On Mon, Apr 28, 2025 at 2:38 PM Richard Sandiford
<richard.sandif...@arm.com> wrote:
>
> native_decode_rtx handles integer modes by building up a wide_int
> and then converting it to an rtx. This patch splits out the
> wide_int part, so that callers who don't want an rtx can avoid
> creating garbage rtl.
>
> Bootstrapped & regression-tested on aarch64-linux-gnu. OK to install?
OK.
> Richard
>
>
> gcc/
> * rtl.h (native_decode_int): Declare.
> * simplify-rtx.cc (native_decode_int): New function, split out from...
> (native_decode_rtx): ...here.
> ---
> gcc/rtl.h | 2 ++
> gcc/simplify-rtx.cc | 38 +++++++++++++++++++++++++-------------
> 2 files changed, 27 insertions(+), 13 deletions(-)
>
> diff --git a/gcc/rtl.h b/gcc/rtl.h
> index 3b676c46880..cc25aed1f49 100644
> --- a/gcc/rtl.h
> +++ b/gcc/rtl.h
> @@ -2443,6 +2443,8 @@ extern void get_full_rtx_cost (rtx, machine_mode, enum
> rtx_code, int,
> struct full_rtx_costs *);
> extern bool native_encode_rtx (machine_mode, rtx, vec<target_unit> &,
> unsigned int, unsigned int);
> +extern wide_int native_decode_int (const vec<target_unit> &, unsigned int,
> + unsigned int, unsigned int);
> extern rtx native_decode_rtx (machine_mode, const vec<target_unit> &,
> unsigned int);
> extern rtx native_decode_vector_rtx (machine_mode, const vec<target_unit> &,
> diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
> index 88d31a71c05..0e0a908aa38 100644
> --- a/gcc/simplify-rtx.cc
> +++ b/gcc/simplify-rtx.cc
> @@ -7702,6 +7702,28 @@ native_decode_vector_rtx (machine_mode mode, const
> vec<target_unit> &bytes,
> return builder.build ();
> }
>
> +/* Extract a PRECISION-bit integer from bytes [FIRST_BYTE, FIRST_BYTE + SIZE)
> + of target memory image BYTES. */
> +
> +wide_int
> +native_decode_int (const vec<target_unit> &bytes, unsigned int first_byte,
> + unsigned int size, unsigned int precision)
> +{
> + /* Pull the bytes msb first, so that we can use simple
> + shift-and-insert wide_int operations. */
> + wide_int result (wi::zero (precision));
> + for (unsigned int i = 0; i < size; ++i)
> + {
> + unsigned int lsb = (size - i - 1) * BITS_PER_UNIT;
> + /* Always constant because the inputs are. */
> + unsigned int subbyte
> + = subreg_size_offset_from_lsb (1, size, lsb).to_constant ();
> + result <<= BITS_PER_UNIT;
> + result |= bytes[first_byte + subbyte];
> + }
> + return result;
> +}
> +
> /* Read an rtx of mode MODE from the target memory image given by BYTES,
> starting at byte FIRST_BYTE. Each element of BYTES contains BITS_PER_UNIT
> bits and the bytes are in target memory order. The image has enough
> @@ -7727,19 +7749,9 @@ native_decode_rtx (machine_mode mode, const
> vec<target_unit> &bytes,
> if (is_a <scalar_int_mode> (mode, &imode)
> && GET_MODE_PRECISION (imode) <= MAX_BITSIZE_MODE_ANY_INT)
> {
> - /* Pull the bytes msb first, so that we can use simple
> - shift-and-insert wide_int operations. */
> - unsigned int size = GET_MODE_SIZE (imode);
> - wide_int result (wi::zero (GET_MODE_PRECISION (imode)));
> - for (unsigned int i = 0; i < size; ++i)
> - {
> - unsigned int lsb = (size - i - 1) * BITS_PER_UNIT;
> - /* Always constant because the inputs are. */
> - unsigned int subbyte
> - = subreg_size_offset_from_lsb (1, size, lsb).to_constant ();
> - result <<= BITS_PER_UNIT;
> - result |= bytes[first_byte + subbyte];
> - }
> + auto result = native_decode_int (bytes, first_byte,
> + GET_MODE_SIZE (imode),
> + GET_MODE_PRECISION (imode));
> return immed_wide_int_const (result, imode);
> }
>
> --
> 2.43.0
>
