Richard Henderson <richard.hender...@linaro.org> writes:
> Duplicate all usub_*_carryinC, but use xzr for the output when we
> only require the flags output. The signed versions use sign_extend
> instead of zero_extend for combine's benefit.
>
> These will be used shortly for TImode comparisons.
>
> * config/aarch64/aarch64.md (<su>cmp<GPI>3_carryinC): New.
> (*<su>cmp<GPI>3_carryinC_z1): New.
> (*<su>cmp<GPI>3_carryinC_z2): New.
> (*<su>cmp<GPI>3_carryinC): New.
> ---
> gcc/config/aarch64/aarch64.md | 50 +++++++++++++++++++++++++++++++++++
> 1 file changed, 50 insertions(+)
>
> diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
> index a996a5f1c39..9b1c3f797f9 100644
> --- a/gcc/config/aarch64/aarch64.md
> +++ b/gcc/config/aarch64/aarch64.md
> @@ -3440,6 +3440,18 @@
> ""
> )
>
> +(define_expand "<ANY_EXTEND:su>cmp<GPI:mode>3_carryinC"
> + [(set (reg:CC CC_REGNUM)
> + (compare:CC
> + (ANY_EXTEND:<DWI>
> + (match_operand:GPI 0 "register_operand"))
> + (plus:<DWI>
> + (ANY_EXTEND:<DWI>
> + (match_operand:GPI 1 "register_operand"))
> + (ltu:<DWI> (reg:CC CC_REGNUM) (const_int 0)))))]
> + ""
> +)
> (define_insn "*usub<GPI:mode>3_carryinC_z1"
> [(set (reg:CC CC_REGNUM)
> (compare:CC
> @@ -3457,6 +3469,19 @@
> [(set_attr "type" "adc_reg")]
> )
>
> +(define_insn "*<ANY_EXTEND:su>cmp<GPI:mode>3_carryinC_z1"
> + [(set (reg:CC CC_REGNUM)
> + (compare:CC
> + (const_int 0)
> + (plus:<DWI>
> + (ANY_EXTEND:<DWI>
> + (match_operand:GPI 0 "register_operand" "r"))
> + (match_operand:<DWI> 1 "aarch64_borrow_operation" ""))))]
> + ""
> + "sbcs\\t<w>zr, <w>zr, %<w>0"
> + [(set_attr "type" "adc_reg")]
> +)
> +
> (define_insn "*usub<GPI:mode>3_carryinC_z2"
> [(set (reg:CC CC_REGNUM)
> (compare:CC
> @@ -3472,6 +3497,17 @@
> [(set_attr "type" "adc_reg")]
> )
>
> +(define_insn "*<ANY_EXTEND:su>cmp<GPI:mode>3_carryinC_z2"
> + [(set (reg:CC CC_REGNUM)
> + (compare:CC
> + (ANY_EXTEND:<DWI>
> + (match_operand:GPI 0 "register_operand" "r"))
> + (match_operand:<DWI> 1 "aarch64_borrow_operation" "")))]
> + ""
> + "sbcs\\t<w>zr, %<w>0, <w>zr"
> + [(set_attr "type" "adc_reg")]
> +)
> +
> (define_insn "*usub<GPI:mode>3_carryinC"
> [(set (reg:CC CC_REGNUM)
> (compare:CC
> @@ -3490,6 +3526,20 @@
> [(set_attr "type" "adc_reg")]
> )
>
> +(define_insn "*<ANY_EXTEND:su>cmp<GPI:mode>3_carryinC"
> + [(set (reg:CC CC_REGNUM)
> + (compare:CC
> + (ANY_EXTEND:<DWI>
> + (match_operand:GPI 0 "register_operand" "r"))
> + (plus:<DWI>
> + (ANY_EXTEND:<DWI>
> + (match_operand:GPI 1 "register_operand" "r"))
> + (match_operand:<DWI> 2 "aarch64_borrow_operation" ""))))]
> + ""
> + "sbcs\\t<w>zr, %<w>0, %<w>1"
> + [(set_attr "type" "adc_reg")]
> +)
I guess this feeds into your reply to Segher's comment for 7/9,
but I think:
(compare:CC X Y)
is always supposed to be the NZCV flags result of X - Y, as computed in
the mode of X and Y. If so, it seems like the type of extension should
matter. E.g. the N flag ought to be set for:
(compare:CC
(sign_extend 0xf...)
(plus (sign_extend 0x7...)
(ltu ...)))
but ought to be clear for:
(compare:CC
(zero_extend 0xf...)
(plus (zero_extend 0x7...)
(ltu ...)))
If so, I guess this is a bug in the existing code...
Thanks,
Richard
