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openSUSE:12.2
gcc41
nov495844.diff
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File nov495844.diff of Package gcc41
2009-04-23 Richard Guenther <rguenther@suse.de> * tree-ssa-loop-ivopts.c (iv_expression_expensive_p): New function. (may_eliminate_iv): Use it. * gcc.dg/tree-ssa/bnc495844.c: New testcase. Index: gcc/tree-ssa-loop-ivopts.c =================================================================== *** gcc/tree-ssa-loop-ivopts.c (revision 146521) --- gcc/tree-ssa-loop-ivopts.c (working copy) *************** iv_elimination_compare (struct ivopts_da *** 3996,4001 **** --- 3996,4045 ---- return (exit->flags & EDGE_TRUE_VALUE ? EQ_EXPR : NE_EXPR); } + /* Returns true if the expression EXPR is considered to be too expensive + for induction variable elimination. */ + + static bool + iv_expression_expensive_p (tree expr) + { + enum tree_code code; + + if (is_gimple_val (expr)) + return false; + + code = TREE_CODE (expr); + if (code == TRUNC_DIV_EXPR + || code == CEIL_DIV_EXPR + || code == FLOOR_DIV_EXPR + || code == ROUND_DIV_EXPR + || code == TRUNC_MOD_EXPR + || code == CEIL_MOD_EXPR + || code == FLOOR_MOD_EXPR + || code == ROUND_MOD_EXPR + || code == EXACT_DIV_EXPR) + { + /* Division by power of two is usually cheap, so we allow it. + Forbid anything else. */ + if (!integer_pow2p (TREE_OPERAND (expr, 1))) + return true; + } + + switch (TREE_CODE_CLASS (code)) + { + case tcc_binary: + case tcc_comparison: + if (iv_expression_expensive_p (TREE_OPERAND (expr, 1))) + return true; + + /* Fallthru. */ + case tcc_unary: + return iv_expression_expensive_p (TREE_OPERAND (expr, 0)); + + default: + return true; + } + } + /* Check whether it is possible to express the condition in USE by comparison of candidate CAND. If so, store the value compared with to BOUND. */ *************** may_eliminate_iv (struct ivopts_data *da *** 4053,4058 **** --- 4097,4106 ---- return false; *bound = cand_value_at (loop, cand, use->stmt, nit); + /* It is unlikely that computing the number of iterations using division + would be more profitable than keeping the original induction variable. */ + if (iv_expression_expensive_p (*bound)) + return false; return true; } Index: gcc/testsuite/gcc.dg/tree-ssa/bnc495844.c =================================================================== *** gcc/testsuite/gcc.dg/tree-ssa/bnc495844.c (revision 0) --- gcc/testsuite/gcc.dg/tree-ssa/bnc495844.c (revision 0) *************** *** 0 **** --- 1,14 ---- + /* { dg-do compile } */ + /* { dg-options "-O2 -fdump-tree-optimized" } */ + + unsigned long + foo (const char *d, int len, char *dict, unsigned long o) + { + int point_me; + for (point_me = 0; point_me < len; point_me += 3) + o += dict[point_me]; + return o; + } + + /* { dg-final { scan-tree-dump-not "/\\\[fl\\\] 3" "optimized" } } */ + /* { dg-final { cleanup-tree-dump "optimized" } } */
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