diff options
Diffstat (limited to 'gcc/tree-ssa-loop-ivopts.c')
| -rw-r--r-- | gcc/tree-ssa-loop-ivopts.c | 41 |
1 files changed, 27 insertions, 14 deletions
diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c index 41c3794..ce5c05c 100644 --- a/gcc/tree-ssa-loop-ivopts.c +++ b/gcc/tree-ssa-loop-ivopts.c @@ -3745,13 +3745,12 @@ may_eliminate_iv (struct ivopts_data *data, tree nit, period; struct loop *loop = data->current_loop; aff_tree bnd; - double_int period_value, max_niter; if (TREE_CODE (cand->iv->step) != INTEGER_CST) return false; - /* For now works only for exits that dominate the loop latch. TODO -- extend - for other conditions inside loop body. */ + /* For now works only for exits that dominate the loop latch. + TODO: extend to other conditions inside loop body. */ ex_bb = bb_for_stmt (use->stmt); if (use->stmt != last_stmt (ex_bb) || TREE_CODE (use->stmt) != COND_EXPR) @@ -3769,19 +3768,33 @@ may_eliminate_iv (struct ivopts_data *data, if (!nit) return false; - /* Determine whether we may use the variable to test whether niter iterations - elapsed. This is the case iff the period of the induction variable is - greater than the number of iterations. */ + /* Determine whether we can use the variable to test the exit condition. + This is the case iff the period of the induction variable is greater + than the number of iterations for which the exit condition is true. */ period = iv_period (cand->iv); - if (!period) - return false; - /* Compare the period with the estimate on the number of iterations of the - loop. */ - if (!estimated_loop_iterations (loop, true, &max_niter)) - return false; - period_value = tree_to_double_int (period); - if (double_int_ucmp (period_value, max_niter) <= 0) + /* If the number of iterations is constant, compare against it directly. */ + if (TREE_CODE (nit) == INTEGER_CST) + { + if (!tree_int_cst_lt (nit, period)) + return false; + } + + /* If not, and if this is the only possible exit of the loop, see whether + we can get a conservative estimate on the number of iterations of the + entire loop and compare against that instead. */ + else if (loop_only_exit_p (loop, exit)) + { + double_int period_value, max_niter; + if (!estimated_loop_iterations (loop, true, &max_niter)) + return false; + period_value = tree_to_double_int (period); + if (double_int_ucmp (max_niter, period_value) >= 0) + return false; + } + + /* Otherwise, punt. */ + else return false; cand_value_at (loop, cand, use->stmt, nit, &bnd); |