[Bug optimization/13643] New: __builtin_constant_p() fails to notice known value of member variable

[Bug optimization/13643] New: __builtin_constant_p() fails to notice known value of member variable

[bryner at brianryner dot com]

The testcase can probably demonstrate this better than I can verbalize it. 
Basically, I have an object allocated on the stack that initializes a member
variable to a constant.  I then call an inlined function on the object which
wants to use __builtin_constant_p() on the member variable.  The constant check
evaluates to false... it seems like the compiler should have sufficient
information to determine the value of the member variable.  In particular, note
that for struct B in the test case, the |if| in the inline function is optimized
away at compile time.  Therefore it seems like __builtin_constant_p() should
evaluate to true in struct A.

(It should be fairly obvious what I'm trying to do here -- eliminate an
unnecessary call to delete(NULL) when mPtr is known to be null at compile time).

-- 
           Summary: __builtin_constant_p() fails to notice known value of
                    member variable
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bryner at brianryner dot com
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13643

[Bug optimization/13643] __builtin_constant_p() fails to notice known value of member variable

[bryner at brianryner dot com]

------- Additional Comments From bryner at brianryner dot com  2004-01-11 09:51 -------
Created an attachment (id=5450)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=5450&action=view)
testcase

Compiled with:
c++ -Os -c -o test_const.o test_const.cpp

$ c++ -v
Reading specs from /usr/gcc34/lib/gcc/i686-pc-linux-gnu/3.4.0/specs
Configured with: ../gcc/configure --prefix=/usr/gcc34 --enable-shared
--enable-threads=posix --disable-checking --with-system-zlib
--enable-__cxa_atexit --enable-languages=c,c++ --host=i686-pc-linux-gnu
Thread model: posix
gcc version 3.4.0 20040110 (experimental)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13643

[Bug optimization/13643] __builtin_constant_p() fails to notice known value of member variable

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-01-11 16:07 -------
Fixed on the tree-ssa already so suspending it.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |SUSPENDED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13643

[Bug optimization/13643] __builtin_constant_p() fails to notice known value of member variable

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-01-11 16:07 -------
Confirmed on the mainline but ...

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |pessimizes-code
   Last reconfirmed|0000-00-00 00:00:00         |2004-01-11 16:07:05
               date|                            |
   Target Milestone|---                         |tree-ssa
            Version|unknown                     |3.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13643

[Bug tree-optimization/13643] __builtin_constant_p() fails to notice known value of member variable

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-13 11:33 -------
Fixed for 3.5.0 by the merge of the tree-ssa.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|SUSPENDED                   |RESOLVED
          Component|rtl-optimization            |tree-optimization
         Resolution|                            |FIXED
   Target Milestone|tree-ssa                    |3.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13643