Merge from rewrite branch.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@66318 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 11 insertions, 1 deletions

diff --git a/gcc/combine.c b/gcc/combine.c
index f7c98526833..6e3bbb2fb56 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -1437,7 +1437,7 @@ cant_combine_insn_p (insn)
 
   /* Never combine loads and stores involving hard regs that are likely
      to be spilled.  The register allocator can usually handle such
-     reg-reg moves by tying.  If we allow the combiner to make 
+     reg-reg moves by tying.  If we allow the combiner to make
      substitutions of likely-spilled regs, we may abort in reload.
      As an exception, we allow combinations involving fixed regs; these are
      not available to the register allocator so there's no risk involved.  */
@@ -10159,6 +10159,14 @@ gen_lowpart_for_combine (mode, x)
   if (GET_MODE (x) == mode)
     return x;
 
+  /* Return identity if this is a CONST or symbolic
+     reference.  */
+  if (mode == Pmode
+      && (GET_CODE (x) == CONST
+	  || GET_CODE (x) == SYMBOL_REF
+	  || GET_CODE (x) == LABEL_REF))
+    return x;
+
   /* We can only support MODE being wider than a word if X is a
      constant integer or has a mode the same size.  */
 
@@ -10242,6 +10250,8 @@ gen_lowpart_for_combine (mode, x)
 	{
 	  sub_mode = int_mode_for_mode (mode);
 	  x = gen_lowpart_common (sub_mode, x);
+	  if (x == 0)
+	    return gen_rtx_CLOBBER (VOIDmode, const0_rtx);
 	}
       res = simplify_gen_subreg (mode, x, sub_mode, offset);
       if (res)