(final_scan_insn): Allow removal of redundant test and compare

instructions that use clobbers.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@11806 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/final.c b/gcc/final.c
index 882850f..70aa819 100644 (file)
--- a/gcc/final.c
+++ b/gcc/final.c
@@ -1756,35 +1756,39 @@ final_scan_insn (insn, file, optimize, prescan, nopeepholes)
           and the next statement should reexamine the variable
           to compute the condition codes.  */
 
-       if (optimize
-           && GET_CODE (body) == SET
-           && GET_CODE (SET_DEST (body)) == CC0
-           && insn != last_ignored_compare)
+       if (optimize)
          {
-           if (GET_CODE (SET_SRC (body)) == SUBREG)
-             SET_SRC (body) = alter_subreg (SET_SRC (body));
-           else if (GET_CODE (SET_SRC (body)) == COMPARE)
-             {
-               if (GET_CODE (XEXP (SET_SRC (body), 0)) == SUBREG)
-                 XEXP (SET_SRC (body), 0)
-                   = alter_subreg (XEXP (SET_SRC (body), 0));
-               if (GET_CODE (XEXP (SET_SRC (body), 1)) == SUBREG)
-                 XEXP (SET_SRC (body), 1)
-                   = alter_subreg (XEXP (SET_SRC (body), 1));
-             }
-           if ((cc_status.value1 != 0
-                && rtx_equal_p (SET_SRC (body), cc_status.value1))
-               || (cc_status.value2 != 0
-                   && rtx_equal_p (SET_SRC (body), cc_status.value2)))
+           rtx set = single_set(insn);
+
+           if (set
+               && GET_CODE (SET_DEST (set)) == CC0
+               && insn != last_ignored_compare)
              {
-               /* Don't delete insn if it has an addressing side-effect.  */
-               if (! FIND_REG_INC_NOTE (insn, 0)
-                   /* or if anything in it is volatile.  */
-                   && ! volatile_refs_p (PATTERN (insn)))
+               if (GET_CODE (SET_SRC (set)) == SUBREG)
+                 SET_SRC (set) = alter_subreg (SET_SRC (set));
+               else if (GET_CODE (SET_SRC (set)) == COMPARE)
                  {
-                   /* We don't really delete the insn; just ignore it.  */
-                   last_ignored_compare = insn;
-                   break;
+                   if (GET_CODE (XEXP (SET_SRC (set), 0)) == SUBREG)
+                     XEXP (SET_SRC (set), 0)
+                       = alter_subreg (XEXP (SET_SRC (set), 0));
+                   if (GET_CODE (XEXP (SET_SRC (set), 1)) == SUBREG)
+                     XEXP (SET_SRC (set), 1)
+                       = alter_subreg (XEXP (SET_SRC (set), 1));
+                 }
+               if ((cc_status.value1 != 0
+                    && rtx_equal_p (SET_SRC (set), cc_status.value1))
+                   || (cc_status.value2 != 0
+                       && rtx_equal_p (SET_SRC (set), cc_status.value2)))
+                 {
+                   /* Don't delete insn if it has an addressing side-effect.  */
+                   if (! FIND_REG_INC_NOTE (insn, 0)
+                       /* or if anything in it is volatile.  */
+                       && ! volatile_refs_p (PATTERN (insn)))
+                     {
+                       /* We don't really delete the insn; just ignore it.  */
+                       last_ignored_compare = insn;
+                       break;
+                     }
                  }
              }
          }