[SYCL] Add support for _Float16 type mangling to OclCxxRewrite

Half type is defined on SYCL device as _Float16. This type is mangled by
clang as "DF16_". OclCxxRewrite doesn't support this mangling and skips
all OpenCL built-ins with _Float16 type. So these built-ins are not
translated properly to SPIRV without this change.

Signed-off-by: Mariya Podchishchaeva <mariya.podchishchaeva@intel.com>

Author: Fznamznon

clang/lib/CodeGen/OclCxxRewrite/OclCxxDemangler.cpp

@@ -353,6 +353,8 @@ static bool matchFixedBiTypeAndAdvance(const std::string &ParsedText,
       break;
     case 'n': MatchedType = DBT_NullPtr;
       break;
+    case 'F': MatchedType = DBT_Half; Pos += 3; // _Float16 -> DF16_
+      break;
     default:
       return false;
     }

clang/lib/CodeGen/OclCxxRewrite/OclCxxMangleEncodings.inc

@@ -115,7 +115,7 @@ OCLCXX_MENC_BITYPE_FIXED(Float128R,    "De", "__fp128r")
                              ///< IEEE 754r decimal floating point (128 bits)
 OCLCXX_MENC_BITYPE_FIXED(Float32R,     "Df", "__fp32r")
                              ///< IEEE 754r decimal floating point (32 bits)
-OCLCXX_MENC_BITYPE_FIXED(Float16R,     "Dh", "half")
+OCLCXX_MENC_BITYPE_FIXED(Float16R,     "DF16_", "_Float16")
                              ///< IEEE 754r half-prec floating point (16 bits)
 OCLCXX_MENC_BITYPE_ALIAS(Half,         Float16R)
 OCLCXX_MENC_BITYPE_FIXED(Char32,       "Di", "char32_t")       ///< char32_t