From 7a46a0b58c20df126eb07aac5b0fcd6e07b6ec3e Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Thu, 26 Dec 2019 10:02:21 -0500
Subject: [PATCH 1/9] Inline catching panics into std::catch_unwind

This allows LLVM to inline the happy path, such that catching unwinding is
zero-cost when no panic occurs. This also allows us to match the code generated
by C++ try/catch.
---
 src/libpanic_abort/lib.rs     | 13 ++-----
 src/libpanic_unwind/dummy.rs  |  4 +-
 src/libpanic_unwind/emcc.rs   |  4 +-
 src/libpanic_unwind/gcc.rs    |  5 +--
 src/libpanic_unwind/hermit.rs |  4 +-
 src/libpanic_unwind/lib.rs    | 33 ++++------------
 src/libpanic_unwind/seh.rs    |  4 +-
 src/libstd/panicking.rs       | 71 ++++++++++++++++++++++-------------
 8 files changed, 61 insertions(+), 77 deletions(-)

diff --git a/src/libpanic_abort/lib.rs b/src/libpanic_abort/lib.rs
index db7c250e21157..ebc57860b9d4a 100644
--- a/src/libpanic_abort/lib.rs
+++ b/src/libpanic_abort/lib.rs
@@ -17,18 +17,11 @@
 #![feature(panic_runtime)]
 #![feature(staged_api)]
 #![feature(rustc_attrs)]
+#![feature(raw)]
 
-// Rust's "try" function, but if we're aborting on panics we just call the
-// function as there's nothing else we need to do here.
 #[rustc_std_internal_symbol]
-pub unsafe extern "C" fn __rust_maybe_catch_panic(
-    f: fn(*mut u8),
-    data: *mut u8,
-    _data_ptr: *mut usize,
-    _vtable_ptr: *mut usize,
-) -> u32 {
-    f(data);
-    0
+pub unsafe extern "C" fn __rust_cleanup(_: *mut u8) -> core::raw::TraitObject {
+    unreachable!()
 }
 
 // "Leak" the payload and shim to the relevant abort on the platform in
diff --git a/src/libpanic_unwind/dummy.rs b/src/libpanic_unwind/dummy.rs
index 8675632638712..30593d3b88af9 100644
--- a/src/libpanic_unwind/dummy.rs
+++ b/src/libpanic_unwind/dummy.rs
@@ -6,9 +6,7 @@ use alloc::boxed::Box;
 use core::any::Any;
 use core::intrinsics;
 
-pub fn payload() -> *mut u8 {
-    core::ptr::null_mut()
-}
+pub type Payload = *mut u8;
 
 pub unsafe fn cleanup(_ptr: *mut u8) -> Box<dyn Any + Send> {
     intrinsics::abort()
diff --git a/src/libpanic_unwind/emcc.rs b/src/libpanic_unwind/emcc.rs
index 2098404ee1b9d..2859067c098b3 100644
--- a/src/libpanic_unwind/emcc.rs
+++ b/src/libpanic_unwind/emcc.rs
@@ -48,9 +48,7 @@ static EXCEPTION_TYPE_INFO: TypeInfo = TypeInfo {
     name: b"rust_panic\0".as_ptr(),
 };
 
-pub fn payload() -> *mut u8 {
-    ptr::null_mut()
-}
+pub type Payload = *mut u8;
 
 pub unsafe fn cleanup(ptr: *mut u8) -> Box<dyn Any + Send> {
     assert!(!ptr.is_null());
diff --git a/src/libpanic_unwind/gcc.rs b/src/libpanic_unwind/gcc.rs
index e5e8e805b6e89..e09ced175051f 100644
--- a/src/libpanic_unwind/gcc.rs
+++ b/src/libpanic_unwind/gcc.rs
@@ -48,7 +48,6 @@
 
 use alloc::boxed::Box;
 use core::any::Any;
-use core::ptr;
 
 use crate::dwarf::eh::{self, EHAction, EHContext};
 use libc::{c_int, uintptr_t};
@@ -82,9 +81,7 @@ pub unsafe fn panic(data: Box<dyn Any + Send>) -> u32 {
     }
 }
 
-pub fn payload() -> *mut u8 {
-    ptr::null_mut()
-}
+pub type Payload = *mut u8;
 
 pub unsafe fn cleanup(ptr: *mut u8) -> Box<dyn Any + Send> {
     let my_ep = ptr as *mut Exception;
diff --git a/src/libpanic_unwind/hermit.rs b/src/libpanic_unwind/hermit.rs
index 2f53df2861d44..8ffb4bcd3df23 100644
--- a/src/libpanic_unwind/hermit.rs
+++ b/src/libpanic_unwind/hermit.rs
@@ -6,9 +6,7 @@ use alloc::boxed::Box;
 use core::any::Any;
 use core::ptr;
 
