Re: [PATCH] AArch64: Add support for __builtin_roundeven[f] [PR100966]

[Richard Sandiford <richard.sandiford@arm.com>]

Wilco Dijkstra <Wilco.Dijkstra@arm.com> writes:
> Enable __builtin_roundeven[f] by adding roundeven as an alias to the
> existing frintn support.

Although frint_pattern maps UNSPEC_FRINTN to "frintn", "frintn"
doesn't mean anything to the target-independent part of the compiler.
I assume it was just picked as a placeholder since the roundeven
optabs didn't exist at the time.

So rather than have two patterns that generate frintn, I think
it would be better to change the existing frint_pattern entry to
"roundeven" instead, and fix whatever the fallout is.  Hopefully it
shouldn't be too bad, since we already use the optab names for the
other UNSPEC_FRINT* codes.

Thanks,
Richard

> Bootstrap OK and passes regress.
>
> ChangeLog:
> 2021-06-18  Wilco Dijkstra  <wdijkstr@arm.com>
>
>         PR target/100966
>         * config/aarch64/aarch64.md (UNSPEC_FRINTR): Add.
>         * config/aarch64/aarch64.c (aarch64_frint_unspec_p): Add UNSPEC_FRINTR.
>         (aarch64_rtx_cost): Likewise.
>         * config/aarch64/iterators.md (FRINT): Add UNSPEC_FRINTR.
>         (frint_pattern): Likewise.
>         (frint_suffix): Likewise.
>
> gcc/testsuite
>         PR target/100966
>         * gcc.target/aarch64/frint.x: Add roundeven tests.
>         * gcc.target/aarch64/frint_double.c: Likewise.
>         * gcc.target/aarch64/frint_float.c: Likewise.
>
> ---
>
> diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
> index f4d264bbc817153b330bac9ab423bf561689ebf2..63bd49d475433c04faa89bb380a9d17e4ad4bc6c 100644
> --- a/gcc/config/aarch64/aarch64.c
> +++ b/gcc/config/aarch64/aarch64.c
> @@ -12253,6 +12253,7 @@ aarch64_frint_unspec_p (unsigned int u)
>        case UNSPEC_FRINTM:
>        case UNSPEC_FRINTA:
>        case UNSPEC_FRINTN:
> +      case UNSPEC_FRINTR:
>        case UNSPEC_FRINTX:
>        case UNSPEC_FRINTI:
>          return true;
> @@ -13648,6 +13649,7 @@ cost_plus:
>                || uns_code == UNSPEC_FRINTM
>                || uns_code == UNSPEC_FRINTN
>                || uns_code == UNSPEC_FRINTP
> +             || uns_code == UNSPEC_FRINTR
>                || uns_code == UNSPEC_FRINTZ)
>              x = XVECEXP (x, 0, 0);
>          }
> diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
> index 30effca6f3562f6870a6cc8097750e63bb0d424d..70e46f28259640a273d444a2b963246ed9a91109 100644
> --- a/gcc/config/aarch64/aarch64.md
> +++ b/gcc/config/aarch64/aarch64.md
> @@ -167,6 +167,7 @@ (define_c_enum "unspec" [
>      UNSPEC_FRINTM
>      UNSPEC_FRINTN
>      UNSPEC_FRINTP
> +    UNSPEC_FRINTR
>      UNSPEC_FRINTX
>      UNSPEC_FRINTZ
>      UNSPEC_GOTSMALLPIC
> diff --git a/gcc/config/aarch64/iterators.md b/gcc/config/aarch64/iterators.md
> index cac33ae812b382cd55611b0da8a6e9eac3a513c4..1542661c6d101ed53c6e1c8683cbca32baefebbd 100644
> --- a/gcc/config/aarch64/iterators.md
> +++ b/gcc/config/aarch64/iterators.md
> @@ -2291,7 +2291,7 @@ (define_int_iterator REVERSE [UNSPEC_REV64 UNSPEC_REV32 UNSPEC_REV16])
>
>  (define_int_iterator FRINT [UNSPEC_FRINTZ UNSPEC_FRINTP UNSPEC_FRINTM
>                              UNSPEC_FRINTN UNSPEC_FRINTI UNSPEC_FRINTX
