rustc: Implement custom panic runtimes

This commit is an implementation of [RFC 1513] which allows applications to
alter the behavior of panics at compile time. A new compiler flag, `-C panic`,
is added and accepts the values `unwind` or `panic`, with the default being
`unwind`. This model affects how code is generated for the local crate, skipping
generation of landing pads with `-C panic=abort`.

[RFC 1513]: https://github.com/rust-lang/rfcs/blob/master/text/1513-less-unwinding.md

Panic implementations are then provided by crates tagged with
`#![panic_runtime]` and lazily required by crates with
`#![needs_panic_runtime]`. The panic strategy (`-C panic` value) of the panic
runtime must match the final product, and if the panic strategy is not `abort`
then the entire DAG must have the same panic strategy.

With the `-C panic=abort` strategy, users can expect a stable method to disable
generation of landing pads, improving optimization in niche scenarios,
decreasing compile time, and decreasing output binary size. With the `-C
panic=unwind` strategy users can expect the existing ability to isolate failure
in Rust code from the outside world.

Organizationally, this commit dismantles the `sys_common::unwind` module in
favor of some bits moving part of it to `libpanic_unwind` and the rest into the
`panicking` module in libstd. The custom panic runtime support is pretty similar
to the custom allocator support with the only major difference being how the
panic runtime is injected (takes the `-C panic` flag into account).

4 files changed, 0 insertions, 819 deletions

diff --git a/src/libstd/sys/common/unwind/gcc.rs b/src/libstd/sys/common/unwind/gcc.rs
deleted file mode 100644
index da7a340af35..00000000000
--- a/src/libstd/sys/common/unwind/gcc.rs
+++ /dev/null
@@ -1,280 +0,0 @@
-// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-#![allow(private_no_mangle_fns)]
-
-use prelude::v1::*;
-
-use any::Any;
-use sys_common::libunwind as uw;
-
-struct Exception {
-    uwe: uw::_Unwind_Exception,
-    cause: Option<Box<Any + Send + 'static>>,
-}
-
-pub unsafe fn panic(data: Box<Any + Send + 'static>) -> ! {
-    let exception: Box<_> = box Exception {
-        uwe: uw::_Unwind_Exception {
-            exception_class: rust_exception_class(),
-            exception_cleanup: exception_cleanup,
-            private: [0; uw::unwinder_private_data_size],
-        },
-        cause: Some(data),
-    };
-    let exception_param = Box::into_raw(exception) as *mut uw::_Unwind_Exception;
-    let error = uw::_Unwind_RaiseException(exception_param);
-    rtabort!("Could not unwind stack, error = {}", error as isize);
-
-    extern fn exception_cleanup(_unwind_code: uw::_Unwind_Reason_Code,
-                                exception: *mut uw::_Unwind_Exception) {
-        unsafe {
-            let _: Box<Exception> = Box::from_raw(exception as *mut Exception);
-        }
-    }
-}
-
-pub fn payload() -> *mut u8 {
-    0 as *mut u8
-}
-
-pub unsafe fn cleanup(ptr: *mut u8) -> Box<Any + Send + 'static> {
-    let my_ep = ptr as *mut Exception;
-    let cause = (*my_ep).cause.take();
-    uw::_Unwind_DeleteException(ptr as *mut _);
-    cause.unwrap()
-}
-
-// Rust's exception class identifier.  This is used by personality routines to
-// determine whether the exception was thrown by their own runtime.
-fn rust_exception_class() -> uw::_Unwind_Exception_Class {
-    // M O Z \0  R U S T -- vendor, language
-    0x4d4f5a_00_52555354
-}
-
-// We could implement our personality routine in pure Rust, however exception
-// info decoding is tedious.  More importantly, personality routines have to
-// handle various platform quirks, which are not fun to maintain.  For this
-// reason, we attempt to reuse personality routine of the C language:
-// __gcc_personality_v0.
-//
-// Since C does not support exception catching, __gcc_personality_v0 simply
-// always returns _URC_CONTINUE_UNWIND in search phase, and always returns
-// _URC_INSTALL_CONTEXT (i.e. "invoke cleanup code") in cleanup phase.
-//
-// This is pretty close to Rust's exception handling approach, except that Rust
-// does have a single "catch-all" handler at the bottom of each thread's stack.
-// So we have two versions of the personality routine:
-// - rust_eh_personality, used by all cleanup landing pads, which never catches,
-//   so the behavior of __gcc_personality_v0 is perfectly adequate there, and
-// - rust_eh_personality_catch, used only by rust_try(), which always catches.
