Only SwitchInt over integers, not all consts

Also use a Cow to avoid full Vec for all SwitchInts

10 files changed, 154 insertions, 101 deletions

diff --git a/src/librustc/middle/const_val.rs b/src/librustc/middle/const_val.rs
index c4e3827fef2..f885a6d9569 100644
--- a/src/librustc/middle/const_val.rs
+++ b/src/librustc/middle/const_val.rs
@@ -11,6 +11,7 @@
 use syntax::symbol::InternedString;
 use syntax::ast;
 use std::rc::Rc;
+use std::borrow::Cow;
 use hir::def_id::DefId;
 use rustc_const_math::*;
 use self::ConstVal::*;
@@ -18,6 +19,8 @@ pub use rustc_const_math::ConstInt;
 
 use std::collections::BTreeMap;
 
+pub static BOOL_SWITCH_TRUE: Cow<'static, [ConstInt]> = Cow::Borrowed(&[ConstInt::Infer(1)]);
+
 #[derive(Clone, Debug, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq)]
 pub enum ConstVal {
     Float(ConstFloat),
@@ -49,4 +52,14 @@ impl ConstVal {
             Char(..) => "char",
         }
     }
+
+    pub fn to_const_int(&self) -> Option<ConstInt> {
+        match *self {
+            ConstVal::Integral(i) => Some(i),
+            ConstVal::Bool(true) => Some(ConstInt::Infer(1)),
+            ConstVal::Bool(false) => Some(ConstInt::Infer(0)),
+            ConstVal::Char(ch) => Some(ConstInt::U32(ch as u32)),
+            _ => None
+        }
+    }
 }
diff --git a/src/librustc/mir/mod.rs b/src/librustc/mir/mod.rs
index b0a6784c3c3..28990fd323f 100644
--- a/src/librustc/mir/mod.rs
+++ b/src/librustc/mir/mod.rs
@@ -446,6 +446,9 @@ pub struct Terminator<'tcx> {
     pub kind: TerminatorKind<'tcx>
 }
 
+/// For use in SwitchInt, for switching on bools.
+pub static BOOL_SWITCH_TRUE: Cow<'static, [ConstInt]> = Cow::Borrowed(&[ConstInt::Infer(1)]);
+
 #[derive(Clone, RustcEncodable, RustcDecodable)]
 pub enum TerminatorKind<'tcx> {
     /// block should have one successor in the graph; we jump there
@@ -464,8 +467,7 @@ pub enum TerminatorKind<'tcx> {
 
         /// Possible values. The locations to branch to in each case
         /// are found in the corresponding indices from the `targets` vector.
-        // FIXME: ConstVal doesn’t quite make any sense here? Its a Switch*Int*.
-        values: Vec<ConstVal>,
+        values: Cow<'tcx, [ConstInt]>,
 
         /// Possible branch sites. The length of this vector should be
         /// equal to the length of the `values` vector plus 1 -- the
@@ -696,7 +698,7 @@ impl<'tcx> TerminatorKind<'tcx> {
                 values.iter()
                       .map(|const_val| {
                           let mut buf = String::new();
-                          fmt_const_val(&mut buf, const_val).unwrap();
+                          fmt_const_val(&mut buf, &ConstVal::Integral(*const_val)).unwrap();
                           buf.into()
                       })
                       .chain(iter::once(String::from("otherwise").into()))
diff --git a/src/librustc/mir/visit.rs b/src/librustc/mir/visit.rs
index ca20cf6236b..be3c43db7ba 100644
--- a/src/librustc/mir/visit.rs
+++ b/src/librustc/mir/visit.rs
@@ -223,6 +223,12 @@ macro_rules! make_mir_visitor {
                 self.super_const_val(const_val);
             }
 
+            fn visit_const_int(&mut self,
+                               const_int: &ConstInt,
+                               _: Location) {
+                self.super_const_int(const_int);
+            }
+
             fn visit_const_usize(&mut self,
                                  const_usize: & $($mutability)* ConstUsize,
                                  _: Location) {
@@ -364,12 +370,12 @@ macro_rules! make_mir_visitor {
 
