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Infallible extractors, and some fixes to fallibility in return types (Option<T> vs T).

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This commit is contained in:
Chris Fallin
2021-09-09 15:33:15 -07:00
parent 6daa55af82
commit a412cce615
7 changed files with 156 additions and 29 deletions
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14
cranelift/isle/TODO
View File

@@ -1,8 +1,10 @@
- Optimizations
- Infallible patterns; optimize away control flow when possible.
- Don't do the closure-wrapping thing for expressions inside of patterns.
- Document the semantics of the DSL!
- Document semantics carefully, especially wrt extractors.
- Clean up and factor the codegen properly.
- Build out an initial set of bindings for Cranelift LowerCtx with extractors
for instruction info.
- Look into whether optimizations are possible:
- More in-depth fallibility analysis (avoid failure edges where possible)
- Slightly nicer human-readable generated code
- Include full rule body (S-expression) in comment, not just line number
- Inline some expressions (no more `let val23 = 1234; ... f(val23);`)

4
cranelift/isle/isle_examples/test3.isle
View File

@@ -10,10 +10,10 @@
(type u32 (primitive u32))
(decl Op (Opcode) Inst)
(extern extractor Op get_opcode)
(extern extractor infallible Op get_opcode)
(decl InstInput (InstInput u32) Inst)
(extern extractor InstInput get_inst_input (out in))
(extern extractor infallible InstInput get_inst_input (out in))
(decl Producer (Inst) InstInput)
(extern extractor Producer get_input_producer)

5
cranelift/isle/src/ast.rs
View File

@@ -171,6 +171,11 @@ pub enum Extern {
/// more precisely the term value that we are extracting, is
/// an "input").
arg_polarity: Option<Vec<ArgPolarity>>,
/// Infallibility: if an external extractor returns `(T1, T2,
/// ...)` rather than `Option<(T1, T2, ...)>`, and hence can
/// never fail, it is declared as such and allows for slightly
/// better code to be generated.
infallible: bool,
},
/// An external constructor: `(constructor Term rustfunc)` form.
Constructor {

59
cranelift/isle/src/codegen.rs
View File

@@ -567,7 +567,7 @@ impl<'a> Codegen<'a> {
) -> Result<(), Error> {
writeln!(
code,
"{}fn {}(&mut self, {}) -> Option<({},)>;",
"{}fn {}(&mut self, {}) -> {}({},){};",
indent,
sig.func_name,
sig.arg_tys
@@ -576,11 +576,13 @@ impl<'a> Codegen<'a> {
.map(|(i, &ty)| format!("arg{}: {}", i, self.type_name(ty, /* by_ref = */ true)))
.collect::<Vec<_>>()
.join(", "),
if sig.infallible { "" } else { "Option<" },
sig.ret_tys
.iter()
.map(|&ty| self.type_name(ty, /* by_ref = */ false))
.collect::<Vec<_>>()
.join(", ")
.join(", "),
if sig.infallible { "" } else { ">" },
)?;
Ok(())
}
@@ -822,7 +824,10 @@ impl<'a> Codegen<'a> {
self.define_val(&output, ctx, /* is_ref = */ false, ty);
}
&ExprInst::Construct {
ref inputs, term, ..
ref inputs,
term,
infallible,
..
} => {
let mut input_exprs = vec![];
for (input_value, _) in inputs {
@@ -838,13 +843,15 @@ impl<'a> Codegen<'a> {
let termdata = &self.termenv.terms[term.index()];
let sig = termdata.to_sig(self.typeenv).unwrap();
assert_eq!(input_exprs.len(), sig.arg_tys.len());
let fallible_try = if infallible { "" } else { "?" };
writeln!(
code,
"{}let {} = {}(ctx, {});",
"{}let {} = {}(ctx, {}){};",
indent,
outputname,
sig.full_name,
input_exprs.join(", "),
fallible_try,
)?;
self.define_val(&output, ctx, /* is_ref = */ false, termdata.ret_ty);
}
@@ -905,7 +912,6 @@ impl<'a> Codegen<'a> {
_ => true,
};
writeln!(code, "{}let {} = arg{};", indent, outputname, index)?;
writeln!(code, "{}{{", indent)?;
self.define_val(
&Value::Pattern {
inst: id,
@@ -961,6 +967,7 @@ impl<'a> Codegen<'a> {
ref inputs,
ref output_tys,
term,
infallible,
..
} => {
let termdata = &self.termenv.terms[term.index()];
@@ -983,6 +990,17 @@ impl<'a> Codegen<'a> {
})
.collect::<Vec<_>>();
if infallible {
writeln!(
code,
"{}let ({},) = {}(ctx, {});",
indent,
output_binders.join(", "),
sig.full_name,
input_values.join(", "),
)?;
Ok(true)
} else {
writeln!(
code,
"{}if let Some(({},)) = {}(ctx, {}) {{",
@@ -991,10 +1009,32 @@ impl<'a> Codegen<'a> {
sig.full_name,
input_values.join(", "),
)?;
Ok(false)
}
&PatternInst::Expr { ref seq, output_ty, .. } => {
}
&PatternInst::Expr {
ref seq, output_ty, ..
} if seq.is_const_int().is_some() => {
let (ty, val) = seq.is_const_int().unwrap();
assert_eq!(ty, output_ty);
let output = Value::Pattern {
inst: id,
output: 0,
};
writeln!(
code,
"{}let {} = {};",
indent,
self.value_name(&output),
val
)?;
self.define_val(&output, ctx, /* is_ref = */ false, ty);
Ok(true)
}
&PatternInst::Expr {
ref seq, output_ty, ..
} => {
let closure_name = format!("closure{}", id.index());
writeln!(code, "{}let {} = || {{", indent, closure_name)?;
let subindent = format!("{} ", indent);
@@ -1124,9 +1164,12 @@ impl<'a> Codegen<'a> {
let id = InstId(depth);
let infallible =
self.generate_pattern_inst(code, id, op, indent, ctx)?;
let i = if infallible { indent } else { &subindent[..] };
let sub_returned =
self.generate_body(code, depth + 1, node, &subindent, ctx)?;
self.generate_body(code, depth + 1, node, i, ctx)?;
if !infallible {
writeln!(code, "{}}}", indent)?;
}
if infallible && sub_returned {
returned = true;
break;

