Emulate <Box<F> as FnOnce>::call_once without alloca

Fixes rust-lang#884

cc rust-lang#15

patches/0017-Fix-libtest-compilation.patch

@@ -11,24 +11,6 @@ diff --git a/src/libtest/lib.rs b/src/libtest/lib.rs
 index 8b76080..9e65de2 100644
 --- a/src/libtest/lib.rs
 +++ b/src/libtest/lib.rs
-@@ -52,7 +52,7 @@ use std::fmt;
- use std::{
-     env, io,
-     io::prelude::Write,
--    panic::{self, catch_unwind, AssertUnwindSafe, PanicInfo},
-+    panic::{self, PanicInfo},
-     process::{self, Command, Termination},
-     sync::mpsc::{channel, Sender},
-     sync::{Arc, Mutex},
-@@ -1493,7 +1493,7 @@ pub fn run_test(
-     fn run_test_inner(
-         desc: TestDesc,
-         monitor_ch: Sender<CompletedTest>,
--        testfn: Box<dyn FnOnce() + Send>,
-+        testfn: Box<impl FnOnce() + Send + 'static>,
-         opts: TestRunOpts,
-     ) {
-         let concurrency = opts.concurrency;
 @@ -1509,7 +1509,7 @@ pub fn run_test(
          // If the platform is single-threaded we're just going to run
          // the test synchronously, regardless of the concurrency
@@ -38,55 +20,5 @@ index 8b76080..9e65de2 100644
          if concurrency == Concurrent::Yes && supports_threads {
              let cfg = thread::Builder::new().name(name.as_slice().to_owned());
              cfg.spawn(runtest).unwrap();
-@@ -1531,17 +1531,8 @@ pub fn run_test(
-             // Benchmarks aren't expected to panic, so we run them all in-process.
-             crate::bench::benchmark(desc, monitor_ch, opts.nocapture, benchfn);
-         }
--        DynTestFn(f) => {
--            match strategy {
--                RunStrategy::InProcess => (),
--                _ => panic!("Cannot run dynamic test fn out-of-process"),
--            };
--            run_test_inner(
--                desc,
--                monitor_ch,
--                Box::new(move || __rust_begin_short_backtrace(f)),
--                test_run_opts,
--            );
-+        DynTestFn(_f) => {
-+            unimplemented!();
-         }
-         StaticTestFn(f) => run_test_inner(
-             desc,
-@@ -1604,10 +1592,10 @@ fn get_result_from_exit_code(desc: &TestDesc, code: i32) -> TestResult {
- fn run_test_in_process(
-     desc: TestDesc,
-     nocapture: bool,
-     report_time: bool,
--    testfn: Box<dyn FnOnce() + Send>,
-+    testfn: Box<impl FnOnce() + Send + 'static>,
-     monitor_ch: Sender<CompletedTest>,
-     time_opts: Option<time::TestTimeOptions>,
- ) {
-     // Buffer for capturing standard I/O
-     let data = Arc::new(Mutex::new(Vec::new()));
-@@ -1623,7 +1611,7 @@ fn run_test_in_process(desc: TestDesc,
-     };
-
-     let start = report_time.then(Instant::now);
--    let result = catch_unwind(AssertUnwindSafe(testfn));
-+    let result = Ok::<(), Box<dyn std::any::Any + Send>>(testfn());
-     let exec_time = start.map(|start| {
-         let duration = start.elapsed();
-         TestExecTime(duration)
-@@ -1688,7 +1676,7 @@ fn spawn_test_subprocess(desc: TestDesc, report_time: bool, monitor_ch: Sender<M
-     monitor_ch.send(message).unwrap();
- }
-
--fn run_test_in_spawned_subprocess(desc: TestDesc, testfn: Box<dyn FnOnce() + Send>) -> ! {
-+fn run_test_in_spawned_subprocess(desc: TestDesc, testfn: Box<impl FnOnce() + Send + 'static>) -> ! {
-     let builtin_panic_hook = panic::take_hook();
-     let record_result = Arc::new(move |panic_info: Option<&'_ PanicInfo<'_>>| {
-         let test_result = match panic_info {
 -- 
 2.20.1

src/abi/mod.rs

@@ -288,7 +288,7 @@ fn local_place<'tcx>(
     fx.local_map[&local]
 }
 
-pub fn codegen_fn_prelude(fx: &mut FunctionCx<'_, '_, impl Backend>, start_block: Block) {
+pub fn codegen_fn_prelude(fx: &mut FunctionCx<'_, '_, impl Backend>, start_block: Block, should_codegen_locals: bool) {
     let ssa_analyzed = crate::analyze::analyze(fx);
 
     #[cfg(debug_assertions)]
@@ -405,13 +405,17 @@ pub fn codegen_fn_prelude(fx: &mut FunctionCx<'_, '_, impl Backend>, start_block
         }
     }
 
-    for local in fx.mir.vars_and_temps_iter() {
-        let ty = fx.monomorphize(&fx.mir.local_decls[local].ty);
-        let layout = fx.layout_of(ty);
+    // HACK should_codegen_locals required for the ``implement `<Box<F> as FnOnce>::call_once`
+    // without `alloca``` hack in `base::trans_fn`.
+    if should_codegen_locals {
+        for local in fx.mir.vars_and_temps_iter() {
+            let ty = fx.monomorphize(&fx.mir.local_decls[local].ty);
+            let layout = fx.layout_of(ty);
 
-        let is_ssa = ssa_analyzed[local] == crate::analyze::SsaKind::Ssa;
+            let is_ssa = ssa_analyzed[local] == crate::analyze::SsaKind::Ssa;
 
-        local_place(fx, local, layout, is_ssa);
+            local_place(fx, local, layout, is_ssa);
+        }
     }
 
     fx.bcx