-//
-// See also: rustc_trans::trans::intrinsic::trans_gnu_try
-
-#[cfg(all(not(target_arch = "arm"),
-          not(all(windows, target_arch = "x86_64")),
-          not(test)))]
-pub mod eabi {
-    use sys_common::libunwind as uw;
-    use libc::c_int;
-
-    extern {
-        fn __gcc_personality_v0(version: c_int,
-                                actions: uw::_Unwind_Action,
-                                exception_class: uw::_Unwind_Exception_Class,
-                                ue_header: *mut uw::_Unwind_Exception,
-                                context: *mut uw::_Unwind_Context)
-            -> uw::_Unwind_Reason_Code;
-    }
-
-    #[lang = "eh_personality"]
-    #[no_mangle]
-    extern fn rust_eh_personality(
-        version: c_int,
-        actions: uw::_Unwind_Action,
-        exception_class: uw::_Unwind_Exception_Class,
-        ue_header: *mut uw::_Unwind_Exception,
-        context: *mut uw::_Unwind_Context
-    ) -> uw::_Unwind_Reason_Code
-    {
-        unsafe {
-            __gcc_personality_v0(version, actions, exception_class, ue_header,
-                                 context)
-        }
-    }
-
-    #[lang = "eh_personality_catch"]
-    #[no_mangle]
-    pub extern fn rust_eh_personality_catch(
-        version: c_int,
-        actions: uw::_Unwind_Action,
-        exception_class: uw::_Unwind_Exception_Class,
-        ue_header: *mut uw::_Unwind_Exception,
-        context: *mut uw::_Unwind_Context
-    ) -> uw::_Unwind_Reason_Code
-    {
-
-        if (actions as c_int & uw::_UA_SEARCH_PHASE as c_int) != 0 { // search phase
-            uw::_URC_HANDLER_FOUND // catch!
-        }
-        else { // cleanup phase
-            unsafe {
-                __gcc_personality_v0(version, actions, exception_class, ue_header,
-                                     context)
-            }
-        }
-    }
-}
-
-// iOS on armv7 is using SjLj exceptions and therefore requires to use
-// a specialized personality routine: __gcc_personality_sj0
-
-#[cfg(all(target_os = "ios", target_arch = "arm", not(test)))]
-pub mod eabi {
-    use sys_common::libunwind as uw;
-    use libc::c_int;
-
-    extern {
-        fn __gcc_personality_sj0(version: c_int,
-                                actions: uw::_Unwind_Action,
-                                exception_class: uw::_Unwind_Exception_Class,
-                                ue_header: *mut uw::_Unwind_Exception,
-                                context: *mut uw::_Unwind_Context)
-            -> uw::_Unwind_Reason_Code;
-    }
-
-    #[lang = "eh_personality"]
-    #[no_mangle]
-    pub extern fn rust_eh_personality(
-        version: c_int,
-        actions: uw::_Unwind_Action,
-        exception_class: uw::_Unwind_Exception_Class,
-        ue_header: *mut uw::_Unwind_Exception,
-        context: *mut uw::_Unwind_Context
-    ) -> uw::_Unwind_Reason_Code
-    {
-        unsafe {
-            __gcc_personality_sj0(version, actions, exception_class, ue_header,
-                                  context)
-        }
-    }
-
-    #[lang = "eh_personality_catch"]
-    #[no_mangle]
-    pub extern fn rust_eh_personality_catch(
-        version: c_int,
-        actions: uw::_Unwind_Action,
-        exception_class: uw::_Unwind_Exception_Class,
-        ue_header: *mut uw::_Unwind_Exception,
-        context: *mut uw::_Unwind_Context
-    ) -> uw::_Unwind_Reason_Code
-    {
-        if (actions as c_int & uw::_UA_SEARCH_PHASE as c_int) != 0 { // search phase
-            uw::_URC_HANDLER_FOUND // catch!
-        }
-        else { // cleanup phase
-            unsafe {
-                __gcc_personality_sj0(version, actions, exception_class, ue_header,
-                                      context)
-            }
-        }
-    }
-}
-
-
-// ARM EHABI uses a slightly different personality routine signature,
-// but otherwise works the same.
