LRA: side_effects_p stmts' output is not invariant (PR89721)

PR89721 shows LRA treating an unspec_volatile's result as invariant,
which of course isn't correct.  This patch fixes it.


	PR rtl-optimization/89721
	* lra-constraints (invariant_p): Return false if side_effects_p holds.

From-SVN: r269716

gcc/ChangeLog

+2019-03-15  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/89721
+	* lra-constraints (invariant_p): Return false if side_effects_p holds.
+
 2019-03-15  Kelvin Nilsen  <kelvin@gcc.gnu.org>
 
 	PR target/87532

gcc/lra-constraints.c

@@ -5839,6 +5839,9 @@ invariant_p (const_rtx x)
   enum rtx_code code;
   int i, j;
 
+  if (side_effects_p (x))
+    return false;
+
   code = GET_CODE (x);
   mode = GET_MODE (x);
   if (code == SUBREG)