Re: PING [Patch][Middle-end]Add -fzero-call-used-regs=[skip|used-gpr|all-gpr|used|all]

[Qing Zhao via Gcc-patches]

> On Sep 15, 2020, at 2:41 PM, Segher Boessenkool <seg...@kernel.crashing.org> 
> wrote:
> 
> On Tue, Sep 15, 2020 at 10:11:41AM +0100, Richard Sandiford wrote:
>> Qing Zhao <qing.z...@oracle.com> writes:
>>>> On Sep 14, 2020, at 2:20 PM, Richard Sandiford <richard.sandif...@arm.com> 
>>>> wrote:
> (Putting correct info in DF, inserting the new insns in pro_and_epi).
> 
> But, scheduling runs *after* that, and then you need to prevent the
> inserted (zeroing) insns from moving -- if you don't, the code after
> some zeroing can be used as gadget!  You want to always have all
> zeroing insns after *any* computational insn, or it becomes a gadget.

Please see the previous discussion, we have agreed to put the new pass   
(pass_zero_call_used_regs) 
in the beginning of the pass_late_compilation as following:

     PUSH_INSERT_PASSES_WITHIN (pass_late_compilation)
++++  NEXT_PASS (pass_zero_call_used_regs);
         NEXT_PASS (pass_compute_alignments);
         NEXT_PASS (pass_variable_tracking);
         NEXT_PASS (pass_free_cfg);
         NEXT_PASS (pass_machine_reorg);
         NEXT_PASS (pass_cleanup_barriers);
         NEXT_PASS (pass_delay_slots);

Scheduling has been done already. 

Qing


> 
> 
> Segher