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

["H.J. Lu" <hjl.tools@gmail.com>]

On Thu, Jul 9, 2015 at 4:04 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.
>>         * 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)
>> +           return false;
>>         }
>>      }
>
> Why can't we directly look at nregs != 0 in the above code? AFAICS,
> nregs accurately tracks number of available argument registers.
>

I tried it first.  But nregs isn't accessible from ix86_function_ok_for_sibcall.

-- 
H.J.