Re: [PATCH] rs6000, fix vec_replace_unaligned builtin arguments

[Carl Love <cel@us.ibm.com>]

Kewen:

On Mon, 2023-06-19 at 11:50 +0800, Kewen.Lin wrote:
> > generated the vinsd instruction for the two calls with the first
> > argument of unsigned long long int.  When the first argument of the
> > builtin is changed to the correct type, vector unsigned char the
> > builtin generates the vinsw instruction instead.  The change occurs
> > in
> > two places resulting in reducing the counts for vinsd by two and
> > increasing the counts for vinsw by two.  The other calls to the
> > builtin
> > are either vector ints or vector floats which generate the vinsw
> > instruction.  Changing the first argument in those calls to vector
> > unsigned char still generate the vinsw instruction.
> 
> But it did expose something odd and needed to be handled in this
> change.
> I had a further check, for the below test case:
> 
> #include "altivec.h"
> 
> #ifdef ORIG
> vector unsigned char foo (vector unsigned long long v){
>   unsigned long long val = 678ull;
>   return vec_replace_unaligned (v, val, 7);
> }
> #else
> vector unsigned char foo (vector unsigned long long v){
>   unsigned long long val = 678ull;
>   return vec_replace_unaligned ((vector unsigned char)v, val, 7);
> }
> #endif
> 
> Without this patch (-DORIG required to match the previous prototype),
> it would generate vinsd; while with this proposed patch, it would
> generate vinsw.  I think it's unexpected since users can still have
> the need to replace a doubleword size of chunk but give a constant
> which can be represented by int.  The previous way can support it,
> while the new way can't.  So we should have some way to distinguish
> it, we have some special-casing in function
> altivec_resolve_overloaded_builtin, could you have a check and try
> there?  Thanks!

I added the needed handling in altivec_resolve_overloaded_builtin to
address the issue with the built-in generating the correct instruction
for the unsigned long long cases in the test file.  I added an
additional test file with the above test case.  It was put into a new
test file as it requires the -flax-vector-conversions argument.  I felt
that it was best to separate the tests that need/do not need the -flax-
vector-conversions argument.

Note, adding the additional case statement RS6000_OVLD_VEC_REPLACE_UN
to handle the three argument built-in vec_replace_unaligned in
altivec_resolve_overloaded_builtin exposed an issue with function
find_instance.  Function find_instance assumes there are only two
arguments in the builtin.  There are no checks on the actual number of
arguments used by the built-in. This leads to an error in
tree_operand_check_failed() when using find_builtin.  The find_buitin
function was extended to handle 2 or 3 arguments with a check to make
sure the number of arguments is either 2 or 3.

FYI, I also noticed in the current patch the names in rs6000-
builtins.def and rs6000-overload.def for builtin_altivec_vreplace_un
still reflect the type of the first argument.  The current patch
changes the first argument to vuc, but the naming didn't all get
updated.  I think the names should be changed to reflect the name of
the second argument since the first arguments are all identical.  For
example:
 
    -- a/gcc/config/rs6000/rs6000-builtins.def
    +++ b/gcc/config/rs6000/rs6000-builtins.def
    @@ -3388,29 +3388,29 @@
       const vull __builtin_altivec_vpextd (vull, vull);
         VPEXTD vpextd {}
     
   -  const vuc __builtin_altivec_vreplace_un_uv2di (vull, unsigned long long, \
   -                                                 const int<4>);
   -    VREPLACE_UN_UV2DI vreplace_un_v2di {}
   +  const vuc __builtin_altivec_vreplace_un_udi (vuc, unsigned long long, \
   +                                               const int<4>);
   +    VREPLACE_UN_UDI vreplace_un_di {}
 
 The name changes will ripple thru files rs6000-builtins.def, rs6000-
 overload.def and vsx.md.

I did all the naming as well in the new version 3 of the patch.

                         Carl