On Mon, Oct 17, 2011 at 1:31 PM, Kai Tietz <ktiet...@googlemail.com> wrote:
> 2011/10/17 Richard Guenther <richard.guent...@gmail.com>:
>> On Mon, Oct 17, 2011 at 12:59 PM, Kai Tietz <ktiet...@googlemail.com> wrote:
>>> 2011/10/17 Richard Guenther <richard.guent...@gmail.com>:
>>>> On Fri, Oct 14, 2011 at 9:43 PM, Kai Tietz <ktiet...@googlemail.com> wrote:
>>>>> Hello,
>>>>>
>>>>> So I committed the gimplify patch separate. And here is the remaining
>>>>> fold-const patch.
>>>>> The important tests here are in gcc.dg/tree-ssa/builtin-expect[1-4].c,
>>>>> which
>>>>> cover the one special-case for branching. Also tree-ssa/20040204-1.c
>>>>> covers
>>>>> tests for branching code (on targets having high-engough BRANCH_COST and
>>>>> no
>>>>> special-casing - like MIPS, S/390, and AVR.
>>>>>
>>>>> ChangeLog
>>>>>
>>>>> 2011-10-14 Kai Tietz <kti...@redhat.com>
>>>>>
>>>>> * fold-const.c (simple_operand_p_2): New function.
>>>>> (fold_truthop): Rename to
>>>>> (fold_truth_andor_1): function name.
>>>>> Additionally remove branching creation for logical and/or.
>>>>> (fold_truth_andor): Handle branching creation for logical and/or
>>>>> here.
>>>>>
>>>>> Bootstrapped and regression-tested for all languages plus Ada and
>>>>> Obj-C++ on x86_64-pc-linux-gnu.
>>>>> Ok for apply?
>>>>
>>>> Ok with ...
>>>>
>>>>> Regards,
>>>>> Kai
>>>>>
>>>>> Index: gcc/gcc/fold-const.c
>>>>> ===================================================================
>>>>> --- gcc.orig/gcc/fold-const.c
>>>>> +++ gcc/gcc/fold-const.c
>>>>> @@ -112,13 +112,13 @@ static tree decode_field_reference (loca
>>>>> static int all_ones_mask_p (const_tree, int);
>>>>> static tree sign_bit_p (tree, const_tree);
>>>>> static int simple_operand_p (const_tree);
>>>>> +static bool simple_operand_p_2 (tree);
>>>>> static tree range_binop (enum tree_code, tree, tree, int, tree, int);
>>>>> static tree range_predecessor (tree);
>>>>> static tree range_successor (tree);
>>>>> static tree fold_range_test (location_t, enum tree_code, tree, tree,
>>>>> tree);
>>>>> static tree fold_cond_expr_with_comparison (location_t, tree, tree,
>>>>> tree, tree);
>>>>> static tree unextend (tree, int, int, tree);
>>>>> -static tree fold_truthop (location_t, enum tree_code, tree, tree, tree);
>>>>> static tree optimize_minmax_comparison (location_t, enum tree_code,
>>>>> tree, tree, tree);
>>>>> static tree extract_muldiv (tree, tree, enum tree_code, tree, bool *);
>>>>> @@ -3500,7 +3500,7 @@ optimize_bit_field_compare (location_t l
>>>>> return lhs;
>>>>> }
>>>>>
>>>>> -/* Subroutine for fold_truthop: decode a field reference.
>>>>> +/* Subroutine for fold_truth_andor_1: decode a field reference.
>>>>>
>>>>> If EXP is a comparison reference, we return the innermost reference.
