diff --git a/include/luisa/luisa-compute.h b/include/luisa/luisa-compute.h
index 879be3258..91b7054e4 100644
--- a/include/luisa/luisa-compute.h
+++ b/include/luisa/luisa-compute.h
@@ -212,6 +212,7 @@
 #include <luisa/xir/instructions/break.h>
 #include <luisa/xir/instructions/call.h>
 #include <luisa/xir/instructions/cast.h>
+#include <luisa/xir/instructions/clock.h>
 #include <luisa/xir/instructions/continue.h>
 #include <luisa/xir/instructions/gep.h>
 #include <luisa/xir/instructions/if.h>
diff --git a/include/luisa/xir/builder.h b/include/luisa/xir/builder.h
index bb806f246..5b65180b5 100644
--- a/include/luisa/xir/builder.h
+++ b/include/luisa/xir/builder.h
@@ -2,7 +2,6 @@
 
 #include <luisa/ast/type_registry.h>
 #include <luisa/xir/constant.h>
-#include <luisa/xir/special_register.h>
 #include <luisa/xir/instructions/alloca.h>
 #include <luisa/xir/instructions/assert.h>
 #include <luisa/xir/instructions/assume.h>
@@ -10,6 +9,7 @@
 #include <luisa/xir/instructions/break.h>
 #include <luisa/xir/instructions/call.h>
 #include <luisa/xir/instructions/cast.h>
+#include <luisa/xir/instructions/clock.h>
 #include <luisa/xir/instructions/continue.h>
 #include <luisa/xir/instructions/gep.h>
 #include <luisa/xir/instructions/if.h>
@@ -25,6 +25,9 @@
 #include <luisa/xir/instructions/switch.h>
 #include <luisa/xir/instructions/unreachable.h>
 
+namespace luisa::compute::xir {
+class ClockInst;
+}// namespace luisa::compute::xir
 namespace luisa::compute::xir {
 
 class LC_XIR_API Builder {
@@ -101,6 +104,8 @@ class LC_XIR_API Builder {
     LoadInst *load(const Type *type, Value *variable) noexcept;
     StoreInst *store(Value *variable, Value *value) noexcept;
 
+    ClockInst *clock() noexcept;
+
     OutlineInst *outline() noexcept;
     RayQueryInst *ray_query(Value *query_object) noexcept;
 };
diff --git a/include/luisa/xir/instruction.h b/include/luisa/xir/instruction.h
index b528752fd..28b068e1a 100644
--- a/include/luisa/xir/instruction.h
+++ b/include/luisa/xir/instruction.h
@@ -1,5 +1,7 @@
 #pragma once
 
+#include "instruction.h"
+
 #include <luisa/xir/user.h>
 
 namespace luisa::compute::xir {
@@ -24,17 +26,31 @@ enum struct DerivedInstructionTag {
     RETURN,            // basic block terminator: return (early returns are removed after control flow normalization)
     PHI,               // basic block beginning: phi nodes
 
-    // variable instructions
+    /* variable instructions */
     ALLOCA,
     LOAD,
     STORE,
     GEP,
 
+    /* atomic instructions */
+    ATOMIC,// operates on buffers / shared memory
+
+    /* ALU (arithmetic logic unit) instructions */
+    ALU,// all are pure functions, free to move/eliminate
+
+    /* CTA (cooperative thread array) instructions */
+    CTA,// volatile, may involve synchronization and cannot be moved/eliminated
+
+    /* resource instructions */
+    RESOURCE,
+
     /* other instructions */
-    CALL,     // user or external function calls
+    CALL, // user or external function calls
+    CAST, // type casts
+    PRINT,// kernel print
+    CLOCK,// kernel clock
+
     INTRINSIC,// intrinsic function calls
-    CAST,     // type casts
-    PRINT,    // kernel print
 
     ASSERT,// assertion
     ASSUME,// assumption
@@ -44,6 +60,8 @@ enum struct DerivedInstructionTag {
     RAY_QUERY,// ray queries
 };
 
