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improve multiple_of_p
- From: Richard Henderson <rth at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Sat, 18 Dec 2004 11:06:54 -0800
- Subject: improve multiple_of_p
A couple of months ago I changed round_up and round_down to
use BIT_AND_EXPR instead of FLOOR_DIV_EXPR and CEIL_DIV_EXPR.
When the current result of round_up is passed to round_up
again, since multiple_of_p doesn't understand BIT_AND_EXPR
we get a second, unnecessary, set of operations.
r~
* fold-const.c (multiple_of_p): Handle BIT_AND_EXPR when
BOTTOM is a power of two.
Index: fold-const.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/fold-const.c,v
retrieving revision 1.485
diff -c -p -d -r1.485 fold-const.c
*** fold-const.c 14 Dec 2004 17:59:36 -0000 1.485
--- fold-const.c 18 Dec 2004 19:02:34 -0000
*************** multiple_of_p (tree type, tree top, tree
*** 9541,9546 ****
--- 9541,9553 ----
switch (TREE_CODE (top))
{
+ case BIT_AND_EXPR:
+ /* Bitwise and provides a power of two multiple. If the mask is
+ a multiple of BOTTOM then TOP is a multiple of BOTTOM. */
+ if (!integer_pow2p (bottom))
+ return 0;
+ /* FALLTHRU */
+
case MULT_EXPR:
return (multiple_of_p (type, TREE_OPERAND (top, 0), bottom)
|| multiple_of_p (type, TREE_OPERAND (top, 1), bottom));