Auto merge of #35032 - vadimcn:rusty-ehabi, r=alexcrichton

Implement ARM personality routine in Rust.

Remove the `eh_personality_catch` lang item.
Use a simplified version of `cfg_if!` in libunwind.

Closes #34786

5 files changed, 314 insertions, 270 deletions

diff --git a/src/libpanic_unwind/gcc.rs b/src/libpanic_unwind/gcc.rs
index cdf772ad3b8..fdae8f69a9c 100644
--- a/src/libpanic_unwind/gcc.rs
+++ b/src/libpanic_unwind/gcc.rs
@@ -61,6 +61,8 @@ use core::ptr;
 use alloc::boxed::Box;
 
 use unwind as uw;
+use libc::{c_int, uintptr_t};
+use dwarf::eh::{self, EHContext, EHAction};
 
 #[repr(C)]
 struct Exception {
@@ -106,139 +108,184 @@ fn rust_exception_class() -> uw::_Unwind_Exception_Class {
     0x4d4f5a_00_52555354
 }
 
-// All targets, except ARM which uses a slightly different ABI (however, iOS goes here as it uses
-// SjLj unwinding).  Also, 64-bit Windows implementation lives in seh64_gnu.rs
-#[cfg(all(any(target_os = "ios", not(target_arch = "arm"))))]
-pub mod eabi {
-    use unwind as uw;
-    use libc::{c_int, uintptr_t};
-    use dwarf::eh::{EHContext, EHAction, find_eh_action};
 
-    // Register ids were lifted from LLVM's TargetLowering::getExceptionPointerRegister()
-    // and TargetLowering::getExceptionSelectorRegister() for each architecture,
-    // then mapped to DWARF register numbers via register definition tables
-    // (typically <arch>RegisterInfo.td, search for "DwarfRegNum").
-    // See also http://llvm.org/docs/WritingAnLLVMBackend.html#defining-a-register.
+// Register ids were lifted from LLVM's TargetLowering::getExceptionPointerRegister()
+// and TargetLowering::getExceptionSelectorRegister() for each architecture,
+// then mapped to DWARF register numbers via register definition tables
+// (typically <arch>RegisterInfo.td, search for "DwarfRegNum").
+// See also http://llvm.org/docs/WritingAnLLVMBackend.html#defining-a-register.
 
-    #[cfg(target_arch = "x86")]
-    const UNWIND_DATA_REG: (i32, i32) = (0, 2); // EAX, EDX
+#[cfg(target_arch = "x86")]
+const UNWIND_DATA_REG: (i32, i32) = (0, 2); // EAX, EDX
 
-    #[cfg(target_arch = "x86_64")]
-    const UNWIND_DATA_REG: (i32, i32) = (0, 1); // RAX, RDX
+#[cfg(target_arch = "x86_64")]
+const UNWIND_DATA_REG: (i32, i32) = (0, 1); // RAX, RDX
 
-    #[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
-    const UNWIND_DATA_REG: (i32, i32) = (0, 1); // R0, R1 / X0, X1
+#[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
+const UNWIND_DATA_REG: (i32, i32) = (0, 1); // R0, R1 / X0, X1
 
-    #[cfg(any(target_arch = "mips", target_arch = "mipsel"))]
-    const UNWIND_DATA_REG: (i32, i32) = (4, 5); // A0, A1
+#[cfg(any(target_arch = "mips", target_arch = "mipsel"))]
+const UNWIND_DATA_REG: (i32, i32) = (4, 5); // A0, A1
 
-    #[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
-    const UNWIND_DATA_REG: (i32, i32) = (3, 4); // R3, R4 / X3, X4
+#[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
+const UNWIND_DATA_REG: (i32, i32) = (3, 4); // R3, R4 / X3, X4
 
