diff --git a/src/script_opt/CPP/Compile.h b/src/script_opt/CPP/Compile.h
index 5d818c1756..6b5cb20cf2 100644
--- a/src/script_opt/CPP/Compile.h
+++ b/src/script_opt/CPP/Compile.h
@@ -135,7 +135,8 @@ class CPPCompile {
 public:
 	CPPCompile(std::vector<FuncInfo>& _funcs, ProfileFuncs& pfs,
 	           const std::string& gen_name, const std::string& addl_name,
-	           CPPHashManager& _hm, bool _update, bool _standalone);
+	           CPPHashManager& _hm, bool _update, bool _standalone,
+	           bool report_uncompilable);
 	~CPPCompile();
 
 private:
@@ -145,7 +146,7 @@ private:
 	//
 
 	// Main driver, invoked by constructor.
-	void Compile();
+	void Compile(bool report_uncompilable);
 
 	// Generate the beginning of the compiled code: run-time functions,
 	// namespace, auxiliary globals.
@@ -161,8 +162,11 @@ private:
 	void GenEpilog();
 
 	// True if the given function (plus body and profile) is one 
-	// that should be compiled.
-	bool IsCompilable(const FuncInfo& func);
+	// that should be compiled.  If non-nil, sets reason to the
+	// the reason why, if there's a fundamental problem.  If however
+	// the function should be skipped for other reasons, then sets
+	// it to nil.
+	bool IsCompilable(const FuncInfo& func, const char** reason = nullptr);
 
 	// The set of functions/bodies we're compiling.
 	std::vector<FuncInfo>& funcs;
diff --git a/src/script_opt/CPP/Driver.cc b/src/script_opt/CPP/Driver.cc
index 7d8d016922..d9d0081300 100644
--- a/src/script_opt/CPP/Driver.cc
+++ b/src/script_opt/CPP/Driver.cc
@@ -14,7 +14,8 @@ using namespace std;
 
 CPPCompile::CPPCompile(vector<FuncInfo>& _funcs, ProfileFuncs& _pfs,
                        const string& gen_name, const string& _addl_name,
-                       CPPHashManager& _hm, bool _update, bool _standalone)
+                       CPPHashManager& _hm, bool _update, bool _standalone,
+		       bool report_uncompilable)
 : funcs(_funcs), pfs(_pfs), hm(_hm),
   update(_update), standalone(_standalone)
 	{
@@ -67,7 +68,7 @@ CPPCompile::CPPCompile(vector<FuncInfo>& _funcs, ProfileFuncs& _pfs,
 		fclose(addl_f);
 		}
 
-	Compile();
+	Compile(report_uncompilable);
 	}
 
 CPPCompile::~CPPCompile()
@@ -75,7 +76,7 @@ CPPCompile::~CPPCompile()
 	fclose(write_file);
 	}
 
-void CPPCompile::Compile()
+void CPPCompile::Compile(bool report_uncompilable)
 	{
 	// Get the working directory so we can use it in diagnostic messages
 	// as a way to identify this compilation.  Only germane when doing
@@ -100,8 +101,13 @@ void CPPCompile::Compile()
 			// Can't be called directly.
 			continue;
 
-		if ( IsCompilable(func) )
+		const char* reason;
+		if ( IsCompilable(func, &reason) )
 			compilable_funcs.insert(BodyName(func));
+		else if ( reason && report_uncompilable )
+			fprintf(stderr,
+			        "%s cannot be compiled to C++ due to %s\n",
+				func.Func()->Name(), reason);
 
 		auto h = func.Profile()->HashVal();
 		if ( hm.HasHash(h) )
@@ -341,17 +347,24 @@ void CPPCompile::GenEpilog()
 	Emit("} // zeek::detail");
 	}
 
-bool CPPCompile::IsCompilable(const FuncInfo& func)
+bool CPPCompile::IsCompilable(const FuncInfo& func, const char** reason)
 	{
+	if ( ! is_CPP_compilable(func.Profile(), reason) )
+		return false;
+
+	if ( reason )
+		// Indicate that there's no fundamental reason it can't be
+		// compiled.
+		*reason = nullptr;
+
 	if ( func.ShouldSkip() )
-		// Caller marked this function as one to skip.
 		return false;
 
 	if ( hm.HasHash(func.Profile()->HashVal()) )
 		// We've already compiled it.
 		return false;
 
-	return is_CPP_compilable(func.Profile());
+	return true;
 	}
 
 } // zeek::detail
diff --git a/src/script_opt/CPP/Util.cc b/src/script_opt/CPP/Util.cc
index 4c86ccbcf9..30adbb2578 100644
--- a/src/script_opt/CPP/Util.cc
+++ b/src/script_opt/CPP/Util.cc
@@ -33,13 +33,21 @@ string scope_prefix(int scope)
 	return scope_prefix(to_string(scope));
 	}
 
-bool is_CPP_compilable(const ProfileFunc* pf)
+bool is_CPP_compilable(const ProfileFunc* pf, const char** reason)
 	{
 	if ( pf->NumWhenStmts() > 0 )
+		{
+		if ( reason )
+			*reason = "use of \"when\"";
 		return false;
+		}
 
 	if ( pf->TypeSwitches().size() > 0 )
+		{
+		if ( reason )
+			*reason = "use of type-based \"switch\"";
 		return false;
+		}
 
 	return true;
 	}
diff --git a/src/script_opt/CPP/Util.h b/src/script_opt/CPP/Util.h
index 25b7a0abc6..a44fe8cfd8 100644
--- a/src/script_opt/CPP/Util.h
+++ b/src/script_opt/CPP/Util.h
@@ -19,8 +19,11 @@ extern std::string scope_prefix(const std::string& scope);
 // Same, but for scopes identified with numbers.
 extern std::string scope_prefix(int scope);
 
-// True if the given function is compilable to C++.
-extern bool is_CPP_compilable(const ProfileFunc* pf);
+// True if the given function is compilable to C++.  If it isn't, and
+// the second argument is non-nil, then on return it points to text
+// explaining why not.
+extern bool is_CPP_compilable(const ProfileFunc* pf,
+                              const char** reason = nullptr);
 
 // Helper utilities for file locking, to ensure that hash files
 // don't receive conflicting writes due to concurrent compilations.
diff --git a/src/script_opt/GenRDs.cc b/src/script_opt/GenRDs.cc
index 0ab24eea19..8c59ce4a4d 100644
--- a/src/script_opt/GenRDs.cc
+++ b/src/script_opt/GenRDs.cc
@@ -10,6 +10,13 @@
 namespace zeek::detail {
 
 
+RD_Decorate::RD_Decorate(std::shared_ptr<ProfileFunc> _pf, const Func* f,
+	                 ScopePtr scope, StmtPtr body)
+: pf(std::move(_pf))
+	{
+	TraverseFunction(f, scope, body);
+	}
+
 void RD_Decorate::TraverseFunction(const Func* f, ScopePtr scope, StmtPtr body)
 	{
 	func_flavor = f->Flavor();
diff --git a/src/script_opt/GenRDs.h b/src/script_opt/GenRDs.h
index cfdfc5e34c..73e1ca4149 100644
--- a/src/script_opt/GenRDs.h
+++ b/src/script_opt/GenRDs.h
@@ -50,9 +50,12 @@ private:
 
 class RD_Decorate : public TraversalCallback {
 public:
-	RD_Decorate(std::shared_ptr<ProfileFunc> _pf) : pf(std::move(_pf))
-		{ }
+	RD_Decorate(std::shared_ptr<ProfileFunc> _pf, const Func* f,
+	            ScopePtr scope, StmtPtr body);
 
+	const DefSetsMgr* GetDefSetsMgr() const	{ return &mgr; }
+
+private:
 	// Traverses the given function body, using the first two
 	// arguments for context.
 	void TraverseFunction(const Func* f, ScopePtr scope, StmtPtr body);
@@ -62,9 +65,6 @@ public:
 	TraversalCode PreExpr(const Expr*) override;
 	TraversalCode PostExpr(const Expr*) override;
 
-	const DefSetsMgr* GetDefSetsMgr() const	{ return &mgr; }
-
-private:
 	// The following implement various types of "confluence", i.e.,
 	// situations in which control flow merges from multiple possible
 	// paths to a given point.
diff --git a/src/script_opt/ProfileFunc.cc b/src/script_opt/ProfileFunc.cc
index 1d18037834..a1b9399146 100644
--- a/src/script_opt/ProfileFunc.cc
+++ b/src/script_opt/ProfileFunc.cc
@@ -459,7 +459,7 @@ ProfileFuncs::ProfileFuncs(std::vector<FuncInfo>& funcs,
 		auto pf = std::make_unique<ProfileFunc>(f.Func(), f.Body(),
 		                                        full_record_hashes);
 
-		if ( ! pred || (*pred)(pf.get()) )
+		if ( ! pred || (*pred)(pf.get(), nullptr) )
 			MergeInProfile(pf.get());
 		else
 			f.SetSkip(true);
diff --git a/src/script_opt/ProfileFunc.h b/src/script_opt/ProfileFunc.h
index f2fc206310..c653281c7e 100644
--- a/src/script_opt/ProfileFunc.h
+++ b/src/script_opt/ProfileFunc.h
@@ -281,7 +281,7 @@ protected:
 // profile is compilable.  Alternatively we could derive subclasses
 // from ProfileFuncs and use a virtual method for this, but that seems
 // heavier-weight for what's really a simple notion.
-typedef bool (*is_compilable_pred)(const ProfileFunc*);
+typedef bool (*is_compilable_pred)(const ProfileFunc*, const char** reason);
 