-#[cfg(all(target_arch = "arm", not(target_os = "ios"), not(test)))]
-pub mod eabi {
-    use sys_common::libunwind as uw;
-    use libc::c_int;
-
-    extern {
-        fn __gcc_personality_v0(state: uw::_Unwind_State,
-                                ue_header: *mut uw::_Unwind_Exception,
-                                context: *mut uw::_Unwind_Context)
-            -> uw::_Unwind_Reason_Code;
-    }
-
-    #[lang = "eh_personality"]
-    #[no_mangle]
-    extern fn rust_eh_personality(
-        state: uw::_Unwind_State,
-        ue_header: *mut uw::_Unwind_Exception,
-        context: *mut uw::_Unwind_Context
-    ) -> uw::_Unwind_Reason_Code
-    {
-        unsafe {
-            __gcc_personality_v0(state, ue_header, context)
-        }
-    }
-
-    #[lang = "eh_personality_catch"]
-    #[no_mangle]
-    pub extern fn rust_eh_personality_catch(
-        state: uw::_Unwind_State,
-        ue_header: *mut uw::_Unwind_Exception,
-        context: *mut uw::_Unwind_Context
-    ) -> uw::_Unwind_Reason_Code
-    {
-        // Backtraces on ARM will call the personality routine with
-        // state == _US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND. In those cases
-        // we want to continue unwinding the stack, otherwise all our backtraces
-        // would end at __rust_try.
-        if (state as c_int & uw::_US_ACTION_MASK as c_int)
-                           == uw::_US_VIRTUAL_UNWIND_FRAME as c_int
-               && (state as c_int & uw::_US_FORCE_UNWIND as c_int) == 0 { // search phase
-            uw::_URC_HANDLER_FOUND // catch!
-        }
-        else { // cleanup phase
-            unsafe {
-                __gcc_personality_v0(state, ue_header, context)
-            }
-        }
-    }
-}
-
-// See docs in the `unwind` module.
-#[cfg(all(target_os="windows", target_arch = "x86", target_env="gnu", not(test)))]
-#[lang = "eh_unwind_resume"]
-#[unwind]
-unsafe extern fn rust_eh_unwind_resume(panic_ctx: *mut u8) -> ! {
-    uw::_Unwind_Resume(panic_ctx as *mut uw::_Unwind_Exception);
-}
-
-#[cfg(all(target_os="windows", target_arch = "x86", target_env="gnu"))]
-pub mod eh_frame_registry {
-    // The implementation of stack unwinding is (for now) deferred to libgcc_eh, however Rust
-    // crates use these Rust-specific entry points to avoid potential clashes with GCC runtime.
-    // See also: rtbegin.rs, `unwind` module.
-
-    #[link(name = "gcc_eh")]
-    #[cfg(not(cargobuild))]
-    extern {}
-
-    extern {
-        fn __register_frame_info(eh_frame_begin: *const u8, object: *mut u8);
-        fn __deregister_frame_info(eh_frame_begin: *const u8, object: *mut u8);
-    }
-    #[cfg(not(test))]
-    #[no_mangle]
-    #[unstable(feature = "libstd_sys_internals", issue = "0")]
-    pub unsafe extern fn rust_eh_register_frames(eh_frame_begin: *const u8,
-                                                 object: *mut u8) {
-        __register_frame_info(eh_frame_begin, object);
-    }
-    #[cfg(not(test))]
-    #[no_mangle]
-    #[unstable(feature = "libstd_sys_internals", issue = "0")]
-    pub  unsafe extern fn rust_eh_unregister_frames(eh_frame_begin: *const u8,
-                                                   object: *mut u8) {
-        __deregister_frame_info(eh_frame_begin, object);
-    }
-}
diff --git a/src/libstd/sys/common/unwind/mod.rs b/src/libstd/sys/common/unwind/mod.rs
deleted file mode 100644
index 527c2e63030..00000000000
--- a/src/libstd/sys/common/unwind/mod.rs
+++ /dev/null
@@ -1,241 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! Implementation of Rust stack unwinding
-//!
-//! For background on exception handling and stack unwinding please see
-//! "Exception Handling in LLVM" (llvm.org/docs/ExceptionHandling.html) and
-//! documents linked from it.
-//! These are also good reads:
-//!     http://mentorembedded.github.io/cxx-abi/abi-eh.html
-//!     http://monoinfinito.wordpress.com/series/exception-handling-in-c/
-//!     http://www.airs.com/blog/index.php?s=exception+frames
-//!
-//! ## A brief summary
-//!
-//! Exception handling happens in two phases: a search phase and a cleanup phase.
-//!
