On Thu, Nov 30, 2017 at 09:26:37AM +0000, Segher Boessenkool wrote:
> This removes use_crosses_set_p, and uses modified_between_p instead
> everywhere it was used. This improves optimisation. I'm a little bit
> worried it might increase compile time; so far I haven't seen it do
> that though.
>
> Longer term I would like to get rid of reg_stat completely, perhaps
> use dataflow everywhere.
>
> Comments/ideas welcome, both on this patch and that longer-term plan.
Since there are no comments, I'll commit it now.
Segher
> 2017-11-30 Segher Boessenkool <seg...@kernel.crashing.org>
>
> * combine.c: Adjust comment.
> (use_crosses_set_p): Delete.
> (can_combine_p): Use modified_between_p instead of use_crosses_set_p.
> (try_combine): Ditto.
>
> ---
> gcc/combine.c | 69
> ++++++-----------------------------------------------------
> 1 file changed, 7 insertions(+), 62 deletions(-)
>
> diff --git a/gcc/combine.c b/gcc/combine.c
> index 22a382d..748c9a8 100644
> --- a/gcc/combine.c
> +++ b/gcc/combine.c
> @@ -39,7 +39,7 @@ along with GCC; see the file COPYING3. If not see
> insn as having a logical link to the preceding insn. The same is true
> for an insn explicitly using CC0.
>
> - We check (with use_crosses_set_p) to avoid combining in such a way
> + We check (with modified_between_p) to avoid combining in such a way
> as to move a computation to a place where its value would be different.
>
> Combination is done by mathematically substituting the previous
> @@ -482,7 +482,6 @@ static void record_dead_and_set_regs_1 (rtx, const_rtx,
> void *);
> static void record_dead_and_set_regs (rtx_insn *);
> static int get_last_value_validate (rtx *, rtx_insn *, int, int);
> static rtx get_last_value (const_rtx);
> -static int use_crosses_set_p (const_rtx, int);
> static void reg_dead_at_p_1 (rtx, const_rtx, void *);
> static int reg_dead_at_p (rtx, rtx_insn *);
> static void move_deaths (rtx, rtx, int, rtx_insn *, rtx *);
> @@ -2011,7 +2010,7 @@ can_combine_p (rtx_insn *insn, rtx_insn *i3, rtx_insn
> *pred ATTRIBUTE_UNUSED,
> || (! all_adjacent
> && (((!MEM_P (src)
> || ! find_reg_note (insn, REG_EQUIV, src))
> - && use_crosses_set_p (src, DF_INSN_LUID (insn)))
> + && modified_between_p (src, insn, i3))
> || (GET_CODE (src) == ASM_OPERANDS && MEM_VOLATILE_P (src))
> || GET_CODE (src) == UNSPEC_VOLATILE))
> /* Don't combine across a CALL_INSN, because that would possibly
> @@ -3727,7 +3726,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1,
> rtx_insn *i0,
> }
> else if (m_split_insn && NEXT_INSN (NEXT_INSN (m_split_insn)) ==
> NULL_RTX
> && (next_nonnote_nondebug_insn (i2) == i3
> - || ! use_crosses_set_p (PATTERN (m_split_insn), DF_INSN_LUID
> (i2))))
> + || !modified_between_p (PATTERN (m_split_insn), i2, i3)))
> {
> rtx i2set, i3set;
> rtx newi3pat = PATTERN (NEXT_INSN (m_split_insn));
> @@ -3791,7 +3790,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1,
> rtx_insn *i0,
> || can_change_dest_mode (i2dest, added_sets_2,
> GET_MODE (*split)))
> && (next_nonnote_nondebug_insn (i2) == i3
> - || ! use_crosses_set_p (*split, DF_INSN_LUID (i2)))
