Re: [PATCH] Fix failing assertion in calls.c:store_unaligned_arguments_into_pseudos

[Jeff Law <law at redhat dot com>]

On 11/11/13 07:32, Ulrich Weigand wrote:
> Hello,
>
> when implementing the new ABI for powerpc64le-linux, I ran into an assertion
> failure in store_unaligned_arguments_into_pseudos:
>              gcc_assert (args[i].partial % UNITS_PER_WORD == 0);
>
> This can happen in the new ABI since we pass "homogeneous structures"
> consisting of soleley floating point elements of the same type in
> floating-point registers until they run out, and the rest of the
> structure in memory.  If the structure member type is a 4-byte float,
> and we only have an odd number of floating point registers available,
> then args[i].partial can legitimately end up not being a multiple
> of UNITS_PER_WORD (i.e. 8 on the platform).
>
> Now, there are a number of similar checks that args[i].partial is
> aligned elsewhere in calls.c and functions.c.  But for all of those
> the logic is: if args[i].reg is a REG, then args[i].partial must be
> a multiple of the word size; but if args[i].regs is a PARALLEL, then
> args[i].partial can be any arbitrary value.  In the powerpc64le-linux
> use case, the back-end always generates PARALLEL in this situation,
> so it seemed the middle-end ought to support this -- and it does,
> except for this one case.
>
> However, looking more closely, it seems store_unaligned_arguments_into_pseudos
> is not really useful for PARALLEL arguments in the first place.  What this
> routine does is load arguments into args[i].aligned_regs.  But if we have
> an argument where args[i].reg is a PARALLEL, args[i].aligned_regs will in
> fact never be used later on at all!   Instead, PARALLEL will always be
> handled directly via emit_group_move (in load_register_parameters), so
> the code generated by store_unaligned_arguments_into_pseudos for such cases
> is simply dead anyway.
>
> Thus, I'd suggest to simply have store_unaligned_arguments_into_pseudos
> skip PARALLEL arguments.
>
> Tested on powerpc64-linux and powerpc64le-linux.
>
> OK for mainline?
>
> Bye,
> Ulrich
>
>
>
> ChangeLog:
>
> 2013-11-11  Ulrich Weigand  <Ulrich.Weigand@de.ibm.com>
>
> 	* calls.c (store_unaligned_arguments_into_pseudos): Skip PARALLEL
> 	arguments.
Does this work on the PA, particularly the 32bit ABI?

         /* Structures 5 to 8 bytes in size are passed in the general
             registers in the same manner as other non floating-point
             objects.  The data is right-justified and zero-extended
             to 64 bits.  This is opposite to the normal justification
             used on big endian targets and requires special treatment.
             We now define BLOCK_REG_PADDING to pad these objects.
             Aggregates, complex and vector types are passed in the same
             manner as structures.  */
          if (mode == BLKmode
              || (type && (AGGREGATE_TYPE_P (type)
                           || TREE_CODE (type) == COMPLEX_TYPE
                           || TREE_CODE (type) == VECTOR_TYPE)))
            {
              rtx loc = gen_rtx_EXPR_LIST (VOIDmode,
                                           gen_rtx_REG (DImode, 
gpr_reg_base),
                                           const0_rtx);
              return gen_rtx_PARALLEL (BLKmode, gen_rtvec (1, loc));
            }



It's been eons since I looked at this stuff, so if it's not relevant, 
then just say so and I'll put those concerns aside.

jeff