-//! In both phases the unwinder walks stack frames from top to bottom using
-//! information from the stack frame unwind sections of the current process's
-//! modules ("module" here refers to an OS module, i.e. an executable or a
-//! dynamic library).
-//!
-//! For each stack frame, it invokes the associated "personality routine", whose
-//! address is also stored in the unwind info section.
-//!
-//! In the search phase, the job of a personality routine is to examine exception
-//! object being thrown, and to decide whether it should be caught at that stack
-//! frame.  Once the handler frame has been identified, cleanup phase begins.
-//!
-//! In the cleanup phase, the unwinder invokes each personality routine again.
-//! This time it decides which (if any) cleanup code needs to be run for
-//! the current stack frame.  If so, the control is transferred to a special branch
-//! in the function body, the "landing pad", which invokes destructors, frees memory,
-//! etc.  At the end of the landing pad, control is transferred back to the unwinder
-//! and unwinding resumes.
-//!
-//! Once stack has been unwound down to the handler frame level, unwinding stops
-//! and the last personality routine transfers control to the catch block.
-//!
-//! ## `eh_personality` and `eh_unwind_resume`
-//!
-//! These language items are used by the compiler when generating unwind info.
-//! The first one is the personality routine described above.  The second one
-//! allows compilation target to customize the process of resuming unwind at the
-//! end of the landing pads.  `eh_unwind_resume` is used only if `custom_unwind_resume`
-//! flag in the target options is set.
-//!
-//! ## Frame unwind info registration
-//!
-//! Each module's image contains a frame unwind info section (usually ".eh_frame").
-//! When a module is loaded/unloaded into the process, the unwinder must be informed
-//! about the location of this section in memory. The methods of achieving that vary
-//! by the platform.
-//! On some (e.g. Linux), the unwinder can discover unwind info sections on its own
-//! (by dynamically enumerating currently loaded modules via the dl_iterate_phdr() API
-//! and finding their ".eh_frame" sections);
-//! Others, like Windows, require modules to actively register their unwind info
-//! sections via unwinder API (see `rust_eh_register_frames`/`rust_eh_unregister_frames`).
-
-#![allow(dead_code)]
-#![allow(unused_imports)]
-
-use prelude::v1::*;
-
-use any::Any;
-use boxed;
-use cmp;
-use panicking::{self,PANIC_COUNT};
-use fmt;
-use intrinsics;
-use mem;
-use sync::atomic::{self, Ordering};
-use sys_common::mutex::Mutex;
-
-// The actual unwinding implementation is cfg'd here, and we've got two current
-// implementations. One goes through SEH on Windows and the other goes through
-// libgcc via the libunwind-like API.
-
-// *-pc-windows-msvc
-#[cfg(target_env = "msvc")]
-#[path = "seh.rs"] #[doc(hidden)]
-pub mod imp;
-
-// x86_64-pc-windows-gnu
-#[cfg(all(windows, target_arch = "x86_64", target_env = "gnu"))]
-#[path = "seh64_gnu.rs"] #[doc(hidden)]
-pub mod imp;
-
-// i686-pc-windows-gnu and all others
-#[cfg(any(unix, all(windows, target_arch = "x86", target_env = "gnu")))]
-#[path = "gcc.rs"] #[doc(hidden)]
-pub mod imp;
-
-/// Invoke a closure, capturing the cause of panic if one occurs.
-///
-/// This function will return `Ok(())` if the closure did not panic, and will
-/// return `Err(cause)` if the closure panics. The `cause` returned is the
-/// object with which panic was originally invoked.
-///
-/// This function also is unsafe for a variety of reasons:
-///
-/// * This is not safe to call in a nested fashion. The unwinding
-///   interface for Rust is designed to have at most one try/catch block per
-///   thread, not multiple. No runtime checking is currently performed to uphold
-///   this invariant, so this function is not safe. A nested try/catch block
-///   may result in corruption of the outer try/catch block's state, especially
-///   if this is used within a thread itself.
-///
-/// * It is not sound to trigger unwinding while already unwinding. Rust threads
-///   have runtime checks in place to ensure this invariant, but it is not
-///   guaranteed that a rust thread is in place when invoking this function.
-///   Unwinding twice can lead to resource leaks where some destructors are not
-///   run.
