diff --git a/auxil/gen-zam b/auxil/gen-zam
index 16bcb175dd..113acbada6 160000
--- a/auxil/gen-zam
+++ b/auxil/gen-zam
@@ -1 +1 @@
-Subproject commit 16bcb175dddaa1cb6e3df7e1951287a29a74164e
+Subproject commit 113acbada6478a610dfa639f34ef6662fbb671d9
diff --git a/src/script_opt/ProfileFunc.cc b/src/script_opt/ProfileFunc.cc
index dddcfd0e19..6d4072473c 100644
--- a/src/script_opt/ProfileFunc.cc
+++ b/src/script_opt/ProfileFunc.cc
@@ -522,6 +522,12 @@ void ProfileFunc::TrackID(const ID* id) {
         // Already tracked.
         return;
 
+	if ( id->IsGlobal() )
+		{
+                globals.insert(id);
+                all_globals.insert(id);
+		}
+
     ordered_ids.push_back(id);
 }
 
diff --git a/src/script_opt/ZAM/Compile.h b/src/script_opt/ZAM/Compile.h
index 2ee365e64c..a8b262dfac 100644
--- a/src/script_opt/ZAM/Compile.h
+++ b/src/script_opt/ZAM/Compile.h
@@ -167,8 +167,14 @@ private:
     void PushFallThroughs() { PushGoTos(fallthroughs); }
     void PushCatchReturns() { PushGoTos(catches); }
 
-    void ResolveNexts(const InstLabel l) { ResolveGoTos(nexts, l); }
-    void ResolveBreaks(const InstLabel l) { ResolveGoTos(breaks, l); }
+    void ResolveNexts(const InstLabel l) {
+        ResolveGoTos(nexts, l);
+        AddCFT(l, CFT_NEXT);
+    }
+    void ResolveBreaks(const InstLabel l) {
+        ResolveGoTos(breaks, l);
+        AddCFT(l, CFT_BREAK);
+    }
     void ResolveFallThroughs(const InstLabel l) { ResolveGoTos(fallthroughs, l); }
     void ResolveCatchReturns(const InstLabel l) { ResolveGoTos(catches, l); }
 
@@ -319,6 +325,9 @@ private:
     const ZAMStmt ErrorStmt();
     const ZAMStmt LastInst();
 
+    // Adds control flow information to an instruction.
+    void AddCFT(ZInstI* inst, ControlFlowType cft);
+
     // Returns a handle to state associated with building
     // up a list of values.
     OpaqueVals* BuildVals(const ListExprPtr&);
diff --git a/src/script_opt/ZAM/Driver.cc b/src/script_opt/ZAM/Driver.cc
index b37e033d43..d77936cfeb 100644
--- a/src/script_opt/ZAM/Driver.cc
+++ b/src/script_opt/ZAM/Driver.cc
@@ -203,6 +203,7 @@ StmtPtr ZAMCompiler::CompileBody() {
 
     auto zb = make_intrusive<ZBody>(fname, this);
     zb->SetInsts(insts2);
+    zb->SetLocationInfo(body->GetLocationInfo());
 
     // Could erase insts1 here to recover memory, but it's handy
     // for debugging.
diff --git a/src/script_opt/ZAM/Low-Level.cc b/src/script_opt/ZAM/Low-Level.cc
index 4898393eaa..fa6c95c87c 100644
--- a/src/script_opt/ZAM/Low-Level.cc
+++ b/src/script_opt/ZAM/Low-Level.cc
@@ -20,9 +20,15 @@ bool ZAMCompiler::NullStmtOK() const {
 
 const ZAMStmt ZAMCompiler::EmptyStmt() { return ZAMStmt(insts1.size() - 1); }
 
+const ZAMStmt ZAMCompiler::ErrorStmt() { return ZAMStmt(0); }
+
 const ZAMStmt ZAMCompiler::LastInst() { return ZAMStmt(insts1.size() - 1); }
 
-const ZAMStmt ZAMCompiler::ErrorStmt() { return ZAMStmt(0); }
+void ZAMCompiler::AddCFT(ZInstI* inst, ControlFlowType cft) {
+    if ( ! inst->aux )
+        inst->aux = new ZInstAux(0);
+    inst->aux->cft.insert(cft);
+}
 
 OpaqueVals* ZAMCompiler::BuildVals(const ListExprPtr& l) { return new OpaqueVals(InternalBuildVals(l.get())); }
 
diff --git a/src/script_opt/ZAM/README.md b/src/script_opt/ZAM/README.md
index dc9c62da68..90afbdbf09 100644
--- a/src/script_opt/ZAM/README.md
+++ b/src/script_opt/ZAM/README.md
@@ -100,6 +100,7 @@ issues:
 |`profile-ZAM`	|	Generate to "zprof.out" a ZAM execution profile. (Requires configuring with `--enable-ZAM-profiling` or `--enable-debug`.)|
 |`report-recursive`	|	Report on recursive functions and exit.|
 |`report-uncompilable`	|	Report on uncompilable functions and exit. For ZAM, all functions should be compilable.|
+|`validate-ZAM`		|	Perform internal validation of ZAM instructions and exit.|
 |`xform`		|	Transform scripts to "reduced" form.|
 
 <a name="ZAM-profiling"></a>
diff --git a/src/script_opt/ZAM/Stmt.cc b/src/script_opt/ZAM/Stmt.cc
index f5af4b7710..2f80add1d9 100644
--- a/src/script_opt/ZAM/Stmt.cc
+++ b/src/script_opt/ZAM/Stmt.cc
@@ -145,13 +145,22 @@ const ZAMStmt ZAMCompiler::IfElse(const Expr* e, const Stmt* s1, const Stmt* s2)
     else
         cond_stmt = GenCond(e, branch_v);
 
