function fIr$Tmp return number is
nRes number;
begin        
  nRes :=  268435456;
  -- nRes := power(2, 28); -- а так все нормально.
  return nRes;
end;

select svc$23532pkg.fIr$Tmp from dual
--------------------------------------
429514

select * from v$version
-------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
PL/SQL Release 11.2.0.4.0 - Production
CORE    11.2.0.4.0    Production
TNS for Solaris: Version 11.2.0.4.0 - Production
NLSRTL Version 11.2.0.4.0 - Production

 return fIr$Tmp.nRes;

alter session set plsql_optimize_level = 0;
alter package svc$23532pkg compile;

select svc$23532pkg.fIr$Tmp from dual
--------------------------------------
429514

select text from dba_source
where owner = 'XXXXXX'
and name = 'SVC$23532PKG'
and line >= 97818
order by line
------------
function fIr$Tmp return number is
nRes number;
 begin        
    nRes :=  268435457;--power(2, 28);
    return nRes;
end;
END SVC$23532PKG;

function fIr$Tmp return number is
nRes number;
 begin        
    nRes :=  268435457;--power(2, 28);
    return nRes;
 end;

function fIr$Tmp2 return number is
cRes CONSTANT number := 268435457;
nRes number;
 begin        
    nRes :=  cRes;
    return nRes;
 end; 

 function fIr$Tmp3 return number is
cRes CONSTANT number := 268435457;
nRes number;
 begin        
    return cRes;
 end;
 
select BP$5024_PO_tmp.fIR$Tmp as ver_0, BP$5024_PO_tmp.fIR$Tmp2 as ver_2, BP$5024_PO_tmp.fIR$Tmp3 as ver_3 from dual
VER_0     VER_2     VER_3
-----------------------------
420057    429514    383429

function fIr$Tmp return number is
nRes number;
 begin        
    nRes :=  268435457+0;--power(2, 28);
    return nRes;
 end;

 function fIr$Tmp3 return number is
cRes CONSTANT number := 268435457;
nRes number;
 begin        
    return cRes;
 end;

select SVC$23532PKG.fIR$Tmp as ver_0, SVC$23532PKG.fIR$Tmp3 as ver_3 from dual
----------------
VER_0    VER_3
429514    268435457

alter session set plsql_code_type = native;

alter session set plsql_code_type = native;
alter package SVC$23532PKG compile;

select SVC$23532PKG.fIR$Tmp as ver_0 from dual
---------------------------
VER_0
429514

select * from USER_OBJECT_SIZE where name = 'SVC$23532PKG'
-------------------------------------------------------------------------
SVC$23532PKG    PACKAGE                55787       160551       91580    0
SVC$23532PKG    PACKAGE BODY    5516957           6848    6959681    0

alter session set plsql_debug = true;
alter package SVC$23532PKG compile debug;

select SVC$23532PKG.fIR$Tmp as ver_0 from dual
VER_0 
------
429514

select * from USER_OBJECT_SIZE where name = 'SVC$23532PKG'

NAME           TYPE    SOURCE_SIZE    PARSED_SIZE    CODE_SIZE    ERROR_SIZE
------------------------------------------------------------------------
SVC$23532PKG    PACKAGE    55787    160551    91580    0
SVC$23532PKG    PACKAGE BODY    5516957    6848    6959449    0

function fXXX return number is
 c1 CONSTANT number := 268435457;
 c2 CONSTANT number := 268435457;
 ...
 cn CONSTANT number := 268435457;
begin 
 return cn;
end;

function fIr$Tmp return number is
nRes number;
begin        
  nRes :=  268;
  return nRes;
end;

......
function fIr$Tmp_110 return number is 
nRes number;
begin        
  nRes :=  268435456;
  return nRes;
end;
function fIr$Tmp_111 return number is 
nRes number;
begin        
  nRes :=  268;
  return nRes;
end;
function fIr$Tmp_112 return number is 
nRes number;
begin        
  nRes :=  268435457;
  return nRes;
end;
......

select count(*) from all_source
 where owner = 'XXXXXXX' 
   and type = 'PACKAGE BODY' 
   and name = 'SVC$23532PKG'
   and text like '%(429514,%'
   --
   130 --  429514 - некорректное значение, возвращаемое fIr$Tmp

select count(*) from all_source
 where owner = 'XXXXXXX' 
   and type = 'PACKAGE BODY' 
   and name = 'SVC$23532PKG'
   and text like '%26843545%'
   --
   3 -- это одна штатная fIr$Tmp + две, которые ввел по ходу обсуждения: fIr$Tmp2 + fIr$Tmp3

function fIr$Tmp return number is
nRes number;
 begin        
    nRes :=  268435455;
    return nRes;
 end;
 
select SVC$23532PKG.fIR$Tmp as ver_0 from dual
-------
 VER_0
 429514

drop package SVC$23532PKG;   
create or replace package SVC$23532PKG as...
create or replace package body SVC$23532PKG as...
    
select SVC$23532PKG.fIR$Tmp as ver_0 from dual
-------
 VER_0
 429514

drop package SVC$23532PKG;   
--create or replace package SVC$23532PKG as...
--create or replace package body SVC$23532PKG as...
    
select SVC$23532PKG.fIR$Tmp as ver_0 from dual
???

drop package SVC$23532PKG;

select SVC$23532PKG.fIr$Tmp from dual

ORA-00904: "SVC$23532PKG"."FIR$TMP": invalid identifier

alter session set plsql_warnings = 'enable:all';

alter session set plsql_warnings = 'enable:all';
alter package SVC$23532PKG compile;

select  text, count(1) from dba_errors where name = 'SVC$23532PKG'  group by text
-----
PLW-06010: keyword "RESULT" used as a defined name	149
PLW-07203: parameter 'OP' may benefit from use of the NOCOPY compiler hint	1452
PLW-06002: Unreachable code	473
PLW-05018: unit SVC$23532PKG omitted optional AUTHID clause; default value DEFINER used	1

select line, name, text from all_source where owner = 'COLVIR' and name = 'SVC$23532PKG' and type = 'PACKAGE BODY' and line > 97825 order by line
LINE      NAME               TEXT
------------------------------------------------------------
97826 SVC$23532PKG  "function fIr$Tmp2 return number is
97827 SVC$23532PKG  "nRes number;
97828 SVC$23532PKG  " begin        
97829 SVC$23532PKG  "    nRes := 268435457;
97830 SVC$23532PKG  "    return nRes;
97831 SVC$23532PKG  " end; 
97832 SVC$23532PKG  "function fIr$Tmp return number is
97833 SVC$23532PKG  "nRes number;
97834 SVC$23532PKG  " begin       
97835 SVC$23532PKG  "    nRes :=  26843;
97836 SVC$23532PKG  "    return nRes;
97837 SVC$23532PKG  " end;
97838 SVC$23532PKG  "END SVC$23532PKG;

select SVC$23532PKG.fIr$Tmp fIr$Tmp,SVC$23532PKG.fIr$Tmp2 fIr$Tmp2 from dual
----------------------------------------------------------------
fIr$Tmp   fIr$Tmp2
26843     429514