From 58b4fac1ceca3d75e59091b09e71a8914d6bd7e2 Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Fri, 17 Jun 2016 13:09:20 +0200
Subject: [PATCH 01/18] implement overflowing ops

---
 src/error.rs           | 21 ++++++++++++++
 src/interpreter/mod.rs | 47 ++++++++++++++++++++++--------
 src/lib.rs             |  1 +
 src/primval.rs         | 66 +++++++++++++++++++++++++++++++++++++-----
 tests/compiletest.rs   |  6 ++--
 5 files changed, 118 insertions(+), 23 deletions(-)

diff --git a/src/error.rs b/src/error.rs
index 35a978f2d2..885f5af632 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -3,6 +3,9 @@ use std::fmt;
 use rustc::mir::repr as mir;
 use rustc::ty::BareFnTy;
 use memory::Pointer;
+use rustc_const_math::ConstMathErr;
+use syntax::codemap::Span;
+use primval::PrimVal;
 
 #[derive(Clone, Debug)]
 pub enum EvalError<'tcx> {
@@ -24,6 +27,10 @@ pub enum EvalError<'tcx> {
     Unimplemented(String),
     DerefFunctionPointer,
     ExecuteMemory,
+    ArrayIndexOutOfBounds(Span, u64, u64),
+    Math(Span, ConstMathErr),
+    InvalidBitShiftRhs(PrimVal),
+    Overflow(PrimVal, PrimVal, mir::BinOp, PrimVal),
 }
 
 pub type EvalResult<'tcx, T> = Result<T, EvalError<'tcx>>;
@@ -58,6 +65,14 @@ impl<'tcx> Error for EvalError<'tcx> {
                 "tried to dereference a function pointer",
             EvalError::ExecuteMemory =>
                 "tried to treat a memory pointer as a function pointer",
+            EvalError::ArrayIndexOutOfBounds(..) =>
+                "array index out of bounds",
+            EvalError::Math(..) =>
+                "mathematical operation failed",
+            EvalError::InvalidBitShiftRhs(..) =>
+                "bit shift rhs negative or not an int",
+            EvalError::Overflow(..) =>
+                "mathematical operation overflowed",
         }
     }
 
@@ -73,6 +88,12 @@ impl<'tcx> fmt::Display for EvalError<'tcx> {
             },
             EvalError::FunctionPointerTyMismatch(expected, got) =>
                 write!(f, "tried to call a function of type {:?} through a function pointer of type {:?}", expected, got),
+            EvalError::ArrayIndexOutOfBounds(span, len, index) =>
+                write!(f, "array index {} out of bounds {} at {:?}", index, len, span),
+            EvalError::Math(span, ref err) =>
+                write!(f, "mathematical operation at {:?} failed with {:?}", span, err),
+            EvalError::Overflow(l, r, op, val) =>
+                write!(f, "mathematical operation overflowed: {:?} {} {:?} => {:?}", l, op.to_hir_binop().as_str(), r, val),
             _ => write!(f, "{}", self.description()),
         }
     }
diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index 213f813529..6d367a3be2 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -474,15 +474,23 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
                 self.frame_mut().block = target;
             }
 
-            Assert { ref cond, expected, ref msg, target, cleanup } => {
-                let actual_ptr = self.eval_operand(cond)?;
-                let actual = self.memory.read_bool(actual_ptr)?;
-                if actual == expected {
+            Assert { ref cond, expected, ref msg, target, .. } => {
+                let cond_ptr = self.eval_operand(cond)?;
+                if expected == self.memory.read_bool(cond_ptr)? {
                     self.frame_mut().block = target;
                 } else {
-                    panic!("unimplemented: jump to {:?} and print {:?}", cleanup, msg);
+                    return match *msg {
+                        mir::AssertMessage::BoundsCheck { ref len, ref index } => {
+                            let len = self.eval_operand(len).expect("can't eval len");
+                            let len = self.memory.read_usize(len).expect("can't read len");
+                            let index = self.eval_operand(index).expect("can't eval index");
+                            let index = self.memory.read_usize(index).expect("can't read index");
+                            Err(EvalError::ArrayIndexOutOfBounds(terminator.source_info.span, len, index))
+                        },
+                        mir::AssertMessage::Math(ref err) => Err(EvalError::Math(terminator.source_info.span, err.clone())),
+                    }
                 }
-            }
+            },
 
             DropAndReplace { .. } => unimplemented!(),
             Resume => unimplemented!(),
@@ -922,13 +930,28 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
                 let right_ty = self.operand_ty(right);
                 let right_val = self.read_primval(right_ptr, right_ty)?;
 
-                let val = primval::binary_op(bin_op, left_val, right_val)?;
-                self.memory.write_primval(dest, val)?;
+                use rustc::ty::layout::Layout::*;
+                let tup_layout = match *dest_layout {
+                    Univariant { ref variant, .. } => variant,
+                    _ => panic!("checked bin op returns something other than a tuple"),
+                };
 
-                // FIXME(solson): Find the result type size properly. Perhaps refactor out
-                // Projection calculations so we can do the equivalent of `dest.1` here.
-                let s = self.type_size(left_ty);
-                self.memory.write_bool(dest.offset(s as isize), false)?;
+                match primval::binary_op(bin_op, left_val, right_val) {
+                    Ok(val) => {
+                        let offset = tup_layout.field_offset(0).bytes() as isize;
+                        self.memory.write_primval(dest.offset(offset), val)?;
+                        let offset = tup_layout.field_offset(1).bytes() as isize;
+                        self.memory.write_bool(dest.offset(offset), false)?;
+                    },
+                    Err(EvalError::Overflow(l, r, op, val)) => {
+                        debug!("mathematical operation overflowed: {:?} {} {:?} => {:?}", l, op.to_hir_binop().as_str(), r, val);
+                        let offset = tup_layout.field_offset(0).bytes() as isize;
+                        self.memory.write_primval(dest.offset(offset), val)?;
+                        let offset = tup_layout.field_offset(1).bytes() as isize;
+                        self.memory.write_bool(dest.offset(offset), true)?;
+                    },
+                    Err(other) => return Err(other),
+                }
             }
 
             UnaryOp(un_op, ref operand) => {
diff --git a/src/lib.rs b/src/lib.rs
index 4bc5a07e3c..c881e79e61 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -14,6 +14,7 @@
 extern crate rustc_data_structures;
 extern crate rustc_mir;
 extern crate rustc_trans;
+extern crate rustc_const_math;
 extern crate syntax;
 #[macro_use] extern crate log;
 extern crate log_settings;
diff --git a/src/primval.rs b/src/primval.rs
index 5e1cdac45a..b1900874a9 100644
--- a/src/primval.rs
+++ b/src/primval.rs
@@ -17,21 +17,32 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
     use rustc::mir::repr::BinOp::*;
     use self::PrimVal::*;
 
+    macro_rules! overflow {
+        ($v:ident, $v2:ident, $l:ident, $op:ident, $r:ident) => ({
+            let (val, of) = $l.$op($r);
+            if of {
+                return Err(EvalError::Overflow($v($l), $v2($r), bin_op, $v(val)));
+            } else {
+                $v(val)
+            }
+        })
+    }
+
     macro_rules! int_binops {
         ($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 % $r),
+                Add    => overflow!($v, $v, $l, overflowing_add, $r),
+                Sub    => overflow!($v, $v, $l, overflowing_sub, $r),
+                Mul    => overflow!($v, $v, $l, overflowing_mul, $r),
+                Div    => overflow!($v, $v, $l, overflowing_div, $r),
+                Rem    => overflow!($v, $v, $l, overflowing_rem, $r),
                 BitXor => $v($l ^ $r),
                 BitAnd => $v($l & $r),
                 BitOr  => $v($l | $r),
 
-                // TODO(solson): Can have differently-typed RHS.
-                Shl => $v($l << $r),
-                Shr => $v($l >> $r),
+                // these have already been handled
+                Shl => unreachable!(),
+                Shr => unreachable!(),
 
                 Eq => Bool($l == $r),
                 Ne => Bool($l != $r),
@@ -53,6 +64,45 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
         }
     }
 
