[gcc r14-8984] middle-end: inspect all exits for additional annotations for loop.

[Tamar Christina <tnfchris@gcc.gnu.org>]

https://gcc.gnu.org/g:16ae5efedd389e8952f35bb10665518c22a9251c

commit r14-8984-g16ae5efedd389e8952f35bb10665518c22a9251c
Author: Tamar Christina <tamar.christina@arm.com>
Date:   Wed Feb 14 16:13:51 2024 +0000

    middle-end: inspect all exits for additional annotations for loop.
    
    Attaching a pragma to a loop which has a complex condition often gets the pragma
    dropped. e.g.
    
    #pragma GCC novector
      while (i < N && parse_tables_n--)
    
    before lowering this is represented as:
    
     if (ANNOTATE_EXPR <i <= 305 && parse_tables_n--  != 0, no-vector>) ...
    
    But after lowering the condition is broken appart and attached to the final
    component of the expression:
    
      if (parse_tables_n.2_2 != 0) goto <D.4456>; else goto <D.4453>;
      <D.4456>:
        iftmp.1D.4452 = 1;
        goto <D.4454>;
      <D.4453>:
        iftmp.1D.4452 = 0;
      <D.4454>:
        D.4451 = .ANNOTATE (iftmp.1D.4452, 2, 0);
        if (D.4451 != 0) goto <D.4442>; else goto <D.4440>;
      <D.4440>:
    
    and it's never heard from again because during replace_loop_annotate we only
    inspect the loop header and latch for annotations.
    
    Since annotations were supposed to apply to the loop as a whole this fixes it
    by checking the loop exit src blocks for annotations instead.
    
    gcc/ChangeLog:
    
            * tree-cfg.cc (replace_loop_annotate): Inspect loop edges for annotations.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.dg/vect/vect-novect_gcond.c: New test.

Diff:
---
 gcc/testsuite/gcc.dg/vect/vect-novect_gcond.c | 39 +++++++++++++++++++++++++++
 gcc/tree-cfg.cc                               |  9 +++----
 2 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/vect/vect-novect_gcond.c b/gcc/testsuite/gcc.dg/vect/vect-novect_gcond.c
new file mode 100644
index 000000000000..01e69cbef9d5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/vect-novect_gcond.c
@@ -0,0 +1,39 @@
+/* { 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-not "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;
+#pragma GCC novector
+  while (i < N && parse_tables_n--)
+    table[i++] = 0;
+
+  return table[NEEDLE];
+}
+
+int main ()
+{
+  check_vect ();
+
+#pragma GCC novector
+  for (int j = 0; j < N; j++)
+    table[j] = -1;
+
+  if (foo (0, 0xFFFF) != 0)
+    __builtin_abort ();
+
+  return 0;
+}
diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
index cdd439fe7506..bdffc3b4ed27 100644
--- a/gcc/tree-cfg.cc
+++ b/gcc/tree-cfg.cc
@@ -320,12 +320,9 @@ replace_loop_annotate (void)
 
   for (auto loop : loops_list (cfun, 0))
     {
-      /* First look into the header.  */
-      replace_loop_annotate_in_block (loop->header, loop);
-
-      /* Then look into the latch, if any.  */
-      if (loop->latch)
-	replace_loop_annotate_in_block (loop->latch, loop);
+      /* Check all exit source blocks for annotations.  */
+      for (auto e : get_loop_exit_edges (loop))
+	replace_loop_annotate_in_block (e->src, loop);
 
       /* Push the global flag_finite_loops state down to individual loops.  */
       loop->finite_p = flag_finite_loops;