[Bug optimization/13136] New: invalid "might be used uninitialized" warning (-O, long long)

[Bug optimization/13136] New: invalid "might be used uninitialized" warning (-O, long long)

[gcc-bugzilla at gcc dot gnu dot org]

	GCC gives 'might be used uninitialized in this function' warning when
	'long long' variable 'd' is first set to some value and then modified
	in next line. Compiled with '-O -Wall'. 'long' type variable works ok.

Environment:
System: Linux haapana 2.4.22 #12 SMP Fri Nov 7 04:07:28 EET 2003 i686 unknown unknown GNU/Linux
Architecture: i686

host: i686-pc-linux-gnu
build: i686-pc-linux-gnu
target: mcore-unknown-elf
configured with: /work/gcc/configure --target=mcore-elf --with-gnu-as --with-gcc --disable-nls --enable-languages=c,objc,c++ --with-gnu-ld --prefix=/emb/cross-gcc-current --program-prefix=mcore-elf- --program-suffix= -v --with-newlib --with-headers=/pub/devel/gnu/newlib-1.11.0/newlib/libc/include

How-To-Repeat:
	/* ***** start of test.c ***** */
	/* compile: mcore-elf-gcc -O -Wall -o test.o -c test.c */
	
	int test(int c)
	{
	  long long d;
	  
	  d = 32000000LL << 1;
	      
	  return (int)d;
	}
	/* ****** end of test.c ****** */
------- Additional Comments From sami dot kantoluoto at embedtronics dot fi  2003-11-20 07:57 -------
Fix:
	Workaround: initialize 'd' variable to e.g. zero (0). Like:

	int test(int c)
	{
	  long long d = 0;
	  
	  d = 32000000LL << 1;
	      
	  return (int)d;
	}

-- 
           Summary: invalid "might be used uninitialized" warning (-O, long
                    long)
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sami dot kantoluoto at embedtronics dot fi
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: mcore-unknown-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13136

[Bug optimization/13136] invalid "might be used uninitialized" warning (-O, long long)

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-11-20 08:01 -------
Related to bug 12792 (filed for m68k).
Actually I think its analysis is to be able to mark it as a dup of it then:
* life_analysis() does not track subregister modifications -- if you don't
modify the whole register with a single set, it considers the register
unused.

*** This bug has been marked as a duplicate of 12792 ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13136