[PATCH] Fix fallthrough attribute ignorance w/ -fsanitize=address (PR sanitizer/82792).

["Martin Liška" <mliska@suse.cz>]

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Hello.

Quite simple patch that ignores IFN_ASAN_CHECK call that is introduced in gimplifier.
Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.

Ready to be installed?
Martin

gcc/ChangeLog:

2017-11-07  Martin Liska  <mliska@suse.cz>

	PR sanitizer/82792
	* gimplify.c (expand_FALLTHROUGH_r): Skip IFN_ASAN_MARK.

gcc/testsuite/ChangeLog:

2017-11-07  Martin Liska  <mliska@suse.cz>

	PR sanitizer/82792
	* g++.dg/asan/pr82792.C: New test.
---
 gcc/gimplify.c                      |  8 ++++++--
 gcc/testsuite/g++.dg/asan/pr82792.C | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/asan/pr82792.C



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diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index c4fd5038d92..9563d825a6a 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -2223,7 +2223,8 @@ expand_FALLTHROUGH_r (gimple_stmt_iterator *gsi_p, bool *handled_ops_p,
 	  while (!gsi_end_p (gsi2))
 	    {
 	      stmt = gsi_stmt (gsi2);
-	      if (gimple_code (stmt) == GIMPLE_LABEL)
+	      enum gimple_code gc = gimple_code (stmt);
+	      if (gc == GIMPLE_LABEL)
 		{
 		  tree label = gimple_label_label (as_a <glabel *> (stmt));
 		  if (gimple_has_location (stmt) && DECL_ARTIFICIAL (label))
@@ -2232,8 +2233,11 @@ expand_FALLTHROUGH_r (gimple_stmt_iterator *gsi_p, bool *handled_ops_p,
 		      break;
 		    }
 		}
+	      else if (gc == GIMPLE_CALL
+		       && gimple_call_internal_p (stmt, IFN_ASAN_MARK))
+		;
 	      else
-		/* Something other than a label.  That's not expected.  */
+		/* Something other is not expected.  */
 		break;
 	      gsi_next (&gsi2);
 	    }
diff --git a/gcc/testsuite/g++.dg/asan/pr82792.C b/gcc/testsuite/g++.dg/asan/pr82792.C
new file mode 100644
index 00000000000..99f1c35328c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/asan/pr82792.C
@@ -0,0 +1,32 @@
+/* PR sanitizer/82792 */
+/* { dg-do compile } */
+/* { dg-options "-fsanitize=address" } */
+
+extern int
+test (int i, int j)
+{
+  long c;
+  (c) = 1;
+  switch (i)
+    {
+    case 1:
+      if (j)
+	{
+	  c = 1;
+	}
+      goto default_case;
+    case 2:
+      {
+	if (j)
+	  {
+	    c = 0;
+	  }
+      }
+      __attribute ((fallthrough));
+    default_case:
+    default:
+      c = 0;
+      break;
+    }
+  return 0;
+}