> + || !modified_between_p (*split, i2, i3))
> /* We can't overwrite I2DEST if its value is still used by
> NEWPAT. */
> && ! reg_referenced_p (i2dest, newpat))
> @@ -3982,8 +3981,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1,
> rtx_insn *i0,
> && GET_CODE (XVECEXP (newpat, 0, 1)) == SET
> && rtx_equal_p (SET_SRC (XVECEXP (newpat, 0, 1)),
> XEXP (SET_SRC (XVECEXP (newpat, 0, 0)), 0))
> - && ! use_crosses_set_p (SET_SRC (XVECEXP (newpat, 0, 1)),
> - DF_INSN_LUID (i2))
> + && !modified_between_p (SET_SRC (XVECEXP (newpat, 0, 1)), i2, i3)
> && GET_CODE (SET_DEST (XVECEXP (newpat, 0, 1))) != ZERO_EXTRACT
> && GET_CODE (SET_DEST (XVECEXP (newpat, 0, 1))) != STRICT_LOW_PART
> && ! (temp_expr = SET_DEST (XVECEXP (newpat, 0, 1)),
> @@ -4057,7 +4055,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1,
> rtx_insn *i0,
> be first. The PARALLEL might also have been pre-existing in i3,
> so we need to make sure that we won't wrongly hoist a SET to i2
> that would conflict with a death note present in there. */
> - if (!use_crosses_set_p (SET_SRC (set1), DF_INSN_LUID (i2))
> + if (!modified_between_p (SET_SRC (set1), i2, i3)
> && !(REG_P (SET_DEST (set1))
> && find_reg_note (i2, REG_DEAD, SET_DEST (set1)))
> && !(GET_CODE (SET_DEST (set1)) == SUBREG
> @@ -4072,7 +4070,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1,
> rtx_insn *i0,
> newi2pat = set1;
> newpat = set0;
> }
> - else if (!use_crosses_set_p (SET_SRC (set0), DF_INSN_LUID (i2))
> + else if (!modified_between_p (SET_SRC (set0), i2, i3)
> && !(REG_P (SET_DEST (set0))
> && find_reg_note (i2, REG_DEAD, SET_DEST (set0)))
> && !(GET_CODE (SET_DEST (set0)) == SUBREG
> @@ -13695,59 +13693,6 @@ get_last_value (const_rtx x)
> return 0;
> }
>
> -/* Return nonzero if expression X refers to a REG or to memory
> - that is set in an instruction more recent than FROM_LUID. */
> -
> -static int
> -use_crosses_set_p (const_rtx x, int from_luid)
> -{
> - const char *fmt;
> - int i;
> - enum rtx_code code = GET_CODE (x);
> -
> - if (code == REG)
> - {
> - unsigned int regno = REGNO (x);
> - unsigned endreg = END_REGNO (x);
> -
> -#ifdef PUSH_ROUNDING
> - /* Don't allow uses of the stack pointer to be moved,
> - because we don't know whether the move crosses a push insn. */
> - if (regno == STACK_POINTER_REGNUM && PUSH_ARGS)
> - return 1;
> -#endif
> - for (; regno < endreg; regno++)
> - {
> - reg_stat_type *rsp = ®_stat[regno];
> - if (rsp->last_set
> - && rsp->last_set_label == label_tick
> - && DF_INSN_LUID (rsp->last_set) > from_luid)
> - return 1;
> - }
> - return 0;
> - }
> -
> - if (code == MEM && mem_last_set > from_luid)
> - return 1;
> -
> - fmt = GET_RTX_FORMAT (code);
> -
> - for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
> - {
> - if (fmt[i] == 'E')
> - {
> - int j;
> - for (j = XVECLEN (x, i) - 1; j >= 0; j--)
> - if (use_crosses_set_p (XVECEXP (x, i, j), from_luid))
> - return 1;
> - }
> - else if (fmt[i] == 'e'
> - && use_crosses_set_p (XEXP (x, i), from_luid))
> - return 1;
> - }
> - return 0;
> -}
> -
> /* Define three variables used for communication between the following
> routines. */
>
> --
> 1.8.3.1
