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(fold, case GT_EXPR): Simplify X < (1 << Y) into X >> Y == 0. 

From-SVN: r6999
This commit is contained in:
Richard Kenner 1994-04-08 18:18:08 -04:00
parent 69887ad921
commit e92d30482e
1 changed files with 24 additions and 0 deletions
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24
gcc/fold-const.c
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@ -4517,6 +4517,30 @@ fold (expr)
return build (code == EQ_EXPR ? NE_EXPR : EQ_EXPR, type,
arg0, integer_zero_node);
/* If X is unsigned, convert X < (1 << Y) into X >> Y == 0
and similarly for <= into !=. */
if ((code == LT_EXPR || code == GE_EXPR)
&& TREE_UNSIGNED (TREE_TYPE (arg0))
&& TREE_CODE (arg1) == LSHIFT_EXPR
&& integer_onep (TREE_OPERAND (arg1, 0)))
return build (code == LT_EXPR ? EQ_EXPR : NE_EXPR, type,
build (RSHIFT_EXPR, TREE_TYPE (arg0), arg0,
TREE_OPERAND (arg1, 1)),
convert (TREE_TYPE (arg0), integer_zero_node));
else if ((code == LT_EXPR || code == GE_EXPR)
&& TREE_UNSIGNED (TREE_TYPE (arg0))
&& (TREE_CODE (arg1) == NOP_EXPR
|| TREE_CODE (arg1) == CONVERT_EXPR)
&& TREE_CODE (TREE_OPERAND (arg1, 0)) == LSHIFT_EXPR
&& integer_onep (TREE_OPERAND (TREE_OPERAND (arg1, 0), 0)))
return
build (code == LT_EXPR ? EQ_EXPR : NE_EXPR, type,
convert (TREE_TYPE (arg0),
build (RSHIFT_EXPR, TREE_TYPE (arg0), arg0,
TREE_OPERAND (TREE_OPERAND (arg1, 0), 1))),
convert (TREE_TYPE (arg0), integer_zero_node));
/* Simplify comparison of something with itself. (For IEEE
floating-point, we can only do some of these simplifications.) */
if (operand_equal_p (arg0, arg1, 0))