-pub unsafe fn try<F: FnOnce()>(f: F) -> Result<(), Box<Any + Send>> {
-    let mut f = Some(f);
-    return inner_try(try_fn::<F>, &mut f as *mut _ as *mut u8);
-
-    fn try_fn<F: FnOnce()>(opt_closure: *mut u8) {
-        let opt_closure = opt_closure as *mut Option<F>;
-        unsafe { (*opt_closure).take().unwrap()(); }
-    }
-}
-
-unsafe fn inner_try(f: fn(*mut u8), data: *mut u8)
-                    -> Result<(), Box<Any + Send>> {
-    PANIC_COUNT.with(|s| {
-        let prev = s.get();
-        s.set(0);
-
-        // The "payload" here is a platform-specific region of memory which is
-        // used to transmit information about the exception being thrown from
-        // the point-of-throw back to this location.
-        //
-        // A pointer to this data is passed to the `try` intrinsic itself,
-        // allowing this function, the `try` intrinsic, imp::payload(), and
-        // imp::cleanup() to all work in concert to transmit this information.
-        //
-        // More information about what this pointer actually is can be found in
-        // each implementation as well as browsing the compiler source itself.
-        let mut payload = imp::payload();
-        let r = intrinsics::try(f, data, &mut payload as *mut _ as *mut _);
-        s.set(prev);
-        if r == 0 {
-            Ok(())
-        } else {
-            Err(imp::cleanup(payload))
-        }
-    })
-}
-
-/// Determines whether the current thread is unwinding because of panic.
-pub fn panicking() -> bool {
-    PANIC_COUNT.with(|s| s.get() != 0)
-}
-
-// An uninlined, unmangled function upon which to slap yer breakpoints
-#[inline(never)]
-#[no_mangle]
-#[allow(private_no_mangle_fns)]
-pub fn rust_panic(cause: Box<Any + Send + 'static>) -> ! {
-    unsafe {
-        imp::panic(cause)
-    }
-}
-
-#[cfg(not(test))]
-/// Entry point of panic from the libcore crate.
-#[lang = "panic_fmt"]
-#[unwind]
-pub extern fn rust_begin_unwind(msg: fmt::Arguments,
-                                file: &'static str, line: u32) -> ! {
-    begin_unwind_fmt(msg, &(file, line))
-}
-
-/// The entry point for unwinding with a formatted message.
-///
-/// This is designed to reduce the amount of code required at the call
-/// site as much as possible (so that `panic!()` has as low an impact
-/// on (e.g.) the inlining of other functions as possible), by moving
-/// the actual formatting into this shared place.
-#[unstable(feature = "libstd_sys_internals",
-           reason = "used by the panic! macro",
-           issue = "0")]
-#[inline(never)] #[cold]
-pub fn begin_unwind_fmt(msg: fmt::Arguments, file_line: &(&'static str, u32)) -> ! {
-    use fmt::Write;
-
-    // We do two allocations here, unfortunately. But (a) they're
-    // required with the current scheme, and (b) we don't handle
-    // panic + OOM properly anyway (see comment in begin_unwind
-    // below).
-
-    let mut s = String::new();
-    let _ = s.write_fmt(msg);
-    begin_unwind_inner(Box::new(s), file_line)
-}
-
-/// This is the entry point of unwinding for panic!() and assert!().
-#[unstable(feature = "libstd_sys_internals",
-           reason = "used by the panic! macro",
-           issue = "0")]
-#[inline(never)] #[cold] // avoid code bloat at the call sites as much as possible
-pub fn begin_unwind<M: Any + Send>(msg: M, file_line: &(&'static str, u32)) -> ! {
-    // Note that this should be the only allocation performed in this code path.
-    // Currently this means that panic!() on OOM will invoke this code path,
-    // but then again we're not really ready for panic on OOM anyway. If
-    // we do start doing this, then we should propagate this allocation to
-    // be performed in the parent of this thread instead of the thread that's
-    // panicking.
-
-    // see below for why we do the `Any` coercion here.
-    begin_unwind_inner(Box::new(msg), file_line)
-}
-
-/// The core of the unwinding.
-///
-/// This is non-generic to avoid instantiation bloat in other crates
-/// (which makes compilation of small crates noticeably slower). (Note:
-/// we need the `Any` object anyway, we're not just creating it to
-/// avoid being generic.)
-///
-/// Doing this split took the LLVM IR line counts of `fn main() { panic!()
-/// }` from ~1900/3700 (-O/no opts) to 180/590.
-#[inline(never)] #[cold] // this is the slow path, please never inline this
-fn begin_unwind_inner(msg: Box<Any + Send>,
-                      file_line: &(&'static str, u32)) -> ! {
-    let (file, line) = *file_line;
-
-    // First, invoke the default panic handler.
