(cse_insn): Don't record a DEST a paradoxical SUBREG and SRC is a

SIGN_EXTEND or ZERO_EXTEND.

From-SVN: r8354

gcc/cse.c

@@ -7188,7 +7188,17 @@ cse_insn (insn, in_libcall_block)
 	    || in_libcall_block
 	    /* If we didn't put a REG_EQUAL value or a source into the hash
 	       table, there is no point is recording DEST.  */
-	     || sets[i].src_elt == 0)
+	    || sets[i].src_elt == 0
+	    /* If DEST is a paradoxical SUBREG and SRC is a ZERO_EXTEND
+	       or SIGN_EXTEND, don't record DEST since it can cause
+	       some tracking to be wrong.
+
+	       ??? Think about this more later.  */
+	    || (GET_CODE (dest) == SUBREG
+		&& (GET_MODE_SIZE (GET_MODE (dest))
+		    > GET_MODE_SIZE (GET_MODE (SUBREG_REG (dest))))
+		&& (GET_CODE (sets[i].src) == SIGN_EXTEND
+		    || GET_CODE (sets[i].src) == ZERO_EXTEND)))
 	  continue;
 
 	/* STRICT_LOW_PART isn't part of the value BEING set,