Hi,
Thanks for all the suggestions.
Please find attached the modified patch as per your suggestions.
I had missed a mail as pointed by Marc Glisse. Now I have implemented
everything suggested.
Please review the patch and let me know if any further modifications are
required.
I have some queries regarding the whole discussions along the course of
this patch.
It would be very helpful for my understanding of the code.
>> /* Fold (A & ~B) - (A & B) into (A ^ B) - B. */
>> Likewise the fold code handles both constant and non-constant B.
How do we know that fold code handles both constant and non-constant B
and not A?
>> Fold (a * (1 << b)) into (a << b)
>> So either way I think we should only allow nop conversions
>> here (as fold-const.c did).
How do we recognize from the fold-const code that it allows only nop
conversions.
>> We want to minimize the number of lines in match.pd and this doesn't
>> really achieve this compared to duplicating the whole pattern.
Yes. Even, I have the same question to understand this better.
Is it worth and does it acheive any extra optimization after moving
it using simplify and match?
Should I have the other three patterns duplicated and implemented
or leave it in fold-const code?
Thanks,
Naveen
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index de45a2c..1e7fbb4 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -9803,20 +9803,6 @@ fold_binary_loc (location_t loc,
goto associate;
case MULT_EXPR:
- /* (-A) * (-B) -> A * B */
- if (TREE_CODE (arg0) == NEGATE_EXPR && negate_expr_p (arg1))
- return fold_build2_loc (loc, MULT_EXPR, type,
- fold_convert_loc (loc, type,
- TREE_OPERAND (arg0, 0)),
- fold_convert_loc (loc, type,
- negate_expr (arg1)));
- if (TREE_CODE (arg1) == NEGATE_EXPR && negate_expr_p (arg0))
- return fold_build2_loc (loc, MULT_EXPR, type,
- fold_convert_loc (loc, type,
- negate_expr (arg0)),
- fold_convert_loc (loc, type,
- TREE_OPERAND (arg1, 0)));
-
if (! FLOAT_TYPE_P (type))
{
/* Transform x * -C into -x * C if x is easily negatable. */
@@ -9830,16 +9816,6 @@ fold_binary_loc (location_t loc,
negate_expr (arg0)),
tem);
- /* (a * (1 << b)) is (a << b) */
- if (TREE_CODE (arg1) == LSHIFT_EXPR
- && integer_onep (TREE_OPERAND (arg1, 0)))
- return fold_build2_loc (loc, LSHIFT_EXPR, type, op0,
- TREE_OPERAND (arg1, 1));
- if (TREE_CODE (arg0) == LSHIFT_EXPR
- && integer_onep (TREE_OPERAND (arg0, 0)))
- return fold_build2_loc (loc, LSHIFT_EXPR, type, op1,
- TREE_OPERAND (arg0, 1));
-
/* (A + A) * C -> A * 2 * C */
if (TREE_CODE (arg0) == PLUS_EXPR
&& TREE_CODE (arg1) == INTEGER_CST
@@ -9882,21 +9858,6 @@ fold_binary_loc (location_t loc,
}
else
{
- /* Convert (C1/X)*C2 into (C1*C2)/X. This transformation may change
- the result for floating point types due to rounding so it is applied
- only if -fassociative-math was specify. */
- if (flag_associative_math
- && TREE_CODE (arg0) == RDIV_EXPR
- && TREE_CODE (arg1) == REAL_CST
- && TREE_CODE (TREE_OPERAND (arg0, 0)) == REAL_CST)
- {
- tree tem = const_binop (MULT_EXPR, TREE_OPERAND (arg0, 0),
- arg1);
- if (tem)
- return fold_build2_loc (loc, RDIV_EXPR, type, tem,
- TREE_OPERAND (arg0, 1));
- }
-
/* Strip sign operations from X in X*X, i.e. -Y*-Y -> Y*Y. */
if (operand_equal_p (arg0, arg1, 0))
{
@@ -10053,22 +10014,6 @@ fold_binary_loc (location_t loc,
goto bit_rotate;
case BIT_AND_EXPR:
- /* ~X & X, (X == 0) & X, and !X & X are always zero. */
- if ((TREE_CODE (arg0) == BIT_NOT_EXPR
- || TREE_CODE (arg0) == TRUTH_NOT_EXPR
- || (TREE_CODE (arg0) == EQ_EXPR
- && integer_zerop (TREE_OPERAND (arg0, 1))))
- && operand_equal_p (TREE_OPERAND (arg0, 0), arg1, 0))
- return omit_one_operand_loc (loc, type, integer_zero_node, arg1);
-
- /* X & ~X , X & (X == 0), and X & !X are always zero. */
- if ((TREE_CODE (arg1) == BIT_NOT_EXPR
- || TREE_CODE (arg1) == TRUTH_NOT_EXPR
- || (TREE_CODE (arg1) == EQ_EXPR
- && integer_zerop (TREE_OPERAND (arg1, 1))))
- && operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0))
- return omit_one_operand_loc (loc, type, integer_zero_node, arg0);
-
/* Fold (X ^ 1) & 1 as (X & 1) == 0. */
if (TREE_CODE (arg0) == BIT_XOR_EXPR
&& INTEGRAL_TYPE_P (type)
diff --git a/gcc/match.pd b/gcc/match.pd
index 655c9ff..2e0b919 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -323,6 +323,27 @@ along with GCC; see the file COPYING3. If not see
(if (real_isinteger (&TREE_REAL_CST (@1), &n) && (n & 1) == 0)
(pows @0 @1))))))
+/* Fold (a * (1 << b)) into (a << b) */
+(simplify
+ (mult:c @0 (lshift integer_onep@1 @2))
+ (if (! FLOAT_TYPE_P (type)
+ && tree_nop_conversion_p (type, TREE_TYPE (@1)))
+ (lshift @0 @2)))
+
+/* Fold (C1/X)*C2 into (C1*C2)/X. */
+(simplify
+ (mult (rdiv:s REAL_CST@0 @1) REAL_CST@2)
+ (if (flag_associative_math)
+ (with
+ { tree tem = const_binop (MULT_EXPR, type, @0, @2); }
+ (if (tem)
+ (rdiv { tem; } @1)))))
+
+/* Simplify ~X & X as zero. */
+(simplify
+ (bit_and:c (convert? @0) (convert? (bit_not @0)))
+ { build_zero_cst (type); })
+
/* X % Y is smaller than Y. */
(for cmp (lt ge)
(simplify
@@ -542,6 +563,13 @@ along with GCC; see the file COPYING3. If not see
(match negate_expr_p
VECTOR_CST
(if (FLOAT_TYPE_P (TREE_TYPE (type)) || TYPE_OVERFLOW_WRAPS (type))))
+
+/* (-A) * (-B) -> A * B */
+(simplify
+ (mult:c (convert1? (negate @0)) (convert2? negate_expr_p@1))
+ (if (tree_nop_conversion_p (type, TREE_TYPE (@0))
+ && tree_nop_conversion_p (type, TREE_TYPE (@1)))
+ (mult (convert @0) (convert (negate @1)))))
/* -(A + B) -> (-B) - A. */
(simplify