-    panicking::on_panic(&*msg, file, line);
-
-    // Finally, perform the unwinding.
-    rust_panic(msg);
-}
diff --git a/src/libstd/sys/common/unwind/seh.rs b/src/libstd/sys/common/unwind/seh.rs
deleted file mode 100644
index 94da42f0092..00000000000
--- a/src/libstd/sys/common/unwind/seh.rs
+++ /dev/null
@@ -1,153 +0,0 @@
-// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! Windows SEH
-//!
-//! On Windows (currently only on MSVC), the default exception handling
-//! mechanism is Structured Exception Handling (SEH). This is quite different
-//! than Dwarf-based exception handling (e.g. what other unix platforms use) in
-//! terms of compiler internals, so LLVM is required to have a good deal of
-//! extra support for SEH.
-//!
-//! In a nutshell, what happens here is:
-//!
-//! 1. The `panic` function calls the standard Windows function `RaiseException`
-//!    with a Rust-specific code, triggering the unwinding process.
-//! 2. All landing pads generated by the compiler use the personality function
-//!    `__C_specific_handler` on 64-bit and `__except_handler3` on 32-bit,
-//!    functions in the CRT, and the unwinding code in Windows will use this
-//!    personality function to execute all cleanup code on the stack.
-//! 3. All compiler-generated calls to `invoke` have a landing pad set as a
-//!    `cleanuppad` LLVM instruction, which indicates the start of the cleanup
-//!    routine. The personality (in step 2, defined in the CRT) is responsible
-//!    for running the cleanup routines.
-//! 4. Eventually the "catch" code in the `try` intrinsic (generated by the
-//!    compiler) is executed, which will ensure that the exception being caught
-//!    is indeed a Rust exception, indicating that control should come back to
-//!    Rust. This is done via a `catchswitch` plus a `catchpad` instruction in
-//!    LLVM IR terms, finally returning normal control to the program with a
-//!    `catchret` instruction. The `try` intrinsic uses a filter function to
-//!    detect what kind of exception is being thrown, and this detection is
-//!    implemented as the msvc_try_filter language item below.
-//!
-//! Some specific differences from the gcc-based exception handling are:
-//!
-//! * Rust has no custom personality function, it is instead *always*
-//!   __C_specific_handler or __except_handler3, so the filtering is done in a
-//!   C++-like manner instead of in the personality function itself. Note that
-//!   the precise codegen for this was lifted from an LLVM test case for SEH
-//!   (this is the `__rust_try_filter` function below).
-//! * We've got some data to transmit across the unwinding boundary,
-//!   specifically a `Box<Any + Send + 'static>`. Like with Dwarf exceptions
-//!   these two pointers are stored as a payload in the exception itself. On
-//!   MSVC, however, there's no need for an extra allocation because the call
-//!   stack is preserved while filter functions are being executed. This means
-//!   that the pointers are passed directly to `RaiseException` which are then
-//!   recovered in the filter function to be written to the stack frame of the
-//!   `try` intrinsic.
-//!
-//! [win64]: http://msdn.microsoft.com/en-us/library/1eyas8tf.aspx
-//! [llvm]: http://llvm.org/docs/ExceptionHandling.html#background-on-windows-exceptions
-
-use sys::c;
-
-// A code which indicates panics that originate from Rust. Note that some of the
-// upper bits are used by the system so we just set them to 0 and ignore them.
-//                           0x 0 R S T
-const RUST_PANIC: c::DWORD = 0x00525354;
-
-pub use self::imp::*;
-
-mod imp {
-    use prelude::v1::*;
-
-    use any::Any;
-    use mem;
-    use raw;
-    use super::RUST_PANIC;
-    use sys::c;
-
-    pub unsafe fn panic(data: Box<Any + Send + 'static>) -> ! {
-        // As mentioned above, the call stack here is preserved while the filter
-        // functions are running, so it's ok to pass stack-local arrays into
-        // `RaiseException`.
-        //
-        // The two pointers of the `data` trait object are written to the stack,
-        // passed to `RaiseException`, and they're later extracted by the filter
-        // function below in the "custom exception information" section of the
-        // `EXCEPTION_RECORD` type.
