sess: default to v0 symbol mangling

Rust's current mangling scheme depends on compiler internals; loses
information about generic parameters (and other things) which makes for
a worse experience when using external tools that need to interact with
Rust symbol names; is inconsistent; and can contain `.` characters
which aren't universally supported. Therefore, Rust has defined its own
symbol mangling scheme which is defined in terms of the Rust language,
not the compiler implementation; encodes information about generic
parameters in a reversible way; has a consistent definition; and
generates symbols that only use the characters `A-Z`, `a-z`, `0-9`, and
`_`.

Support for the new Rust symbol mangling scheme has been added to
upstream tools that will need to interact with Rust symbols (e.g.
debuggers).

This commit changes the default symbol mangling scheme from the legacy
scheme to the new Rust mangling scheme.

Signed-off-by: David Wood <david.wood@huawei.com>

Author: davidtwco

compiler/rustc_session/src/config.rs

@@ -1496,7 +1496,7 @@ impl Options {
     }
 
     pub fn get_symbol_mangling_version(&self) -> SymbolManglingVersion {
-        self.cg.symbol_mangling_version.unwrap_or(SymbolManglingVersion::Legacy)
+        self.cg.symbol_mangling_version.unwrap_or(SymbolManglingVersion::V0)
     }
 }
 

tests/codegen-llvm/array-from_fn.rs

@@ -7,7 +7,7 @@
 
 #[no_mangle]
 pub fn iota() -> [u8; 16] {
-    // OPT-NOT: core..array..Guard
-    // NORMAL: core..array..Guard
+    // OPT-NOT: core::array::Guard
+    // NORMAL: core::array::Guard
     std::array::from_fn(|i| i as _)
 }

tests/codegen-llvm/no-alloca-inside-if-false.rs

@@ -7,10 +7,10 @@
 
 #[inline(never)]
 fn test<const SIZE: usize>() {
-    // CHECK-LABEL: no_alloca_inside_if_false::test
+    // CHECK-LABEL: no_alloca_inside_if_false::test::<8192>
     // CHECK: start:
-    // CHECK-NEXT: alloca [{{12|24}} x i8]
-    // CHECK-NOT: alloca
+    // CHECK-NEXT: = alloca [{{12|24}} x i8]
+    // CHECK-NOT: = alloca
     if const { SIZE < 4096 } {
         let arr = [0u8; SIZE];
         std::hint::black_box(&arr);

tests/codegen-llvm/precondition-checks.rs

@@ -13,13 +13,13 @@
 
 use std::ptr::NonNull;
 
-// CHECK-LABEL: ; core::ptr::non_null::NonNull<T>::new_unchecked
+// CHECK-LABEL: ; <core::ptr::non_null::NonNull<u8>>::new_unchecked
 // CHECK-NOT: call
 // CHECK: }
 
 // CHECK-LABEL: @nonnull_new
 #[no_mangle]
 pub unsafe fn nonnull_new(ptr: *mut u8) -> NonNull<u8> {
-    // CHECK: ; call core::ptr::non_null::NonNull<T>::new_unchecked
+    // CHECK: ; call <core::ptr::non_null::NonNull<u8>>::new_unchecked
     unsafe { NonNull::new_unchecked(ptr) }
 }

tests/codegen-llvm/sanitizer/cfi/emit-type-metadata-id-itanium-cxx-abi-drop-in-place.rs

@@ -9,7 +9,7 @@
 
 #![crate_type = "lib"]
 
-// CHECK-LABEL: define{{.*}}4core3ptr47drop_in_place$LT$dyn$u20$core..marker..Send$GT$
+// CHECK-LABEL: define{{.*}}4core3ptr13drop_in_placeDNtNtB4_6marker4Send
 // CHECK-SAME:  {{.*}}!type ![[TYPE1:[0-9]+]] !type !{{[0-9]+}} !type !{{[0-9]+}} !type !{{[0-9]+}}
 // CHECK:       call i1 @llvm.type.test(ptr {{%.+}}, metadata !"_ZTSFvPu3dynIu{{[0-9]+}}NtNtNtC{{[[:print:]]+}}_4core3ops4drop4Dropu6regionEE")
 
@@ -20,7 +20,7 @@ struct PresentDrop;
 
 impl Drop for PresentDrop {
     fn drop(&mut self) {}
-    // CHECK: define{{.*}}4core3ptr{{[0-9]+}}drop_in_place$LT${{.*}}PresentDrop$GT${{.*}}!type ![[TYPE1]] !type !{{[0-9]+}} !type !{{[0-9]+}} !type !{{[0-9]+}}
+    // CHECK: define{{.*}}4core3ptr{{[0-9]+}}drop_in_place{{.*}}PresentDrop{{.*}}!type ![[TYPE1]] !type !{{[0-9]+}} !type !{{[0-9]+}} !type !{{[0-9]+}}
 }
 
 pub fn foo() {

tests/codegen-llvm/sanitizer/kcfi/naked-function.rs

@@ -28,7 +28,7 @@ impl MyTrait for Thing {}
 // the shim calls the real function
 // CHECK-LABEL: define
 // CHECK-SAME: my_naked_function
-// CHECK-SAME: reify.shim.fnptr
+// CHECK-SAME: reify_fnptr
 
 // CHECK-LABEL: main
 #[unsafe(no_mangle)]
@@ -39,7 +39,7 @@ pub fn main() {
     // main calls the shim function
     // CHECK: call void
     // CHECK-SAME: my_naked_function
-    // CHECK-SAME: reify.shim.fnptr
+    // CHECK-SAME: reify_fnptr
     (F)();
 }
 

tests/ui/panics/short-ice-remove-middle-frames-2.run.stderr

@@ -4,12 +4,12 @@ debug!!!
 stack backtrace:
    0: std::panicking::begin_panic
    1: short_ice_remove_middle_frames_2::eight
-   2: short_ice_remove_middle_frames_2::seven::{{closure}}
+   2: short_ice_remove_middle_frames_2::seven::{closure#0}
       [... omitted 3 frames ...]
    3: short_ice_remove_middle_frames_2::fifth
-   4: short_ice_remove_middle_frames_2::fourth::{{closure}}
+   4: short_ice_remove_middle_frames_2::fourth::{closure#0}
       [... omitted 4 frames ...]
    5: short_ice_remove_middle_frames_2::first
    6: short_ice_remove_middle_frames_2::main
-   7: core::ops::function::FnOnce::call_once
+   7: <fn() as core::ops::function::FnOnce<()>>::call_once
 note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

tests/ui/panics/short-ice-remove-middle-frames.run.stderr

@@ -5,11 +5,11 @@ stack backtrace:
    0: std::panicking::begin_panic
    1: short_ice_remove_middle_frames::seven
    2: short_ice_remove_middle_frames::sixth
-   3: short_ice_remove_middle_frames::fifth::{{closure}}
+   3: short_ice_remove_middle_frames::fifth::{closure#0}
       [... omitted 4 frames ...]
    4: short_ice_remove_middle_frames::second
-   5: short_ice_remove_middle_frames::first::{{closure}}
+   5: short_ice_remove_middle_frames::first::{closure#0}
    6: short_ice_remove_middle_frames::first
    7: short_ice_remove_middle_frames::main
-   8: core::ops::function::FnOnce::call_once
+   8: <fn() as core::ops::function::FnOnce<()>>::call_once
 note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.