gimple: Ignore *0 = {CLOBBER} in path isolation [PR96722]

Clobbers of MEM_REF with NULL address are just fancy nops, something we just
ignore and don't emit any code for it (ditto for other clobbers), they just
mark end of life on something, so we shouldn't infer from those that there
is some UB.

2020-08-25  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/96722
	* gimple.c (infer_nonnull_range): Formatting fix.
	(infer_nonnull_range_by_dereference): Return false for clobber stmts.

	* g++.dg/opt/pr96722.C: New test.

(cherry picked from commit a5b15fcb954ba63d58f0daa700281aba33b5f24a)

diff --git a/gcc/gimple.c b/gcc/gimple.c
index 10c562f4deffdd7237be2663aefb1594c1a8c426..2e1894defa50dbf272a26b3fff5af3b64dcb5dfc 100644 (file)
--- a/gcc/gimple.c
+++ b/gcc/gimple.c
@@ -2932,8 +2932,8 @@ check_loadstore (gimple *, tree op, tree, void *data)
 bool
 infer_nonnull_range (gimple *stmt, tree op)
 {
-  return infer_nonnull_range_by_dereference (stmt, op)
-    || infer_nonnull_range_by_attribute (stmt, op);
+  return (infer_nonnull_range_by_dereference (stmt, op)
+         || infer_nonnull_range_by_attribute (stmt, op));
 }
 
 /* Return true if OP can be inferred to be non-NULL after STMT
@@ -2945,7 +2945,8 @@ infer_nonnull_range_by_dereference (gimple *stmt, tree op)
      non-NULL if -fdelete-null-pointer-checks is enabled.  */
   if (!flag_delete_null_pointer_checks
       || !POINTER_TYPE_P (TREE_TYPE (op))
-      || gimple_code (stmt) == GIMPLE_ASM)
+      || gimple_code (stmt) == GIMPLE_ASM
+      || gimple_clobber_p (stmt))
     return false;
 
   if (walk_stmt_load_store_ops (stmt, (void *)op,

diff --git a/gcc/testsuite/g++.dg/opt/pr96722.C b/gcc/testsuite/g++.dg/opt/pr96722.C
new file mode 100644 (file)
index 0000000..408dfee
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/pr96722.C
@@ -0,0 +1,20 @@
+// PR tree-optimization/96722
+// { dg-do run }
+// { dg-options "-O2" }
+
+struct S { int s; ~S () {} };
+
+void
+foo (S *a)
+{
+  if (a)
+    return;
+  a->~S ();
+}
+
+int
+main ()
+{
+  S s;
+  foo (&s);
+}