[PATCH GCC][4/6]Simple patch skips single element component

[Bin Cheng]

Hi,
This is a simple patch discarding simple element components earlier in predcom.
Bootstrap and test on x86_64 and AArch64, is it OK?

Thanks,
bin
2017-05-10  Bin Cheng  <bin.ch...@arm.com>

        * tree-predcom.c (determine_roots_comp): Skip single-elem chain.
From fd3dd235dca80671d1201098c9235a17b5a2f544 Mon Sep 17 00:00:00 2001
From: Bin Cheng <binch...@e108451-lin.cambridge.arm.com>
Date: Mon, 24 Apr 2017 14:47:25 +0100
Subject: [PATCH 4/6] skip-single-elem-component-20161221.txt

---
 gcc/tree-predcom.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/gcc/tree-predcom.c b/gcc/tree-predcom.c
index 96af63f..0b7811a 100644
--- a/gcc/tree-predcom.c
+++ b/gcc/tree-predcom.c
@@ -1229,8 +1229,11 @@ determine_roots_comp (struct loop *loop,
       return;
     }
 
-  comp->refs.qsort (order_drefs);
+  /* Trivial component.  */
+  if (comp->refs.length () <= 1)
+    return;
 
+  comp->refs.qsort (order_drefs);
   FOR_EACH_VEC_ELT (comp->refs, i, a)
     {
       if (!chain || DR_IS_WRITE (a->ref)
-- 
1.9.1