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tree-optimization/105219 - bogus max iters for vectorized epilogue

Message ID 20220427120950.4A74F13A39@imap2.suse-dmz.suse.de
State New
Headers
Series tree-optimization/105219 - bogus max iters for vectorized epilogue |

Commit Message

Richard Biener April 27, 2022, 12:09 p.m. UTC 
  The following makes sure to take into account prologue peeling
when trying to narrow down the maximum number of iterations
computed for the epilogue of a vectorized epilogue.

Bootstrap & regtest running on x86_64-unknown-linux-gnu.

I did not verify this solves the original aarch64 testcase yet
but it looks like a simpler fix and explains why I don't see
the issue on the 11 branch which does otherwise the same transforms.

Richard.

2022-04-27  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/105219
	* tree-vect-loop.cc (vect_transform_loop): Disable
	special code narrowing the vectorized epilogue epilogue
	max iterations when peeling for alignment was in effect.

	* gcc.dg/vect/pr105219.c: New testcase.
---
 gcc/testsuite/gcc.dg/vect/pr105219.c | 29 ++++++++++++++++++++++++++++
 gcc/tree-vect-loop.cc                |  2 +-
 2 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/vect/pr105219.c
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Patch

diff --git a/gcc/testsuite/gcc.dg/vect/pr105219.c b/gcc/testsuite/gcc.dg/vect/pr105219.c
new file mode 100644
index 00000000000..0cb7ae2f4d6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr105219.c
@@ -0,0 +1,29 @@ 
+/* { dg-do run } */
+/* { dg-additional-options "-O3" } */
+/* { dg-additional-options "-mtune=intel" { target x86_64-*-* i?86-*-* } } */
+
+#include "tree-vect.h"
+
+int data[128];
+
+void __attribute((noipa))
+foo (int *data, int n)
+{
+  for (int i = 0; i < n; ++i)
+    data[i] = i;
+}
+
+int main()
+{
+  check_vect ();
+  for (int start = 0; start < 16; ++start)
+    for (int n = 1; n < 3*16; ++n)
+      {
+        __builtin_memset (data, 0, sizeof (data));
+        foo (&data[start], n);
+        for (int j = 0; j < n; ++j)
+          if (data[start + j] != j)
+            __builtin_abort ();
+      }
+  return 0;
+}
diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index d7bc34636bd..217abab814b 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -9977,7 +9977,7 @@  vect_transform_loop (loop_vec_info loop_vinfo, gimple *loop_vectorized_call)
 			    lowest_vf) - 1
 	   : wi::udiv_floor (loop->nb_iterations_upper_bound + bias_for_lowest,
 			     lowest_vf) - 1);
-      if (main_vinfo)
+      if (main_vinfo && !main_vinfo->peeling_for_alignment)
 	{
 	  unsigned int bound;
 	  poly_uint64 main_iters