>>>>>
>>>>> @@ -3668,7 +3668,7 @@ sign_bit_p (tree exp, const_tree val)
>>>>> return NULL_TREE;
>>>>> }
>>>>>
>>>>> -/* Subroutine for fold_truthop: determine if an operand is simple enough
>>>>> +/* Subroutine for fold_truth_andor_1: determine if an operand is simple
>>>>> enough
>>>>> to be evaluated unconditionally. */
>>>>>
>>>>> static int
>>>>> @@ -3678,7 +3678,7 @@ simple_operand_p (const_tree exp)
>>>>> STRIP_NOPS (exp);
>>>>>
>>>>> return (CONSTANT_CLASS_P (exp)
>>>>> - || TREE_CODE (exp) == SSA_NAME
>>>>> + || TREE_CODE (exp) == SSA_NAME
>>>>> || (DECL_P (exp)
>>>>> && ! TREE_ADDRESSABLE (exp)
>>>>> && ! TREE_THIS_VOLATILE (exp)
>>>>> @@ -3692,6 +3692,46 @@ simple_operand_p (const_tree exp)
>>>>> registers aren't expensive. */
>>>>> && (! TREE_STATIC (exp) || DECL_REGISTER (exp))));
>>>>> }
>>>>> +
>>>>> +/* Subroutine for fold_truth_andor: determine if an operand is simple
>>>>> enough
>>>>> + to be evaluated unconditionally.
>>>>> + I addition to simple_operand_p, we assume that comparisons and
>>>>> logic-not
>>>>> + operations are simple, if their operands are simple, too. */
>>>>> +
>>>>> +static bool
>>>>> +simple_operand_p_2 (tree exp)
>>>>> +{
>>>>> + enum tree_code code;
>>>>> +
>>>>> + /* Strip any conversions that don't change the machine mode. */
>>>>> + STRIP_NOPS (exp);
>>>>> +
>>>>> + code = TREE_CODE (exp);
>>>>> +
>>>>> + if (TREE_CODE_CLASS (code) == tcc_comparison)
>>>>> + return (!tree_could_trap_p (exp)
>>>>> + && simple_operand_p_2 (TREE_OPERAND (exp, 0))
>>>>> + && simple_operand_p_2 (TREE_OPERAND (exp, 1)));
>>>>
>>>> recurse with simple_operand_p.
>>>
>>> No, as this again would reject simple operations and additionally
>>> wouldn't check for trapping.
>>
>> ? Your code allows arbitrarily complex expressions. Also
>> tree_could_trap_p obviously extents to operands.
>
> Ah, ok. I wasn't aware that it walks into tree.
>
>>>
>>>>> +
>>>>> + if (TREE_SIDE_EFFECTS (exp)
>>>>> + || tree_could_trap_p (exp))
>>>>
>>>> Move this check before the tcc_comparison check and remove the
>>>> then redundant tree_could_trap_p check there.
>>>
>>> Ok
>>>
>>>>> + return false;
>>>>> +
>>>>> + switch (code)
>>>>> + {
>>>>> + case SSA_NAME:
>>>>> + return true;
>>>>
>>>> Do not handle here, it's handled in simple_operand_p.
>>>
>>> Well, was more a short-cut here.
>>>
>>>>> + case TRUTH_NOT_EXPR:
>>>>> + return simple_operand_p_2 (TREE_OPERAND (exp, 0));
>>>>> + case BIT_NOT_EXPR:
>>>>> + if (TREE_CODE (TREE_TYPE (exp)) != BOOLEAN_TYPE)
>>>>> + return false;
>>>>
>>>> Remove the BIT_NOT_EXPR handling. Thus, simply change this switch
>>>> to
>>>
>>> Why should we reject simple ~X operations from gimplified code here?
>>
>> Because this is FE triggered code. From gimple you won't ever see
>> such complex expressions (never even the TRUTH_AND*_EXPR variants).
>
> Hmm, I thought we might see such thing in fold and/or. But well, you
> might be right.
>
>>> I admit that from FE-code we won't see that, as always an integer-cast
>>> is done for foo (_Bool x) { ... if (~x) ... }, but from
>>> gimplified-code this is the general description of an boolean-typed !=
>>> 0?
>>>
>>>> if (code == TRUTH_NOT_EXPR)
>>>> return simple_operand_p_2 (TREE_OPERAND (exp, 0));
>>>>
>>>> return simple_operand_p (exp);
>>>>
>>>>> + return simple_operand_p_2 (TREE_OPERAND (exp, 0));
>>>>> + default:
>>>>> + return simple_operand_p (exp);
>>>>> + }
>>>>> +}
>>>>> +
>>>>>
>>>>> /* The following functions are subroutines to fold_range_test and allow
>>>>> it to
>>>>> try to change a logical combination of comparisons into a range test.