 // Collectively profile an entire collection of functions.
 class ProfileFuncs {
diff --git a/src/script_opt/Reduce.cc b/src/script_opt/Reduce.cc
index 481e3a9afd..023285e322 100644
--- a/src/script_opt/Reduce.cc
+++ b/src/script_opt/Reduce.cc
@@ -7,6 +7,8 @@
 #include "zeek/Stmt.h"
 #include "zeek/Desc.h"
 #include "zeek/Reporter.h"
+#include "zeek/script_opt/ExprOptInfo.h"
+#include "zeek/script_opt/StmtOptInfo.h"
 #include "zeek/script_opt/ProfileFunc.h"
 #include "zeek/script_opt/Reduce.h"
 #include "zeek/script_opt/TempVar.h"
@@ -33,6 +35,10 @@ ExprPtr Reducer::GenTemporaryExpr(const TypePtr& t, ExprPtr rhs)
 	{
 	auto e = make_intrusive<NameExpr>(GenTemporary(t, rhs));
 	e->SetLocationInfo(rhs->GetLocationInfo());
+
+	// No need to associate with current statement, since these
+	// are not generated during optimization.
+
 	return e;
 	}
 
@@ -41,7 +47,13 @@ NameExprPtr Reducer::UpdateName(NameExprPtr n)
 	if ( NameIsReduced(n.get()) )
 		return n;
 
-	return make_intrusive<NameExpr>(FindNewLocal(n));
+	auto ne = make_intrusive<NameExpr>(FindNewLocal(n));
+
+	// This name can be used by follow-on optimization analysis,
+	// so need to associate it with its statement.
+	BindExprToCurrStmt(ne);
+
+	return ne;
 	}
 
 bool Reducer::NameIsReduced(const NameExpr* n) const
@@ -106,6 +118,8 @@ bool Reducer::ID_IsReduced(const ID* id) const
 
 NameExprPtr Reducer::GenInlineBlockName(const IDPtr& id)
 	{
+	// We do this during reduction, not optimization, so no need
+	// to associate with curr_stmt.
 	return make_intrusive<NameExpr>(GenLocal(id));
 	}
 
@@ -118,6 +132,7 @@ NameExprPtr Reducer::PushInlineBlock(TypePtr type)
 
 	IDPtr ret_id = install_ID("@retvar", "<internal>", false, false);
 	ret_id->SetType(type);
+	ret_id->GetOptInfo()->SetTemp();
 
 	// Track this as a new local *if* we're in the outermost inlining
 	// block.  If we're recursively deeper into inlining, then this
@@ -141,48 +156,22 @@ bool Reducer::SameVal(const Val* v1, const Val* v2) const
 		return v1 == v2;
 	}
 
-ExprPtr Reducer::NewVarUsage(IDPtr var, const DefPoints* dps, const Expr* orig)
+ExprPtr Reducer::NewVarUsage(IDPtr var, const Expr* orig)
 	{
-	if ( ! dps )
-		reporter->InternalError("null defpoints in NewVarUsage");
-
 	auto var_usage = make_intrusive<NameExpr>(var);
-	SetDefPoints(var_usage.get(), dps);
-	TrackExprReplacement(orig, var_usage.get());
+	BindExprToCurrStmt(var_usage);
 
 	return var_usage;
 	}
 
-const DefPoints* Reducer::GetDefPoints(const NameExpr* var)
+void Reducer::BindExprToCurrStmt(const ExprPtr& e)
 	{
-	auto dps = FindDefPoints(var);
-
-	if ( ! dps )
-		{
-		auto id = var->Id();
-		auto di = mgr->GetConstID_DI(id);
-		auto rds = mgr->GetPreMaxRDs(GetRDLookupObj(var));
-
-		dps = rds->GetDefPoints(di);
-
-		SetDefPoints(var, dps);
-		}
-
-	return dps;
+	e->GetOptInfo()->stmt_num = curr_stmt->GetOptInfo()->stmt_num;
 	}
 
-const DefPoints* Reducer::FindDefPoints(const NameExpr* var) const
+void Reducer::BindStmtToCurrStmt(const StmtPtr& s)
 	{
-	auto dps = var_usage_to_DPs.find(var);
-	if ( dps == var_usage_to_DPs.end() )
-		return nullptr;
-	else
-		return dps->second;
-	}
-
-void Reducer::SetDefPoints(const NameExpr* var, const DefPoints* dps)
-	{
-	var_usage_to_DPs[var] = dps;
+	s->GetOptInfo()->stmt_num = curr_stmt->GetOptInfo()->stmt_num;
 	}
 
 bool Reducer::SameOp(const Expr* op1, const Expr* op2)
@@ -196,7 +185,7 @@ bool Reducer::SameOp(const Expr* op1, const Expr* op2)
 	if ( op1->Tag() == EXPR_NAME )
 		{
 		// Needs to be both the same identifier and in contexts
-		// where the identifier has the same definition points.
+		// where the identifier has the same definitions.
 		auto op1_n = op1->AsNameExpr();
 		auto op2_n = op2->AsNameExpr();
 
@@ -206,10 +195,13 @@ bool Reducer::SameOp(const Expr* op1, const Expr* op2)
 		if ( op1_id != op2_id )
 			return false;
 
-		auto op1_dps = GetDefPoints(op1_n);
-		auto op2_dps = GetDefPoints(op2_n);
+		auto e_stmt_1 = op1->GetOptInfo()->stmt_num;
+		auto e_stmt_2 = op2->GetOptInfo()->stmt_num;
 
-		return same_DPs(op1_dps, op2_dps);
+		auto def_1 = op1_id->GetOptInfo()->DefinitionBefore(e_stmt_1);
+		auto def_2 = op2_id->GetOptInfo()->DefinitionBefore(e_stmt_2);
+
+		return def_1 == def_2 && def_1 != NO_DEF;
 		}
 
 	else if ( op1->Tag() == EXPR_CONST )
@@ -391,11 +383,10 @@ IDPtr Reducer::FindExprTmp(const Expr* rhs, const Expr* a,
 			// always makes it here.
 			auto id = et_i->Id().get();
 
-			// We use 'a' in the following rather than rhs
-			// because the RHS can get rewritten (for example,
-			// due to folding) after we generate RDs, and
-			// thus might not have any.
-			if ( ! mgr->HasSinglePreMinRD(a, id) )
+			auto stmt_num = a->GetOptInfo()->stmt_num;
+			auto def = id->GetOptInfo()->DefinitionBefore(stmt_num);
+
+			if ( def == NO_DEF )
 				// The temporary's value isn't guaranteed
 				// to make it here.
 				continue;
@@ -470,8 +461,6 @@ void Reducer::CheckIDs(const Expr* e, std::vector<const ID*>& ids) const
 
 bool Reducer::IsCSE(const AssignExpr* a, const NameExpr* lhs, const Expr* rhs)
 	{
-	auto a_max_rds = mgr->GetPostMaxRDs(GetRDLookupObj(a));
-
 	auto lhs_id = lhs->Id();
 	auto lhs_tmp = FindTemporary(lhs_id);	// nil if LHS not a temporary
 	auto rhs_tmp = FindExprTmp(rhs, a, lhs_tmp);
@@ -479,9 +468,7 @@ bool Reducer::IsCSE(const AssignExpr* a, const NameExpr* lhs, const Expr* rhs)
 	ExprPtr new_rhs;
 	if ( rhs_tmp )
 		{ // We already have a temporary
-		auto tmp_di = mgr->GetConstID_DI(rhs_tmp.get());
-		auto dps = a_max_rds->GetDefPoints(tmp_di);
-		new_rhs = NewVarUsage(rhs_tmp, dps, rhs);
+		new_rhs = NewVarUsage(rhs_tmp, rhs);
 		rhs = new_rhs.get();
 		}
 
@@ -507,104 +494,73 @@ bool Reducer::IsCSE(const AssignExpr* a, const NameExpr* lhs, const Expr* rhs)
 			// Treat the LHS as either an alias for the RHS,
 			// or as a constant if the RHS is a constant in
 			// this context.
-			auto rhs_di = mgr->GetConstID_DI(rhs_id.get());
-			auto dps = a_max_rds->GetDefPoints(rhs_di);
+			auto stmt_num = a->GetOptInfo()->stmt_num;
+			auto rhs_const = CheckForConst(rhs_id, stmt_num);
 
