implement floats by running the ops on the host architecture

src/interpreter/mod.rs

@@ -169,7 +169,7 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
     // TODO(solson): Try making const_to_primval instead.
     fn const_to_ptr(&mut self, const_val: &const_val::ConstVal) -> EvalResult<'tcx, Pointer> {
         use rustc::middle::const_val::ConstVal::*;
-        use rustc_const_math::{ConstInt, ConstIsize, ConstUsize};
+        use rustc_const_math::{ConstInt, ConstIsize, ConstUsize, ConstFloat};
         macro_rules! i2p {
             ($i:ident, $n:expr) => {{
                 let ptr = self.memory.allocate($n);
@@ -178,7 +178,17 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
             }}
         }
         match *const_val {
-            Float(_f) => unimplemented!(),
+            Float(ConstFloat::F32(f)) => {
+                let ptr = self.memory.allocate(4);
+                self.memory.write_f32(ptr, f)?;
+                Ok(ptr)
+            },
+            Float(ConstFloat::F64(f)) => {
+                let ptr = self.memory.allocate(8);
+                self.memory.write_f64(ptr, f)?;
+                Ok(ptr)
+            },
+            Float(ConstFloat::FInfer{..}) => unreachable!(),
             Integral(ConstInt::Infer(_)) => unreachable!(),
             Integral(ConstInt::InferSigned(_)) => unreachable!(),
             Integral(ConstInt::I8(i)) => i2p!(i, 1),
@@ -824,7 +834,7 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
     }
 
     pub fn read_primval(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<'tcx, PrimVal> {
-        use syntax::ast::{IntTy, UintTy};
+        use syntax::ast::{IntTy, UintTy, FloatTy};
         let val = match (self.memory.pointer_size(), &ty.sty) {
             (_, &ty::TyBool)              => PrimVal::Bool(self.memory.read_bool(ptr)?),
             (_, &ty::TyChar)              => {
@@ -849,6 +859,9 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
             (8, &ty::TyUint(UintTy::Us)) |
             (_, &ty::TyUint(UintTy::U64)) => PrimVal::U64(self.memory.read_uint(ptr, 8)? as u64),
 
+            (_, &ty::TyFloat(FloatTy::F32)) => PrimVal::F32(self.memory.read_f32(ptr)?),
+            (_, &ty::TyFloat(FloatTy::F64)) => PrimVal::F64(self.memory.read_f64(ptr)?),
+
             (_, &ty::TyFnDef(def_id, substs, fn_ty)) => {
                 PrimVal::FnPtr(self.memory.create_fn_ptr(def_id, substs, fn_ty))
             },

src/memory.rs

@@ -407,6 +407,8 @@ impl<'a, 'tcx> Memory<'a, 'tcx> {
             PrimVal::U64(n)  => self.write_uint(ptr, n as u64, 8),
             PrimVal::Char(c) => self.write_uint(ptr, c as u64, 4),
             PrimVal::IntegerPtr(n) => self.write_uint(ptr, n as u64, pointer_size),
+            PrimVal::F32(f) => self.write_f32(ptr, f),
+            PrimVal::F64(f) => self.write_f64(ptr, f),
             PrimVal::FnPtr(_p) |
             PrimVal::AbstractPtr(_p) => unimplemented!(),
         }
@@ -464,6 +466,28 @@ impl<'a, 'tcx> Memory<'a, 'tcx> {
         let size = self.pointer_size();
         self.write_uint(ptr, n, size)
     }
+
+    pub fn write_f32(&mut self, ptr: Pointer, f: f32) -> EvalResult<'tcx, ()> {
+        let endianess = self.endianess();
+        let b = self.get_bytes_mut(ptr, 4)?;
+        write_target_f32(endianess, b, f).unwrap();
+        Ok(())
+    }
+
+    pub fn write_f64(&mut self, ptr: Pointer, f: f64) -> EvalResult<'tcx, ()> {
+        let endianess = self.endianess();
+        let b = self.get_bytes_mut(ptr, 8)?;
+        write_target_f64(endianess, b, f).unwrap();
+        Ok(())
+    }
+
+    pub fn read_f32(&self, ptr: Pointer) -> EvalResult<'tcx, f32> {
+        self.get_bytes(ptr, 4).map(|b| read_target_f32(self.endianess(), b).unwrap())
+    }
+
+    pub fn read_f64(&self, ptr: Pointer) -> EvalResult<'tcx, f64> {
+        self.get_bytes(ptr, 8).map(|b| read_target_f64(self.endianess(), b).unwrap())
+    }
 }
 
