[PATCH] Fix split_live_ranges_for_shrink_wrap (PR rtl-optimization/59166)

[Jakub Jelinek]

Hi!

The problem on this testcase is that we have
(debug_insn 30 29 31 7 (var_location:HI D#1 (subreg:HI (reg/v:SI 93 [ p ]) 0)) 
pr59166.c:20 -1
     (nil))
and split_live_ranges_for_shrink_wrap decides to replace
SImode pseudo 93 with some other SImode pseudo.  But it
uses DF_REF_LOC, which is address of the HImode subreg around the pseudo,
validate_change succeeds on it, because there is no validation inside of
debug_insns and then we crash during var-tracking because of a mode
mismatch.

The following patch uses DF_REF_REAL_LOC instead, so that it looks through
the subreg and adjusts what it should.  Code inspection showed the same
issue in find_moveable_pseudos, don't have a testcase for that though.

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

2013-11-26  Jakub Jelinek  <ja...@redhat.com>

        PR rtl-optimization/59166
        * ira.c (find_moveable_pseudos): Use DF_REF_REAL_LOC instead of
        DF_REF_LOC in validate_change call.
        (split_live_ranges_for_shrink_wrap): Likewise.

        * gcc.dg/torture/pr59166.c: New test.

--- gcc/ira.c.jj        2013-11-25 10:20:12.000000000 +0100
+++ gcc/ira.c   2013-11-26 12:45:27.443495633 +0100
@@ -4812,7 +4812,7 @@ find_moveable_pseudos (void)
        {
          rtx def_reg = DF_REF_REG (def);
          rtx newreg = ira_create_new_reg (def_reg);
-         if (validate_change (def_insn, DF_REF_LOC (def), newreg, 0))
+         if (validate_change (def_insn, DF_REF_REAL_LOC (def), newreg, 0))
            {
              unsigned nregno = REGNO (newreg);
              emit_insn_before (gen_move_insn (def_reg, newreg), use_insn);
@@ -5034,7 +5034,7 @@ split_live_ranges_for_shrink_wrap (void)
 
       rtx newreg = NULL_RTX;
       df_ref use, next;
-      for (use = DF_REG_USE_CHAIN (REGNO(dest)); use; use = next)
+      for (use = DF_REG_USE_CHAIN (REGNO (dest)); use; use = next)
        {
          rtx uin = DF_REF_INSN (use);
          next = DF_REF_NEXT_REG (use);
@@ -5045,7 +5045,7 @@ split_live_ranges_for_shrink_wrap (void)
            {
              if (!newreg)
                newreg = ira_create_new_reg (dest);
-             validate_change (uin, DF_REF_LOC (use), newreg, true);
+             validate_change (uin, DF_REF_REAL_LOC (use), newreg, true);
            }
        }
 
--- gcc/testsuite/gcc.dg/torture/pr59166.c.jj   2013-11-26 12:49:33.551233602 
+0100
+++ gcc/testsuite/gcc.dg/torture/pr59166.c      2013-11-26 12:50:15.589019973 
+0100
@@ -0,0 +1,37 @@
+/* PR rtl-optimization/59166 */
+/* { dg-additional-options "-fcompare-debug" } */
+
+int a, b, c, f, g;
+
+void
+foo ()
+{
+  for (; b; b++)
+    for (; f; f = g)
+      for (; a;)
+       ;
+}
+
+static int
+bar (int p)
+{
+  short d;
+  if (c)
+    {
+      for (; f; f = g);
+      foo ();
+      d = p;
+      char e = d;
+      if (p)
+       return 1;
+    }
+  return p;
+}
+
+int
+main ()
+{
+  bar (0);
+  bar (g);
+  return 0;
+}

        Jakub