+class ControlFlowMerge;
+
 class LC_XIR_API Instruction : public IntrusiveNode<Instruction, DerivedValue<DerivedValueTag::INSTRUCTION, User>> {
 
 private:
@@ -70,6 +88,9 @@ class LC_XIR_API Instruction : public IntrusiveNode<Instruction, DerivedValue<De
     [[nodiscard]] virtual bool is_terminator() const noexcept { return false; }
     [[nodiscard]] BasicBlock *parent_block() noexcept { return _parent_block; }
     [[nodiscard]] const BasicBlock *parent_block() const noexcept { return _parent_block; }
+
+    [[nodiscard]] virtual ControlFlowMerge *control_flow_merge() noexcept { return nullptr; }
+    [[nodiscard]] const ControlFlowMerge *control_flow_merge() const noexcept;
 };
 
 using InstructionList = InlineIntrusiveList<Instruction>;
@@ -158,14 +179,14 @@ class DerivedConditionalBranchInstruction : public DerivedInstruction<tag, Condi
     using DerivedInstruction<tag, ConditionalBranchTerminatorInstruction>::DerivedInstruction;
 };
 
-class LC_XIR_API InstructionMergeMixin {
+class LC_XIR_API ControlFlowMerge {
 
 private:
     BasicBlock *_merge_block{nullptr};
 
 protected:
-    InstructionMergeMixin() noexcept = default;
-    ~InstructionMergeMixin() noexcept = default;
+    ControlFlowMerge() noexcept = default;
+    ~ControlFlowMerge() noexcept = default;
 
 public:
     void set_merge_block(BasicBlock *block) noexcept { _merge_block = block; }
@@ -174,4 +195,15 @@ class LC_XIR_API InstructionMergeMixin {
     BasicBlock *create_merge_block(bool overwrite_existing = false) noexcept;
 };
 
+template<typename Base>
+    requires std::derived_from<Base, Instruction>
+class ControlFlowMergeMixin : public Base,
+                              public ControlFlowMerge {
+public:
+    using Base::Base;
+    [[nodiscard]] ControlFlowMerge *control_flow_merge() noexcept final {
+        return static_cast<ControlFlowMerge *>(this);
+    }
+};
+
 }// namespace luisa::compute::xir
diff --git a/include/luisa/xir/instructions/clock.h b/include/luisa/xir/instructions/clock.h
new file mode 100644
index 000000000..b44588d66
--- /dev/null
+++ b/include/luisa/xir/instructions/clock.h
@@ -0,0 +1,12 @@
+#pragma once
+
+#include <luisa/xir/instruction.h>
+
+namespace luisa::compute::xir {
+
+class LC_XIR_API ClockInst : public DerivedInstruction<DerivedInstructionTag::CLOCK> {
+public:
+    ClockInst() noexcept;
+};
+
+}// namespace luisa::compute::xir
diff --git a/include/luisa/xir/instructions/if.h b/include/luisa/xir/instructions/if.h
index 8fd9bf10f..8a81446e4 100644
--- a/include/luisa/xir/instructions/if.h
+++ b/include/luisa/xir/instructions/if.h
@@ -16,10 +16,9 @@ class BasicBlock;
 // { merge_block }
 //
 // Note: this instruction must be the terminator of a basic block.
-class IfInst final : public DerivedConditionalBranchInstruction<DerivedInstructionTag::IF>,
-                     public InstructionMergeMixin {
+class IfInst final : public ControlFlowMergeMixin<DerivedConditionalBranchInstruction<DerivedInstructionTag::IF>> {
 public:
-    using DerivedConditionalBranchInstruction::DerivedConditionalBranchInstruction;
+    using ControlFlowMergeMixin::ControlFlowMergeMixin;
 };
 
