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Deduplicate literal -> constant lowering #56312

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Nov 29, 2018
Merged

Deduplicate literal -> constant lowering #56312

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40412dc
Deduplicate literal -> constant lowering
oli-obk Nov 28, 2018
afb8cba
Move hir::Lit -> ty::Const conversion into its own file
oli-obk Nov 28, 2018
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102 changes: 102 additions & 0 deletions src/librustc_mir/hair/constant.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,102 @@
use syntax::ast;
use rustc::ty::{self, Ty, TyCtxt, ParamEnv};
use syntax_pos::symbol::Symbol;
use rustc::mir::interpret::{ConstValue, Scalar};

#[derive(PartialEq)]
crate enum LitToConstError {
UnparseableFloat,
Reported,
}

crate fn lit_to_const<'a, 'gcx, 'tcx>(
lit: &'tcx ast::LitKind,
tcx: TyCtxt<'a, 'gcx, 'tcx>,
ty: Ty<'tcx>,
neg: bool,
) -> Result<&'tcx ty::Const<'tcx>, LitToConstError> {
use syntax::ast::*;

let trunc = |n| {
let param_ty = ParamEnv::reveal_all().and(tcx.lift_to_global(&ty).unwrap());
let width = tcx.layout_of(param_ty).map_err(|_| LitToConstError::Reported)?.size;
trace!("trunc {} with size {} and shift {}", n, width.bits(), 128 - width.bits());
let shift = 128 - width.bits();
let result = (n << shift) >> shift;
trace!("trunc result: {}", result);
Ok(ConstValue::Scalar(Scalar::Bits {
bits: result,
size: width.bytes() as u8,
}))
};

use rustc::mir::interpret::*;
let lit = match *lit {
LitKind::Str(ref s, _) => {
let s = s.as_str();
let id = tcx.allocate_bytes(s.as_bytes());
ConstValue::new_slice(Scalar::Ptr(id.into()), s.len() as u64, &tcx)
},
LitKind::ByteStr(ref data) => {
let id = tcx.allocate_bytes(data);
ConstValue::Scalar(Scalar::Ptr(id.into()))
},
LitKind::Byte(n) => ConstValue::Scalar(Scalar::Bits {
bits: n as u128,
size: 1,
}),
LitKind::Int(n, _) if neg => {
let n = n as i128;
let n = n.overflowing_neg().0;
trunc(n as u128)?
},
LitKind::Int(n, _) => trunc(n)?,
LitKind::Float(n, fty) => {
parse_float(n, fty, neg).map_err(|_| LitToConstError::UnparseableFloat)?
}
LitKind::FloatUnsuffixed(n) => {
let fty = match ty.sty {
ty::Float(fty) => fty,
_ => bug!()
};
parse_float(n, fty, neg).map_err(|_| LitToConstError::UnparseableFloat)?
}
LitKind::Bool(b) => ConstValue::Scalar(Scalar::from_bool(b)),
LitKind::Char(c) => ConstValue::Scalar(Scalar::from_char(c)),
};
Ok(ty::Const::from_const_value(tcx, lit, ty))
}

fn parse_float<'tcx>(
num: Symbol,
fty: ast::FloatTy,
neg: bool,
) -> Result<ConstValue<'tcx>, ()> {
let num = num.as_str();
use rustc_apfloat::ieee::{Single, Double};
use rustc_apfloat::Float;
let (bits, size) = match fty {
ast::FloatTy::F32 => {
num.parse::<f32>().map_err(|_| ())?;
let mut f = num.parse::<Single>().unwrap_or_else(|e| {
panic!("apfloat::ieee::Single failed to parse `{}`: {:?}", num, e)
});
if neg {
f = -f;
}
(f.to_bits(), 4)
}
ast::FloatTy::F64 => {
num.parse::<f64>().map_err(|_| ())?;
let mut f = num.parse::<Double>().unwrap_or_else(|e| {
panic!("apfloat::ieee::Single failed to parse `{}`: {:?}", num, e)
});
if neg {
f = -f;
}
(f.to_bits(), 8)
}
};

Ok(ConstValue::Scalar(Scalar::Bits { bits, size }))
}
67 changes: 12 additions & 55 deletions src/librustc_mir/hair/cx/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,12 +26,12 @@ use rustc::ty::subst::Subst;
use rustc::ty::{self, Ty, TyCtxt};
use rustc::ty::subst::{Kind, Substs};
use rustc::ty::layout::VariantIdx;
use syntax::ast::{self, LitKind};
use syntax::ast;
use syntax::attr;
use syntax::symbol::Symbol;
use rustc::hir;
use rustc_data_structures::sync::Lrc;
use hair::pattern::parse_float;
use hair::constant::{lit_to_const, LitToConstError};

#[derive(Clone)]
pub struct Cx<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
Expand Down Expand Up @@ -131,7 +131,6 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
ty::Const::from_bool(self.tcx, false)
}

