(update_flow_info): When add extra REG_DEAD note for original dest...

(update_flow_info): When add extra REG_DEAD note for original
dest, handle case where last insn both uses and sets dest.

From-SVN: r14163

diff --git a/gcc/sched.c b/gcc/sched.c
index 78f9b21d384486d0ea26ad45f90b461c27b03ac0..8d258442db969d65d6575eeb3f4723cf3fef5678 100644 (file)
--- a/gcc/sched.c
+++ b/gcc/sched.c
@@ -4577,10 +4577,7 @@ update_flow_info (notes, first, last, orig_insn)
   /* If any insn, except the last, uses the register set by the last insn,
      then we need a new REG_DEAD note on that insn.  In this case, there
      would not have been a REG_DEAD note for this register in the original
-     insn because it was used and set within one insn.
-
-     There is no new REG_DEAD note needed if the last insn uses the register
-     that it is setting.  */
+     insn because it was used and set within one insn.  */
 
   set = single_set (last);
   if (set)
@@ -4596,10 +4593,31 @@ update_flow_info (notes, first, last, orig_insn)
          /* Global registers are always live, so the code below does not
             apply to them.  */
          && (REGNO (dest) >= FIRST_PSEUDO_REGISTER
-             || ! global_regs[REGNO (dest)])
-         && ! reg_overlap_mentioned_p (dest, SET_SRC (set)))
+             || ! global_regs[REGNO (dest)]))
        {
-         for (insn = PREV_INSN (last); ; insn = PREV_INSN (insn))
+         rtx stop_insn = PREV_INSN (first);
+
+         /* If the last insn uses the register that it is setting, then
+            we don't want to put a REG_DEAD note there.  Search backwards
+            to find the first insn that sets but does not use DEST.  */
+
+         insn = last;
+         if (reg_overlap_mentioned_p (dest, SET_SRC (set)))
+           {
+             for (insn = PREV_INSN (insn); insn != first;
+                  insn = PREV_INSN (insn))
+               {
+                 if ((set = single_set (insn))
+                     && reg_mentioned_p (dest, SET_DEST (set))
+                     && ! reg_overlap_mentioned_p (dest, SET_SRC (set)))
+                   break;
+               }
+           }
+
+         /* Now find the first insn that uses but does not set DEST.  */
+
+         for (insn = PREV_INSN (insn); insn != stop_insn;
+              insn = PREV_INSN (insn))
            {
              if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
                  && reg_mentioned_p (dest, PATTERN (insn))
@@ -4625,8 +4643,6 @@ update_flow_info (notes, first, last, orig_insn)
                      break;
                    }
                }
-             if (insn == first)
-               break;
            }
        }
     }