-			auto rhs_const = CheckForConst(rhs_id, dps);
 			if ( rhs_const )
 				lhs_tmp->SetConst(rhs_const);
 			else
-				lhs_tmp->SetAlias(rhs_id, dps);
+				lhs_tmp->SetAlias(rhs_id);
 
 			return true;
 			}
 
-		// Track where we define the temporary.
-		auto lhs_di = mgr->GetConstID_DI(lhs_id);
-		auto dps = a_max_rds->GetDefPoints(lhs_di);
-		if ( lhs_tmp->DPs() && ! same_DPs(lhs_tmp->DPs(), dps) )
-			reporter->InternalError("double DPs for temporary");
-
-		lhs_tmp->SetDPs(dps);
-		SetDefPoints(lhs, dps);
-
 		expr_temps.emplace_back(lhs_tmp);
 		}
 
 	return false;
 	}
 
-const ConstExpr* Reducer::CheckForConst(const IDPtr& id,
-					const DefPoints* dps) const
+const ConstExpr* Reducer::CheckForConst(const IDPtr& id, int stmt_num) const
 	{
-	if ( ! dps || dps->length() == 0 )
-		// This can happen for access to uninitialized values.
+	if ( id->GetType()->Tag() == TYPE_ANY )
+		// Don't propagate identifiers of type "any" as constants.
+		// This is because the identifier might be used in some
+		// context that's dynamically unreachable due to the type
+		// of its value (such as via a type-switch), but for which
+		// constant propagation of the constant value to that
+		// context can result in compile-time errors when folding
+		// expressions in which the identifier appears (and is
+		// in that context presumed to have a different type).
 		return nullptr;
 
-	if ( dps->length() != 1 )
-		// Multiple definitions of the variable reach to this
-		// location.  In theory we could check whether they *all*
-		// provide the same constant, but that hardly seems likely.
-		return nullptr;
+	auto oi = id->GetOptInfo();
+	auto c = oi->Const();
 
-	// Identifier has a unique definition.
-	auto dp = (*dps)[0];
-	const Expr* e = nullptr;
+	if ( c )
+		return c;
 
-	if ( dp.Tag() == STMT_DEF )
+	auto e = id->GetOptInfo()->DefExprBefore(stmt_num);
+	if ( e )
 		{
-		auto s = dp.StmtVal();
+		auto ce = constant_exprs.find(e.get());
+		if ( ce != constant_exprs.end() )
+			e = ce->second;
 
-		if ( s->Tag() == STMT_CATCH_RETURN )
-			{
-			// Change 's' to refer to the associated assignment
-			// statement, if any.
-			auto cr = s->AsCatchReturnStmt();
-			s = cr->AssignStmt().get();
+		if ( e->Tag() == EXPR_CONST )
+			return e->AsConstExpr();
 
-			if ( ! s )
-				return nullptr;
-			}
-
-		if ( s->Tag() != STMT_EXPR )
-			// Defined in a statement other than an assignment.
+		// Follow aliases.
+		if ( e->Tag() != EXPR_NAME )
 			return nullptr;
 
-		e = s->AsExprStmt()->StmtExpr();
+		return CheckForConst(e->AsNameExpr()->IdPtr(), stmt_num);
 		}
 
-	else if ( dp.Tag() == EXPR_DEF )
-		e = dp.ExprVal();
-
-	else
-		return nullptr;
-
-	if ( e->Tag() != EXPR_ASSIGN )
-		// Not sure why this would happen, other than EXPR_APPEND_TO,
-		// but in any case not an expression we can mine for a
-		// constant.
-		return nullptr;
-
-	auto rhs = e->GetOp2();
-
-	if ( rhs->Tag() != EXPR_CONST )
-		return nullptr;
-
-	return rhs->AsConstExpr();
+	return nullptr;
 	}
 
-void Reducer::TrackExprReplacement(const Expr* orig, const Expr* e)
+ConstExprPtr Reducer::Fold(ExprPtr e)
 	{
-	new_expr_to_orig[e] = orig;
+	auto c = make_intrusive<ConstExpr>(e->Eval(nullptr));
+	FoldedTo(e, c);
+	return c;
 	}
 
-const Obj* Reducer::GetRDLookupObj(const Expr* e) const
+void Reducer::FoldedTo(ExprPtr e, ConstExprPtr c)
 	{
-	auto orig_e = new_expr_to_orig.find(e);
-	if ( orig_e == new_expr_to_orig.end() )
-		return e;
-	else
-		return orig_e->second;
+	constant_exprs[e.get()] = std::move(c);
+	folded_exprs.push_back(std::move(e));
 	}
 
 ExprPtr Reducer::OptExpr(Expr* e)
@@ -635,13 +591,10 @@ ExprPtr Reducer::UpdateExpr(ExprPtr e)
 	auto tmp_var = FindTemporary(id);
 	if ( ! tmp_var )
 		{
-		auto max_rds = mgr->GetPreMaxRDs(GetRDLookupObj(n));
-
 		IDPtr id_ptr = {NewRef{}, id};
-		auto di = mgr->GetConstID_DI(id);
-		auto dps = max_rds->GetDefPoints(di);
+		auto stmt_num = e->GetOptInfo()->stmt_num;
+		auto is_const = CheckForConst(id_ptr, stmt_num);
 
-		auto is_const = CheckForConst(id_ptr, dps);
 		if ( is_const )
 			{
 			// Remember this variable as one whose value
@@ -662,36 +615,33 @@ ExprPtr Reducer::UpdateExpr(ExprPtr e)
 	auto alias = tmp_var->Alias();
 	if ( alias )
 		{
-		// Make sure that the definition points for the
-		// alias here are the same as when the alias
-		// was created.
+		// Make sure that the definitions for the alias here are
+		// the same as when the alias was created.
 		auto alias_tmp = FindTemporary(alias.get());
 
-		if ( alias_tmp )
+		// Resolve any alias chains.
+		while ( alias_tmp && alias_tmp->Alias() )
 			{
-			while ( alias_tmp->Alias() )
-				{
-				// Alias chains can occur due to
-				// re-reduction while optimizing.
-				auto a_id = alias_tmp->Id();
-				if ( a_id == id )
-					return e;
+			alias = alias_tmp->Alias();
+			alias_tmp = FindTemporary(alias.get());
+			}
 
-				alias_tmp = FindTemporary(alias_tmp->Id().get());
-				}
-
-			// Temporaries always have only one definition point,
+		if ( alias->GetOptInfo()->IsTemp() )
+			{
+			// Temporaries always have only one definition,
 			// so no need to check for consistency.
-			auto new_usage = NewVarUsage(alias, alias_tmp->DPs(), e.get());
+			auto new_usage = NewVarUsage(alias, e.get());
 			return new_usage;
 			}
 
-		auto e_max_rds = mgr->GetPreMaxRDs(GetRDLookupObj(e.get()));
-		auto alias_di = mgr->GetConstID_DI(alias.get());
-		auto alias_dps = e_max_rds->GetDefPoints(alias_di);
+		auto e_stmt_1 = e->GetOptInfo()->stmt_num;
+		auto e_stmt_2 = tmp_var->RHS()->GetOptInfo()->stmt_num;
 
-		if ( same_DPs(alias_dps, tmp_var->DPs()) )
-			return NewVarUsage(alias, alias_dps, e.get());
+		auto def_1 = alias->GetOptInfo()->DefinitionBefore(e_stmt_1);
+		auto def_2 = tmp_var->Id()->GetOptInfo()->DefinitionBefore(e_stmt_2);
+
+		if ( def_1 == def_2 && def_1 != NO_DEF )
+			return NewVarUsage(alias, e.get());
 		else
 			return e;
 		}
@@ -758,9 +708,17 @@ StmtPtr Reducer::MergeStmts(const NameExpr* lhs, ExprPtr rhs, Stmt* succ_stmt)
 	lhs_tmp->Deactivate();
 	auto merge_e = make_intrusive<AssignExpr>(a_lhs_deref, rhs, false,
 						nullptr, nullptr, false);
-	TrackExprReplacement(rhs.get(), merge_e.get());
+	auto merge_e_stmt = make_intrusive<ExprStmt>(merge_e);
 
-	return make_intrusive<ExprStmt>(merge_e);
+	// Update the associated stmt_num's.  For strict correctness, we
+	// want both of these bound to the earlier of the two statements
+	// we're merging (though in practice, either will work, since
+	// we're eliding the only difference between the two).  Our
+	// caller ensures this.
+	BindExprToCurrStmt(merge_e);
+	BindStmtToCurrStmt(merge_e_stmt);
+
+	return merge_e_stmt;
 	}
 
 IDPtr Reducer::GenTemporary(const TypePtr& t, ExprPtr rhs)
@@ -809,6 +767,9 @@ IDPtr Reducer::GenLocal(const IDPtr& orig)
 	local_id->SetType(orig->GetType());
 	local_id->SetAttrs(orig->GetAttrs());
 
+	if ( orig->GetOptInfo()->IsTemp() )
+		local_id->GetOptInfo()->SetTemp();
+
 	new_locals.insert(local_id.get());
 	orig_to_new_locals[orig.get()] = local_id;
 
@@ -1040,27 +1001,6 @@ bool CSE_ValidityChecker::CheckAggrMod(const std::vector<const ID*>& ids,
 	}
 
 
-bool same_DPs(const DefPoints* dp1, const DefPoints* dp2)
-	{
-	if ( dp1 == dp2 )
-		return true;
-
-	if ( ! dp1 || ! dp2 )
-		return false;
-
-	// Given how we construct DPs, they should be element-by-element
-	// equivalent; we don't have to worry about reordering.
-	if ( dp1->length() != dp2->length() )
-		return false;
-
-	for ( auto i = 0; i < dp1->length(); ++i )
-		if ( ! (*dp1)[i].SameAs((*dp2)[i]) )
-			return false;
-
-	return true;
-	}
-
-
 const Expr* non_reduced_perp;
 bool checking_reduction;
 
diff --git a/src/script_opt/Reduce.h b/src/script_opt/Reduce.h
index 3df88d2913..db51537ae7 100644
--- a/src/script_opt/Reduce.h
+++ b/src/script_opt/Reduce.h
@@ -6,13 +6,11 @@
 #include "zeek/Expr.h"
 #include "zeek/Stmt.h"
 #include "zeek/Traverse.h"
-#include "zeek/script_opt/DefSetsMgr.h"
 
 namespace zeek::detail {
 
 class Expr;
 class TempVar;
-class ProfileFunc;
 
 class Reducer {
 public:
@@ -20,8 +18,9 @@ public:
 
