On 19/11/14 16:39, Marek Polacek wrote:
On Wed, Nov 19, 2014 at 04:32:43PM +0000, Andrew Stubbs wrote:
+ if (warning_at (gimple_location (elt->stmt),
+ OPT_Waggressive_loop_optimizations,
+ "Loop exit may only be reached after undefined
behaviour."))
Warnings should start with a lowercase and should be without
a fullstop at the end.
Fixed, and I spotted a britishism too.
Andrew
2014-11-19 Andrew Stubbs <a...@codesourcery.com>
gcc/
* tree-ssa-loop-niter.c (maybe_lower_iteration_bound): Warn if a loop
condition would be removed due to undefined behaviour.
gcc/testsuite/
* gcc.dg/undefined-loop-1.c: New file.
* gcc.dg/undefined-loop-2.c: New file.
---
gcc/testsuite/gcc.dg/undefined-loop-1.c | 18 ++++++++++++
gcc/testsuite/gcc.dg/undefined-loop-2.c | 22 +++++++++++++++
gcc/tree-ssa-loop-niter.c | 46 +++++++++++++++++++++++++++++++
3 files changed, 86 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/undefined-loop-1.c
create mode 100644 gcc/testsuite/gcc.dg/undefined-loop-2.c
diff --git a/gcc/testsuite/gcc.dg/undefined-loop-1.c b/gcc/testsuite/gcc.dg/undefined-loop-1.c
new file mode 100644
index 0000000..80260cc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/undefined-loop-1.c
@@ -0,0 +1,18 @@
+/* Check that loops whose final iteration is undefined are detected. */
+/* { dg-do compile } */
+/* { dg-options "-O2 -Waggressive-loop-optimizations" } */
+
+void doSomething(char);
+
+char array[5];
+
+void
+foo (void)
+{
+ int i;
+ for (i = 0;
+ array[i] /* { dg-message "note: possible undefined statement is here" } */
+ && i < 5; /* { dg-warning "loop exit may only be reached after undefined behavior" } */
+ i++)
+ doSomething(array[i]);
+}
diff --git a/gcc/testsuite/gcc.dg/undefined-loop-2.c b/gcc/testsuite/gcc.dg/undefined-loop-2.c
new file mode 100644
index 0000000..dbea62c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/undefined-loop-2.c
@@ -0,0 +1,22 @@
+/* Check that loops whose final iteration is undefined are detected. */
+/* { dg-do compile } */
+/* { dg-options "-O2 -Waggressive-loop-optimizations" } */
+
+void doSomething(char);
+
+char array1[5];
+char array2[5];
+
+void
+foo (int p)
+{
+ int i;
+ for (i=0;
+ (p
+ ? array1[i] /* { dg-message "note: possible undefined statement is here" } */
+ : array2[i]) /* { dg-message "note: possible undefined statement is here" } */
+ && i < 5 /* { dg-warning "loop exit may only be reached after undefined behavior" } */
+ && i < 100; /* { dg-warning "loop exit may only be reached after undefined behavior" } */
+ i++)
+ doSomething(array1[i]);
+}
diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
index fd32d28..0365505 100644
--- a/gcc/tree-ssa-loop-niter.c
+++ b/gcc/tree-ssa-loop-niter.c
@@ -3289,6 +3289,7 @@ maybe_lower_iteration_bound (struct loop *loop)
struct nb_iter_bound *elt;
bool found_exit = false;
vec<basic_block> queue = vNULL;
+ vec<gimple> problem_stmts = vNULL;
bitmap visited;
/* Collect all statements with interesting (i.e. lower than
@@ -3334,6 +3335,7 @@ maybe_lower_iteration_bound (struct loop *loop)
if (not_executed_last_iteration->contains (stmt))
{
stmt_found = true;
+ problem_stmts.safe_push (stmt);
break;
}
if (gimple_has_side_effects (stmt))
@@ -3377,9 +3379,53 @@ maybe_lower_iteration_bound (struct loop *loop)
"undefined statement must be executed at the last iteration.\n");
record_niter_bound (loop, loop->nb_iterations_upper_bound - 1,
false, true);
+
+ if (OPT_Waggressive_loop_optimizations)
+ {
+ bool exit_warned = false;
+ for (elt = loop->bounds; elt; elt = elt->next)
+ {
+ if (elt->is_exit
+ && wi::gtu_p (elt->bound, loop->nb_iterations_upper_bound))
+ {
+ basic_block bb = gimple_bb (elt->stmt);
+ edge exit_edge = EDGE_SUCC (bb, 0);
+ struct tree_niter_desc niter;
+
+ if (!loop_exit_edge_p (loop, exit_edge))
+ exit_edge = EDGE_SUCC (bb, 1);
+
+ if(number_of_iterations_exit (loop, exit_edge,
+ &niter, false, false)
+ && integer_onep (niter.assumptions)
+ && integer_zerop (niter.may_be_zero)
+ && niter.niter
+ && TREE_CODE (niter.niter) == INTEGER_CST
+ && wi::ltu_p (loop->nb_iterations_upper_bound,
+ wi::to_widest (niter.niter)))
+ {
+ if (warning_at (gimple_location (elt->stmt),
+ OPT_Waggressive_loop_optimizations,
+ "loop exit may only be reached after undefined behavior"))
+ exit_warned = true;
+ }
+ }
+ }
+
+ if (exit_warned && problem_stmts != vNULL)
+ {
+ gimple stmt;
+ int index;
+ FOR_EACH_VEC_ELT (problem_stmts, index, stmt)
+ inform (gimple_location (stmt),
+ "possible undefined statement is here");
+ }
+ }
}
+
BITMAP_FREE (visited);
queue.release ();
+ problem_stmts.release ();
delete not_executed_last_iteration;
}