-    // Based on GCC's C and C++ personality routines.  For reference, see:
-    // https://github.com/gcc-mirror/gcc/blob/master/libstdc++-v3/libsupc++/eh_personality.cc
-    // https://github.com/gcc-mirror/gcc/blob/trunk/libgcc/unwind-c.c
-    #[lang = "eh_personality"]
-    #[no_mangle]
-    #[allow(unused)]
-    unsafe extern "C" fn rust_eh_personality(version: c_int,
-                                             actions: uw::_Unwind_Action,
-                                             exception_class: uw::_Unwind_Exception_Class,
-                                             exception_object: *mut uw::_Unwind_Exception,
-                                             context: *mut uw::_Unwind_Context)
-                                             -> uw::_Unwind_Reason_Code {
-        if version != 1 {
-            return uw::_URC_FATAL_PHASE1_ERROR;
-        }
-        let lsda = uw::_Unwind_GetLanguageSpecificData(context) as *const u8;
-        let mut ip_before_instr: c_int = 0;
-        let ip = uw::_Unwind_GetIPInfo(context, &mut ip_before_instr);
-        let eh_context = EHContext {
-            // The return address points 1 byte past the call instruction,
-            // which could be in the next IP range in LSDA range table.
-            ip: if ip_before_instr != 0 { ip } else { ip - 1 },
-            func_start: uw::_Unwind_GetRegionStart(context),
-            get_text_start: &|| uw::_Unwind_GetTextRelBase(context),
-            get_data_start: &|| uw::_Unwind_GetDataRelBase(context),
-        };
-        let eh_action = find_eh_action(lsda, &eh_context);
+// The following code is based on GCC's C and C++ personality routines.  For reference, see:
+// https://github.com/gcc-mirror/gcc/blob/master/libstdc++-v3/libsupc++/eh_personality.cc
+// https://github.com/gcc-mirror/gcc/blob/trunk/libgcc/unwind-c.c
 
-        if actions as i32 & uw::_UA_SEARCH_PHASE as i32 != 0 {
-            match eh_action {
-                EHAction::None | EHAction::Cleanup(_) => return uw::_URC_CONTINUE_UNWIND,
-                EHAction::Catch(_) => return uw::_URC_HANDLER_FOUND,
-                EHAction::Terminate => return uw::_URC_FATAL_PHASE1_ERROR,
-            }
-        } else {
-            match eh_action {
-                EHAction::None => return uw::_URC_CONTINUE_UNWIND,
-                EHAction::Cleanup(lpad) | EHAction::Catch(lpad) => {
-                    uw::_Unwind_SetGR(context, UNWIND_DATA_REG.0, exception_object as uintptr_t);
-                    uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, 0);
-                    uw::_Unwind_SetIP(context, lpad);
-                    return uw::_URC_INSTALL_CONTEXT;
-                }
-                EHAction::Terminate => return uw::_URC_FATAL_PHASE2_ERROR,
+// The personality routine for most of our targets, except ARM, which has a slightly different ABI
+// (however, iOS goes here as it uses SjLj unwinding).  Also, the 64-bit Windows implementation
+// lives in seh64_gnu.rs
+#[cfg(all(any(target_os = "ios", not(target_arch = "arm"))))]
+#[lang = "eh_personality"]
+#[no_mangle]
+#[allow(unused)]
+unsafe extern "C" fn rust_eh_personality(version: c_int,
+                                         actions: uw::_Unwind_Action,
+                                         exception_class: uw::_Unwind_Exception_Class,
+                                         exception_object: *mut uw::_Unwind_Exception,
+                                         context: *mut uw::_Unwind_Context)
+                                         -> uw::_Unwind_Reason_Code {
+    if version != 1 {
+        return uw::_URC_FATAL_PHASE1_ERROR;
+    }
+    let eh_action = find_eh_action(context);
+    if actions as i32 & uw::_UA_SEARCH_PHASE as i32 != 0 {
+        match eh_action {
+            EHAction::None | EHAction::Cleanup(_) => return uw::_URC_CONTINUE_UNWIND,
+            EHAction::Catch(_) => return uw::_URC_HANDLER_FOUND,
+            EHAction::Terminate => return uw::_URC_FATAL_PHASE1_ERROR,
+        }
+    } else {
+        match eh_action {
+            EHAction::None => return uw::_URC_CONTINUE_UNWIND,
+            EHAction::Cleanup(lpad) | EHAction::Catch(lpad) => {
+                uw::_Unwind_SetGR(context, UNWIND_DATA_REG.0, exception_object as uintptr_t);
+                uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, 0);
+                uw::_Unwind_SetIP(context, lpad);
+                return uw::_URC_INSTALL_CONTEXT;
             }
+            EHAction::Terminate => return uw::_URC_FATAL_PHASE2_ERROR,
         }
     }
-
-    #[cfg(stage0)]
-    #[lang = "eh_personality_catch"]
-    #[no_mangle]
-    pub unsafe extern "C" 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 {
-        rust_eh_personality(version, actions, exception_class, ue_header, context)
-    }
 }
 
