On Tue, 25 Jul 2023, Richard Biener wrote:
> The following removes the code checking whether a noop copy
> is between something involved in the return sequence composed
> of a SET and USE. Instead of checking for this special-case
> the following makes us only ever remove noop copies between
> pseudos - which is the case that is necessary for IRA/LRA
> interfacing to function according to the comment. That makes
> looking for the return reg special case unnecessary, reducing
> the compile-time in LRA non-specific to zero for the testcase.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu with
> all languages and {,-m32}.
>
> OK?
Ping.
> Thanks,
> Richard.
>
> PR rtl-optimization/110587
> * lra-spills.cc (return_regno_p): Remove.
> (regno_in_use_p): Likewise.
> (lra_final_code_change): Do not remove noop moves
> between hard registers.
> ---
> gcc/lra-spills.cc | 69 +----------------------------------------------
> 1 file changed, 1 insertion(+), 68 deletions(-)
>
> diff --git a/gcc/lra-spills.cc b/gcc/lra-spills.cc
> index 3a7bb7e8cd9..fe58f162d05 100644
> --- a/gcc/lra-spills.cc
> +++ b/gcc/lra-spills.cc
> @@ -705,72 +705,6 @@ alter_subregs (rtx *loc, bool final_p)
> return res;
> }
>
> -/* Return true if REGNO is used for return in the current
> - function. */
> -static bool
> -return_regno_p (unsigned int regno)
> -{
> - rtx outgoing = crtl->return_rtx;
> -
> - if (! outgoing)
> - return false;
> -
> - if (REG_P (outgoing))
> - return REGNO (outgoing) == regno;
> - else if (GET_CODE (outgoing) == PARALLEL)
> - {
> - int i;
> -
> - for (i = 0; i < XVECLEN (outgoing, 0); i++)
> - {
> - rtx x = XEXP (XVECEXP (outgoing, 0, i), 0);
> -
> - if (REG_P (x) && REGNO (x) == regno)
> - return true;
> - }
> - }
> - return false;
> -}
> -
> -/* Return true if REGNO is in one of subsequent USE after INSN in the
> - same BB. */
> -static bool
> -regno_in_use_p (rtx_insn *insn, unsigned int regno)
> -{
> - static lra_insn_recog_data_t id;
> - static struct lra_static_insn_data *static_id;
> - struct lra_insn_reg *reg;
> - int i, arg_regno;
> - basic_block bb = BLOCK_FOR_INSN (insn);
> -
> - while ((insn = next_nondebug_insn (insn)) != NULL_RTX)
> - {
> - if (BARRIER_P (insn) || bb != BLOCK_FOR_INSN (insn))
> - return false;
> - if (! INSN_P (insn))
> - continue;
> - if (GET_CODE (PATTERN (insn)) == USE
> - && REG_P (XEXP (PATTERN (insn), 0))
> - && regno == REGNO (XEXP (PATTERN (insn), 0)))
> - return true;
> - /* Check that the regno is not modified. */
> - id = lra_get_insn_recog_data (insn);
> - for (reg = id->regs; reg != NULL; reg = reg->next)
> - if (reg->type != OP_IN && reg->regno == (int) regno)
> - return false;
> - static_id = id->insn_static_data;
> - for (reg = static_id->hard_regs; reg != NULL; reg = reg->next)
> - if (reg->type != OP_IN && reg->regno == (int) regno)
> - return false;
> - if (id->arg_hard_regs != NULL)
> - for (i = 0; (arg_regno = id->arg_hard_regs[i]) >= 0; i++)
> - if ((int) regno == (arg_regno >= FIRST_PSEUDO_REGISTER
> - ? arg_regno : arg_regno - FIRST_PSEUDO_REGISTER))
> - return false;
> - }
> - return false;
> -}
> -
> /* Final change of pseudos got hard registers into the corresponding
> hard registers and removing temporary clobbers. */
> void
> @@ -821,8 +755,7 @@ lra_final_code_change (void)
> if (NONJUMP_INSN_P (insn) && GET_CODE (pat) == SET
> && REG_P (SET_SRC (pat)) && REG_P (SET_DEST (pat))
> && REGNO (SET_SRC (pat)) == REGNO (SET_DEST (pat))
> - && (! return_regno_p (REGNO (SET_SRC (pat)))
> - || ! regno_in_use_p (insn, REGNO (SET_SRC (pat)))))
> + && REGNO (SET_SRC (pat)) >= FIRST_PSEUDO_REGISTER)
> {
> lra_invalidate_insn_data (insn);
> delete_insn (insn);
>
