Hi,
On Fri, 9 Dec 2016, Richard Biener wrote:
> On December 9, 2016 4:29:04 PM GMT+01:00, Michael Matz <m...@suse.de> wrote:
> >Hi,
> >
> >if the induction variable on which we want to partition the loop
> >iterations for loop splitting might overflow we would either need
> >runtime
> >tests checking if an overflow in fact does happen, or we can simply not
> >
> >split loops on such ones. I chose the latter.
> >
> >Fixes the testcase, and regstrapped without regressions on x86-64-linux
> >
> >(all languages+Ada). Okay for trunk?
>
> OK
Actually there came another report in the same bug, which has a different
but related cause. In the testcase the potential split-point is
if (outer >= inner)
where the final value of 'inner' is known constant in the _outer_ loop.
But of course we have to consider the actual place of the use: the
comparison statement which is inside the inner loop, not merely in the
outer loop. Fixed with the amended patch.
Regstrapping on x86-64-linux in progress (all langs+ada), but I know that
it fixes both testcases and doesn't regress in gcc.dg. Okay for trunk if
regstrapping succeeds?
Ciao,
Michael.
PR tree-optimization/78725
* tree-ssa-loop-split.c (split_at_bb_p): Check for overflow and
at correct use point.
testsuite/
PR tree-optimization/78725
* gcc.dg/pr78725.c: New test.
* gcc.dg/pr78725-2.c: New test.
diff --git a/gcc/testsuite/gcc.dg/pr78725-2.c b/gcc/testsuite/gcc.dg/pr78725-2.c
new file mode 100644
index 0000000..9de489e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr78725-2.c
@@ -0,0 +1,19 @@
+/* { dg-do run } */
+/* { dg-options "-O3 -fsplit-loops" } */
+
+int a, b, c;
+
+int main ()
+{
+ int d;
+ for (; c < 1; c++)
+ for (d = 0; d < 3; d++)
+ for (b = 0; b < 1; b++)
+ if (c >= d)
+ a = 1;
+
+ if (a != 1)
+ __builtin_abort ();
+
+ return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/pr78725.c b/gcc/testsuite/gcc.dg/pr78725.c
new file mode 100644
index 0000000..ed95790
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr78725.c
@@ -0,0 +1,19 @@
+/* { dg-do run } */
+/* { dg-options "-O3 -fsplit-loops" } */
+
+int fn1 (int b, int c)
+{
+ return c < 0 || c > 31 ? 0 : b >> c;
+}
+
+unsigned char d = 255;
+int e, f;
+
+int main ()
+{
+ for (; f < 2; f++)
+ e = fn1 (1, d++);
+ if (e != 1)
+ __builtin_abort ();
+ return 0;
+}
diff --git a/gcc/tree-ssa-loop-split.c b/gcc/tree-ssa-loop-split.c
index dac68e6..84c0627 100644
--- a/gcc/tree-ssa-loop-split.c
+++ b/gcc/tree-ssa-loop-split.c
@@ -102,10 +102,11 @@ split_at_bb_p (struct loop *loop, basic_block bb, tree
*border, affine_iv *iv)
tree op0 = gimple_cond_lhs (stmt);
tree op1 = gimple_cond_rhs (stmt);
+ struct loop *useloop = loop_containing_stmt (stmt);
- if (!simple_iv (loop, loop, op0, iv, false))
+ if (!simple_iv (loop, useloop, op0, iv, false))
return NULL_TREE;
- if (!simple_iv (loop, loop, op1, &iv2, false))
+ if (!simple_iv (loop, useloop, op1, &iv2, false))
return NULL_TREE;
/* Make it so that the first argument of the condition is
@@ -122,6 +123,8 @@ split_at_bb_p (struct loop *loop, basic_block bb, tree
*border, affine_iv *iv)
return NULL_TREE;
if (!integer_zerop (iv2.step))
return NULL_TREE;
+ if (!iv->no_overflow)
+ return NULL_TREE;
if (dump_file && (dump_flags & TDF_DETAILS))
{
