Re: [PATCH] PR target/66819: Allow indirect sibcall with register arguments

[Uros Bizjak <ubizjak at gmail dot com>]

On Fri, Jul 10, 2015 at 7:58 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Fri, Jul 10, 2015 at 10:21 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
>> On Fri, Jul 10, 2015 at 7:10 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> On Fri, Jul 10, 2015 at 9:30 AM, Uros Bizjak <ubizjak@gmail.com> wrote:
>>>> On Thu, Jul 9, 2015 at 12:54 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>>>> Indirect sibcall with register arguments is OK when there is register
>>>>> available for argument passing.
>>>>>
>>>>> OK for trunk if there is no regression?
>>>>>
>>>>>
>>>>> H.J.
>>>>> ---
>>>>> gcc/
>>>>>
>>>>>         PR target/66819
>>>>>         * config/i386/i386.c (ix86_function_ok_for_sibcall): Allow
>>>>>         indirect sibcall with register arguments if register available
>>>>>         for argument passing.
>>>>>         (init_cumulative_args): Set cfun->machine->arg_reg_available_p
>>>>>         to cum->nregs != 0.
>>
>> Please update the above entry for nregs > 0.
>>
>>>>>         (function_arg_advance_32): Set cfun->machine->arg_reg_available_p
>>>>>         to 0 when setting cum->nregs = 0.
>>>>
>>>> Do we also need similar functionality for 64bit ABIs? What happens if
>>>> we are out of argument regs there?
>>>
>>> 64-bit is OK since we have rax, r10 and r11 as scratch registers which
>>> aren't used to pass arguments.
>>
>> Maybe this fact should be added as a comment in some appropriate place.
>>
>>>>>         * config/i386/i386.h (machine_function): Add arg_reg_available_p.
>>>>>
>>>>> gcc/testsuite/
>>>>>
>>>>>         PR target/66819
>>>>>         * gcc.target/i386/pr66819-1.c: New test.
>>>>>         * gcc.target/i386/pr66819-2.c: Likewise.
>>>>>         * gcc.target/i386/pr66819-3.c: Likewise.
>>>>>         * gcc.target/i386/pr66819-4.c: Likewise.
>>>>>         * gcc.target/i386/pr66819-5.c: Likewise.
>>>>> ---
>>>>>  gcc/config/i386/i386.c                    | 15 +++++++++------
>>>>>  gcc/config/i386/i386.h                    |  3 +++
>>>>>  gcc/testsuite/gcc.target/i386/pr66819-1.c |  8 ++++++++
>>>>>  gcc/testsuite/gcc.target/i386/pr66819-2.c |  8 ++++++++
>>>>>  gcc/testsuite/gcc.target/i386/pr66819-3.c | 10 ++++++++++
>>>>>  gcc/testsuite/gcc.target/i386/pr66819-4.c | 12 ++++++++++++
>>>>>  gcc/testsuite/gcc.target/i386/pr66819-5.c | 10 ++++++++++
>>>>>  7 files changed, 60 insertions(+), 6 deletions(-)
>>>>>  create mode 100644 gcc/testsuite/gcc.target/i386/pr66819-1.c
>>>>>  create mode 100644 gcc/testsuite/gcc.target/i386/pr66819-2.c
>>>>>  create mode 100644 gcc/testsuite/gcc.target/i386/pr66819-3.c
>>>>>  create mode 100644 gcc/testsuite/gcc.target/i386/pr66819-4.c
>>>>>  create mode 100644 gcc/testsuite/gcc.target/i386/pr66819-5.c
>>>>>
>>>>> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
>>>>> index 54ee6f3..85e59a8 100644
>>>>> --- a/gcc/config/i386/i386.c
>>>>> +++ b/gcc/config/i386/i386.c
>>>>> @@ -5628,12 +5628,12 @@ ix86_function_ok_for_sibcall (tree decl, tree exp)
>>>>>        if (!decl
