re PR tree-optimization/14470 ([tree-ssa] trouble with post-increment)

	PR middle-end/14470
	* expr.c (mark_queue): New function.
	(emit_insns_enqueued_after_mark): New function replacing
	emit_queue.  Clear the body of emitted queued insns.
	(emit_queue): Call emit_insns_enqueued_after_mark.
	(store_expr): Mark the increment queue on entry.  Emit
	only the incrementations queued when expanding the source.

From-SVN: r79822

gcc/ChangeLog

+2004-03-22  Eric Botcazou  <ebotcazou@libertysurf.fr>
+
+	PR middle-end/14470
+	* expr.c (mark_queue): New function.
+	(emit_insns_enqueued_after_mark): New function replacing
+	emit_queue.  Clear the body of emitted queued insns.
+	(emit_queue): Call emit_insns_enqueued_after_mark.
+	(store_expr): Mark the increment queue on entry.  Emit
+	only the incrementations queued when expanding the source.
+
 2004-03-22  Nathanael Nerode  <neroden@gcc.gnu.org>
 
 	* configure.ac: Allow --disable-coverage-flags (for the future benefit

gcc/expr.c

@@ -466,13 +466,30 @@ queued_subexp_p (rtx x)
     }
 }
 
-/* Perform all the pending incrementations.  */
+/* Retrieve a mark on the queue.  */
+  
+static rtx
+mark_queue (void)
+{
+  return pending_chain;
+}
 
-void
-emit_queue (void)
+/* Perform all the pending incrementations that have been enqueued
+   after MARK was retrieved.  If MARK is null, perform all the
+   pending incrementations.  */
+
+static void
+emit_insns_enqueued_after_mark (rtx mark)
 {
   rtx p;
-  while ((p = pending_chain))
+
+  /* The marked incrementation may have been emitted in the meantime
+     through a call to emit_queue.  In this case, the mark is not valid
+     anymore so do nothing.  */
+  if (mark && ! QUEUED_BODY (mark))
+    return;
+
+  while ((p = pending_chain) != mark)
     {
       rtx body = QUEUED_BODY (p);
 
@@ -499,9 +516,18 @@ emit_queue (void)
 	  break;
 	}
 
+      QUEUED_BODY (p) = 0;
       pending_chain = QUEUED_NEXT (p);
     }
 }
+
+/* Perform all the pending incrementations.  */
+
+void
+emit_queue (void)
+{
+  emit_insns_enqueued_after_mark (NULL_RTX);
+}
 
 /* Copy data from FROM to TO, where the machine modes are not the same.
    Both modes may be integer, or both may be floating.
@@ -4003,6 +4029,7 @@ store_expr (tree exp, rtx target, int want_value)
 {
   rtx temp;
   rtx alt_rtl = NULL_RTX;
+  rtx mark = mark_queue ();
   int dont_return_target = 0;
   int dont_store_target = 0;
 
@@ -4214,7 +4241,11 @@ store_expr (tree exp, rtx target, int want_value)
 			  temp, TREE_UNSIGNED (TREE_TYPE (exp)));
 
   /* If value was not generated in the target, store it there.
-     Convert the value to TARGET's type first if necessary.
+     Convert the value to TARGET's type first if necessary and emit the
+     pending incrementations that have been queued when expanding EXP.
+     Note that we cannot emit the whole queue blindly because this will
+     effectively disable the POST_INC optimization later.
+
      If TEMP and TARGET compare equal according to rtx_equal_p, but
      one or both of them are volatile memory refs, we have to distinguish
      two cases:
@@ -4242,7 +4273,7 @@ store_expr (tree exp, rtx target, int want_value)
 	 bit-initialized.  */
       && expr_size (exp) != const0_rtx)
     {
-      emit_queue();
+      emit_insns_enqueued_after_mark (mark);
       target = protect_from_queue (target, 1);
       temp = protect_from_queue (temp, 0);
       if (GET_MODE (temp) != GET_MODE (target)