diff --git a/control.hh b/control.hh
index e41f008..c03de1b 100644
--- a/control.hh
+++ b/control.hh
@@ -38,6 +38,8 @@ enum E_OpType
 
 M_LSHIFT_OP( T_StringBuilder , E_OpType );
 uint32_t ArgumentsFor( E_OpType op ) noexcept;
+int32_t DeltaMainStack( E_OpType op ) noexcept;
+int32_t DeltaFPUStack( E_OpType op ) noexcept;
 
 
 struct T_Op
diff --git a/opcomp.cc b/opcomp.cc
index 9362d3d..0bd1cd8 100644
--- a/opcomp.cc
+++ b/opcomp.cc
@@ -56,6 +56,8 @@ struct T_CompilerImpl_
 			E_OpType op ,
 			uint32_t arg0 , uint32_t arg1 ,
 			T_SRDLocation const& location ) noexcept;
+	void applyStackEffects(
+			T_Op const& op ) noexcept;
 };
 
 
@@ -318,22 +320,17 @@ bool T_CompilerImpl_::compileNode(
 			if ( !main ) {
 				addInstruction( OP_PUSH , node.location( ) );
 				addInstruction( OP_FP_SSTORE , 0 , node.location( ) );
-				sdMain ++;
-				sdFPU --;
 			}
 			return false;
 		} else if ( exit && !n.isIdentifier( ) ) {
 			addInstruction( OP_PUSH , node.location( ) );
 			addInstruction( OP_FP_SSTORE , 0 , node.location( ) );
-			sdMain ++;
-			sdFPU --;
 		}
 		break;
 	    }
 
 	    case A_Node::OP_SET:
 		if ( exit ) {
-			assert( sdFPU > 0 );
 			auto& id( ((T_SetInstrNode&)node).id( ) );
 			auto& func{ input->root.function( funcIndex ) };
 			if ( func.hasLocal( id ) ) {
@@ -345,13 +342,11 @@ bool T_CompilerImpl_::compileNode(
 						*locations.get( ((T_SetInstrNode&)node).id( ) ) ,
 						node.location( ) );
 			}
-			sdFPU --;
 		}
 		break;
 
 	    case A_Node::OP_COND:
 		if ( exit ) {
-			assert( sdMain > 0 );
 			addInstruction( OP_POP , 0 , node.location( ) );
 			sdMain --;
 		}
@@ -361,8 +356,6 @@ bool T_CompilerImpl_::compileNode(
 		if ( exit ) {
 			addInstruction( OP_PUSH , node.location( ) );
 			addInstruction( OP_FP_SSTORE_INT , 0 , node.location( ) );
-			sdFPU --;
-			sdMain ++;
 		}
 		break;
 
@@ -395,30 +388,22 @@ bool T_CompilerImpl_::compileNode(
 
 	    case A_Node::EXPR_ADD:
 		if ( exit ) {
-			assert( sdFPU > 2 );
 			addInstruction( OP_FP_ADD , node.location( ) );
-			sdFPU --;
 		}
 		break;
 	    case A_Node::EXPR_SUB:
 		if ( exit ) {
-			assert( sdFPU > 2 );
 			addInstruction( OP_FP_SUB , node.location( ) );
-			sdFPU --;
 		}
 		break;
 	    case A_Node::EXPR_MUL:
 		if ( exit ) {
-			assert( sdFPU > 2 );
 			addInstruction( OP_FP_MUL , node.location( ) );
-			sdFPU --;
 		}
 		break;
 	    case A_Node::EXPR_DIV:
 		if ( exit ) {
-			assert( sdFPU > 2 );
 			addInstruction( OP_FP_DIV , node.location( ) );
-			sdFPU --;
 		}
 		break;
 
@@ -429,7 +414,6 @@ bool T_CompilerImpl_::compileNode(
 			addInstruction( OP_FP_LOAD ,
 					constants.indexOf( value.u ) + 3 ,
 					node.location( ) );
-			sdFPU ++;
 		}
 		break;
 
@@ -456,7 +440,7 @@ void T_CompilerImpl_::processFunction(
 			addInstruction( OP_POP , lvars - 1 , location );
 			sdMain -= lvars;
 		}
-		sdMain -= 1 + args;
+		sdMain -= args;
 		addInstruction( OP_RET , args , location );
 		assert( sdMain == 0 );
 	} else {
@@ -492,13 +476,11 @@ bool T_CompilerImpl_::processIdentifier(
 		const auto p( sdMain - ( stackPos + 1 ) );
 		if ( dt == E_DataType::VARIABLE ) {
 			addInstruction( OP_FP_SLOAD , p , node.location( ) );
-			sdFPU ++;
 			return false;
 		}
 
 		addInstruction( OP_SLOAD , p , node.location( ) );
 		addInstruction( OP_PUSH , node.location( ) );
-		sdMain ++;
 		return true;
 	}
 