-pub fn payload() -> *mut u8 {
-    ptr::null_mut()
-}
+pub type Payload = *mut u8;
 
 pub unsafe fn cleanup(_ptr: *mut u8) -> Box<dyn Any + Send> {
     extern "C" {
diff --git a/src/libpanic_unwind/lib.rs b/src/libpanic_unwind/lib.rs
index e721162edc067..7481ce65d6337 100644
--- a/src/libpanic_unwind/lib.rs
+++ b/src/libpanic_unwind/lib.rs
@@ -22,19 +22,19 @@
 #![feature(libc)]
 #![feature(nll)]
 #![feature(panic_unwind)]
-#![feature(raw)]
 #![feature(staged_api)]
 #![feature(std_internals)]
 #![feature(unwind_attributes)]
+#![feature(rustc_attrs)]
+#![feature(raw)]
 #![panic_runtime]
 #![feature(panic_runtime)]
 
 use alloc::boxed::Box;
-use core::intrinsics;
-use core::mem;
 use core::panic::BoxMeUp;
-use core::raw;
 
+// If adding to this list, you should also look at libstd::panicking's identical
+// list of Payload types and likely add to there as well.
 cfg_if::cfg_if! {
     if #[cfg(target_os = "emscripten")] {
         #[path = "emcc.rs"]
@@ -62,28 +62,11 @@ cfg_if::cfg_if! {
 
 mod dwarf;
 
-// Entry point for catching an exception, implemented using the `try` intrinsic
-// in the compiler.
-//
-// The interaction between the `payload` function and the compiler is pretty
-// hairy and tightly coupled, for more information see the compiler's
-// implementation of this.
 #[no_mangle]
-pub unsafe extern "C" fn __rust_maybe_catch_panic(
-    f: fn(*mut u8),
-    data: *mut u8,
-    data_ptr: *mut usize,
-    vtable_ptr: *mut usize,
-) -> u32 {
-    let mut payload = imp::payload();
-    if intrinsics::r#try(f, data, &mut payload as *mut _ as *mut _) == 0 {
-        0
-    } else {
-        let obj = mem::transmute::<_, raw::TraitObject>(imp::cleanup(payload));
-        *data_ptr = obj.data as usize;
-        *vtable_ptr = obj.vtable as usize;
-        1
-    }
+pub unsafe extern "C" fn __rust_panic_cleanup(payload: *mut u8) -> core::raw::TraitObject {
+    let payload = payload as *mut imp::Payload;
+    let payload = *(payload);
+    core::mem::transmute(imp::cleanup(payload))
 }
 
 // Entry point for raising an exception, just delegates to the platform-specific
diff --git a/src/libpanic_unwind/seh.rs b/src/libpanic_unwind/seh.rs
index 9a28c47ba9458..3fba52eeb285f 100644
--- a/src/libpanic_unwind/seh.rs
+++ b/src/libpanic_unwind/seh.rs
@@ -264,9 +264,7 @@ pub unsafe fn panic(data: Box<dyn Any + Send>) -> u32 {
     _CxxThrowException(throw_ptr, &mut THROW_INFO as *mut _ as *mut _);
 }
 
-pub fn payload() -> [u64; 2] {
-    [0; 2]
-}
+pub type Payload = [u64; 2];
 
 pub unsafe fn cleanup(payload: [u64; 2]) -> Box<dyn Any + Send> {
     mem::transmute(raw::TraitObject { data: payload[0] as *mut _, vtable: payload[1] as *mut _ })
diff --git a/src/libstd/panicking.rs b/src/libstd/panicking.rs
index 43230d7a2c7af..c9639f999ef10 100644
--- a/src/libstd/panicking.rs
+++ b/src/libstd/panicking.rs
@@ -12,9 +12,8 @@ use core::panic::{BoxMeUp, Location, PanicInfo};
 use crate::any::Any;
 use crate::fmt;
 use crate::intrinsics;
-use crate::mem::{self, ManuallyDrop};
+use crate::mem::{self, ManuallyDrop, MaybeUninit};
 use crate::process;
-use crate::raw;
 use crate::sync::atomic::{AtomicBool, Ordering};
 use crate::sys::stdio::panic_output;
 use crate::sys_common::backtrace::{self, RustBacktrace};
@@ -29,6 +28,31 @@ use crate::io::set_panic;
 #[cfg(test)]
 use realstd::io::set_panic;
 