72
cranelift/isle/src/ir.rs
View File

@@ -50,6 +50,7 @@ pub enum PatternInst {
input_tys: Vec<TypeId>,
output_tys: Vec<TypeId>,
term: TermId,
infallible: bool,
},
/// Evaluate an expression and provide the given value as the
@@ -80,6 +81,7 @@ pub enum ExprInst {
inputs: Vec<(Value, TypeId)>,
ty: TypeId,
term: TermId,
infallible: bool,
},
/// Set the Nth return value. Produces no values.
@@ -130,6 +132,34 @@ pub struct ExprSequence {
pub pos: Pos,
}
impl ExprSequence {
pub fn is_const_int(&self) -> Option<(TypeId, i64)> {
if self.insts.len() == 2 && matches!(&self.insts[1], &ExprInst::Return { .. }) {
match &self.insts[0] {
&ExprInst::ConstInt { ty, val } => Some((ty, val)),
_ => None,
}
} else {
None
}
}
pub fn is_const_variant(&self) -> Option<(TypeId, VariantId)> {
if self.insts.len() == 2 && matches!(&self.insts[1], &ExprInst::Return { .. }) {
match &self.insts[0] {
&ExprInst::CreateVariant {
ref inputs,
ty,
variant,
} if inputs.len() == 0 => Some((ty, variant)),
_ => None,
}
} else {
None
}
}
}
#[derive(Clone, Copy, Debug)]
enum ValueOrArgs {
Value(Value),
@@ -195,6 +225,7 @@ impl PatternSequence {
input_tys: Vec<TypeId>,
output_tys: Vec<TypeId>,
term: TermId,
infallible: bool,
) -> Vec<Value> {
let inst = InstId(self.insts.len());
let mut outs = vec![];
@@ -208,6 +239,7 @@ impl PatternSequence {
input_tys,
output_tys,
term,
infallible,
});
outs
}
@@ -320,7 +352,9 @@ impl PatternSequence {
panic!("Should have been expanded away");
}
&TermKind::ExternalExtractor {
ref arg_polarity, ..
ref arg_polarity,
infallible,
..
} => {
// Evaluate all `input` args.
let mut inputs = vec![];
@@ -359,8 +393,8 @@ impl PatternSequence {
}
// Invoke the extractor.
let arg_values =
self.add_extract(inputs, input_tys, output_tys, term);
let arg_values = self
.add_extract(inputs, input_tys, output_tys, term, infallible);
for (pat, &val) in output_pats.iter().zip(arg_values.iter()) {
self.gen_pattern(
@@ -417,10 +451,21 @@ impl ExprSequence {
Value::Expr { inst, output: 0 }
}
fn add_construct(&mut self, inputs: &[(Value, TypeId)], ty: TypeId, term: TermId) -> Value {
fn add_construct(
&mut self,
inputs: &[(Value, TypeId)],
ty: TypeId,
term: TermId,
infallible: bool,
) -> Value {
let inst = InstId(self.insts.len());
let inputs = inputs.iter().cloned().collect();
self.add_inst(ExprInst::Construct { inputs, ty, term });
self.add_inst(ExprInst::Construct {
inputs,
ty,
term,
infallible,
});
Value::Expr { inst, output: 0 }
}
@@ -469,8 +514,21 @@ impl ExprSequence {
&TermKind::EnumVariant { variant } => {
self.add_create_variant(&arg_values_tys[..], ty, variant)
}
&TermKind::InternalConstructor | &TermKind::ExternalConstructor { .. } => {
self.add_construct(&arg_values_tys[..], ty, term)
&TermKind::InternalConstructor => {
self.add_construct(
&arg_values_tys[..],
ty,
term,
/* infallible = */ true,
)
}
&TermKind::ExternalConstructor { .. } => {
self.add_construct(
&arg_values_tys[..],
ty,
term,
/* infallible = */ false,
)
}
_ => panic!("Should have been caught by typechecking"),
}

