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.
>>         (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.

>>         * 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.

>> +           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?

Thanks.

-- 
H.J.