2011/10/10 Richard Guenther <richard.guent...@gmail.com>:
> On Fri, Oct 7, 2011 at 11:36 PM, Kai Tietz <ktiet...@googlemail.com> wrote:
>> Hello,
>>
>> this is the updated version with the suggestion
>>
>> 2011/10/7 Richard Guenther <richard.guent...@gmail.com>:
>>> On Thu, Oct 6, 2011 at 4:25 PM, Kai Tietz <kti...@redhat.com> wrote:
>>>> + && ((TREE_CODE_CLASS (TREE_CODE (arg1)) != tcc_comparison
>>>> + && TREE_CODE (arg1) != TRUTH_NOT_EXPR
>>>> + && simple_operand_p (arg1))
>>>
>>> As I said previously simple_operand_p already rejects covers
>>> comparisons and TRUTH_NOT_EXPR. Also arg1 had better
>>> TREE_SIDE_EFFECTS set if the comparison might trap, as
>>> it might just be hidden in something more complicated - so
>>> the simple check isn't enough anyway (and if simple_operand_p
>>> would cover it, the check would be better placed there).
>>
>> I reworked simple_operand_p so that it does this special-casing and
>> additionally
>> also checks for trapping.
>>
>>>> + if (TREE_CODE (arg0) == code
>>>> + && !TREE_SIDE_EFFECTS (TREE_OPERAND (arg0, 1))
>>>> + && simple_operand_p (TREE_OPERAND (arg0, 1)))
>>>> + {
>>>> + tem = build2_loc (loc,
>>>> + (code == TRUTH_ANDIF_EXPR ? TRUTH_AND_EXPR
>>>> + : TRUTH_OR_EXPR),
>>>> + type, TREE_OPERAND (arg0, 1), arg1);
>>>> + return build2_loc (loc, code, type, TREE_OPERAND (arg0, 0),
>>>> + tem);
>>>
>>> All trees should be folded, don't use plain build without a good reason.
>>
>> Ok, done
>>
>>>> + }
>>>> + /* Convert X TRUTH-ANDORIF Y to X TRUTH-ANDOR Y, if X and Y
>>>> + are simple operands and have no side-effects. */
>>>> + if (simple_operand_p (arg0)
>>>> + && !TREE_SIDE_EFFECTS (arg0))
>>>
>>> Again, the checks you do for arg0 do not match those for arg1. OTOH
>>> it doesn't matter whether arg0 is simple or not or has side-effects or
>>> not for this transformation, so why check it at all?
>>
>> It is required. For left-hand operand, if it isn't a logical
>> and/or/xor, we need to check for side-effects (and for trapping). I
>> see that calling of simple_operand_p is wrong here, as it rejects too
>> much. Nevertheless the check for side-effects is necessary for having
>> valid sequence-points. Without that checking a simple test
>>
>> int getter (void);
>>
>> int foo (void)
>> {
>> int c, r = 0;
>> while ((c = getter ()) != '"' && c >= 0)
>> r +=c;
>> return r;
>> }
>>
>> would give a warning about sequence-points. As left-hand operand has
>> side-effects, but right-hand not. If we would combine it as AND, the
>> operands are exchange-able. So right-hand operand needs to be another
>> ANDIF expression instead.
>> Same apply on trapping.
>>
>>> In fold_truthop we still have the same (albeit more restricted transform),
>>> but guarded with
>>>
>>> if (BRANCH_COST (optimize_function_for_speed_p (cfun),
>>> false) >= 2
>>>
>>> too. Why not here? Please delete redundant code in fold_truthop.
>> Well, in general this is the default definition of
>> LOGICAL_OP_NON_SHORT_CIRCUIT, so I missed that. As for some targets
>> the macro LOGICAL_OP_NON_SHORT_CIRCUIT might be defined differently,
>> it might make sense to check for BRANCH_COST again.
>>
>>> It's also odd that this is only called from fold_truth_andor but has
>>> a more generic name, so maybe rename it to fold_truth_andor_1 on the way.
>>
>> I renamed it.
>>
>>> Richard.
>>
>> ChangeLog
>>
>> 2011-10-07 Kai Tietz <kti...@redhat.com>
>>
>> * fold-const.c (simple_operand_p): Make argument non-const
>> and add floating-point trapping check, and special cases for
>> comparisons, and logical-not's.
>> (fold_truthop): Rename to
>> (fold_truth_andor_1): function name.
>> Additionally remove here TRUTH-AND|OR_EXPR generation.
>> (fold_truth_andor): Handle branching at one place.
