flow.c (propagate_block): If block has no successors, stores to frame are dead if not used.

	* flow.c (propagate_block): If block has no successors, stores to
	frame are dead if not used.

From-SVN: r34296

gcc/ChangeLog

+Wed May 31 08:07:52 2000  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
+
+	* flow.c (propagate_block): If block has no successors, stores to
+	frame are dead if not used.
+
 2000-05-31  Nathan Sidwell  <nathan@codesourcery.com>
 
 	* stmt (expand_end_case): Reorder conversion sequence for jump

gcc/flow.c

@@ -3772,6 +3772,26 @@ propagate_block (bb, live, local_set, flags)
 				 { REG_BASIC_BLOCK (i) = REG_BLOCK_GLOBAL; });
     }
 
+  /* If this block has no successors, any stores to the frame that aren't
+     used later in the block are dead.  So make a pass over the block
+     recording any such that are made and show them dead at the end.  We do
+     a very conservative and simple job here.  */
+  if (bb->succ != 0 && bb->succ->succ_next == 0
+      && bb->succ->dest == EXIT_BLOCK_PTR)
+    for (insn = bb->end; insn != bb->head; insn = PREV_INSN (insn))
+      if (GET_CODE (insn) == INSN && GET_CODE (PATTERN (insn)) == SET
+	  && GET_CODE (SET_DEST (PATTERN (insn))) == MEM)
+	{
+	  rtx mem = SET_DEST (PATTERN (insn));
+
+	  if ((GET_CODE (XEXP (mem, 0)) == REG
+	       && REGNO (XEXP (mem, 0)) == FRAME_POINTER_REGNUM)
+	      || (GET_CODE (XEXP (mem, 0)) == PLUS
+		  && GET_CODE (XEXP (XEXP (mem, 0), 0)) == REG
+		  && REGNO (XEXP (XEXP (mem, 0), 0)) == FRAME_POINTER_REGNUM))
+	    pbi->mem_set_list = alloc_EXPR_LIST (0, mem, pbi->mem_set_list);
+	}
+
   /* Scan the block an insn at a time from end to beginning.  */
 
   for (insn = bb->end; ; insn = prev)