[backport from gcc-4.8/trunk r190102 <mikpe@it.uu.se>]

From: Richard Sandiford <rdsandiford at googlemail dot com>
Subject: [committed] Fix rtx-sharing problem in split_insns
Date: Thu, 02 Aug 2012 21:44:56 +0100
List-Archive: <http://gcc.gnu.org/ml/gcc-patches/>

I hit a case where we were splitting a set of (const (unspec [...]))
into something that still referred to the original expression.
We reused that same expression as a REG_EQUAL note, leading to
an rtx-sharing violation.

Tested on mips64-linux-gnu and applied.

Richard

gcc/

2012-08-02  Richard Sandiford  <rdsandiford@googlemail.com>

	* recog.c (split_insn): Copy the original SET_SRC before using
	it as a note.

--- gcc-4.6.3/gcc/recog.c.~1~	2012-01-15 20:35:15.000000000 +0100
+++ gcc-4.6.3/gcc/recog.c	2012-08-11 15:57:46.000000000 +0200
@@ -2798,7 +2798,8 @@ split_insn (rtx insn)
 	  if (note && CONSTANT_P (XEXP (note, 0)))
 	    set_unique_reg_note (last, REG_EQUAL, XEXP (note, 0));
 	  else if (CONSTANT_P (SET_SRC (insn_set)))
-	    set_unique_reg_note (last, REG_EQUAL, SET_SRC (insn_set));
+	    set_unique_reg_note (last, REG_EQUAL,
+				 copy_rtx (SET_SRC (insn_set)));
 	}
     }