+    auto cft = (s1 && s2) ? CFT_IF_ELSE : (s1 ? CFT_IF : CFT_IF_NOT);
+    AddCFT(insts1.back(), cft);
+
     if ( s1 ) {
         auto s1_end = CompileStmt(s1);
+        AddCFT(insts1.back(), CFT_BLOCK_END);
+
         if ( s2 ) {
             auto branch_after_s1 = GoToStub();
+            auto else_start = insts1.size();
             auto s2_end = CompileStmt(s2);
+
             SetV(cond_stmt, GoToTargetBeyond(branch_after_s1), branch_v);
             SetGoTo(branch_after_s1, GoToTargetBeyond(s2_end));
+            AddCFT(insts1[else_start], CFT_ELSE);
+            AddCFT(insts1.back(), CFT_BLOCK_END);
 
             return s2_end;
         }
@@ -164,6 +173,7 @@ const ZAMStmt ZAMCompiler::IfElse(const Expr* e, const Stmt* s1, const Stmt* s2)
 
     // Only the else clause is non-empty.
     auto s2_end = CompileStmt(s2);
+    AddCFT(insts1.back(), CFT_BLOCK_END);
 
     // For complex conditionals, we need to invert their sense since
     // we're switching to "if ( ! cond ) s2".
@@ -705,12 +715,17 @@ const ZAMStmt ZAMCompiler::While(const Stmt* cond_stmt, const Expr* cond, const
     else
         cond_IF = GenCond(cond, branch_v);
 
+    AddCFT(insts1[head.stmt_num], CFT_LOOP);
+    AddCFT(insts1[cond_IF.stmt_num], CFT_LOOP_COND);
+
     PushNexts();
     PushBreaks();
 
     if ( body && body->Tag() != STMT_NULL )
         (void)CompileStmt(body);
 
+    AddCFT(insts1.back(), CFT_BLOCK_END);
+
     auto tail = GoTo(GoToTarget(head));
 
     auto beyond_tail = GoToTargetBeyond(tail);
@@ -730,17 +745,25 @@ const ZAMStmt ZAMCompiler::CompileFor(const ForStmt* f) {
     PushNexts();
     PushBreaks();
 
+    auto head = StartingBlock();
+    ZAMStmt z;
+
     if ( et == TYPE_TABLE )
-        return LoopOverTable(f, val);
+        z = LoopOverTable(f, val);
 
     else if ( et == TYPE_VECTOR )
-        return LoopOverVector(f, val);
+        z = LoopOverVector(f, val);
 
     else if ( et == TYPE_STRING )
-        return LoopOverString(f, e);
+        z = LoopOverString(f, e);
 
     else
         reporter->InternalError("bad \"for\" loop-over value when compiling");
+
+    AddCFT(insts1[head.stmt_num], CFT_LOOP);
+    AddCFT(insts1[z.stmt_num], CFT_BLOCK_END);
+
+    return z;
 }
 
 const ZAMStmt ZAMCompiler::LoopOverTable(const ForStmt* f, const NameExpr* val) {
@@ -798,6 +821,7 @@ const ZAMStmt ZAMCompiler::LoopOverTable(const ForStmt* f, const NameExpr* val)
     }
 
     z.aux = aux; // so ZOpt.cc can get to it
+    AddCFT(&z, CFT_LOOP_COND);
 
     return FinishLoop(iter_head, z, body, iter_slot, true);
 }
@@ -842,6 +866,8 @@ const ZAMStmt ZAMCompiler::LoopOverVector(const ForStmt* f, const NameExpr* val)
         }
     }
 
+    AddCFT(&z, CFT_LOOP_COND);
+
     return FinishLoop(iter_head, z, f->LoopBody(), iter_slot, false);
 }
 
@@ -878,6 +904,8 @@ const ZAMStmt ZAMCompiler::LoopOverString(const ForStmt* f, const Expr* e) {
         z.is_managed = true;
     }
 
+    AddCFT(&z, CFT_LOOP_COND);
+
     return FinishLoop(iter_head, z, f->LoopBody(), iter_slot, false);
 }
 
@@ -886,7 +914,11 @@ const ZAMStmt ZAMCompiler::Loop(const Stmt* body) {
     PushBreaks();
 
     auto head = StartingBlock();
-    (void)CompileStmt(body);
+    auto b = CompileStmt(body);
+
+    AddCFT(insts1[head.stmt_num], CFT_LOOP);
+    AddCFT(insts1[b.stmt_num], CFT_BLOCK_END);
+
     auto tail = GoTo(GoToTarget(head));
 
     ResolveNexts(GoToTarget(head));
diff --git a/src/script_opt/ZAM/ZInst.h b/src/script_opt/ZAM/ZInst.h
index 3772fa97b5..fc013181e9 100644
--- a/src/script_opt/ZAM/ZInst.h
+++ b/src/script_opt/ZAM/ZInst.h
@@ -375,6 +375,18 @@ private:
     bool is_managed = false;
 };
 
+enum ControlFlowType {
+    CFT_IF,
+    CFT_IF_NOT,
+    CFT_IF_ELSE,
+    CFT_BLOCK_END,
+    CFT_ELSE,
+    CFT_LOOP,
+    CFT_LOOP_COND,
+    CFT_NEXT,
+    CFT_BREAK,
+};
+
 // Auxiliary information, used when the fixed ZInst layout lacks
 // sufficient expressiveness to represent all of the elements that
 // an instruction needs.
@@ -493,6 +505,9 @@ public:
     // Whether we know that we're calling a BiF.
     bool is_BiF_call = false;
 
+    // Associated control flow information.
+    std::set<ControlFlowType> cft;
+
     // Used for referring to events.
     EventHandler* event_handler = nullptr;