Auto merge of #122338 - workingjubilee:rollup-xzpt4v4, r=workingjubilee

Rollup of 15 pull requests

Successful merges:

 - #116791 (Allow codegen backends to opt-out of parallel codegen)
 - #116793 (Allow targets to override default codegen backend)
 - #117458 (LLVM Bitcode Linker: A self contained linker for nvptx and other targets)
 - #119385 (Fix type resolution of associated const equality bounds (take 2))
 - #121438 (std support for wasm32 panic=unwind)
 - #121893 (Add tests (and a bit of cleanup) for interior mut handling in promotion and const-checking)
 - #122080 (Clarity improvements to `DropTree`)
 - #122152 (Improve diagnostics for parenthesized type arguments)
 - #122166 (Remove the unused `field_remapping` field from `TypeLowering`)
 - #122249 (interpret: do not call machine read hooks during validation)
 - #122299 (Store backtrace for `must_produce_diag`)
 - #122318 (Revision-related tweaks for next-solver tests)
 - #122320 (Use ptradd for vtable indexing)
 - #122328 (unix_sigpipe: Replace `inherit` with `sig_dfl` in syntax tests)
 - #122330 (bootstrap readme: fix, improve, update)

r? `@ghost`
`@rustbot` modify labels: rollup

7 files changed, 151 insertions, 23 deletions

diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index fcb3602b734..e70cc9b6216 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -24,6 +24,7 @@ use rustc_span::symbol::Symbol;
 use rustc_target::spec::crt_objects::CrtObjects;
 use rustc_target::spec::LinkSelfContainedComponents;
 use rustc_target::spec::LinkSelfContainedDefault;
+use rustc_target::spec::LinkerFlavorCli;
 use rustc_target::spec::{Cc, LinkOutputKind, LinkerFlavor, Lld, PanicStrategy};
 use rustc_target::spec::{RelocModel, RelroLevel, SanitizerSet, SplitDebuginfo};
 
@@ -1350,6 +1351,7 @@ pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
                         }
                     }
                     LinkerFlavor::Bpf => "bpf-linker",
+                    LinkerFlavor::Llbc => "llvm-bitcode-linker",
                     LinkerFlavor::Ptx => "rust-ptx-linker",
                 }),
                 flavor,
@@ -1367,8 +1369,17 @@ pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
 
     // linker and linker flavor specified via command line have precedence over what the target
     // specification specifies
-    let linker_flavor =
-        sess.opts.cg.linker_flavor.map(|flavor| sess.target.linker_flavor.with_cli_hints(flavor));
+    let linker_flavor = match sess.opts.cg.linker_flavor {
+        // The linker flavors that are non-target specific can be directly translated to LinkerFlavor
+        Some(LinkerFlavorCli::Llbc) => Some(LinkerFlavor::Llbc),
+        Some(LinkerFlavorCli::Ptx) => Some(LinkerFlavor::Ptx),
+        // The linker flavors that corresponds to targets needs logic that keeps the base LinkerFlavor
+        _ => sess
+            .opts
+            .cg
+            .linker_flavor
+            .map(|flavor| sess.target.linker_flavor.with_cli_hints(flavor)),
+    };
     if let Some(ret) = infer_from(sess, sess.opts.cg.linker.clone(), linker_flavor) {
         return ret;
     }
@@ -2338,8 +2349,12 @@ fn add_order_independent_options(
         });
     }
 
