On Tue, 21 Jul 2026, Richard Biener wrote:
> The following makes the recognized INSN_CODEs available to the
> backends for costing via insn_cost.
>
> Bootstrap and regtest running on x86_64-unknown-linux-gnu.
Passed without regressions.
> I have not tried to follow the maze of recog calls in try_combine
> to validate that the three INSN_CODE variables line up with
> the insns costed in combine_validate_cost, but for the single
> i2->i3 combination I looked at it works out.
I used an artificial alternate of myself and that assesses
"Exhaustive tracing of the combine.cc source code confirms that no
mismatch between instruction patterns and INSN_CODEs exists between
combine_validate_cost and try_combine. The instruction codes and
patterns are
kept in perfect, pairwise lockstep throughout every potential path in
try_combine leading up to the cost-validation check."
> IMO calling insn_cost on a non recognized (aka possibly unrecognizable)
> insn doesn't make much sense.
>
> OK? Or am I on the wrong track?
OK for trunk?
Thanks,
Richard.
> Thanks,
> Richard.
>
> PR target/126328
> * combine.cc (combine_validate_cost): New arguments for
> the insn codes. Set INSN_CODE to recognized values
> before calling insn_cost.
> (try_combine): Adjust.
> ---
> gcc/combine.cc | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/gcc/combine.cc b/gcc/combine.cc
> index 53ea168a44b..0711db3f9a6 100644
> --- a/gcc/combine.cc
> +++ b/gcc/combine.cc
> @@ -825,7 +825,8 @@ do_SUBST_LINK (struct insn_link **into, struct insn_link
> *newval)
>
> static bool
> combine_validate_cost (rtx_insn *i0, rtx_insn *i1, rtx_insn *i2, rtx_insn
> *i3,
> - rtx newpat, rtx newi2pat, rtx newotherpat)
> + rtx newpat, rtx newi2pat, rtx newotherpat,
> + int insn_code, int i2_code, int other_code)
> {
> int i0_cost, i1_cost, i2_cost, i3_cost;
> int new_i2_cost, new_i3_cost;
> @@ -867,7 +868,7 @@ combine_validate_cost (rtx_insn *i0, rtx_insn *i1,
> rtx_insn *i2, rtx_insn *i3,
> rtx tmp = PATTERN (i3);
> PATTERN (i3) = newpat;
> int tmpi = INSN_CODE (i3);
> - INSN_CODE (i3) = -1;
> + INSN_CODE (i3) = insn_code;
> new_i3_cost = insn_cost (i3, optimize_this_for_speed_p);
> PATTERN (i3) = tmp;
> INSN_CODE (i3) = tmpi;
> @@ -876,7 +877,7 @@ combine_validate_cost (rtx_insn *i0, rtx_insn *i1,
> rtx_insn *i2, rtx_insn *i3,
> tmp = PATTERN (i2);
> PATTERN (i2) = newi2pat;
> tmpi = INSN_CODE (i2);
> - INSN_CODE (i2) = -1;
> + INSN_CODE (i2) = i2_code;
> new_i2_cost = insn_cost (i2, optimize_this_for_speed_p);
> PATTERN (i2) = tmp;
> INSN_CODE (i2) = tmpi;
> @@ -897,7 +898,7 @@ combine_validate_cost (rtx_insn *i0, rtx_insn *i1,
> rtx_insn *i2, rtx_insn *i3,
> tmp = PATTERN (undobuf.other_insn);
> PATTERN (undobuf.other_insn) = newotherpat;
> tmpi = INSN_CODE (undobuf.other_insn);
> - INSN_CODE (undobuf.other_insn) = -1;
> + INSN_CODE (undobuf.other_insn) = other_code;
> new_other_cost = insn_cost (undobuf.other_insn,
> optimize_this_for_speed_p);
> PATTERN (undobuf.other_insn) = tmp;
> @@ -4134,7 +4135,9 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1,
> rtx_insn *i0,
>
> /* Reject this combination if insn_cost reports that the replacement
> instructions are more expensive than the originals. */
> - if (!combine_validate_cost (i0, i1, i2, i3, newpat, newi2pat, other_pat))
> + if (!combine_validate_cost (i0, i1, i2, i3, newpat, newi2pat, other_pat,
> + insn_code_number, i2_code_number,
> + other_code_number))
> {
> undo_all ();
> return 0;
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Jochen Jaser, Andrew McDonald, Abhinav Puri; (HRB 36809, AG Nuernberg)