>>>>> @@ -4888,7 +4928,7 @@ fold_range_test (location_t loc, enum tr
>>>>> return 0;
>>>>> }
>>>>>
>>>>> -/* Subroutine for fold_truthop: C is an INTEGER_CST interpreted as a P
>>>>> +/* Subroutine for fold_truth_andor_1: C is an INTEGER_CST interpreted as
>>>>> a P
>>>>> bit value. Arrange things so the extra bits will be set to zero if and
>>>>> only if C is signed-extended to its full width. If MASK is nonzero,
>>>>> it is an INTEGER_CST that should be AND'ed with the extra bits. */
>>>>> @@ -5025,8 +5065,8 @@ merge_truthop_with_opposite_arm (locatio
>>>>> We return the simplified tree or 0 if no optimization is possible. */
>>>>>
>>>>> static tree
>>>>> -fold_truthop (location_t loc, enum tree_code code, tree truth_type,
>>>>> - tree lhs, tree rhs)
>>>>> +fold_truth_andor_1 (location_t loc, enum tree_code code, tree truth_type,
>>>>> + tree lhs, tree rhs)
>>>>> {
>>>>> /* If this is the "or" of two comparisons, we can do something if
>>>>> the comparisons are NE_EXPR. If this is the "and", we can do
>>>>> something
>>>>> @@ -5054,8 +5094,6 @@ fold_truthop (location_t loc, enum tree_
>>>>> tree lntype, rntype, result;
>>>>> HOST_WIDE_INT first_bit, end_bit;
>>>>> int volatilep;
>>>>> - tree orig_lhs = lhs, orig_rhs = rhs;
>>>>> - enum tree_code orig_code = code;
>>>>>
>>>>> /* Start by getting the comparison codes. Fail if anything is volatile.
>>>>> If one operand is a BIT_AND_EXPR with the constant one, treat it as
>>>>> if
>>>>> @@ -5119,8 +5157,7 @@ fold_truthop (location_t loc, enum tree_
>>>>> /* If the RHS can be evaluated unconditionally and its operands are
>>>>> simple, it wins to evaluate the RHS unconditionally on machines
>>>>> with expensive branches. In this case, this isn't a comparison
>>>>> - that can be merged. Avoid doing this if the RHS is a floating-point
>>>>> - comparison since those can trap. */
>>>>> + that can be merged. */
>>>>>
>>>>> if (BRANCH_COST (optimize_function_for_speed_p (cfun),
>>>>> false) >= 2
>>>>> @@ -5149,13 +5186,6 @@ fold_truthop (location_t loc, enum tree_
>>>>> build2 (BIT_IOR_EXPR, TREE_TYPE (ll_arg),
>>>>> ll_arg, rl_arg),
>>>>> build_int_cst (TREE_TYPE (ll_arg), 0));
>>>>> -
>>>>> - if (LOGICAL_OP_NON_SHORT_CIRCUIT)
>>>>> - {
>>>>> - if (code != orig_code || lhs != orig_lhs || rhs != orig_rhs)
>>>>> - return build2_loc (loc, code, truth_type, lhs, rhs);
>>>>> - return NULL_TREE;
>>>>> - }
>>>>> }
>>>>>
>>>>> /* See if the comparisons can be merged. Then get all the parameters
>>>>> for
>>>>> @@ -8380,13 +8410,49 @@ fold_truth_andor (location_t loc, enum t
>>>>> lhs is another similar operation, try to merge its rhs with our
>>>>> rhs. Then try to merge our lhs and rhs. */
>>>>> if (TREE_CODE (arg0) == code
>>>>> - && 0 != (tem = fold_truthop (loc, code, type,
>>>>> - TREE_OPERAND (arg0, 1), arg1)))
>>>>> + && 0 != (tem = fold_truth_andor_1 (loc, code, type,
>>>>> + TREE_OPERAND (arg0, 1), arg1)))
>>>>> return fold_build2_loc (loc, code, type, TREE_OPERAND (arg0, 0), tem);
>>>>>
>>>>> - if ((tem = fold_truthop (loc, code, type, arg0, arg1)) != 0)
>>>>> + if ((tem = fold_truth_andor_1 (loc, code, type, arg0, arg1)) != 0)
