just one more nit: Use INVALID_REGNUM as sentinel value for
riscv_next_saved_reg, otherwise LGTM, and feel free to commit that
separately :)
On Mon, Dec 19, 2022 at 9:08 AM Christoph Muellner
<christoph.muell...@vrull.eu> wrote:
>
> From: Christoph Müllner <christoph.muell...@vrull.eu>
>
> This patch restructures the loop over the GP registers
> which saves/restores then as part of the prologue/epilogue.
> No functional change is intended by this patch, but it
> offers the possibility to use load-pair/store-pair instructions.
>
> gcc/ChangeLog:
>
> * config/riscv/riscv.cc (riscv_next_saved_reg): New function.
> (riscv_is_eh_return_data_register): New function.
> (riscv_for_each_saved_reg): Restructure loop.
>
> Signed-off-by: Christoph Müllner <christoph.muell...@vrull.eu>
> ---
> gcc/config/riscv/riscv.cc | 94 +++++++++++++++++++++++++++------------
> 1 file changed, 66 insertions(+), 28 deletions(-)
>
> diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
> index 6dd2ab2d11e..a8d5e1dac7f 100644
> --- a/gcc/config/riscv/riscv.cc
> +++ b/gcc/config/riscv/riscv.cc
> @@ -4835,6 +4835,49 @@ riscv_save_restore_reg (machine_mode mode, int regno,
> fn (gen_rtx_REG (mode, regno), mem);
> }
>
> +/* Return the next register up from REGNO up to LIMIT for the callee
> + to save or restore. OFFSET will be adjusted accordingly.
> + If INC is set, then REGNO will be incremented first. */
> +
> +static unsigned int
> +riscv_next_saved_reg (unsigned int regno, unsigned int limit,
> + HOST_WIDE_INT *offset, bool inc = true)
> +{
> + if (inc)
> + regno++;
> +
> + while (regno <= limit)
> + {
> + if (BITSET_P (cfun->machine->frame.mask, regno - GP_REG_FIRST))
> + {
> + *offset = *offset - UNITS_PER_WORD;
> + break;
> + }
> +
> + regno++;
> + }
> + return regno;
> +}
> +
> +/* Return TRUE if provided REGNO is eh return data register. */
> +
> +static bool
> +riscv_is_eh_return_data_register (unsigned int regno)
> +{
> + unsigned int i, regnum;
> +
> + if (!crtl->calls_eh_return)
> + return false;
> +
> + for (i = 0; (regnum = EH_RETURN_DATA_REGNO (i)) != INVALID_REGNUM; i++)
> + if (regno == regnum)
> + {
> + return true;
> + }
> +
> + return false;
> +}
> +
> /* Call FN for each register that is saved by the current function.
> SP_OFFSET is the offset of the current stack pointer from the start
> of the frame. */
> @@ -4844,36 +4887,31 @@ riscv_for_each_saved_reg (poly_int64 sp_offset,
> riscv_save_restore_fn fn,
> bool epilogue, bool maybe_eh_return)
> {
> HOST_WIDE_INT offset;
> + unsigned int regno;
> + unsigned int start = GP_REG_FIRST;
> + unsigned int limit = GP_REG_LAST;
>
> /* Save the link register and s-registers. */
> - offset = (cfun->machine->frame.gp_sp_offset - sp_offset).to_constant ();
> - for (unsigned int regno = GP_REG_FIRST; regno <= GP_REG_LAST; regno++)
> - if (BITSET_P (cfun->machine->frame.mask, regno - GP_REG_FIRST))
> - {
> - bool handle_reg = !cfun->machine->reg_is_wrapped_separately[regno];
> -
> - /* If this is a normal return in a function that calls the eh_return
> - builtin, then do not restore the eh return data registers as that
> - would clobber the return value. But we do still need to save them
> - in the prologue, and restore them for an exception return, so we
> - need special handling here. */
> - if (epilogue && !maybe_eh_return && crtl->calls_eh_return)
> - {
> - unsigned int i, regnum;
> -
> - for (i = 0; (regnum = EH_RETURN_DATA_REGNO (i)) != INVALID_REGNUM;
> - i++)
> - if (regno == regnum)
> - {
> - handle_reg = FALSE;
> - break;
> - }
> - }
> -
> - if (handle_reg)
> - riscv_save_restore_reg (word_mode, regno, offset, fn);
> - offset -= UNITS_PER_WORD;
> - }
> + offset = (cfun->machine->frame.gp_sp_offset - sp_offset).to_constant ()
> + + UNITS_PER_WORD;
> + for (regno = riscv_next_saved_reg (start, limit, &offset, false);
> + regno <= limit;
> + regno = riscv_next_saved_reg (regno, limit, &offset))
> + {
> + if (cfun->machine->reg_is_wrapped_separately[regno])
> + continue;
> +
> + /* If this is a normal return in a function that calls the eh_return
> + builtin, then do not restore the eh return data registers as that
> + would clobber the return value. But we do still need to save them
> + in the prologue, and restore them for an exception return, so we
> + need special handling here. */
> + if (epilogue && !maybe_eh_return
> + && riscv_is_eh_return_data_register (regno))
> + continue;
> +
> + riscv_save_restore_reg (word_mode, regno, offset, fn);
> + }
>
> /* This loop must iterate over the same space as its companion in
> riscv_compute_frame_info. */
> --
> 2.38.1
>
