Auto merge of rust-lang#70175 - Amanieu:remove_nlp, r=pnkfelix

Remove -Z no-landing-pads flag

Since rust-lang#67502, `-Z no-landing-pads` will cause all attempted unwinds to abort since we don't generate a `try` / `catch`. This previously worked because `__rust_try` was located in libpanic_unwind which is always compiled with `-C panic=unwind`, but `__rust_try` is now directly inline into the crate that uses `catch_unwind`.

As such, `-Z no-landing-pads` is now mostly useless and people should use `-C panic=abort` instead.

src/librustc_codegen_llvm/attributes.rs

@@ -13,6 +13,7 @@ use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_session::config::{OptLevel, Sanitizer};
 use rustc_session::Session;
+use rustc_target::spec::PanicStrategy;
 
 use crate::attributes;
 use crate::llvm::AttributePlace::Function;
@@ -270,7 +271,9 @@ pub fn from_fn_attrs(cx: &CodegenCx<'ll, 'tcx>, llfn: &'ll Value, instance: ty::
     //
     // You can also find more info on why Windows is whitelisted here in:
     //      https://bugzilla.mozilla.org/show_bug.cgi?id=1302078
-    if !cx.sess().no_landing_pads() || cx.sess().target.target.options.requires_uwtable {
+    if cx.sess().panic_strategy() == PanicStrategy::Unwind
+        || cx.sess().target.target.options.requires_uwtable
+    {
         attributes::emit_uwtable(llfn, true);
     }
 

src/librustc_codegen_llvm/intrinsic.rs

@@ -22,6 +22,7 @@ use rustc_middle::ty::{self, Ty};
 use rustc_middle::{bug, span_bug};
 use rustc_span::Span;
 use rustc_target::abi::{self, HasDataLayout, LayoutOf, Primitive};
+use rustc_target::spec::PanicStrategy;
 
 use std::cmp::Ordering;
 use std::iter;
@@ -804,7 +805,7 @@ fn try_intrinsic(
     catch_func: &'ll Value,
     dest: &'ll Value,
 ) {
-    if bx.sess().no_landing_pads() {
+    if bx.sess().panic_strategy() == PanicStrategy::Abort {
         bx.call(try_func, &[data], None);
         // Return 0 unconditionally from the intrinsic call;
         // we can never unwind.

src/librustc_codegen_ssa/back/write.rs

@@ -35,7 +35,7 @@ use rustc_session::Session;
 use rustc_span::hygiene::ExpnId;
 use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::{sym, Symbol};
-use rustc_target::spec::MergeFunctions;
+use rustc_target::spec::{MergeFunctions, PanicStrategy};
 
 use std::any::Any;
 use std::fs;
@@ -995,7 +995,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
         crate_types: sess.crate_types.borrow().clone(),
         each_linked_rlib_for_lto,
         lto: sess.lto(),
-        no_landing_pads: sess.no_landing_pads(),
+        no_landing_pads: sess.panic_strategy() == PanicStrategy::Abort,
         fewer_names: sess.fewer_names(),
         save_temps: sess.opts.cg.save_temps,
         opts: Arc::new(sess.opts.clone()),

src/librustc_interface/tests.rs

@@ -546,7 +546,6 @@ fn test_debugging_options_tracking_hash() {
     tracked!(new_llvm_pass_manager, true);
     tracked!(no_codegen, true);
     tracked!(no_generate_arange_section, true);
-    tracked!(no_landing_pads, true);
     tracked!(no_link, true);
     tracked!(no_profiler_runtime, true);
     tracked!(osx_rpath_install_name, true);

src/librustc_mir/transform/generator.rs

@@ -68,6 +68,7 @@ use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::GeneratorSubsts;
 use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt};
 use rustc_target::abi::VariantIdx;
+use rustc_target::spec::PanicStrategy;
 use std::borrow::Cow;
 use std::iter;
 
@@ -978,7 +979,7 @@ fn can_return<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) -> bool {
 
 fn can_unwind<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) -> bool {
     // Nothing can unwind when landing pads are off.
-    if tcx.sess.no_landing_pads() {
+    if tcx.sess.panic_strategy() == PanicStrategy::Abort {
         return false;
     }
 

src/librustc_mir/transform/no_landing_pads.rs

@@ -5,6 +5,7 @@ use crate::transform::{MirPass, MirSource};
 use rustc_middle::mir::visit::MutVisitor;
 use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
+use rustc_target::spec::PanicStrategy;
 
 pub struct NoLandingPads<'tcx> {
     tcx: TyCtxt<'tcx>,
@@ -23,7 +24,7 @@ impl<'tcx> MirPass<'tcx> for NoLandingPads<'tcx> {
 }
 
 pub fn no_landing_pads<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-    if tcx.sess.no_landing_pads() {
+    if tcx.sess.panic_strategy() == PanicStrategy::Abort {
         NoLandingPads::new(tcx).visit_body(body);
     }
 }

src/librustc_mir/transform/remove_noop_landing_pads.rs

@@ -3,14 +3,15 @@ use crate::util::patch::MirPatch;
 use rustc_index::bit_set::BitSet;
 use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
+use rustc_target::spec::PanicStrategy;
 