                     TerminatorKind::SwitchInt { ref $($mutability)* discr,
                                                 ref $($mutability)* switch_ty,
-                                                ref $($mutability)* values,
+                                                ref values,
                                                 ref targets } => {
                         self.visit_operand(discr, source_location);
                         self.visit_ty(switch_ty);
-                        for value in values {
-                            self.visit_const_val(value, source_location);
+                        for value in &values[..] {
+                            self.visit_const_int(value, source_location);
                         }
                         for &target in targets {
                             self.visit_branch(block, target);
@@ -698,10 +704,13 @@ macro_rules! make_mir_visitor {
                                     _substs: & $($mutability)* ClosureSubsts<'tcx>) {
             }
 
-            fn super_const_val(&mut self, _substs: & $($mutability)* ConstVal) {
+            fn super_const_val(&mut self, _const_val: & $($mutability)* ConstVal) {
+            }
+
+            fn super_const_int(&mut self, _const_int: &ConstInt) {
             }
 
-            fn super_const_usize(&mut self, _substs: & $($mutability)* ConstUsize) {
+            fn super_const_usize(&mut self, _const_usize: & $($mutability)* ConstUsize) {
             }
 
             // Convenience methods
diff --git a/src/librustc_borrowck/borrowck/mir/elaborate_drops.rs b/src/librustc_borrowck/borrowck/mir/elaborate_drops.rs
index 8f3dcd0b8d6..53e84f1fb71 100644
--- a/src/librustc_borrowck/borrowck/mir/elaborate_drops.rs
+++ b/src/librustc_borrowck/borrowck/mir/elaborate_drops.rs
@@ -679,7 +679,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
                     let discr = ConstInt::new_inttype(variant.disr_val, adt.discr_ty,
                                                       self.tcx.sess.target.uint_type,
                                                       self.tcx.sess.target.int_type).unwrap();
-                    values.push(ConstVal::Integral(discr));
+                    values.push(discr);
                     blocks.push(self.open_drop_for_variant(c, &mut drop_block, adt, substs, idx));
                 }
                 // If there are multiple variants, then if something
@@ -704,7 +704,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
                         kind: TerminatorKind::SwitchInt {
                             discr: Operand::Consume(discr),
                             switch_ty: discr_ty,
-                            values: values,
+                            values: From::from(values),
                             targets: blocks,
                             // adt_def: adt,
                             // targets: variant_drops
@@ -836,7 +836,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
                 self.new_block(c, is_cleanup, TerminatorKind::SwitchInt {
                     discr: Operand::Consume(flag),
                     switch_ty: boolty,
-                    values: vec![ConstVal::Bool(true)],
+                    values: BOOL_SWITCH_TRUE.clone(),
                     targets: vec![on_set, on_unset],
                 })
             }
diff --git a/src/librustc_mir/build/expr/into.rs b/src/librustc_mir/build/expr/into.rs
index 2b4336ba66f..537daa4a15b 100644
--- a/src/librustc_mir/build/expr/into.rs
+++ b/src/librustc_mir/build/expr/into.rs
@@ -15,7 +15,6 @@ use build::expr::category::{Category, RvalueFunc};
 use hair::*;
 use rustc::ty;
 use rustc::mir::*;
-use rustc::middle::const_val::ConstVal;
 
 impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     /// Compile `expr`, storing the result into `destination`, which
@@ -73,7 +72,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 this.cfg.terminate(block, source_info, TerminatorKind::SwitchInt {
                     discr: operand,
                     switch_ty: this.hir.bool_ty(),
-                    values: vec![ConstVal::Bool(true)],
+                    values: BOOL_SWITCH_TRUE.clone(),
                     targets: vec![then_block, else_block],
                 });
 
@@ -120,7 +119,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 this.cfg.terminate(block, source_info, TerminatorKind::SwitchInt {
                     discr: lhs,
                     switch_ty: this.hir.bool_ty(),
-                    values: vec![ConstVal::Bool(true)],
+                    values: BOOL_SWITCH_TRUE.clone(),
                     targets: blocks,
                 });
 
