[ESIMD] Provide alternative version of subscript operator (#4313)

Author: DenisBakhvalov

sycl/include/sycl/ext/intel/experimental/esimd/detail/simd_view_impl.hpp

@@ -336,6 +336,15 @@ template <typename BaseTy, typename RegionTy> class simd_view_impl {
     return v[i];
   }
 
+  /// Read a single element from a 1D region, by value only.
+  template <typename T = simd_view_impl,
+            typename = sycl::detail::enable_if_t<T::is1D()>>
+  __SYCL_DEPRECATED("use operator[] form.")
+  element_type operator()(int i) const {
+    const auto v = read();
+    return v[i];
+  }
+
   /// \name Replicate
   /// Replicate simd instance given a simd_view
   /// @{

sycl/include/sycl/ext/intel/experimental/esimd/simd.hpp

@@ -195,11 +195,21 @@ template <typename Ty, int N> class simd {
   /// Read single element, return value only (not reference).
   Ty operator[](int i) const { return data()[i]; }
 
+  /// Read single element, return value only (not reference).
+  __SYCL_DEPRECATED("use operator[] form.")
+  Ty operator()(int i) const { return data()[i]; }
+
   /// Return writable view of a single element.
   simd_view<simd, region1d_t<Ty, 1, 0>> operator[](int i) {
     return select<1, 0>(i);
   }
 
+  /// Return writable view of a single element.
+  __SYCL_DEPRECATED("use operator[] form.")
+  simd_view<simd, region1d_t<Ty, 1, 0>> operator()(int i) {
+    return select<1, 0>(i);
+  }
+
   // TODO ESIMD_EXPERIMENTAL
   /// Read multiple elements by their indices in vector
   template <int Size>

sycl/test/esimd/simd_subscript.cpp

@@ -63,13 +63,21 @@ void test_simd_writable_subscript() SYCL_ESIMD_FUNCTION {
   simd<int, 4> v = 1;
   int val1 = v[0]; // simd_view -> int
   v[1] = 0;        // returns simd_view
+
+  // CHECK: simd_subscript.cpp:69{{.*}}warning: {{.*}} deprecated
+  // CHECK: sycl/ext/intel/experimental/esimd/simd.hpp:{{.*}} note: {{.*}} has been explicitly marked deprecated here
+  v(1) = 0;
 }
 
 void test_simd_const_subscript() SYCL_ESIMD_FUNCTION {
   const simd<int, 4> cv = 1;
   int val2 = cv[0]; // returns int instead of simd_view
-  // CHECK: simd_subscript.cpp:72{{.*}}error: expression is not assignable
+  // CHECK: simd_subscript.cpp:76{{.*}}error: expression is not assignable
   cv[1] = 0;
+
+  // CHECK: simd_subscript.cpp:80{{.*}}warning: {{.*}} deprecated
+  // CHECK: sycl/ext/intel/experimental/esimd/simd.hpp:{{.*}} note: {{.*}} has been explicitly marked deprecated here
+  int val3 = cv(0);
 }
 
 void test_simd_view_assign_op() SYCL_ESIMD_FUNCTION {

sycl/test/esimd/simd_view.cpp

@@ -1,5 +1,4 @@
 // RUN: %clangxx -fsycl -fsycl-device-only -fsyntax-only -Xclang -verify %s
-// expected-no-diagnostics
 
 #include <sycl/ext/intel/experimental/esimd.hpp>
 #include <limits>
@@ -62,3 +61,13 @@ bool test_simd_view_assign3() __attribute__((sycl_device)) {
       (g4.row(2) & mask2.bit_cast_view<ushort, 4, 16>().row(0));
   return val[0] == 0 && val1[0] == 0;
 }
+
+void test_simd_view_subscript() SYCL_ESIMD_FUNCTION {
+  simd<int, 4> v = 1;
+  auto vv = v.select<2, 1>(0);
+
+  int x = vv[1];
+  // expected-warning@+2 2 {{deprecated}}
+  // expected-note@sycl/ext/intel/experimental/esimd/detail/simd_view_impl.hpp:* 2 {{has been explicitly marked deprecated here}}
+  int y = vv(1);
+}