Jakub Jelinek <ja...@redhat.com> writes:
> Hi!
>
> As the following testcase shows, we emit a -Wpsabi note about argument
> passing change since GCC 9, but in reality the ABI didn't change.
> The alignment is 8 bits in GCC < 9 and 32 bits in GCC >= 9 and
> the aarch64_function_arg_alignment returns in that case:
> return MIN (MAX (alignment, PARM_BOUNDARY), STACK_BOUNDARY);
> so when both the old and new alignment are smaller or equal to PARM_BOUNDARY
> (or both are larger than STACK_BOUNDARY, just in theory), even when the new
> one is bigger, it doesn't change the argument passing.
>
> So, the following patch changes aarch64_function_arg_alignment to tell the
> callers the exact old alignmentm so that they can test it if needed.
> The other aarch64_function_arg_alignment callers either check the
> alignment for equality against 16-byte alignment (when old alignment was
> smaller than that and the new one is 16-byte, we want to emit -Wpsabi
> in all the cases) or the va_arg case which I think is ok now too.
>
> Bootstrapped/regtested on aarch64-linux, ok for trunk?
Looks good to me. Richard E knows this code better than I do though,
so I think he should have the final say. He's currently on holiday
but will be back next week.
Thanks,
Richard
>
> 2021-03-18 Jakub Jelinek <ja...@redhat.com>
>
> PR target/91710
> * config/aarch64/aarch64.c (aarch64_function_arg_alignment): Change
> abi_break argument from bool * to unsigned *, store there the pre-GCC 9
> alignment.
> (aarch64_layout_arg, aarch64_gimplify_va_arg_expr): Adjust callers.
> (aarch64_function_arg_regno_p): Likewise. Only emit -Wpsabi note if
> the old and new alignment after applying MIN/MAX to it is different.
>
> * gcc.target/aarch64/pr91710.c: New test.
>
> --- gcc/config/aarch64/aarch64.c.jj 2021-03-18 15:14:51.721425223 +0100
> +++ gcc/config/aarch64/aarch64.c 2021-03-18 16:35:04.437115447 +0100
> @@ -5938,9 +5938,9 @@ aarch64_vfp_is_call_candidate (cumulativ
>
> static unsigned int
> aarch64_function_arg_alignment (machine_mode mode, const_tree type,
> - bool *abi_break)
> + unsigned int *abi_break)
> {
> - *abi_break = false;
> + *abi_break = 0;
> if (!type)
> return GET_MODE_ALIGNMENT (mode);
>
> @@ -5982,7 +5982,7 @@ aarch64_function_arg_alignment (machine_
>
> if (bitfield_alignment > alignment)
> {
> - *abi_break = true;
> + *abi_break = alignment;
> return bitfield_alignment;
> }
>
> @@ -6004,7 +6004,7 @@ aarch64_layout_arg (cumulative_args_t pc
> int ncrn, nvrn, nregs;
> bool allocate_ncrn, allocate_nvrn;
> HOST_WIDE_INT size;
> - bool abi_break;
> + unsigned int abi_break;
>
> /* We need to do this once per argument. */
> if (pcum->aapcs_arg_processed)
> @@ -6322,14 +6322,19 @@ aarch64_function_arg_regno_p (unsigned r
> static unsigned int
> aarch64_function_arg_boundary (machine_mode mode, const_tree type)
> {
> - bool abi_break;
> + unsigned int abi_break;
> unsigned int alignment = aarch64_function_arg_alignment (mode, type,
> &abi_break);
> + alignment = MIN (MAX (alignment, PARM_BOUNDARY), STACK_BOUNDARY);
> if (abi_break & warn_psabi)
> - inform (input_location, "parameter passing for argument of type "
> - "%qT changed in GCC 9.1", type);
> + {
> + abi_break = MIN (MAX (abi_break, PARM_BOUNDARY), STACK_BOUNDARY);
> + if (alignment != abi_break)
> + inform (input_location, "parameter passing for argument of type "
> + "%qT changed in GCC 9.1", type);
> + }
>
> - return MIN (MAX (alignment, PARM_BOUNDARY), STACK_BOUNDARY);
> + return alignment;
> }
>
> /* Implement TARGET_GET_RAW_RESULT_MODE and TARGET_GET_RAW_ARG_MODE. */
> @@ -16616,7 +16621,7 @@ aarch64_gimplify_va_arg_expr (tree valis
> f_stack, NULL_TREE);
> size = int_size_in_bytes (type);
>
> - bool abi_break;
> + unsigned int abi_break;
> align
> = aarch64_function_arg_alignment (mode, type, &abi_break) /
> BITS_PER_UNIT;
>
> --- gcc/testsuite/gcc.target/aarch64/pr91710.c.jj 2021-03-18
> 16:42:33.529232710 +0100
> +++ gcc/testsuite/gcc.target/aarch64/pr91710.c 2021-03-18
> 16:42:07.271518121 +0100
> @@ -0,0 +1,16 @@
> +/* PR target/91710 */
> +/* { dg-do compile } */
> +
> +struct S { unsigned int i:4; };
> +
> +unsigned int test1(struct S s) { /* { dg-bogus "parameter passing for
> argument of type" } */
> + return s.i;
> +}
> +
> +unsigned int test2(unsigned x, struct S s) { /* { dg-bogus "parameter
> passing for argument of type" } */
> + return x - s.i;
> +}
> +
> +unsigned int test3(unsigned x, unsigned y, struct S s) { /* { dg-bogus
> "parameter passing for argument of type" } */
> + return x - y - s.i;
> +}
>
> Jakub