 /// Relocations
@@ -586,6 +610,36 @@ fn read_target_int(endianess: layout::Endian, mut source: &[u8]) -> Result<i64,
     }
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// Methods to access floats in the target endianess
+////////////////////////////////////////////////////////////////////////////////
+
+fn write_target_f32(endianess: layout::Endian, mut target: &mut [u8], data: f32) -> Result<(), byteorder::Error> {
+    match endianess {
+        layout::Endian::Little => target.write_f32::<LittleEndian>(data),
+        layout::Endian::Big => target.write_f32::<BigEndian>(data),
+    }
+}
+fn write_target_f64(endianess: layout::Endian, mut target: &mut [u8], data: f64) -> Result<(), byteorder::Error> {
+    match endianess {
+        layout::Endian::Little => target.write_f64::<LittleEndian>(data),
+        layout::Endian::Big => target.write_f64::<BigEndian>(data),
+    }
+}
+
+fn read_target_f32(endianess: layout::Endian, mut source: &[u8]) -> Result<f32, byteorder::Error> {
+    match endianess {
+        layout::Endian::Little => source.read_f32::<LittleEndian>(),
+        layout::Endian::Big => source.read_f32::<BigEndian>(),
+    }
+}
+fn read_target_f64(endianess: layout::Endian, mut source: &[u8]) -> Result<f64, byteorder::Error> {
+    match endianess {
+        layout::Endian::Little => source.read_f64::<LittleEndian>(),
+        layout::Endian::Big => source.read_f64::<BigEndian>(),
+    }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Undefined byte tracking
 ////////////////////////////////////////////////////////////////////////////////

src/primval.rs

@@ -13,6 +13,8 @@ pub enum PrimVal {
     FnPtr(Pointer),
     IntegerPtr(u64),
     Char(char),
+
+    F32(f32), F64(f64),
 }
 
 /// returns the result of the operation and whether the operation overflowed
@@ -57,6 +59,32 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
         })
     }
 
+    macro_rules! float_binops {
+        ($v:ident, $l:ident, $r:ident) => ({
+            match bin_op {
+                Add    => $v($l + $r),
+                Sub    => $v($l - $r),
+                Mul    => $v($l * $r),
+                Div    => $v($l / $r),
+                Rem    => $v($l % $r),
+
+                // invalid float ops
+                BitXor => unreachable!(),
+                BitAnd => unreachable!(),
+                BitOr  => unreachable!(),
+                Shl => unreachable!(),
+                Shr => unreachable!(),
+
+                Eq => Bool($l == $r),
+                Ne => Bool($l != $r),
+                Lt => Bool($l < $r),
+                Le => Bool($l <= $r),
+                Gt => Bool($l > $r),
+                Ge => Bool($l >= $r),
+            }
+        })
+    }
+
     fn unrelated_ptr_ops<'tcx>(bin_op: mir::BinOp) -> EvalResult<'tcx, PrimVal> {
         use rustc::mir::repr::BinOp::*;
         match bin_op {
@@ -128,6 +156,8 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
         (U16(l), U16(r)) => int_binops!(U16, l, r),
         (U32(l), U32(r)) => int_binops!(U32, l, r),
         (U64(l), U64(r)) => int_binops!(U64, l, r),
+        (F32(l), F32(r)) => float_binops!(F32, l, r),
+        (F64(l), F64(r)) => float_binops!(F64, l, r),
         (Char(l), Char(r)) => match bin_op {
             Eq => Bool(l == r),
             Ne => Bool(l != r),
@@ -211,6 +241,9 @@ pub fn unary_op<'tcx>(un_op: mir::UnOp, val: PrimVal) -> EvalResult<'tcx, PrimVa
         (Not, U16(n)) => Ok(U16(!n)),
         (Not, U32(n)) => Ok(U32(!n)),
         (Not, U64(n)) => Ok(U64(!n)),
+
+        (Neg, F64(n)) => Ok(F64(-n)),
+        (Neg, F32(n)) => Ok(F32(-n)),
         _ => Err(EvalError::Unimplemented(format!("unimplemented unary op: {:?}, {:?}", un_op, val))),
     }
 }

tests/run-pass/floats.rs

@@ -0,0 +1,11 @@
+
+fn main() {
+    assert_eq!(6.0_f32*6.0_f32, 36.0_f32);
+    assert_eq!(6.0_f64*6.0_f64, 36.0_f64);
+    assert_eq!(-{5.0_f32}, -5.0_f32);
+    assert!((5.0_f32/0.0).is_infinite());
+    assert!((-5.0_f32).sqrt().is_nan());
+    let x: u64 = unsafe { std::mem::transmute(42.0_f64) };
+    let y: f64 = unsafe { std::mem::transmute(x) };
+    assert_eq!(y, 42.0_f64);
+}