diff --git a/.vscode/settings.json b/.vscode/settings.json
index 3c989f58d..7a261015a 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -112,6 +112,8 @@
     "cfenv": "cpp",
     "csignal": "cpp",
     "__functional_base_03": "cpp",
-    "__memory": "cpp"
+    "__memory": "cpp",
+    "__bits": "cpp",
+    "__availability": "cpp"
   }
 }
diff --git a/rir/src/compiler/compiler.cpp b/rir/src/compiler/compiler.cpp
index 8d5bd04f1..c4fee994b 100644
--- a/rir/src/compiler/compiler.cpp
+++ b/rir/src/compiler/compiler.cpp
@@ -239,6 +239,43 @@ void Compiler::compileClosure(Closure* closure, rir::Function* optFunction,
 
 bool MEASURE_COMPILER_PERF = getenv("PIR_MEASURE_COMPILER") ? true : false;
 
+static void resetVersionsRefCountState(Module* m) {
+
+    m->eachPirClosure([&](Closure* c) {
+        c->eachVersion([&](ClosureVersion* v) {
+            v->staticCallRefCount = 0;
+            v->isClone = false;
+        });
+    });
+
+    m->eachPirClosure([&](Closure* c) {
+        c->eachVersion([&](ClosureVersion* v) {
+            auto check = [&](Instruction* i) {
+                if (auto call = StaticCall::Cast(i)) {
+                    call->updateVersionRefCount();
+                } else if (auto call = CallInstruction::CastCall(i)) {
+                    if (auto cls = call->tryGetCls()) {
+
+                        if (auto dispatchedVersion = call->tryDispatch(cls)) {
+                            dispatchedVersion->staticCallRefCount++;
+                        }
+                    }
+                }
+            };
+
+            Visitor::run(v->entry, check);
+            v->eachPromise([&](Promise* p) { Visitor::run(p->entry, check); });
+        });
+    });
+
+    m->eachPirClosure([&](Closure* c) {
+        c->eachVersion([&](ClosureVersion* v) {
+            if (v->staticCallRefCount == 0)
+                v->staticCallRefCount = 1;
+        });
+    });
+}
+
 static void findUnreachable(Module* m, Log& log, const std::string& where) {
     std::unordered_map<Closure*, std::unordered_set<Context>> reachable;
     bool changed = true;
@@ -283,6 +320,7 @@ static void findUnreachable(Module* m, Log& log, const std::string& where) {
                                 i->printRecursive(msg, 2);
                                 log.warn(msg.str());
                             }
+
                             found(call->tryDispatch());
                             found(call->tryOptimisticDispatch());
                             found(call->hint);
@@ -310,6 +348,7 @@ static void findUnreachable(Module* m, Log& log, const std::string& where) {
     m->eachPirClosure([&](Closure* c) {
         const auto& reachableVersions = reachable[c];
         c->eachVersion([&](ClosureVersion* v) {
+            // assert(c->getVersion(v->context()) == v);
             if (!reachableVersions.count(v->context())) {
                 toErase.push_back({v->owner(), v->context()});
                 log.close(v);
@@ -320,6 +359,8 @@ static void findUnreachable(Module* m, Log& log, const std::string& where) {
 
     for (auto e : toErase)
         e.first->erase(e.second);
+
+    resetVersionsRefCountState(m);
 };
 
 void Compiler::optimizeClosureVersion(ClosureVersion* v) {
diff --git a/rir/src/compiler/native/lower_function_llvm.cpp b/rir/src/compiler/native/lower_function_llvm.cpp
index 622779a91..aa5ca17b6 100644
--- a/rir/src/compiler/native/lower_function_llvm.cpp
+++ b/rir/src/compiler/native/lower_function_llvm.cpp
@@ -3387,6 +3387,9 @@ void LowerFunctionLLVM::compile() {
                 if (calli->isReordered())
                     callId = pushArgReordering(calli->getArgOrderOrig());
 
+                if (!target)
+                    assert(target && "target is null!");
+
                 if (!target->owner()->hasOriginClosure()) {
                     setVal(
                         i, withCallFrame(args, [&]() -> llvm::Value* {
diff --git a/rir/src/compiler/opt/eager_calls.cpp b/rir/src/compiler/opt/eager_calls.cpp
index 63e2d8051..bee4727ef 100644
--- a/rir/src/compiler/opt/eager_calls.cpp
+++ b/rir/src/compiler/opt/eager_calls.cpp
@@ -15,6 +15,46 @@
 namespace rir {
 namespace pir {
 
