We fail to fold round_up generated expressions during size expression folding.
Fixed as follows, bootstrapped and tested on x86_64-unknwon-linux-gnu, applied to trunk. Richard. 2012-03-13 Richard Guenther <rguent...@suse.de> PR middle-end/52134 * fold-const.c (fold_binary_loc): Fold (X * Y) & -(1 << CST) to X * Y if Y is a constant multiple of 1 << CST. * gcc.dg/pr52134.c: New testcase. Index: gcc/fold-const.c =================================================================== *** gcc/fold-const.c (revision 185322) --- gcc/fold-const.c (working copy) *************** fold_binary_loc (location_t loc, *** 11398,11403 **** --- 11401,11420 ---- fold_convert_loc (loc, type, arg0)); } + /* Fold (X * Y) & -(1 << CST) to X * Y if Y is a constant + multiple of 1 << CST. */ + if (TREE_CODE (arg1) == INTEGER_CST) + { + double_int cst1 = tree_to_double_int (arg1); + double_int ncst1 = double_int_ext (double_int_neg (cst1), + TYPE_PRECISION (TREE_TYPE (arg1)), + TYPE_UNSIGNED (TREE_TYPE (arg1))); + if (double_int_equal_p (double_int_and (cst1, ncst1), ncst1) + && multiple_of_p (type, arg0, + double_int_to_tree (TREE_TYPE (arg1), ncst1))) + return fold_convert_loc (loc, type, arg0); + } + /* For constants M and N, if M == (1LL << cst) - 1 && (N & M) == M, ((A & N) + B) & M -> (A + B) & M Similarly if (N & M) == 0, Index: gcc/testsuite/gcc.dg/pr52134.c =================================================================== *** gcc/testsuite/gcc.dg/pr52134.c (revision 0) --- gcc/testsuite/gcc.dg/pr52134.c (revision 0) *************** *** 0 **** --- 1,14 ---- + /* { dg-do compile } */ + /* { dg-options "-fdump-tree-original" } */ + + unsigned f(unsigned t) + { + return (t*4)&-4; + } + int f1(int t) + { + return (t*4)&-4; + } + + /* { dg-final { scan-tree-dump-not "\\\&" "original" } } */ + /* { dg-final { cleanup-tree-dump "original" } } */