>>>>> return tem;
>>>>>
>>>>> + if ((code == TRUTH_ANDIF_EXPR || code == TRUTH_ORIF_EXPR)
>>>>> + && (BRANCH_COST (optimize_function_for_speed_p (cfun),
>>>>> + false) >= 2)
>>>>> + && LOGICAL_OP_NON_SHORT_CIRCUIT
>>>>> + && simple_operand_p_2 (arg1))
>>>>> + {
>>>>> + enum tree_code ncode = (code == TRUTH_ANDIF_EXPR ? TRUTH_AND_EXPR
>>>>> + : TRUTH_OR_EXPR);
>>>>> +
>>>>> + /* Transform ((A AND-IF B) AND-IF C) into (A AND-IF (B AND C)),
>>>>> + or ((A OR-IF B) OR-IF C) into (A OR-IF (B OR C))
>>>>> + We don't want to pack more than two leafs to a non-IF AND/OR
>>>>> + expression.
>>>>> + If tree-code of left-hand operand isn't an AND/OR-IF code and
>>>>> not
>>>>> + equal to CODE, then we don't want to add right-hand operand.
>>>>> + If the inner right-hand side of left-hand operand has
>>>>> side-effects,
>>>>> + or isn't simple, then we can't add to it, as otherwise we might
>>>>> + destroy if-sequence. */
>>>>> + if (TREE_CODE (arg0) == code
>>>>> + /* Needed for sequence points to handle trappings, and
>>>>> + side-effects. */
>>>>> + && simple_operand_p_2 (TREE_OPERAND (arg0, 1)))
>>>>> + {
>>>>> + tem = fold_build2_loc (loc, ncode, type, TREE_OPERAND (arg0, 1),
>>>>> + arg1);
>>>>> + return fold_build2_loc (loc, code, type, TREE_OPERAND (arg0, 0),
>>>>> + tem);
>>>>> + }
>>>>
>>>> I see you insist on this change. Let me explain again. You do this
>>>> for ((A AND-IF B) AND-IF C) but you don't do this for
>>>> ((A AND-IF B) AND C). Why? That is what doesn't make sense ot me.
>>>> Thus omit this hunk.
>>>
>>> Well, first ((A AND-IF B) AND C) would be an ill sequence, as AND is
>>> associative. So we would simply break sequence points for && and ||.
>>> If left-hand operand is an AND/OR-IF then outer operand has to always
>>> an ?-IF operation, too.
>>
>> Why? It's something like (ptr && *ptr) & x. Whether you evaluate
>> x or (ptr && *ptr) first does not matter. But you have to check
>> whether ptr is non-null before dereferencing it. So it's clearly not
>> ill-formed. You may argue the transform is pointless and we should
>> associate the & instead. Do you?
>
> well, if you are explict writing such thing as binary-and, it would be
> associative anyway and code doesn't change here anything. Binary and
> != logical and. The point about if we see something as (A TRUTH-IF B)
> TRUTH B), we don't want to change it at all. The outer if for this
> already checks that this operation is just to be used on TRUTH-IF. To
> modify a TRUTH to a TRUTH is pretty point-less, isn't it? If we would
> allow to sink the case (A TRUTH-IF B) TRUTH C to (A TRUTH-IF (B TRUTH
> C)), which might be of some intererest, but still would change
> association rule here from point of C specification. By C standard
> each ||,&& is treated as a separate sequence-point. Only in case that
> previous and next &&/|| operand have no side-effects, we can apply to
> them associative law. Or do I read C-spec here wrong?
Certainly if for (A TRUTH-IF B) TRUTH-IF C it is valid to associate
it as A TRUTH-IF (B IF C) then it is valid to do the same for
(A TRUTH-IF B) IF C.
> Regards,
> Kai
>
