shader: Store type of phi nodes in flags

This is needed because pseudo-instructions where invalidated.

src/shader_recompiler/backend/spirv/emit_spirv.cpp

@@ -288,7 +288,8 @@ Id EmitPhi(EmitContext& ctx, IR::Inst* inst) {
         operands.push_back(PhiArgDef(ctx, inst, index));
         operands.push_back(inst->PhiBlock(index)->Definition<Id>());
     }
-    const Id result_type{TypeId(ctx, inst->Arg(0).Type())};
+    // The type of a phi instruction is stored in its flags
+    const Id result_type{TypeId(ctx, inst->Flags<IR::Type>())};
     return ctx.OpPhi(result_type, std::span(operands.data(), operands.size()));
 }
 

src/shader_recompiler/frontend/ir/microinstruction.cpp

@@ -193,6 +193,10 @@ void Inst::AddPhiOperand(Block* predecessor, const Value& value) {
     if (!value.IsImmediate()) {
         Use(value);
     }
+    if (Flags<IR::Type>() == IR::Type::Void) {
+        // Set the type of the phi node
+        SetFlags<IR::Type>(value.Type());
+    }
     phi_args.emplace_back(predecessor, value);
 }
 

src/shader_recompiler/frontend/ir/value.cpp

@@ -56,7 +56,11 @@ bool Value::IsLabel() const noexcept {
 }
 
 IR::Type Value::Type() const noexcept {
-    if (IsIdentity() || IsPhi()) {
+    if (IsPhi()) {
+        // The type of a phi node is stored in its flags
+        return inst->Flags<IR::Type>();
+    }
+    if (IsIdentity()) {
         return inst->Arg(0).Type();
     }
     if (type == Type::Opaque) {