Use entry point interface ID list if available over building our own

renderdoc/driver/shaders/spirv/spirv_processor.cpp

@@ -524,7 +524,8 @@ void Processor::RegisterOp(Iter it)
   else if(opdata.op == Op::EntryPoint)
   {
     OpEntryPoint decoded(it);
-    entries.push_back(EntryPoint(decoded.executionModel, decoded.entryPoint, decoded.name));
+    entries.push_back(
+        EntryPoint(decoded.executionModel, decoded.entryPoint, decoded.name, decoded.iface));
   }
   else if(opdata.op == Op::ExecutionMode)
   {

renderdoc/driver/shaders/spirv/spirv_processor.h

@@ -418,11 +418,15 @@ struct ExecutionModes
 struct EntryPoint
 {
   EntryPoint() = default;
-  EntryPoint(ExecutionModel e, Id i, rdcstr n) : executionModel(e), id(i), name(n) {}
+  EntryPoint(ExecutionModel e, Id i, rdcstr n, const rdcarray<Id> &ids)
+      : executionModel(e), id(i), name(n), usedIds(ids)
+  {
+  }
   ExecutionModel executionModel;
   Id id;
   rdcstr name;
   ExecutionModes executionModes;
+  rdcarray<Id> usedIds;
 
   bool operator<(const EntryPoint &o) const
   {

renderdoc/driver/shaders/spirv/spirv_reflect.cpp

@@ -737,6 +737,15 @@ void Reflector::MakeReflection(const GraphicsAPI sourceAPI, const ShaderStage st
     }
   }
 
+  if(m_MajorVersion > 1 || m_MinorVersion >= 4)
+  {
+    // from SPIR-V 1.4 onwards we can trust the entry point interface list to give us all used
+    // global variables. We still use the above heuristic so we can remove unused members of
+    // gl_PerVertex in structs.
+    usedIds.clear();
+    usedIds.insert(entry->usedIds.begin(), entry->usedIds.end());
+  }
+
   // arrays of elements, which can be appended to in any order and then sorted
   rdcarray<SigParameter> inputs;
   rdcarray<SigParameter> outputs;