select RDB$TRIGGER_NAME, RDB$TRIGGER_TYPE
  from RDB$TRIGGERS
 where RDB$RELATION_NAME = 'MY_TABLE'

before insert  1
after  insert  2
before update  3
after  update  4
before delete  5
after  delete  6

before
IU	 17	0001 0001
IUD	113	0111 0001
I D	 25	0001 1001
 UD	 27	0001 1011

after
IU	 18	0001 0010
IUD	114	0111 0010
I D	 26	0001 1010
 UD	 28	0001 1100

inline int TRIGGER_ACTION_SUFFIX(int value, int slot)
{
         return ((value + 1) >> (slot * 2 - 1)) & 3;
}

{
declare external function TRIGGER_IS
    integer,
    integer
    returns integer by value
entry_point 'TriggerIs' module_name 'MyUDF.dll';
}
function TriggerIs( var aType, aKind : integer ) : integer; cdecl; export; assembler;
{
  aType - значение поля RDB$TRIGGERS.RDB$TRIGGER_TYPE
  aKind - тип DML (1 - insert, 2 - update, 3 - delete)
}
asm
     Push    EBX

     Mov     ECX,   [EAX]
     Inc     ECX
     Mov     EDX,   [EDX]

     Xor     EAX,   EAX
     Shr     ECX,   1

@@10:
     Jcxz    @@90
     Mov     EBX,   ECX
     Shr     ECX,   2
     And     EBX,   0003h
     Cmp     EBX,   EDX
     Jne     @@10

     Inc     EAX

@@90:
     Pop     EBX
end;

set term ^ ;

create procedure TRIIGER_IS (
    TRIGGER_TYPE integer,
    KIND  smallint )
returns (
    IS_TRUE smallint )
as
begin
  IS_TRUE = 0;
  TRIGGER_TYPE = :TRIGGER_TYPE + 1;
  bin_shr( :TRIGGER_TYPE, 1 );

  while ( :TRIGGER_TYPE > 0 ) do
  begin
    if ( bin_and( :TRIGGER_TYPE, 3 ) = :KIND ) then
    begin
      IS_TRUE = 1;
      break;
    end
    bin_shr( :TRIGGER_TYPE, 2 );
  end

  suspend;
end ^

set term ; ^

set term ^ ;

create procedure TRIGGER_IS (
    TRIGGER_TYPE integer,
    KIND  smallint )
returns (
    IS_TRUE smallint )
as
begin
  IS_TRUE = 0;
  TRIGGER_TYPE = :TRIGGER_TYPE + 1;
  bin_shr( :TRIGGER_TYPE, 1 );

  while ( :TRIGGER_TYPE > 0 ) do
  begin
    if ( bin_and( :TRIGGER_TYPE, 3 ) = :KIND ) then
    begin
      IS_TRUE = 1;
      break;
    end
    TRIGGER_TYPE = bin_shr( :TRIGGER_TYPE, 2 );
  end

  suspend;
end ^

set term ; ^

execute block
as
  declare variable CNT integer;
  declare variable TMP integer;
begin
  CNT = 1000000;
  while ( :CNT > 0 ) do
  begin
--    TMP = TRIGGER_IS( 27, 1 );
    TMP = ( select IS_TRUE from TRIGGER_IS( 27, 1 ) );
    CNT = :CNT - 1;
  end
end