re PR debug/65678 (internal compiler error: in gen_rtx_SUBREG, at emit-rtl.c:909)

	PR debug/65678
	* valtrack.c (debug_lowpart_subreg): New function.
	(dead_debug_insert_temp): Use it.

	* g++.dg/debug/pr65678.C: New test.

From-SVN: r221900

gcc/ChangeLog

 2015-04-07  Jakub Jelinek  <jakub@redhat.com>
 
+	PR debug/65678
+	* valtrack.c (debug_lowpart_subreg): New function.
+	(dead_debug_insert_temp): Use it.
+
 	PR middle-end/65680
 	* expr.c (get_inner_reference): Handle bit_offset that doesn't fit
 	into signed HOST_WIDE_INT the same as negative bit_offset.

gcc/testsuite/ChangeLog

 2015-04-07  Jakub Jelinek  <jakub@redhat.com>
 
+	PR debug/65678
+	* g++.dg/debug/pr65678.C: New test.
+
 	PR middle-end/65680
 	* gcc.c-torture/compile/pr65680.c: New test.
 

gcc/testsuite/g++.dg/debug/pr65678.C

+// PR debug/65678
+// { dg-do compile }
+
+long long v;
+
+static int
+bar (double x)
+{
+#if __SIZEOF_DOUBLE__ == __SIZEOF_LONG_LONG__
+  __builtin_memmove (&v, &x, sizeof v);
+#else
+  (void) x;
+  v = 0;
+#endif
+  return v;
+}
+
+struct A
+{
+  A (double x) : a (bar (x)) {}
+  int m1 ();
+  int m2 () { int b = a; return b; }
+  int a;
+};
+
+void foo ();
+
+void
+baz (double x)
+{
+  int c = A (x).m2 ();
+  int d = A (x).m1 ();
+  if (d)
+    foo ();
+}

gcc/valtrack.c

@@ -534,6 +534,22 @@ dead_debug_add (struct dead_debug_local *debug, df_ref use, unsigned int uregno)
   bitmap_set_bit (debug->used, uregno);
 }
 
+/* Like lowpart_subreg, but if a subreg is not valid for machine, force
+   it anyway - for use in debug insns.  */
+
+static rtx
+debug_lowpart_subreg (machine_mode outer_mode, rtx expr,
+		      machine_mode inner_mode)
+{
+  if (inner_mode == VOIDmode)
+    inner_mode = GET_MODE (expr);
+  int offset = subreg_lowpart_offset (outer_mode, inner_mode);
+  rtx ret = simplify_gen_subreg (outer_mode, expr, inner_mode, offset);
+  if (ret)
+    return ret;
+  return gen_rtx_raw_SUBREG (outer_mode, expr, offset);
+}
+
 /* If UREGNO is referenced by any entry in DEBUG, emit a debug insn
    before or after INSN (depending on WHERE), that binds a (possibly
    global) debug temp to the widest-mode use of UREGNO, if WHERE is
@@ -662,9 +678,9 @@ dead_debug_insert_temp (struct dead_debug_local *debug, unsigned int uregno,
 	  /* Ok, it's the same (hardware) REG, but with a different
 	     mode, so SUBREG it.  */
 	  else
-	    breg = lowpart_subreg (GET_MODE (reg),
-				   cleanup_auto_inc_dec (src, VOIDmode),
-				   GET_MODE (dest));
+	    breg = debug_lowpart_subreg (GET_MODE (reg),
+					 cleanup_auto_inc_dec (src, VOIDmode),
+					 GET_MODE (dest));
 	}
       else if (GET_CODE (dest) == SUBREG)
 	{
@@ -684,9 +700,9 @@ dead_debug_insert_temp (struct dead_debug_local *debug, unsigned int uregno,
 	    breg = NULL;
 	  /* Yay, we can use SRC, just adjust its mode.  */
 	  else
-	    breg = lowpart_subreg (GET_MODE (reg),
-				   cleanup_auto_inc_dec (src, VOIDmode),
-				   GET_MODE (dest));
+	    breg = debug_lowpart_subreg (GET_MODE (reg),
+					 cleanup_auto_inc_dec (src, VOIDmode),
+					 GET_MODE (dest));
 	}
       /* Oh well, we're out of luck.  */
       else
@@ -740,7 +756,8 @@ dead_debug_insert_temp (struct dead_debug_local *debug, unsigned int uregno,
 	*DF_REF_REAL_LOC (cur->use) = dval;
       else
 	*DF_REF_REAL_LOC (cur->use)
-	  = gen_lowpart_SUBREG (GET_MODE (*DF_REF_REAL_LOC (cur->use)), dval);
+	  = debug_lowpart_subreg (GET_MODE (*DF_REF_REAL_LOC (cur->use)), dval,
+				  GET_MODE (dval));
       /* ??? Should we simplify subreg of subreg?  */
       bitmap_set_bit (debug->to_rescan, INSN_UID (DF_REF_INSN (cur->use)));
       uses = cur->next;