From: Michael Collison <collison@rivosinc.com>
To: Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org>
Cc: gcc-patches@gcc.gnu.org, Richard Biener <richard.guenther@gmail.com>
Subject: Re: [PATCH v2] match.pd: rewrite select to branchless expression
Date: Fri, 11 Nov 2022 08:00:05 -0500 [thread overview]
Message-ID: <e105a302-1725-7752-7e3e-7bb03ae9c227@rivosinc.com> (raw)
In-Reply-To: <CAAgBjMm74-RQbScrXY-A8kx6qkC6vDATorEueitGGzoOgG5Q-g@mail.gmail.com>
Hi Prathamesh,
It is my understanding that INTEGRAL_TYPE_P applies to the other integer
types you mentioned (chart, short, long). In fact the test function that
motivated this match has a mixture of char and short and does not
restrict matching.
On 11/11/22 02:44, Prathamesh Kulkarni wrote:
> On Fri, 11 Nov 2022 at 07:58, Michael Collison <collison@rivosinc.com> wrote:
>> This patches transforms ((x & 0x1) == 0) ? y : z <op> y -into
>> (-(typeof(y))(x & 0x1) & z) <op> y, where op is a '^' or a '|'. It also
>> transforms (cond (and (x , 0x1) != 0), (z op y), y ) into (-(and (x ,
>> 0x1)) & z ) op y.
>>
>> Matching this patterns allows GCC to generate branchless code for one of
>> the functions in coremark.
>>
>> Bootstrapped and tested on x86 and RISC-V. Okay?
>>
>> Michael.
>>
>> 2022-11-10 Michael Collison <collison@rivosinc.com>
>>
>> * match.pd ((x & 0x1) == 0) ? y : z <op> y
>> -> (-(typeof(y))(x & 0x1) & z) <op> y.
>>
>> 2022-11-10 Michael Collison <collison@rivosinc.com>
>>
>> * gcc.dg/tree-ssa/branchless-cond.c: New test.
>>
>> ---
>>
>> Changes in v2:
>>
>> - Rewrite comment to use C syntax
>>
>> - Guard against 1-bit types
>>
>> - Simplify pattern by using zero_one_valued_p
>>
>> gcc/match.pd | 24 +++++++++++++++++
>> .../gcc.dg/tree-ssa/branchless-cond.c | 26 +++++++++++++++++++
>> 2 files changed, 50 insertions(+)
>> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/branchless-cond.c
>>
>> diff --git a/gcc/match.pd b/gcc/match.pd
>> index 194ba8f5188..258531e9046 100644
>> --- a/gcc/match.pd
>> +++ b/gcc/match.pd
>> @@ -3486,6 +3486,30 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>> (cond (le @0 integer_zerop@1) (negate@2 @0) integer_zerop@1)
>> (max @2 @1))
>>
>> +/* ((x & 0x1) == 0) ? y : z <op> y -> (-(typeof(y))(x & 0x1) & z) <op> y */
>> +(for op (bit_xor bit_ior)
>> + (simplify
>> + (cond (eq zero_one_valued_p@0
>> + integer_zerop)
>> + @1
>> + (op:c @2 @1))
>> + (if (INTEGRAL_TYPE_P (type)
>> + && TYPE_PRECISION (type) > 1
>> + && (INTEGRAL_TYPE_P (TREE_TYPE (@0))))
>> + (op (bit_and (negate (convert:type @0)) @2) @1))))
>> +
>> +/* ((x & 0x1) == 0) ? z <op> y : y -> (-(typeof(y))(x & 0x1) & z) <op> y */
>> +(for op (bit_xor bit_ior)
>> + (simplify
>> + (cond (ne zero_one_valued_p@0
>> + integer_zerop)
>> + (op:c @2 @1)
>> + @1)
>> + (if (INTEGRAL_TYPE_P (type)
>> + && TYPE_PRECISION (type) > 1
>> + && (INTEGRAL_TYPE_P (TREE_TYPE (@0))))
>> + (op (bit_and (negate (convert:type @0)) @2) @1))))
>> +
>> /* Simplifications of shift and rotates. */
>>
>> (for rotate (lrotate rrotate)
>> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/branchless-cond.c b/gcc/testsuite/gcc.dg/tree-ssa/branchless-cond.c
>> new file mode 100644
>> index 00000000000..68087ae6568
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/tree-ssa/branchless-cond.c
>> @@ -0,0 +1,26 @@
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2 -fdump-tree-optimized" } */
>> +
>> +int f1(unsigned int x, unsigned int y, unsigned int z)
>> +{
>> + return ((x & 1) == 0) ? y : z ^ y;
>> +}
>> +
>> +int f2(unsigned int x, unsigned int y, unsigned int z)
>> +{
>> + return ((x & 1) != 0) ? z ^ y : y;
>> +}
>> +
>> +int f3(unsigned int x, unsigned int y, unsigned int z)
>> +{
>> + return ((x & 1) == 0) ? y : z | y;
>> +}
>> +
>> +int f4(unsigned int x, unsigned int y, unsigned int z)
>> +{
>> + return ((x & 1) != 0) ? z | y : y;
>> +}
> Sorry to nitpick -- Since the pattern gates on INTEGRAL_TYPE_P, would
> it be a good idea
> to have these tests for other integral types too besides int like
> {char, short, long} ?
>
> Thanks,
> Prathamesh
>> +
>> +/* { dg-final { scan-tree-dump-times " -" 4 "optimized" } } */
>> +/* { dg-final { scan-tree-dump-times " & " 8 "optimized" } } */
>> +/* { dg-final { scan-tree-dump-not "if" "optimized" } } */
>> --
>> 2.34.1
>>
next prev parent reply other threads:[~2022-11-11 13:00 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-11 2:28 Michael Collison
2022-11-11 7:44 ` Prathamesh Kulkarni
2022-11-11 13:00 ` Michael Collison [this message]
2022-11-17 14:34 ` Jeff Law
2022-11-18 12:57 ` Richard Biener
2022-12-01 18:57 ` Michael Collison
2022-12-02 8:22 ` Richard Biener
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