[PATCH] Ensure DEBUG_INSNs don't contain MEMs with non-canonical MEM_EXPRs (PR debug/48134)

[Jakub Jelinek]

Hi!

Currently expand_debug_expr doesn't always guarantee canonical
MEM_EXPRs, if MEM_EXPR isn't canonical, sometimes aliasing code ICEs on it
(since recent Richard's change fortunately only if --enable-checking=yes).

The following patch canonicalizes those using fold and if canonicalization
isn't successful, just clears the MEM_EXPR.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk and
4.6.1?

2011-03-17  Jakub Jelinek  <ja...@redhat.com>

        PR debug/48134
        * cfgexpand.c (expand_debug_expr) <component_ref>: Use fold to
        canonicalize MEM_EXPR, if it still isn't canonical afterwards, just
        clear MEM_EXPR.

        * gcc.dg/pr48134.c: New test.

--- gcc/cfgexpand.c.jj  2011-03-16 18:30:12.000000000 +0100
+++ gcc/cfgexpand.c     2011-03-16 22:05:13.000000000 +0100
@@ -2712,6 +2712,8 @@ expand_debug_expr (tree exp)
 
        if (MEM_P (op0))
          {
+           tree mem_exp;
+
            if (mode1 == VOIDmode)
              /* Bitfield.  */
              mode1 = smallest_mode_for_size (bitsize, MODE_INT);
@@ -2736,6 +2738,12 @@ expand_debug_expr (tree exp)
            if (op0 == orig_op0)
              op0 = shallow_copy_rtx (op0);
            set_mem_attributes (op0, exp, 0);
+           mem_exp = fold (exp);
+           if (!SSA_VAR_P (mem_exp)
+               && TREE_CODE (mem_exp) != MEM_REF
+               && TREE_CODE (mem_exp) != TARGET_MEM_REF)
+             mem_exp = NULL_TREE;
+           set_mem_expr (op0, mem_exp);
          }
 
        if (bitpos == 0 && mode == GET_MODE (op0))
--- gcc/testsuite/gcc.dg/pr48134.c.jj   2011-03-16 22:04:35.000000000 +0100
+++ gcc/testsuite/gcc.dg/pr48134.c      2011-03-16 22:02:13.000000000 +0100
@@ -0,0 +1,25 @@
+/* PR debug/48134 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fstack-check=specific -fno-tree-dse -fno-tree-fre 
-fno-tree-loop-optimize -g" } */
+
+struct S { int w, z; };
+struct T { struct S s; };
+int i;
+
+static inline struct S
+bar (struct S x)
+{
+  i++;
+  return x;
+}
+
+int
+foo (struct T t, struct S s)
+{
+  struct S *c = &s;
+  if (i)
+    c = &t.s;
+  t.s.w = 3;
+  s = bar (*c);
+  return t.s.w;
+}

        Jakub