 }// namespace luisa::compute::xir
diff --git a/include/luisa/xir/instructions/intrinsic.h b/include/luisa/xir/instructions/intrinsic.h
index b998fbe3b..558c1bef6 100644
--- a/include/luisa/xir/instructions/intrinsic.h
+++ b/include/luisa/xir/instructions/intrinsic.h
@@ -294,9 +294,6 @@ enum struct IntrinsicOp {
 
     // shader execution re-ordering
     SHADER_EXECUTION_REORDER,// (uint hint, uint hint_bits): void
-
-    // clock
-    CLOCK,// (): uint64
 };
 
 [[nodiscard]] LC_XIR_API luisa::string to_string(IntrinsicOp op) noexcept;
diff --git a/include/luisa/xir/instructions/loop.h b/include/luisa/xir/instructions/loop.h
index a2d820c26..b1209de7e 100644
--- a/include/luisa/xir/instructions/loop.h
+++ b/include/luisa/xir/instructions/loop.h
@@ -5,8 +5,7 @@
 namespace luisa::compute::xir {
 
 // Note: this instruction must be the terminator of a basic block.
-class LC_XIR_API LoopInst final : public DerivedTerminatorInstruction<DerivedInstructionTag::LOOP>,
-                                  public InstructionMergeMixin {
+class LC_XIR_API LoopInst final : public ControlFlowMergeMixin<DerivedTerminatorInstruction<DerivedInstructionTag::LOOP>> {
 
 public:
     static constexpr size_t operand_index_prepare_block = 0u;
@@ -36,8 +35,7 @@ class LC_XIR_API LoopInst final : public DerivedTerminatorInstruction<DerivedIns
     [[nodiscard]] const BasicBlock *update_block() const noexcept;
 };
 
-class LC_XIR_API SimpleLoopInst final : public DerivedTerminatorInstruction<DerivedInstructionTag::SIMPLE_LOOP>,
-                                        public InstructionMergeMixin {
+class LC_XIR_API SimpleLoopInst final : public ControlFlowMergeMixin<DerivedTerminatorInstruction<DerivedInstructionTag::SIMPLE_LOOP>> {
 public:
     static constexpr size_t operand_index_body_block = 0u;
 
diff --git a/include/luisa/xir/instructions/outline.h b/include/luisa/xir/instructions/outline.h
index 920eae741..69d3a1a7a 100644
--- a/include/luisa/xir/instructions/outline.h
+++ b/include/luisa/xir/instructions/outline.h
@@ -6,10 +6,9 @@ namespace luisa::compute::xir {
 
 class BasicBlock;
 
-class OutlineInst final : public DerivedBranchInstruction<DerivedInstructionTag::OUTLINE>,
-                          public InstructionMergeMixin {
+class OutlineInst final : public ControlFlowMergeMixin<DerivedBranchInstruction<DerivedInstructionTag::OUTLINE>> {
 public:
-    using DerivedBranchInstruction::DerivedBranchInstruction;
+    using ControlFlowMergeMixin::ControlFlowMergeMixin;
 };
 
 }// namespace luisa::compute::xir
diff --git a/include/luisa/xir/instructions/ray_query.h b/include/luisa/xir/instructions/ray_query.h
index f8438f2e0..b4050cd39 100644
--- a/include/luisa/xir/instructions/ray_query.h
+++ b/include/luisa/xir/instructions/ray_query.h
@@ -4,8 +4,7 @@
 
 namespace luisa::compute::xir {
 
-class LC_XIR_API RayQueryInst final : public DerivedTerminatorInstruction<DerivedInstructionTag::RAY_QUERY>,
-                                      public InstructionMergeMixin {
+class LC_XIR_API RayQueryInst final : public ControlFlowMergeMixin<DerivedTerminatorInstruction<DerivedInstructionTag::RAY_QUERY>> {
 
