[TORCH][MLIR] Add E2E support for `aten.gelu_backward` operation. (#418)

This commit adds new operation `aten.gelu_backward` in the aten
dialect and adds lowering of this operation from aten to linalg.

Signed-Off-By: Prateek Gupta <prateek@nod-labs.com>

e2e_testing/torchscript/backprop.py

@@ -53,3 +53,26 @@ class TanhBackwardModule(torch.nn.Module):
 def TanhBackward_basic(module, tu: TestUtils):
     module.forward(torch.randn(3, 3), torch.randn(3, 3))
 
+
+# ==============================================================================
+
+class GeluBackwardModule(torch.nn.Module):
+    def __init__(self):
+        super().__init__()
+        self.gelu = torch.nn.GELU()
+
+    @export
+    @annotate_args([
+        None,
+        ([-1, -1], torch.float32, True),
+        ([-1, -1], torch.float32, True),
+    ])
+    def forward(self, grad, input):
+        return torch.ops.aten.gelu_backward(grad, input)
+
+
+@register_test_case(module_factory=lambda: GeluBackwardModule())
+def GeluBackwardModule_basic(module, tu: TestUtils):
+    module.forward(tu.rand(5, 3), tu.rand(5, 3))
+
+

include/torch-mlir/Dialect/Torch/IR/GeneratedAtenOps.td

@@ -2845,3 +2845,18 @@ def Torch_AtenTanhBackwardOp : Torch_Op<"aten.tanh_backward", [
   let assemblyFormat = "$grad_output `,` $output attr-dict `:` type($grad_output) `,` type($output) `->` type($result)";
 }
 
+def Torch_AtenGeluBackwardOp : Torch_Op<"aten.gelu_backward", [
+    AllowsTypeRefinement,
+    HasValueSemantics
+  ]> {
+  let summary = "Generated op for `aten::gelu_backward : (Tensor, Tensor) -> (Tensor)`";
+  let arguments = (ins
+    AnyTorchTensorType:$grad,
+    AnyTorchTensorType:$self
+  );
+  let results = (outs
+    AnyTorchTensorType:$result
+  );
+  let assemblyFormat = "$grad `,` $self attr-dict `:` type($grad) `,` type($self) `->` type($result)";
+}
+

lib/Conversion/TorchToLinalg/TorchToLinalg.cpp

@@ -1353,6 +1353,37 @@ static Value createLinalgPayloadCalculationForElementwiseOp(
     Value cdf = buildUnitNormalCdf(b, loc, payloadArgs[0]);
     return b.create<arith::MulFOp>(loc, payloadArgs[0], cdf);
   }
+  if (auto geluBackward = dyn_cast<AtenGeluBackwardOp>(op)) {
+    if (!geluBackward.getType()
+             .cast<ValueTensorType>()
+             .getDtype()
+             .isa<mlir::FloatType>()) {
+      geluBackward.emitError("unimplemented: non-floating point dtype");
+      return nullptr;
+    }
+    Type elementType = payloadArgs[1].getType();
+    Value constant0 = b.create<arith::ConstantOp>(
+        loc, FloatAttr::get(elementType, 1.12837916709551257390));
+    Value constant1 = b.create<arith::ConstantOp>(
+        loc, FloatAttr::get(elementType, 0.70710678118654752440));
+    Value oneHalf =
+        b.create<arith::ConstantOp>(loc, FloatAttr::get(elementType, 0.5));
+    Value kAlpha = b.create<arith::MulFOp>(loc, constant0, constant1);
+    Value kAlphaHalf = b.create<arith::MulFOp>(loc, kAlpha, oneHalf);
+    Value negOneHalf =
+        b.create<arith::ConstantOp>(loc, FloatAttr::get(elementType, -0.5));
+    Value inputSquared =
+        b.create<arith::MulFOp>(loc, payloadArgs[1], payloadArgs[1]);
+    Value negHalfInputSquared =
+        b.create<arith::MulFOp>(loc, inputSquared, negOneHalf);
+    Value dinput = b.create<math::ExpOp>(loc, negHalfInputSquared);
+    Value cdf = buildUnitNormalCdf(b, loc, payloadArgs[1]);
+    Value dinputInput = b.create<arith::MulFOp>(loc, dinput, payloadArgs[1]);
+    Value dinputInputAlpha =
+        b.create<arith::MulFOp>(loc, dinputInput, kAlphaHalf);
+    Value cdfExt = b.create<arith::AddFOp>(loc, dinputInputAlpha, cdf);
+    return b.create<arith::MulFOp>(loc, payloadArgs[0], cdfExt);
+  }
   if (auto add = dyn_cast<AtenAddTensorOp>(op)) {
     AtenAddTensorOp::Adaptor adaptor(operands);
     Type dtype = converter->convertType(add.getType())
@@ -1716,8 +1747,8 @@ struct ConvertElementwiseOp : ConversionPattern {
   LogicalResult
   matchAndRewrite(Operation *op, ArrayRef<Value> operands,
                   ConversionPatternRewriter &rewriter) const override {
-    if (!isa<AtenTanhOp, AtenReluOp, AtenGeluOp, AtenAddTensorOp,
-             AtenMulTensorOp, AtenDivTensorOp, AtenSubTensorOp,
+    if (!isa<AtenTanhOp, AtenReluOp, AtenGeluOp, AtenGeluBackwardOp,
+             AtenAddTensorOp, AtenMulTensorOp, AtenDivTensorOp, AtenSubTensorOp,
              AtenLerpTensorOp, AtenSigmoidOp, AtenExpOp, AtenMinimumOp,
              AtenMaximumOp, AtenToDtypeOp, AtenClampOp, AtenRsubScalarOp,
              AtenLogOp, AtenSqrtOp, AtenFloorOp, AtenPowTensorScalarOp,
@@ -2871,12 +2902,12 @@ public:
     patterns.add<ConvertAtenLinearOp>(typeConverter, context);
     target.addIllegalOp<AtenBatchNormOp>();
     patterns.add<ConvertAtenBatchNormOp>(typeConverter, context);
-    target.addIllegalOp<AtenTanhOp, AtenReluOp, AtenGeluOp, AtenAddTensorOp,
-                        AtenMulTensorOp, AtenDivTensorOp, AtenSubTensorOp,
-                        AtenLerpTensorOp, AtenSigmoidOp, AtenMinimumOp,
-                        AtenMaximumOp, AtenToDtypeOp, AtenClampOp,
-                        AtenRsubScalarOp, AtenLogOp, AtenSqrtOp, AtenFloorOp,
-                        AtenPowTensorScalarOp, AtenLog2Op, AtenRsqrtOp>();
+    target.addIllegalOp<
+        AtenTanhOp, AtenReluOp, AtenGeluOp, AtenGeluBackwardOp, AtenAddTensorOp,
+        AtenMulTensorOp, AtenDivTensorOp, AtenSubTensorOp, AtenLerpTensorOp,
+        AtenSigmoidOp, AtenMinimumOp, AtenMaximumOp, AtenToDtypeOp, AtenClampOp,
+        AtenRsubScalarOp, AtenLogOp, AtenSqrtOp, AtenFloorOp,
+        AtenPowTensorScalarOp, AtenLog2Op, AtenRsqrtOp>();
     patterns.add<ConvertElementwiseOp>(typeConverter, context);
     target.addIllegalOp<AtenUnsqueezeOp>();
     patterns.add<ConvertAtenUnsqueezeOp>(typeConverter, context);