> -                            UNSPEC_FRINTA])
> +                            UNSPEC_FRINTA UNSPEC_FRINTR ])
>
>  (define_int_iterator FCVT [UNSPEC_FRINTZ UNSPEC_FRINTP UNSPEC_FRINTM
>                             UNSPEC_FRINTA UNSPEC_FRINTN])
> @@ -3079,13 +3079,14 @@ (define_int_attr frint_pattern [(UNSPEC_FRINTZ "btrunc")
>                                 (UNSPEC_FRINTI "nearbyint")
>                                 (UNSPEC_FRINTX "rint")
>                                 (UNSPEC_FRINTA "round")
> -                               (UNSPEC_FRINTN "frintn")])
> +                               (UNSPEC_FRINTN "frintn")
> +                               (UNSPEC_FRINTR "roundeven")])
>
>  ;; frint suffix for floating-point rounding instructions.
>  (define_int_attr frint_suffix [(UNSPEC_FRINTZ "z") (UNSPEC_FRINTP "p")
>                                (UNSPEC_FRINTM "m") (UNSPEC_FRINTI "i")
>                                (UNSPEC_FRINTX "x") (UNSPEC_FRINTA "a")
> -                              (UNSPEC_FRINTN "n")])
> +                              (UNSPEC_FRINTN "n") (UNSPEC_FRINTR "n")])
>
>  (define_int_attr fcvt_pattern [(UNSPEC_FRINTZ "btrunc") (UNSPEC_FRINTA "round")
>                                (UNSPEC_FRINTP "ceil") (UNSPEC_FRINTM "floor")
> diff --git a/gcc/testsuite/gcc.target/aarch64/frint.x b/gcc/testsuite/gcc.target/aarch64/frint.x
> index 1403740686ea3927d2c39eb2466ef8cc67e223b2..d598a25ff21b8feeca6a96de79848b2fbde7f31e 100644
> --- a/gcc/testsuite/gcc.target/aarch64/frint.x
> +++ b/gcc/testsuite/gcc.target/aarch64/frint.x
> @@ -4,6 +4,7 @@ extern GPF SUFFIX(floor) (GPF);
>  extern GPF SUFFIX(nearbyint) (GPF);
>  extern GPF SUFFIX(rint) (GPF);
>  extern GPF SUFFIX(round) (GPF);
> +extern GPF SUFFIX(roundeven) (GPF);
>
>  GPF test1a (GPF x)
>  {
> @@ -64,3 +65,14 @@ GPF test6b (GPF x)
>  {
>    return SUFFIX(round)(x);
>  }
> +
> +GPF test7a (GPF x)
> +{
> +  return SUFFIX(__builtin_roundeven)(x);
> +}
> +
> +GPF test7b (GPF x)
> +{
> +  return SUFFIX(roundeven)(x);
> +}
> +
> diff --git a/gcc/testsuite/gcc.target/aarch64/frint_double.c b/gcc/testsuite/gcc.target/aarch64/frint_double.c
> index 96139496ca454cebd41d31e8b018dab7ffa33a3f..1d28eb09e11842802ab632a7696de4407263f8ce 100644
> --- a/gcc/testsuite/gcc.target/aarch64/frint_double.c
> +++ b/gcc/testsuite/gcc.target/aarch64/frint_double.c
> @@ -12,3 +12,4 @@
>  /* { dg-final { scan-assembler-times "frinti\td\[0-9\]" 2 } } */
>  /* { dg-final { scan-assembler-times "frintx\td\[0-9\]" 2 } } */
>  /* { dg-final { scan-assembler-times "frinta\td\[0-9\]" 2 } } */
> +/* { dg-final { scan-assembler-times "frintn\td\[0-9\]" 2 } } */
> diff --git a/gcc/testsuite/gcc.target/aarch64/frint_float.c b/gcc/testsuite/gcc.target/aarch64/frint_float.c
> index 493ec37f940a6e8cb01ea7e324073fa22099636c..530cf975db3d52c30bce43d0c40229b2b375cdea 100644
> --- a/gcc/testsuite/gcc.target/aarch64/frint_float.c
> +++ b/gcc/testsuite/gcc.target/aarch64/frint_float.c
> @@ -12,3 +12,4 @@
>  /* { dg-final { scan-assembler-times "frinti\ts\[0-9\]" 2 } } */
>  /* { dg-final { scan-assembler-times "frintx\ts\[0-9\]" 2 } } */
>  /* { dg-final { scan-assembler-times "frinta\ts\[0-9\]" 2 } } */
> +/* { dg-final { scan-assembler-times "frintn\ts\[0-9\]" 2 } } */