 public:
     static constexpr size_t operand_index_query_object = 0u;
diff --git a/include/luisa/xir/instructions/switch.h b/include/luisa/xir/instructions/switch.h
index 8f47a8631..f8c830a56 100644
--- a/include/luisa/xir/instructions/switch.h
+++ b/include/luisa/xir/instructions/switch.h
@@ -15,8 +15,7 @@ namespace luisa::compute::xir {
 // { merge_block }
 //
 // Note: this instruction must be the terminator of a basic block.
-class LC_XIR_API SwitchInst final : public DerivedTerminatorInstruction<DerivedInstructionTag::SWITCH>,
-                                    public InstructionMergeMixin {
+class LC_XIR_API SwitchInst final : public ControlFlowMergeMixin<DerivedTerminatorInstruction<DerivedInstructionTag::SWITCH>> {
 
 public:
     using case_value_type = int;
diff --git a/src/backends/fallback/fallback_codegen.cpp b/src/backends/fallback/fallback_codegen.cpp
index e197a2075..a6023088c 100644
--- a/src/backends/fallback/fallback_codegen.cpp
+++ b/src/backends/fallback/fallback_codegen.cpp
@@ -21,6 +21,7 @@
 #include <luisa/runtime/rtx/hit.h>
 #include <luisa/xir/module.h>
 #include <luisa/xir/builder.h>
+#include <luisa/xir/special_register.h>
 #include <luisa/xir/metadata/name.h>
 #include <luisa/xir/metadata/location.h>
 
@@ -2535,11 +2536,6 @@ class FallbackCodegen {
             case xir::IntrinsicOp::INDIRECT_DISPATCH_SET_KERNEL: break;
             case xir::IntrinsicOp::INDIRECT_DISPATCH_SET_COUNT: break;
             case xir::IntrinsicOp::SHADER_EXECUTION_REORDER: return nullptr;// no-op on the LLVM side
-            case xir::IntrinsicOp::CLOCK: {
-                auto call = b.CreateIntrinsic(llvm::Intrinsic::readcyclecounter, {}, {});
-                auto llvm_result_type = _translate_type(inst->type(), true);
-                return b.CreateZExtOrTrunc(call, llvm_result_type);
-            }
         }
         LUISA_INFO("unsupported intrinsic op type: {}", static_cast<int>(inst->op()));
         LUISA_NOT_IMPLEMENTED();
@@ -2872,6 +2868,14 @@ class FallbackCodegen {
             }
             case xir::DerivedInstructionTag::AUTO_DIFF: LUISA_NOT_IMPLEMENTED();
             case xir::DerivedInstructionTag::RAY_QUERY: LUISA_NOT_IMPLEMENTED();
+            case xir::DerivedInstructionTag::CLOCK: {
+                auto call = b.CreateIntrinsic(llvm::Intrinsic::readcyclecounter, {}, {});
+                auto llvm_result_type = _translate_type(inst->type(), true);
+                return b.CreateZExtOrTrunc(call, llvm_result_type);
+            }
+            case xir::DerivedInstructionTag::ALU: break;
+            case xir::DerivedInstructionTag::CTA: break;
+            case xir::DerivedInstructionTag::RESOURCE: break;
         }
         LUISA_ERROR_WITH_LOCATION("Invalid instruction.");
     }
diff --git a/src/xir/CMakeLists.txt b/src/xir/CMakeLists.txt
index 8a3fb691f..89d51dde2 100644
--- a/src/xir/CMakeLists.txt
+++ b/src/xir/CMakeLists.txt
@@ -20,6 +20,7 @@ set(LUISA_COMPUTE_XIR_SOURCES
         instructions/assume.cpp
         instructions/call.cpp
         instructions/cast.cpp
+        instructions/clock.cpp
         instructions/gep.cpp
         instructions/intrinsic.cpp
         instructions/load.cpp
diff --git a/src/xir/builder.cpp b/src/xir/builder.cpp
index 5118dac07..b6bfc9b64 100644
--- a/src/xir/builder.cpp
+++ b/src/xir/builder.cpp
@@ -149,17 +149,21 @@ GEPInst *Builder::gep(const Type *type, Value *base, luisa::span<Value *const> i
 
