shader: Implement MEMBAR

src/shader_recompiler/frontend/ir/modifiers.h

@@ -25,6 +25,14 @@ enum class FpRounding : u8 {
     RZ,       // Round towards zero
 };
 
+enum class MemoryScope : u32 {
+  DontCare,
+  Warp,
+  Workgroup,
+  Device,
+  System
+};
+
 struct FpControl {
     bool no_contraction{false};
     FpRounding rounding{FpRounding::DontCare};
@@ -32,6 +40,11 @@ struct FpControl {
 };
 static_assert(sizeof(FpControl) <= sizeof(u32));
 
+union BarrierInstInfo {
+    u32 raw;
+    BitField<0, 3, MemoryScope> scope;
+};
+
 union TextureInstInfo {
     u32 raw;
     BitField<0, 8, TextureType> type;