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Subject: [Bug regression/49498] [4.7 Regression]: gcc.dg/uninit-pred-8_b.c bogus warning line 20
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49498

--- Comment #4 from davidxl <xinliangli at gmail dot com> 2011-06-30 20:37:36 UTC ---
I can to reproduce the problem on x86-64 linux. Can you help provide the
following dump:

 -fdump-tree-uninit-blocks-details?

Thanks,

David



(In reply to comment #3)
> Frankly, I'm just not able to wrap my head around the tree-ssa-uninit
> implementation.  I understand the general concepts, but just can't seem to find
> where in that code we handle certain things.  Perhaps it simply doesn't handle
> them.
> 
> In this simpler sample code we have:
> 
> /* { dg-do compile } */
> /* { dg-options "-Wuninitialized -O2" } */
> 
> int g;
> void bar();
> void blah(int);
> 
> int foo (int n, int l, int m, int r)
> {
>   int v;
> 
>   if (n < 10 || m > 100)
>     v = r;
> 
>   if (m) g++;
> 
>   if ( n < 10 ||  m > 100)
>       blah(v); /* { dg-bogus "uninitialized" "bogus warning" } */
> 
>   return 0;
> }
> 
> Compiling with -O2 -Wuninitialized on cris-elf.
> 
> Someone who knows the code in tree-ssa-uninit.c really needs to chime in...
> Reading that code just makes my head hurt.
> 
> From the standpoint of the resulting CFG, the path 2->8->4->5->6 can never be
> traversed, nor can 2->3->9->4->6.  2->3->9->4->5 is properly guarded as far as
> I can tell, though I'm not convinced tree-ssa-uninit.c is computing the guards
> correctly.