[ESIMD] Allow constructing simd_view from simd (#4514)

* [ESIMD] Allow constructing simd_view from simd

The patch allows the following code to work:
```
  simd<int, 16> s = 0;
  simd_view v = s;
```

I added default template parameter for simd_view_impl class
and put it as a last template argument.

Signed-off-by: Vyacheslav N Klochkov <[email protected]>
Co-authored-by: kbobrovs <[email protected]>
Co-authored-by: DenisBakhvalov <[email protected]>

Author: DenisBakhvalov

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

@@ -25,7 +25,10 @@ namespace detail {
 /// It is an internal class implementing basic functionality of simd_view.
 ///
 /// \ingroup sycl_esimd
-template <typename BaseTy, typename RegionTy> class simd_view_impl {
+template <typename BaseTy,
+          typename RegionTy =
+              region1d_t<typename BaseTy::element_type, BaseTy::length, 1>>
+class simd_view_impl {
   using Derived = simd_view<BaseTy, RegionTy>;
   template <typename, int, class, class> friend class simd_obj_impl;
   template <typename, int> friend class simd;
@@ -65,6 +68,8 @@ template <typename BaseTy, typename RegionTy> class simd_view_impl {
       : M_base(Base), M_region(Region) {}
   simd_view_impl(BaseTy &&Base, RegionTy Region)
       : M_base(Base), M_region(Region) {}
+
+  simd_view_impl(BaseTy &Base) : M_base(Base), M_region(RegionTy(0)) {}
   /// @}
 public:
   // Default copy and move constructors.

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

@@ -25,7 +25,9 @@ namespace esimd {
 /// via an instance of this class.
 ///
 /// \ingroup sycl_esimd
-template <typename BaseTy, typename RegionTy>
+template <typename BaseTy,
+          typename RegionTy =
+              region1d_t<typename BaseTy::element_type, BaseTy::length, 1>>
 class simd_view : public detail::simd_view_impl<BaseTy, RegionTy> {
   template <typename, int, class, class> friend class detail::simd_obj_impl;
   template <typename, int> friend class detail::simd_mask_impl;
@@ -66,10 +68,13 @@ class simd_view : public detail::simd_view_impl<BaseTy, RegionTy> {
   /// @}
 
 public:
-  // Default copy and move constructors for simd_view.
+  /// Default copy and move constructors for simd_view.
   simd_view(const simd_view &Other) = default;
   simd_view(simd_view &&Other) = default;
 
+  /// Construct a complete view of a vector
+  simd_view(BaseTy &Base) : BaseClass(Base) {}
+
   simd_view &operator=(const simd_view &Other) {
     BaseClass::operator=(Other);
     return *this;
@@ -137,6 +142,9 @@ class simd_view<BaseTy, region1d_scalar_t<T>>
   simd_view(BaseTy &&Base, RegionTy Region) : BaseClass(Base, Region) {}
 
 public:
+  /// Construct a complete view of a vector
+  simd_view(BaseTy &Base) : BaseClass(Base) {}
+
   operator element_type() const {
     const auto v = BaseClass::read();
     return v[0];

sycl/test/esimd/simd_view.cpp

@@ -106,6 +106,24 @@ SYCL_ESIMD_FUNCTION void test_simd_view_copy_ctor() {
   auto v0_view_copy(v0_view);
 }
 
+// test construction from vector.
+SYCL_ESIMD_FUNCTION void test_simd_view_from_vector() {
+  simd<int, 16> v16 = 0;
+  simd_view sv16a = v16;
+  simd_view sv16b(v16);
+  // expected-error@+5 {{no matching constructor for initialization of 'simd_view}}
+  // expected-note@sycl/ext/intel/experimental/esimd/simd_view.hpp:* 3 {{candidate }}
+  // expected-note@sycl/ext/intel/experimental/esimd/simd.hpp:* {{candidate }}
+  // expected-note@sycl/ext/intel/experimental/esimd/detail/simd_obj_impl.hpp:* {{candidate }}
+  // expected-note@sycl/ext/intel/experimental/esimd/simd_view.hpp:* 2 {{candidate }}
+  simd_view<simd<int, 16>, region_base<false, int, 1, 1, 16, 1>> sv16c(
+      (simd<int, 16>()));
+
+  simd<int, 1> v1 = 0;
+  simd_view sv1a = v1;
+  simd_view sv1b(v1);
+}
+
 // move constructor transfers the same view of the underlying data.
 SYCL_ESIMD_FUNCTION void test_simd_view_move_ctor() {
   simd<int, 16> v0 = 1;