+// This must be kept in sync with the implementations in libpanic_unwind.
+//
+// This is *not* checked in anyway; the compiler does not allow us to use a
+// type/macro/anything from panic_unwind, since we're then linking in the
+// panic_unwind runtime even during -Cpanic=abort.
+//
+// Essentially this must be the type of `imp::Payload` in libpanic_unwind.
+cfg_if::cfg_if! {
+    if #[cfg(not(feature = "panic_unwind"))] {
+        type Payload = ();
+    } else if #[cfg(target_os = "emscripten")] {
+        type Payload = *mut u8;
+    } else if #[cfg(target_arch = "wasm32")] {
+        type Payload = *mut u8;
+    } else if #[cfg(target_os = "hermit")] {
+        type Payload = *mut u8;
+    } else if #[cfg(all(target_env = "msvc", target_arch = "aarch64"))] {
+        type Payload = *mut u8;
+    } else if #[cfg(target_env = "msvc")] {
+        type Payload = [u64; 2];
+    } else {
+        type Payload = *mut u8;
+    }
+}
+
 // Binary interface to the panic runtime that the standard library depends on.
 //
 // The standard library is tagged with `#![needs_panic_runtime]` (introduced in
@@ -41,12 +65,10 @@ use realstd::io::set_panic;
 // hook up these functions, but it is not this day!
 #[allow(improper_ctypes)]
 extern "C" {
-    fn __rust_maybe_catch_panic(
-        f: fn(*mut u8),
-        data: *mut u8,
-        data_ptr: *mut usize,
-        vtable_ptr: *mut usize,
-    ) -> u32;
+    /// The payload ptr here is actually the same as the payload ptr for the try
+    /// intrinsic (i.e., is really `*mut [u64; 2]` or `*mut *mut u8`).
+    #[unwind(allowed)]
+    fn __rust_panic_cleanup(payload: *mut u8) -> core::raw::TraitObject;
 
     /// `payload` is actually a `*mut &mut dyn BoxMeUp` but that would cause FFI warnings.
     /// It cannot be `Box<dyn BoxMeUp>` because the other end of this call does not depend
@@ -241,9 +263,9 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
     }
 
     // We do some sketchy operations with ownership here for the sake of
-    // performance. We can only  pass pointers down to
-    // `__rust_maybe_catch_panic` (can't pass objects by value), so we do all
-    // the ownership tracking here manually using a union.
+    // performance. We can only pass pointers down to `do_call` (can't pass
+    // objects by value), so we do all the ownership tracking here manually
+    // using a union.
     //
     // We go through a transition where:
     //
@@ -254,7 +276,7 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
     // * If the closure successfully returns, we write the return value into the
     //   data's return slot. Note that `ptr::write` is used as it's overwriting
     //   uninitialized data.
-    // * Finally, when we come back out of the `__rust_maybe_catch_panic` we're
+    // * Finally, when we come back out of the `try` intrinsic we're
     //   in one of two states:
     //
     //      1. The closure didn't panic, in which case the return value was
@@ -265,28 +287,25 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
     //
     // Once we stack all that together we should have the "most efficient'
     // method of calling a catch panic whilst juggling ownership.
-    let mut any_data = 0;
-    let mut any_vtable = 0;
     let mut data = Data { f: ManuallyDrop::new(f) };
 
-    let r = __rust_maybe_catch_panic(
-        do_call::<F, R>,
-        &mut data as *mut _ as *mut u8,
-        &mut any_data,
-        &mut any_vtable,
-    );
+    let mut payload: MaybeUninit<Payload> = MaybeUninit::uninit();
 
-    return if r == 0 {
+    let data_ptr = &mut data as *mut _ as *mut u8;
+    let payload_ptr = payload.as_mut_ptr() as *mut _;
+    return if intrinsics::r#try(do_call::<F, R>, data_ptr, payload_ptr) == 0 {
         debug_assert!(update_panic_count(0) == 0);
         Ok(ManuallyDrop::into_inner(data.r))
     } else {
+        Err(cleanup(payload.assume_init()))
+    };
+
+    unsafe fn cleanup(mut payload: Payload) -> Box<dyn Any + Send + 'static> {
+        let obj = crate::mem::transmute(__rust_panic_cleanup(&mut payload as *mut _ as *mut u8));
         update_panic_count(-1);
         debug_assert!(update_panic_count(0) == 0);
-        Err(mem::transmute(raw::TraitObject {
-            data: any_data as *mut _,
-            vtable: any_vtable as *mut _,
-        }))
-    };
+        obj
+    }
 
     fn do_call<F: FnOnce() -> R, R>(data: *mut u8) {
         unsafe {

From e177b9129fb6ca50730de1b52489a39c791748bb Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Thu, 26 Dec 2019 10:03:41 -0500
Subject: [PATCH 2/9] Avoid over-aligning the return value in the -Cpanic=abort
 case