+    match bin_op {
+        // can have rhs with a different numeric type
+        Shl | Shr => {
+            let r = match right {
+                I8(i) if i >= 0 => i as u32,
+                I16(i) if i >= 0 => i as u32,
+                I32(i) if i >= 0 => i as u32,
+                I64(i) if i >= 0 && i as i32 as i64 == i => i as u32,
+                U8(i) => i as u32,
+                U16(i) => i as u32,
+                U32(i) => i,
+                U64(i) if i as u32 as u64 == i => i as u32,
+                _ => return Err(EvalError::InvalidBitShiftRhs(right)),
+            };
+            macro_rules! shift {
+                ($v:ident, $l:ident, $r:ident) => ({
+                    match bin_op {
+                        Shl => overflow!($v, U32, $l, overflowing_shl, $r),
+                        Shr => overflow!($v, U32, $l, overflowing_shr, $r),
+                        _ => unreachable!(),
+                    }
+                })
+            }
+            let val = match left {
+                I8(l) => shift!(I8, l, r),
+                I16(l) => shift!(I16, l, r),
+                I32(l) => shift!(I32, l, r),
+                I64(l) => shift!(I64, l, r),
+                U8(l) => shift!(U8, l, r),
+                U16(l) => shift!(U16, l, r),
+                U32(l) => shift!(U32, l, r),
+                U64(l) => shift!(U64, l, r),
+                _ => unreachable!(),
+            };
+            return Ok(val);
+        },
+        _ => {},
+    }
+
     let val = match (left, right) {
         (I8(l),  I8(r))  => int_binops!(I8, l, r),
         (I16(l), I16(r)) => int_binops!(I16, l, r),
diff --git a/tests/compiletest.rs b/tests/compiletest.rs
index 66b94ad88d..6869eb1eef 100644
--- a/tests/compiletest.rs
+++ b/tests/compiletest.rs
@@ -79,11 +79,11 @@ fn compile_test() {
                     writeln!(stderr.lock(), "FAILED: {}", e).unwrap();
                 },
             }
+            if failed {
+                panic!("some tests failed");
+            }
         }
         let stderr = std::io::stderr();
         writeln!(stderr.lock(), "").unwrap();
     });
-    if failed {
-        panic!("some tests failed");
-    }
 }

From 3ba4f6db04487929b2eecfc645fa9f4d8c54dfea Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Fri, 17 Jun 2016 15:16:41 +0200
Subject: [PATCH 02/18] remove code repetition and fix overflowing intrinsics

---
 src/interpreter/mod.rs | 191 +++++++++++++++++++++--------------------
 src/lib.rs             |   1 -
 tests/compiletest.rs   |   8 +-
 tests/run-pass/ints.rs |  15 +---
 4 files changed, 102 insertions(+), 113 deletions(-)

diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index 6d367a3be2..be8648ee30 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -515,9 +515,9 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
                 let name = self.tcx.item_name(def_id).as_str();
                 match fn_ty.sig.0.output {
                     ty::FnConverging(ty) => {
-                        let size = self.type_size(ty);
+                        let layout = self.type_layout(ty);
                         let ret = return_ptr.unwrap();
-                        self.call_intrinsic(&name, substs, args, ret, size)
+                        self.call_intrinsic(&name, substs, args, ret, layout)
                     }
                     ty::FnDiverging => unimplemented!(),
                 }
@@ -667,87 +667,126 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
         Ok(if not_null { nndiscr } else { 1 - nndiscr })
     }
 
+    fn intrinsic_with_overflow(
+        &mut self,
+        op: mir::BinOp,
+        left: &mir::Operand<'tcx>,
+        right: &mir::Operand<'tcx>,
+        dest: Pointer,
+        dest_layout: &'tcx Layout,
+    ) -> EvalResult<'tcx, ()> {
+        use rustc::ty::layout::Layout::*;
+        let tup_layout = match *dest_layout {
+            Univariant { ref variant, .. } => variant,
+            _ => panic!("checked bin op returns something other than a tuple"),
+        };
+
+        let overflowed = self.intrinsic_overflowing(op, left, right, dest)?;
+        let offset = tup_layout.field_offset(1).bytes() as isize;
+        self.memory.write_bool(dest.offset(offset), overflowed)
+    }
+
+    fn math(
+        &mut self,
+        op: mir::BinOp,
+        left: &mir::Operand<'tcx>,
+        right: &mir::Operand<'tcx>,
+    ) -> EvalResult<'tcx, PrimVal> {
+        let left_ptr = self.eval_operand(left)?;
+        let left_ty = self.operand_ty(left);
+        let left_val = self.read_primval(left_ptr, left_ty)?;
+
+        let right_ptr = self.eval_operand(right)?;
+        let right_ty = self.operand_ty(right);
+        let right_val = self.read_primval(right_ptr, right_ty)?;
+
+        primval::binary_op(op, left_val, right_val)
+    }
+
+    fn intrinsic_overflowing(
+        &mut self,
+        op: mir::BinOp,
+        left: &mir::Operand<'tcx>,
+        right: &mir::Operand<'tcx>,
+        dest: Pointer,
+    ) -> EvalResult<'tcx, bool> {
+        match self.math(op, left, right) {
+            Ok(val) => {
+                self.memory.write_primval(dest, val)?;
+                Ok(false)
+            },
+            Err(EvalError::Overflow(l, r, op, val)) => {
+                debug!("operation overflowed: {:?} {} {:?} => {:?}", l, op.to_hir_binop().as_str(), r, val);
+                self.memory.write_primval(dest, val)?;
+                Ok(true)
+            },
+            Err(other) => Err(other),
+        }
+    }
+
     fn call_intrinsic(
         &mut self,
         name: &str,
         substs: &'tcx Substs<'tcx>,
         args: &[mir::Operand<'tcx>],
         dest: Pointer,
-        dest_size: usize
+        dest_layout: &'tcx Layout,
     ) -> EvalResult<'tcx, ()> {
         let args_res: EvalResult<Vec<Pointer>> = args.iter()
             .map(|arg| self.eval_operand(arg))
             .collect();
-        let args = args_res?;
+        let args_ptrs = args_res?;
+
+        let pointer_size = self.memory.pointer_size;
 
         match name {
-            // FIXME(solson): Handle different integer types correctly.
-            "add_with_overflow" => {
-                let ty = *substs.types.get(subst::FnSpace, 0);
-                let size = self.type_size(ty);
-                let left = self.memory.read_int(args[0], size)?;
-                let right = self.memory.read_int(args[1], size)?;
-                let (n, overflowed) = unsafe {
-                    ::std::intrinsics::add_with_overflow::<i64>(left, right)
-                };
-                self.memory.write_int(dest, n, size)?;
-                self.memory.write_bool(dest.offset(size as isize), overflowed)?;
-            }
+            "add_with_overflow" => self.intrinsic_with_overflow(mir::BinOp::Add, &args[0], &args[1], dest, dest_layout)?,
+            "sub_with_overflow" => self.intrinsic_with_overflow(mir::BinOp::Sub, &args[0], &args[1], dest, dest_layout)?,
+            "mul_with_overflow" => self.intrinsic_with_overflow(mir::BinOp::Mul, &args[0], &args[1], dest, dest_layout)?,
 
+            // FIXME: turn into an assertion to catch wrong `assume` that would cause UB in llvm
             "assume" => {}
 
             "copy_nonoverlapping" => {
                 let elem_ty = *substs.types.get(subst::FnSpace, 0);
                 let elem_size = self.type_size(elem_ty);
-                let src = self.memory.read_ptr(args[0])?;
-                let dest = self.memory.read_ptr(args[1])?;
-                let count = self.memory.read_isize(args[2])?;
+                let src = self.memory.read_ptr(args_ptrs[0])?;
+                let dest = self.memory.read_ptr(args_ptrs[1])?;
+                let count = self.memory.read_isize(args_ptrs[2])?;
                 self.memory.copy(src, dest, count as usize * elem_size)?;
             }
 
             "discriminant_value" => {
                 let ty = *substs.types.get(subst::FnSpace, 0);
-                let adt_ptr = self.memory.read_ptr(args[0])?;
+                let adt_ptr = self.memory.read_ptr(args_ptrs[0])?;
                 let discr_val = self.read_discriminant_value(adt_ptr, ty)?;
-                self.memory.write_uint(dest, discr_val, dest_size)?;
+                self.memory.write_uint(dest, discr_val, 8)?;
             }
 