 	StmtPtr Reduce(StmtPtr s);
 
-	const DefSetsMgr* GetDefSetsMgr() const		{ return mgr; }
-	void SetDefSetsMgr(const DefSetsMgr* _mgr)	{ mgr = _mgr; }
+	void SetReadyToOptimize()	{ opt_ready = true; }
+
+	void SetCurrStmt(const Stmt* stmt)      { curr_stmt = stmt; }
 
 	ExprPtr GenTemporaryExpr(const TypePtr& t, ExprPtr rhs);
 
@@ -76,7 +75,7 @@ public:
 	// True if the Reducer is being used in the context of a second
 	// pass over for AST optimization.
 	bool Optimizing() const
-		{ return ! IsPruning() && mgr != nullptr; }
+		{ return ! IsPruning() && opt_ready; }
 
 	// A predicate that indicates whether a given reduction pass
 	// is being made to prune unused statements.
@@ -126,6 +125,14 @@ public:
 	// already been applied.
 	bool IsCSE(const AssignExpr* a, const NameExpr* lhs, const Expr* rhs);
 
+	// Returns a constant representing folding of the given expression
+	// (which must have constant operands).
+	ConstExprPtr Fold(ExprPtr e);
+
+	// Notes that the given expression has been folded to the
+	// given constant.
+	void FoldedTo(ExprPtr orig, ConstExprPtr c);
+
 	// Given an lhs=rhs statement followed by succ_stmt, returns
 	// a (new) merge of the two if they're of the form tmp=rhs, var=tmp;
 	// otherwise, nil.
@@ -150,23 +157,13 @@ protected:
 	// are in fact equivalent.)
 	bool SameVal(const Val* v1, const Val* v2) const;
 
-	// Track that the variable "var", which has the given set of
-	// definition points, will be a replacement for the "orig"
-	// expression.  Returns the replacement expression (which is
-	// is just a NameExpr referring to "var").
-	ExprPtr NewVarUsage(IDPtr var, const DefPoints* dps, const Expr* orig);
+	// Track that the variable "var" will be a replacement for
+	// the "orig" expression.  Returns the replacement expression
+	// (which is is just a NameExpr referring to "var").
+	ExprPtr NewVarUsage(IDPtr var, const Expr* orig);
 
-	// Returns the definition points associated with "var".  If none
-	// exist in our cache, then populates the cache.
-	const DefPoints* GetDefPoints(const NameExpr* var);
-
-	// Retrieve the definition points associated in our cache with the
-	// given variable, if any.
-	const DefPoints* FindDefPoints(const NameExpr* var) const;
-
-	// Adds a mapping in our cache of the given variable to the given
-	// set of definition points.
-	void SetDefPoints(const NameExpr* var, const DefPoints* dps);
+	void BindExprToCurrStmt(const ExprPtr& e);
+	void BindStmtToCurrStmt(const StmtPtr& s);
 
 	// Returns true if op1 and op2 represent the same operand, given
 	// the reaching definitions available at their usages (e1 and e2).
@@ -216,23 +213,10 @@ protected:
 	// for the current function.
 	IDPtr GenLocal(const IDPtr& orig);
 
-	// This is the heart of constant propagation.  Given an identifier
-	// and a set of definition points for it, if its value is constant
-	// then returns the corresponding ConstExpr with the value.
-	const ConstExpr* CheckForConst(const IDPtr& id,
-					const DefPoints* dps) const;
-
-	// Track that we're replacing instances of "orig" with a new
-	// expression.  This allows us to locate the RDs associated
-	// with "orig" in the context of the new expression, without
-	// requiring an additional RD propagation pass.
-	void TrackExprReplacement(const Expr* orig, const Expr* e);
-
-	// Returns the object we should use to look up RD's associated
-	// with 'e'.  (This isn't necessarily 'e' itself because we
-	// may have decided to replace it with a different expression,
-	// per TrackExprReplacement().)
-	const Obj* GetRDLookupObj(const Expr* e) const;
+	// This is the heart of constant propagation.  Given an identifier,
+	// if its value is constant at the given location then returns
+	// the corresponding ConstExpr with the value.
+	const ConstExpr* CheckForConst(const IDPtr& id, int stmt_num) const;
 
 	// Tracks the temporary variables created during the reduction/
 	// optimization process.
@@ -253,6 +237,14 @@ protected:
 	// rename local variables when inlining.
 	std::unordered_map<const ID*, IDPtr> orig_to_new_locals;
 
+	// Tracks expressions we've folded, so that we can recognize them
+	// for constant propagation.
+	std::unordered_map<const Expr*, ConstExprPtr> constant_exprs;
+
+	// Holds onto those expressions so they don't become invalid
+	// due to memory management.
+	std::vector<ExprPtr> folded_exprs;
+
 	// Which statements to elide from the AST (because optimization
 	// has determined they're no longer needed).
 	std::unordered_set<const Stmt*> omitted_stmts;
@@ -270,25 +262,17 @@ protected:
 	// exponentially.
 	int bifurcation_level = 0;
 
-	// For a given usage of a variable's value, return the definition
-	// points associated with its use at that point.  We use this
-	// both as a cache (populating it every time we do a more laborious
-	// lookup), and proactively when creating new references to variables.
-	std::unordered_map<const NameExpr*, const DefPoints*> var_usage_to_DPs;
-
 	// Tracks which (non-temporary) variables had constant
 	// values used for constant propagation.
 	std::unordered_set<const ID*> constant_vars;
 
-	// For a new expression we've created, map it to the expression
-	// it's replacing.  This allows us to locate the RDs associated
-	// with the usage.
-	std::unordered_map<const Expr*, const Expr*> new_expr_to_orig;
-
 	// Statement at which the current reduction started.
 	StmtPtr reduction_root = nullptr;
 
-	const DefSetsMgr* mgr = nullptr;
+	// Statement we're currently working on.
+	const Stmt* curr_stmt = nullptr;
+
+	bool opt_ready = false;
 };
 
 
@@ -364,8 +348,6 @@ protected:
 };
 
 
-extern bool same_DPs(const DefPoints* dp1, const DefPoints* dp2);
-
 // Used for debugging, to communicate which expression wasn't
 // reduced when we expected them all to be.
 extern const Expr* non_reduced_perp;
diff --git a/src/script_opt/ScriptOpt.cc b/src/script_opt/ScriptOpt.cc
index 47f0765b57..421eac50a8 100644
--- a/src/script_opt/ScriptOpt.cc
+++ b/src/script_opt/ScriptOpt.cc
@@ -6,15 +6,20 @@
 #include "zeek/Desc.h"
 #include "zeek/EventHandler.h"
 #include "zeek/EventRegistry.h"
+
 #include "zeek/script_opt/ScriptOpt.h"
 #include "zeek/script_opt/ProfileFunc.h"
 #include "zeek/script_opt/Inline.h"
 #include "zeek/script_opt/Reduce.h"
+#include "zeek/script_opt/GenIDDefs.h"
 #include "zeek/script_opt/GenRDs.h"
 #include "zeek/script_opt/UseDefs.h"
+
 #include "zeek/script_opt/CPP/Compile.h"
 #include "zeek/script_opt/CPP/Func.h"
 
+#include "zeek/script_opt/ZAM/Compile.h"
+
 
 namespace zeek::detail {
 
@@ -31,21 +36,76 @@ static std::vector<FuncInfo> funcs;
 
 static ZAMCompiler* ZAM = nullptr;
 
+static bool generating_CPP = false;
+static std::string hash_dir;	// for storing hashes of previous compilations
 
-void optimize_func(ScriptFunc* f, std::shared_ptr<ProfileFunc> pf,
-			ScopePtr scope, StmtPtr& body,
-			AnalyOpt& analysis_options)
+static ScriptFuncPtr global_stmts;
+
+void analyze_func(ScriptFuncPtr f)
+	{
+	// Even if we're doing --optimize-only, we still track all functions
+	// here because the inliner will need the full list.
+	funcs.emplace_back(f, f->GetScope(), f->CurrentBody(),
+	                   f->CurrentPriority());
+	}
+
+const FuncInfo* analyze_global_stmts(Stmt* stmts)
+	{
+	// We ignore analysis_options.only_func - if it's in use, later
+	// logic will keep this function from being compiled, but it's handy
+	// now to enter it into "funcs" so we have a FuncInfo to return.
+
+	auto id = install_ID("<global-stmts>", GLOBAL_MODULE_NAME, true, false);
+	auto empty_args_t = make_intrusive<RecordType>(nullptr);
+	auto func_t = make_intrusive<FuncType>(empty_args_t, nullptr, FUNC_FLAVOR_FUNCTION);
+	id->SetType(func_t);
+
+	auto sc = current_scope();
+	std::vector<IDPtr> empty_inits;
+	StmtPtr stmts_p{NewRef{}, stmts};
+	global_stmts = make_intrusive<ScriptFunc>(id, stmts_p, empty_inits,
+	                                          sc->Length(), 0);
+
+	funcs.emplace_back(global_stmts, sc, stmts_p, 0);
+
+	return &funcs.back();
+	}
+
+
+static bool optimize_AST(ScriptFunc* f, std::shared_ptr<ProfileFunc>& pf,
+                         std::shared_ptr<Reducer>& rc, ScopePtr scope,
+                         StmtPtr& body)
+	{
+	pf = std::make_shared<ProfileFunc>(f, body, true);
+
+	// RD_Decorate reduced_rds(pf, f, scope, body);
+	GenIDDefs ID_defs(pf, f, scope, body);
+
+	if ( reporter->Errors() > 0 )
+		return false;
+
+	rc->SetReadyToOptimize();
+
+	auto new_body = rc->Reduce(body);
+
+	if ( reporter->Errors() > 0 )
+		return false;
+
+	if ( analysis_options.dump_xform )
+		printf("Optimized: %s\n", obj_desc(new_body.get()).c_str());
+
+	f->ReplaceBody(body, new_body);
+	body = new_body;
+
+	return true;
+	}
+
+static void optimize_func(ScriptFunc* f, std::shared_ptr<ProfileFunc> pf,
+                          ScopePtr scope, StmtPtr& body)
 	{
 	if ( reporter->Errors() > 0 )
 		return;
 
