Fix for 56175
Yuri Rumyantsev
ysrumyan@gmail.com
Thu Feb 21 15:42:00 GMT 2013
Richard,
This does not fit to my fix since if we have another pattern like
t = (u8)((x & 1) ^ ((u8)y & 1));
where y has short type, for rhs operand type sinkning (or hoisting as
you prefer) still will be performed but I don't see any reason for
converting (u8)y & 1 --> (u8)(y & 1) if y has u16 type for all
targets including x86.
Yuri.
2013/2/21 Richard Biener <richard.guenther@gmail.com>:
> On Thu, Feb 21, 2013 at 4:16 PM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
>> Richard,
>>
>> Sorry for my previous message - I did not undersatnd it properly.
>>
>> Anyway I proposed another fix that avoid (type) x & c --> (type) (x &
>> (type-x) c) transformation if x has short type:
>>
>> +++ gcc/tree-ssa-forwprop.c (working copy)
>> @@ -1789,8 +1789,11 @@
>> defcodefor_name (arg1, &def1_code, &def1_arg1, &def1_arg2);
>> defcodefor_name (arg2, &def2_code, &def2_arg1, &def2_arg2);
>>
>> - /* Try to fold (type) X op CST -> (type) (X op ((type-x) CST)). */
>> + /* Try to fold (type) X op CST -> (type) (X op ((type-x) CST)).
>> + Do that only if X has not short type. */
>> if (TREE_CODE (arg2) == INTEGER_CST
>> + && (TYPE_PRECISION (TREE_TYPE (arg1))
>> + >= TYPE_PRECISION (integer_type_node))
>> && CONVERT_EXPR_CODE_P (def1_code)
>> && INTEGRAL_TYPE_P (TREE_TYPE (def1_arg1))
>> && int_fits_type_p (arg2, TREE_TYPE (def1_arg1)))
>>
>> Does this fix look suitable?
>
> I think the fix is to disable the transform if it widens the operation.
> Thus, sth like
>
> if (TREE_CODE (arg2) == INTEGER_CST
> && CONVERT_EXPR_CODE_P (def1_code)
> && INTEGRAL_TYPE_P (TREE_TYPE (def1_arg1))
> + && (TYPE_PRECISION (TREE_TYPE (arg1))
> + >= TYPE_PRECISION (TREE_TYPE (def1_arg1)))
> && int_fits_type_p (arg2, TREE_TYPE (def1_arg1)))
>
> see the restriction we place on the transform for the (T1) x & (T2) y case:
>
> /* For bitwise binary operations apply operand conversions to the
> binary operation result instead of to the operands. This allows
> to combine successive conversions and bitwise binary operations. */
> if (CONVERT_EXPR_CODE_P (def1_code)
> && CONVERT_EXPR_CODE_P (def2_code)
> && types_compatible_p (TREE_TYPE (def1_arg1), TREE_TYPE (def2_arg1))
> /* Make sure that the conversion widens the operands, or has same
> precision, or that it changes the operation to a bitfield
> precision. */
> && ((TYPE_PRECISION (TREE_TYPE (def1_arg1))
> <= TYPE_PRECISION (TREE_TYPE (arg1)))
> || (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (arg1)))
> != MODE_INT)
> || (TYPE_PRECISION (TREE_TYPE (arg1))
> != GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (arg1))))))
>
> ideally you'd split out that condition into a predicate function taking the
> two type and use it in both places.
>
> Richard.
>
>> Yuri.
>>
>> 2013/2/21 Richard Biener <richard.guenther@gmail.com>:
>>> On Thu, Feb 21, 2013 at 3:26 PM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
>>>> Richard,
>>>>
>>>> I double checked that with and without my fix compiler produces the
>>>> same output with -fdump-tree-optimized.
>>>
>>> For what testcase?
>>>
>>> Richard.
>>>
>>>> What patch did you apply? I think that you should apply the second one
>>>> - 56175.diff.
>>>>
>>>> Yuri.
>>>>
>>>> 2013/2/21 Richard Biener <richard.guenther@gmail.com>:
>>>>> On Thu, Feb 21, 2013 at 2:41 PM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
>>>>>> Richard,
>>>>>>
>>>>>> This regression was introduced by Kai
>>>>>>
>>>>>> http://gcc.gnu.org/ml/gcc-patches/2011-06/msg01988.html
>>>>>>
>>>>>> 2011-06-27 Kai Tietz <ktietz@redhat.com>
>>>>>>
>>>>>> * tree-ssa-forwprop.c (simplify_bitwise_binary): Improve
>>>>>> type sinking.