>>
>> Bootstrapped and regression-tested for all languages plus Ada and
>> Obj-C++ on x86_64-pc-linux-gnu.
>> Ok for apply?
>>
>> Regards,
>> Kai
>>
>> Index: gcc/gcc/fold-const.c
>> ===================================================================
>> --- gcc.orig/gcc/fold-const.c
>> +++ gcc/gcc/fold-const.c
>> @@ -111,14 +111,13 @@ static tree decode_field_reference (loca
>> tree *, tree *);
>> 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 int simple_operand_p (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 +3499,7 @@ 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.
>>
>> @@ -3668,17 +3667,43 @@ 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
>> -simple_operand_p (const_tree exp)
>> +simple_operand_p (tree exp)
>> {
>> + enum tree_code code;
>> /* Strip any conversions that don't change the machine mode. */
>> STRIP_NOPS (exp);
>>
>> + code = TREE_CODE (exp);
>> +
>> + /* Handle some trivials $$$$ */
>> + if (TREE_CODE_CLASS (code) == tcc_comparison)
>> + return (tree_could_trap_p (exp)
>> + && simple_operand_p (TREE_OPERAND (exp, 0))
>> + && simple_operand_p (TREE_OPERAND (exp, 1)));
>
> Clearly wrong. And what's $$$$ supposed to be?
The $$$$ was a marker. Will remove here from patch
>> +
>> + if (FLOAT_TYPE_P (TREE_TYPE (exp))
>> + && tree_could_trap_p (exp))
>> + return false;
>> +
>> + switch (code)
>> + {
>> + case SSA_NAME:
>> + return true;
>> + case TRUTH_NOT_EXPR:
>> + return simple_operand_p (TREE_OPERAND (exp, 0));
>> + case BIT_NOT_EXPR:
>> + if (TREE_CODE (TREE_TYPE (exp)) != BOOLEAN_TYPE)
>> + return false;
>> + return simple_operand_p (TREE_OPERAND (exp, 0));
>> + default:
>> + break;
>> + }
>> +
>
> You add a lot of cases here without a good reason. Why in this patch?
> Simply removing the tcc_comparison checks would have been enough ...
We should treat comparisons and truth-not expressions as simple to
allow folding on them. But the more important point for this here
is, that we need to see if we might have floating-point trapping in
such comparisons. Also for high branching costs we want to evaluate
two expressions together. If we don't allow comparisons and truth-not
here, we would always end-up for such with a sequences of (AND|OR)IF
expressions for no good reason.
>> return (CONSTANT_CLASS_P (exp)
>> - || TREE_CODE (exp) == SSA_NAME
>> || (DECL_P (exp)
>> && ! TREE_ADDRESSABLE (exp)
>> && ! TREE_THIS_VOLATILE (exp)
>> @@ -4888,7 +4913,7 @@ 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
>
> fold_truth_andor
>
>> 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 +5050,8 @@ 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 +5079,6 @@ 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 +5142,7 @@ 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 +5171,6 @@ 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 +8395,52 @@ 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)
>> + && !TREE_SIDE_EFFECTS (arg1)
>> + && LOGICAL_OP_NON_SHORT_CIRCUIT
>> + && simple_operand_p (arg1))
>> + {
>> + enum tree_code ncode = (code == TRUTH_ANDIF_EXPR ? TRUTH_AND_EXPR
>> + : TRUTH_OR_EXPR);
>> +
>> + /* We don't want to pack more then two non-IF branches
>> + together. Therefore we need to check, if rhs isn't
>> + already an TRUTH_(XOR|OR|AND)[IF]_EXPR. */
>
> which means, just check if (simple_operand_p (arg0)) ...
>
>> + if (TREE_CODE (arg0) == code
>> + && TREE_CODE (TREE_OPERAND (arg0, 1)) != TRUTH_AND_EXPR
>> + && TREE_CODE (TREE_OPERAND (arg0, 1)) != TRUTH_OR_EXPR
>> + && TREE_CODE (TREE_OPERAND (arg0, 1)) != TRUTH_XOR_EXPR
>> + && TREE_CODE (TREE_OPERAND (arg0, 1)) != TRUTH_ANDIF_EXPR
>> + && TREE_CODE (TREE_OPERAND (arg0, 1)) != TRUTH_ORIF_EXPR
>> + /* Needed for sequence points and trappings, or side-effects. */
>> + && !TREE_SIDE_EFFECTS (TREE_OPERAND (arg0, 1))
>> + && !tree_could_trap_p (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);
>
> Don't do this association here. Why should it not be applied to
> (a TRUTH_ANDIF_EXPR b) TRUTH_AND_EXPR c?
