Qing Zhao <qing.z...@oracle.com> writes:
>>> + /* For each of the hard registers, check to see whether we should zero
>>> it if:
>>> + 1. it is a call-used-registers;
>>> + and 2. it is not a fixed-registers;
>>> + and 3. it is not live at the return of the routine;
>>> + and 4. it is general registor if gpr_only is true;
>>> + and 5. it is used in the routine if used_only is true;
>>> + and 6. it is a register that passes parameter if arg_only is true;
>>> + */
>>> +
>>> + HARD_REG_SET need_zeroed_hardregs;
>>> + CLEAR_HARD_REG_SET (need_zeroed_hardregs);
>>> + for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
>>> + {
>>> + if (!this_target_hard_regs->x_call_used_regs[regno])
>>> + continue;
>>
>> This should use crtl->abi instead. The set of call-used registers
>> can vary from function to function.
>
> You mean to use:
>
> If (!crtl->abi->clobbers_full_reg_p(regno))
>
> ?
Yeah, that's right. (But with a space before “(regno)” :-))
>>> +static unsigned int
>>> +rest_of_zero_call_used_regs (void)
>>> +{
>>> + basic_block bb;
>>> + rtx_insn *insn;
>>> +
>>> + /* This pass needs data flow information. */
>>> + df_analyze ();
>>> +
>>> + /* Search all the "return"s in the routine, and insert instruction
>>> sequence to
>>> + zero the call used registers. */
>>> + FOR_EACH_BB_REVERSE_FN (bb, cfun)
>>> + if (bb == EXIT_BLOCK_PTR_FOR_FN (cfun)
>>> + || (single_succ_p (bb)
>>> + && single_succ (bb) == EXIT_BLOCK_PTR_FOR_FN (cfun)))
>>> + FOR_BB_INSNS_REVERSE (bb, insn)
>>> + if (JUMP_P (insn) && ANY_RETURN_P (JUMP_LABEL (insn)))
>>> + {
>>> + /* Now we can insert the instruction sequence to zero the call used
>>> + registers before this insn. */
>>> + gen_call_used_regs_seq (insn);
>>> + break;
>>> + }
>>
>> The exit block never has instructions, so it's only necessary to process
>> predecessors. A simpler way to do that is to iterate over the edges in:
>>
>> EXIT_BLOCK_PTR_FOR_FN (cfun)->preds
>>
>> You shouldn't need to use FOR_BB_INSNS_REVERSE: it should be enough
>> to check only BB_END (bb), since returns always end blocks.
>
> Something like the following?
>
> FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds)
> {
> insn = BB_END (e->src);
> If (JUMP_P (insn) && ANY_RETURN_P (JUMP_LABEL (insn)))
> {
> /* Now we can insert the instruction sequence to zero the call used
> registers before this insn. */
> gen_call_used_regs_seq (insn);
> break;
> }
> }
With this you don't want/need the break, since it would break out
of the edge traversal (instead of the FOR_BB_INSNS_REVERSE, as above).
Also, I think the code becomes simple enough that the comment isn't
really needed.
Thanks,
Richard
