fix 24665

[Richard Henderson <rth at redhat dot com>]

The problem here, as discussed in front of the new function, is that
the shallow predicates in tree-gimple.c assume that expressions have
been, or will be, gimplified.  But DECL_INITIAL expressions haven't
and won't be, so we need a deeper predicate.


r~


        PR tree-opt/24665
        * tree-gimple.c (is_gimple_id): Export.
        * tree-gimple.h (is_gimple_id): Declare.
        * tree-ssa-ccp.c (ccp_decl_initial_min_invariant): New.
        (get_default_value): Use it.
        (maybe_fold_stmt_indirect): Likewise.

Index: tree-gimple.c
===================================================================
--- tree-gimple.c	(revision 107242)
+++ tree-gimple.c	(working copy)
@@ -35,8 +35,6 @@ Boston, MA 02110-1301, USA.  */
 
 /* For the definitive definition of GIMPLE, see doc/tree-ssa.texi.  */
 
-static inline bool is_gimple_id (tree);
-
 /* Validation of GIMPLE expressions.  */
 
 /* Return true if T is a GIMPLE RHS for an assignment to a temporary.  */
@@ -244,7 +242,7 @@ is_gimple_variable (tree t)
 
 /*  Return true if T is a GIMPLE identifier (something with an address).  */
 
-static inline bool
+bool
 is_gimple_id (tree t)
 {
   return (is_gimple_variable (t)
Index: tree-gimple.h
===================================================================
--- tree-gimple.h	(revision 107242)
+++ tree-gimple.h	(working copy)
@@ -53,6 +53,8 @@ extern bool is_gimple_formal_tmp_var (tr
 extern bool is_gimple_formal_tmp_reg (tree);
 /* Returns true iff T is any sort of variable.  */
 extern bool is_gimple_variable (tree);
+/* Returns true iff T is any sort of symbol.  */
+extern bool is_gimple_id (tree);
 /* Returns true iff T is a variable or an INDIRECT_REF (of a variable).  */
 extern bool is_gimple_min_lval (tree);
 /* Returns true iff T is something whose address can be taken.  */
Index: testsuite/g++.dg/opt/pr24665.C
===================================================================
--- testsuite/g++.dg/opt/pr24665.C	(revision 0)
+++ testsuite/g++.dg/opt/pr24665.C	(revision 0)
@@ -0,0 +1,29 @@
+// { dg-do compile }
+// { dg-options "-O2" }
+
+typedef unsigned long T;
+typedef volatile T* const hwreg_t;
+struct RegisterLayout
+{
+    T intmask;
+};
+struct Controller_t
+{
+    Controller_t();
+    inline void
+    disableInterrupt()
+    {
+        *mpMaskRegister = 0;
+    };
+    static hwreg_t mpMaskRegister;
+};
+
+extern char SimulatedRegisters[];
+
+hwreg_t Controller_t::mpMaskRegister
+  = &(reinterpret_cast<volatile RegisterLayout*>(SimulatedRegisters))->intmask;
+
+Controller_t::Controller_t()
+{
+    disableInterrupt();
+}
Index: tree-ssa-ccp.c
===================================================================
--- tree-ssa-ccp.c	(revision 107242)
+++ tree-ssa-ccp.c	(working copy)
@@ -273,6 +273,32 @@ debug_lattice_value (prop_value_t val)
 }
 
 
+/* The regular is_gimple_min_invariant does a shallow test of the object.
+   It assumes that full gimplification has happened, or will happen on the
+   object.  For a value coming from DECL_INITIAL, this is not true, so we
+   have to be more strict outselves.  */
+
+static bool
+ccp_decl_initial_min_invariant (tree t)
+{
+  if (!is_gimple_min_invariant (t))
+    return false;
+  if (TREE_CODE (t) == ADDR_EXPR)
+    {
+      /* Inline and unroll is_gimple_addressable.  */
+      while (1)
+	{
+	  t = TREE_OPERAND (t, 0);
+	  if (is_gimple_id (t))
+	    return true;
+	  if (!handled_component_p (t))
+	    return false;
+	}
+    }
+  return true;
+}
+
+
 /* Compute a default value for variable VAR and store it in the
    CONST_VAL array.  The following rules are used to get default
    values:
@@ -317,7 +343,7 @@ get_default_value (tree var)
   else if (TREE_STATIC (sym)
 	   && TREE_READONLY (sym)
 	   && DECL_INITIAL (sym)
-	   && is_gimple_min_invariant (DECL_INITIAL (sym)))
+	   && ccp_decl_initial_min_invariant (DECL_INITIAL (sym)))
     {
       /* Globals and static variables declared 'const' take their
 	 initial value.  */
@@ -1712,7 +1738,7 @@ maybe_fold_stmt_indirect (tree expr, tre
 
       /* Fold away CONST_DECL to its value, if the type is scalar.  */
       if (TREE_CODE (base) == CONST_DECL
-	  && is_gimple_min_invariant (DECL_INITIAL (base)))
+	  && ccp_decl_initial_min_invariant (DECL_INITIAL (base)))
 	return DECL_INITIAL (base);
 
       /* Try folding *(&B+O) to B[X].  */