On 2023-11-28 11:06 Andrew Pinski <pins...@gmail.com> wrote:
>On Mon, Nov 27, 2023 at 6:56 PM Feng Wang <wangf...@eswincomputing.com> wrote:
>>
>> The link of PATCH v1:
>> https://www.mail-archive.com/gcc-patches@gcc.gnu.org/msg326661.html
>> This patch add another condition for gimple-cond optimization. Refer to
>> the following test case.
>> int foo1 (int data, int res)
>> {
>> res = data & 0xf;
>> res |= res << 4;
>> if (res < 0x22)
>> return 0x22;
>> return res;
>> }
>> with the compilation flag "-O2",
>> before this patch the log info of phiopt2 pass is
>> <bb 2> [local count: 1073741824]:
>> res_5 = data_1(D) & 15;
>> _6 = (unsigned int) res_5;
>> _7 = _6 * 17;
>> res_8 = (int) _7;
>> if (_7 <= 33)
>> goto <bb 3>; [21.72%]
>> else
>> goto <bb 4>; [78.28%]
>>
>> <bb 3> [local count: 233216728]:
>>
>> <bb 4> [local count: 1073741824]:
>> # _9 = PHI <res_8(2), 34(3)>
>> return _9;
>> after this patch the the log info of phiopt2 pass is
>> <bb 2> [local count: 1073741824]:
>> res_5 = data_1(D) & 15;
>> _6 = (unsigned int) res_5;
>> _7 = _6 * 17;
>> res_8 = (int) _7;
>> _10 = MAX_EXPR <_7, 34>;
>> _3 = (int) _10;
>> return _3;
>> This patch optimizes the phi node to generate "MAX_EXPR".
>> The root cause of minmax replacement failure is the type of "_7"
>> is unsigned, but the type of const_int "34" is signed. It makes
>> types_match (c2_type, from_type) return false. So I add another
>> condition to process this scenario.
>>
>> gcc/ChangeLog:
>>
>> * match.pd: Add another condition to process type mismatch.
>
>This should most likely be:
> ((cond (cmp (convert1? x) c1) (convert2? x) c2) pattern): Also allow
>conversions that only change the sign.
>
>>
>> gcc/testsuite/ChangeLog:
>>
>> * gcc.dg/tree-ssa/phi-opt-41.c: New test.
>> ---
>> gcc/match.pd | 5 ++++-
>> gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c | 24 ++++++++++++++++++++++
>> 2 files changed, 28 insertions(+), 1 deletion(-)
>> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c
>>
>> diff --git a/gcc/match.pd b/gcc/match.pd
>> index 95225e4ca5f..e864845bfa9 100644
>> --- a/gcc/match.pd
>> +++ b/gcc/match.pd
>> @@ -5419,7 +5419,10 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>> && (types_match (c2_type, from_type)
>> || (TYPE_PRECISION (c2_type) > TYPE_PRECISION (from_type)
>> && (TYPE_UNSIGNED (from_type)
>> - || TYPE_SIGN (c2_type) == TYPE_SIGN (from_type)))))
>> + || TYPE_SIGN (c2_type) == TYPE_SIGN (from_type)))
>> + || (TYPE_UNSIGNED (from_type) != TYPE_UNSIGNED (c2_type)
>> + && TYPE_PRECISION (c2_type) == TYPE_PRECISION (from_type)
>> + && !TYPE_OVERFLOW_WRAPS (c2_type))))
>
>What is the need for TYPE_OVERFLOW_WRAPS here? Also I think you just
>need the check for TYPE_PRECISION instead of the rest.
>Maybe instead of types_match here, tree_nop_conversion_p could be used
>instead. I am not 100% sure though.
>
>I also suspect you should add a few other testcases that don't depend
>on VRP changing things. Maybe a runtime test too.
>
>Thanks,
>Andrew
>
I want to make sure the cont_int "c2" won't be overflow,so I use the
TYPE_OVERFLOW_WRAPS.
I checked the code , tree_nop_conversion_p judge the TYPE_PRECISION or
TYPE_MODE and doesn't
care the unsigned_flag, it should be fine for this scenario, I'm not sure if
there's a problem with this
modification, I will run the regression to check whether it causes other
issues.
Thanks,
Feng Wang
>> {
>> if (cmp != EQ_EXPR)
>> code = minmax_from_comparison (cmp, @1, @3, @1, @2);
>> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c
>> b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c
>> new file mode 100644
>> index 00000000000..d1101c2f9f7
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c
>> @@ -0,0 +1,24 @@
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2 -fdump-tree-phiopt2" } */
>> +
>> +int foo1 (int data, int res)
>> +{
>> + res = data & 0xf;
>> + res |= res << 4;
>> + if (res < 0x22)
>> + return 0x22;
>> + return res;
>> +}
>> +
>> +int foo2 (int data, int res)
>> +{
>> + res = data & 0xf;
>> + unsigned int r = res;
>> + r*=17;
>> + res = r;
>> + if (r < 0x22)
>> + return 0x22;
>> + return res;
>> +}
>> +
>> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 2 "phiopt2" } } */
>> \ No newline at end of file
>> --
>> 2.17.1
>>