-	if ( ! analysis_options.activate )
-		return;
-
-	if ( analysis_options.only_func &&
-	     *analysis_options.only_func != f->Name() )
-		return;
-
 	if ( analysis_options.only_func )
 		printf("Original: %s\n", obj_desc(body.get()).c_str());
 
@@ -53,10 +113,12 @@ void optimize_func(ScriptFunc* f, std::shared_ptr<ProfileFunc> pf,
 		// We're not able to optimize this.
 		return;
 
-	if ( pf->NumWhenStmts() > 0 || pf->NumLambdas() > 0 )
+	const char* reason;
+	if ( ! is_ZAM_compilable(pf.get(), &reason) )
 		{
-		if ( analysis_options.only_func )
-			printf("Skipping analysis due to \"when\" statement or use of lambdas\n");
+		if ( analysis_options.report_uncompilable )
+			printf("Skipping compilation of %s due to %s\n",
+			       f->Name(), reason);
 		return;
 		}
 
@@ -77,59 +139,35 @@ void optimize_func(ScriptFunc* f, std::shared_ptr<ProfileFunc> pf,
 	if ( ! new_body->IsReduced(rc.get()) )
 		{
 		if ( non_reduced_perp )
-			printf("Reduction inconsistency for %s: %s\n", f->Name(),
+			reporter->InternalError("Reduction inconsistency for %s: %s\n", f->Name(),
 			       obj_desc(non_reduced_perp).c_str());
 		else
-			printf("Reduction inconsistency for %s\n", f->Name());
+			reporter->InternalError("Reduction inconsistency for %s\n", f->Name());
 		}
 
 	checking_reduction = false;
 
-	if ( analysis_options.only_func || analysis_options.dump_xform )
+	if ( analysis_options.dump_xform )
 		printf("Transformed: %s\n", obj_desc(new_body.get()).c_str());
 
 	f->ReplaceBody(body, new_body);
 	body = new_body;
 
-	if ( analysis_options.optimize_AST )
+	if ( analysis_options.optimize_AST &&
+	     ! optimize_AST(f, pf, rc, scope, body) )
 		{
-		pf = std::make_shared<ProfileFunc>(f, body, true);
-
-		RD_Decorate reduced_rds(pf);
-		reduced_rds.TraverseFunction(f, scope, body);
-
-		if ( reporter->Errors() > 0 )
-			{
-			pop_scope();
-			return;
-			}
-
-		rc->SetDefSetsMgr(reduced_rds.GetDefSetsMgr());
-
-		new_body = rc->Reduce(body);
-
-		if ( reporter->Errors() > 0 )
-			{
-			pop_scope();
-			return;
-			}
-
-		if ( analysis_options.only_func || analysis_options.dump_xform )
-			printf("Optimized: %s\n", obj_desc(new_body.get()).c_str());
-
-		f->ReplaceBody(body, new_body);
-		body = new_body;
+		pop_scope();
+		return;
 		}
 
 	// Profile the new body.
 	pf = std::make_shared<ProfileFunc>(f, body, true);
 
 	// Compute its reaching definitions.
-	RD_Decorate reduced_rds(pf);
+	// RD_Decorate reduced_rds(pf, f, scope, body);
+	GenIDDefs ID_defs(pf, f, scope, body);
 
-	reduced_rds.TraverseFunction(f, scope, body);
-
-	rc->SetDefSetsMgr(reduced_rds.GetDefSetsMgr());
+	rc->SetReadyToOptimize();
 
 	auto ud = std::make_shared<UseDefs>(body, rc);
 	ud->Analyze();
@@ -145,315 +183,290 @@ void optimize_func(ScriptFunc* f, std::shared_ptr<ProfileFunc> pf,
 		body = new_body;
 		}
 
-	int new_frame_size =
-		scope->Length() + rc->NumTemps() + rc->NumNewLocals();
+	int new_frame_size = scope->Length() + rc->NumTemps() +
+	                     rc->NumNewLocals();
 
 	if ( new_frame_size > f->FrameSize() )
 		f->SetFrameSize(new_frame_size);
 
+	if ( analysis_options.gen_ZAM_code )
+		{
+		ZAM = new ZAMCompiler(f, pf, scope, new_body, ud, rc);
+
+		new_body = ZAM->CompileBody();
+
+		if ( reporter->Errors() > 0 )
+			return;
+
+		if ( analysis_options.dump_ZAM )
+			ZAM->Dump();
+
+		f->ReplaceBody(body, new_body);
+		body = new_body;
+		}
+
 	pop_scope();
 	}
 
 
-FuncInfo::FuncInfo(ScriptFuncPtr _func, ScopePtr _scope, StmtPtr _body,
-                   int _priority)
-		: func(std::move(_func)), scope(std::move(_scope)),
-		  body(std::move(_body)), priority(_priority)
-	{}
-
-void FuncInfo::SetProfile(std::shared_ptr<ProfileFunc> _pf)
-	{ pf = std::move(_pf); }
-
-void analyze_func(ScriptFuncPtr f)
-	{
-	if ( analysis_options.only_func &&
-	     *analysis_options.only_func != f->Name() )
-		return;
-
-	funcs.emplace_back(f, f->GetScope(), f->CurrentBody(),
-	                   f->CurrentPriority());
-	}
-
-const FuncInfo* analyze_global_stmts(Stmt* stmts)
-	{
-	// We ignore analysis_options.only_func - if it's in use, later
-	// logic will keep this function from being compiled, but it's handy
-	// now to enter it into "funcs" so we have a FuncInfo to return.
-
-	auto id = install_ID("<global-stmts>", GLOBAL_MODULE_NAME, true, false);
-	auto empty_args_t = make_intrusive<RecordType>(nullptr);
-	auto func_t = make_intrusive<FuncType>(empty_args_t, nullptr, FUNC_FLAVOR_FUNCTION);
-	id->SetType(func_t);
-
-	auto sc = current_scope();
-	std::vector<IDPtr> empty_inits;
-	StmtPtr stmts_p{NewRef{}, stmts};
-	auto sf = make_intrusive<ScriptFunc>(id, stmts_p, empty_inits, sc->Length(), 0);
-
-	funcs.emplace_back(sf, sc, stmts_p, 0);
-
-	return &funcs.back();
-	}
-
 static void check_env_opt(const char* opt, bool& opt_flag)
 	{
 	if ( getenv(opt) )
 		opt_flag = true;
 	}
 
-void analyze_scripts()
+static void init_options()
 	{
-	static bool did_init = false;
-	static std::string hash_dir;
+	auto hd = getenv("ZEEK_HASH_DIR");
+	if ( hd )
+		hash_dir = std::string(hd) + "/";
 
-	bool generating_CPP = false;
+	// ZAM-related options.
+	check_env_opt("ZEEK_DUMP_XFORM", analysis_options.dump_xform);
+	check_env_opt("ZEEK_DUMP_UDS", analysis_options.dump_uds);
+	check_env_opt("ZEEK_INLINE", analysis_options.inliner);
+	check_env_opt("ZEEK_OPT", analysis_options.optimize_AST);
+	check_env_opt("ZEEK_XFORM", analysis_options.activate);
+	check_env_opt("ZEEK_ZAM", analysis_options.gen_ZAM);
+	check_env_opt("ZEEK_COMPILE_ALL", analysis_options.compile_all);
+	check_env_opt("ZEEK_ZAM_CODE", analysis_options.gen_ZAM_code);
+	check_env_opt("ZEEK_NO_ZAM_OPT", analysis_options.no_ZAM_opt);
+	check_env_opt("ZEEK_DUMP_ZAM", analysis_options.dump_ZAM);
+	check_env_opt("ZEEK_PROFILE", analysis_options.profile_ZAM);
 