             "forget" => {
                 let arg_ty = *substs.types.get(subst::FnSpace, 0);
                 let arg_size = self.type_size(arg_ty);
-                self.memory.drop_fill(args[0], arg_size)?;
+                self.memory.drop_fill(args_ptrs[0], arg_size)?;
             }
 
-            "init" => self.memory.write_repeat(dest, 0, dest_size)?,
+            "init" => self.memory.write_repeat(dest, 0, dest_layout.size(&self.tcx.data_layout).bytes() as usize)?,
 
             "min_align_of" => {
-                self.memory.write_int(dest, 1, dest_size)?;
+                // FIXME: use correct value
+                self.memory.write_int(dest, 1, pointer_size)?;
             }
 
             "move_val_init" => {
                 let ty = *substs.types.get(subst::FnSpace, 0);
-                let ptr = self.memory.read_ptr(args[0])?;
-                self.move_(args[1], ptr, ty)?;
-            }
-
-            // FIXME(solson): Handle different integer types correctly.
-            "mul_with_overflow" => {
-                let ty = *substs.types.get(subst::FnSpace, 0);
-                let size = self.type_size(ty);
-                let left = self.memory.read_int(args[0], size)?;
-                let right = self.memory.read_int(args[1], size)?;
-                let (n, overflowed) = unsafe {
-                    ::std::intrinsics::mul_with_overflow::<i64>(left, right)
-                };
-                self.memory.write_int(dest, n, size)?;
-                self.memory.write_bool(dest.offset(size as isize), overflowed)?;
+                let ptr = self.memory.read_ptr(args_ptrs[0])?;
+                self.move_(args_ptrs[1], ptr, ty)?;
             }
 
             "offset" => {
                 let pointee_ty = *substs.types.get(subst::FnSpace, 0);
                 let pointee_size = self.type_size(pointee_ty) as isize;
-                let ptr_arg = args[0];
-                let offset = self.memory.read_isize(args[1])?;
+                let ptr_arg = args_ptrs[0];
+                let offset = self.memory.read_isize(args_ptrs[1])?;
 
                 match self.memory.read_ptr(ptr_arg) {
                     Ok(ptr) => {
@@ -763,35 +802,35 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
                 }
             }
 
-            // FIXME(solson): Handle different integer types correctly. Use primvals?
             "overflowing_sub" => {
-                let ty = *substs.types.get(subst::FnSpace, 0);
-                let size = self.type_size(ty);
-                let left = self.memory.read_int(args[0], size)?;
-                let right = self.memory.read_int(args[1], size)?;
-                let n = left.wrapping_sub(right);
-                self.memory.write_int(dest, n, size)?;
+                self.intrinsic_overflowing(mir::BinOp::Sub, &args[0], &args[1], dest)?;
+            }
+            "overflowing_mul" => {
+                self.intrinsic_overflowing(mir::BinOp::Mul, &args[0], &args[1], dest)?;
+            }
+            "overflowing_add" => {
+                self.intrinsic_overflowing(mir::BinOp::Add, &args[0], &args[1], dest)?;
             }
 
             "size_of" => {
                 let ty = *substs.types.get(subst::FnSpace, 0);
                 let size = self.type_size(ty) as u64;
-                self.memory.write_uint(dest, size, dest_size)?;
+                self.memory.write_uint(dest, size, pointer_size)?;
             }
 
             "size_of_val" => {
                 let ty = *substs.types.get(subst::FnSpace, 0);
                 if self.type_is_sized(ty) {
                     let size = self.type_size(ty) as u64;
-                    self.memory.write_uint(dest, size, dest_size)?;
+                    self.memory.write_uint(dest, size, pointer_size)?;
                 } else {
                     match ty.sty {
                         ty::TySlice(_) | ty::TyStr => {
                             let elem_ty = ty.sequence_element_type(self.tcx);
                             let elem_size = self.type_size(elem_ty) as u64;
                             let ptr_size = self.memory.pointer_size as isize;
-                            let n = self.memory.read_usize(args[0].offset(ptr_size))?;
-                            self.memory.write_uint(dest, n * elem_size, dest_size)?;
+                            let n = self.memory.read_usize(args_ptrs[0].offset(ptr_size))?;
+                            self.memory.write_uint(dest, n * elem_size, pointer_size)?;
                         }
 
                         _ => return Err(EvalError::Unimplemented(format!("unimplemented: size_of_val::<{:?}>", ty))),
@@ -801,9 +840,9 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
 
             "transmute" => {
                 let ty = *substs.types.get(subst::FnSpace, 0);
-                self.move_(args[0], dest, ty)?;
+                self.move_(args_ptrs[0], dest, ty)?;
             }
-            "uninit" => self.memory.mark_definedness(dest, dest_size, false)?,
+            "uninit" => self.memory.mark_definedness(dest, dest_layout.size(&self.tcx.data_layout).bytes() as usize, false)?,
 
             name => return Err(EvalError::Unimplemented(format!("unimplemented intrinsic: {}", name))),
         }
@@ -908,50 +947,12 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
             }
 
             BinaryOp(bin_op, ref left, ref right) => {
-                let left_ptr = self.eval_operand(left)?;
-                let left_ty = self.operand_ty(left);
-                let left_val = self.read_primval(left_ptr, left_ty)?;
-
-                let right_ptr = self.eval_operand(right)?;
-                let right_ty = self.operand_ty(right);
-                let right_val = self.read_primval(right_ptr, right_ty)?;
-
-                let val = primval::binary_op(bin_op, left_val, right_val)?;
-                self.memory.write_primval(dest, val)?;
+                let result = self.math(bin_op, left, right)?;
+                self.memory.write_primval(dest, result)?;
             }
 
-            // FIXME(solson): Factor this out with BinaryOp.
             CheckedBinaryOp(bin_op, ref left, ref right) => {
-                let left_ptr = self.eval_operand(left)?;
-                let left_ty = self.operand_ty(left);
-                let left_val = self.read_primval(left_ptr, left_ty)?;
-
-                let right_ptr = self.eval_operand(right)?;
-                let right_ty = self.operand_ty(right);
-                let right_val = self.read_primval(right_ptr, right_ty)?;
-
-                use rustc::ty::layout::Layout::*;
-                let tup_layout = match *dest_layout {
-                    Univariant { ref variant, .. } => variant,
-                    _ => panic!("checked bin op returns something other than a tuple"),
-                };
-
-                match primval::binary_op(bin_op, left_val, right_val) {
-                    Ok(val) => {
-                        let offset = tup_layout.field_offset(0).bytes() as isize;
-                        self.memory.write_primval(dest.offset(offset), val)?;
-                        let offset = tup_layout.field_offset(1).bytes() as isize;
-                        self.memory.write_bool(dest.offset(offset), false)?;
-                    },
-                    Err(EvalError::Overflow(l, r, op, val)) => {
-                        debug!("mathematical operation overflowed: {:?} {} {:?} => {:?}", l, op.to_hir_binop().as_str(), r, val);
-                        let offset = tup_layout.field_offset(0).bytes() as isize;
-                        self.memory.write_primval(dest.offset(offset), val)?;
-                        let offset = tup_layout.field_offset(1).bytes() as isize;
-                        self.memory.write_bool(dest.offset(offset), true)?;
-                    },
-                    Err(other) => return Err(other),
-                }
+                self.intrinsic_with_overflow(bin_op, left, right, dest, dest_layout)?;
             }
 
             UnaryOp(un_op, ref operand) => {
diff --git a/src/lib.rs b/src/lib.rs
index c881e79e61..c983a3f716 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,7 +2,6 @@
     btree_range,
     collections,
     collections_bound,
-    core_intrinsics,
     filling_drop,
     question_mark,
     rustc_private,
diff --git a/tests/compiletest.rs b/tests/compiletest.rs
index 6869eb1eef..b6c46ba4b0 100644
--- a/tests/compiletest.rs
+++ b/tests/compiletest.rs
@@ -38,7 +38,6 @@ fn for_all_targets<F: FnMut(String)>(sysroot: &str, mut f: F) {
 
