clc: support fp16 spec constants

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34053>

src/compiler/clc/clc.h

@@ -175,6 +175,7 @@ struct clc_kernel_info {
 enum clc_spec_constant_type {
    CLC_SPEC_CONSTANT_UNKNOWN,
    CLC_SPEC_CONSTANT_BOOL,
+   CLC_SPEC_CONSTANT_HALF,
    CLC_SPEC_CONSTANT_FLOAT,
    CLC_SPEC_CONSTANT_DOUBLE,
    CLC_SPEC_CONSTANT_INT8,

src/compiler/clc/clc_helpers.cpp

@@ -527,7 +527,7 @@ public:
             literalType = CLC_SPEC_CONSTANT_DOUBLE;
             break;
          case 16:
-            /* Can't be used for a spec constant */
+            literalType = CLC_SPEC_CONSTANT_HALF;
             break;
          default:
             unreachable("Unexpected float bit size");
@@ -1373,6 +1373,7 @@ clc_spirv_specialize(const struct clc_binary *in_spirv,
       case CLC_SPEC_CONSTANT_INT8:
          words.push_back((uint32_t)(int32_t)consts->specializations[i].value.i8);
          break;
+      case CLC_SPEC_CONSTANT_HALF:
       case CLC_SPEC_CONSTANT_UINT16:
          words.push_back((uint32_t)consts->specializations[i].value.u16);
          break;