-// ARM EHABI uses a slightly different personality routine signature,
-// but otherwise works the same.
+// ARM EHABI personality routine.
+// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf
 #[cfg(all(target_arch = "arm", not(target_os = "ios")))]
-pub mod eabi {
-    use unwind as uw;
-    use libc::c_int;
+#[lang = "eh_personality"]
+#[no_mangle]
+unsafe extern "C" fn rust_eh_personality(state: uw::_Unwind_State,
+                                         exception_object: *mut uw::_Unwind_Exception,
+                                         context: *mut uw::_Unwind_Context)
+                                        -> uw::_Unwind_Reason_Code {
+    let state = state as c_int;
+    let action = state & uw::_US_ACTION_MASK as c_int;
+    let search_phase = if action == uw::_US_VIRTUAL_UNWIND_FRAME as c_int {
+        // 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 & uw::_US_FORCE_UNWIND as c_int != 0 {
+            return continue_unwind(exception_object, context)
+        }
+        true
+    } else if action == uw::_US_UNWIND_FRAME_STARTING as c_int {
+        false
+    } else if action == uw::_US_UNWIND_FRAME_RESUME as c_int {
+        return continue_unwind(exception_object, context);
+    } else {
+        return uw::_URC_FAILURE;
+    };
 
-    extern "C" {
-        fn __gcc_personality_v0(state: uw::_Unwind_State,
-                                ue_header: *mut uw::_Unwind_Exception,
-                                context: *mut uw::_Unwind_Context)
-                                -> uw::_Unwind_Reason_Code;
-    }
+    // The DWARF unwinder assumes that _Unwind_Context holds things like the function
+    // and LSDA pointers, however ARM EHABI places them into the exception object.
+    // To preserve signatures of functions like _Unwind_GetLanguageSpecificData(), which
+    // take only the context pointer, GCC personality routines stash a pointer to exception_object
+    // in the context, using location reserved for ARM's "scratch register" (r12).
+    uw::_Unwind_SetGR(context, uw::UNWIND_POINTER_REG, exception_object as uw::_Unwind_Ptr);
+    // ...A more principled approach would be to provide the full definition of ARM's
+    // _Unwind_Context in our libunwind bindings and fetch the required data from there directly,
+    // bypassing DWARF compatibility functions.
 
-    #[lang = "eh_personality"]
-    #[no_mangle]
-    extern "C" 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) }
+    let eh_action = find_eh_action(context);
+    if search_phase {
+        match eh_action {
+            EHAction::None |
+            EHAction::Cleanup(_) => return continue_unwind(exception_object, context),
+            EHAction::Catch(_) => return uw::_URC_HANDLER_FOUND,
+            EHAction::Terminate => return uw::_URC_FAILURE,
+        }
+    } else {
+        match eh_action {
+            EHAction::None => return continue_unwind(exception_object, context),
+            EHAction::Cleanup(lpad) | EHAction::Catch(lpad) => {
+                uw::_Unwind_SetGR(context, UNWIND_DATA_REG.0, exception_object as uintptr_t);
+                uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, 0);
+                uw::_Unwind_SetIP(context, lpad);
+                return uw::_URC_INSTALL_CONTEXT;
+            }
+            EHAction::Terminate => return uw::_URC_FAILURE,
+        }
     }
 
-    #[lang = "eh_personality_catch"]
-    #[no_mangle]
-    pub extern "C" 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!
+    // On ARM EHABI the personality routine is responsible for actually
+    // unwinding a single stack frame before returning (ARM EHABI Sec. 6.1).
+    unsafe fn continue_unwind(exception_object: *mut uw::_Unwind_Exception,
+                              context: *mut uw::_Unwind_Context)
+                              -> uw::_Unwind_Reason_Code {
+        if __gnu_unwind_frame(exception_object, context) == uw::_URC_NO_REASON {
+            uw::_URC_CONTINUE_UNWIND
         } else {
-            // cleanup phase
-            unsafe { __gcc_personality_v0(state, ue_header, context) }
+            uw::_URC_FAILURE
         }
     }
+    // defined in libgcc
+    extern "C" {
+        fn __gnu_unwind_frame(exception_object: *mut uw::_Unwind_Exception,
+                                context: *mut uw::_Unwind_Context)
+                                -> uw::_Unwind_Reason_Code;
+    }
+}
+
+unsafe fn find_eh_action(context: *mut uw::_Unwind_Context) -> EHAction {
+    let lsda = uw::_Unwind_GetLanguageSpecificData(context) as *const u8;
+    let mut ip_before_instr: c_int = 0;
+    let ip = uw::_Unwind_GetIPInfo(context, &mut ip_before_instr);
+    let eh_context = EHContext {
+        // The return address points 1 byte past the call instruction,
+        // which could be in the next IP range in LSDA range table.
+        ip: if ip_before_instr != 0 { ip } else { ip - 1 },
+        func_start: uw::_Unwind_GetRegionStart(context),
+        get_text_start: &|| uw::_Unwind_GetTextRelBase(context),
+        get_data_start: &|| uw::_Unwind_GetDataRelBase(context),
+    };
+    eh::find_eh_action(lsda, &eh_context)
+}
+
+// *** Delete after a new snapshot ***
+#[cfg(all(stage0, any(target_os = "ios", not(target_arch = "arm"))))]
+#[lang = "eh_personality_catch"]
+#[no_mangle]
+pub unsafe extern "C" 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 {
+    rust_eh_personality(version, actions, exception_class, ue_header, context)
+}
+
+// *** Delete after a new snapshot ***
+#[cfg(all(stage0, target_arch = "arm", not(target_os = "ios")))]
+#[lang = "eh_personality_catch"]
+#[no_mangle]
+pub unsafe extern "C" fn rust_eh_personality_catch(state: uw::_Unwind_State,
+                                                    ue_header: *mut uw::_Unwind_Exception,
+                                                    context: *mut uw::_Unwind_Context)
+                                                    -> uw::_Unwind_Reason_Code {
+    rust_eh_personality(state, ue_header, context)
 }
 