// FIXME: Combine with rustc_mir::hair::pattern::lit_to_const
pub fn const_eval_literal(
&mut self,
lit: &'tcx ast::LitKind,
Expand All @@ -141,61 +140,19 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
) -> &'tcx ty::Const<'tcx> {
trace!("const_eval_literal: {:#?}, {:?}, {:?}, {:?}", lit, ty, sp, neg);

let parse_float = |num, fty| -> ConstValue<'tcx> {
parse_float(num, fty, neg).unwrap_or_else(|_| {
match lit_to_const(lit, self.tcx, ty, neg) {
Ok(c) => c,
Err(LitToConstError::UnparseableFloat) => {
// FIXME(#31407) this is only necessary because float parsing is buggy
self.tcx.sess.span_fatal(sp, "could not evaluate float literal (see issue #31407)");
})
};

let trunc = |n| {
let param_ty = self.param_env.and(self.tcx.lift_to_global(&ty).unwrap());
let width = self.tcx.layout_of(param_ty).unwrap().size;
trace!("trunc {} with size {} and shift {}", n, width.bits(), 128 - width.bits());
let shift = 128 - width.bits();
let result = (n << shift) >> shift;
trace!("trunc result: {}", result);
ConstValue::Scalar(Scalar::Bits {
bits: result,
size: width.bytes() as u8,
})
};

use rustc::mir::interpret::*;
let lit = match *lit {
LitKind::Str(ref s, _) => {
let s = s.as_str();
let id = self.tcx.allocate_bytes(s.as_bytes());
ConstValue::new_slice(Scalar::Ptr(id.into()), s.len() as u64, &self.tcx)
},
LitKind::ByteStr(ref data) => {
let id = self.tcx.allocate_bytes(data);
ConstValue::Scalar(Scalar::Ptr(id.into()))
self.tcx.sess.span_err(sp, "could not evaluate float literal (see issue #31407)");
// create a dummy value and continue compiling
Const::from_bits(self.tcx, 0, self.param_env.and(ty))
},
LitKind::Byte(n) => ConstValue::Scalar(Scalar::Bits {
bits: n as u128,
size: 1,
}),
LitKind::Int(n, _) if neg => {
let n = n as i128;
let n = n.overflowing_neg().0;
trunc(n as u128)
},
LitKind::Int(n, _) => trunc(n),
LitKind::Float(n, fty) => {
parse_float(n, fty)
}
LitKind::FloatUnsuffixed(n) => {
let fty = match ty.sty {
ty::Float(fty) => fty,
_ => bug!()
};
parse_float(n, fty)
Err(LitToConstError::Reported) => {
// create a dummy value and continue compiling
Const::from_bits(self.tcx, 0, self.param_env.and(ty))
}
LitKind::Bool(b) => ConstValue::Scalar(Scalar::from_bool(b)),
LitKind::Char(c) => ConstValue::Scalar(Scalar::from_char(c)),
};
ty::Const::from_const_value(self.tcx, lit, ty)
}
}

pub fn pattern_from_hir(&mut self, p: &hir::Pat) -> Pattern<'tcx> {
Expand Down
1 change: 1 addition & 0 deletions src/librustc_mir/hair/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ use syntax_pos::Span;
use self::cx::Cx;

pub mod cx;
mod constant;

pub mod pattern;
pub use self::pattern::{BindingMode, Pattern, PatternKind, FieldPattern};
Expand Down
137 changes: 7 additions & 130 deletions src/librustc_mir/hair/pattern/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ pub(crate) use self::check_match::check_match;
use const_eval::{const_field, const_variant_index};

use hair::util::UserAnnotatedTyHelpers;
use hair::constant::*;

use rustc::mir::{fmt_const_val, Field, BorrowKind, Mutability};
use rustc::mir::{ProjectionElem, UserTypeAnnotation, UserTypeProjection, UserTypeProjections};
Expand All @@ -37,7 +38,6 @@ use std::fmt;
use syntax::ast;
use syntax::ptr::P;
use syntax_pos::Span;
use syntax_pos::symbol::Symbol;

#[derive(Clone, Debug)]
pub enum PatternError {
Expand Down Expand Up @@ -891,12 +891,11 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
);
*self.const_to_pat(instance, val, expr.hir_id, lit.span).kind
},
Err(e) => {
if e == LitToConstError::UnparseableFloat {
self.errors.push(PatternError::FloatBug);
}
Err(LitToConstError::UnparseableFloat) => {
self.errors.push(PatternError::FloatBug);
PatternKind::Wild
},
Err(LitToConstError::Reported) => PatternKind::Wild,
}
},
hir::ExprKind::Path(ref qpath) => *self.lower_path(qpath, expr.hir_id, expr.span).kind,
Expand All @@ -914,12 +913,11 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
);
*self.const_to_pat(instance, val, expr.hir_id, lit.span).kind
},
Err(e) => {
if e == LitToConstError::UnparseableFloat {
self.errors.push(PatternError::FloatBug);
}
Err(LitToConstError::UnparseableFloat) => {
self.errors.push(PatternError::FloatBug);
PatternKind::Wild
},
Err(LitToConstError::Reported) => PatternKind::Wild,
}
}
_ => span_bug!(expr.span, "not a literal: {:?}", expr),
Expand Down Expand Up @@ -1294,124 +1292,3 @@ pub fn compare_const_vals<'a, 'tcx>(