@@ -128,7 +127,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 this.cfg.terminate(else_block, source_info, TerminatorKind::SwitchInt {
                     discr: rhs,
                     switch_ty: this.hir.bool_ty(),
-                    values: vec![ConstVal::Bool(true)],
+                    values: BOOL_SWITCH_TRUE.clone(),
                     targets: vec![true_block, false_block],
                 });
 
@@ -192,7 +191,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                                                TerminatorKind::SwitchInt {
                                                    discr: cond,
                                                    switch_ty: this.hir.bool_ty(),
-                                                   values: vec![ConstVal::Bool(true)],
+                                                   values: BOOL_SWITCH_TRUE.clone(),
                                                    targets: vec![body_block, exit_block],
                                                });
 
diff --git a/src/librustc_mir/build/matches/mod.rs b/src/librustc_mir/build/matches/mod.rs
index 0898d06d2e4..885965da1f9 100644
--- a/src/librustc_mir/build/matches/mod.rs
+++ b/src/librustc_mir/build/matches/mod.rs
@@ -675,7 +675,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             self.cfg.terminate(block, source_info, TerminatorKind::SwitchInt {
                 discr: cond,
                 switch_ty: self.hir.bool_ty(),
-                values: vec![ConstVal::Bool(true)],
+                values: BOOL_SWITCH_TRUE.clone(),
                 targets: vec![arm_block, otherwise],
             });
             Some(otherwise)
diff --git a/src/librustc_mir/build/matches/test.rs b/src/librustc_mir/build/matches/test.rs
index 528e37e73c4..f2d48f65fef 100644
--- a/src/librustc_mir/build/matches/test.rs
+++ b/src/librustc_mir/build/matches/test.rs
@@ -196,7 +196,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                         let discr = ConstInt::new_inttype(variant.disr_val, adt_def.discr_ty,
                                                           tcx.sess.target.uint_type,
                                                           tcx.sess.target.int_type).unwrap();
-                        values.push(ConstVal::Integral(discr));
+                        values.push(discr);
                         *(targets.place_back() <- self.cfg.start_new_block())
                     } else {
                         if otherwise_block.is_none() {
@@ -226,59 +226,45 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 self.cfg.terminate(block, source_info, TerminatorKind::SwitchInt {
                     discr: Operand::Consume(discr),
                     switch_ty: discr_ty,
-                    values: values,
+                    values: From::from(values),
                     targets: targets
                 });
                 target_blocks
             }
 