---
 src/librustc_codegen_llvm/intrinsic.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/librustc_codegen_llvm/intrinsic.rs b/src/librustc_codegen_llvm/intrinsic.rs
index abb17b3b0f116..a18ea051e5d2d 100644
--- a/src/librustc_codegen_llvm/intrinsic.rs
+++ b/src/librustc_codegen_llvm/intrinsic.rs
@@ -858,8 +858,10 @@ fn try_intrinsic(
 ) {
     if bx.sess().no_landing_pads() {
         bx.call(func, &[data], None);
-        let ptr_align = bx.tcx().data_layout.pointer_align.abi;
-        bx.store(bx.const_null(bx.type_i8p()), dest, ptr_align);
+        // Return 0 unconditionally from the intrinsic call;
+        // we can never unwind.
+        let ret_align = bx.tcx().data_layout.i32_align.abi;
+        bx.store(bx.const_i32(0), dest, ret_align);
     } else if wants_msvc_seh(bx.sess()) {
         codegen_msvc_try(bx, func, data, local_ptr, dest);
     } else {

From 85ec3ecd137251d522d1991ac60ed484724f2123 Mon Sep 17 00:00:00 2001
From: Amanieu d'Antras <amanieu@gmail.com>
Date: Thu, 26 Dec 2019 10:37:48 -0500
Subject: [PATCH 3/9] Test catch_unwind vanishing

We execpt the try intrinsic to be a direct call if in -Cpanic=abort mode, and
that catch_unwind optimizes out if calling a function that does not unwind.
---
 src/test/codegen/catch-unwind.rs    | 19 +++++++++++++++++++
 src/test/codegen/try-panic-abort.rs | 17 +++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 src/test/codegen/catch-unwind.rs
 create mode 100644 src/test/codegen/try-panic-abort.rs

diff --git a/src/test/codegen/catch-unwind.rs b/src/test/codegen/catch-unwind.rs
new file mode 100644
index 0000000000000..3c9bc35d1c8bd
--- /dev/null
+++ b/src/test/codegen/catch-unwind.rs
@@ -0,0 +1,19 @@
+// compile-flags: -O
+
+#![crate_type = "lib"]
+
+extern "C" {
+    fn bar();
+}
+
+// CHECK-LABEL: @foo
+#[no_mangle]
+pub unsafe fn foo() -> i32 {
+    // CHECK: call void @bar
+    // CHECK: ret i32 0
+    std::panic::catch_unwind(|| {
+        bar();
+        0
+    })
+    .unwrap()
+}
diff --git a/src/test/codegen/try-panic-abort.rs b/src/test/codegen/try-panic-abort.rs
new file mode 100644
index 0000000000000..9bc89a321576c
--- /dev/null
+++ b/src/test/codegen/try-panic-abort.rs
@@ -0,0 +1,17 @@
+// compile-flags: -C panic=abort -O
+
+#![crate_type = "lib"]
+#![feature(unwind_attributes, core_intrinsics)]
+
+extern "C" {
+    #[unwind(allow)]
+    fn bar(data: *mut u8);
+}
+
+// CHECK-LABEL: @foo
+#[no_mangle]
+pub unsafe fn foo() -> i32 {
+    // CHECK: call void @bar
+    // CHECK: ret i32 0
+    std::intrinsics::r#try(|x| bar(x), 0 as *mut u8, 0 as *mut u8)
+}

From 310903629389c964f8d1532a5c43f662d1d98a8e Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Thu, 26 Dec 2019 10:49:16 -0500
Subject: [PATCH 4/9] Ignore PAL lint for std::panicking

---
 src/tools/tidy/src/pal.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/tools/tidy/src/pal.rs b/src/tools/tidy/src/pal.rs
index dcd4c9e8ef7d9..31fc6f10e8296 100644
--- a/src/tools/tidy/src/pal.rs
+++ b/src/tools/tidy/src/pal.rs
@@ -59,6 +59,8 @@ const EXCEPTION_PATHS: &[&str] = &[
     "src/libstd/sys_common/mod.rs",
     "src/libstd/sys_common/net.rs",
     "src/libstd/sys_common/backtrace.rs",
+    // panic_unwind shims
+    "src/libstd/panicking.rs",
     "src/libterm", // Not sure how to make this crate portable, but test crate needs it.
     "src/libtest", // Probably should defer to unstable `std::sys` APIs.
     "src/libstd/sync/mpsc", // some tests are only run on non-emscripten

From f3da0eaba3720bbd72d2e503ec089add25b6a242 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Thu, 26 Dec 2019 10:54:24 -0500
Subject: [PATCH 5/9] Mark cleanup cold

---
 src/libstd/panicking.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/libstd/panicking.rs b/src/libstd/panicking.rs
index c9639f999ef10..2941504cbc3b9 100644
--- a/src/libstd/panicking.rs
+++ b/src/libstd/panicking.rs
@@ -300,6 +300,11 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
         Err(cleanup(payload.assume_init()))
     };
 