 // See docs in the `unwind` module.
diff --git a/src/libpanic_unwind/seh64_gnu.rs b/src/libpanic_unwind/seh64_gnu.rs
index 7dc428871b3..3642e248895 100644
--- a/src/libpanic_unwind/seh64_gnu.rs
+++ b/src/libpanic_unwind/seh64_gnu.rs
@@ -81,6 +81,7 @@ pub unsafe fn cleanup(ptr: *mut u8) -> Box<Any + Send> {
 // This is considered acceptable, because the behavior of throwing exceptions
 // through a C ABI boundary is undefined.
 
+// *** Delete after a new snapshot ***
 #[cfg(stage0)]
 #[lang = "eh_personality_catch"]
 #[cfg(not(test))]
diff --git a/src/librustc/middle/lang_items.rs b/src/librustc/middle/lang_items.rs
index 960305e1048..a209b1d1abd 100644
--- a/src/librustc/middle/lang_items.rs
+++ b/src/librustc/middle/lang_items.rs
@@ -359,7 +359,6 @@ language_item_table! {
     StartFnLangItem,                 "start",                   start_fn;
 
     EhPersonalityLangItem,           "eh_personality",          eh_personality;
-    EhPersonalityCatchLangItem,      "eh_personality_catch",    eh_personality_catch;
     EhUnwindResumeLangItem,          "eh_unwind_resume",        eh_unwind_resume;
     MSVCTryFilterLangItem,           "msvc_try_filter",         msvc_try_filter;
 
diff --git a/src/librustc_trans/intrinsic.rs b/src/librustc_trans/intrinsic.rs
index e657a086581..1e4a2748182 100644
--- a/src/librustc_trans/intrinsic.rs
+++ b/src/librustc_trans/intrinsic.rs
@@ -19,7 +19,6 @@ use rustc::ty::subst;
 use rustc::ty::subst::FnSpace;
 use abi::{Abi, FnType};
 use adt;
-use attributes;
 use base::*;
 use build::*;
 use callee::{self, Callee};
@@ -37,7 +36,6 @@ use machine;
 use type_::Type;
 use rustc::ty::{self, Ty};
 use Disr;
-use rustc::ty::subst::Substs;
 use rustc::hir;
 use syntax::ast;
 use syntax::ptr::P;
@@ -1173,7 +1171,6 @@ fn trans_gnu_try<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
                              dloc: DebugLoc) -> Block<'blk, 'tcx> {
     let llfn = get_rust_try_fn(bcx.fcx, &mut |bcx| {
         let ccx = bcx.ccx();
-        let tcx = ccx.tcx();
         let dloc = DebugLoc::None;
 
         // Translates the shims described above:
@@ -1193,20 +1190,6 @@ fn trans_gnu_try<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
         // expected to be `*mut *mut u8` for this to actually work, but that's
         // managed by the standard library.
 
-        attributes::emit_uwtable(bcx.fcx.llfn, true);
-        let target = &bcx.sess().target.target;
-        let catch_pers = if target.arch == "arm" && target.target_os != "ios" {
-            // Only ARM still uses a separate catch personality (for now)
-            match tcx.lang_items.eh_personality_catch() {
-                Some(did) => {
-                    Callee::def(ccx, did, tcx.mk_substs(Substs::empty())).reify(ccx).val
-                }
-                None => bug!("eh_personality_catch not defined"),
-            }
-        } else {
-            bcx.fcx.eh_personality()
-        };
-
         let then = bcx.fcx.new_temp_block("then");
         let catch = bcx.fcx.new_temp_block("catch");
 
