[PATCH] Fix PR54684

[Richard Guenther]

This fixes PR54684 where optimizing __builtin_unreachable () during
builtin folding fails to update SSA operands properly.

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

Richard.

2012-09-24  Richard Guenther  <rguent...@suse.de>

        PR tree-optimization/54684
        * tree-ssa-ccp.c (optimize_unreachable): Properly update stmts.

        * g++.dg/torture/pr54684.C: New testcase.

Index: gcc/tree-ssa-ccp.c
===================================================================
--- gcc/tree-ssa-ccp.c  (revision 191664)
+++ gcc/tree-ssa-ccp.c  (working copy)
@@ -2355,6 +2355,7 @@ optimize_unreachable (gimple_stmt_iterat
            gimple_cond_make_true (stmt);
          else
            gcc_unreachable ();
+         update_stmt (stmt);
        }
       else
        {
Index: gcc/testsuite/g++.dg/torture/pr54684.C
===================================================================
--- gcc/testsuite/g++.dg/torture/pr54684.C      (revision 0)
+++ gcc/testsuite/g++.dg/torture/pr54684.C      (working copy)
@@ -0,0 +1,62 @@
+// { dg-do compile }
+
+typedef union tree_node *tree;
+typedef union gimple_statement_d *gimple;
+struct vec_prefix { unsigned num_; };
+template<typename T> struct vec_t {
+    unsigned length (void) const;
+    T &operator[] (unsigned);
+    vec_prefix prefix_;
+    T vec_[1];
+};
+template<typename T> inline unsigned vec_t<T>::length (void) const {
+    return prefix_.num_;
+}
+template<typename T> T & vec_t<T>::operator[] (unsigned ix) {
+    ((void)(__builtin_expect(!(ix < prefix_.num_), 0) ? 
__builtin_unreachable(), 0 : 0));
+    return vec_[ix];
+}
+enum tree_code { PARM_DECL };
+struct tree_base {
+    enum tree_code code : 16;
+    unsigned default_def_flag : 1;
+};
+union tree_node {
+    struct tree_base base;
+};
+struct ipa_param_descriptor {
+    tree decl;
+    unsigned used : 1;
+};
+typedef struct ipa_param_descriptor ipa_param_descriptor_t;
+struct ipa_node_params {
+    vec_t<ipa_param_descriptor_t> *descriptors;
+};
+static inline int ipa_get_param_count (struct ipa_node_params *info) {
+    return ((info->descriptors) ? (info->descriptors)->length () : 0);
+}
+static inline tree ipa_get_param (struct ipa_node_params *info, int i) {
+    return ((*(info->descriptors))[i]).decl;
+}
+static inline void ipa_set_param_used (struct ipa_node_params *info, int i, 
bool val) {
+    ((*(info->descriptors))[i]).used = val;
+}
+int ipa_get_param_decl_index (struct ipa_node_params *info, tree ptree)
+{
+  int i, count;
+  count = ipa_get_param_count (info);
+  for (i = 0; i < count; i++)
+    if (ipa_get_param (info, i) == ptree)       return i;
+  return -1;
+}
+bool visit_ref_for_mod_analysis (gimple stmt __attribute__ ((__unused__)),
+                                tree op, void *data)
+{
+  struct ipa_node_params *info = (struct ipa_node_params *) data;
+  if (op && ((enum tree_code) (op)->base.code) == PARM_DECL)
+    {
+      int index = ipa_get_param_decl_index (info, op);
+      ((void)(__builtin_expect(!(index >= 0), 0) ? __builtin_unreachable(), 0 
: 0));
+      ipa_set_param_used (info, index, true);
+    }
+}