http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60418
--- Comment #18 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Shouldn't we just prefer the original IL if possible? That is not SSA_NAME_VERSION, but not gimple_uid of the stmt definition either. If you have: _4 = something; _5 = somethingelse; _6 = somethingdifferent; _7 = _6 + _4; _8 = _7 + _5; then both SSA_NAME_VERSION and gimple_uid of def_stmt sorting would result in _9 = _4 + _5; _8 = _9 + _6; wouldn't it? But what do we gain by reassociating this (perhaps it can help value numbering and CSE if you have differently ordered sequences, but other than that this seems to be unnecessary reshufling and especially for floating point values and -ffast-math unnecessary source of extra ulps). So perhaps we want to sort by gimple uid of the first use among the insns we are looking at (and take into account also the operand number)?