10
cranelift/isle/src/parser.rs
View File

@@ -256,8 +256,17 @@ impl<'a> Parser<'a> {
})
} else if self.is_sym_str("extractor") {
self.symbol()?;
let infallible = if self.is_sym_str("infallible") {
self.symbol()?;
true
} else {
false
};
let term = self.parse_ident()?;
let func = self.parse_ident()?;
let arg_polarity = if self.is_lparen() {
let mut pol = vec![];
self.lparen()?;
@@ -284,6 +293,7 @@ impl<'a> Parser<'a> {
func,
pos: pos.unwrap(),
arg_polarity,
infallible,
})
} else {
Err(self.error(

9
cranelift/isle/src/sema.rs
View File

@@ -120,6 +120,8 @@ pub enum TermKind {
name: Sym,
/// Which arguments of the extractor are inputs and which are outputs?
arg_polarity: Vec<ArgPolarity>,
/// Is the external extractor infallible?
infallible: bool,
},
/// A term defined solely by an external constructor function.
ExternalConstructor {
@@ -138,6 +140,7 @@ pub struct ExternalSig {
pub full_name: String,
pub arg_tys: Vec<TypeId>,
pub ret_tys: Vec<TypeId>,
pub infallible: bool,
}
impl Term {
@@ -180,10 +183,12 @@ impl Term {
full_name: format!("C::{}", tyenv.syms[name.index()]),
arg_tys: self.arg_tys.clone(),
ret_tys: vec![self.ret_ty],
infallible: true,
}),
&TermKind::ExternalExtractor {
name,
ref arg_polarity,
infallible,
} => {
let mut arg_tys = vec![];
let mut ret_tys = vec![];
@@ -203,6 +208,7 @@ impl Term {
full_name: format!("C::{}", tyenv.syms[name.index()]),
arg_tys,
ret_tys,
infallible,
})
}
&TermKind::InternalConstructor { .. } => {
@@ -212,6 +218,7 @@ impl Term {
full_name: name,
arg_tys: self.arg_tys.clone(),
ret_tys: vec![self.ret_ty],
infallible: false,
})
}
_ => None,
@@ -688,6 +695,7 @@ impl TermEnv {
ref func,
pos,
ref arg_polarity,
infallible,
}) => {
let term_sym = tyenv.intern_mut(term);
let func_sym = tyenv.intern_mut(func);
@@ -717,6 +725,7 @@ impl TermEnv {
termdata.kind = TermKind::ExternalExtractor {
name: func_sym,
arg_polarity,
infallible,
};
}
_ => {