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changed Constant to a struct with 'needed_resolution' bool

This commit is contained in:
llogiq 2015-08-13 10:45:30 +02:00
parent a2f19f2a38
commit 1a19d5ef65
1 changed files with 138 additions and 64 deletions
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202
src/const.rs
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@ -18,9 +18,25 @@ impl From<FloatTy> for FloatWidth {
}
}
#[derive(PartialEq, Eq, Debug, Clone)]
pub struct Constant {
constant: ConstantVariant,
needed_resolution: bool
}
impl Constant {
fn new(variant: ConstantVariant) -> Constant {
Constant { constant: variant, needed_resolution: false }
}
fn new_resolved(variant: ConstantVariant) -> Constant {
Constant { constant: variant, needed_resolution: true }
}
}
/// a Lit_-like enum to fold constant `Expr`s into
#[derive(PartialEq, Eq, Debug, Clone)]
pub enum Constant {
pub enum ConstantVariant {
/// a String "abc"
ConstantStr(&'static str, StrStyle),
/// a Binary String b"abc"
@ -43,34 +59,51 @@ pub enum Constant {
ConstantTuple(Vec<Constant>),
}
/// simple constant folding
pub fn constant(cx: &Context, e: &Expr, follow: bool) -> Option<Constant> {
impl ConstantVariant {
/// convert to u64 if possible
///
/// # panics
///
/// if the constant could not be converted to u64 losslessly
fn as_u64(&self) -> u64 {
if let &ConstantInt(val, _) = self {
val // TODO we may want to check the sign if any
} else {
panic!("Could not convert a {:?} to u64");
}
}
}
/// simple constant folding: Insert an expression, get a constant or none.
pub fn constant(cx: &Context, e: &Expr) -> Option<Constant> {
match e {
&ExprParen(ref inner) => constant(cx, inner, follow),
&ExprPath(_, _) => if follow { fetch_path(cx, e) } else { None },
&ExprBlock(ref block) => constant_block(cx, inner, follow),
&ExprParen(ref inner) => constant(cx, inner),
&ExprPath(_, _) => fetch_path(cx, e),
&ExprBlock(ref block) => constant_block(cx, inner),
&ExprIf(ref cond, ref then, ref otherwise) =>
match constant(cx, cond) {
Some(ConstantBool(true)) => constant(cx, then, follow),
Some(ConstantBool(false)) => constant(cx, otherwise, follow),
_ => None,
},
constant_if(cx, cond, then, otherwise),
&ExprLit(ref lit) => Some(lit_to_constant(lit)),
&ExprVec(ref vec) => constant_vec(cx, vec, follow),
&ExprTup(ref tup) => constant_tup(cx, tup, follow),
&ExprVec(ref vec) => constant_vec(cx, vec),
&ExprTup(ref tup) => constant_tup(cx, tup),
&ExprRepeat(ref value, ref number) =>
constant_binop_apply(cx, value, number,|v, n| ConstantRepeat(v, n)),
&ExprUnary(op, ref operand) => constant(cx, operand, follow).and_then(
constant_binop_apply(cx, value, number,|v, n| Constant {
constant: ConstantRepeat(v, n.constant.as_u64()),
needed_resolution: v.needed_resolution || n.needed_resolution
}),
&ExprUnary(op, ref operand) => constant(cx, operand).and_then(
|o| match op {
UnNot =>
if let ConstantBool(b) = o {
Some(ConstantBool(!b))
if let ConstantBool(b) = o.variant {
Some(Constant{
needed_resolution: o.needed_resolution,
constant: ConstantBool(!b),
})
} else { None },
UnNeg => constant_negate(o),
UnUniq | UnDeref => o,
}),
&ExprBinary(op, ref left, ref right) =>