@@ -1224,7 +1207,7 @@ fn trans_gnu_try<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
         // rust_try ignores the selector.
         let lpad_ty = Type::struct_(ccx, &[Type::i8p(ccx), Type::i32(ccx)],
                                     false);
-        let vals = LandingPad(catch, lpad_ty, catch_pers, 1);
+        let vals = LandingPad(catch, lpad_ty, bcx.fcx.eh_personality(), 1);
         AddClause(catch, vals, C_null(Type::i8p(ccx)));
         let ptr = ExtractValue(catch, vals, 0);
         Store(catch, ptr, BitCast(catch, local_ptr, Type::i8p(ccx).ptr_to()));
diff --git a/src/libunwind/libunwind.rs b/src/libunwind/libunwind.rs
index d9b6c9ed74d..5e242db0a88 100644
--- a/src/libunwind/libunwind.rs
+++ b/src/libunwind/libunwind.rs
@@ -10,38 +10,15 @@
 
 #![allow(bad_style)]
 
-use libc;
-
-#[cfg(any(not(target_arch = "arm"), target_os = "ios"))]
-pub use self::_Unwind_Action::*;
-#[cfg(target_arch = "arm")]
-pub use self::_Unwind_State::*;
-pub use self::_Unwind_Reason_Code::*;
-
-#[cfg(any(not(target_arch = "arm"), target_os = "ios"))]
-#[repr(C)]
-#[derive(Clone, Copy)]
-pub enum _Unwind_Action {
-    _UA_SEARCH_PHASE = 1,
-    _UA_CLEANUP_PHASE = 2,
-    _UA_HANDLER_FRAME = 4,
-    _UA_FORCE_UNWIND = 8,
-    _UA_END_OF_STACK = 16,
+macro_rules! cfg_if {
+    ( $( if #[cfg( $meta:meta )] { $($it1:item)* } else { $($it2:item)* } )* ) =>
+        ( $( $( #[cfg($meta)] $it1)* $( #[cfg(not($meta))] $it2)* )* )
 }
 
-#[cfg(target_arch = "arm")]
-#[repr(C)]
-#[derive(Clone, Copy)]
-pub enum _Unwind_State {
-    _US_VIRTUAL_UNWIND_FRAME = 0,
-    _US_UNWIND_FRAME_STARTING = 1,
-    _US_UNWIND_FRAME_RESUME = 2,
-    _US_ACTION_MASK = 3,
-    _US_FORCE_UNWIND = 8,
-    _US_END_OF_STACK = 16,
-}
+use libc::{c_int, c_void, uintptr_t};
 
 #[repr(C)]
+#[derive(Copy, Clone, PartialEq)]
 pub enum _Unwind_Reason_Code {
     _URC_NO_REASON = 0,
     _URC_FOREIGN_EXCEPTION_CAUGHT = 1,
@@ -52,17 +29,15 @@ pub enum _Unwind_Reason_Code {
     _URC_HANDLER_FOUND = 6,
     _URC_INSTALL_CONTEXT = 7,
     _URC_CONTINUE_UNWIND = 8,
-    _URC_FAILURE = 9, // used only by ARM EABI
+    _URC_FAILURE = 9, // used only by ARM EHABI
 }
+pub use self::_Unwind_Reason_Code::*;
 
 pub type _Unwind_Exception_Class = u64;
-
-pub type _Unwind_Word = libc::uintptr_t;
-pub type _Unwind_Ptr = libc::uintptr_t;
-
-pub type _Unwind_Trace_Fn = extern "C" fn(ctx: *mut _Unwind_Context, arg: *mut libc::c_void)
+pub type _Unwind_Word = uintptr_t;
+pub type _Unwind_Ptr = uintptr_t;
+pub type _Unwind_Trace_Fn = extern "C" fn(ctx: *mut _Unwind_Context, arg: *mut c_void)
                                           -> _Unwind_Reason_Code;
-
 #[cfg(target_arch = "x86")]
 pub const unwinder_private_data_size: usize = 5;
 