-	if ( ! did_init )
+	// Compile-to-C++-related options.
+	check_env_opt("ZEEK_ADD_CPP", analysis_options.add_CPP);
+	check_env_opt("ZEEK_UPDATE_CPP", analysis_options.update_CPP);
+	check_env_opt("ZEEK_GEN_CPP", analysis_options.gen_CPP);
+	check_env_opt("ZEEK_GEN_STANDALONE_CPP",
+		      analysis_options.gen_standalone_CPP);
+	check_env_opt("ZEEK_COMPILE_ALL", analysis_options.compile_all);
+	check_env_opt("ZEEK_REPORT_CPP", analysis_options.report_CPP);
+	check_env_opt("ZEEK_USE_CPP", analysis_options.use_CPP);
+
+	if ( analysis_options.gen_standalone_CPP )
+		analysis_options.gen_CPP = true;
+
+	if ( analysis_options.gen_CPP )
 		{
-		auto hd = getenv("ZEEK_HASH_DIR");
-		if ( hd )
-			hash_dir = std::string(hd) + "/";
-
-		check_env_opt("ZEEK_DUMP_XFORM", analysis_options.dump_xform);
-		check_env_opt("ZEEK_DUMP_UDS", analysis_options.dump_uds);
-		check_env_opt("ZEEK_INLINE", analysis_options.inliner);
-		check_env_opt("ZEEK_OPT", analysis_options.optimize_AST);
-		check_env_opt("ZEEK_XFORM", analysis_options.activate);
-		check_env_opt("ZEEK_ADD_CPP", analysis_options.add_CPP);
-		check_env_opt("ZEEK_UPDATE_CPP", analysis_options.update_CPP);
-		check_env_opt("ZEEK_GEN_CPP", analysis_options.gen_CPP);
-		check_env_opt("ZEEK_GEN_STANDALONE_CPP",
-		              analysis_options.gen_standalone_CPP);
-		check_env_opt("ZEEK_COMPILE_ALL", analysis_options.compile_all);
-		check_env_opt("ZEEK_REPORT_CPP", analysis_options.report_CPP);
-		check_env_opt("ZEEK_USE_CPP", analysis_options.use_CPP);
-
-		if ( analysis_options.gen_standalone_CPP )
-			analysis_options.gen_CPP = true;
-
-		if ( analysis_options.gen_CPP )
+		if ( analysis_options.add_CPP )
 			{
-			if ( analysis_options.add_CPP )
-				{
-				reporter->Warning("gen-C++ incompatible with add-C++");
-				analysis_options.add_CPP = false;
-				}
-
-			if ( analysis_options.update_CPP )
-				{
-				reporter->Warning("gen-C++ incompatible with update-C++");
-				analysis_options.update_CPP = false;
-				}
-
-			generating_CPP = true;
+			reporter->Warning("gen-C++ incompatible with add-C++");
+			analysis_options.add_CPP = false;
 			}
 
-		if ( analysis_options.update_CPP || analysis_options.add_CPP )
-			generating_CPP = true;
-
-		if ( analysis_options.use_CPP && generating_CPP )
+		if ( analysis_options.update_CPP )
 			{
-			reporter->Error("generating C++ incompatible with using C++");
-			exit(1);
+			reporter->Warning("gen-C++ incompatible with update-C++");
+			analysis_options.update_CPP = false;
 			}
 
-		if ( analysis_options.use_CPP && ! CPP_init_hook )
-			{
-			reporter->Error("no C++ functions available to use");
-			exit(1);
-			}
-
-		auto usage = getenv("ZEEK_USAGE_ISSUES");
-
-		if ( usage )
-			analysis_options.usage_issues = atoi(usage) > 1 ? 2 : 1;
-
-		if ( ! analysis_options.only_func )
-			{
-			auto zo = getenv("ZEEK_ONLY");
-			if ( zo )
-				analysis_options.only_func = zo;
-			}
-
-		if ( analysis_options.only_func ||
-		     analysis_options.optimize_AST ||
-		     analysis_options.usage_issues > 0 )
-			analysis_options.activate = true;
-
-		did_init = true;
+		generating_CPP = true;
 		}
 
-	if ( ! analysis_options.activate && ! analysis_options.inliner &&
-	     ! generating_CPP && ! analysis_options.report_CPP &&
-	     ! analysis_options.use_CPP )
-		// Avoid profiling overhead.
-		return;
+	if ( analysis_options.update_CPP || analysis_options.add_CPP )
+		generating_CPP = true;
 
-	// Now that everything's parsed and BiF's have been initialized,
-	// profile the functions.
-	auto pfs = std::make_unique<ProfileFuncs>(funcs, is_CPP_compilable, false);
+	if ( analysis_options.use_CPP && generating_CPP )
+		reporter->FatalError("generating C++ incompatible with using C++");
 
-	if ( CPP_init_hook )
-		(*CPP_init_hook)();
+	if ( analysis_options.use_CPP && ! CPP_init_hook )
+		reporter->FatalError("no C++ functions available to use");
 
-	if ( analysis_options.report_CPP )
+	auto usage = getenv("ZEEK_USAGE_ISSUES");
+
+	if ( usage )
+		analysis_options.usage_issues = atoi(usage) > 1 ? 2 : 1;
+
+	if ( ! analysis_options.only_func )
 		{
-		if ( ! CPP_init_hook )
-			{
-			printf("no C++ script bodies available\n");
-			exit(0);
-			}
+		auto zo = getenv("ZEEK_ONLY");
+		if ( zo )
+			analysis_options.only_func = zo;
+		}
 
-		printf("C++ script bodies available that match loaded scripts:\n");
+	if ( analysis_options.gen_ZAM )
+		{
+		analysis_options.gen_ZAM_code = true;
+		analysis_options.inliner = true;
+		analysis_options.optimize_AST = true;
+		}
 
-		std::unordered_set<unsigned long long> already_reported;
+	if ( analysis_options.dump_ZAM )
+		analysis_options.gen_ZAM_code = true;
 
-		for ( auto& f : funcs )
-			{
-			auto name = f.Func()->Name();
-			auto hash = f.Profile()->HashVal();
-			bool have = compiled_scripts.count(hash) > 0;
-			auto specific = "";
+	if ( analysis_options.only_func )
+		{
+		// Note, this comes after the statement above because for
+		// --optimize-only we don't necessarily want to go all
+		// the way to *generating* ZAM code, though we'll want to
+		// dump it *if* we generate it.
+		analysis_options.dump_xform = analysis_options.dump_ZAM = true;
 
-			if ( ! have )
-				{
-				hash = script_specific_hash(f.Body(), hash);
-				have = compiled_scripts.count(hash) > 0;
-				if ( have )
-					specific = " - specific";
-				}
+		if ( analysis_options.gen_ZAM_code || generating_CPP )
+			analysis_options.report_uncompilable = true;
+		}
 
-			printf("script function %s (hash %llu%s): %s\n",
-				name, hash, specific, have ? "yes" : "no");
+	if ( analysis_options.report_uncompilable &&
+	     ! analysis_options.gen_ZAM_code && ! generating_CPP )
+		reporter->FatalError("report-uncompilable requires generation of ZAM or C++");
 
-			if ( have )
-				already_reported.insert(hash);
-			}
-
-		printf("\nAdditional C++ script bodies available:\n");
-		int addl = 0;
-		for ( const auto& s : compiled_scripts )
-			if ( already_reported.count(s.first) == 0 )
-				{
-				printf("%s body (hash %llu)\n",
-					s.second.body->Name().c_str(), s.first);
-				++addl;
-				}
-
-		if ( addl == 0 )
-			printf("(none)\n");
+	if ( analysis_options.only_func ||
+	     analysis_options.optimize_AST ||
+	     analysis_options.gen_ZAM_code ||
+	     analysis_options.usage_issues > 0 )
+		analysis_options.activate = true;
+	}
 
+static void report_CPP()
+	{
+	if ( ! CPP_init_hook )
+		{
+		printf("no C++ script bodies available\n");
 		exit(0);
 		}
 
-	if ( analysis_options.use_CPP )
+	printf("C++ script bodies available that match loaded scripts:\n");
+
+	std::unordered_set<unsigned long long> already_reported;
+
+	for ( auto& f : funcs )
 		{
-		for ( auto& f : funcs )
+		auto name = f.Func()->Name();
+		auto hash = f.Profile()->HashVal();
+		bool have = compiled_scripts.count(hash) > 0;
+		auto specific = "";
+
+		if ( ! have )
 			{
-			auto hash = f.Profile()->HashVal();
-			auto s = compiled_scripts.find(hash);
-
-			if ( s == compiled_scripts.end() )
-				{ // Look for script-specific body.
-				hash = script_specific_hash(f.Body(), hash);
-				s = compiled_scripts.find(hash);
-				}
-
-			if ( s != compiled_scripts.end() )
-				{
-				auto b = s->second.body;
-				b->SetHash(hash);
-
-				// We may have already updated the body if
-				// we're using code compiled for standalone.
-				if ( f.Body()->Tag() != STMT_CPP )
-					{
-					auto func = f.Func();
-					if ( added_bodies[func->Name()].count(hash) > 0 )
-						// We've already added the
-						// replacement.  Delete orig.
-						func->ReplaceBody(f.Body(), nullptr);
-					else
-						func->ReplaceBody(f.Body(), b);
-
-					f.SetBody(b);
-					}
-
-				for ( auto& e : s->second.events )
-					{
-					auto h = event_registry->Register(e);
-					h->SetUsed();
-					}
-				}
+			hash = script_specific_hash(f.Body(), hash);
+			have = compiled_scripts.count(hash) > 0;
+			if ( have )
+				specific = " - specific";
 			}
 