@@ -509,14 +491,12 @@ bool T_CompilerImpl_::processIdentifier(
 	if ( dt == E_DataType::VARIABLE || dt == E_DataType::BUILTIN ) {
 		addInstruction( OP_FP_LOAD , *locations.get( node.id( ) ) ,
 				node.location( ) );
-		sdFPU ++;
 		return false;
 	}
 
 	addInstruction( OP_LOAD , *locations.get( node.id( ) ) ,
 			node.location( ) );
 	addInstruction( OP_PUSH , node.location( ) );
-	sdMain ++;
 	return true;
 }
 
@@ -526,7 +506,7 @@ void T_CompilerImpl_::addInstruction(
 		T_SRDLocation const& location ) noexcept
 {
 	assert( ArgumentsFor( op ) == 0 );
-	output->ops.addNew( op , location );
+	applyStackEffects( output->ops.addNew( op , location ) );
 }
 
 void T_CompilerImpl_::addInstruction(
@@ -535,7 +515,7 @@ void T_CompilerImpl_::addInstruction(
 		T_SRDLocation const& location ) noexcept
 {
 	assert( ArgumentsFor( op ) == 1 );
-	output->ops.addNew( op , location , arg0 );
+	applyStackEffects( output->ops.addNew( op , location , arg0 ) );
 }
 
 void T_CompilerImpl_::addInstruction(
@@ -545,7 +525,31 @@ void T_CompilerImpl_::addInstruction(
 		T_SRDLocation const& location ) noexcept
 {
 	assert( ArgumentsFor( op ) == 2 );
-	output->ops.addNew( op , location , arg0 , arg1 );
+	applyStackEffects( output->ops.addNew( op , location , arg0 , arg1 ) );
+}
+
+void T_CompilerImpl_::applyStackEffects(
+		T_Op const& op ) noexcept
+{
+	const auto m( DeltaMainStack( op.op ) );
+	const auto f( DeltaFPUStack( op.op ) );
+
+#ifdef INVASIVE_TRACES
+	T_StringBuilder sb;
+	sb << "applying stack effects for (" << op << ") - sdMain " << sdMain
+		<< " (" << m << ") sdFPU " << sdFPU << " (" << f << ")" << '\n' << '\0';
+	printf( "%s" , sb.data( ) );
+#endif
+
+	if ( m ) {
+		assert( m > 0 || sdMain >= uint32_t( -m ) );
+		sdMain += m;
+	}
+
+	if ( f ) {
+		assert( f > 0 || sdFPU >= uint32_t( -m ) );
+		sdFPU += m;
+	}
 }
 
 }
diff --git a/ops.cc b/ops.cc
index 738bf5e..423a4f9 100644
--- a/ops.cc
+++ b/ops.cc
@@ -14,43 +14,98 @@ namespace {
 struct T_OpInfo
 {
 	char const* name;
-	int nArgs;
+	uint32_t nArgs;
+	int32_t sdMain{ 0 };
+	int32_t sdFPU{ 0 };
+	uint32_t fpuReq{ 0 };
 
-	T_OpInfo( char const* name ,
-			int nArgs = 0 )
-		: name( name ) , nArgs( nArgs )
-	{ }
+	template< typename ... Mods >
+	constexpr T_OpInfo( char const* name ,
+			uint32_t nArgs ,
+			Mods&&... mods );
+
+	constexpr T_OpInfo( char const* name );
 };
 
+
+template< typename ... Mods >
+constexpr void ApplyMods_( T_OpInfo& op , Mods&&... mods );
+
+template< >
+constexpr void ApplyMods_( T_OpInfo& )
+{ }
+
+template< typename M0 , typename ... Mods >
+constexpr void ApplyMods_(
+		T_OpInfo& op ,
+		M0&& mod ,
+		Mods&&... mods )
+{
+	mod.applyTo( op );
+	ApplyMods_( op , std::forward< Mods >( mods ) ... );
+}
+
+template< typename ... Mods >
+constexpr T_OpInfo::T_OpInfo(
+		char const* name ,
+		uint32_t nArgs ,
+		Mods&&... mods )
+	: name( name ) , nArgs( nArgs )
+{
+	ApplyMods_( *this , std::forward< Mods >( mods ) ... );
+}
+
+constexpr T_OpInfo::T_OpInfo( char const* name )
+	: T_OpInfo( name , 0 )
+{}
+
+
+struct OpStackMain
+{
+	int32_t value;
+	explicit constexpr OpStackMain( int32_t v ) : value( v ) { }
+	constexpr void applyTo( T_OpInfo& op )
+		{ op.sdMain = value; }
+};
+
+struct OpStackFPU
+{
+	int32_t value;
+	explicit constexpr OpStackFPU( int32_t v ) : value( v ) { }
+	constexpr void applyTo( T_OpInfo& op )
+		{ op.sdFPU = value; }
+};
+
+
 static T_KeyValueTable< E_OpType , T_OpInfo > OpInfoTable_{ ([]() {
 	T_KeyValueTable< E_OpType , T_OpInfo > infos;
 
