Sync rustc_codegen_cranelift 'ddd4ce25535cf71203ba3700896131ce55fde795'

compiler/rustc_codegen_cranelift/src/debuginfo/unwind.rs

@@ -5,17 +5,19 @@ use crate::prelude::*;
 use cranelift_codegen::isa::{unwind::UnwindInfo, TargetIsa};
 
 use gimli::write::{Address, CieId, EhFrame, FrameTable, Section};
+use gimli::RunTimeEndian;
 
 use crate::backend::WriteDebugInfo;
 
-pub(crate) struct UnwindContext<'tcx> {
-    tcx: TyCtxt<'tcx>,
+pub(crate) struct UnwindContext {
+    endian: RunTimeEndian,
     frame_table: FrameTable,
     cie_id: Option<CieId>,
 }
 
-impl<'tcx> UnwindContext<'tcx> {
-    pub(crate) fn new(tcx: TyCtxt<'tcx>, isa: &dyn TargetIsa, pic_eh_frame: bool) -> Self {
+impl UnwindContext {
+    pub(crate) fn new(tcx: TyCtxt<'_>, isa: &dyn TargetIsa, pic_eh_frame: bool) -> Self {
+        let endian = super::target_endian(tcx);
         let mut frame_table = FrameTable::default();
 
         let cie_id = if let Some(mut cie) = isa.create_systemv_cie() {
@@ -28,7 +30,7 @@ impl<'tcx> UnwindContext<'tcx> {
             None
         };
 
-        UnwindContext { tcx, frame_table, cie_id }
+        UnwindContext { endian, frame_table, cie_id }
     }
 
     pub(crate) fn add_function(&mut self, func_id: FuncId, context: &Context, isa: &dyn TargetIsa) {
@@ -54,8 +56,7 @@ impl<'tcx> UnwindContext<'tcx> {
     }
 
     pub(crate) fn emit<P: WriteDebugInfo>(self, product: &mut P) {
-        let mut eh_frame =
-            EhFrame::from(super::emit::WriterRelocate::new(super::target_endian(self.tcx)));
+        let mut eh_frame = EhFrame::from(super::emit::WriterRelocate::new(self.endian));
         self.frame_table.write_eh_frame(&mut eh_frame).unwrap();
 
         if !eh_frame.0.writer.slice().is_empty() {
@@ -71,16 +72,12 @@ impl<'tcx> UnwindContext<'tcx> {
     }
 
     #[cfg(feature = "jit")]
-    pub(crate) unsafe fn register_jit(
-        self,
-        jit_module: &cranelift_jit::JITModule,
-    ) -> Option<UnwindRegistry> {
-        let mut eh_frame =
-            EhFrame::from(super::emit::WriterRelocate::new(super::target_endian(self.tcx)));
+    pub(crate) unsafe fn register_jit(self, jit_module: &cranelift_jit::JITModule) {
+        let mut eh_frame = EhFrame::from(super::emit::WriterRelocate::new(self.endian));
         self.frame_table.write_eh_frame(&mut eh_frame).unwrap();
 
         if eh_frame.0.writer.slice().is_empty() {
-            return None;
+            return;
         }
 
         let mut eh_frame = eh_frame.0.relocate_for_jit(jit_module);
@@ -88,7 +85,10 @@ impl<'tcx> UnwindContext<'tcx> {
         // GCC expects a terminating "empty" length, so write a 0 length at the end of the table.
         eh_frame.extend(&[0, 0, 0, 0]);
 
-        let mut registrations = Vec::new();
+        // FIXME support unregistering unwind tables once cranelift-jit supports deallocating
+        // individual functions
+        #[allow(unused_variables)]
+        let (eh_frame, eh_frame_len, _) = Vec::into_raw_parts(eh_frame);
 
         // =======================================================================
         // Everything after this line up to the end of the file is loosly based on
@@ -96,8 +96,8 @@ impl<'tcx> UnwindContext<'tcx> {
         #[cfg(target_os = "macos")]
         {
             // On macOS, `__register_frame` takes a pointer to a single FDE
-            let start = eh_frame.as_ptr();
-            let end = start.add(eh_frame.len());
+            let start = eh_frame;
+            let end = start.add(eh_frame_len);
             let mut current = start;
 
             // Walk all of the entries in the frame table and register them
@@ -107,7 +107,6 @@ impl<'tcx> UnwindContext<'tcx> {
                 // Skip over the CIE
                 if current != start {
                     __register_frame(current);
-                    registrations.push(current as usize);
                 }
 
                 // Move to the next table entry (+4 because the length itself is not inclusive)
@@ -117,41 +116,12 @@ impl<'tcx> UnwindContext<'tcx> {
         #[cfg(not(target_os = "macos"))]
         {
             // On other platforms, `__register_frame` will walk the FDEs until an entry of length 0
-            let ptr = eh_frame.as_ptr();
-            __register_frame(ptr);
-            registrations.push(ptr as usize);
+            __register_frame(eh_frame);
         }
-
-        Some(UnwindRegistry { _frame_table: eh_frame, registrations })
     }
 }
 
-/// Represents a registry of function unwind information for System V ABI.
-pub(crate) struct UnwindRegistry {
-    _frame_table: Vec<u8>,
-    registrations: Vec<usize>,
-}
-
 extern "C" {
     // libunwind import
     fn __register_frame(fde: *const u8);
-    fn __deregister_frame(fde: *const u8);
-}
-
-impl Drop for UnwindRegistry {
-    fn drop(&mut self) {
-        unsafe {
-            // libgcc stores the frame entries as a linked list in decreasing sort order
-            // based on the PC value of the registered entry.
-            //
-            // As we store the registrations in increasing order, it would be O(N^2) to
-            // deregister in that order.
-            //
-            // To ensure that we just pop off the first element in the list upon every
-            // deregistration, walk our list of registrations backwards.
-            for fde in self.registrations.iter().rev() {
-                __deregister_frame(*fde as *const _);
-            }
-        }
-    }
 }