-		// Now that we've loaded all of the compiled scripts
-		// relevant for the AST, activate standalone ones.
-		for ( auto cb : standalone_activations )
-			(*cb)();
+		printf("script function %s (hash %llu%s): %s\n",
+			name, hash, specific, have ? "yes" : "no");
+
+		if ( have )
+			already_reported.insert(hash);
 		}
 
-	if ( generating_CPP )
-		{
-		const auto hash_name = hash_dir + "CPP-hashes";
+	printf("\nAdditional C++ script bodies available:\n");
 
-		auto hm = std::make_unique<CPPHashManager>(hash_name.c_str(),
-						analysis_options.add_CPP);
-
-		if ( ! analysis_options.gen_CPP )
+	int addl = 0;
+	for ( const auto& s : compiled_scripts )
+		if ( already_reported.count(s.first) == 0 )
 			{
+			printf("%s body (hash %llu)\n",
+				s.second.body->Name().c_str(), s.first);
+			++addl;
+			}
+
+	if ( addl == 0 )
+		printf("(none)\n");
+	}
+
+static void use_CPP()
+	{
+	for ( auto& f : funcs )
+		{
+		auto hash = f.Profile()->HashVal();
+		auto s = compiled_scripts.find(hash);
+
+		if ( s == compiled_scripts.end() )
+			{ // Look for script-specific body.
+			hash = script_specific_hash(f.Body(), hash);
+			s = compiled_scripts.find(hash);
+			}
+
+		if ( s != compiled_scripts.end() )
+			{
+			auto b = s->second.body;
+			b->SetHash(hash);
+
+			// We may have already updated the body if
+			// we're using code compiled for standalone.
+			if ( f.Body()->Tag() != STMT_CPP )
+				{
+				auto func = f.Func();
+				if ( added_bodies[func->Name()].count(hash) > 0 )
+					// We've already added the
+					// replacement.  Delete orig.
+					func->ReplaceBody(f.Body(), nullptr);
+				else
+					func->ReplaceBody(f.Body(), b);
+
+				f.SetBody(b);
+				}
+
+			for ( auto& e : s->second.events )
+				{
+				auto h = event_registry->Register(e);
+				h->SetUsed();
+				}
+			}
+		}
+
+	// Now that we've loaded all of the compiled scripts
+	// relevant for the AST, activate standalone ones.
+	for ( auto cb : standalone_activations )
+		(*cb)();
+	}
+
+static void generate_CPP(std::unique_ptr<ProfileFuncs>& pfs)
+	{
+	const auto hash_name = hash_dir + "CPP-hashes";
+
+	auto hm = std::make_unique<CPPHashManager>(hash_name.c_str(),
+	                                           analysis_options.add_CPP);
+
+	if ( analysis_options.gen_CPP )
+		{
+		if ( analysis_options.only_func )
+			{ // deactivate all functions except the target one
 			for ( auto& func : funcs )
 				{
-				auto hash = func.Profile()->HashVal();
-				if ( compiled_scripts.count(hash) > 0 ||
-				     hm->HasHash(hash) )
+				auto fn = func.Func()->Name();
+				if ( *analysis_options.only_func != fn )
 					func.SetSkip(true);
 				}
-
-			// Now that we've presumably marked a lot of functions
-			// as skippable, recompute the global profile.
-			pfs = std::make_unique<ProfileFuncs>(funcs, is_CPP_compilable, false);
+			}
+		}
+	else
+		{ // doing add-C++ instead, so look for previous compilations
+		for ( auto& func : funcs )
+			{
+			auto hash = func.Profile()->HashVal();
+			if ( compiled_scripts.count(hash) > 0 ||
+			     hm->HasHash(hash) )
+				func.SetSkip(true);
 			}
 
-		const auto gen_name = hash_dir + "CPP-gen.cc";
-		const auto addl_name = hash_dir + "CPP-gen-addl.h";
-
-		CPPCompile cpp(funcs, *pfs, gen_name, addl_name, *hm,
-			       analysis_options.gen_CPP ||
-			       analysis_options.update_CPP,
-			       analysis_options.gen_standalone_CPP);
-
-		exit(0);
+		// Now that we've presumably marked a lot of functions
+		// as skippable, recompute the global profile.
+		pfs = std::make_unique<ProfileFuncs>(funcs, is_CPP_compilable, false);
 		}
 
-	if ( analysis_options.usage_issues > 0 && analysis_options.optimize_AST )
-		{
-		fprintf(stderr, "warning: \"-O optimize-AST\" option is incompatible with -u option, deactivating optimization\n");
-		analysis_options.optimize_AST = false;
-		}
+	const auto gen_name = hash_dir + "CPP-gen.cc";
+	const auto addl_name = hash_dir + "CPP-gen-addl.h";
 
-	// Re-profile the functions, this time without worrying about
-	// compatibility with compilation to C++.  Note that the first
-	// profiling pass above may have marked some of the functions
-	// as to-skip, so first clear those markings.  Once we have
-	// full compile-to-C++ and ZAM support for all Zeek language
-	// features, we can remove the re-profiling here.
-	for ( auto& f : funcs )
-		f.SetSkip(false);
-
-	pfs = std::make_unique<ProfileFuncs>(funcs, nullptr, true);
+	CPPCompile cpp(funcs, *pfs, gen_name, addl_name, *hm,
+		       analysis_options.gen_CPP || analysis_options.update_CPP,
+		       analysis_options.gen_standalone_CPP,
+		       analysis_options.report_uncompilable);
+	}
 
+static void find_when_funcs(std::unique_ptr<ProfileFuncs>& pfs,
+                            std::unordered_set<const ScriptFunc*>& when_funcs)
+	{
 	// Figure out which functions either directly or indirectly
 	// appear in "when" clauses.
 
-	// Final set of functions involved in "when" clauses.
-	std::unordered_set<const ScriptFunc*> when_funcs;
-
 	// Which functions we still need to analyze.
 	std::unordered_set<const ScriptFunc*> when_funcs_to_do;
 
 	for ( auto& f : funcs )
-		{
 		if ( f.Profile()->WhenCalls().size() > 0 )
 			{
 			when_funcs.insert(f.Func());
@@ -463,18 +476,7 @@ void analyze_scripts()
 				ASSERT(pfs->FuncProf(bf));
 				when_funcs_to_do.insert(bf);
 				}
-
-#ifdef NOT_YET
-			if ( analysis_options.report_uncompilable )
-				{
-				ODesc d;
-				f.ScriptFunc()->AddLocation(&d);
-				printf("%s cannot be compiled due to use of \"when\" statement (%s)\n",
-					f.ScriptFunc()->Name(), d.Description());
-				}
-#endif	// NOT_YET
 			}
-		}
 
 	// Set of new functions to put on to-do list.  Separate from
 	// the to-do list itself so we don't modify it while iterating
@@ -501,12 +503,41 @@ void analyze_scripts()
 		when_funcs_to_do = new_to_do;
 		new_to_do.clear();
 		}
+	}
 
+static void analyze_scripts_for_ZAM(std::unique_ptr<ProfileFuncs>& pfs)
+	{
+	if ( analysis_options.usage_issues > 0 &&
+	     analysis_options.optimize_AST )
+		{
+		fprintf(stderr, "warning: \"-O optimize-AST\" option is incompatible with -u option, deactivating optimization\n");
+		analysis_options.optimize_AST = false;
+		}
+
+	// Re-profile the functions, now without worrying about compatibility
+	// with compilation to C++.  Note that the first profiling pass earlier
+	// may have marked some of the functions as to-skip, so first clear
+	// those markings.  Once we have full compile-to-C++ and ZAM support
+	// for all Zeek language features, we can remove the re-profiling here.
+	for ( auto& f : funcs )
+		f.SetSkip(false);
+
+	pfs = std::make_unique<ProfileFuncs>(funcs, nullptr, true);
+
+	// set of functions involved (directly or indirectly) in "when"
+	// clauses.
+	std::unordered_set<const ScriptFunc*> when_funcs;
+
+	find_when_funcs(pfs, when_funcs);
+
+	bool report_recursive = analysis_options.report_recursive;
 	std::unique_ptr<Inliner> inl;
 	if ( analysis_options.inliner )
-		inl = std::make_unique<Inliner>(funcs, analysis_options.report_recursive);
+		inl = std::make_unique<Inliner>(funcs, report_recursive);
 
 	if ( ! analysis_options.activate )
+		// Some --optimize options stop short of AST transformations,
+		// for development/debugging purposes.
 		return;
 
 	// The following tracks inlined functions that are also used
@@ -515,6 +546,9 @@ void analyze_scripts()
 	// since it won't be consulted in that case.
 	std::unordered_set<Func*> func_used_indirectly;
 
+	if ( global_stmts )
+		func_used_indirectly.insert(global_stmts.get());
+
 	if ( inl )
 		{
 		for ( auto& f : funcs )
@@ -540,23 +574,67 @@ void analyze_scripts()
 		{
 		auto func = f.Func();
 
-		if ( ! analysis_options.compile_all &&
-		     inl && inl->WasInlined(func) &&
-		     func_used_indirectly.count(func) == 0 )
-			// No need to compile as it won't be
-			// called directly.
-			continue;
+		if ( analysis_options.only_func )
+			{
+			if ( *analysis_options.only_func != func->Name() )
+				continue;
+			}
 