@@ -99,91 +74,55 @@ pub enum _Unwind_Context {}
 
 pub type _Unwind_Exception_Cleanup_Fn = extern "C" fn(unwind_code: _Unwind_Reason_Code,
                                                       exception: *mut _Unwind_Exception);
-
-#[cfg_attr(any(all(target_os = "linux", not(target_env = "musl")),
-               target_os = "freebsd",
-               target_os = "solaris",
-               all(target_os = "linux",
-                   target_env = "musl",
-                   not(target_arch = "x86"),
-                   not(target_arch = "x86_64"))),
-           link(name = "gcc_s"))]
-#[cfg_attr(all(target_os = "linux",
-               target_env = "musl",
-               any(target_arch = "x86", target_arch = "x86_64"),
-               not(test)),
-           link(name = "unwind", kind = "static"))]
-#[cfg_attr(any(target_os = "android", target_os = "openbsd"),
-           link(name = "gcc"))]
-#[cfg_attr(all(target_os = "netbsd", not(target_vendor = "rumprun")),
-           link(name = "gcc"))]
-#[cfg_attr(all(target_os = "netbsd", target_vendor = "rumprun"),
-           link(name = "unwind"))]
-#[cfg_attr(target_os = "dragonfly",
-           link(name = "gcc_pic"))]
-#[cfg_attr(target_os = "bitrig",
-           link(name = "c++abi"))]
-#[cfg_attr(all(target_os = "windows", target_env = "gnu"),
-           link(name = "gcc_eh"))]
-#[cfg(not(cargobuild))]
-extern "C" {}
-
 extern "C" {
-    // iOS on armv7 uses SjLj exceptions and requires to link
-    // against corresponding routine (..._SjLj_...)
-    #[cfg(not(all(target_os = "ios", target_arch = "arm")))]
-    #[unwind]
-    pub fn _Unwind_RaiseException(exception: *mut _Unwind_Exception) -> _Unwind_Reason_Code;
-
-    #[cfg(all(target_os = "ios", target_arch = "arm"))]
-    #[unwind]
-    fn _Unwind_SjLj_RaiseException(e: *mut _Unwind_Exception) -> _Unwind_Reason_Code;
-
-    pub fn _Unwind_DeleteException(exception: *mut _Unwind_Exception);
-
     #[unwind]
     pub fn _Unwind_Resume(exception: *mut _Unwind_Exception) -> !;
-
-    // No native _Unwind_Backtrace on iOS
-    #[cfg(not(all(target_os = "ios", target_arch = "arm")))]
-    pub fn _Unwind_Backtrace(trace: _Unwind_Trace_Fn,
-                             trace_argument: *mut libc::c_void)
-                             -> _Unwind_Reason_Code;
-
-    // available since GCC 4.2.0, should be fine for our purpose
-    #[cfg(all(not(all(target_os = "android", target_arch = "arm")),
-              not(all(target_os = "linux", target_arch = "arm"))))]
-    pub fn _Unwind_GetIPInfo(ctx: *mut _Unwind_Context,
-                             ip_before_insn: *mut libc::c_int)
-                             -> libc::uintptr_t;
-
-    pub fn _Unwind_GetLanguageSpecificData(ctx: *mut _Unwind_Context) -> _Unwind_Ptr;
+    pub fn _Unwind_DeleteException(exception: *mut _Unwind_Exception);
+    pub fn _Unwind_GetLanguageSpecificData(ctx: *mut _Unwind_Context) -> *mut c_void;
     pub fn _Unwind_GetRegionStart(ctx: *mut _Unwind_Context) -> _Unwind_Ptr;
     pub fn _Unwind_GetTextRelBase(ctx: *mut _Unwind_Context) -> _Unwind_Ptr;
     pub fn _Unwind_GetDataRelBase(ctx: *mut _Unwind_Context) -> _Unwind_Ptr;
-    pub fn _Unwind_SetGR(ctx: *mut _Unwind_Context, reg_index: libc::c_int, value: _Unwind_Ptr);
-    pub fn _Unwind_SetIP(ctx: *mut _Unwind_Context, value: _Unwind_Ptr);
-
-    #[cfg(all(not(target_os = "android"),
-              not(all(target_os = "linux", target_arch = "arm"))))]
-    pub fn _Unwind_FindEnclosingFunction(pc: *mut libc::c_void) -> *mut libc::c_void;
 }
 
