From: Richard Sandiford <richard.sandiford@arm.com>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: gcc-patches@gcc.gnu.org, richard.earnshaw@arm.com,
marcus.shawcroft@arm.com, kyrylo.tkachov@arm.com,
Wilco.Dijkstra@arm.com
Subject: Re: [PATCH v2 1/9] aarch64: Accept 0 as first argument to compares
Date: Tue, 31 Mar 2020 17:55:44 +0100 [thread overview]
Message-ID: <mptr1x8a2gf.fsf@arm.com> (raw)
In-Reply-To: <20200321024231.13778-2-richard.henderson@linaro.org> (Richard Henderson's message of "Fri, 20 Mar 2020 19:42:23 -0700")
Richard Henderson <richard.henderson@linaro.org> writes:
> While cmp (extended register) and cmp (immediate) uses <Wn|WSP>,
> cmp (shifted register) uses <Wn>. So we can perform cmp xzr, x0.
>
> For ccmp, we only have <Wn> as an input.
>
> * config/aarch64/aarch64.md (cmp<GPI>): For operand 0, use
> aarch64_reg_or_zero. Shuffle reg/reg to last alternative
> and accept Z.
> (@ccmpcc<GPI>): For operand 0, use aarch64_reg_or_zero and Z.
> (@ccmpcc<GPI>_rev): Likewise.
Looks good, but...
> ---
> gcc/config/aarch64/aarch64.md | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
> index c7c4d1dd519..b9ae51e48dd 100644
> --- a/gcc/config/aarch64/aarch64.md
> +++ b/gcc/config/aarch64/aarch64.md
> @@ -502,7 +502,7 @@
> [(match_operand 0 "cc_register" "")
> (const_int 0)])
> (compare:CC_ONLY
> - (match_operand:GPI 2 "register_operand" "r,r,r")
> + (match_operand:GPI 2 "aarch64_reg_or_zero" "rZ,rZ,rZ")
> (match_operand:GPI 3 "aarch64_ccmp_operand" "r,Uss,Usn"))
> (unspec:CC_ONLY
> [(match_operand 5 "immediate_operand")]
> @@ -542,7 +542,7 @@
> [(match_operand 5 "immediate_operand")]
> UNSPEC_NZCV)
> (compare:CC_ONLY
> - (match_operand:GPI 2 "register_operand" "r,r,r")
> + (match_operand:GPI 2 "aarch64_reg_or_zero" "rZ,rZ,rZ")
> (match_operand:GPI 3 "aarch64_ccmp_operand" "r,Uss,Usn"))))]
> ""
> "@
> @@ -3961,14 +3961,14 @@
>
> (define_insn "cmp<mode>"
> [(set (reg:CC CC_REGNUM)
> - (compare:CC (match_operand:GPI 0 "register_operand" "rk,rk,rk")
> - (match_operand:GPI 1 "aarch64_plus_operand" "r,I,J")))]
> + (compare:CC (match_operand:GPI 0 "aarch64_reg_or_zero" "rk,rk,rkZ")
> + (match_operand:GPI 1 "aarch64_plus_operand" "I,J,rZ")))]
> ""
> "@
> - cmp\\t%<w>0, %<w>1
> cmp\\t%<w>0, %1
> - cmn\\t%<w>0, #%n1"
> - [(set_attr "type" "alus_sreg,alus_imm,alus_imm")]
> + cmn\\t%<w>0, #%n1
> + cmp\\t%<w>0, %<w>1"
> + [(set_attr "type" "alus_imm,alus_imm,alus_sreg")]
> )
>
> (define_insn "fcmp<mode>"
...does adding 'Z' to operand 1 enable any new combinations?
I guess it allows (compare:CC (const_int 0) (const_int 0)),
but it's borderline whether that should be valid rtl.
Richard
next prev parent reply other threads:[~2020-03-31 16:55 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-21 2:42 [PATCH v2 0/9] aarch64: Implement TImode comparisons Richard Henderson
2020-03-21 2:42 ` [PATCH v2 1/9] aarch64: Accept 0 as first argument to compares Richard Henderson
2020-03-31 16:55 ` Richard Sandiford [this message]
2020-03-31 17:15 ` Richard Henderson
2020-03-21 2:42 ` [PATCH v2 2/9] aarch64: Accept zeros in add<GPI>3_carryin Richard Henderson
2020-03-21 2:42 ` [PATCH v2 3/9] aarch64: Add <su>cmp_*_carryinC patterns Richard Henderson
2020-03-22 19:30 ` Segher Boessenkool
2020-03-22 20:40 ` Richard Henderson
2020-03-31 18:34 ` Richard Sandiford
2020-03-31 22:44 ` Richard Henderson
2020-04-01 12:37 ` Segher Boessenkool
2020-04-01 16:28 ` Richard Sandiford
2020-04-01 17:14 ` Richard Henderson
2020-03-21 2:42 ` [PATCH v2 4/9] aarch64: Add <su>cmp<GPI>_carryinC_m2 Richard Henderson
2020-03-21 2:42 ` [PATCH v2 5/9] aarch64: Provide expander for sub<GPI>3_compare1 Richard Henderson
2020-03-21 2:42 ` [PATCH v2 6/9] aarch64: Introduce aarch64_expand_addsubti Richard Henderson
2020-03-21 2:42 ` [PATCH v2 7/9] aarch64: Adjust result of aarch64_gen_compare_reg Richard Henderson
2020-03-22 21:55 ` Segher Boessenkool
2020-03-22 22:21 ` Richard Henderson
2020-03-21 2:42 ` [PATCH v2 8/9] aarch64: Implement TImode comparisons Richard Henderson
2020-03-21 2:42 ` [PATCH v2 9/9] aarch64: Implement absti2 Richard Henderson
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