+    // We consider unwinding to be rare, so mark this function as cold. However,
+    // do not mark it no-inline -- that decision is best to leave to the
+    // optimizer (in most cases this function is not inlined even as a normal,
+    // non-cold function, though, as of the writing of this comment).
+    #[cold]
     unsafe fn cleanup(mut payload: Payload) -> Box<dyn Any + Send + 'static> {
         let obj = crate::mem::transmute(__rust_panic_cleanup(&mut payload as *mut _ as *mut u8));
         update_panic_count(-1);

From 5e320df95b75207fd501642647199fae0d449a2a Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Thu, 26 Dec 2019 11:17:18 -0500
Subject: [PATCH 6/9] fixup! Inline catching panics into std::catch_unwind

---
 src/libstd/panicking.rs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/libstd/panicking.rs b/src/libstd/panicking.rs
index 2941504cbc3b9..71105624428be 100644
--- a/src/libstd/panicking.rs
+++ b/src/libstd/panicking.rs
@@ -67,7 +67,6 @@ cfg_if::cfg_if! {
 extern "C" {
     /// The payload ptr here is actually the same as the payload ptr for the try
     /// intrinsic (i.e., is really `*mut [u64; 2]` or `*mut *mut u8`).
-    #[unwind(allowed)]
     fn __rust_panic_cleanup(payload: *mut u8) -> core::raw::TraitObject;
 
     /// `payload` is actually a `*mut &mut dyn BoxMeUp` but that would cause FFI warnings.

From 4ad9a3c4100d674dc6010a0acff3c73e56fc4151 Mon Sep 17 00:00:00 2001
From: Amanieu d'Antras <amanieu@gmail.com>
Date: Thu, 26 Dec 2019 19:37:14 +0100
Subject: [PATCH 7/9] Fix some minor issues

---
 src/libpanic_abort/lib.rs  | 5 +++--
 src/libpanic_unwind/lib.rs | 5 +++--
 src/libstd/panicking.rs    | 4 ++--
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/libpanic_abort/lib.rs b/src/libpanic_abort/lib.rs
index ebc57860b9d4a..fe9196ef2314b 100644
--- a/src/libpanic_abort/lib.rs
+++ b/src/libpanic_abort/lib.rs
@@ -17,10 +17,11 @@
 #![feature(panic_runtime)]
 #![feature(staged_api)]
 #![feature(rustc_attrs)]
-#![feature(raw)]
+
+use core::any::Any;
 
 #[rustc_std_internal_symbol]
-pub unsafe extern "C" fn __rust_cleanup(_: *mut u8) -> core::raw::TraitObject {
+pub unsafe extern "C" fn __rust_panic_cleanup(_: *mut u8) -> *mut (dyn Any + Send + 'static) {
     unreachable!()
 }
 
diff --git a/src/libpanic_unwind/lib.rs b/src/libpanic_unwind/lib.rs
index 7481ce65d6337..ba417d0b014cd 100644
--- a/src/libpanic_unwind/lib.rs
+++ b/src/libpanic_unwind/lib.rs
@@ -31,6 +31,7 @@
 #![feature(panic_runtime)]
 
 use alloc::boxed::Box;
+use core::any::Any;
 use core::panic::BoxMeUp;
 
 // If adding to this list, you should also look at libstd::panicking's identical
@@ -63,10 +64,10 @@ cfg_if::cfg_if! {
 mod dwarf;
 
 #[no_mangle]
-pub unsafe extern "C" fn __rust_panic_cleanup(payload: *mut u8) -> core::raw::TraitObject {
+pub unsafe extern "C" fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any + Send + 'static) {
     let payload = payload as *mut imp::Payload;
     let payload = *(payload);
-    core::mem::transmute(imp::cleanup(payload))
+    Box::into_raw(imp::cleanup(payload))
 }
 
 // Entry point for raising an exception, just delegates to the platform-specific
diff --git a/src/libstd/panicking.rs b/src/libstd/panicking.rs
index 71105624428be..71097d5e232eb 100644
--- a/src/libstd/panicking.rs
+++ b/src/libstd/panicking.rs
@@ -67,7 +67,7 @@ cfg_if::cfg_if! {
 extern "C" {
     /// The payload ptr here is actually the same as the payload ptr for the try
     /// intrinsic (i.e., is really `*mut [u64; 2]` or `*mut *mut u8`).
-    fn __rust_panic_cleanup(payload: *mut u8) -> core::raw::TraitObject;
+    fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any + Send + 'static);
 
     /// `payload` is actually a `*mut &mut dyn BoxMeUp` but that would cause FFI warnings.
     /// It cannot be `Box<dyn BoxMeUp>` because the other end of this call does not depend
@@ -305,7 +305,7 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
     // non-cold function, though, as of the writing of this comment).
     #[cold]
     unsafe fn cleanup(mut payload: Payload) -> Box<dyn Any + Send + 'static> {
-        let obj = crate::mem::transmute(__rust_panic_cleanup(&mut payload as *mut _ as *mut u8));
+        let obj = Box::from_raw(__rust_panic_cleanup(&mut payload as *mut _ as *mut u8));
         update_panic_count(-1);
         debug_assert!(update_panic_count(0) == 0);
         obj