-    if flavor == LinkerFlavor::Ptx {
-        // Provide the linker with fallback to internal `target-cpu`.
+    if flavor == LinkerFlavor::Llbc {
+        cmd.arg("--target");
+        cmd.arg(sess.target.llvm_target.as_ref());
+        cmd.arg("--target-cpu");
+        cmd.arg(&codegen_results.crate_info.target_cpu);
+    } else if flavor == LinkerFlavor::Ptx {
         cmd.arg("--fallback-arch");
         cmd.arg(&codegen_results.crate_info.target_cpu);
     } else if flavor == LinkerFlavor::Bpf {
diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs
index e52efd86955..b4e054417f3 100644
--- a/compiler/rustc_codegen_ssa/src/back/linker.rs
+++ b/compiler/rustc_codegen_ssa/src/back/linker.rs
@@ -153,6 +153,7 @@ pub fn get_linker<'a>(
         LinkerFlavor::Msvc(..) => Box::new(MsvcLinker { cmd, sess }) as Box<dyn Linker>,
         LinkerFlavor::EmCc => Box::new(EmLinker { cmd, sess }) as Box<dyn Linker>,
         LinkerFlavor::Bpf => Box::new(BpfLinker { cmd, sess }) as Box<dyn Linker>,
+        LinkerFlavor::Llbc => Box::new(LlbcLinker { cmd, sess }) as Box<dyn Linker>,
         LinkerFlavor::Ptx => Box::new(PtxLinker { cmd, sess }) as Box<dyn Linker>,
     }
 }
@@ -1824,7 +1825,7 @@ impl<'a> Linker for PtxLinker<'a> {
             }
 
             Lto::No => {}
-        };
+        }
     }
 
     fn output_filename(&mut self, path: &Path) {
@@ -1862,6 +1863,104 @@ impl<'a> Linker for PtxLinker<'a> {
     fn linker_plugin_lto(&mut self) {}
 }
 
+/// The `self-contained` LLVM bitcode linker
+pub struct LlbcLinker<'a> {
+    cmd: Command,
+    sess: &'a Session,
+}
+
+impl<'a> Linker for LlbcLinker<'a> {
+    fn cmd(&mut self) -> &mut Command {
+        &mut self.cmd
+    }
+
+    fn set_output_kind(&mut self, _output_kind: LinkOutputKind, _out_filename: &Path) {}
+
+    fn link_dylib_by_name(&mut self, _name: &str, _verbatim: bool, _as_needed: bool) {
+        panic!("external dylibs not supported")
+    }
+
+    fn link_staticlib_by_name(
+        &mut self,
+        _name: &str,
+        _verbatim: bool,
+        _whole_archive: bool,
+        _search_paths: &SearchPaths,
+    ) {
+        panic!("staticlibs not supported")
+    }
+
+    fn link_staticlib_by_path(&mut self, path: &Path, _whole_archive: bool) {
+        self.cmd.arg(path);
+    }
+
+    fn include_path(&mut self, path: &Path) {
+        self.cmd.arg("-L").arg(path);
+    }
+
+    fn debuginfo(&mut self, _strip: Strip, _: &[PathBuf]) {
+        self.cmd.arg("--debug");
+    }
+
+    fn add_object(&mut self, path: &Path) {
+        self.cmd.arg(path);
+    }
+
+    fn optimize(&mut self) {
+        match self.sess.opts.optimize {
+            OptLevel::No => "-O0",
+            OptLevel::Less => "-O1",
+            OptLevel::Default => "-O2",
+            OptLevel::Aggressive => "-O3",
+            OptLevel::Size => "-Os",
+            OptLevel::SizeMin => "-Oz",
+        };
+    }
+
+    fn output_filename(&mut self, path: &Path) {
+        self.cmd.arg("-o").arg(path);
+    }
+
+    fn framework_path(&mut self, _path: &Path) {
+        panic!("frameworks not supported")
+    }
+
+    fn full_relro(&mut self) {}
+
+    fn partial_relro(&mut self) {}
+
+    fn no_relro(&mut self) {}
+
+    fn gc_sections(&mut self, _keep_metadata: bool) {}
+
+    fn no_gc_sections(&mut self) {}
+
+    fn pgo_gen(&mut self) {}
+
+    fn no_crt_objects(&mut self) {}
+
+    fn no_default_libraries(&mut self) {}
+
+    fn control_flow_guard(&mut self) {}
+
+    fn ehcont_guard(&mut self) {}
+
+    fn export_symbols(&mut self, _tmpdir: &Path, _crate_type: CrateType, symbols: &[String]) {
+        match _crate_type {
+            CrateType::Cdylib => {
+                for sym in symbols {
+                    self.cmd.arg("--export-symbol").arg(sym);
+                }
+            }
+            _ => (),
+        }
+    }
+
+    fn subsystem(&mut self, _subsystem: &str) {}
+
+    fn linker_plugin_lto(&mut self) {}
+}
+
 pub struct BpfLinker<'a> {
     cmd: Command,
     sess: &'a Session,
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index bbb04652119..4eda4c2f08c 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -374,6 +374,10 @@ pub struct CodegenContext<B: WriteBackendMethods> {
     pub incr_comp_session_dir: Option<PathBuf>,
     /// Channel back to the main control thread to send messages to
     pub coordinator_send: Sender<Box<dyn Any + Send>>,
+    /// `true` if the codegen should be run in parallel.
+    ///
+    /// Depends on [`CodegenBackend::supports_parallel()`] and `-Zno_parallel_backend`.
+    pub parallel: bool,
 }
 
