[MLIR][KernelGen] Add `tf.Asinh` kernels and complete their lowerings

PiperOrigin-RevId: 351989552

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

@@ -66,6 +66,8 @@ static Value getConstantLike(OpBuilder& b, Location loc, T constant,
   return b.create<ConstantLikeOp>(loc, getAttr(), val);
 }
 
+Value getConstantLikeMaxFiniteValue(OpBuilder& b, Location loc, Value val);
+
 }  // namespace chlo
 }  // namespace mlir
 

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

@@ -372,6 +372,18 @@ def HLOClient_AsinOp : HLOClient_UnaryElementwiseOp<"asin", [],
   }];
 }
 
+def HLOClient_AsinhOp : HLOClient_UnaryElementwiseOp<"asinh", [],
+    HLO_FpOrComplexTensor> {
+  let summary = "Asinh operation";
+
+  let description = [{
+    Returns `Asinh(operand)` element-wise.
+
+    $$
+    \asinh(x) = log(x + sqrt(x^2 + 1))
+    $$
+  }];
+}
 def HLOClient_AtanOp : HLOClient_UnaryElementwiseOp<"atan", [],
     HLO_FpOrComplexTensor> {
   let summary = "Atan operator";

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

@@ -30,6 +30,9 @@ class ConstantSplat<string value> : NativeCodeCall<
 class HLO_ConstantLike<string value> : NativeCodeCall<
     "chlo::getConstantLike($_builder, $_loc, " # value # ", $0)">;
 
+def HLO_ConstantLikeMaxFiniteValue : NativeCodeCall<
+    "chlo::getConstantLikeMaxFiniteValue($_builder, $_loc, $0)">;
+
 def NullDenseIntElementsAttr : NativeCodeCall<"DenseIntElementsAttr()">;
 
 def BinBroadcastDimensions : NativeCodeCall<

lib/Dialect/mhlo/IR/chlo_ops.cc

@@ -32,6 +32,20 @@ static LogicalResult Verify(T op) {
   return success();
 }
 
+static constexpr float kF16MaxFiniteValue = 0x1.ffcP15;
+
+Value getConstantLikeMaxFiniteValue(OpBuilder& b, Location loc, Value val) {
+  Type ty = getElementTypeOrSelf(val.getType());
+  if (ty.isF16()) {
+    return getConstantLike(b, loc, kF16MaxFiniteValue, val);
+  } else if (ty.isF32()) {
+    return getConstantLike(b, loc, std::numeric_limits<float>::max(), val);
+  } else if (ty.isF64()) {
+    return getConstantLike(b, loc, std::numeric_limits<double>::max(), val);
+  }
+  llvm_unreachable("unhandled type");
+}
+
 //===----------------------------------------------------------------------===//
 // BinaryOps
 //===----------------------------------------------------------------------===//

lib/Dialect/mhlo/transforms/chlo_legalize_to_hlo_patterns.td

@@ -79,6 +79,94 @@ def : Pat<(HLOClient_AsinOp NonComplexElementType:$input),
     )
   )>;
 
+// Expand asinh to MHLO dialect as
+//   asinh(x) = log(x + sqrt(x^2 + 1))
+//
+// If x^2 will overflow and x is positive, we can approximate x + sqrt(x^2 + 1)
+// as 2*x and return log(2) + log(x).
+//
+// For small x, sqrt(x^2 + 1) will evaluate to 1 due to floating point
+// arithmetic. However, we would like to retain the low order term of this,
+// which is around 0.5 * x^2 using a binomial expansion.
+// Let z = sqrt(a^2 + 1)
+// The following rewrite retains the lower order term.
+// log(a + sqrt(a^2 + 1))
+//   = log((a + sqrt(a^2 + 1)) * (1 + sqrt(a^2 + 1)) / (1 + sqrt(a^2 + 1)))
+//   = log((a + a^2 + 1 + a * z + z) / (1 + z))
+//   = log(1 + a + a^2 / (1 + z))
+//   = log(1 + a + a^2 / (1 + sqrt(a^2 + 1)))
+//
+// If x is negative, the above would give us some trouble; we can't approximate
+// the result as x + abs(x) = 0 but we are saved by the fact that asinh(-x) =
+// -asinh(x).
+def : Pat<(HLOClient_AsinhOp NonComplexElementType:$input),
+  (HLO_MulOp
+    (HLO_SignOp $input),
+    (HLO_SelectOp
+      (HLO_CompareOp
+        (HLO_AbsOp $input),
+        (HLO_SqrtOp
+          (HLO_ConstantLikeMaxFiniteValue $input)
+        ),
+        HLO_COMPARISON_DIRECTION_GE,
+        (HLO_DEFAULT_COMPARISON_TYPE)
+      ),
+      (HLO_AddOp
+        (HLO_LogOp
+          (HLO_AbsOp $input)
+        ),
+        (HLO_LogOp
+          (HLO_ConstantLike<"2"> $input)
+        )
+      ),
+      (HLO_SelectOp
+        (HLO_CompareOp
+          (HLO_AbsOp $input),
+          (HLO_ConstantLike<"1"> $input),
+          HLO_COMPARISON_DIRECTION_LE,
+          (HLO_DEFAULT_COMPARISON_TYPE)
+        ),
+        (HLO_Log1pOp
+          (HLO_AddOp
+            (HLO_AbsOp $input),
+            (HLO_MulOp
+              (HLO_AbsOp $input),
+              (HLO_DivOp
+                (HLO_AbsOp $input),
+                (HLO_AddOp
+                  (HLO_ConstantLike<"1"> $input),
+                  (HLO_SqrtOp
+                    (HLO_AddOp
+                      (HLO_MulOp
+                        (HLO_AbsOp $input),
+                        (HLO_AbsOp $input)
+                      ),
+                      (HLO_ConstantLike<"1"> $input)
+                    )
+                  )
+                )
+              )
+            )
+          )
+        ),
+        (HLO_LogOp
+          (HLO_AddOp
+            (HLO_AbsOp $input),
+            (HLO_SqrtOp
+              (HLO_AddOp
+                (HLO_MulOp
+                  (HLO_AbsOp $input),
+                  (HLO_AbsOp $input)
+                ),
+                (HLO_ConstantLike<"1"> $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(AsinOp) sep fn(AtanOp) sep fn(ConjOp) sep fn(CoshOp) \
+  fn(AcosOp) sep fn(AsinOp) sep fn(AsinhOp) sep fn(AtanOp) sep fn(ConjOp) \
-      sep fn(ErfOp) sep fn(ErfcOp) sep fn(SinhOp) sep fn(TanOp)
+      sep fn(CoshOp) sep fn(ErfOp) sep fn(ErfcOp) sep fn(SinhOp) sep fn(TanOp)
 
 template <typename OpTy>
 inline void AddLegalOpOnRankedTensor(ConversionTarget *target) {