From 5be658a62b5291c39897deac07f9c1ccf576b706 Mon Sep 17 00:00:00 2001
From: Amanieu d'Antras <amanieu@gmail.com>
Date: Sun, 29 Dec 2019 12:07:44 +0100
Subject: [PATCH 8/9] Ignore broken no-landing-pads test

---
 src/test/ui/no-landing-pads.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/test/ui/no-landing-pads.rs b/src/test/ui/no-landing-pads.rs
index d9d532106125a..44af25f7f8f48 100644
--- a/src/test/ui/no-landing-pads.rs
+++ b/src/test/ui/no-landing-pads.rs
@@ -1,6 +1,7 @@
 // run-pass
 // compile-flags: -Z no-landing-pads -C codegen-units=1
 // ignore-emscripten no threads support
+// ignore-test fails because catch_unwind doesn't work with no-landing-pads
 
 use std::thread;
 

From da5b1a4a50d06af068e192858853eda21cbbf385 Mon Sep 17 00:00:00 2001
From: Amanieu d'Antras <amanieu@gmail.com>
Date: Tue, 7 Jan 2020 16:41:59 +0100
Subject: [PATCH 9/9] Apply review feedback

---
 Cargo.lock                     |  1 +
 src/libpanic_abort/Cargo.toml  |  1 +
 src/libpanic_abort/lib.rs      |  5 ++++-
 src/libpanic_unwind/dummy.rs   |  2 --
 src/libpanic_unwind/emcc.rs    |  2 --
 src/libpanic_unwind/gcc.rs     |  2 --
 src/libpanic_unwind/hermit.rs  |  2 --
 src/libpanic_unwind/lib.rs     | 12 +++++++-----
 src/libpanic_unwind/payload.rs | 21 +++++++++++++++++++++
 src/libpanic_unwind/seh.rs     |  2 --
 src/libstd/panicking.rs        | 34 ++++++----------------------------
 src/test/ui/no-landing-pads.rs | 24 ------------------------
 12 files changed, 40 insertions(+), 68 deletions(-)
 create mode 100644 src/libpanic_unwind/payload.rs
 delete mode 100644 src/test/ui/no-landing-pads.rs

diff --git a/Cargo.lock b/Cargo.lock
index f3fad1296bfd7..6a08ea2e326fd 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2301,6 +2301,7 @@ dependencies = [
 name = "panic_abort"
 version = "0.0.0"
 dependencies = [
+ "cfg-if",
  "compiler_builtins",
  "core",
  "libc",
diff --git a/src/libpanic_abort/Cargo.toml b/src/libpanic_abort/Cargo.toml
index 2bee0b716c750..8ebd95047ac23 100644
--- a/src/libpanic_abort/Cargo.toml
+++ b/src/libpanic_abort/Cargo.toml
@@ -14,3 +14,4 @@ doc = false
 core = { path = "../libcore" }
 libc = { version = "0.2", default-features = false }
 compiler_builtins = "0.1.0"
+cfg-if = "0.1.8"
diff --git a/src/libpanic_abort/lib.rs b/src/libpanic_abort/lib.rs
index fe9196ef2314b..6ea818ecef827 100644
--- a/src/libpanic_abort/lib.rs
+++ b/src/libpanic_abort/lib.rs
@@ -20,8 +20,11 @@
 
 use core::any::Any;
 
+// We need the definition of TryPayload for __rust_panic_cleanup.
+include!("../libpanic_unwind/payload.rs");
+
 #[rustc_std_internal_symbol]
-pub unsafe extern "C" fn __rust_panic_cleanup(_: *mut u8) -> *mut (dyn Any + Send + 'static) {
+pub unsafe extern "C" fn __rust_panic_cleanup(_: TryPayload) -> *mut (dyn Any + Send + 'static) {
     unreachable!()
 }
 
diff --git a/src/libpanic_unwind/dummy.rs b/src/libpanic_unwind/dummy.rs
index 30593d3b88af9..4667ede2baad5 100644
--- a/src/libpanic_unwind/dummy.rs
+++ b/src/libpanic_unwind/dummy.rs
@@ -6,8 +6,6 @@ use alloc::boxed::Box;
 use core::any::Any;
 use core::intrinsics;
 