>>>>>> * tree-ssa-math-opts.c (execute_optimize_bswap): Separate
>>>>>> search for di/si mode patterns for finding widest match.
>>>>>>
>>>>>> Is it sufficient for you to accept my patch?
>>>>>
>>>>> No, I still don't think the fix is sound. A proper fix would revert the
>>>>> above change (the simplify_bitwise_binary one), watch for testsuite
>>>>> fallout (I can immediately see gcc.dg/tree-ssa/bitwise-sink.c failing)
>>>>> and fix those failures in a better way.
>>>>>
>>>>> Richard.
>>>>>
>>>>>> Best regards.
>>>>>> yuri.
>>>>>>
>>>>>> 2013/2/21 Richard Biener <richard.guenther@gmail.com>:
>>>>>>> On Thu, Feb 21, 2013 at 1:39 PM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
>>>>>>>> Richard,
>>>>>>>>
>>>>>>>> As we know Kai is working on this problem for 4.9 and I assume that
>>>>>>>> type sinking will be deleted from forwprop pass. Could we stay on this
>>>>>>>> fix but more common fix will be done.
>>>>>>>
>>>>>>> Well, unless you show it is a regression the patch is not applicable for 4.8
>>>>>>> anyway. Not sure if the code will be deleted from forwprop pass in 4.9 either,
>>>>>>> it is after all a canonicalization - fold seems to perform the opposite one
>>>>>>> though:
>>>>>>>
>>>>>>> /* Convert (T)(x & c) into (T)x & (T)c, if c is an integer
>>>>>>> constants (if x has signed type, the sign bit cannot be set
>>>>>>> in c). This folds extension into the BIT_AND_EXPR.
>>>>>>>
>>>>>>> note that what forwprop does (T)x & c -> (T)(x & c') I'd call type hoisting,
>>>>>>> not sinking. Generally frontends and fold try to narrow operands when
>>>>>>> possible (even though some targets later widen them again because of
>>>>>>> instruction set constraints).
>>>>>>>
>>>>>>> Most of this hoisting code was done to make lowering logical && and ||
>>>>>>> I believe. Looking at the testcases added tells us that while matching
>>>>>>> the two patterns as done now helps them but only because that pattern
>>>>>>> feeds single-operand instructions that then simplify. So doing the transform
>>>>>>> starting from that single-operand instructions instead looks like a better
>>>>>>> fix (op !=/== 0/1 and (T) op) and also would not disagree with the
>>>>>>> canonicalization done by fold.
>>>>>>>
>>>>>>> Richard.
>>>>>>>
>>>>>>>> I also can propose to introduce new hook for it but need to know your
>>>>>>>> opinion since we don't went to waste our time on preparing dead
>>>>>>>> patches. Note that x86 supports all short types in HW and such type
>>>>>>>> sinkning is usually useless if short types are involved.
>>>>>>>>
>>>>>>>> Best regards.
>>>>>>>> Yuri.
>>>>>>>>
>>>>>>>>
>>>>>>>> 2013/2/21 Richard Biener <richard.guenther@gmail.com>:
>>>>>>>>> On Wed, Feb 20, 2013 at 4:41 PM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
>>>>>>>>>> Richard,
>>>>>>>>>>
>>>>>>>>>> First of all, your proposal to move type sinking to the end of
>>>>>>>>>> function does not work since we handle each statement in function and
>>>>>>>>>> we want that 1st type folding of X & C will not happen.
>>>>>>>>>> Note that we have the following sequence of gimple before forwprop1:
>>>>>>>>>>
>>>>>>>>>> x.0_10 = (signed char) x_8;
>>>>>>>>>> _11 = x.0_10 & 1;
>>>>>>>>>> _12 = (signed char) y_9;
>>>>>>>>>> _13 = _12 & 1;
>>>>>>>>>> _14 = _11 ^ _13;
>>>>>>>>>
>>>>>>>>> Ah, indeed. Reminds me of some of my dead patches that separated
>>>>>>>>> forwprop into a forward and backward stage. Of course then you have
>>>>>>>>> the ordering issue of whether to first forward or backward.
