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;
