On 2023-11-23 14:34 Andrew Pinski<pins...@gmail.com> wrote:
>
>On Wed, Nov 22, 2023 at 10:07 PM Feng Wang <wangf...@eswincomputing.com> wrote:
>>
>> 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 "-march=rv64gc_zba_zbb -mabi=lp64d -O2",
>> before this patch the compilation result is
>> foo1:
>> andi a0,a0,15
>> slliw a5,a0,4
>> addw a3,a5,a0
>> li a4,33
>> add a0,a5,a0
>> bleu a3,a4,.L5
>> ret
>> .L5:
>> li a0,34
>> ret
>> after this patch the compilation result is
>> foo1:
>> andi a0,a0,15
>> slliw a5,a0,4
>> add a5,a5,a0
>> li a0,34
>> max a0,a5,a0
>> ret
>> The reason is in the pass_early_vrp, the arg0 of gimple_cond
>> is replaced,but the PHI node still use the arg0.
>> The some of evrp pass logs are as follows
>> gimple_assign <mult_expr, _9, _7, 17, NULL>
>> gimple_assign <nop_expr, res_5, _9, NULL, NULL>
>> gimple_cond <le_expr, _9, 33, NULL, NULL>
>> goto <bb 3>; [INV]
>> else
>> goto <bb 4>; [INV]
>>
>> <bb 3> :
>> // predicted unlikely by early return (on trees) predictor.
>>
>> <bb 4> :
>> # gimple_phi <_2, 34(3), res_5(2)>
>> The arg0 of gimple_cond is replaced by _9,but the gimple_phi still
>> uses res_5,it will cause optimization fail of PHI node to MAX_EXPR.
>> So the next_use_is_phi is added to control the replacement.
>
>I don't think this is the correct appoarch here.
>We end up with the same original issue if we had wrote it like:
>```
>int foo1 (int data, int res)
>{
> res = data & 0xf;
> unsigned int r = res;
> r*=17;
> res = r;
> if (r < 0x22)
> return 0x22;
> return res;
>}
>```
>I suspect instead we should extend the match.pd patterns to match this max.
>We should be able to extend:
>```
>(for cmp (lt le gt ge eq ne)
> (simplify
> (cond (cmp (convert1? @1) INTEGER_CST@3) (convert2? @1) INTEGER_CST@2)
> (with
>```
>To match instead by changing the second @1 with @4 and then using
>bitwise_equal_p . If @1 != @4 but bitwise_equal_p is true, you need to
>make sure the outer convert1/convert2 are nop conversions so that you
>get the same extension I think ...
>
>Note you could instead improve minmax_replacement but I have been in
>the process of moving those changes to match.pd.
>
>Thanks,
>Andrew Pinski
Thanks for your feedback. The minmax replacement happens in phiopt pass, there
is one condition
that requires the "arg_false"(from PHI node) should be same with "smaller"(from
gimple_cond).
So I made this change. But as you said, this modification is not very suitable,
and I have not considered
it comprehensively. I'm not very familiar with match.pd, can it solve this
judgment problem?
Thanks,
Feng Wang
>
>>
>> gcc/ChangeLog:
>>
>> * vr-values.cc (next_use_is_phi):
>> (simplify_using_ranges::simplify_casted_compare):
>> add new function next_use_is_phi to control the replacement.
>>
>> gcc/testsuite/ChangeLog:
>>
>> * gcc.target/riscv/zbb-min-max-04.c: New test.
>> ---
>> gcc/testsuite/gcc.target/riscv/zbb-min-max-04.c | 14 ++++++++++++++
>> gcc/vr-values.cc | 15 ++++++++++++++-
>> 2 files changed, 28 insertions(+), 1 deletion(-)
>> create mode 100644 gcc/testsuite/gcc.target/riscv/zbb-min-max-04.c
>>
>> diff --git a/gcc/testsuite/gcc.target/riscv/zbb-min-max-04.c
>> b/gcc/testsuite/gcc.target/riscv/zbb-min-max-04.c
>> new file mode 100644
>> index 00000000000..8c3e87a35e0
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/riscv/zbb-min-max-04.c
>> @@ -0,0 +1,14 @@
>> +/* { dg-do compile } */
>> +/* { dg-options "-march=rv64gc_zba_zbb -mabi=lp64d" } */
>> +/* { dg-skip-if "" { *-*-* } { "-O0" "-Og" } } */
>> +
>> +int foo1 (int data, int res)
>> +{
>> + res = data & 0xf;
>> + res |= res << 4;
>> + if (res < 0x22)
>> + return 0x22;
>> + return res;
>> +}
>> +
>> +/* { dg-final { scan-assembler-times "max\t" 1 } } */
>> \ No newline at end of file
>> diff --git a/gcc/vr-values.cc b/gcc/vr-values.cc
>> index ecb294131b0..1f7a727c638 100644
>> --- a/gcc/vr-values.cc
>> +++ b/gcc/vr-values.cc
>> @@ -1263,6 +1263,18 @@
>> simplify_using_ranges::simplify_compare_using_ranges_1 (tree_code
>> &cond_code, tr
>> return happened;
>> }
>>
>> +/* Return true if the next use of SSA_NAME is PHI node */
>> +bool
>> +next_use_is_phi (tree arg)
>> +{
>> + use_operand_p imm = &(SSA_NAME_IMM_USE_NODE (arg));
>> + use_operand_p next = imm->next;
>> + if (next && next->loc.stmt
>> + && (gimple_code (next->loc.stmt) == GIMPLE_PHI))
>> + return true;
>> + return false;
>> +}
>> +
>> /* Simplify OP0 code OP1 when OP1 is a constant and OP0 was a SSA_NAME
>> defined by a type conversion. Replacing OP0 with RHS of the type
>>conversion.
>> Doing so makes the conversion dead which helps subsequent passes. */
>> @@ -1305,7 +1317,8 @@ simplify_using_ranges::simplify_casted_compare
>> (tree_code &, tree &op0, tree &op
>> if (TREE_CODE (innerop) == SSA_NAME
>> && !POINTER_TYPE_P (TREE_TYPE (innerop))
>> && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (innerop)
>> - && desired_pro_or_demotion_p (TREE_TYPE (innerop), TREE_TYPE
>> (op0)))
>> + && desired_pro_or_demotion_p (TREE_TYPE (innerop), TREE_TYPE (op0))
>> + && !next_use_is_phi (op0))
>> {
>> value_range vr;
>>
>> --
>> 2.17.1
>>
