cranelift: Add narrower and wider constraints to the instruction DSL (#6013)

* Add narrower and wider constraints to the instruction DSL

* Add docs to narrower/wider operands

* Update cranelift/codegen/meta/src/cdsl/instructions.rs

Co-authored-by: Jamey Sharp <jamey@minilop.net>

* Fix assertion message

* Simplify upper bounds for the wider constraint

* Remove additional unnecessary cases in the verifier

* Remove unused variables

* Remove changes to is_ctrl_typevar_candidate

These changes were only necessary when the type returned by an
instruction was a variable constrained by narrow or widen. As we have
switched to requiring that constraints must appear on argument types and
not return types, these changes were not longer necessary.

---------

Co-authored-by: Jamey Sharp <jamey@minilop.net>

cranelift/codegen/meta/src/cdsl/typevar.rs

@@ -202,6 +202,32 @@ impl TypeVar {
                     "can't halve a scalar type"
                 );
             }
+            DerivedFunc::Narrower => {
+                assert_eq!(
+                    *ts.lanes.iter().max().unwrap(),
+                    1,
+                    "The `narrower` constraint does not apply to vectors"
+                );
+                assert!(
+                    (!ts.ints.is_empty() || !ts.floats.is_empty())
+                        && ts.refs.is_empty()
+                        && ts.dynamic_lanes.is_empty(),
+                    "The `narrower` constraint only applies to scalar ints or floats"
+                );
+            }
+            DerivedFunc::Wider => {
+                assert_eq!(
+                    *ts.lanes.iter().max().unwrap(),
+                    1,
+                    "The `wider` constraint does not apply to vectors"
+                );
+                assert!(
+                    (!ts.ints.is_empty() || !ts.floats.is_empty())
+                        && ts.refs.is_empty()
+                        && ts.dynamic_lanes.is_empty(),
+                    "The `wider` constraint only applies to scalar ints or floats"
+                );
+            }
             DerivedFunc::LaneOf | DerivedFunc::AsBool | DerivedFunc::DynamicToVector => {
                 /* no particular assertions */
             }
@@ -241,6 +267,16 @@ impl TypeVar {
     pub fn dynamic_to_vector(&self) -> TypeVar {
         self.derived(DerivedFunc::DynamicToVector)
     }
+
+    /// Make a new [TypeVar] that includes all types narrower than self.
+    pub fn narrower(&self) -> TypeVar {
+        self.derived(DerivedFunc::Narrower)
+    }
+
+    /// Make a new [TypeVar] that includes all types wider than self.
+    pub fn wider(&self) -> TypeVar {
+        self.derived(DerivedFunc::Wider)
+    }
 }
 
 impl Into<TypeVar> for &TypeVar {
@@ -302,6 +338,8 @@ pub(crate) enum DerivedFunc {
     SplitLanes,
     MergeLanes,
     DynamicToVector,
+    Narrower,
+    Wider,
 }
 
 impl DerivedFunc {
@@ -314,6 +352,8 @@ impl DerivedFunc {
             DerivedFunc::SplitLanes => "split_lanes",
             DerivedFunc::MergeLanes => "merge_lanes",
             DerivedFunc::DynamicToVector => "dynamic_to_vector",
+            DerivedFunc::Narrower => "narrower",
+            DerivedFunc::Wider => "wider",
         }
     }
 }
@@ -391,6 +431,8 @@ impl TypeSet {
             DerivedFunc::SplitLanes => self.half_width().double_vector(),
             DerivedFunc::MergeLanes => self.double_width().half_vector(),
             DerivedFunc::DynamicToVector => self.dynamic_to_vector(),
+            DerivedFunc::Narrower => self.clone(),
+            DerivedFunc::Wider => self.clone(),
         }
     }
 

cranelift/codegen/meta/src/shared/instructions.rs

@@ -3064,12 +3064,6 @@ pub(crate) fn define(
         TypeSetBuilder::new().ints(Interval::All).build(),
     );
 
