[gcc r11-8898] Clear EAF_NOCLOBBER for indirect calls

[Martin Liska <marxin@gcc.gnu.org>]

https://gcc.gnu.org/g:d0adc557a26963b9ad0e07829872c968e67c5ffc

commit r11-8898-gd0adc557a26963b9ad0e07829872c968e67c5ffc
Author: Jan Hubicka <jh@suse.cz>
Date:   Sun Aug 22 20:57:19 2021 +0200

    Clear EAF_NOCLOBBER for indirect calls
    
    gcc/ChangeLog:
    
    2021-08-22  Jan Hubicka  <hubicka@ucw.cz>
                Martin Liska  <mliska@suse.cz>
    
            PR middle-end/101949
            * ipa-modref.c (analyze_ssa_name_flags): Indirect call implies
            ~EAF_NOCLOBBER.
    
    gcc/testsuite/ChangeLog:
    
    2021-08-22  Jan Hubicka  <hubicka@ucw.cz>
                Martin Liska  <mliska@suse.cz>
    
            * gcc.dg/lto/pr101949_0.c: New test.
            * gcc.dg/lto/pr101949_1.c: New test.
    
    (cherry picked from commit 9b08f7764cecd16cba84944f2a8b67a7f73a7ce7)

Diff:
---
 gcc/ipa-modref.c                      |  9 +++++++++
 gcc/testsuite/gcc.dg/lto/pr101949_0.c | 20 ++++++++++++++++++++
 gcc/testsuite/gcc.dg/lto/pr101949_1.c |  4 ++++
 3 files changed, 33 insertions(+)

diff --git a/gcc/ipa-modref.c b/gcc/ipa-modref.c
index ef5e62beb0e..dc5ee8cc2d0 100644
--- a/gcc/ipa-modref.c
+++ b/gcc/ipa-modref.c
@@ -1621,6 +1621,15 @@ analyze_ssa_name_flags (tree name, vec<modref_lattice> &lattice, int depth,
       else if (gcall *call = dyn_cast <gcall *> (use_stmt))
 	{
 	  tree callee = gimple_call_fndecl (call);
+
+	  /* IPA PTA internally it treats calling a function as "writing" to
+	     the argument space of all functions the function pointer points to
+	     (PR101949).  We can not drop EAF_NOCLOBBER only when ipa-pta
+	     is on since that would allow propagation of this from -fno-ipa-pta
+	     to -fipa-pta functions.  */
+	  if (gimple_call_fn (use_stmt) == name)
+	    lattice[index].merge (~EAF_NOCLOBBER);
+
 	  /* Return slot optimization would require bit of propagation;
 	     give up for now.  */
 	  if (gimple_call_return_slot_opt_p (call)
diff --git a/gcc/testsuite/gcc.dg/lto/pr101949_0.c b/gcc/testsuite/gcc.dg/lto/pr101949_0.c
new file mode 100644
index 00000000000..142dffe8780
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/pr101949_0.c
@@ -0,0 +1,20 @@
+/* { dg-lto-do run } */
+/* { dg-lto-options { "-O2 -fipa-pta -flto -flto-partition=1to1" } } */
+
+extern int bar (int (*)(int *), int *);
+
+static int x;
+
+static int __attribute__ ((noinline)) foo (int *p)
+{
+  *p = 1;
+  x = 0;
+  return *p;
+}
+
+int main ()
+{
+  if (bar (foo, &x) != 0)
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/lto/pr101949_1.c b/gcc/testsuite/gcc.dg/lto/pr101949_1.c
new file mode 100644
index 00000000000..871d15c9bfb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/pr101949_1.c
@@ -0,0 +1,4 @@
+int __attribute__((noinline,noclone)) bar (int (*fn)(int *), int *p)
+{
+  return fn (p);
+}