ssa_rewrite: Recursively remove phis

src/shader_recompiler/ir/ir_emitter.h

@@ -330,6 +330,7 @@ private:
     template <typename T = Value, typename... Args>
     T Inst(Opcode op, Args... args) {
         auto it{block->PrependNewInst(insertion_point, op, {Value{args}...})};
+        it->SetParent(block);
         return T{Value{&*it}};
     }
 
@@ -347,6 +348,7 @@ private:
         u32 raw_flags{};
         std::memcpy(&raw_flags, &flags.proxy, sizeof(flags.proxy));
         auto it{block->PrependNewInst(insertion_point, op, {Value{args}...}, raw_flags)};
+        it->SetParent(block);
         return T{Value{&*it}};
     }
 };

src/shader_recompiler/ir/microinstruction.cpp

@@ -150,7 +150,6 @@ void Inst::AddPhiOperand(Block* predecessor, const Value& value) {
 }
 
 void Inst::Invalidate() {
-    ASSERT(uses.empty());
     ClearArgs();
     ReplaceOpcode(Opcode::Void);
 }

src/shader_recompiler/ir/passes/ssa_rewrite_pass.cpp

@@ -164,7 +164,6 @@ IR::Opcode UndefOpcode(const FlagTag) noexcept {
 enum class Status {
     Start,
     SetValue,
-    PreparePhiArgument,
     PushPhiArgument,
 };
 
@@ -253,12 +252,10 @@ public:
                 IR::Inst* const phi{stack.back().phi};
                 phi->AddPhiOperand(*stack.back().pred_it, stack.back().result);
                 ++stack.back().pred_it;
-            }
-                [[fallthrough]];
-            case Status::PreparePhiArgument:
                 prepare_phi_operand();
                 break;
             }
+            }
         } while (stack.size() > 1);
         return stack.back().result;
     }
@@ -266,16 +263,13 @@ public:
     void SealBlock(IR::Block* block) {
         const auto it{incomplete_phis.find(block)};
         if (it != incomplete_phis.end()) {
-            for (auto& pair : it->second) {
-                auto& variant{pair.first};
-                auto& phi{pair.second};
+            for (auto& [variant, phi] : it->second) {
                 std::visit([&](auto& variable) { AddPhiOperands(variable, *phi, block); }, variant);
             }
         }
         block->SsaSeal();
     }
 
-private:
     template <typename Type>
     IR::Value AddPhiOperands(Type variable, IR::Inst& phi, IR::Block* block) {
         for (IR::Block* const imm_pred : block->ImmPredecessors()) {
@@ -317,6 +311,12 @@ private:
         list.insert(reinsert_point, phi);
         phi.ReplaceUsesWith(same);
         // TODO: Try to recursively remove all phi users, which might have become trivial
+        const auto users = phi.Uses();
+        for (const auto& [user, arg_index] : users) {
+            if (user->GetOpcode() == IR::Opcode::Phi) {
+                TryRemoveTrivialPhi(*user, user->GetParent(), undef_opcode);
+            }
+        }
         return same;
     }
 

src/shader_recompiler/ir/value.h

@@ -129,6 +129,14 @@ public:
     Inst& operator=(Inst&&) = delete;
     Inst(Inst&&) = delete;
 
+    IR::Block* GetParent() {
+        ASSERT(parent);
+        return parent;
+    }
+    void SetParent(IR::Block* block) {
+        parent = block;
+    }
+
     /// Get the number of uses this instruction has.
     [[nodiscard]] int UseCount() const noexcept {
         return uses.size();
@@ -214,6 +222,10 @@ public:
         return std::bit_cast<DefinitionType>(definition);
     }
 
+    const auto Uses() const {
+        return uses;
+    }
+
 private:
     struct NonTriviallyDummy {
         NonTriviallyDummy() noexcept {}
@@ -226,6 +238,7 @@ private:
     IR::Opcode op{};
     u32 flags{};
     u32 definition{};
+    IR::Block* parent{};
     union {
         NonTriviallyDummy dummy{};
         boost::container::small_vector<std::pair<Block*, Value>, 2> phi_args;
@@ -234,7 +247,7 @@ private:
 
     boost::container::list<IR::Use> uses;
 };
-static_assert(sizeof(Inst) <= 152, "Inst size unintentionally increased");
+static_assert(sizeof(Inst) <= 160, "Inst size unintentionally increased");
 
 using U1 = TypedValue<Type::U1>;
 using U8 = TypedValue<Type::U8>;
@@ -392,4 +405,4 @@ template <>
 struct hash<Shader::IR::Value> {
     std::size_t operator()(const Shader::IR::Value& v) const;
 };
-} // namespace std
+} // namespace std