             TestKind::SwitchInt { switch_ty, ref options, indices: _ } => {
-                let (targets, term) = match switch_ty.sty {
-                    // If we're matching on boolean we can
-                    // use the If TerminatorKind instead
-                    ty::TyBool => {
-                        assert!(options.len() > 0 && options.len() <= 2);
-
-                        let (true_bb, else_bb) =
-                            (self.cfg.start_new_block(),
-                             self.cfg.start_new_block());
-
-                        let targets = match &options[0] {
-                            &ConstVal::Bool(true) => vec![true_bb, else_bb],
-                            &ConstVal::Bool(false) => vec![else_bb, true_bb],
-                            v => span_bug!(test.span, "expected boolean value but got {:?}", v)
-                        };
-
-                        (targets, TerminatorKind::SwitchInt {
-                             discr: Operand::Consume(lvalue.clone()),
-                             switch_ty: self.hir.bool_ty(),
-                             values: vec![ConstVal::Bool(true)],
-                             targets: vec![true_bb, else_bb]
-                         })
-
-                    }
-                    _ => {
-                        // The switch may be inexhaustive so we
-                        // add a catch all block
-                        let otherwise = self.cfg.start_new_block();
-                        let targets: Vec<_> =
-                            options.iter()
-                                   .map(|_| self.cfg.start_new_block())
-                                   .chain(Some(otherwise))
-                                   .collect();
-
-                        (targets.clone(),
-                         TerminatorKind::SwitchInt {
-                             discr: Operand::Consume(lvalue.clone()),
-                             switch_ty: switch_ty,
-                             values: options.clone(),
-                             targets: targets
-                         })
-                    }
+                let (values, targets, ret) = if switch_ty.sty == ty::TyBool {
+                    assert!(options.len() > 0 && options.len() <= 2);
+                    let (true_bb, false_bb) = (self.cfg.start_new_block(),
+                                               self.cfg.start_new_block());
+                    let ret = match &options[0] {
+                        &ConstVal::Bool(true) => vec![true_bb, false_bb],
+                        &ConstVal::Bool(false) => vec![false_bb, true_bb],
+                        v => span_bug!(test.span, "expected boolean value but got {:?}", v)
+                    };
+                    (BOOL_SWITCH_TRUE.clone(), vec![true_bb, false_bb], ret)
+                } else {
+                    // The switch may be inexhaustive so we
+                    // add a catch all block
+                    let otherwise = self.cfg.start_new_block();
+                    let targets: Vec<_> =
+                        options.iter()
+                               .map(|_| self.cfg.start_new_block())
+                               .chain(Some(otherwise))
+                               .collect();
+                    let values: Vec<_> = options.iter().map(|v|
+                        v.to_const_int().expect("switching on integral")
+                    ).collect();
+                    (From::from(values), targets.clone(), targets)
                 };
 
-                self.cfg.terminate(block, source_info, term);
-                targets
+                self.cfg.terminate(block, source_info, TerminatorKind::SwitchInt {
+                    discr: Operand::Consume(lvalue.clone()),
+                    switch_ty: switch_ty,
+                    values: values,
+                    targets: targets.clone(),
+                });
+                ret
             }
 
             TestKind::Eq { ref value, mut ty } => {
@@ -346,10 +332,9 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                     self.cfg.terminate(eq_block, source_info, TerminatorKind::SwitchInt {
                         discr: Operand::Consume(eq_result),
                         switch_ty: self.hir.bool_ty(),
-                        values: vec![ConstVal::Bool(true)],
+                        values: BOOL_SWITCH_TRUE.clone(),
                         targets: vec![block, fail],
                     });
-
                     vec![block, fail]
                 } else {
                     let block = self.compare(block, fail, test.span, BinOp::Eq, expect, val);
@@ -391,16 +376,15 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                                                       Operand::Consume(expected)));
 
                 // branch based on result
-                let target_blocks: Vec<_> = vec![self.cfg.start_new_block(),
-                                                 self.cfg.start_new_block()];
+                let (false_bb, true_bb) = (self.cfg.start_new_block(),
+                                           self.cfg.start_new_block());
                 self.cfg.terminate(block, source_info, TerminatorKind::SwitchInt {
                     discr: Operand::Consume(result),
                     switch_ty: self.hir.bool_ty(),
-                    values: vec![ConstVal::Bool(true)],
-                    targets: target_blocks.clone(),
+                    values: BOOL_SWITCH_TRUE.clone(),
+                    targets: vec![true_bb, false_bb],
                 });
-
-                target_blocks
+                vec![true_bb, false_bb]
             }
         }
     }
@@ -425,10 +409,9 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         self.cfg.terminate(block, source_info, TerminatorKind::SwitchInt {
             discr: Operand::Consume(result),
             switch_ty: self.hir.bool_ty(),
-            values: vec![ConstVal::Bool(true)],
+            values: BOOL_SWITCH_TRUE.clone(),
             targets: vec![target_block, fail_block]
         });
-
         target_block
     }
 
