Hi,
Previous patch removed warning message on loops whose counter might overflow,
while this patch adds it back. Reason is it's always good to have a warning
message indicating missed loop optimizations. Also warning message itself is
slightly changed.
There will be following patch which removes -funsafe-loop-optimizations.
Bootstrap and test on x86_64. Is it OK?
Thanks,
bin
2016-07-20 Bin Cheng <bin.ch...@arm.com>
* tree-ssa-loop-niter.h (number_of_iterations_exit_assumptions): New
Parameter.
* tree-ssa-loop-niter.c (number_of_iterations_exit_assumptions): New
Parameter.
(number_of_iterations_exit): Warn missed loop optimization for
possible infinite loops.
gcc/testsuite/ChangeLog
2016-07-20 Bin Cheng <bin.ch...@arm.com>
* gcc.dg/tree-ssa/pr19210-1.c: Refine test strings.
* gcc.dg/tree-ssa/pr19210-2.c: Delete.diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr19210-1.c
b/gcc/testsuite/gcc.dg/tree-ssa/pr19210-1.c
index 906132c..3c8ee06 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/pr19210-1.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr19210-1.c
@@ -6,10 +6,10 @@ void
f (unsigned n)
{
unsigned k;
- for(k = 0;k <= n;k++) /* { dg-warning "cannot optimize.*infinite loops" } */
+ for(k = 0;k <= n;k++) /* { dg-warning "missed loop optimization.*overflow" }
*/
g();
- for(k = 0;k <= n;k += 4) /* { dg-warning "cannot optimize.*overflow" } */
+ for(k = 0;k <= n;k += 4) /* { dg-warning "missed loop
optimization.*overflow" } */
g();
/* We used to get warning for this loop. However, since then # of iterations
@@ -21,9 +21,9 @@ f (unsigned n)
g();
/* So we need the following loop, instead. */
- for(k = 4;k <= n;k += 5) /* { dg-warning "cannot optimize.*overflow" } */
+ for(k = 4;k <= n;k += 5) /* { dg-warning "missed loop
optimization.*overflow" } */
g();
- for(k = 15;k >= n;k--) /* { dg-warning "cannot optimize.*infinite" } */
+ for(k = 15;k >= n;k--) /* { dg-warning "missed loop optimization.*overflow"
} */
g();
}
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr19210-2.c
b/gcc/testsuite/gcc.dg/tree-ssa/pr19210-2.c
deleted file mode 100644
index 9116e97..0000000
--- a/gcc/testsuite/gcc.dg/tree-ssa/pr19210-2.c
+++ /dev/null
@@ -1,29 +0,0 @@
-/* { dg-do compile } */
-/* { dg-options "-O2 -funsafe-loop-optimizations -Wunsafe-loop-optimizations"
} */
-extern void g(void);
-
-void
-f (unsigned n)
-{
- unsigned k;
- for(k = 0;k <= n;k++) /* { dg-warning "assuming.*not infinite" } */
- g();
-
- for(k = 5;k <= n;k += 4) /* { dg-warning "assuming.*not overflow" } */
- g();
-
- /* We used to get warning for this loop. However, since then # of iterations
- analysis improved, and we can now prove that this loop does not verflow.
- This is because the only case when it would overflow is if n = ~0 (since
- ~0 is divisible by 5), and this cannot be the case, since when we got
- here, the previous loop exited, thus there exists k > n. */
- for(k = 5;k <= n;k += 5)
- g();
-
- for(k = 4;k <= n;k += 5) /* { dg-warning "assuming.*not overflow" } */
- g();
-
- for(k = 15;k >= n;k--) /* { dg-warning "assuming.*not infinite" } */
- g();
-
-}
diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
index d96c03b..48947f0 100644
--- a/gcc/tree-ssa-loop-niter.c
+++ b/gcc/tree-ssa-loop-niter.c
@@ -2181,12 +2181,13 @@ loop_only_exit_p (const struct loop *loop, const_edge
exit)
in comments at struct tree_niter_desc declaration), false otherwise.
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).
- */
+ If AT_STMT is not NULL, this function stores LOOP's condition statement in
+ it when returning true. */
bool
number_of_iterations_exit_assumptions (struct loop *loop, edge exit,
struct tree_niter_desc *niter,
- bool every_iteration)
+ gcond **at_stmt, bool every_iteration)
{
gimple *last;
gcond *stmt;
@@ -2303,6 +2304,9 @@ number_of_iterations_exit_assumptions (struct loop *loop,
edge exit,
if (TREE_CODE (niter->niter) == INTEGER_CST)
niter->max = wi::to_widest (niter->niter);
+ if (at_stmt)
+ *at_stmt = stmt;
+
return (!integer_zerop (niter->assumptions));
}
@@ -2312,13 +2316,27 @@ number_of_iterations_exit_assumptions (struct loop
*loop, edge exit,
bool
number_of_iterations_exit (struct loop *loop, edge exit,
struct tree_niter_desc *niter,
- bool, bool every_iteration)
+ bool warn, bool every_iteration)
{
+ gcond *stmt;
if (!number_of_iterations_exit_assumptions (loop, exit, niter,
- every_iteration))
+ &stmt, every_iteration))
return false;
- return (integer_nonzerop (niter->assumptions));
+ if (integer_nonzerop (niter->assumptions))
+ return true;
+
+ if (warn)
+ {
+ const char *wording;
+ location_t loc = gimple_location (stmt);
+
+ wording = N_("missed loop optimization, the loop counter may overflow");
+ warning_at ((LOCATION_LINE (loc) > 0) ? loc : input_location,
+ OPT_Wunsafe_loop_optimizations, "%s", gettext (wording));
+ }
+
+ return false;
}
/* Try to determine the number of iterations of LOOP. If we succeed,
diff --git a/gcc/tree-ssa-loop-niter.h b/gcc/tree-ssa-loop-niter.h
index 1aea580..e46b829 100644
--- a/gcc/tree-ssa-loop-niter.h
+++ b/gcc/tree-ssa-loop-niter.h
@@ -29,7 +29,7 @@ extern bool number_of_iterations_exit (struct loop *, edge,
bool every_iteration = true);
extern bool number_of_iterations_exit_assumptions (struct loop *, edge,
struct tree_niter_desc *,
- bool = true);
+ gcond **, bool = true);
extern tree find_loop_niter (struct loop *, edge *);
extern bool finite_loop_p (struct loop *);
extern tree loop_niter_by_eval (struct loop *, edge);