 #[test]
 fn compile_test() {
-    let mut failed = false;
     // Taken from https://github.com/Manishearth/rust-clippy/pull/911.
     let home = option_env!("RUSTUP_HOME").or(option_env!("MULTIRUST_HOME"));
     let toolchain = option_env!("RUSTUP_TOOLCHAIN").or(option_env!("MULTIRUST_TOOLCHAIN"));
@@ -69,19 +68,16 @@ fn compile_test() {
             match cmd.output() {
                 Ok(ref output) if output.status.success() => writeln!(stderr.lock(), "ok").unwrap(),
                 Ok(output) => {
-                    failed = true;
                     writeln!(stderr.lock(), "FAILED with exit code {}", output.status.code().unwrap_or(0)).unwrap();
                     writeln!(stderr.lock(), "stdout: \n {}", std::str::from_utf8(&output.stdout).unwrap()).unwrap();
                     writeln!(stderr.lock(), "stderr: \n {}", std::str::from_utf8(&output.stderr).unwrap()).unwrap();
+                    panic!("some tests failed");
                 }
                 Err(e) => {
-                    failed = true;
                     writeln!(stderr.lock(), "FAILED: {}", e).unwrap();
+                    panic!("some tests failed");
                 },
             }
-            if failed {
-                panic!("some tests failed");
-            }
         }
         let stderr = std::io::stderr();
         writeln!(stderr.lock(), "").unwrap();
diff --git a/tests/run-pass/ints.rs b/tests/run-pass/ints.rs
index 76091be358..4f23b5ec9c 100644
--- a/tests/run-pass/ints.rs
+++ b/tests/run-pass/ints.rs
@@ -1,34 +1,25 @@
-#![feature(custom_attribute)]
-#![allow(dead_code, unused_attributes)]
-
-#[miri_run]
 fn ret() -> i64 {
     1
 }
 
-#[miri_run]
 fn neg() -> i64 {
     -1
 }
 
-#[miri_run]
 fn add() -> i64 {
     1 + 2
 }
 
-#[miri_run]
 fn indirect_add() -> i64 {
     let x = 1;
     let y = 2;
     x + y
 }
 
-#[miri_run]
 fn arith() -> i32 {
     3*3 + 4*4
 }
 
-#[miri_run]
 fn match_int() -> i16 {
     let n = 2;
     match n {
@@ -40,7 +31,6 @@ fn match_int() -> i16 {
     }
 }
 
-#[miri_run]
 fn match_int_range() -> i64 {
     let n = 42;
     match n {
@@ -53,7 +43,6 @@ fn match_int_range() -> i64 {
     }
 }
 
-#[miri_run]
 fn main() {
     assert_eq!(ret(), 1);
     assert_eq!(neg(), -1);
@@ -62,4 +51,8 @@ fn main() {
     assert_eq!(arith(), 5*5);
     assert_eq!(match_int(), 20);
     assert_eq!(match_int_range(), 4);
+    assert_eq!(i64::min_value().overflowing_mul(-1), (i64::min_value(), true));
+    assert_eq!(i32::min_value().overflowing_mul(-1), (i32::min_value(), true));
+    assert_eq!(i16::min_value().overflowing_mul(-1), (i16::min_value(), true));
+    assert_eq!(i8::min_value().overflowing_mul(-1), (i8::min_value(), true));
 }

From 6376ef42286d83aed3dbb8778db98abf1ef0a39a Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Fri, 17 Jun 2016 15:21:01 +0200
Subject: [PATCH 03/18] run the *compiled* run-pass tests on the host machine

---
 tests/compiletest.rs | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/tests/compiletest.rs b/tests/compiletest.rs
index b6c46ba4b0..e57869766b 100644
--- a/tests/compiletest.rs
+++ b/tests/compiletest.rs
@@ -3,23 +3,32 @@ extern crate compiletest_rs as compiletest;
 use std::path::{PathBuf, Path};
 use std::io::Write;
 
-fn run_mode(dir: &'static str, mode: &'static str, sysroot: &str) {
+fn compile_fail(sysroot: &str) {
     // Disable rustc's new error fomatting. It breaks these tests.
     std::env::remove_var("RUST_NEW_ERROR_FORMAT");
     let flags = format!("--sysroot {} -Dwarnings", sysroot);
     for_all_targets(sysroot, |target| {
         let mut config = compiletest::default_config();
         config.host_rustcflags = Some(flags.clone());
-        config.mode = mode.parse().expect("Invalid mode");
+        config.mode = "compile-fail".parse().expect("Invalid mode");
         config.run_lib_path = Path::new(sysroot).join("lib").join("rustlib").join(&target).join("lib");
         config.rustc_path = "target/debug/miri".into();
-        config.src_base = PathBuf::from(format!("tests/{}", dir));
+        config.src_base = PathBuf::from("tests/compile-fail".to_string());
         config.target = target.to_owned();
         config.target_rustcflags = Some(flags.clone());
         compiletest::run_tests(&config);
     });
 }
 
+fn run_pass() {
+    // Disable rustc's new error fomatting. It breaks these tests.
+    std::env::remove_var("RUST_NEW_ERROR_FORMAT");
+    let mut config = compiletest::default_config();
+    config.mode = "run-pass".parse().expect("Invalid mode");
+    config.src_base = PathBuf::from("tests/run-pass".to_string());
+    compiletest::run_tests(&config);
+}
+
 fn for_all_targets<F: FnMut(String)>(sysroot: &str, mut f: F) {
     for target in std::fs::read_dir(format!("{}/lib/rustlib/", sysroot)).unwrap() {
         let target = target.unwrap();
@@ -47,7 +56,8 @@ fn compile_test() {
             .expect("need to specify RUST_SYSROOT env var or use rustup or multirust")
             .to_owned(),
     };
-    run_mode("compile-fail", "compile-fail", &sysroot);
+    compile_fail(&sysroot);
+    run_pass();
     for_all_targets(&sysroot, |target| {
         for file in std::fs::read_dir("tests/run-pass").unwrap() {
             let file = file.unwrap();

From 4f48bef8969120da73154ceb7bf16aa07dc94657 Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Fri, 17 Jun 2016 15:48:15 +0200
Subject: [PATCH 04/18] cfail test for std::env::args()

---
 tests/compile-fail/env_args.rs | 6 ++++++
 1 file changed, 6 insertions(+)
 create mode 100644 tests/compile-fail/env_args.rs

diff --git a/tests/compile-fail/env_args.rs b/tests/compile-fail/env_args.rs
new file mode 100644
index 0000000000..b0068785e1
--- /dev/null
+++ b/tests/compile-fail/env_args.rs
@@ -0,0 +1,6 @@
+//error-pattern: no mir for `std
+
+fn main() {
+    let x = std::env::args();
+    assert_eq!(x.count(), 1);
+}

From e3a2bf84e26f0be966297d75b47b9d121feb3bf5 Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Fri, 17 Jun 2016 16:03:11 +0200
Subject: [PATCH 05/18] clippy

---
 src/interpreter/mod.rs | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index be8648ee30..abc695de4d 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -1127,9 +1127,7 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
 
                         // Hack to support fat pointer -> thin pointer casts to keep tests for
                         // other things passing for now.
-                        let is_fat_ptr_cast = pointee_type(src_ty).map(|ty| {
-                            !self.type_is_sized(ty)
-                        }).unwrap_or(false);
+                        let is_fat_ptr_cast = pointee_type(src_ty).map_or(false, |ty| !self.type_is_sized(ty));
 
                         if dest_size == src_size || is_fat_ptr_cast {
                             self.memory.copy(src, dest, dest_size)?;

From 00eb198a82376eeb608c32e6d4252743f6dcfc87 Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Fri, 17 Jun 2016 16:49:06 +0200
Subject: [PATCH 06/18] implement fn -> unsafe fn pointer casts

---
 src/interpreter/mod.rs                    | 11 ++++++++++-
 tests/compile-fail/cast_fn_ptr_unsafe.rs  | 10 ++++++++++
 tests/compile-fail/cast_fn_ptr_unsafe2.rs | 10 ++++++++++
 tests/run-pass/cast_fn_ptr_unsafe.rs      |  8 ++++++++
 4 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 tests/compile-fail/cast_fn_ptr_unsafe.rs
 create mode 100644 tests/compile-fail/cast_fn_ptr_unsafe2.rs
 create mode 100644 tests/run-pass/cast_fn_ptr_unsafe.rs

diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index abc695de4d..7ae0867522 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -1144,7 +1144,16 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
                         ref other => panic!("reify fn pointer on {:?}", other),
                     },
 