+static ClosureVersion*
+cloneOrReplaceVersion(Closure* target, ClosureVersion* version,
+                      StaticCall* call, Context assumptions,
+                      const std::function<void(ClosureVersion*)>&
+                          updateVersionWithNewAssumptions) {
+    if (version != call->lastSeen) {
+        version->staticCallRefCount++;
+    }
+
+    ClosureVersion* newVersion;
+
+    call->lastSeen = nullptr;
+    if (version->isClone || version->staticCallRefCount > 1) {
+
+        newVersion = target->cloneWithAssumptions(
+            version, assumptions, [&](ClosureVersion* newCls) {
+                updateVersionWithNewAssumptions(newCls);
+            });
+
+        if (newVersion != version) {
+            newVersion->isClone = true;
+
+            call->lastSeen = newVersion;
+            version->staticCallRefCount--;
+        }
+
+    } else {
+
+        newVersion = target->replaceWithAssumptions(
+            version, assumptions, updateVersionWithNewAssumptions);
+
+        call->lastSeen = newVersion;
+        if (newVersion->staticCallRefCount == 0) {
+            newVersion->staticCallRefCount = 1;
+        }
+    }
+
+    return newVersion;
+}
+
 bool EagerCalls::apply(Compiler& cmp, ClosureVersion* cls, Code* code,
                        AbstractLog& log, size_t) const {
     AvailableCheckpoints checkpoint(cls, code, log);
@@ -287,8 +327,9 @@ bool EagerCalls::apply(Compiler& cmp, ClosureVersion* cls, Code* code,
                 // version. Maybe we should limit this at some point, to avoid
                 // version explosion.
                 if (availableAssumptions.isImproving(version)) {
-                    auto newVersion = target->cloneWithAssumptions(
-                        version, availableAssumptions,
+
+
+                    auto updateVersionWithNewAssumptions =
                         [&](ClosureVersion* newCls) {
                             Visitor::run(newCls->entry, [&](Instruction* i) {
                                 if (auto f = Force::Cast(i)) {
@@ -308,7 +349,12 @@ bool EagerCalls::apply(Compiler& cmp, ClosureVersion* cls, Code* code,
                                     }
                                 }
                             });
-                        });
+                        };
+
+                    auto newVersion = cloneOrReplaceVersion(
+                        target, version, call, availableAssumptions,
+                        updateVersionWithNewAssumptions);
+
                     call->hint = newVersion;
                     assert(call->tryDispatch() == newVersion);
                     ip = next;
diff --git a/rir/src/compiler/opt/match_call_args.cpp b/rir/src/compiler/opt/match_call_args.cpp
index 561d4a67c..f70075be3 100644
--- a/rir/src/compiler/opt/match_call_args.cpp
+++ b/rir/src/compiler/opt/match_call_args.cpp
@@ -239,9 +239,11 @@ bool MatchCallArgs::apply(Compiler& cmp, ClosureVersion* cls, Code* code,
 
                 if (staticallyArgmatched && target) {
                     anyChange = true;
+
                     if (auto c = call) {
                         assert(!usemethodTarget);
                         auto cls = c->cls()->followCastsAndForce();
+
                         auto nc = new StaticCall(
                             c->env(), target, asmpt, matchedArgs, argOrderOrig,
                             c->frameStateOrTs(), c->srcIdx, cls);
@@ -249,6 +251,7 @@ bool MatchCallArgs::apply(Compiler& cmp, ClosureVersion* cls, Code* code,
                     } else if (auto c = namedCall) {
                         assert(!usemethodTarget);
                         auto cls = c->cls()->followCastsAndForce();
+
                         auto nc = new StaticCall(
                             c->env(), target, asmpt, matchedArgs, argOrderOrig,
                             c->frameStateOrTs(), c->srcIdx, cls);
diff --git a/rir/src/compiler/pir/closure.cpp b/rir/src/compiler/pir/closure.cpp
index cb9e3df6f..988531403 100644
--- a/rir/src/compiler/pir/closure.cpp
+++ b/rir/src/compiler/pir/closure.cpp
@@ -54,6 +54,25 @@ ClosureVersion* Closure::cloneWithAssumptions(ClosureVersion* version,
     return copy;
 }
 
+ClosureVersion* Closure::replaceWithAssumptions(ClosureVersion* version,
+                                                const Context& asmpt,
+                                                const MaybeClsVersion& change) {
+    assert(versions.count(version->context()) > 0);
+
+    auto newCtx = version->context() | asmpt;
+    if (versions.count(newCtx)) {
+        return versions.at(newCtx);
+    }
+
+    versions.erase(version->context());
+
+    version->setContext(newCtx);
+
+    versions[newCtx] = version;
+    change(version);
+    return version;
+}
+
 ClosureVersion* Closure::findCompatibleVersion(const Context& ctx) const {
     // ordered by number of assumptions
     for (auto& candidate : versions) {
diff --git a/rir/src/compiler/pir/closure.h b/rir/src/compiler/pir/closure.h
index e07df5061..52cc56a40 100644
--- a/rir/src/compiler/pir/closure.h
+++ b/rir/src/compiler/pir/closure.h
@@ -51,6 +51,7 @@ class Closure {
     Context userContext_;
 
   public:
+
     bool matchesUserContext(Context c) const {
         return c.smaller(this->userContext_);
     }
@@ -90,6 +91,10 @@ class Closure {
                                          const Context& asmpt,
                                          const MaybeClsVersion& change);
 
