2011/10/10 Richard Guenther <richard.guent...@gmail.com>:
> On Mon, Oct 10, 2011 at 5:07 PM, Kai Tietz <ktiet...@googlemail.com> wrote:
>> 2011/10/10 Richard Guenther <richard.guent...@gmail.com>:
>>> On Mon, Oct 10, 2011 at 4:06 PM, Kai Tietz <ktiet...@googlemail.com> wrote:
>>>> 2011/10/10 Richard Guenther <richard.guent...@gmail.com>:
>>>>> On Mon, Oct 10, 2011 at 2:29 PM, Kai Tietz <ktiet...@googlemail.com>
>>>>> wrote:
>>>>>> Recent patch had a thinko on rhs of inner lhs check for TRUTH-IF. It
>>>>>> has to be checked that the LHS code is same as outer CODE, as
>>>>>> otherwise we wouldn't apply different TRUTH-IF only on inner RHS of
>>>>>> LHS, which is of course wrong.
>>>>>>
>>>>>> 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)));
>>>>>
>>>>> And that's still wrong.
>>>>>
>>>>> Stopped reading here.
>>>>>
>>>>> Richard.
>>>>
>>>> Oh, there is a not missing. I didn't spot that, sorry.
>>>>
>>>> To the point why we need to handle comparisons within simple_operand_p.
>>>>
>>>> If we reject comparisons and logical not here, we won't have any
>>>> branching optimization anymore, as this the patch moves into
>>>> fold_truthandor.
>>>>
>>>> The result with rejecting in simple_operand_p compares and logic-not
>>>> provides for the following example:
>>>
>>> But you change what simple_operand_p accepts and thus change what
>>> fold_truthop accepts as operands to its simplifications.
>>>
>>> Richard.
>>
>> Well, not really. I assume you mean fold_truth_andor_1 (aka fold_truthop).
>>
>> It checks for
>> ...
>> if (TREE_CODE_CLASS (lcode) != tcc_comparison
>> || TREE_CODE_CLASS (rcode) != tcc_comparison)
>> return 0;
>> ...
>> before checking for simple_operand_p. So there is actual no change.
>> It might be of some interest here to add in a different patch support
>> for logic-not, but well, this is would be material for a different
>> patch.
>> So, it won't operate on anything else then comparisons as before.
>
> Sure, because simple_operand_p is checked on the comparison
> operands, not the comparison itself.
>
> Richard.
Right, we would allow by this things like (a != b) < (c != d) etc.
Here it seems that only some cases for comparison in comparison are
folded. (eg (a == b) == (c == d) -> (a == b) ^ (c == d) ). Well,
other material for a different patch.
To ensure that we use simple_operand_p in all cases, beside for
branching AND/OR chains, in same way as before, I added to this
function an additional argument, by which
the looking into comparisons can be activated.
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 bool simple_operand_p (tree, bool);
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 +3667,48 @@ sign_bit_p (tree exp, const_tree val)
return NULL_TREE;
}
-/* Subroutine for fold_truthop: determine if an operand is simple enough
- to be evaluated unconditionally. */
+/* Subroutine for fold_truth_andor_1: determine if an operand is simple enough
+ to be evaluated unconditionally.
+ If IN_COMPARES is TRUE, then we assume comparisons and logic-not
+ operations are simple, if their operands are simple. */
-static int
-simple_operand_p (const_tree exp)
+static bool
+simple_operand_p (tree exp, bool in_compares)
{
+ enum tree_code code;
/* Strip any conversions that don't change the machine mode. */
STRIP_NOPS (exp);
+ code = TREE_CODE (exp);
+
+ if (in_compares)
+ {
+ if (TREE_CODE_CLASS (code) == tcc_comparison)
+ return (!tree_could_trap_p (exp)
+ && simple_operand_p (TREE_OPERAND (exp, 0), true)
+ && simple_operand_p (TREE_OPERAND (exp, 1), true));
+
+ 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), true);
+ case BIT_NOT_EXPR:
+ if (TREE_CODE (TREE_TYPE (exp)) != BOOLEAN_TYPE)
+ return false;
+ return simple_operand_p (TREE_OPERAND (exp, 0), true);
+ default:
+ break;
+ }
+ }
+
return (CONSTANT_CLASS_P (exp)
- || TREE_CODE (exp) == SSA_NAME
+ || code == SSA_NAME
|| (DECL_P (exp)
&& ! TREE_ADDRESSABLE (exp)
&& ! TREE_THIS_VOLATILE (exp)
@@ -4858,7 +4888,7 @@ fold_range_test (location_t loc, enum tr
/* If simple enough, just rewrite. Otherwise, make a SAVE_EXPR
unless we are at top level or LHS contains a PLACEHOLDER_EXPR, in
which cases we can't do this. */
- if (simple_operand_p (lhs))
+ if (simple_operand_p (lhs, false))
return build2_loc (loc, code == TRUTH_ANDIF_EXPR
? TRUTH_AND_EXPR : TRUTH_OR_EXPR,
type, op0, op1);
@@ -4888,7 +4918,7 @@ 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 +5055,8 @@ 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 +5084,6 @@ 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
@@ -5091,8 +5119,8 @@ fold_truthop (location_t loc, enum tree_
rr_arg = TREE_OPERAND (rhs, 1);
/* Simplify (x<y) && (x==y) into (x<=y) and related optimizations. */
- if (simple_operand_p (ll_arg)
- && simple_operand_p (lr_arg))
+ if (simple_operand_p (ll_arg, false)
+ && simple_operand_p (lr_arg, false))
{
if (operand_equal_p (ll_arg, rl_arg, 0)
&& operand_equal_p (lr_arg, rr_arg, 0))
@@ -5119,14 +5147,13 @@ 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
&& ! FLOAT_TYPE_P (TREE_TYPE (rl_arg))
- && simple_operand_p (rl_arg)
- && simple_operand_p (rr_arg))
+ && simple_operand_p (rl_arg, false)
+ && simple_operand_p (rr_arg, false))
{
/* Convert (a != 0) || (b != 0) into (a | b) != 0. */
if (code == TRUTH_OR_EXPR
@@ -5149,13 +5176,6 @@ 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 +8400,46 @@ 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, true))
+ {
+ 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 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. */
+ && !TREE_SIDE_EFFECTS (TREE_OPERAND (arg0, 1))
+ && simple_operand_p (TREE_OPERAND (arg0, 1), true))
+ {
+ 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, true))
+ return fold_build2_loc (loc, ncode, type, arg0, arg1);
+ }
+
return NULL_TREE;
}
