diff --git a/lib/cretonne/meta/gen_encoding.py b/lib/cretonne/meta/gen_encoding.py
index f19377b8bd..c56db8fc79 100644
--- a/lib/cretonne/meta/gen_encoding.py
+++ b/lib/cretonne/meta/gen_encoding.py
@@ -474,6 +474,15 @@ def emit_recipe_constraints(isa, fmt):
             with fmt.indented('RecipeConstraints {', '},'):
                 emit_operand_constraints(r, r.ins, 'ins', tied_i2o, fmt)
                 emit_operand_constraints(r, r.outs, 'outs', tied_o2i, fmt)
+                fmt.format(
+                        'fixed_ins: {},',
+                        str(any(isinstance(c, Register)
+                            for c in r.ins)).lower())
+                fmt.format(
+                        'fixed_outs: {},',
+                        str(any(isinstance(c, Register)
+                            for c in r.outs)).lower())
+                fmt.format('tied_ops: {},', str(bool(tied_i2o)).lower())
 
 
 def emit_operand_constraints(
diff --git a/lib/cretonne/src/isa/constraints.rs b/lib/cretonne/src/isa/constraints.rs
index fa30fd24fe..e38b044535 100644
--- a/lib/cretonne/src/isa/constraints.rs
+++ b/lib/cretonne/src/isa/constraints.rs
@@ -67,6 +67,15 @@ pub struct RecipeConstraints {
     /// If the instruction produces a variable number of results, it's probably a call and the
     /// constraints must be derived from the calling convention ABI.
     pub outs: &'static [OperandConstraint],
+
+    /// Are any of the input constraints `FixedReg`?
+    pub fixed_ins: bool,
+
+    /// Are any of the output constraints `FixedReg`?
+    pub fixed_outs: bool,
+
+    /// Are there any tied operands?
+    pub tied_ops: bool,
 }
 
 /// Constraints on the range of a branch instruction.