-    let IntTo = &TypeVar::new(
-        "IntTo",
-        "A smaller integer type",
-        TypeSetBuilder::new().ints(Interval::All).build(),
-    );
-
     ig.push(
         Inst::new(
             "ireduce",
@@ -3081,8 +3075,9 @@ pub(crate) fn define(
         "#,
             &formats.unary,
         )
-        .operands_in(vec![Operand::new("x", Int)])
+        .operands_in(vec![Operand::new("x", &Int.wider())
-        .operands_out(vec![Operand::new("a", IntTo)]),
+            .with_doc("A scalar integer type, wider than the controlling type")])
+        .operands_out(vec![Operand::new("a", Int)]),
     );
 
     let I16or32or64xN = &TypeVar::new(
@@ -3272,13 +3267,6 @@ pub(crate) fn define(
         .operands_out(vec![Operand::new("a", I16x8)]),
     );
 
-    {
-        let IntTo = &TypeVar::new(
-            "IntTo",
-            "A larger integer type with the same number of lanes",
-            TypeSetBuilder::new().ints(Interval::All).build(),
-        );
-
     ig.push(
         Inst::new(
             "uextend",
@@ -3295,8 +3283,10 @@ pub(crate) fn define(
         "#,
             &formats.unary,
         )
-            .operands_in(vec![Operand::new("x", Int)])
+        .operands_in(vec![Operand::new("x", &Int.narrower()).with_doc(
-            .operands_out(vec![Operand::new("a", IntTo)]),
+            "A scalar integer type, narrower than the controlling type",
+        )])
+        .operands_out(vec![Operand::new("a", Int)]),
     );
 
     ig.push(
@@ -3315,10 +3305,11 @@ pub(crate) fn define(
         "#,
             &formats.unary,
         )
-            .operands_in(vec![Operand::new("x", Int)])
+        .operands_in(vec![Operand::new("x", &Int.narrower()).with_doc(
-            .operands_out(vec![Operand::new("a", IntTo)]),
+            "A scalar integer type, narrower than the controlling type",
+        )])
+        .operands_out(vec![Operand::new("a", Int)]),
     );
-    }
 
     let FloatScalar = &TypeVar::new(
         "FloatScalar",
@@ -3326,12 +3317,6 @@ pub(crate) fn define(
         TypeSetBuilder::new().floats(Interval::All).build(),
     );
 
-    let FloatScalarTo = &TypeVar::new(
-        "FloatScalarTo",
-        "A scalar only floating point number",
-        TypeSetBuilder::new().floats(Interval::All).build(),
-    );
-
     ig.push(
         Inst::new(
             "fpromote",
@@ -3349,8 +3334,10 @@ pub(crate) fn define(
         "#,
             &formats.unary,
         )
-        .operands_in(vec![Operand::new("x", FloatScalar)])
+        .operands_in(vec![Operand::new("x", &FloatScalar.narrower()).with_doc(
-        .operands_out(vec![Operand::new("a", FloatScalarTo)]),
+            "A scalar only floating point number, narrower than the controlling type",
+        )])
+        .operands_out(vec![Operand::new("a", FloatScalar)]),
     );
 
     ig.push(
@@ -3370,8 +3357,10 @@ pub(crate) fn define(
         "#,
             &formats.unary,
         )
-        .operands_in(vec![Operand::new("x", FloatScalar)])
+        .operands_in(vec![Operand::new("x", &FloatScalar.wider()).with_doc(
-        .operands_out(vec![Operand::new("a", FloatScalarTo)]),
+            "A scalar only floating point number, wider than the controlling type",
+        )])
+        .operands_out(vec![Operand::new("a", FloatScalar)]),
     );
 
     let F64x2 = &TypeVar::new(

cranelift/codegen/src/bitset.rs

@@ -11,7 +11,7 @@ use core::mem::size_of;
 use core::ops::{Add, BitOr, Shl, Sub};
 
