[gcc r13-1972] tree-optimization/106533 - loop distribution of inner loop of nest

[Richard Biener <rguenth@gcc.gnu.org>]

https://gcc.gnu.org/g:36bc2a8f24f9c8f6eb2c579d520d7fc73a113ae1

commit r13-1972-g36bc2a8f24f9c8f6eb2c579d520d7fc73a113ae1
Author: Richard Biener <rguenther@suse.de>
Date:   Fri Aug 5 10:40:18 2022 +0200

    tree-optimization/106533 - loop distribution of inner loop of nest
    
    Loop distribution currently gives up if the outer loop of a loop
    nest it analyzes contains a stmt with side-effects instead of
    continuing to analyze the innermost loop.  The following fixes that
    by continuing anyway.
    
            PR tree-optimization/106533
            * tree-loop-distribution.cc (loop_distribution::execute): Continue
            analyzing the inner loops when find_seed_stmts_for_distribution
            fails.
    
            * gcc.dg/tree-ssa/ldist-39.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/tree-ssa/ldist-39.c | 16 ++++++++++++++++
 gcc/tree-loop-distribution.cc            |  2 +-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ldist-39.c b/gcc/testsuite/gcc.dg/tree-ssa/ldist-39.c
new file mode 100644
index 00000000000..3ef72864d96
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ldist-39.c
@@ -0,0 +1,16 @@
+/* PR/106533 */
+/* { dg-options "-O2 -fdump-tree-ldist-optimized" } */
+
+void bar (int *a, int * __restrict b)
+{
+  for (int k = 0; k < 10; k++)
+    {
+      for (int j = 0; j < 100000; ++j)
+	a[j] = b[j];
+      __builtin_printf ("Foo!");
+    }
+}
+
+/* The stmt with side-effects in the outer loop should not prevent
+   distribution of the inner loop of the loop nest.  */
+/* { dg-final { scan-tree-dump "optimized: Loop . distributed: split to 0 loops and 1 library calls" "ldist" } } */
diff --git a/gcc/tree-loop-distribution.cc b/gcc/tree-loop-distribution.cc
index 0ee441c077d..e1948fb452a 100644
--- a/gcc/tree-loop-distribution.cc
+++ b/gcc/tree-loop-distribution.cc
@@ -3829,7 +3829,7 @@ loop_distribution::execute (function *fun)
 	{
 	  auto_vec<gimple *> work_list;
 	  if (!find_seed_stmts_for_distribution (loop, &work_list))
-	    break;
+	    continue;
 
 	  const char *str = loop->inner ? " nest" : "";
 	  dump_user_location_t loc = find_loop_location (loop);