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tree-cfg.c (find_taken_edge): Statically compute the truth value of a predicate comparing an SSA_NAME to itself. 

* tree-cfg.c (find_taken_edge): Statically compute the truth
	value of a predicate comparing an SSA_NAME to itself.

From-SVN: r84561
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Diego Novillo 2004-07-12 15:38:25 +00:00 committed by Diego Novillo
parent 938bf7475d
commit 255cd731f4
2 changed files with 26 additions and 3 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2004-07-12 Diego Novillo <dnovillo@redhat.com>
* tree-cfg.c (find_taken_edge): Statically compute the truth
value of a predicate comparing an SSA_NAME to itself.
2004-07-12 Roger Sayle <roger@eyesopen.com>
* config/rs6000/rs6000.c (rs6000_rtx_costs): Indicate that the

24
gcc/tree-cfg.c
View File

@ -1991,9 +1991,9 @@ cleanup_control_expr_graph (basic_block bb, block_stmt_iterator bsi)
}
/* Given a control block BB and a constant value VAL, return the edge that
will be taken out of the block. If VAL does not match a unique edge,
NULL is returned. */
/* Given a control block BB and a predicate VAL, return the edge that
will be taken out of the block. If VAL does not match a unique
edge, NULL is returned. */
edge
find_taken_edge (basic_block bb, tree val)
@ -2007,6 +2007,24 @@ find_taken_edge (basic_block bb, tree val)
abort ();
#endif
/* If VAL is a predicate of the form N RELOP N, where N is an
SSA_NAME, we can always determine its truth value (except when
doing floating point comparisons that may involve NaNs). */
if (val
&& TREE_CODE_CLASS (TREE_CODE (val)) == '<'
&& TREE_OPERAND (val, 0) == TREE_OPERAND (val, 1)
&& TREE_CODE (TREE_OPERAND (val, 0)) == SSA_NAME
&& (TREE_CODE (TREE_TYPE (TREE_OPERAND (val, 0))) != REAL_TYPE
|| !HONOR_NANS (TYPE_MODE (TREE_TYPE (TREE_OPERAND (val, 0))))))
{
enum tree_code code = TREE_CODE (val);
if (code == EQ_EXPR || code == LE_EXPR || code == GE_EXPR)
val = boolean_true_node;
else if (code == LT_EXPR || code == GT_EXPR || code == NE_EXPR)
val = boolean_false_node;
}
/* If VAL is not a constant, we can't determine which edge might
be taken. */
if (val == NULL || !really_constant_p (val))