[Mlir-commits] [mlir] [mlir][xegpu] Add SIMT distribution patterns for UpdateNdOffset and PrefetchNd ops. (PR #138033)

[Chao Chen]

================
@@ -1412,6 +1431,150 @@ struct DpasDistribution final : public gpu::WarpDistributionPattern {
   }
 };
 
+/// Sink an update_nd_offset op feeding into yield op of an enclosing
+/// `gpu.warp_execute_on_lane_0` region. The warp op will still contain the
+/// original op that will not be used by the yield op (and should be cleaned
+/// up later). The yield op will bypass the updateOp's arguments. The tensor
+/// descriptor type is not distributed. Appropriate cast ops are inserted if
+/// the distributed types does not match expected xegpu SIMT types.
+/// Example:
+/// ```
+///   #lo0 = #xegpu.layout<wi_layout = [1, 8], wi_data = [1, 1]>
+///   %r = gpu.warp_execute_on_lane_0(%laneid) ->
+///                   (!xegpu.tensor_desc<4x8xf32, #lo0>) {
+///     ...
+///     %update = xegpu.update_nd_offset %arg0, [%c32, %c16]:
+///       !xegpu.tensor_desc<4x8xf32, #lo0>
+///     gpu.yield %update
+///   }
+///   ...
+/// ```
+/// To
+/// ```
+///   %r:2 = gpu.warp_execute_on_lane_0(%laneid) -> (vector<4x1xf32>,
+///   !xegpu.tensor_desc<4x8xf32, #lo0>) {
+///     ...
+///     %dead = xegpu.update_nd_offset %arg0, [%c32, %c16]:
+///       !xegpu.tensor_desc<4x8xf32, #lo0> gpu.yield %dead, %arg0
+///     gup.yield %dead, %arg0, %c32, %c16
+///   }
+///   %0 = xegpu.unrealized_conversion_cast %r#1: !xegpu.tensor_desc<4x8xf32,
+///        #lo0> -> !xegpu.tensor_desc<4x8xf32>
+///   %1 = xegpu.update_nd_offset %0, [%c32, %c16]:
+///     !xegpu.tensor_desc<4x8xf32>
+///   ...
+/// ```
+struct UpdateNdOffsetDistribution final : public gpu::WarpDistributionPattern {
+  using gpu::WarpDistributionPattern::WarpDistributionPattern;
+  LogicalResult matchAndRewrite(gpu::WarpExecuteOnLane0Op subgroupOp,
+                                PatternRewriter &rewriter) const override {
+    OpOperand *operand =
+        getWarpResult(subgroupOp, llvm::IsaPred<xegpu::UpdateNdOffsetOp>);
+    if (!operand)
+      return rewriter.notifyMatchFailure(
+          subgroupOp, "warp result is not a xegpu::UpdateNdOffset op");
+    auto updateOp = operand->get().getDefiningOp<xegpu::UpdateNdOffsetOp>();
+    unsigned operandIdx = operand->getOperandNumber();
+    // new update op does not have layout attribute.
+    xegpu::TensorDescType newTensorDescTy =
+        dropLayouts(updateOp.getTensorDescType());
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chencha3 wrote:

nit: do you mind putting dropLayout into TensorDescType. I feel it could be useful in many places. 

https://github.com/llvm/llvm-project/pull/138033