[DXIL] Add tan intrinsic part 2 (#90277)

This change is an implementation of #87367's investigation on supporting
IEEE math operations as intrinsics.
Which was discussed in this RFC:
https://discourse.llvm.org/t/rfc-all-the-math-intrinsics/78294

If you want an overarching view of how this will all connect see:
#90088

Changes:
-  `llvm/include/llvm/IR/Intrinsics.td` - Create the tan intrinsic
- `llvm/lib/Target/DirectX/DXIL.td` - Map `int_tan` (the tan intrinsic)
to the equivalent DXIL Op.

Author: farzonl

llvm/lib/Target/DirectX/DXIL.td

@@ -266,6 +266,9 @@ def Cos  : DXILOpMapping<12, unary, int_cos,
 def Sin  : DXILOpMapping<13, unary, int_sin,
                          "Returns sine(theta) for theta in radians.",
                          [llvm_halforfloat_ty, LLVMMatchType<0>]>;
+def Tan  : DXILOpMapping<14, unary, int_tan,
+                         "Returns tangent(theta) for theta in radians.",
+                         [llvm_halforfloat_ty, LLVMMatchType<0>]>;
 def Exp2 : DXILOpMapping<21, unary, int_exp2,
                          "Returns the base 2 exponential, or 2**x, of the specified value."
                          "exp2(x) = 2**x.",

llvm/test/CodeGen/DirectX/tan.ll

@@ -0,0 +1,20 @@
+; RUN: opt -S -dxil-op-lower < %s | FileCheck %s
+
+; Make sure dxil operation function calls for tan are generated for float and half.
+
+define noundef float @tan_float(float noundef %a) #0 {
+entry:
+; CHECK:call float @dx.op.unary.f32(i32 14, float %{{.*}})
+  %elt.tan = call float @llvm.tan.f32(float %a)
+  ret float %elt.tan
+}
+
+define noundef half @tan_half(half noundef %a) #0 {
+entry:
+; CHECK:call half @dx.op.unary.f16(i32 14, half %{{.*}})
+  %elt.tan = call half @llvm.tan.f16(half %a)
+  ret half %elt.tan
+}
+
+declare half @llvm.tan.f16(half)
+declare float @llvm.tan.f32(float)

llvm/test/CodeGen/DirectX/tan_error.ll

@@ -0,0 +1,10 @@
+; RUN: not opt -S -dxil-op-lower %s 2>&1 | FileCheck %s
+
+; DXIL operation tan does not support double overload type
+; CHECK: LLVM ERROR: Invalid Overload
+
+define noundef double @tan_double(double noundef %a) #0 {
+entry:
+  %1 = call double @llvm.tan.f64(double %a)
+  ret double %1
+}