Add simplification pattern to tm_tensor to linalg conversion

Attempts to compute whether or not each dimension in
a tm_tensor.npbroadcast op is either broadcasted or not. If all dims are
not broadcasted and the input and output ranks match, then the op is
folded away, else it generates a linalg style broadcast.

externals/llvm-external-projects/torch-mlir-dialects/lib/Dialect/TMTensor/Transforms/ConvertBroadcastToLinalg.cpp

@@ -13,6 +13,7 @@
 #include "mlir/Dialect/Tensor/IR/Tensor.h"
 #include "mlir/IR/BuiltinTypes.h"
 #include "mlir/IR/PatternMatch.h"
+#include "mlir/Interfaces/ValueBoundsOpInterface.h"
 #include "mlir/Pass/Pass.h"
 #include "mlir/Transforms/GreedyPatternRewriteDriver.h"
 #include "torch-mlir-dialects/Dialect/TMTensor/IR/TMTensorDialect.h"
@@ -26,7 +27,76 @@
 using namespace mlir;
 using namespace mlir::torch::TMTensor;
 
-/// Pattern rewriter hook to lower a `ScalarLoopOpInterface` to loops.
+namespace {
+class SimplifyNumpyBroadcast : public OpRewritePattern<NumpyBroadcastOp> {
+public:
+  using OpRewritePattern::OpRewritePattern;
+  LogicalResult matchAndRewrite(NumpyBroadcastOp broadcastOp,
+                                PatternRewriter &rewriter) const override {
+    Location loc = broadcastOp.getLoc();
+    Value input = broadcastOp.getInput();
+    Value output = broadcastOp.getOutput();
+    auto inputType = input.getType().cast<RankedTensorType>();
+    auto outputType = output.getType().cast<RankedTensorType>();
+    int64_t inputRank = inputType.getRank();
+    int64_t outputRank = outputType.getRank();
+    int64_t diff = outputRank - inputRank;
+
+    Value oneIndex =
+        rewriter.create<arith::ConstantOp>(loc, rewriter.getIndexAttr(1));
+
+    SmallVector<bool> broadcastedStatus;
+    for (int64_t i = 0, e = inputRank; i < e; ++i) {
+      FailureOr<bool> dimsEqual =
+          ValueBoundsConstraintSet::areEqual(input, output, i, i + diff);
+      if (succeeded(dimsEqual) && *dimsEqual) {
+        broadcastedStatus.push_back(false);
+        continue;
+      }
+      FailureOr<bool> isUnit =
+          ValueBoundsConstraintSet::areEqual(input, oneIndex, i, std::nullopt);
+      if (succeeded(isUnit) || *isUnit) {
+        broadcastedStatus.push_back(true);
+        continue;
+      }
+      // Unable to statically bound all input dims to a broadcast status; bail.
+      return failure();
+    }
+
+    // If no dims are broadcasted and the rank doesn't change, we can just fold
+    // the op away entirely.
+    if (!llvm::any_of(broadcastedStatus, [](bool b) { return b; }) &&
+        inputRank == outputRank) {
+      rewriter.replaceOpWithNewOp<tensor::CastOp>(
+          broadcastOp, broadcastOp.getResult(0).getType(), input);
+      return success();
+    }
+
+    SmallVector<AffineExpr> inputExprs;
+    for (int64_t i = 0, e = inputRank; i < e; ++i) {
+      if (broadcastedStatus[i]) {
+        inputExprs.push_back(rewriter.getAffineConstantExpr(0));
+        continue;
+      }
+      inputExprs.push_back(rewriter.getAffineDimExpr(i + diff));
+    }
+
+    SmallVector<AffineMap> indexingMaps = {
+        AffineMap::get(outputRank, 0, inputExprs, broadcastOp.getContext()),
+        rewriter.getMultiDimIdentityMap(outputRank)};
+    SmallVector<utils::IteratorType> iteratorTypes(
+        outputRank, utils::IteratorType::parallel);
+    rewriter.replaceOpWithNewOp<linalg::GenericOp>(
+        broadcastOp, output.getType(), input, output, indexingMaps,
+        iteratorTypes, [&](OpBuilder &b, Location loc, ValueRange args) {
+          b.create<linalg::YieldOp>(loc, args[0]);
+        });
+    return success();
+  }
+};
+} // namespace
+
+/// Pattern rewriter hook to lower a `tm_tensor.npbroadcast` to linalg.
 namespace {
 class LowerNumpyBroadcastToLinalg : public OpRewritePattern<NumpyBroadcastOp> {
 public:
@@ -106,6 +176,16 @@ struct TMTensorBroadcastToLinalgPass
   void runOnOperation() override {
     MLIRContext *context = &getContext();
 
+    {
+      RewritePatternSet patterns(context);
+      patterns.insert<SimplifyNumpyBroadcast>(context);
+      if (failed(applyPatternsAndFoldGreedily(getOperation(),
+                                              std::move(patterns)))) {
+        return signalPassFailure();
+      }
+    }
+
+    {
       RewritePatternSet patterns(context);
       patterns.insert<LowerNumpyBroadcastToLinalg>(context);
       if (failed(applyPatternsAndFoldGreedily(getOperation(),
@@ -113,6 +193,7 @@ struct TMTensorBroadcastToLinalgPass
         return signalPassFailure();
       }
     }
+  }
 };
 } // namespace