-                    _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
+                    UnsafeFnPointer => match dest_ty.sty {
+                        ty::TyFnPtr(unsafe_fn_ty) => {
+                            let src = self.eval_operand(operand)?;
+                            let ptr = self.memory.read_ptr(src)?;
+                            let fn_def = self.memory.get_fn(ptr.alloc_id)?;
+                            let fn_ptr = self.memory.create_fn_ptr(fn_def.def_id, fn_def.substs, unsafe_fn_ty);
+                            self.memory.write_ptr(dest, fn_ptr)?;
+                        },
+                        ref other => panic!("fn to unsafe fn cast on {:?}", other),
+                    },
                 }
             }
 
diff --git a/tests/compile-fail/cast_fn_ptr_unsafe.rs b/tests/compile-fail/cast_fn_ptr_unsafe.rs
new file mode 100644
index 0000000000..225cd1391b
--- /dev/null
+++ b/tests/compile-fail/cast_fn_ptr_unsafe.rs
@@ -0,0 +1,10 @@
+// just making sure that fn -> unsafe fn casts are handled by rustc so miri doesn't have to
+fn main() {
+    fn f() {}
+
+    let g = f as fn() as unsafe fn(i32); //~ERROR: non-scalar cast: `fn()` as `unsafe fn(i32)`
+
+    unsafe {
+        g(42);
+    }
+}
diff --git a/tests/compile-fail/cast_fn_ptr_unsafe2.rs b/tests/compile-fail/cast_fn_ptr_unsafe2.rs
new file mode 100644
index 0000000000..c3a2fb9556
--- /dev/null
+++ b/tests/compile-fail/cast_fn_ptr_unsafe2.rs
@@ -0,0 +1,10 @@
+// just making sure that fn -> unsafe fn casts are handled by rustc so miri doesn't have to
+fn main() {
+    fn f() {}
+
+    let g = f as fn() as fn(i32) as unsafe fn(i32); //~ERROR: non-scalar cast: `fn()` as `fn(i32)`
+
+    unsafe {
+        g(42);
+    }
+}
diff --git a/tests/run-pass/cast_fn_ptr_unsafe.rs b/tests/run-pass/cast_fn_ptr_unsafe.rs
new file mode 100644
index 0000000000..0cabb369bf
--- /dev/null
+++ b/tests/run-pass/cast_fn_ptr_unsafe.rs
@@ -0,0 +1,8 @@
+fn main() {
+    fn f() {}
+
+    let g = f as fn() as unsafe fn();
+    unsafe {
+        g();
+    }
+}

From 874d683bfa1b916cb9e3bc57d132a62afdd411fe Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 20 Jun 2016 10:34:34 +0200
Subject: [PATCH 07/18] improve method names and add documentation

---
 src/interpreter/mod.rs | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index 7ae0867522..0492a3dfc7 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -667,6 +667,8 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
         Ok(if not_null { nndiscr } else { 1 - nndiscr })
     }
 
+    /// applies the binary operation `op` to the two operands and writes a tuple of the result
+    /// and a boolean signifying the potential overflow to the destination
     fn intrinsic_with_overflow(
         &mut self,
         op: mir::BinOp,
@@ -686,7 +688,8 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
         self.memory.write_bool(dest.offset(offset), overflowed)
     }
 
-    fn math(
+    /// extracts the lhs and rhs primval from the operands and applies the binary op
+    fn eval_binop(
         &mut self,
         op: mir::BinOp,
         left: &mir::Operand<'tcx>,
@@ -703,6 +706,7 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
         primval::binary_op(op, left_val, right_val)
     }
 
+    /// applies the binary operation `op` to the arguments and writes the result to the destination
     fn intrinsic_overflowing(
         &mut self,
         op: mir::BinOp,
@@ -710,7 +714,7 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
         right: &mir::Operand<'tcx>,
         dest: Pointer,
     ) -> EvalResult<'tcx, bool> {
-        match self.math(op, left, right) {
+        match self.eval_binop(op, left, right) {
             Ok(val) => {
                 self.memory.write_primval(dest, val)?;
                 Ok(false)
@@ -947,7 +951,7 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
             }
 
             BinaryOp(bin_op, ref left, ref right) => {
-                let result = self.math(bin_op, left, right)?;
+                let result = self.eval_binop(bin_op, left, right)?;
                 self.memory.write_primval(dest, result)?;
             }
 

From d9776427b465283bb2368be0301bf0e5cd1459eb Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 20 Jun 2016 10:34:55 +0200
Subject: [PATCH 08/18] compiletest 2.0 uses json errors and doesn't depend on
 the output format anymore

---
 tests/compiletest.rs | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/tests/compiletest.rs b/tests/compiletest.rs
index e57869766b..ffe35ad7e4 100644
--- a/tests/compiletest.rs
+++ b/tests/compiletest.rs
@@ -4,8 +4,6 @@ use std::path::{PathBuf, Path};
 use std::io::Write;
 
 fn compile_fail(sysroot: &str) {
-    // Disable rustc's new error fomatting. It breaks these tests.
-    std::env::remove_var("RUST_NEW_ERROR_FORMAT");
     let flags = format!("--sysroot {} -Dwarnings", sysroot);
     for_all_targets(sysroot, |target| {
         let mut config = compiletest::default_config();
@@ -21,8 +19,6 @@ fn compile_fail(sysroot: &str) {
 }
 
 fn run_pass() {
-    // Disable rustc's new error fomatting. It breaks these tests.
-    std::env::remove_var("RUST_NEW_ERROR_FORMAT");
     let mut config = compiletest::default_config();
     config.mode = "run-pass".parse().expect("Invalid mode");
     config.src_base = PathBuf::from("tests/run-pass".to_string());

From e90ee1674ae2fd32bc5e07a3a52562c45b273c56 Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 20 Jun 2016 10:35:15 +0200
Subject: [PATCH 09/18] fix comparing of function pointers

---
 src/interpreter/mod.rs              |  4 ++++
 src/memory.rs                       | 26 ++++++++++++++++++--------
 src/primval.rs                      | 14 +++++++++++++-
 tests/run-pass/function_pointers.rs |  2 ++
 4 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index 0492a3dfc7..739e987a37 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -1404,6 +1404,10 @@ 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::TyFnDef(def_id, substs, fn_ty)) => {
+                PrimVal::FnPtr(self.memory.create_fn_ptr(def_id, substs, fn_ty))
+            },
+            (_, &ty::TyFnPtr(_)) => self.memory.read_ptr(ptr).map(PrimVal::FnPtr)?,
             (_, &ty::TyRef(_, ty::TypeAndMut { ty, .. })) |
             (_, &ty::TyRawPtr(ty::TypeAndMut { ty, .. })) => {
                 if self.type_is_sized(ty) {
diff --git a/src/memory.rs b/src/memory.rs
index e20d92207d..a7fecd773c 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -42,7 +42,7 @@ impl Pointer {
     }
 }
 
-#[derive(Debug, Copy, Clone)]
+#[derive(Debug, Copy, Clone, Hash, Eq, PartialEq)]
 pub struct FunctionDefinition<'tcx> {
     pub def_id: DefId,
     pub substs: &'tcx Substs<'tcx>,
@@ -59,6 +59,8 @@ pub struct Memory<'tcx> {
     /// Function "allocations". They exist solely so pointers have something to point to, and
     /// we can figure out what they point to.
     functions: HashMap<AllocId, FunctionDefinition<'tcx>>,
+    /// Inverse map of `functions` so we don't allocate a new pointer every time we need one
+    function_definitions: HashMap<FunctionDefinition<'tcx>, AllocId>,
     next_id: AllocId,
     pub pointer_size: usize,
 }
@@ -69,22 +71,29 @@ impl<'tcx> Memory<'tcx> {
         Memory {
             alloc_map: HashMap::new(),
             functions: HashMap::new(),
+            function_definitions: HashMap::new(),
             next_id: AllocId(0),
             pointer_size: pointer_size,
         }
     }
 