-        let ptrs = mem::transmute::<_, raw::TraitObject>(data);
-        let ptrs = [ptrs.data, ptrs.vtable];
-        c::RaiseException(RUST_PANIC, 0, 2, ptrs.as_ptr() as *mut _);
-        rtabort!("could not unwind stack");
-    }
-
-    pub fn payload() -> [usize; 2] {
-        [0; 2]
-    }
-
-    pub unsafe fn cleanup(payload: [usize; 2]) -> Box<Any + Send + 'static> {
-        mem::transmute(raw::TraitObject {
-            data: payload[0] as *mut _,
-            vtable: payload[1] as *mut _,
-        })
-    }
-
-    // This is quite a special function, and it's not literally passed in as the
-    // filter function for the `catchpad` of the `try` intrinsic. The compiler
-    // actually generates its own filter function wrapper which will delegate to
-    // this for the actual execution logic for whether the exception should be
-    // caught. The reasons for this are:
-    //
-    // * Each architecture has a slightly different ABI for the filter function
-    //   here. For example on x86 there are no arguments but on x86_64 there are
-    //   two.
-    // * This function needs access to the stack frame of the `try` intrinsic
-    //   which is using this filter as a catch pad. This is because the payload
-    //   of this exception, `Box<Any>`, needs to be transmitted to that
-    //   location.
-    //
-    // Both of these differences end up using a ton of weird llvm-specific
-    // intrinsics, so it's actually pretty difficult to express the entire
-    // filter function in Rust itself. As a compromise, the compiler takes care
-    // of all the weird LLVM-specific and platform-specific stuff, getting to
-    // the point where this function makes the actual decision about what to
-    // catch given two parameters.
-    //
-    // The first parameter is `*mut EXCEPTION_POINTERS` which is some contextual
-    // information about the exception being filtered, and the second pointer is
-    // `*mut *mut [usize; 2]` (the payload here). This value points directly
-    // into the stack frame of the `try` intrinsic itself, and we use it to copy
-    // information from the exception onto the stack.
-    #[lang = "msvc_try_filter"]
-    #[cfg(not(test))]
-    unsafe extern fn __rust_try_filter(eh_ptrs: *mut u8,
-                                       payload: *mut u8) -> i32 {
-        let eh_ptrs = eh_ptrs as *mut c::EXCEPTION_POINTERS;
-        let payload = payload as *mut *mut [usize; 2];
-        let record = &*(*eh_ptrs).ExceptionRecord;
-        if record.ExceptionCode != RUST_PANIC {
-            return 0
-        }
-        (**payload)[0] = record.ExceptionInformation[0] as usize;
-        (**payload)[1] = record.ExceptionInformation[1] as usize;
-        return 1
-    }
-}
-
-// This is required by the compiler to exist (e.g. it's a lang item), but
-// it's never actually called by the compiler because __C_specific_handler
-// or _except_handler3 is the personality function that is always used.
-// Hence this is just an aborting stub.
-#[lang = "eh_personality"]
-#[cfg(not(test))]
-fn rust_eh_personality() {
-    unsafe { ::intrinsics::abort() }
-}
diff --git a/src/libstd/sys/common/unwind/seh64_gnu.rs b/src/libstd/sys/common/unwind/seh64_gnu.rs
deleted file mode 100644
index 57281d67ebb..00000000000
--- a/src/libstd/sys/common/unwind/seh64_gnu.rs
+++ /dev/null
@@ -1,145 +0,0 @@
-// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! Unwinding implementation of top of native Win64 SEH,
-//! however the unwind handler data (aka LSDA) uses GCC-compatible encoding.
-
-#![allow(bad_style)]
-#![allow(private_no_mangle_fns)]
-
-use prelude::v1::*;
-
-use any::Any;
-use sys_common::dwarf::eh;
-use core::mem;
-use core::ptr;
-use sys::c;
-
-// Define our exception codes:
-// according to http://msdn.microsoft.com/en-us/library/het71c37(v=VS.80).aspx,
-//    [31:30] = 3 (error), 2 (warning), 1 (info), 0 (success)
-//    [29]    = 1 (user-defined)
-//    [28]    = 0 (reserved)
-// we define bits:
-//    [24:27] = type
-//    [0:23]  = magic
-const ETYPE: c::DWORD = 0b1110_u32 << 28;
-const MAGIC: c::DWORD = 0x525354; // "RST"
-
-const RUST_PANIC: c::DWORD  = ETYPE | (1 << 24) | MAGIC;
-
-#[repr(C)]
-struct PanicData {
-    data: Box<Any + Send + 'static>
-}
-
-pub unsafe fn panic(data: Box<Any + Send + 'static>) -> ! {
-    let panic_ctx = Box::new(PanicData { data: data });
-    let params = [Box::into_raw(panic_ctx) as c::ULONG_PTR];
-    c::RaiseException(RUST_PANIC,
-                      c::EXCEPTION_NONCONTINUABLE,
-                      params.len() as c::DWORD,
-                      &params as *const c::ULONG_PTR);
-    rtabort!("could not unwind stack");
-}
-
-pub fn payload() -> *mut u8 {
-    0 as *mut u8
-}
-
-pub unsafe fn cleanup(ptr: *mut u8) -> Box<Any + Send + 'static> {
-    let panic_ctx = Box::from_raw(ptr as *mut PanicData);
-    return panic_ctx.data;
-}
-
-// SEH doesn't support resuming unwinds after calling a landing pad like
-// libunwind does. For this reason, MSVC compiler outlines landing pads into
-// separate functions that can be called directly from the personality function
-// but are nevertheless able to find and modify stack frame of the "parent"
-// function.
