middle-end: update vector loop upper bounds when early break vect [PR113734]

When doing early break vectorization we should treat the final iteration as
possibly being partial.  This so that when we calculate the vector loop upper
bounds we take into account that final iteration could have done some work.

The attached testcase shows that if we don't then cunroll may unroll the loop an
if the upper bound is wrong we lose a vector iteration.

This is similar to how we adjust the scalar loop bounds for the PEELED case.

gcc/ChangeLog:

	PR tree-optimization/113734
	* tree-vect-loop.cc (vect_transform_loop): Treat the final iteration of
	an early break loop as partial.

gcc/testsuite/ChangeLog:

	PR tree-optimization/113734
	* gcc.dg/vect/vect-early-break_117-pr113734.c: New test.

diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_117-pr113734.c b/gcc/testsuite/gcc.dg/vect/vect-early-break_117-pr113734.c
new file mode 100644 (file)
index 0000000..36ae094
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_117-pr113734.c
@@ -0,0 +1,37 @@
+/* { dg-add-options vect_early_break } */
+/* { dg-require-effective-target vect_early_break_hw } */
+/* { dg-require-effective-target vect_int } */
+/* { dg-additional-options "-O3" } */
+
+/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
+
+#include "tree-vect.h"
+
+#define N 306
+#define NEEDLE 136
+
+int table[N];
+
+__attribute__ ((noipa))
+int foo (int i, unsigned short parse_tables_n)
+{
+  parse_tables_n >>= 9;
+  parse_tables_n += 11;
+  while (i < N && parse_tables_n--)
+    table[i++] = 0;
+
+  return table[NEEDLE];
+}
+
+int main ()
+{
+  check_vect ();
+
+  for (int j = 0; j < N; j++)
+    table[j] = -1;
+
+  if (foo (0, 0xFFFF) != 0)
+    __builtin_abort ();
+
+  return 0;
+}

diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index 04f4b5b6b2fa76824c75b4d41df48ef995ad17a2..367077965fd9a166f605f6b933ee731b3586d1c2 100644 (file)
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -12174,7 +12174,8 @@ vect_transform_loop (loop_vec_info loop_vinfo, gimple *loop_vectorized_call)
   /* True if the final iteration might not handle a full vector's
      worth of scalar iterations.  */
   bool final_iter_may_be_partial
-    = LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo);
+    = LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo)
+      || LOOP_VINFO_EARLY_BREAKS (loop_vinfo);
   /* The minimum number of iterations performed by the epilogue.  This
      is 1 when peeling for gaps because we always need a final scalar
      iteration.  */