lib/Dialect/Torch/Transforms/RefineTypes.cpp

@@ -224,13 +224,14 @@ public:
   visitOperation(Operation *op,
                  ArrayRef<LatticeElement<ValueKnowledge> *> operands) final {
     if (isa<TensorStaticInfoCastOp, CopyToValueTensorOp, CopyToNonValueTensorOp,
-            AtenTanhOp, AtenBatchNormOp, AtenReluOp, AtenGeluOp, AtenEqScalarOp,
-            AtenGeScalarOp, AtenGtScalarOp, AtenNeScalarOp, AtenBitwiseNotOp,
-            AtenExpOp, AtenSinOp, AtenCosOp, AtenSigmoidOp, DerefineOp,
-            AtenToPrimDeviceOp, AtenCpuOp, AtenContiguousOp, AtenFill_ScalarOp,
-            AtenDetachOp, AtenMaskedFill_ScalarOp, AtenCopy_Op, AtenIndexPut_Op,
-            AtenCumsumOp, AtenLayerNormOp, AtenClampOp, AtenLogOp, AtenSqrtOp,
-            AtenFloorOp, AtenLog2Op, Aten_SoftmaxBackwardDataOp, AtenRsqrtOp,
+            AtenTanhOp, AtenBatchNormOp, AtenReluOp, AtenGeluOp,
+            AtenGeluBackwardOp, AtenEqScalarOp, AtenGeScalarOp, AtenGtScalarOp,
+            AtenNeScalarOp, AtenBitwiseNotOp, AtenExpOp, AtenSinOp, AtenCosOp,
+            AtenSigmoidOp, DerefineOp, AtenToPrimDeviceOp, AtenCpuOp,
+            AtenContiguousOp, AtenFill_ScalarOp, AtenDetachOp,
+            AtenMaskedFill_ScalarOp, AtenCopy_Op, AtenIndexPut_Op, AtenCumsumOp,
+            AtenLayerNormOp, AtenClampOp, AtenLogOp, AtenSqrtOp, AtenFloorOp,
+            AtenLog2Op, Aten_SoftmaxBackwardDataOp, AtenRsqrtOp,
             AtenTanhBackwardOp>(op)) {
       return getLatticeElement(op->getResult(0)).join(*operands[0]);
     }

python/torch_mlir/dialects/torch/importer/jit_ir/build_tools/torch_ods_gen.py

@@ -625,6 +625,7 @@ def emit_aten_ops(torch_ir_dir: str, registry: Registry):
         # backprop ops
         emit("aten::_softmax_backward_data : (Tensor, Tensor, int, int) -> (Tensor)")
         emit("aten::tanh_backward : (Tensor, Tensor) -> (Tensor)")
+        emit("aten::gelu_backward : (Tensor, Tensor) -> (Tensor)")
 
 
 def emit_quantized_ops(torch_ir_dir: str, registry: Registry):