Add x86_push and x86_pop instructions.

lib/cretonne/src/ir/instructions.rs

@@ -120,6 +120,7 @@ pub enum InstructionData {
     },
     Ternary { opcode: Opcode, args: [Value; 3] },
     MultiAry { opcode: Opcode, args: ValueList },
+    NullAry { opcode: Opcode },
     InsertLane {
         opcode: Opcode,
         lane: Uimm8,

lib/cretonne/src/verifier/mod.rs

@@ -359,7 +359,8 @@ impl<'a> Verifier<'a> {
             Store { .. } |
             RegMove { .. } |
             Trap { .. } |
-            CondTrap { .. } => {}
+            CondTrap { .. } |
+            NullAry { .. } => {}
         }
 
         Ok(())

lib/cretonne/src/write.rs

@@ -295,6 +295,7 @@ pub fn write_operands(
                 write!(w, " {}", DisplayValues(args.as_slice(pool)))
             }
         }
+        NullAry { .. } => write!(w, " "),
         InsertLane { lane, args, .. } => write!(w, " {}, {}, {}", args[0], lane, args[1]),
         ExtractLane { lane, arg, .. } => write!(w, " {}, {}", arg, lane),
         IntCompare { cond, args, .. } => write!(w, " {} {}, {}", cond, args[0], args[1]),