-// ... and now we just providing access to SjLj counterspart
-// through a standard name to hide those details from others
-// (see also comment above regarding _Unwind_RaiseException)
-#[cfg(all(target_os = "ios", target_arch = "arm"))]
-#[inline]
-pub unsafe fn _Unwind_RaiseException(exc: *mut _Unwind_Exception) -> _Unwind_Reason_Code {
-    _Unwind_SjLj_RaiseException(exc)
-}
+cfg_if! {
+if #[cfg(not(any(all(target_os = "android", target_arch = "arm"),
+                 all(target_os = "linux", target_arch = "arm"))))] {
+    // Not ARM EHABI
+    #[repr(C)]
+    #[derive(Copy, Clone, PartialEq)]
+    pub enum _Unwind_Action {
+        _UA_SEARCH_PHASE = 1,
+        _UA_CLEANUP_PHASE = 2,
+        _UA_HANDLER_FRAME = 4,
+        _UA_FORCE_UNWIND = 8,
+        _UA_END_OF_STACK = 16,
+    }
+    pub use self::_Unwind_Action::*;
+
+    extern "C" {
+        pub fn _Unwind_GetGR(ctx: *mut _Unwind_Context, reg_index: c_int) -> _Unwind_Word;
+        pub fn _Unwind_SetGR(ctx: *mut _Unwind_Context, reg_index: c_int, value: _Unwind_Word);
+        pub fn _Unwind_GetIP(ctx: *mut _Unwind_Context) -> _Unwind_Word;
+        pub fn _Unwind_SetIP(ctx: *mut _Unwind_Context, value: _Unwind_Word);
+        pub fn _Unwind_GetIPInfo(ctx: *mut _Unwind_Context, ip_before_insn: *mut c_int)
+                                 -> _Unwind_Word;
+        pub fn _Unwind_FindEnclosingFunction(pc: *mut c_void) -> *mut c_void;
+    }
+
+} else {
+    // ARM EHABI
+    #[repr(C)]
+    #[derive(Copy, Clone, PartialEq)]
+    pub enum _Unwind_State {
+        _US_VIRTUAL_UNWIND_FRAME = 0,
+        _US_UNWIND_FRAME_STARTING = 1,
+        _US_UNWIND_FRAME_RESUME = 2,
+        _US_ACTION_MASK = 3,
+        _US_FORCE_UNWIND = 8,
+        _US_END_OF_STACK = 16,
+    }
+    pub use self::_Unwind_State::*;
 
-// On android, the function _Unwind_GetIP is a macro, and this is the
-// expansion of the macro. This is all copy/pasted directly from the
-// header file with the definition of _Unwind_GetIP.
-#[cfg(any(all(target_os = "android", target_arch = "arm"),
-          all(target_os = "linux", target_arch = "arm")))]
-pub unsafe fn _Unwind_GetIP(ctx: *mut _Unwind_Context) -> libc::uintptr_t {
     #[repr(C)]
     enum _Unwind_VRS_Result {
         _UVRSR_OK = 0,
@@ -198,6 +137,7 @@ pub unsafe fn _Unwind_GetIP(ctx: *mut _Unwind_Context) -> libc::uintptr_t {
         _UVRSC_WMMXD = 3,
         _UVRSC_WMMXC = 4,
     }
+    use self::_Unwind_VRS_RegClass::*;
     #[repr(C)]
     enum _Unwind_VRS_DataRepresentation {
         _UVRSD_UINT32 = 0,
@@ -207,42 +147,116 @@ pub unsafe fn _Unwind_GetIP(ctx: *mut _Unwind_Context) -> libc::uintptr_t {
         _UVRSD_FLOAT = 4,
         _UVRSD_DOUBLE = 5,
     }
+    use self::_Unwind_VRS_DataRepresentation::*;
+
+    pub const UNWIND_POINTER_REG: c_int = 12;
+    pub const UNWIND_IP_REG: c_int = 15;
 
-    type _Unwind_Word = libc::c_uint;
     extern "C" {
         fn _Unwind_VRS_Get(ctx: *mut _Unwind_Context,
-                           klass: _Unwind_VRS_RegClass,
-                           word: _Unwind_Word,
+                           regclass: _Unwind_VRS_RegClass,
+                           regno: _Unwind_Word,
+                           repr: _Unwind_VRS_DataRepresentation,
+                           data: *mut c_void)
+                           -> _Unwind_VRS_Result;
+
+        fn _Unwind_VRS_Set(ctx: *mut _Unwind_Context,
+                           regclass: _Unwind_VRS_RegClass,
+                           regno: _Unwind_Word,
                            repr: _Unwind_VRS_DataRepresentation,
-                           data: *mut libc::c_void)
+                           data: *mut c_void)
                            -> _Unwind_VRS_Result;
     }
 
-    let mut val: _Unwind_Word = 0;
-    let ptr = &mut val as *mut _Unwind_Word;
-    let _ = _Unwind_VRS_Get(ctx,
-                            _Unwind_VRS_RegClass::_UVRSC_CORE,
-                            15,
-                            _Unwind_VRS_DataRepresentation::_UVRSD_UINT32,
-                            ptr as *mut libc::c_void);
-    (val & !1) as libc::uintptr_t
-}
+    // On Android or ARM/Linux, these are implemented as macros:
+
+    pub unsafe fn _Unwind_GetGR(ctx: *mut _Unwind_Context, reg_index: c_int) -> _Unwind_Word {
+        let mut val: _Unwind_Word = 0;
+        _Unwind_VRS_Get(ctx, _UVRSC_CORE, reg_index as _Unwind_Word, _UVRSD_UINT32,
+                        &mut val as *mut _ as *mut c_void);
+        val
+    }
 
