Auto merge of rust-lang#71044 - ecstatic-morse:body-predecessor-cache, r=oli-obk

Remove `BodyAndCache`

...returning to the original approach using interior mutability within `Body`. This simplifies the API at the cost of some uncontended mutex locks when the parallel compiler is enabled.

The current API requires you to either have a mutable reference to `Body` (`&mut BodyAndCache`), or to compute the predecessor graph ahead of time by creating a `ReadOnlyBodyAndCache`. This is not a good fit for, e.g., the dataflow framework, which
1. does not mutate the MIR
2. only sometimes needs the predecessor graph (for backward dataflow problems)

Author: bors

src/librustc_codegen_ssa/mir/analyze.rs

@@ -120,7 +120,7 @@ impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
             };
             if is_consume {
                 let base_ty =
-                    mir::Place::ty_from(place_ref.local, proj_base, *self.fx.mir, cx.tcx());
+                    mir::Place::ty_from(place_ref.local, proj_base, self.fx.mir, cx.tcx());
                 let base_ty = self.fx.monomorphize(&base_ty);
 
                 // ZSTs don't require any actual memory access.

src/librustc_codegen_ssa/mir/block.rs

@@ -152,7 +152,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
     // a loop.
     fn maybe_sideeffect<Bx: BuilderMethods<'a, 'tcx>>(
         &self,
-        mir: mir::ReadOnlyBodyAndCache<'tcx, 'tcx>,
+        mir: &'tcx mir::Body<'tcx>,
         bx: &mut Bx,
         targets: &[mir::BasicBlock],
     ) {
@@ -306,7 +306,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         target: mir::BasicBlock,
         unwind: Option<mir::BasicBlock>,
     ) {
-        let ty = location.ty(*self.mir, bx.tcx()).ty;
+        let ty = location.ty(self.mir, bx.tcx()).ty;
         let ty = self.monomorphize(&ty);
         let drop_fn = Instance::resolve_drop_in_place(bx.tcx(), ty);
 
@@ -572,7 +572,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         let extra_args = extra_args
             .iter()
             .map(|op_arg| {
-                let op_ty = op_arg.ty(*self.mir, bx.tcx());
+                let op_ty = op_arg.ty(self.mir, bx.tcx());
                 self.monomorphize(&op_ty)
             })
             .collect::<Vec<_>>();