Hi, this is first patch of change of tree-ssa-loop-niter to consider bounds that are not in block dominating latch. This patch makes them to be recorded and they are not used. I plan to followup with:
1) patch to add simple shortest path walk at the end of estimate_numbers_of_iterations_loop determining bound of i.e. int a[10]; int b[10]; for (i=0;i<n;i++) if (t()) q(a[i]); else q(a[i]); 2) make complette loop unrolling to kill all statements known to not be executed in the last iteration by __builtin_unreachable to silence part of -Warray-bounds warnings currently breaking bootstrap with -O3 3) make duplicate_loop_to_header_edge in peeling mode to do the same silencing the rest of warnings 4) make branch prediction code to drop the prediction on exits not dominating latch. Bootstrapped/regtested x86_64-linux, OK? * tree-ssa-loop-niter.c (number_of_iterations_exit): New parameter EVERY_ITERATION with implicit value of true. (record_estimate): Check dominance relationship of the basic block we are estimating on instead of relying on UPPER to be false. (struct ilb_data): Drop RELIABLE. (idx_infer_loop_bounds): Update. (infer_loop_bounds_from_ref): Drop parameter RELIABLE. (infer_loop_bounds_from_array): Drop parameter RELIABLE. (infer_loop_bounds_from_undefined): Update comments and handling of RELIABLE. (estimate_numbers_of_iterations_loop): Record all bounds. Index: tree-ssa-loop-niter.c =================================================================== --- tree-ssa-loop-niter.c (revision 192986) +++ tree-ssa-loop-niter.c (working copy) @@ -1793,12 +1793,15 @@ loop_only_exit_p (const struct loop *loo meaning described in comments at struct tree_niter_desc declaration), false otherwise. If WARN is true and -Wunsafe-loop-optimizations was given, warn if the optimizer is going to use - potentially unsafe assumptions. */ + potentially unsafe assumptions. + When EVERY_ITERATION is true, only tests that are known to be executed + every iteration are considered (i.e. only test that alone bounds the loop). + */ bool number_of_iterations_exit (struct loop *loop, edge exit, struct tree_niter_desc *niter, - bool warn) + bool warn, bool every_iteration) { gimple stmt; tree type; @@ -1806,7 +1809,8 @@ number_of_iterations_exit (struct loop * enum tree_code code; affine_iv iv0, iv1; - if (!dominated_by_p (CDI_DOMINATORS, loop->latch, exit->src)) + if (every_iteration + && !dominated_by_p (CDI_DOMINATORS, loop->latch, exit->src)) return false; niter->assumptions = boolean_false_node; @@ -2568,6 +2572,11 @@ record_estimate (struct loop *loop, tree loop->bounds = elt; } + /* If statement is executed on every path to the loop latch, we can directly + infer the upper bound on the # of iterations of the loop. */ + if (!dominated_by_p (CDI_DOMINATORS, loop->latch, gimple_bb (at_stmt))) + return; + /* Update the number of iteration estimates according to the bound. If at_stmt is an exit then the loop latch is executed at most BOUND times, otherwise it can be executed BOUND + 1 times. We will lower the estimate @@ -2651,7 +2660,6 @@ struct ilb_data { struct loop *loop; gimple stmt; - bool reliable; }; static bool @@ -2660,7 +2668,7 @@ idx_infer_loop_bounds (tree base, tree * struct ilb_data *data = (struct ilb_data *) dta; tree ev, init, step; tree low, high, type, next; - bool sign, upper = data->reliable, at_end = false; + bool sign, upper = true, at_end = false; struct loop *loop = data->loop; if (TREE_CODE (base) != ARRAY_REF) @@ -2737,14 +2745,12 @@ idx_infer_loop_bounds (tree base, tree * STMT is guaranteed to be executed in every iteration of LOOP.*/ static void -infer_loop_bounds_from_ref (struct loop *loop, gimple stmt, tree ref, - bool reliable) +infer_loop_bounds_from_ref (struct loop *loop, gimple stmt, tree ref) { struct ilb_data data; data.loop = loop; data.stmt = stmt; - data.reliable = reliable; for_each_index (&ref, idx_infer_loop_bounds, &data); } @@ -2753,7 +2759,7 @@ infer_loop_bounds_from_ref (struct loop executed in every iteration of LOOP. */ static void -infer_loop_bounds_from_array (struct loop *loop, gimple stmt, bool reliable) +infer_loop_bounds_from_array (struct loop *loop, gimple stmt) { if (is_gimple_assign (stmt)) { @@ -2763,10 +2769,10 @@ infer_loop_bounds_from_array (struct loo /* For each memory access, analyze its access function and record a bound on the loop iteration domain. */ if (REFERENCE_CLASS_P (op0)) - infer_loop_bounds_from_ref (loop, stmt, op0, reliable); + infer_loop_bounds_from_ref (loop, stmt, op0); if (REFERENCE_CLASS_P (op1)) - infer_loop_bounds_from_ref (loop, stmt, op1, reliable); + infer_loop_bounds_from_ref (loop, stmt, op1); } else if (is_gimple_call (stmt)) { @@ -2775,13 +2781,13 @@ infer_loop_bounds_from_array (struct loo lhs = gimple_call_lhs (stmt); if (lhs && REFERENCE_CLASS_P (lhs)) - infer_loop_bounds_from_ref (loop, stmt, lhs, reliable); + infer_loop_bounds_from_ref (loop, stmt, lhs); for (i = 0; i < n; i++) { arg = gimple_call_arg (stmt, i); if (REFERENCE_CLASS_P (arg)) - infer_loop_bounds_from_ref (loop, stmt, arg, reliable); + infer_loop_bounds_from_ref (loop, stmt, arg); } } } @@ -2910,14 +2916,15 @@ infer_loop_bounds_from_undefined (struct /* If BB is not executed in each iteration of the loop, we cannot use the operations in it to infer reliable upper bound on the - # of iterations of the loop. However, we can use it as a guess. */ + # of iterations of the loop. However, we can use it as a guess. + Reliable guesses come only from array bounds. */ reliable = dominated_by_p (CDI_DOMINATORS, loop->latch, bb); for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi)) { gimple stmt = gsi_stmt (bsi); - infer_loop_bounds_from_array (loop, stmt, reliable); + infer_loop_bounds_from_array (loop, stmt); if (reliable) { @@ -3078,7 +3085,7 @@ estimate_numbers_of_iterations_loop (str likely_exit = single_likely_exit (loop); FOR_EACH_VEC_ELT (edge, exits, i, ex) { - if (!number_of_iterations_exit (loop, ex, &niter_desc, false)) + if (!number_of_iterations_exit (loop, ex, &niter_desc, false, false)) continue; niter = niter_desc.niter;