fallback()
}

#[derive(PartialEq)]
enum LitToConstError {
UnparseableFloat,
Propagated,
}

// FIXME: Combine with rustc_mir::hair::cx::const_eval_literal
fn lit_to_const<'a, 'tcx>(lit: &'tcx ast::LitKind,
tcx: TyCtxt<'a, 'tcx, 'tcx>,
ty: Ty<'tcx>,
neg: bool)
-> Result<&'tcx ty::Const<'tcx>, LitToConstError> {
use syntax::ast::*;

use rustc::mir::interpret::*;
let lit = match *lit {
LitKind::Str(ref s, _) => {
let s = s.as_str();
let id = tcx.allocate_bytes(s.as_bytes());
ConstValue::new_slice(Scalar::Ptr(id.into()), s.len() as u64, &tcx)
},
LitKind::ByteStr(ref data) => {
let id = tcx.allocate_bytes(data);
ConstValue::Scalar(Scalar::Ptr(id.into()))
},
LitKind::Byte(n) => ConstValue::Scalar(Scalar::Bits {
bits: n as u128,
size: 1,
}),
LitKind::Int(n, _) => {
enum Int {
Signed(IntTy),
Unsigned(UintTy),
}
let ity = match ty.sty {
ty::Int(IntTy::Isize) => Int::Signed(tcx.sess.target.isize_ty),
ty::Int(other) => Int::Signed(other),
ty::Uint(UintTy::Usize) => Int::Unsigned(tcx.sess.target.usize_ty),
ty::Uint(other) => Int::Unsigned(other),
ty::Error => { // Avoid ICE (#51963)
return Err(LitToConstError::Propagated);
}
_ => bug!("literal integer type with bad type ({:?})", ty.sty),
};
// This converts from LitKind::Int (which is sign extended) to
// Scalar::Bytes (which is zero extended)
let n = match ity {
// FIXME(oli-obk): are these casts correct?
Int::Signed(IntTy::I8) if neg =>
(n as i8).overflowing_neg().0 as u8 as u128,
Int::Signed(IntTy::I16) if neg =>
(n as i16).overflowing_neg().0 as u16 as u128,
Int::Signed(IntTy::I32) if neg =>
(n as i32).overflowing_neg().0 as u32 as u128,
Int::Signed(IntTy::I64) if neg =>
(n as i64).overflowing_neg().0 as u64 as u128,
Int::Signed(IntTy::I128) if neg =>
(n as i128).overflowing_neg().0 as u128,
Int::Signed(IntTy::I8) | Int::Unsigned(UintTy::U8) => n as u8 as u128,
Int::Signed(IntTy::I16) | Int::Unsigned(UintTy::U16) => n as u16 as u128,
Int::Signed(IntTy::I32) | Int::Unsigned(UintTy::U32) => n as u32 as u128,
Int::Signed(IntTy::I64) | Int::Unsigned(UintTy::U64) => n as u64 as u128,
Int::Signed(IntTy::I128)| Int::Unsigned(UintTy::U128) => n,
_ => bug!(),
};
let size = tcx.layout_of(ty::ParamEnv::empty().and(ty)).unwrap().size.bytes() as u8;
ConstValue::Scalar(Scalar::Bits {
bits: n,
size,
})
},
LitKind::Float(n, fty) => {
parse_float(n, fty, neg).map_err(|_| LitToConstError::UnparseableFloat)?
}
LitKind::FloatUnsuffixed(n) => {
let fty = match ty.sty {
ty::Float(fty) => fty,
_ => bug!()
};
parse_float(n, fty, neg).map_err(|_| LitToConstError::UnparseableFloat)?
}
LitKind::Bool(b) => ConstValue::Scalar(Scalar::from_bool(b)),
LitKind::Char(c) => ConstValue::Scalar(Scalar::from_char(c)),
};
Ok(ty::Const::from_const_value(tcx, lit, ty))
}

pub fn parse_float<'tcx>(
num: Symbol,
fty: ast::FloatTy,
neg: bool,
) -> Result<ConstValue<'tcx>, ()> {
let num = num.as_str();
use rustc_apfloat::ieee::{Single, Double};
use rustc_apfloat::Float;
let (bits, size) = match fty {
ast::FloatTy::F32 => {
num.parse::<f32>().map_err(|_| ())?;
let mut f = num.parse::<Single>().unwrap_or_else(|e| {
panic!("apfloat::ieee::Single failed to parse `{}`: {:?}", num, e)
});
if neg {
f = -f;
}
(f.to_bits(), 4)
}
ast::FloatTy::F64 => {
num.parse::<f64>().map_err(|_| ())?;
let mut f = num.parse::<Double>().unwrap_or_else(|e| {
panic!("apfloat::ieee::Single failed to parse `{}`: {:?}", num, e)
});
if neg {
f = -f;
}
(f.to_bits(), 8)
}
};

Ok(ConstValue::Scalar(Scalar::Bits { bits, size }))
}