-pub type Payload = *mut u8;
-
 pub unsafe fn cleanup(_ptr: *mut u8) -> Box<dyn Any + Send> {
     intrinsics::abort()
 }
diff --git a/src/libpanic_unwind/emcc.rs b/src/libpanic_unwind/emcc.rs
index 2859067c098b3..f77c1f53c4646 100644
--- a/src/libpanic_unwind/emcc.rs
+++ b/src/libpanic_unwind/emcc.rs
@@ -48,8 +48,6 @@ static EXCEPTION_TYPE_INFO: TypeInfo = TypeInfo {
     name: b"rust_panic\0".as_ptr(),
 };
 
-pub type Payload = *mut u8;
-
 pub unsafe fn cleanup(ptr: *mut u8) -> Box<dyn Any + Send> {
     assert!(!ptr.is_null());
     let adjusted_ptr = __cxa_begin_catch(ptr as *mut libc::c_void);
diff --git a/src/libpanic_unwind/gcc.rs b/src/libpanic_unwind/gcc.rs
index e09ced175051f..fa48db611993f 100644
--- a/src/libpanic_unwind/gcc.rs
+++ b/src/libpanic_unwind/gcc.rs
@@ -81,8 +81,6 @@ pub unsafe fn panic(data: Box<dyn Any + Send>) -> u32 {
     }
 }
 
-pub type Payload = *mut u8;
-
 pub unsafe fn cleanup(ptr: *mut u8) -> Box<dyn Any + Send> {
     let my_ep = ptr as *mut Exception;
     let cause = (*my_ep).cause.take();
diff --git a/src/libpanic_unwind/hermit.rs b/src/libpanic_unwind/hermit.rs
index 8ffb4bcd3df23..6bded4dd499bd 100644
--- a/src/libpanic_unwind/hermit.rs
+++ b/src/libpanic_unwind/hermit.rs
@@ -6,8 +6,6 @@ use alloc::boxed::Box;
 use core::any::Any;
 use core::ptr;
 
-pub type Payload = *mut u8;
-
 pub unsafe fn cleanup(_ptr: *mut u8) -> Box<dyn Any + Send> {
     extern "C" {
         pub fn __rust_abort() -> !;
diff --git a/src/libpanic_unwind/lib.rs b/src/libpanic_unwind/lib.rs
index ba417d0b014cd..adac6ce18e900 100644
--- a/src/libpanic_unwind/lib.rs
+++ b/src/libpanic_unwind/lib.rs
@@ -34,8 +34,8 @@ use alloc::boxed::Box;
 use core::any::Any;
 use core::panic::BoxMeUp;
 
-// If adding to this list, you should also look at libstd::panicking's identical
-// list of Payload types and likely add to there as well.
+// If adding to this list, you should also look at the list of TryPayload types
+// defined in payload.rs and likely add to there as well.
 cfg_if::cfg_if! {
     if #[cfg(target_os = "emscripten")] {
         #[path = "emcc.rs"]
@@ -61,12 +61,14 @@ cfg_if::cfg_if! {
     }
 }
 
+include!("payload.rs");
+
 mod dwarf;
 
 #[no_mangle]
-pub unsafe extern "C" fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any + Send + 'static) {
-    let payload = payload as *mut imp::Payload;
-    let payload = *(payload);
+pub unsafe extern "C" fn __rust_panic_cleanup(
+    payload: TryPayload,
+) -> *mut (dyn Any + Send + 'static) {
     Box::into_raw(imp::cleanup(payload))
 }
 
diff --git a/src/libpanic_unwind/payload.rs b/src/libpanic_unwind/payload.rs
new file mode 100644
index 0000000000000..1234db7da0f08
--- /dev/null
+++ b/src/libpanic_unwind/payload.rs
@@ -0,0 +1,21 @@
+// Type definition for the payload argument of the try intrinsic.
+//
+// This must be kept in sync with the implementations of the try intrinsic.
+//
+// This file is included by both panic runtimes and libstd. It is part of the
+// panic runtime ABI.
+cfg_if::cfg_if! {
+    if #[cfg(target_os = "emscripten")] {
+        type TryPayload = *mut u8;
+    } else if #[cfg(target_arch = "wasm32")] {
+        type TryPayload = *mut u8;
+    } else if #[cfg(target_os = "hermit")] {
+        type TryPayload = *mut u8;
+    } else if #[cfg(all(target_env = "msvc", target_arch = "aarch64"))] {
+        type TryPayload = *mut u8;
+    } else if #[cfg(target_env = "msvc")] {
+        type TryPayload = [u64; 2];
+    } else {
+        type TryPayload = *mut u8;
+    }
+}
diff --git a/src/libpanic_unwind/seh.rs b/src/libpanic_unwind/seh.rs
index 3fba52eeb285f..4460fba9f6902 100644
--- a/src/libpanic_unwind/seh.rs
+++ b/src/libpanic_unwind/seh.rs
@@ -264,8 +264,6 @@ pub unsafe fn panic(data: Box<dyn Any + Send>) -> u32 {
     _CxxThrowException(throw_ptr, &mut THROW_INFO as *mut _ as *mut _);
 }
 
