re PR target/89188 (ICE in pre_and_rev_post_order_compute, at cfganal.c:1055)

	PR target/89188
	* dce.c (delete_unmarked_insns): Don't remove no-op moves if they
	can throw, non-call exceptions are enabled and we can't delete
	dead exceptions or alter cfg.  Set must_clean if
	delete_insn_and_edges returns true, don't set it blindly for calls.
	Assert that delete_unreachable_blocks is called only if can_alter_cfg.

	* g++.dg/opt/pr89188.C: New test.

From-SVN: r268544

1 files changed, 11 insertions, 9 deletions

diff --git a/gcc/dce.c b/gcc/dce.c
index 7fd9c37..cb18e815 100644
--- a/gcc/dce.c
+++ b/gcc/dce.c
@@ -584,7 +584,12 @@ delete_unmarked_insns (void)
 	  rtx turn_into_use = NULL_RTX;
 
 	  /* Always delete no-op moves.  */
-	  if (noop_move_p (insn))
+	  if (noop_move_p (insn)
+	      /* Unless the no-op move can throw and we are not allowed
+		 to alter cfg.  */
+	      && (!cfun->can_throw_non_call_exceptions
+		  || (cfun->can_delete_dead_exceptions && can_alter_cfg)
+		  || insn_nothrow_p (insn)))
 	    {
 	      if (RTX_FRAME_RELATED_P (insn))
 		turn_into_use
@@ -627,12 +632,6 @@ delete_unmarked_insns (void)
 	     for the destination regs in order to avoid dangling notes.  */
 	  remove_reg_equal_equiv_notes_for_defs (insn);
 
-	  /* If a pure or const call is deleted, this may make the cfg
-	     have unreachable blocks.  We rememeber this and call
-	     delete_unreachable_blocks at the end.  */
-	  if (CALL_P (insn))
-	    must_clean = true;
-
 	  if (turn_into_use)
 	    {
 	      /* Don't remove frame related noop moves if they cary
@@ -645,12 +644,15 @@ delete_unmarked_insns (void)
 	    }
 	  else
 	    /* Now delete the insn.  */
-	    delete_insn_and_edges (insn);
+	    must_clean |= delete_insn_and_edges (insn);
 	}
 
   /* Deleted a pure or const call.  */
   if (must_clean)
-    delete_unreachable_blocks ();
+    {
+      gcc_assert (can_alter_cfg);
+      delete_unreachable_blocks ();
+    }
 }