 /// A pass that removes noop landing pads and replaces jumps to them with
 /// `None`. This is important because otherwise LLVM generates terrible
 /// code for these.
 pub struct RemoveNoopLandingPads;
 
 pub fn remove_noop_landing_pads<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-    if tcx.sess.no_landing_pads() {
+    if tcx.sess.panic_strategy() == PanicStrategy::Abort {
         return;
     }
     debug!("remove_noop_landing_pads({:?})", body);

src/librustc_mir_build/build/mod.rs

@@ -536,11 +536,6 @@ fn should_abort_on_panic(tcx: TyCtxt<'_>, fn_def_id: LocalDefId, _abi: Abi) -> b
         return false;
     }
 
-    // We cannot add landing pads, so don't add one.
-    if tcx.sess.no_landing_pads() {
-        return false;
-    }
-
     // This is a special case: some functions have a C abi but are meant to
     // unwind anyway. Don't stop them.
     match unwind_attr {

src/librustc_session/options.rs

@@ -878,8 +878,6 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "omit DWARF address ranges that give faster lookups"),
     no_interleave_lints: bool = (false, parse_no_flag, [UNTRACKED],
         "execute lints separately; allows benchmarking individual lints"),
-    no_landing_pads: bool = (false, parse_no_flag, [TRACKED],
-        "omit landing pads for unwinding"),
     no_leak_check: bool = (false, parse_no_flag, [UNTRACKED],
         "disable the 'leak check' for subtyping; unsound, but useful for tests"),
     no_link: bool = (false, parse_no_flag, [TRACKED],

src/librustc_session/session.rs

@@ -540,9 +540,6 @@ impl Session {
         self.opts.debugging_opts.fewer_names || !more_names
     }
 
-    pub fn no_landing_pads(&self) -> bool {
-        self.opts.debugging_opts.no_landing_pads || self.panic_strategy() == PanicStrategy::Abort
-    }
     pub fn unstable_options(&self) -> bool {
         self.opts.debugging_opts.unstable_options
     }

src/test/mir-opt/generator-tiny.rs

@@ -1,7 +1,8 @@
 //! Tests that generators that cannot return or unwind don't have unnecessary
 //! panic branches.
 
-// compile-flags: -Zno-landing-pads
+// compile-flags: -C panic=abort
+// no-prefer-dynamic
 
 #![feature(generators, generator_trait)]
 

src/test/mir-opt/generator-tiny/rustc.main-{{closure}}.generator_resume.0.mir

@@ -1,78 +1,78 @@
 // MIR for `main::{{closure}}#0` 0 generator_resume
 // generator_layout = GeneratorLayout { field_tys: [HasDrop], variant_fields: [[], [], [], [_0]], storage_conflicts: BitMatrix { num_rows: 1, num_columns: 1, words: [1], marker: PhantomData } }
 