 LoadInst *Builder::load(const Type *type, Value *variable) noexcept {
     LUISA_ASSERT(variable->is_lvalue(), "Load source must be an lvalue.");
-	LUISA_ASSERT(type == variable->type(), "Type mismatch in Load");
+    LUISA_ASSERT(type == variable->type(), "Type mismatch in Load");
     return _create_and_append_instruction<LoadInst>(type, variable);
 }
 
 StoreInst *Builder::store(Value *variable, Value *value) noexcept {
     LUISA_ASSERT(variable->is_lvalue(), "Store destination must be an lvalue.");
     LUISA_ASSERT(!value->is_lvalue(), "Store source cannot be an lvalue.");
-	LUISA_ASSERT(variable->type() == value->type(), "Type mismatch in Store");
+    LUISA_ASSERT(variable->type() == value->type(), "Type mismatch in Store");
     return _create_and_append_instruction<StoreInst>(variable, value);
 }
 
+ClockInst *Builder::clock() noexcept {
+    return _create_and_append_instruction<ClockInst>();
+}
+
 OutlineInst *Builder::outline() noexcept {
     return _create_and_append_instruction<OutlineInst>();
 }
diff --git a/src/xir/instruction.cpp b/src/xir/instruction.cpp
index 3e167fbf7..6f268ec3a 100644
--- a/src/xir/instruction.cpp
+++ b/src/xir/instruction.cpp
@@ -55,6 +55,10 @@ void Instruction::replace_self_with(Instruction *node) noexcept {
     remove_self();
 }
 
+const ControlFlowMerge *Instruction::control_flow_merge() const noexcept {
+    return const_cast<Instruction *>(this)->control_flow_merge();
+}
+
 TerminatorInstruction::TerminatorInstruction() noexcept
     : Instruction{nullptr} {}
 
@@ -141,7 +145,7 @@ const BasicBlock *ConditionalBranchTerminatorInstruction::false_block() const no
     return const_cast<ConditionalBranchTerminatorInstruction *>(this)->false_block();
 }
 
-BasicBlock *InstructionMergeMixin::create_merge_block(bool overwrite_existing) noexcept {
+BasicBlock *ControlFlowMerge::create_merge_block(bool overwrite_existing) noexcept {
     LUISA_ASSERT(merge_block() == nullptr || overwrite_existing,
                  "Merge block already exists.");
     auto block = Pool::current()->create<BasicBlock>();
diff --git a/src/xir/instructions/clock.cpp b/src/xir/instructions/clock.cpp
new file mode 100644
index 000000000..a04bc1168
--- /dev/null
+++ b/src/xir/instructions/clock.cpp
@@ -0,0 +1,9 @@
+#include <luisa/ast/type_registry.h>
+#include <luisa/xir/instructions/clock.h>
+
+namespace luisa::compute::xir {
+
+ClockInst::ClockInst() noexcept
+    : DerivedInstruction{Type::of<luisa::ulong>()} {}
+
+}// namespace luisa::compute::xir
diff --git a/src/xir/instructions/intrinsic_name_map.inl.h b/src/xir/instructions/intrinsic_name_map.inl.h
index ade9b758f..9198e68bc 100644
--- a/src/xir/instructions/intrinsic_name_map.inl.h
+++ b/src/xir/instructions/intrinsic_name_map.inl.h
@@ -224,7 +224,6 @@ luisa::string to_string(IntrinsicOp op) noexcept {
         case IntrinsicOp::INDIRECT_DISPATCH_SET_KERNEL: return "indirect_dispatch_set_kernel";
         case IntrinsicOp::INDIRECT_DISPATCH_SET_COUNT: return "indirect_dispatch_set_count";
         case IntrinsicOp::SHADER_EXECUTION_REORDER: return "shader_execution_reorder";
-        case IntrinsicOp::CLOCK: return "clock";
     }
     LUISA_ERROR_WITH_LOCATION("Unknown intrinsic operation: {}.",
                               static_cast<uint32_t>(op));
@@ -454,7 +453,6 @@ IntrinsicOp intrinsic_op_from_string(luisa::string_view name) noexcept {
         {"indirect_dispatch_set_kernel", IntrinsicOp::INDIRECT_DISPATCH_SET_KERNEL},
         {"indirect_dispatch_set_count", IntrinsicOp::INDIRECT_DISPATCH_SET_COUNT},
         {"shader_execution_reorder", IntrinsicOp::SHADER_EXECUTION_REORDER},
-        {"clock", IntrinsicOp::CLOCK},
     };
     auto iter = m.find(name);
     LUISA_ASSERT(iter != m.end(), "Unknown intrinsic operation: {}.", name);
diff --git a/src/xir/translators/ast2xir.cpp b/src/xir/translators/ast2xir.cpp
index 0117ef5cd..08c788baa 100644
--- a/src/xir/translators/ast2xir.cpp
+++ b/src/xir/translators/ast2xir.cpp
@@ -5,6 +5,7 @@
 #include <luisa/ast/statement.h>
 #include <luisa/ast/function.h>
 #include <luisa/xir/builder.h>
+#include <luisa/xir/special_register.h>
 #include <luisa/xir/translators/ast2xir.h>
 
