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[70.176.202.128]) by smtp.googlemail.com with ESMTPSA id x88sm57893007pfi.66.2016.03.02.23.24.00 (version=TLSv1/SSLv3 cipher=OTHER); Wed, 02 Mar 2016 23:24:01 -0800 (PST) Subject: Re: [PATCH][ARM] PR target/70008 To: "Richard Earnshaw (lists)" , Kyrill Tkachov , GCC Patches , Ramana Radhakrishnan References: <56D3CD4F.6060301@linaro.org> <56D4263A.5040403@foss.arm.com> <56D429CA.9000202@linaro.org> <56D463E7.1040105@arm.com> From: Michael Collison Message-ID: <56D7E68F.4020500@linaro.org> Date: Thu, 3 Mar 2016 00:23:59 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <56D463E7.1040105@arm.com> I have attached a new patch which hopefully address Richard's concerns. I modified the predicate on operand 1 to to "arm_rhs_operand" to be consistent with the constraints. I retained the split into two patterns; one for arm and another for thumb2. I thought this was cleaner. Okay for trunk? 2016-02-28 Michael Collison PR target/70008 * config/arm/arm.md (*subsi3_carryin): Change predicate to arm_rhs_operand to be consistent with constraints. Only allow pattern for TARGET_ARM. * config/arm/thumb2.md (*thumb2_subsi3_carryin): New pattern. On 02/29/2016 08:29 AM, Richard Earnshaw (lists) wrote: > On 29/02/16 11:21, Michael Collison wrote: >> >> On 2/29/2016 4:06 AM, Kyrill Tkachov wrote: >>> Hi Michael, >>> >>> On 29/02/16 04:47, Michael Collison wrote: >>>> This patches address PR 70008, where a reverse subtract with carry >>>> instruction can be generated in thumb2 mode. It was tested with no >>>> regressions in arm and thumb modes on the following targets: >>>> >>>> arm-none-linux-gnueabi >>>> arm-none-linux-gnuabihf >>>> armeb-none-linux-gnuabihf >>>> arm-none-eabi >>>> >>>> Okay for trunk? >>>> >>>> 2016-02-28 Michael Collison >>>> >>>> PR target/70008 >>>> * config/arm/arm.md (*subsi3_carryin): Only match pattern if >>>> TARGET_ARM due to 'rsc' instruction alternative. >>>> * config/arm/thumb2.md (*thumb2_subsi3_carryin): New pattern. >>>> >>>> >>> The *subsi3_carrying pattern has the arch attribute: >>> (set_attr "arch" "*,a") >>> >>> That means that the second alternative that generates the RSC >>> instruction is only enabled >>> for ARM mode. Do you have a testcase where this doesn't happen and >>> this pattern generates >>> the second alternative for Thumb2? >> No I don't have a test case; i noticed the pattern when working on the >> overflow project. I did not realize >> that an attribute could affect the matching of an alternative. I will >> close the bug. >> >>> >>> Thanks, >>> Kyrill > This is all true, but there is a potential performance issue with this > pattern though, that could lead to sub-optimal code. > > The predicate accepts reg-or-int, but in ARM state only simple > 'const-ok-for-arm' immediates are permitted by the predicates, and in > thumb code, no immediates are permitted at all. This could potentially > result in sub-optimal code due to late splitting of the pattern. It > would be better if the predicate understood these limitations and > restricted immediates accordingly. > > R. > diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md index e67239d..e6bcd7f 100644 --- a/gcc/config/arm/arm.md +++ b/gcc/config/arm/arm.md @@ -867,15 +867,14 @@ (define_insn "*subsi3_carryin" [(set (match_operand:SI 0 "s_register_operand" "=r,r") - (minus:SI (minus:SI (match_operand:SI 1 "reg_or_int_operand" "r,I") + (minus:SI (minus:SI (match_operand:SI 1 "arm_rhs_operand" "r,I") (match_operand:SI 2 "s_register_operand" "r,r")) (ltu:SI (reg:CC_C CC_REGNUM) (const_int 0))))] - "TARGET_32BIT" + "TARGET_ARM" "@ sbc%?\\t%0, %1, %2 rsc%?\\t%0, %2, %1" [(set_attr "conds" "use") - (set_attr "arch" "*,a") (set_attr "predicable" "yes") (set_attr "predicable_short_it" "no") (set_attr "type" "adc_reg,adc_imm")] diff --git a/gcc/config/arm/thumb2.md b/gcc/config/arm/thumb2.md index 9925365..79305c5 100644 --- a/gcc/config/arm/thumb2.md +++ b/gcc/config/arm/thumb2.md @@ -848,6 +848,20 @@ (set_attr "type" "multiple")] ) +(define_insn "*thumb2_subsi3_carryin" + [(set (match_operand:SI 0 "s_register_operand" "=r") + (minus:SI (minus:SI (match_operand:SI 1 "s_register_operand" "r") + (match_operand:SI 2 "s_register_operand" "r")) + (ltu:SI (reg:CC_C CC_REGNUM) (const_int 0))))] + "TARGET_THUMB2" + "@ + sbc%?\\t%0, %1, %2" + [(set_attr "conds" "use") + (set_attr "predicable" "yes") + (set_attr "predicable_short_it" "no") + (set_attr "type" "adc_reg")] +) + (define_insn "*thumb2_cond_sub" [(set (match_operand:SI 0 "s_register_operand" "=Ts,Ts") (minus:SI (match_operand:SI 1 "s_register_operand" "0,?Ts") -- 1.9.1