 	infos.add( E_OpType::OP_END , T_OpInfo{ "end" } );
 	//
 	infos.add( E_OpType::OP_CALL , T_OpInfo{ "call" , 1 } );
-	infos.add( E_OpType::OP_RET , T_OpInfo{ "ret" , 1 } );
+	infos.add( E_OpType::OP_RET , T_OpInfo{ "ret" , 1 , OpStackMain{ -1 } } );
 	infos.add( E_OpType::OP_COND_JUMP , T_OpInfo{ "cond-jump" , 2 } );
 	//
 	infos.add( E_OpType::OP_RES_STACK , T_OpInfo{ "res-stack" , 1 } );
-	infos.add( E_OpType::OP_PUSH , T_OpInfo{ "push" } );
+	infos.add( E_OpType::OP_PUSH , T_OpInfo{ "push" , 0 , OpStackMain{ 1 } } );
 	infos.add( E_OpType::OP_POP , T_OpInfo{ "pop" , 1 } );
 	//
 	infos.add( E_OpType::OP_LOAD , T_OpInfo{ "load" , 1 } );
 	infos.add( E_OpType::OP_SLOAD , T_OpInfo{ "load-stack" , 1 } );
 	//
-	infos.add( E_OpType::OP_FP_LOAD , T_OpInfo{ "fp-load" , 1 } );
-	infos.add( E_OpType::OP_FP_SLOAD , T_OpInfo{ "fp-load-stack" , 1 } );
-	infos.add( E_OpType::OP_FP_STORE , T_OpInfo{ "fp-store" , 1 } );
-	infos.add( E_OpType::OP_FP_SSTORE , T_OpInfo{ "fp-store-stack" , 1 } );
-	infos.add( E_OpType::OP_FP_SSTORE_INT , T_OpInfo{ "fp-store-stack-int" , 1 } );
+	infos.add( E_OpType::OP_FP_LOAD , T_OpInfo{ "fp-load" , 1 , OpStackFPU{ 1 } } );
+	infos.add( E_OpType::OP_FP_SLOAD , T_OpInfo{ "fp-load-stack" , 1 , OpStackFPU{ 1 } } );
+	infos.add( E_OpType::OP_FP_STORE , T_OpInfo{ "fp-store" , 1 , OpStackFPU{ -1 } } );
+	infos.add( E_OpType::OP_FP_SSTORE , T_OpInfo{ "fp-store-stack" , 1 , OpStackFPU{ -1 } } );
+	infos.add( E_OpType::OP_FP_SSTORE_INT , T_OpInfo{ "fp-store-stack-int" , 1 , OpStackFPU{ -1 } } );
 	//
-	infos.add( E_OpType::OP_FP_CMP , T_OpInfo{ "fp-cmp" , 1 } );
-	infos.add( E_OpType::OP_FP_ADD , T_OpInfo{ "fp-add" } );
-	infos.add( E_OpType::OP_FP_SUB , T_OpInfo{ "fp-sub" } );
-	infos.add( E_OpType::OP_FP_MUL , T_OpInfo{ "fp-mul" } );
-	infos.add( E_OpType::OP_FP_DIV , T_OpInfo{ "fp-div" } );
-	infos.add( E_OpType::OP_FP_MUL , T_OpInfo{ "fp-neg" } );
-	infos.add( E_OpType::OP_FP_DIV , T_OpInfo{ "fp-inv" } );
+	infos.add( E_OpType::OP_FP_CMP , T_OpInfo{ "fp-cmp" , 1 , OpStackFPU{ -1 } } );
+	infos.add( E_OpType::OP_FP_ADD , T_OpInfo{ "fp-add" , 0 , OpStackFPU{ -1 } } );
+	infos.add( E_OpType::OP_FP_SUB , T_OpInfo{ "fp-sub" , 0 , OpStackFPU{ -1 } } );
+	infos.add( E_OpType::OP_FP_MUL , T_OpInfo{ "fp-mul" , 0 , OpStackFPU{ -1 } } );
+	infos.add( E_OpType::OP_FP_DIV , T_OpInfo{ "fp-div" , 0 , OpStackFPU{ -1 } } );
+	infos.add( E_OpType::OP_FP_MUL , T_OpInfo{ "fp-neg" , 0 } );
+	infos.add( E_OpType::OP_FP_DIV , T_OpInfo{ "fp-inv" , 0 } );
 
 	return infos;
 })( ) };
@@ -64,6 +119,20 @@ uint32_t ops::ArgumentsFor(
 	return OpInfoTable_.get( op )->nArgs;
 }
 
+int32_t ops::DeltaMainStack(
+		const E_OpType op ) noexcept
+{
+	assert( OpInfoTable_.contains( op ) );
+	return OpInfoTable_.get( op )->sdMain;
+}
+
+int32_t ops::DeltaFPUStack(
+		const E_OpType op ) noexcept
+{
+	assert( OpInfoTable_.contains( op ) );
+	return OpInfoTable_.get( op )->sdFPU;
+}
+
 
 /*= STRING FORMATTING ==========================================================*/