On 09/09/2016 02:59 PM, Segher Boessenkool wrote:
On Thu, Sep 08, 2016 at 11:51:53AM -0600, Jeff Law wrote:
On 07/31/2016 07:42 PM, Segher Boessenkool wrote:
A restore is supposed to restore some certain register. Restoring it
into some other register will not work. Don't.
2016-06-07 Segher Boessenkool <seg...@kernel.crashing.org>
* regrename.c (build_def_use): Invalidate chains that have a
REG_CFA_RESTORE on some instruction.
Again, how is this different from a normal epilogue that restores
registers which regrename seems to not muck with.
Good question. Either way, it is always wrong to rename a register we
restore from stack.
Agreed. Somehow register renaming does the right thing for a normal
epilogue. I don't see anything in regrename that obviously treats the
epilogue specially, there's check_new_reg_p, but I don't see that it
inherently handles this case.
regrename seems to use the DF infrastructure, so I wouldn't be surprised
if this is a symptom of incorrect DF information for the epilogues. One
way to potentially find out would be to tweak the DF code to mark all
the callee saved regs as live at the return insns and see how that
affects regrename's decision making.
jeff
