[PATCH] ipa-cp: Avoid adjusting references through self-recursion (PR 104813)

[Martin Jambor <mjambor@suse.cz>]

Hi,

when writing the patch that downgrades address-taken references to
load references when IPA-CP can prove that all uses of the taken
address ends up in loads, I unfortunately did not take into account
that find_more_scalar_values_for_callers_subset now happily adds
self-recursive edges to the set of callers which should be immediately
redirected (originally recursion was meant to be handled as edge
redirection in a second pass over the SCC).

The code as it is can now decrement the referece counters too many
times.  This can remedied by removing self-recursive edges earlier, we
already do it because of thunk expansion issues, and so this patch
does exactly that.

Bootstrapped and LTO-bootstrapped and tested on x86_64-linux.  OK for
master?

Thanks,

Martin


gcc/ChangeLog:

2022-03-07  Martin Jambor  <mjambor@suse.cz>

	PR ipa/104813
	* ipa-cp.cc (create_specialized_node): Move removal of
	self-recursive calls from callers vector before refrence
	adjustments.

gcc/testsuite/ChangeLog:

2022-03-07  Martin Jambor  <mjambor@suse.cz>

	PR ipa/104813
	* gcc.dg/ipa/pr104813.c: New test.
---
 gcc/ipa-cp.cc                       | 20 +++++++++---------
 gcc/testsuite/gcc.dg/ipa/pr104813.c | 32 +++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 10 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/ipa/pr104813.c

diff --git a/gcc/ipa-cp.cc b/gcc/ipa-cp.cc
index 453e9c93cc3..18047c209a8 100644
--- a/gcc/ipa-cp.cc
+++ b/gcc/ipa-cp.cc
@@ -5099,6 +5099,16 @@ create_specialized_node (struct cgraph_node *node,
   else
     new_adjustments = NULL;
 
+  auto_vec<cgraph_edge *, 2> self_recursive_calls;
+  for (i = callers.length () - 1; i >= 0; i--)
+    {
+      cgraph_edge *cs = callers[i];
+      if (cs->caller == node)
+	{
+	  self_recursive_calls.safe_push (cs);
+	  callers.unordered_remove (i);
+	}
+    }
   replace_trees = cinfo ? vec_safe_copy (cinfo->tree_map) : NULL;
   for (i = 0; i < count; i++)
     {
@@ -5129,16 +5139,6 @@ create_specialized_node (struct cgraph_node *node,
       if (replace_map)
 	vec_safe_push (replace_trees, replace_map);
     }
-  auto_vec<cgraph_edge *, 2> self_recursive_calls;
-  for (i = callers.length () - 1; i >= 0; i--)
-    {
-      cgraph_edge *cs = callers[i];
-      if (cs->caller == node)
-	{
-	  self_recursive_calls.safe_push (cs);
-	  callers.unordered_remove (i);
-	}
-    }
 
   unsigned &suffix_counter = clone_num_suffixes->get_or_insert (
 			       IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (
diff --git a/gcc/testsuite/gcc.dg/ipa/pr104813.c b/gcc/testsuite/gcc.dg/ipa/pr104813.c
new file mode 100644
index 00000000000..34f413e3823
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ipa/pr104813.c
@@ -0,0 +1,32 @@
+/* { dg-do compile } */
+/* { dg-options "-O3"  } */
+
+int a, b, c, d, *e;
+void f(int h) {
+  if (b) {
+    int g;
+    while (g++)
+      d = *e;
+    e++;
+  }
+}
+static void i();
+static void j(int *h, int k, int *l) {
+  if (c) {
+    int *o = h, m;
+    f(*l);
+    i(m);
+    j(o, 1, o);
+    for (;;)
+      ;
+  }
+}
+void i() {
+  int *n = &a;
+  while (1)
+    j(n, 1, n);
+}
+int main() {
+  j(&a, 0, &a);
+  return 0;
+}
-- 
2.35.1