-fn main::{{closure}}#0(_1: std::pin::Pin<&mut [generator@$DIR/generator-tiny.rs:18:16: 24:6 {u8, HasDrop, ()}]>, _2: u8) -> std::ops::GeneratorState<(), ()> {
-    debug _x => _10;                     // in scope 0 at $DIR/generator-tiny.rs:18:17: 18:19
-    let mut _0: std::ops::GeneratorState<(), ()>; // return place in scope 0 at $DIR/generator-tiny.rs:18:16: 24:6
-    let _3: HasDrop;                     // in scope 0 at $DIR/generator-tiny.rs:19:13: 19:15
-    let mut _4: !;                       // in scope 0 at $DIR/generator-tiny.rs:20:9: 23:10
-    let mut _5: ();                      // in scope 0 at $DIR/generator-tiny.rs:18:16: 24:6
-    let _6: u8;                          // in scope 0 at $DIR/generator-tiny.rs:21:13: 21:18
-    let mut _7: ();                      // in scope 0 at $DIR/generator-tiny.rs:21:13: 21:18
-    let _8: ();                          // in scope 0 at $DIR/generator-tiny.rs:22:13: 22:21
-    let mut _9: ();                      // in scope 0 at $DIR/generator-tiny.rs:18:25: 18:25
-    let _10: u8;                         // in scope 0 at $DIR/generator-tiny.rs:18:17: 18:19
-    let mut _11: isize;                  // in scope 0 at $DIR/generator-tiny.rs:18:16: 24:6
+fn main::{{closure}}#0(_1: std::pin::Pin<&mut [generator@$DIR/generator-tiny.rs:19:16: 25:6 {u8, HasDrop, ()}]>, _2: u8) -> std::ops::GeneratorState<(), ()> {
+    debug _x => _10;                     // in scope 0 at $DIR/generator-tiny.rs:19:17: 19:19
+    let mut _0: std::ops::GeneratorState<(), ()>; // return place in scope 0 at $DIR/generator-tiny.rs:19:16: 25:6
+    let _3: HasDrop;                     // in scope 0 at $DIR/generator-tiny.rs:20:13: 20:15
+    let mut _4: !;                       // in scope 0 at $DIR/generator-tiny.rs:21:9: 24:10
+    let mut _5: ();                      // in scope 0 at $DIR/generator-tiny.rs:19:16: 25:6
+    let _6: u8;                          // in scope 0 at $DIR/generator-tiny.rs:22:13: 22:18
+    let mut _7: ();                      // in scope 0 at $DIR/generator-tiny.rs:22:13: 22:18
+    let _8: ();                          // in scope 0 at $DIR/generator-tiny.rs:23:13: 23:21
+    let mut _9: ();                      // in scope 0 at $DIR/generator-tiny.rs:19:25: 19:25
+    let _10: u8;                         // in scope 0 at $DIR/generator-tiny.rs:19:17: 19:19
+    let mut _11: isize;                  // in scope 0 at $DIR/generator-tiny.rs:19:16: 25:6
     scope 1 {
-        debug _d => (((*(_1.0: &mut [generator@$DIR/generator-tiny.rs:18:16: 24:6 {u8, HasDrop, ()}])) as variant#3).0: HasDrop); // in scope 1 at $DIR/generator-tiny.rs:19:13: 19:15
+        debug _d => (((*(_1.0: &mut [generator@$DIR/generator-tiny.rs:19:16: 25:6 {u8, HasDrop, ()}])) as variant#3).0: HasDrop); // in scope 1 at $DIR/generator-tiny.rs:20:13: 20:15
     }
 
     bb0: {
-        _11 = discriminant((*(_1.0: &mut [generator@$DIR/generator-tiny.rs:18:16: 24:6 {u8, HasDrop, ()}]))); // scope 0 at $DIR/generator-tiny.rs:18:16: 24:6
-        switchInt(move _11) -> [0u32: bb1, 3u32: bb5, otherwise: bb6]; // scope 0 at $DIR/generator-tiny.rs:18:16: 24:6
+        _11 = discriminant((*(_1.0: &mut [generator@$DIR/generator-tiny.rs:19:16: 25:6 {u8, HasDrop, ()}]))); // scope 0 at $DIR/generator-tiny.rs:19:16: 25:6
+        switchInt(move _11) -> [0u32: bb1, 3u32: bb5, otherwise: bb6]; // scope 0 at $DIR/generator-tiny.rs:19:16: 25:6
     }
 
     bb1: {
-        _10 = move _2;                   // scope 0 at $DIR/generator-tiny.rs:18:16: 24:6
-        nop;                             // scope 0 at $DIR/generator-tiny.rs:19:13: 19:15
-        (((*(_1.0: &mut [generator@$DIR/generator-tiny.rs:18:16: 24:6 {u8, HasDrop, ()}])) as variant#3).0: HasDrop) = HasDrop; // scope 0 at $DIR/generator-tiny.rs:19:18: 19:25
-        StorageLive(_4);                 // scope 1 at $DIR/generator-tiny.rs:20:9: 23:10
-        goto -> bb2;                     // scope 1 at $DIR/generator-tiny.rs:20:9: 23:10
+        _10 = move _2;                   // scope 0 at $DIR/generator-tiny.rs:19:16: 25:6
+        nop;                             // scope 0 at $DIR/generator-tiny.rs:20:13: 20:15
+        (((*(_1.0: &mut [generator@$DIR/generator-tiny.rs:19:16: 25:6 {u8, HasDrop, ()}])) as variant#3).0: HasDrop) = HasDrop; // scope 0 at $DIR/generator-tiny.rs:20:18: 20:25
+        StorageLive(_4);                 // scope 1 at $DIR/generator-tiny.rs:21:9: 24:10
+        goto -> bb2;                     // scope 1 at $DIR/generator-tiny.rs:21:9: 24:10
     }
 
