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fold-const.c (fold): Optimize unsigned modulus by a power of two into a bit-wise AND, i.e.

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* fold-const.c (fold) <TRUNC_MOD_EXPR>: Optimize unsigned modulus
	by a power of two into a bit-wise AND, i.e. "X % C" as "X & (C-1)".
	Normalize "X % C" as "X % -C" for signed modulus and negative C.
	Optimize "X % -Y" as "X % Y" for signed modulus.
	<EQ_EXPR>: Recursively call "fold" when transforming "(X % Y) == 0"
	into "((unsigned) X % Y) == 0".

From-SVN: r84122
This commit is contained in:
Roger Sayle 2004-07-05 16:44:17 +00:00 committed by Roger Sayle
parent 48eb4e53cd
commit ab0e8f666d
2 changed files with 63 additions and 6 deletions
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9
gcc/ChangeLog
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@ -1,3 +1,12 @@
2004-07-05 Roger Sayle <roger@eyesopen.com>
* fold-const.c (fold) <TRUNC_MOD_EXPR>: Optimize unsigned modulus
by a power of two into a bit-wise AND, i.e. "X % C" as "X & (C-1)".
Normalize "X % C" as "X % -C" for signed modulus and negative C.
Optimize "X % -Y" as "X % Y" for signed modulus.
<EQ_EXPR>: Recursively call "fold" when transforming "(X % Y) == 0"
into "((unsigned) X % Y) == 0".
2004-07-05 Joseph S. Myers <jsm@polyomino.org.uk>
* sourcebuild.texi (Config Fragments): Use @comma{} in

60
gcc/fold-const.c
View File

@ -7538,6 +7538,7 @@ fold (tree expr)
return omit_one_operand (type, integer_zero_node, arg0);
if (integer_zerop (arg1))
return t;
/* X % -1 is zero. */
if (!TYPE_UNSIGNED (type)
&& TREE_CODE (arg1) == INTEGER_CST
@ -7545,6 +7546,52 @@ fold (tree expr)
&& TREE_INT_CST_HIGH (arg1) == -1)
return omit_one_operand (type, integer_zero_node, arg0);
/* Optimize unsigned TRUNC_MOD_EXPR by a power of two into a
BIT_AND_EXPR, i.e. "X % C" into "X & C2". */
if (code == TRUNC_MOD_EXPR
&& TYPE_UNSIGNED (type)
&& integer_pow2p (arg1))
{
unsigned HOST_WIDE_INT high, low;
tree mask;
int l;
l = tree_log2 (arg1);
if (l >= HOST_BITS_PER_WIDE_INT)
{
high = ((unsigned HOST_WIDE_INT) 1
<< (l - HOST_BITS_PER_WIDE_INT)) - 1;
low = -1;
}
else
{
high = 0;
low = ((unsigned HOST_WIDE_INT) 1 << l) - 1;
}
mask = build_int_2 (low, high);
TREE_TYPE (mask) = type;
return fold (build2 (BIT_AND_EXPR, type,
fold_convert (type, arg0), mask));
}
/* X % -C is the same as X % C (for all rounding moduli). */
if (!TYPE_UNSIGNED (type)
&& TREE_CODE (arg1) == INTEGER_CST
&& TREE_INT_CST_HIGH (arg1) < 0
&& !flag_trapv
/* Avoid this transformation if C is INT_MIN, i.e. C == -C. */
&& !sign_bit_p (arg1, arg1))
return fold (build2 (code, type, fold_convert (type, arg0),
fold_convert (type, negate_expr (arg1))));
/* X % -Y is the same as X % Y (for all rounding moduli). */
if (!TYPE_UNSIGNED (type)
&& TREE_CODE (arg1) == NEGATE_EXPR
&& !flag_trapv)
return fold (build2 (code, type, fold_convert (type, arg0),
fold_convert (type, TREE_OPERAND (arg1, 0))));
if (TREE_CODE (arg1) == INTEGER_CST
&& 0 != (tem = extract_muldiv (TREE_OPERAND (t, 0), arg1,
code, NULL_TREE)))
@ -8268,13 +8315,14 @@ fold (tree expr)
&& integer_pow2p (TREE_OPERAND (arg0, 1)))
{
tree newtype = lang_hooks.types.unsigned_type (TREE_TYPE (arg0));
tree newmod = build2 (TREE_CODE (arg0), newtype,
fold_convert (newtype,
TREE_OPERAND (arg0, 0)),
fold_convert (newtype,
TREE_OPERAND (arg0, 1)));
tree newmod = fold (build2 (TREE_CODE (arg0), newtype,
fold_convert (newtype,
TREE_OPERAND (arg0, 0)),
fold_convert (newtype,
TREE_OPERAND (arg0, 1))));
return build2 (code, type, newmod, fold_convert (newtype, arg1));
return fold (build2 (code, type, newmod,
fold_convert (newtype, arg1)));
}
/* If this is an NE comparison of zero with an AND of one, remove the