[Bug middle-end/60418] [4.9 Regression] 435.gromacs in SPEC CPU 2006 is miscompiled

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60418

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |x32
   Target Milestone|---                         |4.9.0

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, what's the target triplet of a x32-only target?(In reply to H.J. Lu from
comment #0)
> Since r208165, 435.gromacs in SPEC CPU 2006 is miscompiled on x32 with
> 
> -mx32 -O3 -funroll-loops -ffast-math -fwhole-program -flto=jobserver
> -fuse-linker-plugin
> 
> The failure is
> 
>   Running 435.gromacs ref peak lto default
> 
> *** Miscompare of gromacs.out; for details see
>    
> /export/project/git/gcc-regression/spec/2006/spec/benchspec/CPU2006/435.grom
> acs/run/run_peak_ref_lto.0000/gromacs.out.mis
> 
> cat
> /export/project/git/gcc-regression/spec/2006/spec/benchspec/CPU2006/435.
> gromacs/run/run_peak_ref_lto.0000/gromacs.out.mis
> 0002:  3.07684e+02
>        3.03594e+02
> 
> The result of 3.03594e+02 is outside of tolerance for 3.07684e+02.
> I added a static counter in tree_forwarder_block_p for the number of
> times returned true above and return false if it is between getenv("from")
> and getenv("to").  I noticed that as more basic blocks get removed,
> the deviation is getting bigger. One removed basic block has
> 
> ;; basic block 3, loop depth 0, count 0, freq 225, maybe hot 
> ;;  prev block 2, next block 4, flags: (NEW, REACHABLE)
> ;;  pred:       2
> ;; 
> ;;  succ:       4
> 
> and its successor has
> 
> ;; basic block 4, loop depth 1, count 0, freq 2500, maybe hot 
> ;;  prev block 3, next block 5, flags: (NEW)
> ;;  pred:       3
> ;;              6
> ;; starting at line 722 
> # gimple_phi <i_429, 0(3), [bondfree.c : 726:24] i_27(6)>
> 
> Is is safe to remove basic block 3?

Sure it is.  This is a loop pre-header.