constant_binop(cx, op, left, right, follow),
constant_binop(op, left, right),
//TODO: add other expressions
_ => None,
}
@ -78,68 +111,100 @@ pub fn constant(cx: &Context, e: &Expr, follow: bool) -> Option<Constant> {
fn lit_to_constant(lit: &Lit_) -> Constant {
match lit {
&LitStr(ref is, style) => ConstantStr(&*is, style),
&LitBinary(ref blob) => ConstantBinary(blob.clone()),
&LitByte(b) => ConstantByte(b),
&LitChar(c) => ConstantChar(c),
&LitInt(value, ty) => ConstantInt(value, ty),
&LitFloat(ref is, ty) => ConstantFloat(Cow::Borrowed(&*is), ty.into()),
&LitStr(ref is, style) => Constant::new(ConstantStr(&*is, style)),
&LitBinary(ref blob) => Constant::new(ConstantBinary(blob.clone())),
&LitByte(b) => Constant::new(ConstantByte(b)),
&LitChar(c) => Constant::new(ConstantChar(c)),
&LitInt(value, ty) => Constant::new(ConstantInt(value, ty)),
&LitFloat(ref is, ty) =>
Constant::new(ConstantFloat(Cow::Borrowed(&*is), ty.into())),
&LitFloatUnsuffixed(InternedString) =>
ConstantFloat(Cow::Borrowed(&*is), FwAny),
&LitBool(b) => ConstantBool(b),
Constant::new(ConstantFloat(Cow::Borrowed(&*is), FwAny)),
&LitBool(b) => Constant::new(ConstantBool(b)),
}
}
/// create `Some(ConstantVec(..))` of all constants, unless there is any
/// non-constant part
fn constant_vec(cx: &Context, vec: &[&Expr], follow: bool) -> Option<Constant> {
parts = Vec::new();
fn constant_vec(cx: &Context, vec: &[&Expr]) -> Option<Constant> {
let mut parts = Vec::new();
let mut resolved = false;
for opt_part in vec {
match constant(cx, opt_part, follow) {
Some(ref p) => parts.push(p),
match constant(cx, opt_part) {
Some(ref p) => {
resolved |= p.needed_resolution;
parts.push(p)
},
None => { return None; },
}
}
Some(ConstantVec(parts))
Some(Constant {
constant: ConstantVec(parts),
needed_resolution: resolved
})
}
fn constant_tup(cx: &Context, tup: &[&Expr], follow: bool) -> Option<Constant> {
parts = Vec::new();
fn constant_tup(cx: &Context, tup: &[&Expr]) -> Option<Constant> {
let mut parts = Vec::new();
let mut resolved = false;
for opt_part in vec {
match constant(cx, opt_part, follow) {
Some(ref p) => parts.push(p),
match constant(cx, opt_part) {
Some(ref p) => {
resolved |= p.needed_resolution;
parts.push(p)
},
None => { return None; },
}
}
Some(ConstantTuple(parts))
Some(Constant {
constant: ConstantTuple(parts),
needed_resolution: resolved
})
}
/// lookup a possibly constant expression from a ExprPath
fn fetch_path(cx: &Context, e: &Expr) -> Option<Constant> {
if let Some(&PathResolution { base_def: DefConst(id), ..}) =
cx.tcx.def_map.borrow().get(&e.id) {
lookup_const_by_id(cx.tcx, id, None).map(|l| constant(cx, l))
lookup_const_by_id(cx.tcx, id, None).map(
|l| Constant::new_resolved(constant(cx, l).constant))
} else { None }
}
/// A block can only yield a constant if it only has one constant expression
fn constant_block(cx: &Context, block: &Block, follow: bool) -> Option<Constant> {
fn constant_block(cx: &Context, block: &Block) -> Option<Constant> {
if block.stmts.is_empty() {
block.expr.map(|b| constant(cx, b, follow))
block.expr.map(|b| constant(cx, b))
} else { None }
}
fn constant_if(cx: &Context, cond: &Expr, then: &Expr, otherwise: &Expr) ->