diff --git a/src/librustc_trans/mir/block.rs b/src/librustc_trans/mir/block.rs
index 2ed2cc61062..651d0066b12 100644
--- a/src/librustc_trans/mir/block.rs
+++ b/src/librustc_trans/mir/block.rs
@@ -11,6 +11,7 @@
 use llvm::{self, ValueRef, BasicBlockRef};
 use rustc_const_eval::{ErrKind, ConstEvalErr, note_const_eval_err};
 use rustc::middle::lang_items;
+use rustc::middle::const_val::ConstInt;
 use rustc::ty::{self, layout, TypeFoldable};
 use rustc::mir;
 use abi::{Abi, FnType, ArgType};
@@ -134,14 +135,24 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
             }
 
             mir::TerminatorKind::SwitchInt { ref discr, switch_ty, ref values, ref targets } => {
-                // TODO: cond_br if only 1 value
-                let (otherwise, targets) = targets.split_last().unwrap();
-                let discr = self.trans_operand(&bcx, discr).immediate();
-                let switch = bcx.switch(discr, llblock(self, *otherwise), values.len());
-                for (value, target) in values.iter().zip(targets) {
-                    let val = Const::from_constval(bcx.ccx, value.clone(), switch_ty);
-                    let llbb = llblock(self, *target);
-                    bcx.add_case(switch, val.llval, llbb)
+                let discr = self.trans_operand(&bcx, discr);
+                if switch_ty == bcx.tcx().types.bool {
+                    let lltrue = llblock(self, targets[0]);
+                    let llfalse = llblock(self, targets[1]);
+                    if let [ConstInt::Infer(0)] = values[..] {
+                        bcx.cond_br(discr.immediate(), llfalse, lltrue);
+                    } else {
+                        bcx.cond_br(discr.immediate(), lltrue, llfalse);
+                    }
+                } else {
+                    let (otherwise, targets) = targets.split_last().unwrap();
+                    let switch = bcx.switch(discr.immediate(),
+                                            llblock(self, *otherwise), values.len());
+                    for (value, target) in values.iter().zip(targets) {
+                        let val = Const::from_constint(bcx.ccx, value);
+                        let llbb = llblock(self, *target);
+                        bcx.add_case(switch, val.llval, llbb)
+                    }
                 }
             }
 
diff --git a/src/librustc_trans/mir/constant.rs b/src/librustc_trans/mir/constant.rs
index 11668e792e3..19139301bb0 100644
--- a/src/librustc_trans/mir/constant.rs
+++ b/src/librustc_trans/mir/constant.rs
@@ -61,6 +61,33 @@ impl<'tcx> Const<'tcx> {
         }
     }
 
