From 24e62148dd14a41f00f06a56af6c0892074176ee Mon Sep 17 00:00:00 2001
From: Tanyo Kwok <tianyou.gty@alibaba-inc.com>
Date: Wed, 20 Jul 2022 10:50:39 +0800
Subject: [PATCH] Add decomposition for aten::native_layer_norm (#13)

---
 .../Torch/Transforms/DecomposeComplexOps.cpp  | 86 +++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/lib/Dialect/Torch/Transforms/DecomposeComplexOps.cpp b/lib/Dialect/Torch/Transforms/DecomposeComplexOps.cpp
index 77c0ec6d2610..2bbb3fa36b52 100644
--- a/lib/Dialect/Torch/Transforms/DecomposeComplexOps.cpp
+++ b/lib/Dialect/Torch/Transforms/DecomposeComplexOps.cpp
@@ -9,6 +9,7 @@
 
 #include "PassDetail.h"
 
+#include <numeric>
 #include "mlir/IR/BuiltinDialect.h"
 #include "mlir/Transforms/DialectConversion.h"
 #include "torch-mlir/Dialect/Torch/IR/TorchDialect.h"
@@ -1670,6 +1671,88 @@ class DecomposeAtenLayerNormOp : public OpRewritePattern<AtenLayerNormOp> {
 };
 } // namespace
 
+namespace {
+class DecomposeAtenNativeLayerNormOp
+    : public OpRewritePattern<AtenNativeLayerNormOp> {
+  using OpRewritePattern<AtenNativeLayerNormOp>::OpRewritePattern;
+  LogicalResult matchAndRewrite(AtenNativeLayerNormOp op,
+                                PatternRewriter &rewriter) const override {
+    Location loc = op.getLoc();
+    auto context = op.getContext();
+
+    auto inputTy = op.input().getType().cast<BaseTensorType>();
+    if (!inputTy.hasSizes())
+      return rewriter.notifyMatchFailure(
+          op, "input tensor should have known sizes.");
+    int64_t inputRank = inputTy.getSizes().size();
+    Value normalizedShape = op.normalized_shape();
+    SmallVector<Value> normalizedShapeSizesTorchInt;
+    getListConstructElements(normalizedShape, normalizedShapeSizesTorchInt);
+    int64_t axis = inputRank - normalizedShapeSizesTorchInt.size();
+    SmallVector<int64_t> reduceDimInts(normalizedShapeSizesTorchInt.size());
+    std::iota(reduceDimInts.begin(), reduceDimInts.end(), axis);
+    auto reducedTy = op.getResult(1).getType();
+    auto sizeListType = ListType::get(IntType::get(context));
+
+    // build reduce dims
+    SmallVector<Value> reduceDimVals;
+    reduceDimVals.reserve(reduceDimInts.size());
+    std::transform(reduceDimInts.begin(), reduceDimInts.end(),
+                   std::back_inserter(reduceDimVals), [&](int64_t d) {
+                     return rewriter.create<Torch::ConstantIntOp>(
+                         loc, rewriter.getI64IntegerAttr(d));
+                   });
+    Value reduceDimList =
+        rewriter.create<PrimListConstructOp>(loc, sizeListType, reduceDimVals);
+    Value one = rewriter.create<Torch::ConstantIntOp>(
+        loc, rewriter.getI64IntegerAttr(1));
+
+    Value cstTrue = rewriter.create<Torch::ConstantBoolOp>(loc, true);
+    Value none = rewriter.create<Torch::ConstantNoneOp>(loc);
+    // mean(x)
+    Value inputMean = rewriter.create<AtenMeanDimOp>(
+        loc, reducedTy, op.input(), reduceDimList, cstTrue, none);
+
+    // x - mean(x)
+    Value inputMeanExpanded = rewriter.create<AtenExpandAsOp>(loc, inputTy, inputMean, op.input());
+    Value inputZeroMean = rewriter.create<AtenSubTensorOp>(
+        loc, inputTy, op.input(), inputMeanExpanded, one);
+    // var(x) = mean((x - mean(x))^2)
+    Value inputZeroMeanSquare = rewriter.create<AtenMulTensorOp>(
+        loc, inputTy, inputZeroMean, inputZeroMean);
+    Value inputVar = rewriter.create<AtenMeanDimOp>(
+        loc, reducedTy, inputZeroMeanSquare, reduceDimList, cstTrue, none);
+
+    // rsqrt(var(x) + eps)
+    Value inputVarPlusEps = rewriter.create<AtenAddScalarOp>(
+        loc, reducedTy, inputVar, op.eps(), one);
+    Value inputRsqrtVar =
+        rewriter.create<AtenRsqrtOp>(loc, reducedTy, inputVarPlusEps);
+
+    // (x - mean(x)) * rsqrt(var(x) + eps)
+    Value inputRsqrtVarExpanded =
+        rewriter.create<AtenExpandAsOp>(loc, inputTy, inputRsqrtVar, op.input());
+    Value inputNormalized = rewriter.create<AtenMulTensorOp>(
+        loc, inputTy, inputZeroMean, inputRsqrtVarExpanded);
+    Value out = rewriter.create<TensorStaticInfoCastOp>(loc, op.getResult(0).getType(),
+                                                        inputNormalized);
+
+    Value weight = op.weight();
+    Value bias = op.bias();
+    if (!weight.getType().isa<Torch::NoneType>()) {
+      out = rewriter.create<AtenMulTensorOp>(loc, out.getType(), out, weight);
+    }
+    if (!bias.getType().isa<Torch::NoneType>()) {
+      out =
+          rewriter.create<AtenAddTensorOp>(loc, out.getType(), out, bias, one);
+    }
+    rewriter.replaceOp(op, {out, inputMean, inputRsqrtVar});
+
+    return success();
+  }
+};
+} // namespace
+
 namespace {
 // Decompose `aten.empty_like` op into `aten.size` and `aten.empty` ops.
 class DecomposeAtenEmptyLikeOp : public OpRewritePattern<AtenEmptyLikeOp> {
@@ -2676,6 +2759,9 @@ class DecomposeComplexOpsPass
     target.addIllegalOp<AtenAddcdivOp>();
     target.addIllegalOp<AtenLayerNormOp>();
     patterns.add<DecomposeAtenLayerNormOp>(context);
+    target.addIllegalOp<AtenNativeLayerNormOp>();
+    patterns.add<DecomposeAtenNativeLayerNormOp>(context);
+ 
     target.addIllegalOp<AtenNativeBatchNormOp>();
     patterns.add<DecomposeAtenNativeBatchNormOp>(context);
     target.addIllegalOp<AtenConvolutionOverrideableOp>();