-    // FIXME: never create two pointers to the same def_id + substs combination
-    // maybe re-use the statics cache of the EvalContext?
     pub fn create_fn_ptr(&mut self, def_id: DefId, substs: &'tcx Substs<'tcx>, fn_ty: &'tcx BareFnTy<'tcx>) -> Pointer {
-        let id = self.next_id;
-        debug!("creating fn ptr: {}", id);
-        self.next_id.0 += 1;
-        self.functions.insert(id, FunctionDefinition {
+        let def = FunctionDefinition {
             def_id: def_id,
             substs: substs,
             fn_ty: fn_ty,
-        });
+        };
+        if let Some(&alloc_id) = self.function_definitions.get(&def) {
+            return Pointer {
+                alloc_id: alloc_id,
+                offset: 0,
+            };
+        }
+        let id = self.next_id;
+        debug!("creating fn ptr: {}", id);
+        self.next_id.0 += 1;
+        self.functions.insert(id, def);
+        self.function_definitions.insert(def, id);
         Pointer {
             alloc_id: id,
             offset: 0,
@@ -361,6 +370,7 @@ impl<'tcx> Memory<'tcx> {
             PrimVal::U32(n)  => self.write_uint(ptr, n as u64, 4),
             PrimVal::U64(n)  => self.write_uint(ptr, n as u64, 8),
             PrimVal::IntegerPtr(n) => self.write_uint(ptr, n as u64, pointer_size),
+            PrimVal::FnPtr(_p) |
             PrimVal::AbstractPtr(_p) => unimplemented!(),
         }
     }
diff --git a/src/primval.rs b/src/primval.rs
index b1900874a9..67ef58948f 100644
--- a/src/primval.rs
+++ b/src/primval.rs
@@ -10,6 +10,7 @@ pub enum PrimVal {
     U8(u8), U16(u16), U32(u32), U64(u64),
 
     AbstractPtr(Pointer),
+    FnPtr(Pointer),
     IntegerPtr(u64),
 }
 
@@ -130,9 +131,20 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
 
         (IntegerPtr(l), IntegerPtr(r)) => int_binops!(IntegerPtr, l, r),
 
-        (AbstractPtr(_), IntegerPtr(_)) | (IntegerPtr(_), AbstractPtr(_)) =>
+        (AbstractPtr(_), IntegerPtr(_)) |
+        (IntegerPtr(_), AbstractPtr(_)) |
+        (FnPtr(_), AbstractPtr(_)) |
+        (AbstractPtr(_), FnPtr(_)) |
+        (FnPtr(_), IntegerPtr(_)) |
+        (IntegerPtr(_), FnPtr(_)) =>
             return unrelated_ptr_ops(bin_op),
 
+        (FnPtr(l_ptr), FnPtr(r_ptr)) => match bin_op {
+            Eq => Bool(l_ptr == r_ptr),
+            Ne => Bool(l_ptr != r_ptr),
+            _ => return Err(EvalError::Unimplemented(format!("unimplemented fn ptr comparison: {:?}", bin_op))),
+        },
+
         (AbstractPtr(l_ptr), AbstractPtr(r_ptr)) => {
             if l_ptr.alloc_id != r_ptr.alloc_id {
                 return unrelated_ptr_ops(bin_op);
diff --git a/tests/run-pass/function_pointers.rs b/tests/run-pass/function_pointers.rs
index 8361a58ea4..2e75a5a3ea 100644
--- a/tests/run-pass/function_pointers.rs
+++ b/tests/run-pass/function_pointers.rs
@@ -12,4 +12,6 @@ fn call_fn_ptr() -> i32 {
 
 fn main() {
     assert_eq!(call_fn_ptr(), 42);
+    assert!(return_fn_ptr() == f);
+    assert!(return_fn_ptr() as unsafe fn() -> i32 == f as fn() -> i32 as unsafe fn() -> i32);
 }

From ed4af21605ca5939a8d45f52975632be95cd210a Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 20 Jun 2016 12:33:54 +0200
Subject: [PATCH 10/18] fix master

---
 tests/run-pass/specialization.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tests/run-pass/specialization.rs b/tests/run-pass/specialization.rs
index 9570b5b58e..13894926d3 100644
--- a/tests/run-pass/specialization.rs
+++ b/tests/run-pass/specialization.rs
@@ -1,3 +1,5 @@
+#![feature(specialization)]
+
 trait IsUnit {
     fn is_unit() -> bool;
 }

From b9ac85d2a94e94dd5c81d5988b0adf60c1868e0c Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 20 Jun 2016 16:52:43 +0200
Subject: [PATCH 11/18] rustc does overflow checking for us, don't duplicate
 it.

---
 src/error.rs           |  5 -----
 src/interpreter/mod.rs | 23 ++++++++---------------
 src/primval.rs         | 13 +++++++------
 3 files changed, 15 insertions(+), 26 deletions(-)

diff --git a/src/error.rs b/src/error.rs
index 885f5af632..3962c09dee 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -30,7 +30,6 @@ pub enum EvalError<'tcx> {
     ArrayIndexOutOfBounds(Span, u64, u64),
     Math(Span, ConstMathErr),
     InvalidBitShiftRhs(PrimVal),
-    Overflow(PrimVal, PrimVal, mir::BinOp, PrimVal),
 }
 
 pub type EvalResult<'tcx, T> = Result<T, EvalError<'tcx>>;
@@ -71,8 +70,6 @@ impl<'tcx> Error for EvalError<'tcx> {
                 "mathematical operation failed",
             EvalError::InvalidBitShiftRhs(..) =>
                 "bit shift rhs negative or not an int",
-            EvalError::Overflow(..) =>
-                "mathematical operation overflowed",
         }
     }
 
@@ -92,8 +89,6 @@ impl<'tcx> fmt::Display for EvalError<'tcx> {
                 write!(f, "array index {} out of bounds {} at {:?}", index, len, span),
             EvalError::Math(span, ref err) =>
                 write!(f, "mathematical operation at {:?} failed with {:?}", span, err),
-            EvalError::Overflow(l, r, op, val) =>
-                write!(f, "mathematical operation overflowed: {:?} {} {:?} => {:?}", l, op.to_hir_binop().as_str(), r, val),
             _ => write!(f, "{}", self.description()),
         }
     }
diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index eaadfbd1df..4815421f24 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -688,13 +688,14 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
         self.memory.write_bool(dest.offset(offset), overflowed)
     }
 
-    /// extracts the lhs and rhs primval from the operands and applies the binary op
+    /// Extracts the lhs and rhs primval from the operands and applies the binary op.
+    /// Returns the result and whether the operation overflowed
     fn eval_binop(
         &mut self,
         op: mir::BinOp,
         left: &mir::Operand<'tcx>,
         right: &mir::Operand<'tcx>,
-    ) -> EvalResult<'tcx, PrimVal> {
+    ) -> EvalResult<'tcx, (PrimVal, bool)> {
         let left_ptr = self.eval_operand(left)?;
         let left_ty = self.operand_ty(left);
         let left_val = self.read_primval(left_ptr, left_ty)?;
@@ -714,18 +715,9 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
         right: &mir::Operand<'tcx>,
         dest: Pointer,
     ) -> EvalResult<'tcx, bool> {
-        match self.eval_binop(op, left, right) {
-            Ok(val) => {
-                self.memory.write_primval(dest, val)?;
-                Ok(false)
-            },
-            Err(EvalError::Overflow(l, r, op, val)) => {
-                debug!("operation overflowed: {:?} {} {:?} => {:?}", l, op.to_hir_binop().as_str(), r, val);
-                self.memory.write_primval(dest, val)?;
-                Ok(true)
-            },
-            Err(other) => Err(other),
-        }
+        let (val, overflow) = self.eval_binop(op, left, right)?;
+        self.memory.write_primval(dest, val)?;
+        Ok(overflow)
     }
 
     fn call_intrinsic(
@@ -951,7 +943,8 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
             }
 
             BinaryOp(bin_op, ref left, ref right) => {
-                let result = self.eval_binop(bin_op, left, right)?;
+                // ignore overflow bit, rustc inserts check branches for us
+                let result = self.eval_binop(bin_op, left, right)?.0;
                 self.memory.write_primval(dest, result)?;
             }
 
diff --git a/src/primval.rs b/src/primval.rs
index 67ef58948f..673aea4244 100644
--- a/src/primval.rs
+++ b/src/primval.rs
@@ -14,7 +14,8 @@ pub enum PrimVal {
     IntegerPtr(u64),
 }
 
-pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> EvalResult<'tcx, PrimVal> {
+/// returns the result of the operation and whether the operation overflowed
+pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> EvalResult<'tcx, (PrimVal, bool)> {
     use rustc::mir::repr::BinOp::*;
     use self::PrimVal::*;
 
@@ -22,7 +23,7 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
         ($v:ident, $v2:ident, $l:ident, $op:ident, $r:ident) => ({
             let (val, of) = $l.$op($r);
             if of {
-                return Err(EvalError::Overflow($v($l), $v2($r), bin_op, $v(val)));
+                return Ok(($v(val), true));
             } else {
                 $v(val)
             }
@@ -99,7 +100,7 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
                 U64(l) => shift!(U64, l, r),
                 _ => unreachable!(),
             };
-            return Ok(val);
+            return Ok((val, false));
         },
         _ => {},
     }
@@ -137,7 +138,7 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
         (AbstractPtr(_), FnPtr(_)) |
         (FnPtr(_), IntegerPtr(_)) |
         (IntegerPtr(_), FnPtr(_)) =>
-            return unrelated_ptr_ops(bin_op),
+            unrelated_ptr_ops(bin_op)?,
 
         (FnPtr(l_ptr), FnPtr(r_ptr)) => match bin_op {
             Eq => Bool(l_ptr == r_ptr),
@@ -147,7 +148,7 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
 
         (AbstractPtr(l_ptr), AbstractPtr(r_ptr)) => {
             if l_ptr.alloc_id != r_ptr.alloc_id {
-                return unrelated_ptr_ops(bin_op);
+                return Ok((unrelated_ptr_ops(bin_op)?, false));
             }
 
             let l = l_ptr.offset;
@@ -167,7 +168,7 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
         (l, r) => return Err(EvalError::Unimplemented(format!("unimplemented binary op: {:?}, {:?}, {:?}", l, r, bin_op))),
     };
 
-    Ok(val)
+    Ok((val, false))
 }
 
 pub fn unary_op<'tcx>(un_op: mir::UnOp, val: PrimVal) -> EvalResult<'tcx, PrimVal> {

From 68469be89bd7652cf12a0fe74fb6cd6c5915498d Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 20 Jun 2016 16:52:53 +0200
Subject: [PATCH 12/18] rename function cache member

---
 src/memory.rs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/memory.rs b/src/memory.rs
index a7fecd773c..be0cd0ef4f 100644
--- a/src/memory.rs
+++ b/src/memory.rs
@@ -60,7 +60,7 @@ pub struct Memory<'tcx> {
     /// we can figure out what they point to.
     functions: HashMap<AllocId, FunctionDefinition<'tcx>>,
     /// Inverse map of `functions` so we don't allocate a new pointer every time we need one
-    function_definitions: HashMap<FunctionDefinition<'tcx>, AllocId>,
+    function_alloc_cache: HashMap<FunctionDefinition<'tcx>, AllocId>,
     next_id: AllocId,
     pub pointer_size: usize,
 }
@@ -71,7 +71,7 @@ impl<'tcx> Memory<'tcx> {
         Memory {
             alloc_map: HashMap::new(),
             functions: HashMap::new(),
-            function_definitions: HashMap::new(),
+            function_alloc_cache: HashMap::new(),
             next_id: AllocId(0),
             pointer_size: pointer_size,
         }
@@ -83,7 +83,7 @@ impl<'tcx> Memory<'tcx> {
             substs: substs,
             fn_ty: fn_ty,
         };
-        if let Some(&alloc_id) = self.function_definitions.get(&def) {
+        if let Some(&alloc_id) = self.function_alloc_cache.get(&def) {
             return Pointer {
                 alloc_id: alloc_id,
                 offset: 0,
@@ -93,7 +93,7 @@ impl<'tcx> Memory<'tcx> {
         debug!("creating fn ptr: {}", id);
         self.next_id.0 += 1;
         self.functions.insert(id, def);
-        self.function_definitions.insert(def, id);
+        self.function_alloc_cache.insert(def, id);
         Pointer {
             alloc_id: id,
             offset: 0,

From 0821a15476ad85975445fdfde3bb8016b8d8c848 Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 20 Jun 2016 16:57:36 +0200
Subject: [PATCH 13/18] no need for EvalContext::eval_binop

---
 src/interpreter/mod.rs | 25 +++++++------------------
 1 file changed, 7 insertions(+), 18 deletions(-)

diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index 4815421f24..0a8c82c5df 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -688,14 +688,15 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
         self.memory.write_bool(dest.offset(offset), overflowed)
     }
 
-    /// Extracts the lhs and rhs primval from the operands and applies the binary op.
-    /// Returns the result and whether the operation overflowed
-    fn eval_binop(
+    /// Applies the binary operation `op` to the arguments and writes the result to the destination.
+    /// Returns `true` if the operation overflowed.
+    fn intrinsic_overflowing(
         &mut self,
         op: mir::BinOp,
         left: &mir::Operand<'tcx>,
         right: &mir::Operand<'tcx>,
-    ) -> EvalResult<'tcx, (PrimVal, bool)> {
+        dest: Pointer,
+    ) -> EvalResult<'tcx, bool> {
         let left_ptr = self.eval_operand(left)?;
         let left_ty = self.operand_ty(left);
         let left_val = self.read_primval(left_ptr, left_ty)?;
@@ -704,18 +705,7 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
         let right_ty = self.operand_ty(right);
         let right_val = self.read_primval(right_ptr, right_ty)?;
 
-        primval::binary_op(op, left_val, right_val)
-    }
-
-    /// applies the binary operation `op` to the arguments and writes the result to the destination
-    fn intrinsic_overflowing(
-        &mut self,
-        op: mir::BinOp,
-        left: &mir::Operand<'tcx>,
-        right: &mir::Operand<'tcx>,
-        dest: Pointer,
-    ) -> EvalResult<'tcx, bool> {
-        let (val, overflow) = self.eval_binop(op, left, right)?;
+        let (val, overflow) = primval::binary_op(op, left_val, right_val)?;
         self.memory.write_primval(dest, val)?;
         Ok(overflow)
     }
@@ -944,8 +934,7 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
 
             BinaryOp(bin_op, ref left, ref right) => {
                 // ignore overflow bit, rustc inserts check branches for us
-                let result = self.eval_binop(bin_op, left, right)?.0;
-                self.memory.write_primval(dest, result)?;
+                self.intrinsic_overflowing(bin_op, left, right, dest)?;
             }
 
             CheckedBinaryOp(bin_op, ref left, ref right) => {

From 3e3aeab0ed29e7da7aa151465d5ed63d6689069b Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 20 Jun 2016 17:16:45 +0200
Subject: [PATCH 14/18] implement bit masks as the compiler would translate
 them

---
 src/error.rs   |  2 +-
 src/primval.rs | 27 +++++++++++++++++++--------
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/src/error.rs b/src/error.rs
index 3962c09dee..9e5e899746 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -69,7 +69,7 @@ impl<'tcx> Error for EvalError<'tcx> {
             EvalError::Math(..) =>
                 "mathematical operation failed",
             EvalError::InvalidBitShiftRhs(..) =>
-                "bit shift rhs negative or not an int",
+                "bit shift rhs not an int",
         }
     }
 
diff --git a/src/primval.rs b/src/primval.rs
index 673aea4244..586aaeee4e 100644
--- a/src/primval.rs
+++ b/src/primval.rs
@@ -69,15 +69,26 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
     match bin_op {
         // can have rhs with a different numeric type
         Shl | Shr => {
+            let mask_bits = match left {
+                I8(_) => 3,
+                I16(_) => 4,
+                I32(_) => 5,
+                I64(_) => 6,
+                U8(_) => 3,
+                U16(_) => 4,
+                U32(_) => 5,
+                U64(_) => 6,
+                _ => unreachable!(),
+            };
             let r = match right {
-                I8(i) if i >= 0 => i as u32,
-                I16(i) if i >= 0 => i as u32,
-                I32(i) if i >= 0 => i as u32,
-                I64(i) if i >= 0 && i as i32 as i64 == i => i as u32,
-                U8(i) => i as u32,
-                U16(i) => i as u32,
-                U32(i) => i,
-                U64(i) if i as u32 as u64 == i => i as u32,
+                I8(i) => (i & ((1 << mask_bits) - 1)) as u32,
+                I16(i) => (i & ((1 << mask_bits) - 1)) as u32,
+                I32(i) => (i & ((1 << mask_bits) - 1)) as u32,
+                I64(i) => (i & ((1 << mask_bits) - 1)) as u32,
+                U8(i) => (i & ((1 << mask_bits) - 1)) as u32,
+                U16(i) => (i & ((1 << mask_bits) - 1)) as u32,
+                U32(i) => (i & ((1 << mask_bits) - 1)) as u32,
+                U64(i) => (i & ((1 << mask_bits) - 1)) as u32,
                 _ => return Err(EvalError::InvalidBitShiftRhs(right)),
             };
             macro_rules! shift {