     bb2: {
-        StorageLive(_6);                 // scope 1 at $DIR/generator-tiny.rs:21:13: 21:18
-        StorageLive(_7);                 // scope 1 at $DIR/generator-tiny.rs:21:13: 21:18
-        _7 = ();                         // scope 1 at $DIR/generator-tiny.rs:21:13: 21:18
-        _0 = std::ops::GeneratorState::<(), ()>::Yielded(move _7); // scope 1 at $DIR/generator-tiny.rs:21:13: 21:18
-        discriminant((*(_1.0: &mut [generator@$DIR/generator-tiny.rs:18:16: 24:6 {u8, HasDrop, ()}]))) = 3; // scope 1 at $DIR/generator-tiny.rs:21:13: 21:18
-        return;                          // scope 1 at $DIR/generator-tiny.rs:21:13: 21:18
+        StorageLive(_6);                 // scope 1 at $DIR/generator-tiny.rs:22:13: 22:18
+        StorageLive(_7);                 // scope 1 at $DIR/generator-tiny.rs:22:13: 22:18
+        _7 = ();                         // scope 1 at $DIR/generator-tiny.rs:22:13: 22:18
+        _0 = std::ops::GeneratorState::<(), ()>::Yielded(move _7); // scope 1 at $DIR/generator-tiny.rs:22:13: 22:18
+        discriminant((*(_1.0: &mut [generator@$DIR/generator-tiny.rs:19:16: 25:6 {u8, HasDrop, ()}]))) = 3; // scope 1 at $DIR/generator-tiny.rs:22:13: 22:18
+        return;                          // scope 1 at $DIR/generator-tiny.rs:22:13: 22:18
     }
 
     bb3: {
-        StorageDead(_7);                 // scope 1 at $DIR/generator-tiny.rs:21:17: 21:18
-        StorageDead(_6);                 // scope 1 at $DIR/generator-tiny.rs:21:18: 21:19
-        StorageLive(_8);                 // scope 1 at $DIR/generator-tiny.rs:22:13: 22:21
-        _8 = const callee() -> bb4;      // scope 1 at $DIR/generator-tiny.rs:22:13: 22:21
+        StorageDead(_7);                 // scope 1 at $DIR/generator-tiny.rs:22:17: 22:18
+        StorageDead(_6);                 // scope 1 at $DIR/generator-tiny.rs:22:18: 22:19
+        StorageLive(_8);                 // scope 1 at $DIR/generator-tiny.rs:23:13: 23:21
+        _8 = const callee() -> bb4;      // scope 1 at $DIR/generator-tiny.rs:23:13: 23:21
                                          // ty::Const
                                          // + ty: fn() {callee}
                                          // + val: Value(Scalar(<ZST>))
                                          // mir::Constant
-                                         // + span: $DIR/generator-tiny.rs:22:13: 22:19
+                                         // + span: $DIR/generator-tiny.rs:23:13: 23:19
                                          // + literal: Const { ty: fn() {callee}, val: Value(Scalar(<ZST>)) }
     }
 
     bb4: {
-        StorageDead(_8);                 // scope 1 at $DIR/generator-tiny.rs:22:21: 22:22
-        _5 = const ();                   // scope 1 at $DIR/generator-tiny.rs:20:14: 23:10
+        StorageDead(_8);                 // scope 1 at $DIR/generator-tiny.rs:23:21: 23:22
+        _5 = const ();                   // scope 1 at $DIR/generator-tiny.rs:21:14: 24:10
                                          // ty::Const
                                          // + ty: ()
                                          // + val: Value(Scalar(<ZST>))
                                          // mir::Constant
-                                         // + span: $DIR/generator-tiny.rs:20:14: 23:10
+                                         // + span: $DIR/generator-tiny.rs:21:14: 24:10
                                          // + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
-        goto -> bb2;                     // scope 1 at $DIR/generator-tiny.rs:20:9: 23:10
+        goto -> bb2;                     // scope 1 at $DIR/generator-tiny.rs:21:9: 24:10
     }
 
     bb5: {
-        StorageLive(_4);                 // scope 0 at $DIR/generator-tiny.rs:18:16: 24:6
-        StorageLive(_6);                 // scope 0 at $DIR/generator-tiny.rs:18:16: 24:6
-        StorageLive(_7);                 // scope 0 at $DIR/generator-tiny.rs:18:16: 24:6
-        _6 = move _2;                    // scope 0 at $DIR/generator-tiny.rs:18:16: 24:6
-        goto -> bb3;                     // scope 0 at $DIR/generator-tiny.rs:18:16: 24:6
+        StorageLive(_4);                 // scope 0 at $DIR/generator-tiny.rs:19:16: 25:6
+        StorageLive(_6);                 // scope 0 at $DIR/generator-tiny.rs:19:16: 25:6
+        StorageLive(_7);                 // scope 0 at $DIR/generator-tiny.rs:19:16: 25:6
+        _6 = move _2;                    // scope 0 at $DIR/generator-tiny.rs:19:16: 25:6
+        goto -> bb3;                     // scope 0 at $DIR/generator-tiny.rs:19:16: 25:6
     }
 
     bb6: {
-        unreachable;                     // scope 0 at $DIR/generator-tiny.rs:18:16: 24:6
+        unreachable;                     // scope 0 at $DIR/generator-tiny.rs:19:16: 25:6
     }
 }