 impl<B: WriteBackendMethods> CodegenContext<B> {
@@ -1152,6 +1156,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
         target_arch: tcx.sess.target.arch.to_string(),
         split_debuginfo: tcx.sess.split_debuginfo(),
         split_dwarf_kind: tcx.sess.opts.unstable_opts.split_dwarf_kind,
+        parallel: backend.supports_parallel() && !sess.opts.unstable_opts.no_parallel_backend,
     };
 
     // This is the "main loop" of parallel work happening for parallel codegen.
@@ -1422,7 +1427,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
                             .binary_search_by_key(&cost, |&(_, cost)| cost)
                             .unwrap_or_else(|e| e);
                         work_items.insert(insertion_index, (work, cost));
-                        if !cgcx.opts.unstable_opts.no_parallel_llvm {
+                        if cgcx.parallel {
                             helper.request_token();
                         }
                     }
@@ -1545,7 +1550,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
                     };
                     work_items.insert(insertion_index, (llvm_work_item, cost));
 
-                    if !cgcx.opts.unstable_opts.no_parallel_llvm {
+                    if cgcx.parallel {
                         helper.request_token();
                     }
                     assert_eq!(main_thread_state, MainThreadState::Codegenning);
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 5cba14a5dda..c316d19e041 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -165,14 +165,11 @@ pub fn unsized_info<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                 cx.tcx().vtable_trait_upcasting_coercion_new_vptr_slot((source, target));
 
             if let Some(entry_idx) = vptr_entry_idx {
-                let ptr_ty = cx.type_ptr();
-                let ptr_align = cx.tcx().data_layout.pointer_align.abi;
-                let gep = bx.inbounds_gep(
-                    ptr_ty,
-                    old_info,
-                    &[bx.const_usize(u64::try_from(entry_idx).unwrap())],
-                );
-                let new_vptr = bx.load(ptr_ty, gep, ptr_align);
+                let ptr_size = bx.data_layout().pointer_size;
+                let ptr_align = bx.data_layout().pointer_align.abi;
+                let vtable_byte_offset = u64::try_from(entry_idx).unwrap() * ptr_size.bytes();
+                let gep = bx.inbounds_ptradd(old_info, bx.const_usize(vtable_byte_offset));
+                let new_vptr = bx.load(bx.type_ptr(), gep, ptr_align);
                 bx.nonnull_metadata(new_vptr);
                 // VTable loads are invariant.
                 bx.set_invariant_load(new_vptr);
diff --git a/compiler/rustc_codegen_ssa/src/meth.rs b/compiler/rustc_codegen_ssa/src/meth.rs
index 12146a54d3b..4f7dc9968a1 100644
--- a/compiler/rustc_codegen_ssa/src/meth.rs
+++ b/compiler/rustc_codegen_ssa/src/meth.rs
@@ -20,9 +20,13 @@ impl<'a, 'tcx> VirtualIndex {
         ty: Ty<'tcx>,
         fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
     ) -> Bx::Value {
-        // Load the data pointer from the object.
+        // Load the function pointer from the object.
         debug!("get_fn({llvtable:?}, {ty:?}, {self:?})");
+
         let llty = bx.fn_ptr_backend_type(fn_abi);
+        let ptr_size = bx.data_layout().pointer_size;
+        let ptr_align = bx.data_layout().pointer_align.abi;
+        let vtable_byte_offset = self.0 * ptr_size.bytes();
 