 namespace luisa::compute::xir {
@@ -709,7 +710,7 @@ class AST2XIRContext {
             case CallOp::TEXTURE3D_SAMPLE_GRAD: return resource_call(IntrinsicOp::TEXTURE3D_SAMPLE_GRAD);
             case CallOp::TEXTURE3D_SAMPLE_GRAD_LEVEL: return resource_call(IntrinsicOp::TEXTURE3D_SAMPLE_GRAD_LEVEL);
             case CallOp::SHADER_EXECUTION_REORDER: return resource_call(IntrinsicOp::SHADER_EXECUTION_REORDER);
-            case CallOp::CLOCK: return pure_call(IntrinsicOp::CLOCK);
+            case CallOp::CLOCK: return b.clock();
         }
         LUISA_NOT_IMPLEMENTED();
     }
diff --git a/src/xir/translators/xir2text.cpp b/src/xir/translators/xir2text.cpp
index ff1250fe3..e91dcf77d 100644
--- a/src/xir/translators/xir2text.cpp
+++ b/src/xir/translators/xir2text.cpp
@@ -13,6 +13,7 @@
 #include <luisa/xir/instructions/break.h>
 #include <luisa/xir/instructions/call.h>
 #include <luisa/xir/instructions/cast.h>
+#include <luisa/xir/instructions/clock.h>
 #include <luisa/xir/instructions/continue.h>
 #include <luisa/xir/instructions/gep.h>
 #include <luisa/xir/instructions/intrinsic.h>
@@ -248,6 +249,10 @@ class XIR2TextTranslator final {
         _main << " " << _value_ident(inst->condition());
     }
 
+    void _emit_clock_inst(const ClockInst *inst [[maybe_unused]]) noexcept {
+        _main << "clock";
+    }
+
     void _emit_if_inst(const IfInst *inst, int indent) noexcept {
         _main << "if " << _value_ident(inst->condition()) << ", then ";
         _emit_basic_block(inst->true_block(), indent);
@@ -469,6 +474,12 @@ class XIR2TextTranslator final {
             case DerivedInstructionTag::ASSUME:
                 _emit_assume_inst(static_cast<const AssumeInst *>(inst));
                 break;
+            case DerivedInstructionTag::CLOCK:
+                _emit_clock_inst(static_cast<const ClockInst *>(inst));
+                break;
+            case DerivedInstructionTag::ALU: break;
+            case DerivedInstructionTag::CTA: break;
+            case DerivedInstructionTag::RESOURCE: break;
         }
         _main << ";";
         _emit_use_debug_info(_main, inst->use_list());