From 26285af40f98dfdb809b98b08386073c63b65db1 Mon Sep 17 00:00:00 2001
From: Jan Hubicka <jh@suse.cz>
Date: Sun, 15 Nov 2020 15:10:22 +0100
Subject: [PATCH] Mare return to clear EAF_UNUSED flag.

gcc/ChangeLog:
	* ipa-modref.c (analyze_ssa_name_flags): Make return to clear
	EAF_UNUSED flag.

gcc/testsuite/ChangeLog:
	* gcc.c-torture/execute/pr97836.c: New test.
---
 gcc/ipa-modref.c                              |  6 ++++--
 gcc/testsuite/gcc.c-torture/execute/pr97836.c | 17 +++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr97836.c

diff --git a/gcc/ipa-modref.c b/gcc/ipa-modref.c
index 5273c20..4a43c50 100644
--- a/gcc/ipa-modref.c
+++ b/gcc/ipa-modref.c
@@ -1224,10 +1224,12 @@ analyze_ssa_name_flags (tree name, vec<unsigned char> &known_flags, int depth)
 	  print_gimple_stmt (dump_file, use_stmt, 0);
 	}
 
-      /* Gimple return may load the return value.  */
+      /* Gimple return may load the return value.
+	 Returning name counts as an use by tree-ssa-structalias.c  */
       if (greturn *ret = dyn_cast <greturn *> (use_stmt))
 	{
-	  if (memory_access_to (gimple_return_retval (ret), name))
+	  if (memory_access_to (gimple_return_retval (ret), name)
+	      || name == gimple_return_retval (ret))
 	    flags &= ~EAF_UNUSED;
 	}
       /* Account for LHS store, arg loads and flags from callee function.  */
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr97836.c b/gcc/testsuite/gcc.c-torture/execute/pr97836.c
new file mode 100644
index 0000000..4585e1f
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr97836.c
@@ -0,0 +1,17 @@
+int a;
+
+int b(int c) { return 0; }
+
+static int *d(int *e) {
+  if (a) {
+    a = a && b(*e);
+  }
+  return e;
+}
+
+int main() {
+  int f;
+  if (d(&f) != &f)
+    __builtin_abort();
+  return 0;
+}
-- 
2.7.4