOp.getResultVectorType();
+
+    // 0-D and scalable vectors are not supported yet.
+    if (castSrcType.getRank() == 0 || castSrcType.isScalable() ||
+        castDstType.isScalable())
+      return failure();
+
+    int64_t castSrcLastDim = castSrcType.getShape().back();
+    int64_t castDstLastDim = castDstType.getShape().back();
+    bool isNumElemsShrink = castSrcLastDim >= castDstLastDim;
+    int64_t ratio;
+    if (isNumElemsShrink) {
+      assert(castSrcLastDim % castDstLastDim == 0);
+      ratio = castSrcLastDim / castDstLastDim;
+    } else {
+      assert(castDstLastDim % castSrcLastDim == 0);
+      ratio = castDstLastDim / castSrcLastDim;
+    }
+
+    auto insertOp = bitcastOp.getSource().getDefiningOp<vector::InsertOp>();
+    if (!insertOp)
+      return failure();
+
+    // Only vector sources are supported for now.
+    auto insertSrcType = dyn_cast<VectorType>(insertOp.getSourceType());
+    if (!insertSrcType)
+      return failure();
+
+    // Bitcast the source.
+    SmallVector<int64_t> srcDims(insertSrcType.getShape());
+    srcDims.back() =
+        isNumElemsShrink ? srcDims.back() / ratio : srcDims.back() * ratio;
+    VectorType newCastSrcType =
+        VectorType::get(srcDims, castDstType.getElementType());
+    auto newCastSrcOp = rewriter.create<vector::BitCastOp>(
+        bitcastOp.getLoc(), newCastSrcType, insertOp.getSource());
+
+    SmallVector<int64_t> dstDims(insertOp.getDestVectorType().getShape());
+    dstDims.back() =
+        isNumElemsShrink ? dstDims.back() / ratio : dstDims.back() * ratio;
+    VectorType newCastDstType =
+        VectorType::get(dstDims, castDstType.getElementType());
+
+    // Bitcast the destination.
+    auto newCastDstOp = rewriter.create<vector::BitCastOp>(
+        bitcastOp.getLoc(), newCastDstType, insertOp.getDest());
+
+    // Generate new insert.
+    rewriter.replaceOpWithNewOp<vector::InsertOp>(
+        bitcastOp, newCastSrcOp, newCastDstOp, insertOp.getMixedPosition());
+    return success();
+  }
+};
+
+// Shuffles vector.bitcast op before vector.insert_strided_slice op.
+//
+// This transforms IR like:
 //   %0 = vector.insert_strided_slice %src, %dst {
 //          offsets = [0], strides = [1]} : vector<4xf16> into vector<8xf16>
 //   %1 = vector.bitcast %0: vector<8xf16> to vector<4xf32>
@@ -1782,8 +1852,8 @@ void mlir::vector::populateBubbleVectorBitCastOpPatterns(
     RewritePatternSet &patterns, PatternBenefit benefit) {
   patterns.add<BubbleDownVectorBitCastForExtract,
                BubbleDownBitCastForStridedSliceExtract,
-               BubbleUpBitCastForStridedSliceInsert>(patterns.getContext(),
-                                                     benefit);
+               BubbleUpBitCastForInsert, BubbleUpBitCastForStridedSliceInsert>(
+      patterns.getContext(), benefit);
 }
 
 void mlir::vector::populateBreakDownVectorBitCastOpPatterns(