 /// A small bitset built on a single primitive integer type
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
 #[cfg_attr(feature = "enable-serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct BitSet<T>(pub T);
 

cranelift/codegen/src/ir/instructions.rs

@@ -575,12 +575,9 @@ impl OpcodeConstraints {
     /// `ctrl_type`.
     pub fn result_type(self, n: usize, ctrl_type: Type) -> Type {
         debug_assert!(n < self.num_fixed_results(), "Invalid result index");
-        if let ResolvedConstraint::Bound(t) =
+        match OPERAND_CONSTRAINTS[self.constraint_offset() + n].resolve(ctrl_type) {
-            OPERAND_CONSTRAINTS[self.constraint_offset() + n].resolve(ctrl_type)
+            ResolvedConstraint::Bound(t) => t,
-        {
+            ResolvedConstraint::Free(ts) => panic!("Result constraints can't be free: {:?}", ts),
-            t
-        } else {
-            panic!("Result constraints can't be free");
         }
     }
 
@@ -614,7 +611,7 @@ type BitSet8 = BitSet<u8>;
 type BitSet16 = BitSet<u16>;
 
 /// A value type set describes the permitted set of types for a type variable.
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
 pub struct ValueTypeSet {
     /// Allowed lane sizes
     pub lanes: BitSet16,
@@ -703,6 +700,12 @@ enum OperandConstraint {
 
     /// This operands is `ctrlType.dynamic_to_vector()`.
     DynamicToVector,
+
+    /// This operand is `ctrlType.narrower()`.
+    Narrower,
+
+    /// This operand is `ctrlType.wider()`.
+    Wider,
 }
 
 impl OperandConstraint {
@@ -766,6 +769,47 @@ impl OperandConstraint {
                     .dynamic_to_vector()
                     .expect("invalid type for dynamic_to_vector"),
             ),
+            Narrower => {
+                let ctrl_type_bits = ctrl_type.log2_lane_bits();
+                let mut tys = ValueTypeSet::default();
+
+                // We're testing scalar values, only.
+                tys.lanes = BitSet::from_range(0, 1);
+
+                if ctrl_type.is_int() {
+                    // The upper bound in from_range is exclusive, so add one here get the closed
+                    // interval of [I8, ctrl_type].
+                    tys.ints = BitSet::from_range(3, ctrl_type_bits as u8 + 1);
+                } else if ctrl_type.is_float() {
+                    // The upper bound in from_range is exclusive, so add one here get the closed
+                    // interval of [F32, ctrl_type].
+                    tys.floats = BitSet::from_range(5, ctrl_type_bits as u8 + 1);
+                } else {
+                    panic!("The Narrower constraint only operates on floats or ints");
+                }
+                ResolvedConstraint::Free(tys)
+            }
+            Wider => {
+                let ctrl_type_bits = ctrl_type.log2_lane_bits();
+                let mut tys = ValueTypeSet::default();
+
+                // We're testing scalar values, only.
+                tys.lanes = BitSet::from_range(0, 1);
+
+                if ctrl_type.is_int() {
+                    // The upper bound should include all types wider than `ctrl_type`, so we use
+                    // `2^8` as the upper bound to define the closed range `[ctrl_type, I128]`.
+                    tys.ints = BitSet::from_range(ctrl_type_bits as u8, 8);
+                } else if ctrl_type.is_float() {
+                    // The upper bound should include all float types wider than `ctrl_type`, so we
+                    // use `2^7` as the upper bound to define the closed range `[ctrl_type, F64]`.
+                    tys.floats = BitSet::from_range(ctrl_type_bits as u8, 7);
+                } else {
+                    panic!("The Wider constraint only operates on floats or ints");
+                }
+
+                ResolvedConstraint::Free(tys)
+            }
         }
     }
 }

cranelift/codegen/src/verifier/mod.rs

@@ -1191,7 +1191,7 @@ impl<'a> Verifier<'a> {
         let _ = self.typecheck_fixed_args(inst, ctrl_type, errors);
         let _ = self.typecheck_variable_args(inst, errors);
         let _ = self.typecheck_return(inst, errors);
-        let _ = self.typecheck_special(inst, ctrl_type, errors);
+        let _ = self.typecheck_special(inst, errors);
 