+    pub fn from_constint<'a>(ccx: &CrateContext<'a, 'tcx>, ci: &ConstInt)
+    -> Const<'tcx> {
+        let tcx = ccx.tcx();
+        let (llval, ty) = match *ci {
+            I8(v) => (C_integral(Type::i8(ccx), v as u64, true), tcx.types.i8),
+            I16(v) => (C_integral(Type::i16(ccx), v as u64, true), tcx.types.i16),
+            I32(v) => (C_integral(Type::i32(ccx), v as u64, true), tcx.types.i32),
+            I64(v) => (C_integral(Type::i64(ccx), v as u64, true), tcx.types.i64),
+            I128(v) => (C_big_integral(Type::i128(ccx), v as u128), tcx.types.i128),
+            Isize(v) => {
+                let i = v.as_i64(ccx.tcx().sess.target.int_type);
+                (C_integral(Type::int(ccx), i as u64, true), tcx.types.isize)
+            },
+            U8(v) => (C_integral(Type::i8(ccx), v as u64, false), tcx.types.u8),
+            U16(v) => (C_integral(Type::i16(ccx), v as u64, false), tcx.types.u16),
+            U32(v) => (C_integral(Type::i32(ccx), v as u64, false), tcx.types.u32),
+            U64(v) => (C_integral(Type::i64(ccx), v, false), tcx.types.u64),
+            U128(v) => (C_big_integral(Type::i128(ccx), v), tcx.types.u128),
+            Usize(v) => {
+                let u = v.as_u64(ccx.tcx().sess.target.uint_type);
+                (C_integral(Type::int(ccx), u, false), tcx.types.usize)
+            },
+            Infer(_) | InferSigned(_) => bug!("MIR must not use `{:?}`", ci),
+        };
+        Const { llval: llval, ty: ty }
+    }
+
     /// Translate ConstVal into a LLVM constant value.
     pub fn from_constval<'a>(ccx: &CrateContext<'a, 'tcx>,
                              cv: ConstVal,
@@ -72,26 +99,7 @@ impl<'tcx> Const<'tcx> {
             ConstVal::Float(F64(v)) => C_floating_f64(v, llty),
             ConstVal::Float(FInfer {..}) => bug!("MIR must not use `{:?}`", cv),
             ConstVal::Bool(v) => C_bool(ccx, v),
-            ConstVal::Integral(I8(v)) => C_integral(Type::i8(ccx), v as u64, true),
-            ConstVal::Integral(I16(v)) => C_integral(Type::i16(ccx), v as u64, true),
-            ConstVal::Integral(I32(v)) => C_integral(Type::i32(ccx), v as u64, true),
-            ConstVal::Integral(I64(v)) => C_integral(Type::i64(ccx), v as u64, true),
-            ConstVal::Integral(I128(v)) => C_big_integral(Type::i128(ccx), v as u128),
-            ConstVal::Integral(Isize(v)) => {
-                let i = v.as_i64(ccx.tcx().sess.target.int_type);
-                C_integral(Type::int(ccx), i as u64, true)
-            },
-            ConstVal::Integral(U8(v)) => C_integral(Type::i8(ccx), v as u64, false),
-            ConstVal::Integral(U16(v)) => C_integral(Type::i16(ccx), v as u64, false),
-            ConstVal::Integral(U32(v)) => C_integral(Type::i32(ccx), v as u64, false),
-            ConstVal::Integral(U64(v)) => C_integral(Type::i64(ccx), v, false),
-            ConstVal::Integral(U128(v)) => C_big_integral(Type::i128(ccx), v),
-            ConstVal::Integral(Usize(v)) => {
-                let u = v.as_u64(ccx.tcx().sess.target.uint_type);
-                C_integral(Type::int(ccx), u, false)
-            },
-            ConstVal::Integral(Infer(_)) |
-            ConstVal::Integral(InferSigned(_)) => bug!("MIR must not use `{:?}`", cv),
+            ConstVal::Integral(ref i) => return Const::from_constint(ccx, i),
             ConstVal::Str(ref v) => C_str_slice(ccx, v.clone()),
             ConstVal::ByteStr(ref v) => consts::addr_of(ccx, C_bytes(ccx, v), 1, "byte_str"),
             ConstVal::Struct(_) | ConstVal::Tuple(_) |
diff --git a/src/libserialize/serialize.rs b/src/libserialize/serialize.rs
index ba39fcdec6f..c6847249803 100644
--- a/src/libserialize/serialize.rs
+++ b/src/libserialize/serialize.rs
@@ -567,6 +567,34 @@ impl<T:Decodable> Decodable for Vec<T> {
     }
 }
 
+impl<'a, T:Encodable> Encodable for Cow<'a, [T]>
+where [T]: ToOwned<Owned = Vec<T>>
+{
+    fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
+        s.emit_seq(self.len(), |s| {
+            for (i, e) in self.iter().enumerate() {
+                s.emit_seq_elt(i, |s| e.encode(s))?
+            }
+            Ok(())
+        })
+    }
+}
+
+impl<T:Decodable+ToOwned> Decodable for Cow<'static, [T]>
+where [T]: ToOwned<Owned = Vec<T>>
+{
+    fn decode<D: Decoder>(d: &mut D) -> Result<Cow<'static, [T]>, D::Error> {
+        d.read_seq(|d, len| {
+            let mut v = Vec::with_capacity(len);
+            for i in 0..len {
+                v.push(d.read_seq_elt(i, |d| Decodable::decode(d))?);
+            }
+            Ok(Cow::Owned(v))
+        })
+    }
+}
+
+
 impl<T:Encodable> Encodable for Option<T> {
     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
         s.emit_option(|s| {