Couple mir building cleanups

compiler/rustc_mir_build/src/builder/expr/as_constant.rs

@@ -105,23 +105,19 @@ fn lit_to_mir_constant<'tcx>(tcx: TyCtxt<'tcx>, lit_input: LitToConstInput<'tcx>
         return Const::Ty(Ty::new_error(tcx, guar), ty::Const::new_error(tcx, guar));
     }
 
-    let trunc = |n, width: ty::UintTy| {
-        let width = width
-            .normalize(tcx.data_layout.pointer_size.bits().try_into().unwrap())
-            .bit_width()
-            .unwrap();
-        let width = Size::from_bits(width);
+    let lit_ty = match *ty.kind() {
+        ty::Pat(base, _) => base,
+        _ => ty,
+    };
+
+    let trunc = |n| {
+        let width = lit_ty.primitive_size(tcx);
         trace!("trunc {} with size {} and shift {}", n, width.bits(), 128 - width.bits());
         let result = width.truncate(n);
         trace!("trunc result: {}", result);
         ConstValue::Scalar(Scalar::from_uint(result, width))
     };
 
-    let lit_ty = match *ty.kind() {
-        ty::Pat(base, _) => base,
-        _ => ty,
-    };
-
     let value = match (lit, lit_ty.kind()) {
         (ast::LitKind::Str(s, _), ty::Ref(_, inner_ty, _)) if inner_ty.is_str() => {
             let s = s.as_str();
@@ -149,11 +145,10 @@ fn lit_to_mir_constant<'tcx>(tcx: TyCtxt<'tcx>, lit_input: LitToConstInput<'tcx>
         (ast::LitKind::Byte(n), ty::Uint(ty::UintTy::U8)) => {
             ConstValue::Scalar(Scalar::from_uint(*n, Size::from_bytes(1)))
         }
-        (ast::LitKind::Int(n, _), ty::Uint(ui)) if !neg => trunc(n.get(), *ui),
-        (ast::LitKind::Int(n, _), ty::Int(i)) => trunc(
-            if neg { (n.get() as i128).overflowing_neg().0 as u128 } else { n.get() },
-            i.to_unsigned(),
-        ),
+        (ast::LitKind::Int(n, _), ty::Uint(_)) if !neg => trunc(n.get()),
+        (ast::LitKind::Int(n, _), ty::Int(_)) => {
+            trunc(if neg { (n.get() as i128).overflowing_neg().0 as u128 } else { n.get() })
+        }
         (ast::LitKind::Float(n, _), ty::Float(fty)) => {
             parse_float_into_constval(*n, *fty, neg).unwrap()
         }

compiler/rustc_mir_build/src/builder/scope.rs

@@ -305,27 +305,25 @@ impl DropTree {
     }
 
     /// Builds the MIR for a given drop tree.
-    ///
-    /// `blocks` should have the same length as `self.drops`, and may have its
-    /// first value set to some already existing block.
     fn build_mir<'tcx, T: DropTreeBuilder<'tcx>>(
         &mut self,
         cfg: &mut CFG<'tcx>,
-        blocks: &mut IndexVec<DropIdx, Option<BasicBlock>>,
-    ) {
+        root_node: Option<BasicBlock>,
+    ) -> IndexVec<DropIdx, Option<BasicBlock>> {
         debug!("DropTree::build_mir(drops = {:#?})", self);
-        assert_eq!(blocks.len(), self.drops.len());
 
-        self.assign_blocks::<T>(cfg, blocks);
-        self.link_blocks(cfg, blocks)
+        let mut blocks = self.assign_blocks::<T>(cfg, root_node);
+        self.link_blocks(cfg, &mut blocks);
+
+        blocks
     }
 
     /// Assign blocks for all of the drops in the drop tree that need them.
     fn assign_blocks<'tcx, T: DropTreeBuilder<'tcx>>(
         &mut self,
         cfg: &mut CFG<'tcx>,
-        blocks: &mut IndexVec<DropIdx, Option<BasicBlock>>,
-    ) {
+        root_node: Option<BasicBlock>,
+    ) -> IndexVec<DropIdx, Option<BasicBlock>> {
         // StorageDead statements can share blocks with each other and also with
         // a Drop terminator. We iterate through the drops to find which drops
         // need their own block.
@@ -342,8 +340,11 @@ impl DropTree {
             Own,
         }
 
+        let mut blocks = IndexVec::from_elem(None, &self.drops);
+        blocks[ROOT_NODE] = root_node;
+
         let mut needs_block = IndexVec::from_elem(Block::None, &self.drops);
-        if blocks[ROOT_NODE].is_some() {
+        if root_node.is_some() {
             // In some cases (such as drops for `continue`) the root node
             // already has a block. In this case, make sure that we don't
             // override it.
@@ -385,6 +386,8 @@ impl DropTree {
 
         debug!("assign_blocks: blocks = {:#?}", blocks);
         assert!(entry_points.is_empty());
+
+        blocks
     }
 
     fn link_blocks<'tcx>(
@@ -1574,10 +1577,7 @@ impl<'a, 'tcx: 'a> Builder<'a, 'tcx> {
         span: Span,
         continue_block: Option<BasicBlock>,
     ) -> Option<BlockAnd<()>> {
-        let mut blocks = IndexVec::from_elem(None, &drops.drops);
-        blocks[ROOT_NODE] = continue_block;
-
-        drops.build_mir::<ExitScopes>(&mut self.cfg, &mut blocks);
+        let blocks = drops.build_mir::<ExitScopes>(&mut self.cfg, continue_block);
         let is_coroutine = self.coroutine.is_some();
 
         // Link the exit drop tree to unwind drop tree.
@@ -1633,8 +1633,7 @@ impl<'a, 'tcx: 'a> Builder<'a, 'tcx> {
         let drops = &mut self.scopes.coroutine_drops;
         let cfg = &mut self.cfg;
         let fn_span = self.fn_span;
-        let mut blocks = IndexVec::from_elem(None, &drops.drops);
-        drops.build_mir::<CoroutineDrop>(cfg, &mut blocks);
+        let blocks = drops.build_mir::<CoroutineDrop>(cfg, None);
         if let Some(root_block) = blocks[ROOT_NODE] {
             cfg.terminate(
                 root_block,
@@ -1670,9 +1669,7 @@ impl<'a, 'tcx: 'a> Builder<'a, 'tcx> {
         fn_span: Span,
         resume_block: &mut Option<BasicBlock>,
     ) {
-        let mut blocks = IndexVec::from_elem(None, &drops.drops);
-        blocks[ROOT_NODE] = *resume_block;
-        drops.build_mir::<Unwind>(cfg, &mut blocks);
+        let blocks = drops.build_mir::<Unwind>(cfg, *resume_block);
         if let (None, Some(resume)) = (*resume_block, blocks[ROOT_NODE]) {
             cfg.terminate(resume, SourceInfo::outermost(fn_span), TerminatorKind::UnwindResume);