diff --git a/lib/cretonne/meta/base/formats.py b/lib/cretonne/meta/base/formats.py
index 4e1ff3500a..1961d9d4a9 100644
--- a/lib/cretonne/meta/base/formats.py
+++ b/lib/cretonne/meta/base/formats.py
@@ -32,6 +32,8 @@ Ternary = InstructionFormat(VALUE, VALUE, VALUE, typevar_operand=1)
 # operands.
 MultiAry = InstructionFormat(VARIABLE_ARGS)
 
+NullAry = InstructionFormat()
+
 InsertLane = InstructionFormat(VALUE, ('lane', uimm8), VALUE)
 ExtractLane = InstructionFormat(VALUE, ('lane', uimm8))
 
diff --git a/lib/cretonne/meta/isa/intel/instructions.py b/lib/cretonne/meta/isa/intel/instructions.py
index 27a0063557..3389f77708 100644
--- a/lib/cretonne/meta/isa/intel/instructions.py
+++ b/lib/cretonne/meta/isa/intel/instructions.py
@@ -99,4 +99,17 @@ fmax = Instruction(
         """,
         ins=(x, y), outs=a)
 
+WideInt = TypeVar(
+        'WideInt', 'An integer type with 16 to 64 bits',
+        ints=(16, 64))
+x = Operand('x', WideInt)
+
+push = Instruction(
+    'x86_push', "Pushes onto the stack.",
+    ins=x, can_store=True, other_side_effects=True)
+
+pop = Instruction(
+    'x86_pop', "Pops from the stack.",
+    outs=x, can_load=True, other_side_effects=True)
+
 GROUP.close()
diff --git a/lib/cretonne/src/ir/instructions.rs b/lib/cretonne/src/ir/instructions.rs
index f110cd14db..c474258f37 100644
--- a/lib/cretonne/src/ir/instructions.rs
+++ b/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,
diff --git a/lib/cretonne/src/verifier/mod.rs b/lib/cretonne/src/verifier/mod.rs
index 2144264f40..6b67ed1bed 100644
--- a/lib/cretonne/src/verifier/mod.rs
+++ b/lib/cretonne/src/verifier/mod.rs
@@ -359,7 +359,8 @@ impl<'a> Verifier<'a> {
             Store { .. } |
             RegMove { .. } |
             Trap { .. } |
-            CondTrap { .. } => {}
+            CondTrap { .. } |
+            NullAry { .. } => {}
         }
 
         Ok(())
diff --git a/lib/cretonne/src/write.rs b/lib/cretonne/src/write.rs
index 9de3e93d58..1604ca559a 100644
--- a/lib/cretonne/src/write.rs
+++ b/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]),
diff --git a/lib/reader/src/parser.rs b/lib/reader/src/parser.rs
index d809cd192c..b96cba20b2 100644
--- a/lib/reader/src/parser.rs
+++ b/lib/reader/src/parser.rs
@@ -1955,6 +1955,7 @@ impl<'a> Parser<'a> {
                     args: args.into_value_list(&[], &mut ctx.function.dfg.value_lists),
                 }
             }
+            InstructionFormat::NullAry => InstructionData::NullAry { opcode },
             InstructionFormat::Jump => {
                 // Parse the destination EBB number. Don't translate source to local numbers yet.
                 let ebb_num = self.match_ebb("expected jump destination EBB")?;