Again, this would destroy sequence. As associative law might be used.
It might be that a, or b have side-effects and changing value of c.
So we have here the same reason.
> Thus, if you
> want to associate the above if b and c do not have side-effects then
> do so generally, not only when you are converting a TRUTH_ANDIF_EXPR
> to TRUTH_AND_EXPR.
There is no need to change an TRUTH_AND_EXPR to an TRUTH_AND_EXPR
here. So this case is not of much interest and would just be costy.
> Thus, please remove this association code.
>
>> + }
>> + else if (TREE_CODE (arg0) != TRUTH_AND_EXPR
>> + && TREE_CODE (arg0) != TRUTH_OR_EXPR
>> + && TREE_CODE (arg0) != TRUTH_ANDIF_EXPR
>> + && TREE_CODE (arg0) != TRUTH_ORIF_EXPR
>> + && TREE_CODE (arg0) != TRUTH_XOR_EXPR
>> + /* Needed for sequence points and trappings, or side-effects.
>> */
>> + && !TREE_SIDE_EFFECTS (arg0)
>> + && !tree_could_trap_p (arg0))
>
> See above.
Yes. see above.
> You made the patch more complex when I asked for a simpler one.
Updated patch attached with checking for right-hand operand with same
properties as for left-hand operand .
Regards,
Kai
Index: gcc/gcc/fold-const.c
===================================================================
--- gcc.orig/gcc/fold-const.c
+++ gcc/gcc/fold-const.c
@@ -111,14 +111,13 @@ static tree decode_field_reference (loca
tree *, tree *);
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 int simple_operand_p (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 +3499,7 @@ 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.
@@ -3668,17 +3667,43 @@ 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
-simple_operand_p (const_tree exp)
+simple_operand_p (tree exp)
{
+ enum tree_code code;
/* Strip any conversions that don't change the machine mode. */
STRIP_NOPS (exp);
+ code = TREE_CODE (exp);
+
+ /* Handle some trivials */
+ if (TREE_CODE_CLASS (code) == tcc_comparison)
+ return (tree_could_trap_p (exp)
+ && simple_operand_p (TREE_OPERAND (exp, 0))
+ && simple_operand_p (TREE_OPERAND (exp, 1)));
+
+ if (FLOAT_TYPE_P (TREE_TYPE (exp))
+ && tree_could_trap_p (exp))
+ return false;
+
+ switch (code)
+ {
+ case SSA_NAME:
+ return true;
+ case TRUTH_NOT_EXPR:
+ return simple_operand_p (TREE_OPERAND (exp, 0));
+ case BIT_NOT_EXPR:
+ if (TREE_CODE (TREE_TYPE (exp)) != BOOLEAN_TYPE)
+ return false;
+ return simple_operand_p (TREE_OPERAND (exp, 0));
+ default:
+ break;
+ }
+
return (CONSTANT_CLASS_P (exp)
- || TREE_CODE (exp) == SSA_NAME
|| (DECL_P (exp)
&& ! TREE_ADDRESSABLE (exp)
&& ! TREE_THIS_VOLATILE (exp)
@@ -4888,7 +4913,7 @@ 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 +5050,8 @@ 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 +5079,6 @@ 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 +5142,7 @@ 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 +5171,6 @@ 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 +8395,47 @@ 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)
+ && !TREE_SIDE_EFFECTS (arg1)
+ && LOGICAL_OP_NON_SHORT_CIRCUIT
+ && simple_operand_p (arg1))
+ {
+ enum tree_code ncode = (code == TRUTH_ANDIF_EXPR ? TRUTH_AND_EXPR
+ : TRUTH_OR_EXPR);
+
+ /* We don't want to pack more then two leafs to an non-IF
+ If tree-code of left-hand operand isn't an AND/OR-IF 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) == TRUTH_ANDIF_EXPR
+ || TREE_CODE (arg0) == TRUTH_ORIF_EXPR)
+ /* Needed for sequence points to handle trappings, and
+ side-effects. */
+ && !TREE_SIDE_EFFECTS (TREE_OPERAND (arg0, 1))
+ && simple_operand_p (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);
+ }
+ /* Needed for sequence points to handle trappings, and side-effects. */
+ else if (!TREE_SIDE_EFFECTS (arg0)
+ && simple_operand_p (arg0))
+ return fold_build2_loc (loc, ncode, type, arg0, arg1);
+ }
+
return NULL_TREE;
}
