Add TerminatorKind::if_ convenience constructor

Constructs a TerminatorKind::SwitchInt for an equivalent conditional true-false branch.

src/librustc/mir/mod.rs

@@ -446,9 +446,6 @@ pub struct Terminator<'tcx> {
     pub kind: TerminatorKind<'tcx>
 }
 
-/// For use in SwitchInt, for switching on bools.
-pub static BOOL_SWITCH_FALSE: Cow<'static, [ConstInt]> = Cow::Borrowed(&[ConstInt::Infer(0)]);
-
 #[derive(Clone, RustcEncodable, RustcDecodable)]
 pub enum TerminatorKind<'tcx> {
     /// block should have one successor in the graph; we jump there
@@ -543,6 +540,17 @@ pub fn successors_mut(&mut self) -> Vec<&mut BasicBlock> {
 }
 
 impl<'tcx> TerminatorKind<'tcx> {
+    pub fn if_<'a, 'gcx>(tcx: ty::TyCtxt<'a, 'gcx, 'tcx>, cond: Operand<'tcx>,
+                         t: BasicBlock, f: BasicBlock) -> TerminatorKind<'tcx> {
+        static BOOL_SWITCH_FALSE: &'static [ConstInt] = &[ConstInt::Infer(0)];
+        TerminatorKind::SwitchInt {
+            discr: cond,
+            switch_ty: tcx.types.bool,
+            values: From::from(BOOL_SWITCH_FALSE),
+            targets: vec![f, t],
+        }
+    }
+
     pub fn successors(&self) -> Cow<[BasicBlock]> {
         use self::TerminatorKind::*;
         match *self {

src/librustc_borrowck/borrowck/mir/elaborate_drops.rs

@@ -842,13 +842,8 @@ fn drop_flag_test_block_with_succ<'a>(&mut self,
             (true, false) => on_set,
             (true, true) => {
                 let flag = self.drop_flag(c.path).unwrap();
-                let boolty = self.tcx.types.bool;
-                self.new_block(c, is_cleanup, TerminatorKind::SwitchInt {
-                    discr: Operand::Consume(flag),
-                    switch_ty: boolty,
-                    values: BOOL_SWITCH_FALSE.clone(),
-                    targets: vec![on_unset, on_set],
-                })
+                let term = TerminatorKind::if_(self.tcx, Operand::Consume(flag), on_set, on_unset);
+                self.new_block(c, is_cleanup, term)
             }
         }
     }

src/librustc_mir/build/expr/into.rs

@@ -69,12 +69,8 @@ pub fn into_expr(&mut self,
 
                 let mut then_block = this.cfg.start_new_block();
                 let mut else_block = this.cfg.start_new_block();
-                this.cfg.terminate(block, source_info, TerminatorKind::SwitchInt {
-                    discr: operand,
-                    switch_ty: this.hir.bool_ty(),
-                    values: BOOL_SWITCH_FALSE.clone(),
-                    targets: vec![else_block, then_block],
-                });
+                let term = TerminatorKind::if_(this.hir.tcx(), operand, then_block, else_block);
+                this.cfg.terminate(block, source_info, term);
 
                 unpack!(then_block = this.into(destination, then_block, then_expr));
                 else_block = if let Some(else_expr) = else_expr {
@@ -113,23 +109,15 @@ pub fn into_expr(&mut self,
 
                 let lhs = unpack!(block = this.as_operand(block, lhs));
                 let blocks = match op {
-                    LogicalOp::And => vec![false_block, else_block],
-                    LogicalOp::Or => vec![else_block, true_block],
+                    LogicalOp::And => (else_block, false_block),
+                    LogicalOp::Or => (true_block, else_block),
                 };
-                this.cfg.terminate(block, source_info, TerminatorKind::SwitchInt {
-                    discr: lhs,
-                    switch_ty: this.hir.bool_ty(),
-                    values: BOOL_SWITCH_FALSE.clone(),
-                    targets: blocks,
-                });
+                let term = TerminatorKind::if_(this.hir.tcx(), lhs, blocks.0, blocks.1);
+                this.cfg.terminate(block, source_info, term);
 
                 let rhs = unpack!(else_block = this.as_operand(else_block, rhs));
-                this.cfg.terminate(else_block, source_info, TerminatorKind::SwitchInt {
-                    discr: rhs,
-                    switch_ty: this.hir.bool_ty(),
-                    values: BOOL_SWITCH_FALSE.clone(),
-                    targets: vec![false_block, true_block],
-                });
+                let term = TerminatorKind::if_(this.hir.tcx(), rhs, true_block, false_block);
+                this.cfg.terminate(else_block, source_info, term);
 