>>>>>           || (TARGET_DLLIMPORT_DECL_ATTRIBUTES && DECL_DLLIMPORT_P (decl)))
>>>>>         {
>>>>> -         if (ix86_function_regparm (type, NULL) >= 3)
>>>>> -           {
>>>>> -             /* ??? Need to count the actual number of registers to be used,
>>>>> -                not the possible number of registers.  Fix later.  */
>>>>> -             return false;
>>>>> -           }
>>>>> +         /* FIXME: The symbol indirect call doesn't need a
>>>>> +            call-clobbered register.  But we don't know if
>>>>> +            this is a symbol indirect call or not  here.  */
>>>>> +         if (ix86_function_regparm (type, NULL) >= 3
>>>>> +             && !cfun->machine->arg_reg_available_p)
>>>>
>>>> Isn't enough to look at arg_reg_available here?
>>>
>>> We need to check ix86_function_regparm since nregs is 0 if
>>> -mregparm=N isn't used and pr65753.c will fail.
>>
>> OK. Please add this comment, is not that obvious.
>>
>>>
>>>>> +           return false;
>>>>>         }
>>>>>      }
>>>>>
>>>>> @@ -6567,6 +6567,7 @@ init_cumulative_args (CUMULATIVE_ARGS *cum,  /* Argument info to initialize */
>>>>>                     ? X86_64_REGPARM_MAX
>>>>>                     : X86_64_MS_REGPARM_MAX);
>>>>>      }
>>>>> +  cfun->machine->arg_reg_available_p = cum->nregs != 0;
>>>>
>>>> false instead of 0. This is a boolean.
>>>
>>> Updated.
>>>
>>>>>    if (TARGET_SSE)
>>>>>      {
>>>>>        cum->sse_nregs = SSE_REGPARM_MAX;
>>>>> @@ -6636,6 +6637,7 @@ init_cumulative_args (CUMULATIVE_ARGS *cum,  /* Argument info to initialize */
>>>>>           else
>>>>>             cum->nregs = ix86_function_regparm (fntype, fndecl);
>>>>>         }
>>>>> +      cfun->machine->arg_reg_available_p = cum->nregs != 0;
>>>>
>>>> IMO, cum->nregs > 0 would be more descriptive.
>>>
>>> Updated.
>>>
>>>>>        /* Set up the number of SSE registers used for passing SFmode
>>>>>          and DFmode arguments.  Warn for mismatching ABI.  */
>>>>> @@ -7584,6 +7586,7 @@ pass_in_reg:
>>>>>         {
>>>>>           cum->nregs = 0;
>>>>>           cum->regno = 0;
>>>>> +         cfun->machine->arg_reg_available_p = 0;
>>>>>         }
>>>>>        break;
>>>>>
>>>>> diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
>>>>> index 74334ff..0b6e304 100644
>>>>> --- a/gcc/config/i386/i386.h
>>>>> +++ b/gcc/config/i386/i386.h
>>>>> @@ -2479,6 +2479,9 @@ struct GTY(()) machine_function {
>>>>>    /* If true, it is safe to not save/restore DRAP register.  */
>>>>>    BOOL_BITFIELD no_drap_save_restore : 1;
>>>>>
>>>>> +  /* If true, there is register available for argument passing.  */
>>>>> +  BOOL_BITFIELD arg_reg_available_p : 1;
>>>>
>>>> This is not a predicate, but a boolean flag. Please remove _p from the name.
>>>
>>> Updated.
>>>
>>> Here is the updated patch.  OK for trunk?
>>
>> OK with a small comment additions.
>>
>> +  /* If true, there is register available for argument passing.  */
>> +  BOOL_BITFIELD arg_reg_available : 1;
>> +
>>
>> Please mention here that this is for 32bit targets only.
>>
>
> Updated. Is this one OK?

LGTM.

OK for mainline.

Thanks,
Uros.