From a088f105aa2e099ba027e47f9bc29c30b06b416e Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 20 Jun 2016 17:52:14 +0200
Subject: [PATCH 15/18] add a comment explaining the magic numbers

---
 src/primval.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/primval.rs b/src/primval.rs
index 586aaeee4e..29d79abbbf 100644
--- a/src/primval.rs
+++ b/src/primval.rs
@@ -69,6 +69,8 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
     match bin_op {
         // can have rhs with a different numeric type
         Shl | Shr => {
+            // these numbers are the maximum number of bits a bitshift rhs could possibly have
+            // e.g. u16 can be bitshifted by 0..16, so 2^4 - 1 is the largest possible bitshift
             let mask_bits = match left {
                 I8(_) => 3,
                 I16(_) => 4,

From 001ae69212a58766c007bf8464927e18fe406d0f Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 20 Jun 2016 17:52:36 +0200
Subject: [PATCH 16/18] remove the bad rhs value error and panic instead. the
 typechecker prevent this

---
 src/error.rs   | 4 ----
 src/primval.rs | 2 +-
 2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/src/error.rs b/src/error.rs
index 9e5e899746..b19f63231a 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -5,7 +5,6 @@ use rustc::ty::BareFnTy;
 use memory::Pointer;
 use rustc_const_math::ConstMathErr;
 use syntax::codemap::Span;
-use primval::PrimVal;
 
 #[derive(Clone, Debug)]
 pub enum EvalError<'tcx> {
@@ -29,7 +28,6 @@ pub enum EvalError<'tcx> {
     ExecuteMemory,
     ArrayIndexOutOfBounds(Span, u64, u64),
     Math(Span, ConstMathErr),
-    InvalidBitShiftRhs(PrimVal),
 }
 
 pub type EvalResult<'tcx, T> = Result<T, EvalError<'tcx>>;
@@ -68,8 +66,6 @@ impl<'tcx> Error for EvalError<'tcx> {
                 "array index out of bounds",
             EvalError::Math(..) =>
                 "mathematical operation failed",
-            EvalError::InvalidBitShiftRhs(..) =>
-                "bit shift rhs not an int",
         }
     }
 
diff --git a/src/primval.rs b/src/primval.rs
index 29d79abbbf..fbb9301288 100644
--- a/src/primval.rs
+++ b/src/primval.rs
@@ -91,7 +91,7 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
                 U16(i) => (i & ((1 << mask_bits) - 1)) as u32,
                 U32(i) => (i & ((1 << mask_bits) - 1)) as u32,
                 U64(i) => (i & ((1 << mask_bits) - 1)) as u32,
-                _ => return Err(EvalError::InvalidBitShiftRhs(right)),
+                _ => panic!("bad MIR: bitshift rhs is not integral"),
             };
             macro_rules! shift {
                 ($v:ident, $l:ident, $r:ident) => ({

From c7039dbb2b601cff4a929e01c4941b00becadab2 Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 20 Jun 2016 18:01:35 +0200
Subject: [PATCH 17/18] simplify the masked rhs computation

---
 src/primval.rs | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/primval.rs b/src/primval.rs
index fbb9301288..3399d697ed 100644
--- a/src/primval.rs
+++ b/src/primval.rs
@@ -82,17 +82,19 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
                 U64(_) => 6,
                 _ => unreachable!(),
             };
+            let mask = (1 << mask_bits) - 1;
             let r = match right {
-                I8(i) => (i & ((1 << mask_bits) - 1)) as u32,
-                I16(i) => (i & ((1 << mask_bits) - 1)) as u32,
-                I32(i) => (i & ((1 << mask_bits) - 1)) as u32,
-                I64(i) => (i & ((1 << mask_bits) - 1)) as u32,
-                U8(i) => (i & ((1 << mask_bits) - 1)) as u32,
-                U16(i) => (i & ((1 << mask_bits) - 1)) as u32,
-                U32(i) => (i & ((1 << mask_bits) - 1)) as u32,
-                U64(i) => (i & ((1 << mask_bits) - 1)) as u32,
+                I8(i) => i as u8 & mask,
+                I16(i) => i as u8 & mask,
+                I32(i) => i as u8 & mask,
+                I64(i) => i as u8 & mask,
+                U8(i) => i as u8 & mask,
+                U16(i) => i as u8 & mask,
+                U32(i) => i as u8 & mask,
+                U64(i) => i as u8 & mask,
                 _ => panic!("bad MIR: bitshift rhs is not integral"),
             };
+            let r = r as u32;
             macro_rules! shift {
                 ($v:ident, $l:ident, $r:ident) => ({
                     match bin_op {

From 65de5dd2d0fd66c5277787558c3af9421545af24 Mon Sep 17 00:00:00 2001
From: Oliver Schneider <git-spam-no-reply9815368754983@oli-obk.de>
Date: Mon, 20 Jun 2016 18:15:33 +0200
Subject: [PATCH 18/18] simplify even more

---
 src/primval.rs | 40 +++++++++++++++++++---------------------
 1 file changed, 19 insertions(+), 21 deletions(-)

diff --git a/src/primval.rs b/src/primval.rs
index 3399d697ed..6b17a63b65 100644
--- a/src/primval.rs
+++ b/src/primval.rs
@@ -69,32 +69,30 @@ pub fn binary_op<'tcx>(bin_op: mir::BinOp, left: PrimVal, right: PrimVal) -> Eva
     match bin_op {
         // can have rhs with a different numeric type
         Shl | Shr => {
-            // these numbers are the maximum number of bits a bitshift rhs could possibly have
-            // e.g. u16 can be bitshifted by 0..16, so 2^4 - 1 is the largest possible bitshift
-            let mask_bits = match left {
-                I8(_) => 3,
-                I16(_) => 4,
-                I32(_) => 5,
-                I64(_) => 6,
-                U8(_) => 3,
-                U16(_) => 4,
-                U32(_) => 5,
-                U64(_) => 6,
+            // these numbers are the maximum number a bitshift rhs could possibly have
+            // e.g. u16 can be bitshifted by 0..16, so masking with 0b1111 (16 - 1) will ensure we are in that range
+            let type_bits: u32 = match left {
+                I8(_) | U8(_) => 8,
+                I16(_) | U16(_) => 16,
+                I32(_) | U32(_) => 32,
+                I64(_) | U64(_) => 64,
                 _ => unreachable!(),
             };
-            let mask = (1 << mask_bits) - 1;
+            assert!(type_bits.is_power_of_two());
+            // turn into `u32` because `overflowing_sh{l,r}` only take `u32`
             let r = match right {
-                I8(i) => i as u8 & mask,
-                I16(i) => i as u8 & mask,
-                I32(i) => i as u8 & mask,
-                I64(i) => i as u8 & mask,
-                U8(i) => i as u8 & mask,
-                U16(i) => i as u8 & mask,
-                U32(i) => i as u8 & mask,
-                U64(i) => i as u8 & mask,
+                I8(i) => i as u32,
+                I16(i) => i as u32,
+                I32(i) => i as u32,
+                I64(i) => i as u32,
+                U8(i) => i as u32,
+                U16(i) => i as u32,
+                U32(i) => i as u32,
+                U64(i) => i as u32,
                 _ => panic!("bad MIR: bitshift rhs is not integral"),
             };
-            let r = r as u32;
+            // apply mask
+            let r = r & (type_bits - 1);
             macro_rules! shift {
                 ($v:ident, $l:ident, $r:ident) => ({
                     match bin_op {