-//
-// Since this cannot be done with libdwarf-style landing pads,
-// rust_eh_personality instead catches RUST_PANICs, runs the landing pad, then
-// reraises the exception.
-//
-// Note that it makes certain assumptions about the exception:
-//
-// 1. That RUST_PANIC is non-continuable, so no lower stack frame may choose to
-//    resume execution.
-// 2. That the first parameter of the exception is a pointer to an extra data
-//    area (PanicData).
-// Since these assumptions do not generally hold true for foreign exceptions
-// (system faults, C++ exceptions, etc), we make no attempt to invoke our
-// landing pads (and, thus, destructors!) for anything other than RUST_PANICs.
-// This is considered acceptable, because the behavior of throwing exceptions
-// through a C ABI boundary is undefined.
-
-#[lang = "eh_personality_catch"]
-#[cfg(not(test))]
-unsafe extern fn rust_eh_personality_catch(
-    exceptionRecord: *mut c::EXCEPTION_RECORD,
-    establisherFrame: c::LPVOID,
-    contextRecord: *mut c::CONTEXT,
-    dispatcherContext: *mut c::DISPATCHER_CONTEXT
-) -> c::EXCEPTION_DISPOSITION
-{
-    rust_eh_personality(exceptionRecord, establisherFrame,
-                        contextRecord, dispatcherContext)
-}
-
-#[lang = "eh_personality"]
-#[cfg(not(test))]
-unsafe extern fn rust_eh_personality(
-    exceptionRecord: *mut c::EXCEPTION_RECORD,
-    establisherFrame: c::LPVOID,
-    contextRecord: *mut c::CONTEXT,
-    dispatcherContext: *mut c::DISPATCHER_CONTEXT
-) -> c::EXCEPTION_DISPOSITION
-{
-    let er = &*exceptionRecord;
-    let dc = &*dispatcherContext;
-
-    if er.ExceptionFlags & c::EXCEPTION_UNWIND == 0 { // we are in the dispatch phase
-        if er.ExceptionCode == RUST_PANIC {
-            if let Some(lpad) = find_landing_pad(dc) {
-                c::RtlUnwindEx(establisherFrame,
-                               lpad as c::LPVOID,
-                               exceptionRecord,
-                               er.ExceptionInformation[0] as c::LPVOID, // pointer to PanicData
-                               contextRecord,
-                               dc.HistoryTable);
-                rtabort!("could not unwind");
-            }
-        }
-    }
-    c::ExceptionContinueSearch
-}
-
-#[cfg(not(test))]
-#[lang = "eh_unwind_resume"]
-#[unwind]
-unsafe extern fn rust_eh_unwind_resume(panic_ctx: c::LPVOID) -> ! {
-    let params = [panic_ctx as c::ULONG_PTR];
-    c::RaiseException(RUST_PANIC,
-                      c::EXCEPTION_NONCONTINUABLE,
-                      params.len() as c::DWORD,
-                      &params as *const c::ULONG_PTR);
-    rtabort!("could not resume unwind");
-}
-
-unsafe fn find_landing_pad(dc: &c::DISPATCHER_CONTEXT) -> Option<usize> {
-    let eh_ctx = eh::EHContext {
-        ip: dc.ControlPc as usize,
-        func_start: dc.ImageBase as usize + (*dc.FunctionEntry).BeginAddress as usize,
-        text_start: dc.ImageBase as usize,
-        data_start: 0
-    };
-    eh::find_landing_pad(dc.HandlerData, &eh_ctx)
-}