From: Cherry Vanc <cherry.vanc@gmail.com>
To: Jeff Law <law@redhat.com>
Cc: gcc-help@gcc.gnu.org
Subject: Re: fuse multiple ops into one new op
Date: Tue, 05 Aug 2014 23:26:00 -0000 [thread overview]
Message-ID: <CANqEaAfU20usuRLyKzEa5t5=5cUQWhef0dyPsHXu3B4Mvk9GSA@mail.gmail.com> (raw)
In-Reply-To: <53DCB4BF.80701@redhat.com>
Thanks. I am now using a define_insn based on your inputs :
(define_insn "testnew36"
[(set (match_operand:DI 0 "register_operand" "")
(op1:DI (match_operand:DI 1 "register_operand" "")
(match_operand:SI 2 "immediate_operand" "") ))
(set (match_operand:DI 3 "register_operand" "")
(op2:DI (match_operand:DI 4 "register_operand" "") (match_dup 0)))
(set (match_operand:DI 5 "register_operand" "")
(sign_extend:DI (op3:SI (match_dup 3))))]
"TARGET_MYCORE"
"testnew 36"
[(set_attr "mode" "DI")])
Why doesnt -fdump-rtl-all-all / -fdump-rtl-all generate those .life
and .combine files so that I can take a look at the combine pass is
doing ? dump-rtl-combine doesnt spit anything either. MYCORE is a mips
adaptation using GCC 4.9.0.
On Sat, Aug 2, 2014 at 2:51 AM, Jeff Law <law@redhat.com> wrote:
> On 08/01/14 17:18, Cherry Vanc wrote:
>>
>> I need to fuse multiple instructions into a single one.
>> ...
>> r1 = (r1) op1 (const)
>> ...
>> ...
>> r1 = (r1) op2 (r2)
>> ...
>> ...
>> r3 = op3 (r1)
>> ...
>>
>> I defined a peephole2 pattern in my GCC backend .md file. If these
>> three instructions are contiguous, then I do get my test "testnew"
>> instruction. If these instructions are far apart, I dont.
>>
>> (define_peephole2
>> [(set (match_operand:DI 0 "register_operand" "")
>> (op1:DI (match_dup 0) (match_operand:SI 1 "immediate_operand" "") ))
>> (set (match_dup 0)
>> (op2:DI (match_operand:DI 2 "register_operand" "") (match_dup 0)))
>> (set (match_dup 0)
>> (sign_extend:DI (op3:SI (match_dup 0))))]
>> "TARGET_MYCORE"
>> [(set (match_dup 0) (sign_extend:DI (op3:SI (op2:SI (op1:SI
>> (match_dup 0) (match_dup 1)) (match_dup 0)))))]
>> "")
>>
>> (define_insn "*testnew"
>> [(set (match_operand:DI 0 "register_operand" "=d")
>> (sign_extend:DI (op3:SI (op2:SI (op1:SI (match_dup 0)
>> (match_operand:SI 1 "immediate_operand" "I")) (match_dup 0)))))]
>> "TARGET_MYCORE"
>> "testnew 36"
>> [(set_attr "mode" "DI")])
>>
>> How can I fuse multiple instructions that are far apart into a new
>> single opcode that MYCORE has ?
>
> I suspect the problem is "r1" is set/used multiple times. That will inhibit
> instruction combination. If at all possible you really want that code to
> look like:
>
>
> r4 = (r1) op1 (const) /* r1 dies */
> r5 = r4 op (r2) /*r2 and r2 die */
> r3 = op3 (r5) /* r5 dies */
>
>
> Then the combiner will attempt to combine those instructions in the obvious
> ways. For the combiner you want to use a define_insn pattern.
>
> define_peephole2 is primarily used in cases where there is no obvious
> dataflow between the patterns.
>
>
> Jeff
>
>
next prev parent reply other threads:[~2014-08-05 23:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-01 23:18 Cherry Vanc
2014-08-02 7:02 ` Marc Glisse
2014-08-02 9:09 ` Oleg Endo
2014-08-02 9:52 ` Jeff Law
2014-08-05 23:26 ` Cherry Vanc [this message]
2014-08-05 23:27 ` Cherry Vanc
2014-08-06 5:51 ` Marc Glisse
2014-08-07 18:35 ` Cherry Vanc
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