-		if ( when_funcs.count(func) > 0 )
-			// We don't try to compile these.
+		else if ( ! analysis_options.compile_all &&
+		          inl && inl->WasInlined(func) &&
+		          func_used_indirectly.count(func) == 0 )
+			// No need to compile as it won't be called directly.
 			continue;
 
 		auto new_body = f.Body();
-		optimize_func(func, f.ProfilePtr(), f.Scope(), new_body,
-		              analysis_options);
+		optimize_func(func, f.ProfilePtr(), f.Scope(), new_body);
 		f.SetBody(new_body);
 		}
 	}
 
+void analyze_scripts()
+	{
+	static bool did_init = false;
+
+	if ( ! did_init )
+		{
+		init_options();
+		did_init = true;
+		}
+
+	if ( ! analysis_options.activate && ! analysis_options.inliner &&
+	     ! generating_CPP && ! analysis_options.report_CPP &&
+	     ! analysis_options.use_CPP )
+		// No work to do, avoid profiling overhead.
+		return;
+
+	// Now that everything's parsed and BiF's have been initialized,
+	// profile the functions.
+	auto pfs = std::make_unique<ProfileFuncs>(funcs, is_CPP_compilable,
+	                                          false);
+
+	if ( CPP_init_hook )
+		(*CPP_init_hook)();
+
+	if ( analysis_options.report_CPP )
+		{
+		report_CPP();
+		exit(0);
+		}
+
+	if ( analysis_options.use_CPP )
+		use_CPP();
+
+	if ( generating_CPP )
+		{
+		generate_CPP(pfs);
+		exit(0);
+		}
+
+	// At this point we're done with C++ considerations, so instead
+	// are compiling to ZAM.
+	analyze_scripts_for_ZAM(pfs);
+	}
+
 
 } // namespace zeek::detail
diff --git a/src/script_opt/ScriptOpt.h b/src/script_opt/ScriptOpt.h
index 5de3f0e507..f672044e1d 100644
--- a/src/script_opt/ScriptOpt.h
+++ b/src/script_opt/ScriptOpt.h
@@ -125,7 +125,11 @@ using ScriptFuncPtr = IntrusivePtr<ScriptFunc>;
 // Info we need for tracking an instance of a function.
 class FuncInfo {
 public:
-	FuncInfo(ScriptFuncPtr func, ScopePtr scope, StmtPtr body, int priority);
+	FuncInfo(ScriptFuncPtr _func, ScopePtr _scope, StmtPtr _body,
+	         int _priority)
+	: func(std::move(_func)), scope(std::move(_scope)),
+	  body(std::move(_body)), priority(_priority)
+		{}
 
 	ScriptFunc* Func() const		{ return func.get(); }
 	const ScriptFuncPtr& FuncPtr() const	{ return func; }
@@ -134,11 +138,11 @@ public:
 	int Priority() const			{ return priority; }
 	const ProfileFunc* Profile() const	{ return pf.get(); }
 	std::shared_ptr<ProfileFunc> ProfilePtr() const	{ return pf; }
-	const std::string& SaveFile() const	{ return save_file; }
 
 	void SetBody(StmtPtr new_body)	{ body = std::move(new_body); }
-	void SetProfile(std::shared_ptr<ProfileFunc> _pf);
-	void SetSaveFile(std::string _sf)	{ save_file = std::move(_sf); }
+	// void SetProfile(std::shared_ptr<ProfileFunc> _pf);
+	void SetProfile(std::shared_ptr<ProfileFunc> _pf)
+		{ pf = std::move(_pf); }
 
 	// The following provide a way of marking FuncInfo's as
 	// should-be-skipped for script optimization, generally because
@@ -156,10 +160,6 @@ protected:
 
 	// Whether to skip optimizing this function.
 	bool skip = false;
-
-	// If we're saving this function in a file, this is the name
-	// of the file to use.
-	std::string save_file;
 };
 
 
diff --git a/src/script_opt/Stmt.cc b/src/script_opt/Stmt.cc
index 892028f7fa..cb96bfa61f 100644
--- a/src/script_opt/Stmt.cc
+++ b/src/script_opt/Stmt.cc
@@ -8,6 +8,7 @@
 #include "zeek/Reporter.h"
 #include "zeek/Desc.h"
 #include "zeek/Traverse.h"
+#include "zeek/script_opt/IDOptInfo.h"
 #include "zeek/script_opt/Reduce.h"
 
 
@@ -34,6 +35,8 @@ StmtPtr Stmt::Reduce(Reducer* c)
 		return null;
 		}
 
+	c->SetCurrStmt(this);
+
 	return DoReduce(c);
 	}
 
@@ -846,7 +849,9 @@ bool StmtList::ReduceStmt(int& s_i, StmtPList* f_stmts, Reducer* c)
 			auto& s_i_succ = Stmts()[s_i + 1];
 
 			// Don't reduce s_i_succ.  If it's what we're
-			// looking for, it's already reduced.
+			// looking for, it's already reduced.  Plus
+			// that's what Reducer::MergeStmts (not that
+			// it really matters, per the comment there).
 			auto merge = c->MergeStmts(var, rhs, s_i_succ);
 			if ( merge )
 				{
@@ -1014,10 +1019,19 @@ StmtPtr CatchReturnStmt::DoReduce(Reducer* c)
 			return make_intrusive<NullStmt>();
 			}
 
-		auto assign = make_intrusive<AssignExpr>(ret_var->Duplicate(),
-							ret_e->Duplicate(),
+		auto rv_dup = ret_var->Duplicate();
+		auto ret_e_dup = ret_e->Duplicate();
+
+		auto assign = make_intrusive<AssignExpr>(rv_dup, ret_e_dup,
 							false);
 		assign_stmt = make_intrusive<ExprStmt>(assign);
+
+		if ( ret_e_dup->Tag() == EXPR_CONST )
+			{
+			auto c = ret_e_dup->AsConstExpr();
+			rv_dup->AsNameExpr()->Id()->GetOptInfo()->SetConst(c);
+			}
+
 		return assign_stmt;
 		}
 
diff --git a/src/script_opt/TempVar.cc b/src/script_opt/TempVar.cc
index b385bb432a..cd4924fed8 100644
--- a/src/script_opt/TempVar.cc
+++ b/src/script_opt/TempVar.cc
@@ -14,28 +14,15 @@ TempVar::TempVar(int num, const TypePtr& t, ExprPtr _rhs) : type(t)
 	rhs = std::move(_rhs);
 	}
 
-void TempVar::SetAlias(IDPtr _alias, const DefPoints* _dps)
+void TempVar::SetAlias(IDPtr _alias)
 	{
 	if ( alias )
 		reporter->InternalError("Re-aliasing a temporary");
 
-	if ( ! _dps )
-		{
-		printf("trying to alias %s to %s\n", name.c_str(), _alias->Name());
-		reporter->InternalError("Empty dps for alias");
-		}
-
 	if ( alias == id )
 		reporter->InternalError("Creating alias loop");
 
 	alias = std::move(_alias);
-	dps = _dps;
-	}
-
-void TempVar::SetDPs(const DefPoints* _dps)
-	{
-	ASSERT(_dps->length() == 1);
-	dps = _dps;
 	}
 
 } // zeek::detail
diff --git a/src/script_opt/TempVar.h b/src/script_opt/TempVar.h
index 446327c1bb..4b6920eccc 100644
--- a/src/script_opt/TempVar.h
+++ b/src/script_opt/TempVar.h
@@ -9,6 +9,7 @@
 
 #include "zeek/ID.h"
 #include "zeek/Expr.h"
+#include "zeek/script_opt/IDOptInfo.h"
 #include "zeek/script_opt/ReachingDefs.h"
 
 namespace zeek::detail {
@@ -22,21 +23,24 @@ public:
 	const Expr* RHS() const		{ return rhs.get(); }
 
 	IDPtr Id() const	{ return id; }
-	void SetID(IDPtr _id)	{ id = std::move(_id); }
+	void SetID(IDPtr _id)
+		{
+		id = std::move(_id);
+		id->GetOptInfo()->SetTemp();
+		}
 	void Deactivate()	{ active = false; }
 	bool IsActive() const	{ return active; }
 
 	// Associated constant expression, if any.
-	const ConstExpr* Const() const	{ return const_expr; }
+	const ConstExpr* Const() const	{ return id->GetOptInfo()->Const(); }
 
 	// The most use of "const" in any single line in the Zeek
 	// codebase :-P ... though only by one!
-	void SetConst(const ConstExpr* _const) { const_expr = _const; }
+	void SetConst(const ConstExpr* _const)
+		{ id->GetOptInfo()->SetConst(_const); }
 
 	IDPtr Alias() const			{ return alias; }
-	const DefPoints* DPs() const		{ return dps; }
-	void SetAlias(IDPtr id, const DefPoints* dps);
-	void SetDPs(const DefPoints* _dps);
+	void SetAlias(IDPtr id);
 
 	const RDPtr& MaxRDs() const	{ return max_rds; }
 	void SetMaxRDs(RDPtr rds)	{ max_rds = std::move(rds); }
@@ -47,9 +51,7 @@ protected:
 	const TypePtr& type;
 	ExprPtr rhs;
 	bool active = true;
-	const ConstExpr* const_expr = nullptr;
 	IDPtr alias;
-	const DefPoints* dps = nullptr;
 	RDPtr max_rds;
 };