* combine.c (simplify_set): Remove an unnecessary subreg.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@53873 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8e2c29e..001ff8a 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2002-05-25  Kazu Hirata  <kazu@cs.umass.edu>
+
+       * combine.c (simplify_set): Remove an unnecessary subreg.
+
 2002-05-25  Marek Michalkiewicz  <marekm@amelek.gda.pl>
 
        * config/avr/avr.c (avr_handle_progmem_attribute): Handle TYPE_DECL.

diff --git a/gcc/combine.c b/gcc/combine.c
index f3cb90f..e1581da 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -5160,6 +5160,30 @@ simplify_set (x)
       src = SET_SRC (x), dest = SET_DEST (x);
     }
 
+#ifdef HAVE_cc0
+  /* If we have (set (cc0) (subreg ...)), we try to remove the subreg
+     in SRC.  */
+  if (dest == cc0_rtx
+      && GET_CODE (src) == SUBREG
+      && subreg_lowpart_p (src)
+      && (GET_MODE_BITSIZE (GET_MODE (src))
+         < GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (src)))))
+    {
+      rtx inner = SUBREG_REG (src);
+      enum machine_mode inner_mode = GET_MODE (inner);
+
+      /* Here we make sure that we don't have a sign bit on.  */
+      if (GET_MODE_BITSIZE (inner_mode) <= HOST_BITS_PER_WIDE_INT
+         && (nonzero_bits (inner, inner_mode)
+             < ((unsigned HOST_WIDE_INT) 1
+                << (GET_MODE_BITSIZE (inner_mode) - 1))))
+       {
+         SUBST (SET_SRC (x), inner);
+         src = SET_SRC (x);
+       }
+    }
+#endif
+
 #ifdef LOAD_EXTEND_OP
   /* If we have (set FOO (subreg:M (mem:N BAR) 0)) with M wider than N, this
      would require a paradoxical subreg.  Replace the subreg with a