>>>>>>>>>
>>>>>>>>> Which means that I bet you can construct a testcase that with
>>>>>>>>> your change is no longer optimized (just make pushing the conversion
>>>>>>>>> make the types _match_). Which is always the case
>>>>>>>>> with this kind of local pattern-matching transforms.
>>>>>>>>>
>>>>>>>>> Currently forwprop processes leafs of expression trees first (well, inside
>>>>>>>>> a basic-block), similar to how fold () is supposed to be operated, based
>>>>>>>>> on the idea that simplified / canonicalized leafs helps keeping pattern
>>>>>>>>> recognition simple and cost considerations more accurate.
>>>>>>>>>
>>>>>>>>> When one order works better than another you always have to consider
>>>>>>>>> that the user could already have written the code in a way that results
>>>>>>>>> in the input that isn't well handled.
>>>>>>>>>
>>>>>>>>> Not that this helps very much for the situation ;)
>>>>>>>>>
>>>>>>>>> But I don't like the use of first_pass_instance ... and the fix isn't
>>>>>>>>> an improvement but just a hack for the benchmark.
>>>>>>>>>
>>>>>>>>> Richard.
>>>>>>>>>
>>>>>>>>>> I also added comment to my fix and create new test for it. I also
>>>>>>>>>> checked that this test is passed with patched compiler only. So
>>>>>>>>>> Change Log was also modified:
>>>>>>>>>>
>>>>>>>>>> ChangeLog
>>>>>>>>>>
>>>>>>>>>> 2013-02-20 Yuri Rumyantsev <ysrumyan@gmail.com>
>>>>>>>>>>
>>>>>>>>>> PR tree-optimization/56175
>>>>>>>>>> * tree-ssa-forwprop.c (simplify_bitwise_binary): Avoid type sinking
>>>>>>>>>> at 1st forwprop pass to recognize (A & C) ^ (B & C) -> (A ^ B) & C
>>>>>>>>>> for short integer types.
>>>>>>>>>> * gcc.dg/pr56175.c: New test.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> 2013/2/20 Richard Biener <richard.guenther@gmail.com>:
>>>>>>>>>>> On Wed, Feb 20, 2013 at 1:00 PM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
>>>>>>>>>>>> Hi All,
>>>>>>>>>>>>
>>>>>>>>>>>> This patch is aimed to recognize (A & C) ^ (B & C) -> (A ^ B) & C
>>>>>>>>>>>> pattern in simpify_bitwise_binary for short integer types.
>>>>>>>>>>>> The fix is very simple - we simply turn off short type sinking at the
>>>>>>>>>>>> first pass of forward propagation allows to get
>>>>>>>>>>>> +10% speedup for important benchmark Coremark 1.0 at x86 Atom and
>>>>>>>>>>>> +5-7% for other x86 platforms too.
>>>>>>>>>>>> Bootstrapping and regression testing were successful on x86-64.
>>>>>>>>>>>>
>>>>>>>>>>>> Is it Ok for trunk?
>>>>>>>>>>>
>>>>>>>>>>> It definitely needs a comment before the checks.
>>>>>>>>>>>
>>>>>>>>>>> Also I think it simply shows that the code is placed at the wrong spot.
>>>>>>>>>>> Simply moving it down in simplify_bitwise_binary to be done the very last
>>>>>>>>>>> should get both of the effects done.
>>>>>>>>>>>
>>>>>>>>>>> Can you rework the patch according to that?
>>>>>>>>>>>
>>>>>>>>>>> You also miss a testcase, we should make sure to not regress again here.
>>>>>>>>>>>
>>>>>>>>>>> Thanks,
>>>>>>>>>>> Richard.
>>>>>>>>>>>
>>>>>>>>>>>> ChangeLog.
>>>>>>>>>>>>
>>>>>>>>>>>> 2013-02-20 Yuri Rumyantsev <ysrumyan@gmail.com>
>>>>>>>>>>>>
>>>>>>>>>>>> PR tree-optimization/56175
>>>>>>>>>>>> * tree-ssa-forwprop.c (simplify_bitwise_binary) : Avoid type sinking
>>>>>>>>>>>> at 1st forwprop pass to recognize (A & C) ^ (B & C) -> (A ^ B) & C
>>>>>>>>>>>> for short integer types.
More information about the Gcc-patches
mailing list