c: Fix -Wduplicated-branches ICE [PR97125]

We crash here because since r11-3302 the C FE uses codes like SWITCH_STMT
in the else branches in the attached test, and inchash::add_expr in
do_warn_duplicated_branches doesn't handle these front-end codes.  In
the C++ FE this works because by the time we get to do_warn_duplicated_branches
we've already cp_genericize'd the SWITCH_STMT tree into a SWITCH_EXPR.

The fix is to call do_warn_duplicated_branches_r only after loops and other
structured control constructs have been lowered.

gcc/c-family/ChangeLog:

	PR c/97125
	* c-gimplify.c (c_genericize): Only call do_warn_duplicated_branches_r
	after loops and other structured control constructs have been lowered.

gcc/testsuite/ChangeLog:

	PR c/97125
	* c-c++-common/Wduplicated-branches-15.c: New test.

diff --git a/gcc/c-family/c-gimplify.c b/gcc/c-family/c-gimplify.c
index 8b326c99d487b61da830c862ed2396c81a56a7da..d1e391590dd3f14a19d6f48a006c324d34a8fb19 100644 (file)
--- a/gcc/c-family/c-gimplify.c
+++ b/gcc/c-family/c-gimplify.c
@@ -533,10 +533,6 @@ c_genericize (tree fndecl)
                 &pset);
     }
 
-  if (warn_duplicated_branches)
-    walk_tree_without_duplicates (&DECL_SAVED_TREE (fndecl),
-                                 do_warn_duplicated_branches_r, NULL);
-
   /* Genericize loops and other structured control constructs.  The C++
      front end has already done this in lang-specific code.  */
   if (!c_dialect_cxx ())
@@ -550,6 +546,10 @@ c_genericize (tree fndecl)
       pop_cfun ();
     }
 
+  if (warn_duplicated_branches)
+    walk_tree_without_duplicates (&DECL_SAVED_TREE (fndecl),
+                                 do_warn_duplicated_branches_r, NULL);
+
   /* Dump the C-specific tree IR.  */
   dump_orig = get_dump_info (TDI_original, &local_dump_flags);
   if (dump_orig)

diff --git a/gcc/testsuite/c-c++-common/Wduplicated-branches-15.c b/gcc/testsuite/c-c++-common/Wduplicated-branches-15.c
new file mode 100644 (file)
index 0000000..d494360
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Wduplicated-branches-15.c
@@ -0,0 +1,32 @@
+/* PR c/97125 */
+/* { dg-do compile } */
+/* { dg-options "-Wduplicated-branches" } */
+
+void foo (void);
+
+void
+fn1 (void)
+{
+  if (0)
+    foo ();
+  else
+    switch (0);
+}
+
+void
+fn2 (void)
+{
+  if (0)
+    foo ();
+  else
+    while (0);
+}
+
+void
+fn3 (void)
+{
+  if (0)
+    foo ();
+  else
+    for (;;);
+}