[HLSL] add sqrt library function

[bob80905]

Summary

This change exposes the sqrt library function for HLSL scalar types,
excluding long and long long doubles. Sqrt is supported for all scalar, vector,
and matrix types. This patch only adds a subset of scalar type support.

Long and long long double support is missing in this patch because that type
doesn't exist in HLSL.

The full documentation of the HLSL asin function is available here:
https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-sqrt

clang/lib/Headers/hlsl/hlsl_intrinsics.h

 abs(double);
 __attribute__((clang_builtin_alias(__builtin_elementwise_abs)))
 double2 abs(double2);
 __attribute__((clang_builtin_alias(__builtin_elementwise_abs)))
 double3 abs(double3);
 __attribute__((clang_builtin_alias(__builtin_elementwise_abs)))
 double4 abs(double4);
 
+// sqrt builtins
+__attribute__((clang_builtin_alias(__builtin_sqrt))) double sqrt(double In);
+__attribute__((clang_builtin_alias(__builtin_sqrtf))) float sqrt(float In);
+
+#ifdef __HLSL_ENABLE_16_BIT
+__attribute__((clang_builtin_alias(__builtin_sqrtf16))) half sqrt(half In);
+#endif
+
 #endif //_HLSL_HLSL_INTRINSICS_H_

clang/test/CodeGenHLSL/builtins/sqrt.hlsl

+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN:   dxil-pc-shadermodel6.2-library %s -fnative-half-type \
+// RUN:   -emit-llvm -disable-llvm-passes -o - | FileCheck %s
+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN:   dxil-pc-shadermodel6.2-library %s -emit-llvm -disable-llvm-passes \
+// RUN:   -o - | FileCheck %s --check-prefix=NO_HALF
+
+double sqrt_d(double x)
+{
+  return sqrt(x);
+}
+
+// CHECK: define noundef double @"?sqrt_d@@YANN@Z"(
+// CHECK: call double @llvm.sqrt.f64(double %0)
+
+float sqrt_f(float x)
+{
+  return sqrt(x);
+}
+
+// CHECK: define noundef float @"?sqrt_f@@YAMM@Z"(
+// CHECK: call float @llvm.sqrt.f32(float %0)
+
+half sqrt_h(half x)
+{
+  return sqrt(x);
+}
+
+// CHECK: define noundef half @"?sqrt_h@@YA$f16@$f16@@Z"(
+// CHECK: call half @llvm.sqrt.f16(half %0)
+// NO_HALF: define noundef float @"?sqrt_h@@YA$halff@$halff@@Z"(
+// NO_HALF: call float @llvm.sqrt.f32(float %0) sdasd
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