                 this.cfg.push_assign_constant(
                     true_block, source_info, destination,
@@ -187,13 +175,9 @@ pub fn into_expr(&mut self,
                             let cond = unpack!(
                                 loop_block_end = this.as_operand(loop_block, cond_expr));
                             body_block = this.cfg.start_new_block();
-                            this.cfg.terminate(loop_block_end, source_info,
-                                               TerminatorKind::SwitchInt {
-                                                   discr: cond,
-                                                   switch_ty: this.hir.bool_ty(),
-                                                   values: BOOL_SWITCH_FALSE.clone(),
-                                                   targets: vec![exit_block, body_block],
-                                               });
+                            let term = TerminatorKind::if_(this.hir.tcx(), cond,
+                                                           body_block, exit_block);
+                            this.cfg.terminate(loop_block_end, source_info, term);
 
                             // if the test is false, there's no `break` to assign `destination`, so
                             // we have to do it; this overwrites any `break`-assigned value but it's

src/librustc_mir/build/matches/mod.rs

@@ -672,12 +672,8 @@ fn bind_and_guard_matched_candidate<'pat>(&mut self,
             let source_info = self.source_info(guard.span);
             let cond = unpack!(block = self.as_operand(block, guard));
             let otherwise = self.cfg.start_new_block();
-            self.cfg.terminate(block, source_info, TerminatorKind::SwitchInt {
-                discr: cond,
-                switch_ty: self.hir.bool_ty(),
-                values: BOOL_SWITCH_FALSE.clone(),
-                targets: vec![otherwise, arm_block],
-            });
+            self.cfg.terminate(block, source_info,
+                               TerminatorKind::if_(self.hir.tcx(), cond, arm_block, otherwise));
             Some(otherwise)
         } else {
             let source_info = self.source_info(candidate.span);

src/librustc_mir/build/matches/test.rs

@@ -228,6 +228,7 @@ pub fn perform_test(&mut self,
 
             TestKind::SwitchInt { switch_ty, ref options, indices: _ } => {
                 let (values, targets, ret) = if switch_ty.sty == ty::TyBool {
+                    static BOOL_SWITCH_FALSE: &'static [ConstInt] = &[ConstInt::Infer(0)];
                     assert!(options.len() > 0 && options.len() <= 2);
                     let (true_bb, false_bb) = (self.cfg.start_new_block(),
                                                self.cfg.start_new_block());
@@ -236,7 +237,7 @@ pub fn perform_test(&mut self,
                         &ConstVal::Bool(false) => vec![false_bb, true_bb],
                         v => span_bug!(test.span, "expected boolean value but got {:?}", v)
                     };
-                    (BOOL_SWITCH_FALSE.clone(), vec![false_bb, true_bb], ret)
+                    (From::from(BOOL_SWITCH_FALSE), vec![false_bb, true_bb], ret)
                 } else {
                     // The switch may be inexhaustive so we
                     // add a catch all block
@@ -323,12 +324,10 @@ pub fn perform_test(&mut self,
 
                     // check the result
                     let block = self.cfg.start_new_block();
-                    self.cfg.terminate(eq_block, source_info, TerminatorKind::SwitchInt {
-                        discr: Operand::Consume(eq_result),
-                        switch_ty: self.hir.bool_ty(),
-                        values: BOOL_SWITCH_FALSE.clone(),
-                        targets: vec![fail, block],
-                    });
+                    self.cfg.terminate(eq_block, source_info,
+                                       TerminatorKind::if_(self.hir.tcx(),
+                                                           Operand::Consume(eq_result),
+                                                           block, fail));
                     vec![block, fail]
                 } else {
                     let block = self.compare(block, fail, test.span, BinOp::Eq, expect, val);
@@ -372,12 +371,9 @@ pub fn perform_test(&mut self,
                 // branch based on result
                 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: BOOL_SWITCH_FALSE.clone(),
-                    targets: vec![false_bb, true_bb],
-                });
+                self.cfg.terminate(block, source_info,
+                                   TerminatorKind::if_(self.hir.tcx(), Operand::Consume(result),
+                                                       true_bb, false_bb));
                 vec![true_bb, false_bb]
             }
         }
@@ -400,12 +396,9 @@ fn compare(&mut self,
 
         // branch based on result
         let target_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: BOOL_SWITCH_FALSE.clone(),
-            targets: vec![fail_block, target_block]
-        });
+        self.cfg.terminate(block, source_info,
+                           TerminatorKind::if_(self.hir.tcx(), Operand::Consume(result),
+                                               target_block, fail_block));
         target_block
     }