[SYCL] Fix over-allocation in spec consts (#8546)

This commit fixes an issue where specialization constants would
over-allocate memory. To avoid this causing errors this commit also
fixes an issue where setting specialization constants would prepend the
new value to the previous one.

Signed-off-by: Larsen, Steffen <[email protected]>

Author: steffenlarsen

sycl/include/sycl/kernel_bundle.hpp

@@ -315,8 +315,7 @@ class kernel_bundle : public detail::kernel_bundle_plain,
     using SCType =
         typename std::remove_reference_t<decltype(SpecName)>::value_type;
 
-    std::array<char *, sizeof(SCType)> RetValue;
-
+    std::array<char, sizeof(SCType)> RetValue;
     get_specialization_constant_impl(SpecSymName, RetValue.data());
 
     return *reinterpret_cast<SCType *>(RetValue.data());

sycl/source/detail/kernel_bundle_impl.hpp

@@ -425,10 +425,9 @@ class kernel_bundle_impl {
         getSyclObjImpl(DeviceImage)
             ->set_specialization_constant_raw_value(SpecName, Value);
     else {
-      const auto *DataPtr = static_cast<const unsigned char *>(Value);
       std::vector<unsigned char> &Val = MSpecConstValues[std::string{SpecName}];
       Val.resize(Size);
-      Val.insert(Val.begin(), DataPtr, DataPtr + Size);
+      std::memcpy(Val.data(), Value, Size);
     }
   }