> Am 26.10.2023 um 14:21 schrieb Andrew Pinski <pins...@gmail.com>:
>
> On Thu, Oct 26, 2023 at 2:24 AM Richard Biener
> <richard.guent...@gmail.com> wrote:
>>
>>> On Wed, Oct 25, 2023 at 5:37 AM Andrew Pinski <pins...@gmail.com> wrote:
>>>
>>> This adds a match pattern for `a != C1 ? abs(a) : C2` which gets simplified
>>> to `abs(a)`. if C1 was originally *_MIN then change it over to use absu
>>> instead
>>> of abs.
>>>
>>> Bootstrapped and tested on x86_64-linux-gnu with no regressions.
>>>
>>> PR tree-optimization/111957
>>>
>>> gcc/ChangeLog:
>>>
>>> * match.pd (`a != C1 ? abs(a) : C2`): New pattern.
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> * gcc.dg/tree-ssa/phi-opt-40.c: New test.
>>> ---
>>> gcc/match.pd | 10 +++++++++
>>> gcc/testsuite/gcc.dg/tree-ssa/phi-opt-40.c | 25 ++++++++++++++++++++++
>>> 2 files changed, 35 insertions(+)
>>> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi-opt-40.c
>>>
>>> diff --git a/gcc/match.pd b/gcc/match.pd
>>> index 5df04ebba77..370ee35de52 100644
>>> --- a/gcc/match.pd
>>> +++ b/gcc/match.pd
>>> @@ -5622,6 +5622,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>>> (if (wi::eq_p (wi::bit_not (wi::to_wide (@1)), wi::to_wide (@2)))
>>> @3))
>>>
>>> +/* X != C1 ? abs(X) : C2 simplifies to abs(x) when abs(C1) == C2. */
>>> +(for op (abs absu)
>>> + (simplify
>>> + (cond (ne @0 INTEGER_CST@1) (op@3 @0) INTEGER_CST@2)
>>> + (if (wi::abs (wi::to_wide (@1)) == wi::to_wide (@2))
>>
>> Why not use
>>
>> (cond (ne @0 INTEGER_CST@1) (op@3 @0) @1)
>
> Because that does not work for:
> `a != -1 ? abs(a) : -1`
> We want to match -1 and 1 here (in that order).
> It just happens 0 and INT_MIN have the same value as their abs and
> matches but we could expand it to match all others too.
Ah, I missed the wi::not. The original patch is OK.
Richard
> Thanks,
> Andrew
>
>>
>> ? OK with that change.
>>
>> Richard.
>>
>>> + (if (op != ABSU_EXPR && wi::only_sign_bit_p (wi::to_wide (@1)))
>>> + (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); }
>>> + (convert (absu:utype @0)))
>>> + @3))))
>>> +
>>> /* (X + 1) > Y ? -X : 1 simplifies to X >= Y ? -X : 1 when
>>> X is unsigned, as when X + 1 overflows, X is -1, so -X == 1. */
>>> (simplify
>>> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-40.c
>>> b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-40.c
>>> new file mode 100644
>>> index 00000000000..a9011ce97fb
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-40.c
>>> @@ -0,0 +1,25 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O1 -fdump-tree-phiopt" } */
>>> +/* PR tree-optimization/111957 */
>>> +
>>> +int f(int a)
>>> +{
>>> + if (a)
>>> + return a > 0 ? a : -a;
>>> + return 0;
>>> +}
>>> +
>>> +int f1(int x)
>>> +{
>>> + int intmin = (-1u >> 1);
>>> + intmin = -intmin - 1;
>>> + if (x != intmin)
>>> + return x > 0 ? x : -x;
>>> + return intmin;
>>> +}
>>> +
>>> +/* { dg-final { scan-tree-dump-times "if " 1 "phiopt1" } } */
>>> +/* { dg-final { scan-tree-dump-not "if " "phiopt2" } } */
>>> +/* { dg-final { scan-tree-dump-times "ABS_EXPR <" 2 "phiopt1" } } */
>>> +/* { dg-final { scan-tree-dump-times "ABS_EXPR <" 1 "phiopt2" } } */
>>> +/* { dg-final { scan-tree-dump-times "ABSU_EXPR <" 1 "phiopt2" } } */
>>> --
>>> 2.34.1
>>>
