[XLA][MLIR] Lower `tf.Tan` and `tf.Sin` to MLHLO

Add `tan` op and lowering to CHLO dialect, move CHLO lowerings to
`chlo_legalize_to_hlo_patterns` and extend missing patterns.

PiperOrigin-RevId: 331506094

include/mlir-hlo/Dialect/mhlo/IR/chlo_ops.td

@@ -364,6 +364,19 @@ def HLOClient_AcosOp: HLOClient_UnaryElementwiseOp<"acos",
   }];
 }
 
+def HLOClient_TanOp : HLOClient_UnaryElementwiseOp<"tan",
+    [NoSideEffect, SameOperandsAndResultType], HLO_FpOrComplexTensor> {
+  let summary = "Tan operation";
+
+  let description = [{
+    Returns `Tan(operand)` element-wise.
+
+    $$
+    \tan(x) = \sin(x) / \cos(x)
+    $$
+  }];
+}
+
 def HLOClient_ConstantLikeOp : HLOClient_Op<"constant_like",
     [NoSideEffect, SameOperandsAndResultShape,
      InferTypeOpInterface,

lib/Dialect/mhlo/transforms/CMakeLists.txt

@@ -25,6 +25,10 @@ set(LLVM_TARGET_DEFINITIONS legalize_to_standard_patterns.td)
 mlir_tablegen(generated_legalize_to_standard.inc -gen-rewriters)
 add_public_tablegen_target(MLIRMhloLegalizeToStandardIncGen)
 
+set(LLVM_TARGET_DEFINITIONS chlo_legalize_to_hlo_patterns.td)
+mlir_tablegen(generated_chlo_legalize_to_hlo.inc -gen-rewriters)
+add_public_tablegen_target(MLIRChloLegalizeToHloIncGen)
+
 
 add_mlir_library(ChloPasses
   chlo_legalize_to_hlo.cc
@@ -32,6 +36,7 @@ add_mlir_library(ChloPasses
 
   DEPENDS
   MLIRhlo_opsIncGen
+  MLIRChloLegalizeToHloIncGen
 
   LINK_COMPONENTS
   Core

lib/Dialect/mhlo/transforms/chlo_legalize_to_hlo.cc

@@ -469,10 +469,13 @@ struct HloCompareAdaptor {
   }
 };
 
+#include "generated_chlo_legalize_to_hlo.inc"
 }  // namespace
 
 void PopulateLegalizeChloToHloPatterns(MLIRContext *context,
                                        OwningRewritePatternList *patterns) {
+  populateWithGenerated(context, patterns);
+
   // Instantiate conversion templates for conforming binary elementwise ops
   // that do not have different dtypes between operands and results and do
   // not have special attributes that need to be preserved.

lib/Dialect/mhlo/transforms/chlo_legalize_to_hlo_patterns.td

@@ -0,0 +1,59 @@
+/* Copyright 2020 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+// This is the legalization pattern definition file for CHLO to MHLO.
+
+include "mlir/IR/OpBase.td"
+include "mlir-hlo/Dialect/mhlo/IR/hlo_ops.td"
+include "mlir-hlo/Dialect/mhlo/IR/chlo_ops.td"
+
+//===----------------------------------------------------------------------===//
+// Unary op patterns.
+//===----------------------------------------------------------------------===//
+
+// Expand acos to MHLO dialect as follows:
+//   acos(x) = 2 * atan(sqrt(1 - x^2) / (1 + x))  if x != -1
+//           = pi                                 if x == -1
+def : Pat<(HLOClient_AcosOp $input),
+  (HLO_SelectOp
+    (HLO_CompareOp $input,
+      (HLO_ConstantLike<"0"> $input),
+      HLO_COMPARISON_DIRECTION_NE
+    ),
+    (HLO_MulOp
+      (HLO_ConstantLike<"2.0f"> $input),
+      (HLO_Atan2Op
+        (HLO_SqrtOp
+          (HLO_SubOp
+            (HLO_ConstantLike<"1"> $input),
+            (HLO_MulOp $input, $input)
+          )
+        ),
+        (HLO_AddOp
+          (HLO_ConstantLike<"1"> $input),
+          $input
+        )
+      )
+    ),
+    (HLO_ConstantLike<"M_PI"> $input))>;
+
+// Express tan in MHLO dialect as
+//   tan(x) = sin(x) / cos(x).
+def : Pat<(HLOClient_TanOp $input),
+  (HLO_DivOp
+    (HLO_SinOp $input),
+    (HLO_CosOp $input)
+  )>;
+

lib/Dialect/mhlo/transforms/hlo_legalize_to_lhlo.cc

@@ -515,6 +515,7 @@ void populateHLOToLHLOConversionPattern(
       HloToLhloOpConverter<mhlo::ReshapeOp>,
       HloToLhloOpConverter<mhlo::SelectOp>,
       HloToLhloOpConverter<mhlo::SignOp>,
+      HloToLhloOpConverter<mhlo::SinOp>,
       HloToLhloOpConverter<mhlo::SliceOp>,
       HloToLhloOpConverter<mhlo::SqrtOp>,
       HloToLhloOpConverter<mhlo::SubOp>,