[MLIR][KernelGen] Add asin kernels and tests

PiperOrigin-RevId: 351381423

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

@@ -359,6 +359,19 @@ def HLOClient_AcosOp : HLOClient_UnaryElementwiseOp<"acos", [],
   }];
 }
 
+def HLOClient_AsinOp : HLOClient_UnaryElementwiseOp<"asin", [],
+    HLO_FpOrComplexTensor> {
+  let summary = "Asin operator";
+
+  let description = [{
+    Returns `Asin(operand)` element-wise.
+
+    $$
+    \asin(x) = 2 * atan(x / (1 + sqrt(1 - x^2)))
+    $$
+  }];
+}
+
 def HLOClient_AtanOp : HLOClient_UnaryElementwiseOp<"atan", [],
     HLO_FpOrComplexTensor> {
   let summary = "Atan operator";

lib/Dialect/mhlo/transforms/chlo_legalize_to_hlo_patterns.td

@@ -60,6 +60,25 @@ def : Pat<(HLOClient_AcosOp NonComplexElementType:$input),
     (HLO_ConstantLike<"M_PI"> $input)
   )>;
 
+// Expand asin to MHLO dialect as follows:
+//   asin(x) = 2 * atan(x / (1 + sqrt(1 - x^2)))
+def : Pat<(HLOClient_AsinOp $input),
+  (HLO_MulOp
+    (HLO_ConstantLike<"2"> $input),
+    (HLO_Atan2Op
+      $input,
+      (HLO_AddOp
+        (HLO_ConstantLike<"1"> $input),
+        (HLO_SqrtOp
+          (HLO_SubOp
+            (HLO_ConstantLike<"1"> $input),
+            (HLO_MulOp $input, $input)
+          )
+        )
+      )
+    )
+  )>;
+
 // Express `atan` as
 //   atan(x) = atan2(x, 1)
 def : Pat<(HLOClient_AtanOp $input),

lib/Dialect/mhlo/transforms/transform_unranked_hlo.cc

@@ -51,8 +51,8 @@ namespace {
 
 // TODO(herhut): Generate these out of op definitions.
 #define MAP_CHLO_OPERATION_CWISE_UNARY(fn, sep)                         \
-  fn(AcosOp) sep fn(AtanOp) sep fn(ConjOp) sep fn(ErfOp) sep fn(ErfcOp) \
-      sep fn(SinhOp) sep fn(TanOp)
+  fn(AcosOp) sep fn(AsinOp) sep fn(AtanOp) sep fn(ConjOp) sep fn(ErfOp) \
+      sep fn(ErfcOp) sep fn(SinhOp) sep fn(TanOp)
 
 template <typename OpTy>
 inline void AddLegalOpOnRankedTensor(ConversionTarget *target) {