         if bx.cx().sess().opts.unstable_opts.virtual_function_elimination
             && bx.cx().sess().lto() == Lto::Fat
@@ -30,12 +34,10 @@ impl<'a, 'tcx> VirtualIndex {
             let typeid = bx
                 .typeid_metadata(typeid_for_trait_ref(bx.tcx(), expect_dyn_trait_in_self(ty)))
                 .unwrap();
-            let vtable_byte_offset = self.0 * bx.data_layout().pointer_size.bytes();
             let func = bx.type_checked_load(llvtable, vtable_byte_offset, typeid);
             func
         } else {
-            let ptr_align = bx.tcx().data_layout.pointer_align.abi;
-            let gep = bx.inbounds_gep(llty, llvtable, &[bx.const_usize(self.0)]);
+            let gep = bx.inbounds_ptradd(llvtable, bx.const_usize(vtable_byte_offset));
             let ptr = bx.load(llty, gep, ptr_align);
             bx.nonnull_metadata(ptr);
             // VTable loads are invariant.
@@ -53,9 +55,12 @@ impl<'a, 'tcx> VirtualIndex {
         debug!("get_int({:?}, {:?})", llvtable, self);
 
         let llty = bx.type_isize();
-        let usize_align = bx.tcx().data_layout.pointer_align.abi;
-        let gep = bx.inbounds_gep(llty, llvtable, &[bx.const_usize(self.0)]);
-        let ptr = bx.load(llty, gep, usize_align);
+        let ptr_size = bx.data_layout().pointer_size;
+        let ptr_align = bx.data_layout().pointer_align.abi;
+        let vtable_byte_offset = self.0 * ptr_size.bytes();
+
+        let gep = bx.inbounds_ptradd(llvtable, bx.const_usize(vtable_byte_offset));
+        let ptr = bx.load(llty, gep, ptr_align);
         // VTable loads are invariant.
         bx.set_invariant_load(ptr);
         ptr
diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs
index 89a44d2897a..d3f5de25d9a 100644
--- a/compiler/rustc_codegen_ssa/src/mir/block.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/block.rs
@@ -1597,7 +1597,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         let funclet;
         let llbb;
         let mut bx;
-        if base::wants_msvc_seh(self.cx.sess()) {
+        if base::wants_new_eh_instructions(self.cx.sess()) {
             // This is a basic block that we're aborting the program for,
             // notably in an `extern` function. These basic blocks are inserted
             // so that we assert that `extern` functions do indeed not panic,
diff --git a/compiler/rustc_codegen_ssa/src/traits/backend.rs b/compiler/rustc_codegen_ssa/src/traits/backend.rs
index cb1feff1336..e6d42c596d2 100644
--- a/compiler/rustc_codegen_ssa/src/traits/backend.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/backend.rs
@@ -111,6 +111,13 @@ pub trait CodegenBackend {
         codegen_results: CodegenResults,
         outputs: &OutputFilenames,
     ) -> Result<(), ErrorGuaranteed>;
+
+    /// Returns `true` if this backend can be safely called from multiple threads.
+    ///
+    /// Defaults to `true`.
+    fn supports_parallel(&self) -> bool {
+        true
+    }
 }
 
 pub trait ExtraBackendMethods: