checkpoint; builds again

This commit is contained in:
2023-12-02 22:38:44 -08:00
parent 71228b9e09
commit 93cac44a99
16 changed files with 1200 additions and 1194 deletions

View File

@@ -1,15 +1,15 @@
use std::collections::HashMap;
use crate::eval::PrimitiveType;
use crate::ir::{Expression, Primitive, Program, Statement, TopLevel, Type, Value, ValueOrRef};
use crate::syntax::ConstantType;
use cranelift_codegen::entity::EntityRef;
use crate::ir::{Expression, Primitive, Program, TopLevel, Type, Value, ValueOrRef, Variable};
use crate::syntax::{ConstantType, Location};
use crate::util::scoped_map::ScopedMap;
use cranelift_codegen::ir::{
self, entities, types, Function, GlobalValue, InstBuilder, MemFlags, Signature, UserFuncName,
self, entities, types, AbiParam, Function, GlobalValue, InstBuilder, Signature, UserFuncName,
};
use cranelift_codegen::isa::CallConv;
use cranelift_codegen::Context;
use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext, Variable};
use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
use cranelift_module::{FuncId, Linkage, Module};
use internment::ArcIntern;
@@ -24,25 +24,101 @@ use crate::backend::Backend;
/// This just a handy type alias to avoid a lot of confusion in the functions.
type StringTable = HashMap<ArcIntern<String>, GlobalValue>;
/// When we're talking about variables, it's handy to just have a table that points
/// from a variable to "what to do if you want to reference this variable", which is
/// agnostic about whether the variable is local, global, an argument, etc. Since
/// the type of that function is a little bit annoying, we summarize it here.
struct ReferenceBuilder {
ir_type: ConstantType,
cranelift_type: cranelift_codegen::ir::Type,
local_data: GlobalValue,
}
impl ReferenceBuilder {
fn refer_to(&self, builder: &mut FunctionBuilder) -> (entities::Value, ConstantType) {
let value = builder.ins().symbol_value(self.cranelift_type, self.local_data);
(value, self.ir_type)
}
}
impl<M: Module> Backend<M> {
/// Compile the given `Program` into a function with the given name.
/// Translate the given IR type into an ABI parameter type for cranelift, as
/// best as possible.
fn translate_type(&self, t: &Type) -> AbiParam {
let (value_type, extension) = match t {
Type::Function(_, _) => (
types::Type::triple_pointer_type(&self.platform),
ir::ArgumentExtension::None,
),
Type::Primitive(PrimitiveType::Void) => (types::I8, ir::ArgumentExtension::None), // FIXME?
Type::Primitive(PrimitiveType::I8) => (types::I8, ir::ArgumentExtension::Sext),
Type::Primitive(PrimitiveType::I16) => (types::I16, ir::ArgumentExtension::Sext),
Type::Primitive(PrimitiveType::I32) => (types::I32, ir::ArgumentExtension::Sext),
Type::Primitive(PrimitiveType::I64) => (types::I64, ir::ArgumentExtension::Sext),
Type::Primitive(PrimitiveType::U8) => (types::I8, ir::ArgumentExtension::Uext),
Type::Primitive(PrimitiveType::U16) => (types::I16, ir::ArgumentExtension::Uext),
Type::Primitive(PrimitiveType::U32) => (types::I32, ir::ArgumentExtension::Uext),
Type::Primitive(PrimitiveType::U64) => (types::I64, ir::ArgumentExtension::Uext),
};
AbiParam {
value_type,
purpose: ir::ArgumentPurpose::Normal,
extension,
}
}
/// Compile the given program.
///
/// At some point, the use of `Program` is going to change; however, for the
/// moment, we have no notion of a function in our language so the whole input
/// is converted into a single output function. The type of the generated
/// function is, essentially, `fn() -> ()`: it takes no arguments and returns
/// no value.
///
/// The function provided can then be either written to a file (if using a
/// static Cranelift backend) or executed directly (if using the Cranelift JIT).
/// The returned value is a `FuncId` that represents a function that runs all the statements
/// found in the program, which will be compiled using the given function name. (If there
/// are no such statements, the function will do nothing.)
pub fn compile_program(
&mut self,
function_name: &str,
program: Program<Type>,
) -> Result<FuncId, BackendError> {
let mut generated_body = vec![];
for item in program.items {
match item {
TopLevel::Function(name, args, rettype, body) => {
self.compile_function(name.as_str(), &args, rettype, body);
}
TopLevel::Statement(stmt) => {
generated_body.push(stmt);
}
}
}
let void = Type::Primitive(PrimitiveType::Void);
self.compile_function(
function_name,
&[],
void.clone(),
Expression::Block(Location::manufactured(), void, generated_body),
)
}
/// Compile the given function.
pub fn compile_function(
&mut self,
function_name: &str,
mut program: Program,
arguments: &[(Variable, Type)],
return_type: Type,
body: Expression<Type>,
) -> Result<FuncId, BackendError> {
let basic_signature = Signature {
params: vec![],
returns: vec![],
params: arguments
.iter()
.map(|(_, t)| self.translate_type(t))
.collect(),
returns: if return_type == Type::Primitive(PrimitiveType::Void) {
vec![]
} else {
vec![self.translate_type(&return_type)]
},
call_conv: CallConv::triple_default(&self.platform),
};
@@ -63,13 +139,6 @@ impl<M: Module> Backend<M> {
let user_func_name = UserFuncName::user(0, func_id.as_u32());
ctx.func = Function::with_name_signature(user_func_name, basic_signature);
// We generate a table of every string that we use in the program, here.
// Cranelift is going to require us to have this in a particular structure
// (`GlobalValue`) so that we can reference them later, and it's going to
// be tricky to generate those on the fly. So we just generate the set we
// need here, and then have ir around in the table for later.
let string_table = self.build_string_table(&mut ctx.func, &program)?;
// In the future, we might want to see what runtime functions the function
// we were given uses, and then only include those functions that we care
// about. Presumably, we'd use some sort of lookup table like we do for
@@ -82,25 +151,32 @@ impl<M: Module> Backend<M> {
&mut ctx.func,
)?;
// In the case of the JIT, there may be symbols we've already defined outside
// the context of this particular `Progam`, which we might want to reference.
// Just like with strings, generating the `GlobalValue`s we need can potentially
// be a little tricky to do on the fly, so we generate the complete list right
// here and then use it later.
let pre_defined_symbols: HashMap<String, (GlobalValue, ConstantType)> = self
.defined_symbols
.iter()
.map(|(k, (v, t))| {
let local_data = self.module.declare_data_in_func(*v, &mut ctx.func);
(k.clone(), (local_data, *t))
})
.collect();
// Let's start creating the variable table we'll use when we're dereferencing
// them later. This table is a little interesting because instead of pointing
// from data to data, we're going to point from data (the variable) to an
// action to take if we encounter that variable at some later point. This
// makes it nice and easy to have many different ways to access data, such
// as globals, function arguments, etc.
let mut variables: ScopedMap<ArcIntern<String>, ReferenceBuilder> = ScopedMap::new();
// The last table we're going to need is our local variable table, to store
// variables used in this `Program` but not used outside of it. For whatever
// reason, Cranelift requires us to generate unique indexes for each of our
// variables; we just use a simple incrementing counter for that.
let mut variable_table = HashMap::new();
// At the outer-most scope of things, we'll put global variables we've defined
// elsewhere in the program.
for (name, (data_id, ty)) in self.defined_symbols.iter() {
let local_data = self.module.declare_data_in_func(*data_id, &mut ctx.func);
let cranelift_type = ir::Type::from(*ty);
variables.insert(
name.clone(),
ReferenceBuilder { cranelift_type, local_data, ir_type: *ty },
);
}
// Once we have these, we're going to actually push a level of scope and
// add our arguments. We push scope because if there happen to be any with
// the same name (their shouldn't be, but just in case), we want the arguments
// to win.
variables.new_scope();
// FIXME: Add arguments
let mut next_var_num = 1;
// Finally (!), we generate the function builder that we're going to use to
@@ -114,98 +190,13 @@ impl<M: Module> Backend<M> {
let main_block = builder.create_block();
builder.switch_to_block(main_block);
// Compiling a function is just compiling each of the statements in order.
// At the moment, we do the pattern match for statements here, and then
// directly compile the statements. If/when we add more statement forms,
// this is likely to become more cumbersome, and we'll want to separate
// these off. But for now, given the amount of tables we keep around to track
// state, it's easier to just include them.
for item in program.items.drain(..) {
match item {
TopLevel::Function(_, _, _, _) => unimplemented!(),
// Print statements are fairly easy to compile: we just lookup the
// output buffer, the address of the string to print, and the value
// of whatever variable we're printing. Then we just call print.
TopLevel::Statement(Statement::Print(ann, t, var)) => {
// Get the output buffer (or null) from our general compilation context.
let buffer_ptr = self.output_buffer_ptr();
let buffer_ptr = builder.ins().iconst(types::I64, buffer_ptr as i64);
// Get a reference to the string we want to print.
let local_name_ref = string_table.get(&var).unwrap();
let name_ptr = builder.ins().symbol_value(types::I64, *local_name_ref);
// Look up the value for the variable. Because this might be a
// global variable (and that requires special logic), we just turn
// this into an `Expression` and re-use the logic in that implementation.
let (val, vtype) = ValueOrRef::Ref(ann, t, var).into_crane(
&mut builder,
&variable_table,
&pre_defined_symbols,
)?;
let vtype_repr = builder.ins().iconst(types::I64, vtype as i64);
let casted_val = match vtype {
ConstantType::U64 | ConstantType::I64 => val,
ConstantType::I8 | ConstantType::I16 | ConstantType::I32 => {
builder.ins().sextend(types::I64, val)
}
ConstantType::U8 | ConstantType::U16 | ConstantType::U32 => {
builder.ins().uextend(types::I64, val)
}
};
// Finally, we can generate the call to print.
builder.ins().call(
print_func_ref,
&[buffer_ptr, name_ptr, vtype_repr, casted_val],
);
}
// Variable binding is a little more con
TopLevel::Statement(Statement::Binding(_, var_name, _, value)) => {
// Kick off to the `Expression` implementation to see what value we're going
// to bind to this variable.
let (val, etype) =
value.into_crane(&mut builder, &variable_table, &pre_defined_symbols)?;
// Now the question is: is this a local variable, or a global one?
if let Some((global_id, ctype)) = pre_defined_symbols.get(var_name.as_str()) {
// It's a global variable! In this case, we assume that someone has already
// dedicated some space in memory to store this value. We look this location
// up, and then tell Cranelift to store the value there.
assert_eq!(etype, *ctype);
let val_ptr = builder
.ins()
.symbol_value(ir::Type::from(*ctype), *global_id);
builder.ins().store(MemFlags::new(), val, val_ptr, 0);
} else {
// It's a local variable! In this case, we need to allocate a new Cranelift
// `Variable` for this variable, which we do using our `next_var_num` counter.
// (While we're doing this, we also increment `next_var_num`, so that we get
// a fresh `Variable` next time. This is one of those very narrow cases in which
// I wish Rust had an increment expression.)
let var = Variable::new(next_var_num);
next_var_num += 1;
// We can add the variable directly to our local variable map; it's `Copy`.
variable_table.insert(var_name, (var, etype));
// Now we tell Cranelift about our new variable!
builder.declare_var(var, ir::Type::from(etype));
builder.def_var(var, val);
}
}
}
}
let (value, _) = self.compile_expression(body, &mut variables, &mut builder)?;
// Now that we're done, inject a return function (one with no actual value; basically
// the equivalent of Rust's `return;`). We then seal the block (which lets Cranelift
// know that the block is done), and then finalize the function (which lets Cranelift
// know we're done with the function).
builder.ins().return_(&[]);
builder.ins().return_(&[value]);
builder.seal_block(main_block);
builder.finalize();
@@ -219,45 +210,18 @@ impl<M: Module> Backend<M> {
Ok(func_id)
}
// Build the string table for use in referencing strings later.
//
// This function is slightly smart, in that it only puts strings in the table that
// are used by the `Program`. (Thanks to `Progam::strings()`!) If the strings have
// been declared globally, via `Backend::define_string()`, we will re-use that data.
// Otherwise, this will define the string for you.
fn build_string_table(
/// Compile an expression, returning the Cranelift Value for the expression and
/// its type.
fn compile_expression(
&mut self,
func: &mut Function,
program: &Program,
) -> Result<StringTable, BackendError> {
let mut string_table = HashMap::new();
for interned_value in program.strings().drain() {
let global_id = match self.defined_strings.get(interned_value.as_str()) {
Some(x) => *x,
None => self.define_string(interned_value.as_str())?,
};
let local_data = self.module.declare_data_in_func(global_id, func);
string_table.insert(interned_value, local_data);
}
Ok(string_table)
}
}
impl Expression {
fn into_crane(
self,
expr: Expression<Type>,
variables: &mut ScopedMap<Variable, ReferenceBuilder>,
builder: &mut FunctionBuilder,
local_variables: &HashMap<ArcIntern<String>, (Variable, ConstantType)>,
global_variables: &HashMap<String, (GlobalValue, ConstantType)>,
) -> Result<(entities::Value, ConstantType), BackendError> {
match self {
Expression::Atomic(x) => x.into_crane(builder, local_variables, global_variables),
Expression::Cast(_, target_type, expr) => {
let (val, val_type) =
expr.into_crane(builder, local_variables, global_variables)?;
match expr {
Expression::Atomic(x) => self.compile_value_or_ref(x, variables, builder),
Expression::Cast(_, target_type, valref) => {
let (val, val_type) = self.compile_value_or_ref(valref, variables, builder)?;
match (val_type, &target_type) {
(ConstantType::I8, Type::Primitive(PrimitiveType::I8)) => Ok((val, val_type)),
@@ -325,7 +289,7 @@ impl Expression {
for val in vals.drain(..) {
let (compiled, compiled_type) =
val.into_crane(builder, local_variables, global_variables)?;
self.compile_value_or_ref(val, variables, builder)?;
if let Some(leftmost_type) = first_type {
assert_eq!(leftmost_type, compiled_type);
@@ -355,22 +319,79 @@ impl Expression {
Primitive::Divide => Ok((builder.ins().udiv(values[0], values[1]), first_type)),
}
}
Expression::Block(_, _, mut exprs) => match exprs.pop() {
None => Ok((builder.ins().iconst(types::I8, 0), ConstantType::I8)),
Some(last) => {
for inner in exprs {
// we can ignore all of these return values and such, because we
// don't actually use them anywhere
self.compile_expression(inner, variables, builder);
}
// instead, we just return the last one
self.compile_expression(last, variables, builder)
}
},
Expression::Print(ann, var) => {
// Get the output buffer (or null) from our general compilation context.
let buffer_ptr = self.output_buffer_ptr();
let buffer_ptr = builder.ins().iconst(types::I64, buffer_ptr as i64);
// Get a reference to the string we want to print.
let string_data_id = self
.defined_strings
.get(var.as_ref())
.ok_or_else(|| BackendError::UnknownString(var.clone()))?;
let local_name_ref = self
.module
.declare_data_in_func(*string_data_id, builder.func);
let name_ptr = builder.ins().symbol_value(types::I64, local_name_ref);
// Look up the value for the variable. Because this might be a
// global variable (and that requires special logic), we just turn
// this into an `Expression` and re-use the logic in that implementation.
let fake_ref = ValueOrRef::Ref(ann, Type::Primitive(PrimitiveType::U8), var);
let (val, vtype) = self.compile_value_or_ref(fake_ref, variables, builder)?;
let vtype_repr = builder.ins().iconst(types::I64, vtype as i64);
let casted_val = match vtype {
ConstantType::U64 | ConstantType::I64 => val,
ConstantType::I8 | ConstantType::I16 | ConstantType::I32 => {
builder.ins().sextend(types::I64, val)
}
ConstantType::U8 | ConstantType::U16 | ConstantType::U32 => {
builder.ins().uextend(types::I64, val)
}
};
// Finally, we can generate the call to print.
let print_func_ref = self.runtime_functions.include_runtime_function(
"print",
&mut self.module,
builder.func,
)?;
builder.ins().call(
print_func_ref,
&[buffer_ptr, name_ptr, vtype_repr, casted_val],
);
Ok((builder.ins().iconst(types::I8, 0), ConstantType::I8))
}
Expression::Bind(_, _, _, _) => unimplemented!(),
}
}
}
// Just to avoid duplication, this just leverages the `From<ValueOrRef>` trait implementation
// for `ValueOrRef` to compile this via the `Expression` logic, above.
impl ValueOrRef {
fn into_crane(
self,
/// Compile a value or reference into Cranelift, returning the Cranelift Value for
/// the expression and its type.
fn compile_value_or_ref(
&self,
valref: ValueOrRef<Type>,
variables: &ScopedMap<Variable, ReferenceBuilder>,
builder: &mut FunctionBuilder,
local_variables: &HashMap<ArcIntern<String>, (Variable, ConstantType)>,
global_variables: &HashMap<String, (GlobalValue, ConstantType)>,
) -> Result<(entities::Value, ConstantType), BackendError> {
match self {
// Values are pretty straightforward to compile, mostly because we only
// have one type of variable, and it's an integer type.
match valref {
ValueOrRef::Value(_, _, val) => match val {
Value::I8(_, v) => {
Ok((builder.ins().iconst(types::I8, v as i64), ConstantType::I8))
@@ -400,31 +421,217 @@ impl ValueOrRef {
ConstantType::U64,
)),
},
ValueOrRef::Ref(_, _, name) => {
// first we see if this is a local variable (which is nicer, from an
// optimization point of view.)
if let Some((local_var, etype)) = local_variables.get(&name) {
return Ok((builder.use_var(*local_var), *etype));
}
// then we check to see if this is a global reference, which requires us to
// first lookup where the value is stored, and then load it.
if let Some((global_var, etype)) = global_variables.get(name.as_ref()) {
let cranelift_type = ir::Type::from(*etype);
let val_ptr = builder.ins().symbol_value(cranelift_type, *global_var);
return Ok((
builder
.ins()
.load(cranelift_type, MemFlags::new(), val_ptr, 0),
*etype,
));
}
// this should never happen, because we should have made sure that there are
// no unbound variables a long time before this. but still ...
Err(BackendError::VariableLookupFailure(name))
}
ValueOrRef::Ref(_, _, name) => match variables.get(&name) {
None => Err(BackendError::VariableLookupFailure(name)),
Some(x) => Ok(x.refer_to(builder)),
},
}
}
// Compiling a function is just compiling each of the statements in order.
// At the moment, we do the pattern match for statements here, and then
// directly compile the statements. If/when we add more statement forms,
// this is likely to become more cumbersome, and we'll want to separate
// these off. But for now, given the amount of tables we keep around to track
// state, it's easier to just include them.
// for item in program.items.drain(..) {
// match item {
// TopLevel::Function(_, _, _) => unimplemented!(),
//
// // Print statements are fairly easy to compile: we just lookup the
// // output buffer, the address of the string to print, and the value
// // of whatever variable we're printing. Then we just call print.
// TopLevel::Statement(Statement::Print(ann, t, var)) => {
// // Get the output buffer (or null) from our general compilation context.
// let buffer_ptr = self.output_buffer_ptr();
// let buffer_ptr = builder.ins().iconst(types::I64, buffer_ptr as i64);
//
// // Get a reference to the string we want to print.
// let local_name_ref = string_table.get(&var).unwrap();
// let name_ptr = builder.ins().symbol_value(types::I64, *local_name_ref);
//
// // Look up the value for the variable. Because this might be a
// // global variable (and that requires special logic), we just turn
// // this into an `Expression` and re-use the logic in that implementation.
// let (val, vtype) = ValueOrRef::Ref(ann, t, var).into_crane(
// &mut builder,
// &variable_table,
// &pre_defined_symbols,
// )?;
//
// let vtype_repr = builder.ins().iconst(types::I64, vtype as i64);
//
// let casted_val = match vtype {
// ConstantType::U64 | ConstantType::I64 => val,
// ConstantType::I8 | ConstantType::I16 | ConstantType::I32 => {
// builder.ins().sextend(types::I64, val)
// }
// ConstantType::U8 | ConstantType::U16 | ConstantType::U32 => {
// builder.ins().uextend(types::I64, val)
// }
// };
//
// // Finally, we can generate the call to print.
// builder.ins().call(
// print_func_ref,
// &[buffer_ptr, name_ptr, vtype_repr, casted_val],
// );
// }
//
// // Variable binding is a little more con
// TopLevel::Statement(Statement::Binding(_, var_name, _, value)) => {
// // Kick off to the `Expression` implementation to see what value we're going
// // to bind to this variable.
// let (val, etype) =
// value.into_crane(&mut builder, &variable_table, &pre_defined_symbols)?;
//
// // Now the question is: is this a local variable, or a global one?
// if let Some((global_id, ctype)) = pre_defined_symbols.get(var_name.as_str()) {
// // It's a global variable! In this case, we assume that someone has already
// // dedicated some space in memory to store this value. We look this location
// // up, and then tell Cranelift to store the value there.
// assert_eq!(etype, *ctype);
// let val_ptr = builder
// .ins()
// .symbol_value(ir::Type::from(*ctype), *global_id);
// builder.ins().store(MemFlags::new(), val, val_ptr, 0);
// } else {
// // It's a local variable! In this case, we need to allocate a new Cranelift
// // `Variable` for this variable, which we do using our `next_var_num` counter.
// // (While we're doing this, we also increment `next_var_num`, so that we get
// // a fresh `Variable` next time. This is one of those very narrow cases in which
// // I wish Rust had an increment expression.)
// let var = Variable::new(next_var_num);
// next_var_num += 1;
//
// // We can add the variable directly to our local variable map; it's `Copy`.
// variable_table.insert(var_name, (var, etype));
//
// // Now we tell Cranelift about our new variable!
// builder.declare_var(var, ir::Type::from(etype));
// builder.def_var(var, val);
// }
// }
// }
// }
// Build the string table for use in referencing strings later.
//
// This function is slightly smart, in that it only puts strings in the table that
// are used by the `Program`. (Thanks to `Progam::strings()`!) If the strings have
// been declared globally, via `Backend::define_string()`, we will re-use that data.
// Otherwise, this will define the string for you.
// fn build_string_table(
// &mut self,
// func: &mut Function,
// program: &Expression<Type>,
// ) -> Result<StringTable, BackendError> {
// let mut string_table = HashMap::new();
//
// for interned_value in program.strings().drain() {
// let global_id = match self.defined_strings.get(interned_value.as_str()) {
// Some(x) => *x,
// None => self.define_string(interned_value.as_str())?,
// };
// let local_data = self.module.declare_data_in_func(global_id, func);
// string_table.insert(interned_value, local_data);
// }
//
// Ok(string_table)
// }
}
//impl Expression {
// fn into_crane(
// self,
// builder: &mut FunctionBuilder,
// local_variables: &HashMap<ArcIntern<String>, (Variable, ConstantType)>,
// global_variables: &HashMap<String, (GlobalValue, ConstantType)>,
// ) -> Result<(entities::Value, ConstantType), BackendError> {
// match self {
// Expression::Atomic(x) => x.into_crane(builder, local_variables, global_variables),
//
// Expression::Cast(_, target_type, expr) => {
// let (val, val_type) =
// expr.into_crane(builder, local_variables, global_variables)?;
//
// match (val_type, &target_type) {
// }
// }
//
// Expression::Primitive(_, _, prim, mut vals) => {
// }
// }
// }
//}
//
//// Just to avoid duplication, this just leverages the `From<ValueOrRef>` trait implementation
//// for `ValueOrRef` to compile this via the `Expression` logic, above.
//impl ValueOrRef {
// fn into_crane(
// self,
// builder: &mut FunctionBuilder,
// local_variables: &HashMap<ArcIntern<String>, (Variable, ConstantType)>,
// global_variables: &HashMap<String, (GlobalValue, ConstantType)>,
// ) -> Result<(entities::Value, ConstantType), BackendError> {
// match self {
// // Values are pretty straightforward to compile, mostly because we only
// // have one type of variable, and it's an integer type.
// ValueOrRef::Value(_, _, val) => match val {
// Value::I8(_, v) => {
// Ok((builder.ins().iconst(types::I8, v as i64), ConstantType::I8))
// }
// Value::I16(_, v) => Ok((
// builder.ins().iconst(types::I16, v as i64),
// ConstantType::I16,
// )),
// Value::I32(_, v) => Ok((
// builder.ins().iconst(types::I32, v as i64),
// ConstantType::I32,
// )),
// Value::I64(_, v) => Ok((builder.ins().iconst(types::I64, v), ConstantType::I64)),
// Value::U8(_, v) => {
// Ok((builder.ins().iconst(types::I8, v as i64), ConstantType::U8))
// }
// Value::U16(_, v) => Ok((
// builder.ins().iconst(types::I16, v as i64),
// ConstantType::U16,
// )),
// Value::U32(_, v) => Ok((
// builder.ins().iconst(types::I32, v as i64),
// ConstantType::U32,
// )),
// Value::U64(_, v) => Ok((
// builder.ins().iconst(types::I64, v as i64),
// ConstantType::U64,
// )),
// },
//
// ValueOrRef::Ref(_, _, name) => {
// // first we see if this is a local variable (which is nicer, from an
// // optimization point of view.)
// if let Some((local_var, etype)) = local_variables.get(&name) {
// return Ok((builder.use_var(*local_var), *etype));
// }
//
// // then we check to see if this is a global reference, which requires us to
// // first lookup where the value is stored, and then load it.
// if let Some((global_var, etype)) = global_variables.get(name.as_ref()) {
// let cranelift_type = ir::Type::from(*etype);
// let val_ptr = builder.ins().symbol_value(cranelift_type, *global_var);
// return Ok((
// builder
// .ins()
// .load(cranelift_type, MemFlags::new(), val_ptr, 0),
// *etype,
// ));
// }
//
// // this should never happen, because we should have made sure that there are
// // no unbound variables a long time before this. but still ...
// Err(BackendError::VariableLookupFailure(name))
// }
// }
// }
//}
//