Option<Constant> {
if let Some(Constant{ constant: ConstantBool(b), needed_resolution: res }) =
constant(cx, cond) {
let part = constant(cx, if b { then } else { otherwise });
Some(Constant {
constant: part.constant,
needed_resolution: res || part.needed_resolution,
})
} else { None }
}
fn constant_negate(o: Constant) -> Option<Constant> {
match o {
&ConstantInt(value, ty) =>
Some(ConstantInt(value, match ty {
SignedIntLit(ity, sign) => SignedIntLit(ity, neg_sign(sign)),
UnsuffixedIntLit(sign) => UnsuffixedIntLit(neg_sign(sign)),
_ => { return None; },
})),
&LitFloat(ref is, ref ty) => Some(ConstantFloat(neg_float_str(is), ty)),
_ => None,
}
Some(Constant{
needed_resolution: o.needed_resolution,
constant: match o.constant {
&ConstantInt(value, ty) =>
ConstantInt(value, match ty {
SignedIntLit(ity, sign) =>
SignedIntLit(ity, neg_sign(sign)),
UnsuffixedIntLit(sign) => UnsuffixedIntLit(neg_sign(sign)),
_ => { return None; },
}),
&LitFloat(ref is, ref ty) => ConstantFloat(neg_float_str(is), ty),
_ => { return None; },
}
})
}
fn neg_sign(s: Sign) -> Sign {
@ -157,16 +222,16 @@ fn neg_float_str(s: &InternedString) -> Cow<'static, str> {
}
}
fn constant_binop(cx: &Context, op: BinOp, left: &Expr, right: &Expr,
follow: bool) -> Option<Constant> {
fn constant_binop(cx: &Context, op: BinOp, left: &Expr, right: &Expr)
-> Option<Constant> {
match op.node {
//BiAdd,
//BiSub,
//BiMul,
//BiDiv,
//BiRem,
BiAnd => constant_short_circuit(cx, left, right, false, follow),
BiOr => constant_short_circuit(cx, left, right, true, follow),
BiAnd => constant_short_circuit(cx, left, right, false),
BiOr => constant_short_circuit(cx, left, right, true),
//BiBitXor,
//BiBitAnd,
//BiBitOr,
@ -182,21 +247,30 @@ fn constant_binop(cx: &Context, op: BinOp, left: &Expr, right: &Expr,
}
}
fn constant_binop_apply<F>(cx: &Context, left: &Expr, right: &Expr, op: F,
follow: bool) -> Option<Constant>
where F: FnMut(Constant, Constant) -> Option<Constant> {
constant(cx, left, follow).and_then(|l| constant(cx, right, follow)
.and_then(|r| op(l, r)))
fn constant_binop_apply<F>(cx: &Context, left: &Expr, right: &Expr, op: F)
-> Option<Constant>
where F: FnMut(ConstantVariant, ConstantVariant) -> Option<ConstantVariant> {
constant(cx, left).and_then(|l| constant(cx, right).and_then(
|r| Constant {
needed_resolution: l.needed_resolution || r.needed_resolution,
constant: op(l.constant, r.constant)
}))
}
fn constant_short_circuit(cx: &Context, left: &Expr, right: &Expr, b: bool,
follow: bool) -> Option<Constant> {
if let ConstantBool(lbool) = constant(cx, left, follow) {
fn constant_short_circuit(cx: &Context, left: &Expr, right: &Expr, b: bool) ->
Option<Constant> {
let leftconst = constant(cx, left);
if let ConstantBool(lbool) = leftconst.constant {
if l == b {
Some(ConstantBool(b))
Some(leftconst)
} else {
if let ConstantBool(rbool) = constant(cx, right, follow) {
Some(ConstantBool(rbool))
let rightconst = constant(cx, right);
if let ConstantBool(rbool) = rightconst.constant {
Some(Constant {
constant: rightconst.constant,
needed_resolution: leftconst.needed_resolution ||
rightconst.needed_resolution,
})
} else { None }
}
} else { None }