         Ok(())
     }
@@ -1478,63 +1478,8 @@ impl<'a> Verifier<'a> {
 
     // Check special-purpose type constraints that can't be expressed in the normal opcode
     // constraints.
-    fn typecheck_special(
+    fn typecheck_special(&self, inst: Inst, errors: &mut VerifierErrors) -> VerifierStepResult<()> {
-        &self,
-        inst: Inst,
-        ctrl_type: Type,
-        errors: &mut VerifierErrors,
-    ) -> VerifierStepResult<()> {
         match self.func.dfg.insts[inst] {
-            ir::InstructionData::Unary { opcode, arg } => {
-                let arg_type = self.func.dfg.value_type(arg);
-                match opcode {
-                    Opcode::Uextend | Opcode::Sextend | Opcode::Fpromote => {
-                        if arg_type.lane_count() != ctrl_type.lane_count() {
-                            return errors.nonfatal((
-                                inst,
-                                self.context(inst),
-                                format!(
-                                    "input {} and output {} must have same number of lanes",
-                                    arg_type, ctrl_type,
-                                ),
-                            ));
-                        }
-                        if arg_type.lane_bits() >= ctrl_type.lane_bits() {
-                            return errors.nonfatal((
-                                inst,
-                                self.context(inst),
-                                format!(
-                                    "input {} must be smaller than output {}",
-                                    arg_type, ctrl_type,
-                                ),
-                            ));
-                        }
-                    }
-                    Opcode::Ireduce | Opcode::Fdemote => {
-                        if arg_type.lane_count() != ctrl_type.lane_count() {
-                            return errors.nonfatal((
-                                inst,
-                                self.context(inst),
-                                format!(
-                                    "input {} and output {} must have same number of lanes",
-                                    arg_type, ctrl_type,
-                                ),
-                            ));
-                        }
-                        if arg_type.lane_bits() <= ctrl_type.lane_bits() {
-                            return errors.nonfatal((
-                                inst,
-                                self.context(inst),
-                                format!(
-                                    "input {} must be larger than output {}",
-                                    arg_type, ctrl_type,
-                                ),
-                            ));
-                        }
-                    }
-                    _ => {}
-                }
-            }
             ir::InstructionData::TableAddr { table, arg, .. } => {
                 let index_type = self.func.dfg.value_type(arg);
                 let table_index_type = self.func.tables[table].index_type;

cranelift/filetests/filetests/verifier/type_check.clif

@@ -113,14 +113,28 @@ block2(v3: f32, v4: i8):
 function %bad_extend() {
 block0:
     v0 = iconst.i32 10
-    v1 = uextend.i16 v0 ; error: input i32 must be smaller than output i16
+    v1 = uextend.i16 v0 ; error: arg 0 (v0) with type i32 failed to satisfy type set
     return
 }
 
 function %bad_reduce() {
 block0:
     v0 = iconst.i32 10
-    v1 = ireduce.i64 v0 ; error: input i32 must be larger than output i64
+    v1 = ireduce.i64 v0 ; error: arg 0 (v0) with type i32 failed to satisfy type set
+    return
+}
+
+function %bad_fdemote() {
+block0:
+    v0 = f32const 0xf.f
+    v1 = fdemote.f64 v0 ; error: arg 0 (v0) with type f32 failed to satisfy type set
+    return
+}
+
+function %bad_fpromote() {
+block0:
+    v0 = f64const 0xf.f
+    v1 = fpromote.f32 v0 ; error: arg 0 (v0) with type f64 failed to satisfy type set
     return
 }