Use distinct nodes for clspv.next_spec_constant_id (#696)

Metadata nodes are uniqued by default, which means this counter was
sometimes being merged with other metadata values such as push
constant declarations. Subsequent updates to this counter would then
inadvertently change the type of the push constant.

lib/SpecConstant.cpp

diff --git a/lib/SpecConstant.cpp b/lib/SpecConstant.cpp
index 30b478a..a5ccc89 100644
--- a/lib/SpecConstant.cpp
+++ b/lib/SpecConstant.cpp
@@ -30,7 +30,7 @@
   const uint32_t first_spec_id = 3;
   auto id_const = ValueAsMetadata::getConstant(ConstantInt::get(
       IntegerType::get(module->getContext(), 32), first_spec_id));
-  auto id_md = MDTuple::get(module->getContext(), {id_const});
+  auto id_md = MDTuple::getDistinct(module->getContext(), {id_const});
   next_spec_id_md->addOperand(id_md);
 
   auto spec_constant_list_md =

test/Reflection/global_size_and_work_dim.cl

diff --git a/test/Reflection/global_size_and_work_dim.cl b/test/Reflection/global_size_and_work_dim.cl
new file mode 100644
index 0000000..8f7be2d
--- /dev/null
+++ b/test/Reflection/global_size_and_work_dim.cl
@@ -0,0 +1,19 @@
+// RUN: clspv %s -o %t.spv -cl-std=CL2.0 -inline-entry-points
+// RUN: spirv-dis %t.spv -o %t.spvasm
+// RUN: FileCheck %s < %t.spvasm
+// RUN: spirv-val --target-env vulkan1.0 %t.spv
+
+kernel void foo(global int* data) {
+  *data = get_global_size(0) + get_work_dim();
+}
+
+// CHECK: [[import:%[a-zA-Z0-9_]+]] = OpExtInstImport "NonSemantic.ClspvReflection.1"
+// CHECK: OpEntryPoint GLCompute [[foo:%[a-zA-Z0-9_]+]] "foo"
+// CHECK-DAG: [[void:%[a-zA-Z0-9_]+]] = OpTypeVoid
+// CHECK-DAG: [[uint:%[a-zA-Z0-9_]+]] = OpTypeInt 32 0
+// CHECK-DAG: [[uint_0:%[a-zA-Z0-9_]+]] = OpConstant [[uint]] 0
+// CHECK-DAG: [[uint_12:%[a-zA-Z0-9_]+]] = OpConstant [[uint]] 12
+// CHECK-DAG: [[uint_3:%[a-zA-Z0-9_]+]] = OpConstant [[uint]] 3
+//
+// CHECK-DAG: OpExtInst [[void]] [[import]] PushConstantGlobalSize [[uint_0]] [[uint_12]]
+// CHECK: OpExtInst [[void]] [[import]] SpecConstantWorkDim [[uint_3]]