+    ClosureVersion* replaceWithAssumptions(ClosureVersion* cls,
+                                           const Context& asmpt,
+                                           const MaybeClsVersion& change);
+
     typedef std::function<void(pir::ClosureVersion*)> ClosureVersionIterator;
     void eachVersion(ClosureVersionIterator it) const;
 
diff --git a/rir/src/compiler/pir/closure_version.h b/rir/src/compiler/pir/closure_version.h
index 7421dc226..5be9049b9 100644
--- a/rir/src/compiler/pir/closure_version.h
+++ b/rir/src/compiler/pir/closure_version.h
@@ -42,11 +42,12 @@ class ClosureVersion : public Code {
     const bool root;
 
     rir::Function* optFunction;
+    size_t staticCallRefCount = 0;
 
   private:
     Closure* owner_;
     std::vector<Promise*> promises_;
-    const Context optimizationContext_;
+    Context optimizationContext_;
 
     std::string name_;
     std::string nameSuffix_;
@@ -59,9 +60,14 @@ class ClosureVersion : public Code {
     friend class Closure;
 
   public:
+    bool isClone = false;
+
     ClosureVersion* clone(const Context& newContext);
 
     const Context& context() const { return optimizationContext_; }
+    void setContext(const Context& newContext) {
+        optimizationContext_ = newContext;
+    }
 
     Properties properties;
 
diff --git a/rir/src/compiler/pir/instruction.cpp b/rir/src/compiler/pir/instruction.cpp
index 8735fd107..8c7eb8a06 100644
--- a/rir/src/compiler/pir/instruction.cpp
+++ b/rir/src/compiler/pir/instruction.cpp
@@ -1255,6 +1255,7 @@ StaticCall::StaticCall(Value* callerEnv, ClosureVersion* clsVersion,
                        Context givenContext, const std::vector<Value*>& args,
                        const ArglistOrder::CallArglistOrder& argOrderOrig,
                        Value* fs, unsigned srcIdx, Value* runtimeClosure)
+
     : VarLenInstructionWithEnvSlot(PirType::val(), callerEnv, srcIdx),
       cls_(clsVersion->owner()), argOrderOrig(argOrderOrig),
       givenContext(givenContext) {
@@ -1276,7 +1277,27 @@ StaticCall::StaticCall(Value* callerEnv, ClosureVersion* clsVersion,
         }
     }
 
+    auto dispatched = tryDispatch();
     assert(tryDispatch() == clsVersion);
+
+    // Update version-refCount fields
+    dispatched->staticCallRefCount++;
+    lastSeen = dispatched;
+}
+
+void StaticCall::updateVersionRefCount() {
+    lastSeen = nullptr;
+    auto target = tryDispatch();
+    if (target) {
+        lastSeen = target;
+        target->staticCallRefCount++;
+    }
+}
+
+Instruction* StaticCall::clone() const {
+    auto sc = StaticCall::Cast(InstructionImplementation::clone());
+    sc->updateVersionRefCount();
+    return sc;
 }
 
 PirType StaticCall::inferType(const GetType& getType) const {
diff --git a/rir/src/compiler/pir/instruction.h b/rir/src/compiler/pir/instruction.h
index 63739a3c0..ba098b2eb 100644
--- a/rir/src/compiler/pir/instruction.h
+++ b/rir/src/compiler/pir/instruction.h
@@ -62,6 +62,7 @@ namespace pir {
 
 class BB;
 class Closure;
+
 class Phi;
 
 struct InstrArg {
@@ -2268,6 +2269,7 @@ class VLIE(StaticCall, Effects::Any()), public CallInstruction {
                const ArglistOrder::CallArglistOrder& argOrderOrig, Value* fs,
                unsigned srcIdx, Value* runtimeClosure = Tombstone::closure());
 
+    ClosureVersion* lastSeen = nullptr;
     Context givenContext;
 
     ClosureVersion* hint = nullptr;
@@ -2279,6 +2281,9 @@ class VLIE(StaticCall, Effects::Any()), public CallInstruction {
 
     size_t nCallArgs() const override { return nargs() - 3; }
 
+    Instruction* clone() const override;
+    void updateVersionRefCount();
+
     void eachNamedCallArg(const NamedArgumentValueIterator& it) const override {
         for (size_t i = 0; i < nCallArgs(); ++i)
             it(R_NilValue, arg(i + 2).val());
diff --git a/rir/src/compiler/rir2pir/rir2pir.cpp b/rir/src/compiler/rir2pir/rir2pir.cpp
index 49309d7c1..daba908f1 100644
--- a/rir/src/compiler/rir2pir/rir2pir.cpp
+++ b/rir/src/compiler/rir2pir/rir2pir.cpp
@@ -928,13 +928,14 @@ bool Rir2Pir::compileBC(const BC& bc, Opcode* pos, Opcode* nextPos,
                 assert(!inlining());
                 auto fs = insert.registerFrameState(srcCode, nextPos, stack,
                                                     inPromise());
+
                 auto cl = insert(
                     new StaticCall(insert.env, f, given, matchedArgs,
                                    std::move(argOrderOrig), fs, ast,
                                    f->owner()->closureEnv() == Env::notClosed()
                                        ? guardedCallee
                                        : Tombstone::closure()));
-                cl->effects.set(Effect::DependsOnAssume);
+
                 push(cl);
 
                 auto innerc = MkCls::Cast(guardedCallee->followCastsAndForce());