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fold-const.c (fold): Fold (A & ~B) - (A & B) into (A ^ B) - B, where B is any power of 2 minus 1.

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* fold-const.c (fold): Fold (A & ~B) - (A & B) into
	(A ^ B) - B, where B is any power of 2 minus 1.

From-SVN: r71910
This commit is contained in:
Kazu Hirata 2003-09-29 17:35:11 +00:00 • committed by Kazu Hirata
parent 1ffcc35206
commit 38b35623d3
2 changed files with 28 additions and 0 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2003-09-29 Kazu Hirata <kazu@cs.umass.edu>
* fold-const.c (fold): Fold (A & ~B) - (A & B) into
(A ^ B) - B, where B is any power of 2 minus 1.
Mon Sep 29 19:05:46 CEST 2003 Jan Hubicka <jh@suse.cz>
* libgcov.c (gcov_exit): Fix two pastos.

23
gcc/fold-const.c
View file

@ -6017,6 +6017,29 @@ fold (tree expr)
TREE_OPERAND (arg1, 1))),
arg0));
}
/* Fold (A & ~B) - (A & B) into (A ^ B) - B, , where B is
any power of 2 minus 1. */
if (TREE_CODE (arg0) == BIT_AND_EXPR
&& TREE_CODE (arg1) == BIT_AND_EXPR
&& operand_equal_p (TREE_OPERAND (arg0, 0),
TREE_OPERAND (arg1, 0), 0)
&& TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
&& TREE_CODE (TREE_OPERAND (arg1, 1)) == INTEGER_CST)
{
tree mask0 = TREE_OPERAND (arg0, 1);
tree mask1 = TREE_OPERAND (arg1, 1);
tree tem = fold (build1 (BIT_NOT_EXPR, type, mask0));
if (operand_equal_p (tem, mask1, 0)
&& integer_pow2p (fold (build (PLUS_EXPR, type,
mask1, integer_one_node))))
{
tem = fold (build (BIT_XOR_EXPR, type,
TREE_OPERAND (arg0, 0), mask1));
return fold (build (MINUS_EXPR, type, tem, mask1));
}
}
}
/* See if ARG1 is zero and X - ARG1 reduces to X. */