-// This function doesn't exist on Android or ARM/Linux, so make it same
-// to _Unwind_GetIP
-#[cfg(any(all(target_os = "android", target_arch = "arm"),
-          all(target_os = "linux", target_arch = "arm")))]
-pub unsafe fn _Unwind_GetIPInfo(ctx: *mut _Unwind_Context,
-                                ip_before_insn: *mut libc::c_int)
-                                -> libc::uintptr_t {
-    *ip_before_insn = 0;
-    _Unwind_GetIP(ctx)
+    pub unsafe fn _Unwind_SetGR(ctx: *mut _Unwind_Context, reg_index: c_int, value: _Unwind_Word) {
+        let mut value = value;
+        _Unwind_VRS_Set(ctx, _UVRSC_CORE, reg_index as _Unwind_Word, _UVRSD_UINT32,
+                        &mut value as *mut _ as *mut c_void);
+    }
+
+    pub unsafe fn _Unwind_GetIP(ctx: *mut _Unwind_Context)
+                                -> _Unwind_Word {
+        let val = _Unwind_GetGR(ctx, UNWIND_IP_REG);
+        (val & !1) as _Unwind_Word
+    }
+
+    pub unsafe fn _Unwind_SetIP(ctx: *mut _Unwind_Context,
+                                value: _Unwind_Word) {
+        // Propagate thumb bit to instruction pointer
+        let thumb_state = _Unwind_GetGR(ctx, UNWIND_IP_REG) & 1;
+        let value = value | thumb_state;
+        _Unwind_SetGR(ctx, UNWIND_IP_REG, value);
+    }
+
+    pub unsafe fn _Unwind_GetIPInfo(ctx: *mut _Unwind_Context,
+                                    ip_before_insn: *mut c_int)
+                                    -> _Unwind_Word {
+        *ip_before_insn = 0;
+        _Unwind_GetIP(ctx)
+    }
+
+    // This function also doesn't exist on Android or ARM/Linux, so make it a no-op
+    pub unsafe fn _Unwind_FindEnclosingFunction(pc: *mut c_void) -> *mut c_void {
+        pc
+    }
 }
 
-// This function also doesn't exist on Android or ARM/Linux, so make it
-// a no-op
-#[cfg(any(target_os = "android",
-          all(target_os = "linux", target_arch = "arm")))]
-pub unsafe fn _Unwind_FindEnclosingFunction(pc: *mut libc::c_void) -> *mut libc::c_void {
-    pc
+if #[cfg(not(all(target_os = "ios", target_arch = "arm")))] {
+    // Not 32-bit iOS
+    extern "C" {
+        #[unwind]
+        pub fn _Unwind_RaiseException(exception: *mut _Unwind_Exception) -> _Unwind_Reason_Code;
+        pub fn _Unwind_Backtrace(trace: _Unwind_Trace_Fn,
+                                 trace_argument: *mut c_void)
+                                 -> _Unwind_Reason_Code;
+    }
+} else {
+    // 32-bit iOS uses SjLj and does not provide _Unwind_Backtrace()
+    extern "C" {
+        #[unwind]
+        pub fn _Unwind_SjLj_RaiseException(e: *mut _Unwind_Exception) -> _Unwind_Reason_Code;
+    }
+
+    #[inline]
+    pub unsafe fn _Unwind_RaiseException(exc: *mut _Unwind_Exception) -> _Unwind_Reason_Code {
+        _Unwind_SjLj_RaiseException(exc)
+    }
 }
+} // cfg_if!
+
+#[cfg_attr(any(all(target_os = "linux", not(target_env = "musl")),
+               target_os = "freebsd",
+               target_os = "solaris",
+               all(target_os = "linux",
+                   target_env = "musl",
+                   not(target_arch = "x86"),
+                   not(target_arch = "x86_64"))),
+           link(name = "gcc_s"))]
+#[cfg_attr(all(target_os = "linux",
+               target_env = "musl",
+               any(target_arch = "x86", target_arch = "x86_64"),
+               not(test)),
+           link(name = "unwind", kind = "static"))]
+#[cfg_attr(any(target_os = "android", target_os = "openbsd"),
+           link(name = "gcc"))]
+#[cfg_attr(all(target_os = "netbsd", not(target_vendor = "rumprun")),
+           link(name = "gcc"))]
+#[cfg_attr(all(target_os = "netbsd", target_vendor = "rumprun"),
+           link(name = "unwind"))]
+#[cfg_attr(target_os = "dragonfly",
+           link(name = "gcc_pic"))]
+#[cfg_attr(target_os = "bitrig",
+           link(name = "c++abi"))]
+#[cfg_attr(all(target_os = "windows", target_env = "gnu"),
+           link(name = "gcc_eh"))]
+#[cfg(not(cargobuild))]
+extern "C" {}