-pub type Payload = [u64; 2];
-
 pub unsafe fn cleanup(payload: [u64; 2]) -> Box<dyn Any + Send> {
     mem::transmute(raw::TraitObject { data: payload[0] as *mut _, vtable: payload[1] as *mut _ })
 }
diff --git a/src/libstd/panicking.rs b/src/libstd/panicking.rs
index 71097d5e232eb..a8e559e8d783a 100644
--- a/src/libstd/panicking.rs
+++ b/src/libstd/panicking.rs
@@ -28,30 +28,8 @@ use crate::io::set_panic;
 #[cfg(test)]
 use realstd::io::set_panic;
 
-// This must be kept in sync with the implementations in libpanic_unwind.
-//
-// This is *not* checked in anyway; the compiler does not allow us to use a
-// type/macro/anything from panic_unwind, since we're then linking in the
-// panic_unwind runtime even during -Cpanic=abort.
-//
-// Essentially this must be the type of `imp::Payload` in libpanic_unwind.
-cfg_if::cfg_if! {
-    if #[cfg(not(feature = "panic_unwind"))] {
-        type Payload = ();
-    } else if #[cfg(target_os = "emscripten")] {
-        type Payload = *mut u8;
-    } else if #[cfg(target_arch = "wasm32")] {
-        type Payload = *mut u8;
-    } else if #[cfg(target_os = "hermit")] {
-        type Payload = *mut u8;
-    } else if #[cfg(all(target_env = "msvc", target_arch = "aarch64"))] {
-        type Payload = *mut u8;
-    } else if #[cfg(target_env = "msvc")] {
-        type Payload = [u64; 2];
-    } else {
-        type Payload = *mut u8;
-    }
-}
+// Include the definition of UnwindPayload from libpanic_unwind.
+include!("../libpanic_unwind/payload.rs");
 
 // Binary interface to the panic runtime that the standard library depends on.
 //
@@ -67,7 +45,7 @@ cfg_if::cfg_if! {
 extern "C" {
     /// The payload ptr here is actually the same as the payload ptr for the try
     /// intrinsic (i.e., is really `*mut [u64; 2]` or `*mut *mut u8`).
-    fn __rust_panic_cleanup(payload: *mut u8) -> *mut (dyn Any + Send + 'static);
+    fn __rust_panic_cleanup(payload: TryPayload) -> *mut (dyn Any + Send + 'static);
 
     /// `payload` is actually a `*mut &mut dyn BoxMeUp` but that would cause FFI warnings.
     /// It cannot be `Box<dyn BoxMeUp>` because the other end of this call does not depend
@@ -288,7 +266,7 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
     // method of calling a catch panic whilst juggling ownership.
     let mut data = Data { f: ManuallyDrop::new(f) };
 
-    let mut payload: MaybeUninit<Payload> = MaybeUninit::uninit();
+    let mut payload: MaybeUninit<TryPayload> = MaybeUninit::uninit();
 
     let data_ptr = &mut data as *mut _ as *mut u8;
     let payload_ptr = payload.as_mut_ptr() as *mut _;
@@ -304,8 +282,8 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
     // optimizer (in most cases this function is not inlined even as a normal,
     // non-cold function, though, as of the writing of this comment).
     #[cold]
-    unsafe fn cleanup(mut payload: Payload) -> Box<dyn Any + Send + 'static> {
-        let obj = Box::from_raw(__rust_panic_cleanup(&mut payload as *mut _ as *mut u8));
+    unsafe fn cleanup(payload: TryPayload) -> Box<dyn Any + Send + 'static> {
+        let obj = Box::from_raw(__rust_panic_cleanup(payload));
         update_panic_count(-1);
         debug_assert!(update_panic_count(0) == 0);
         obj
diff --git a/src/test/ui/no-landing-pads.rs b/src/test/ui/no-landing-pads.rs
deleted file mode 100644
index 44af25f7f8f48..0000000000000
--- a/src/test/ui/no-landing-pads.rs
+++ /dev/null
@@ -1,24 +0,0 @@
-// run-pass
-// compile-flags: -Z no-landing-pads -C codegen-units=1
-// ignore-emscripten no threads support
-// ignore-test fails because catch_unwind doesn't work with no-landing-pads
-
-use std::thread;
-
-static mut HIT: bool = false;
-
-struct A;
-
-impl Drop for A {
-    fn drop(&mut self) {
-        unsafe { HIT = true; }
-    }
-}
-
-fn main() {
-    thread::spawn(move|| -> () {
-        let _a = A;
-        panic!();
-    }).join().unwrap_err();
-    assert!(unsafe { !HIT });
-}