[SYCL][ESIMD] Fix host compilation errors when sycl.hpp is not included. (#3838)

* [SYCL][ESIMD] Fix host compilation errors when sycl.hpp is not included.

Signed-off-by: kbobrovs <[email protected]>

Author: kbobrovs

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

@@ -12,6 +12,8 @@
 
 #ifndef __SYCL_DEVICE_ONLY__
 
+#include <limits>
+
 #define SIMDCF_ELEMENT_SKIP(i)
 
 __SYCL_INLINE_NAMESPACE(cl) {
@@ -33,6 +35,7 @@ namespace esimd {
 namespace emu {
 namespace detail {
 
+using half = sycl::detail::half_impl::half;
 constexpr int sat_is_on = 1;
 
 static long long abs(long long a) {

sycl/test/esimd/regression/esimd_hpp_wo_sycl_hpp_included.cpp

@@ -0,0 +1,7 @@
+// RUN: %clangxx -fsycl -fsyntax-only %s
+// expected-no-diagnostics
+
+#include <sycl/ext/intel/experimental/esimd.hpp>
+
+// This test checks that host compiler can compile esimd.hpp when there is no
+// sycl.hpp included (can happen in pure-ESIMD library).