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

Cargo.lock

@@ -2265,6 +2265,17 @@ checksum = "f9d642685b028806386b2b6e75685faadd3eb65a85fff7df711ce18446a422da"
 name = "lld-wrapper"
 version = "0.1.0"
 
+[[package]]
+name = "llvm-bitcode-linker"
+version = "0.0.1"
+dependencies = [
+ "anyhow",
+ "clap",
+ "thiserror",
+ "tracing",
+ "tracing-subscriber",
+]
+
 [[package]]
 name = "lock_api"
 version = "0.4.11"

Cargo.toml

@@ -34,6 +34,7 @@ members = [
   "src/tools/expand-yaml-anchors",
   "src/tools/jsondocck",
   "src/tools/jsondoclint",
+  "src/tools/llvm-bitcode-linker",
   "src/tools/html-checker",
   "src/tools/bump-stage0",
   "src/tools/replace-version-placeholder",

compiler/rustc_codegen_llvm/src/context.rs

@@ -77,8 +77,8 @@ pub struct CodegenCx<'ll, 'tcx> {
     /// See <https://llvm.org/docs/LangRef.html#the-llvm-compiler-used-global-variable> for details
     pub compiler_used_statics: RefCell<Vec<&'ll Value>>,
 
-    /// Mapping of non-scalar types to llvm types and field remapping if needed.
-    pub type_lowering: RefCell<FxHashMap<(Ty<'tcx>, Option<VariantIdx>), TypeLowering<'ll>>>,
+    /// Mapping of non-scalar types to llvm types.
+    pub type_lowering: RefCell<FxHashMap<(Ty<'tcx>, Option<VariantIdx>), &'ll Type>>,
 
     /// Mapping of scalar types to llvm types.
     pub scalar_lltypes: RefCell<FxHashMap<Ty<'tcx>, &'ll Type>>,
@@ -105,15 +105,6 @@ pub struct CodegenCx<'ll, 'tcx> {
     pub renamed_statics: RefCell<FxHashMap<DefId, &'ll Value>>,
 }
 
-pub struct TypeLowering<'ll> {
-    /// Associated LLVM type
-    pub lltype: &'ll Type,
-
-    /// If padding is used the slice maps fields from source order
-    /// to llvm order.
-    pub field_remapping: Option<SmallVec<[u32; 4]>>,
-}
-
 fn to_llvm_tls_model(tls_model: TlsModel) -> llvm::ThreadLocalMode {
     match tls_model {
         TlsModel::GeneralDynamic => llvm::ThreadLocalMode::GeneralDynamic,

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -5,6 +5,7 @@ use crate::errors::{
 };
 use crate::llvm;
 use libc::c_int;
+use rustc_codegen_ssa::base::wants_wasm_eh;
 use rustc_codegen_ssa::traits::PrintBackendInfo;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::small_c_str::SmallCStr;
@@ -98,6 +99,10 @@ unsafe fn configure_llvm(sess: &Session) {
             }
         }
 
+        if wants_wasm_eh(sess) {
+            add("-wasm-enable-eh", false);
+        }
+
         if sess.target.os == "emscripten" && sess.panic_strategy() == PanicStrategy::Unwind {
             add("-enable-emscripten-cxx-exceptions", false);
         }
@@ -523,6 +528,10 @@ pub(crate) fn global_llvm_features(sess: &Session, diagnostics: bool) -> Vec<Str
             .map(String::from),
     );
 
+    if wants_wasm_eh(sess) && sess.panic_strategy() == PanicStrategy::Unwind {
+        features.push("+exception-handling".into());
+    }
+
     // -Ctarget-features
     let supported_features = sess.target.supported_target_features();
     let mut featsmap = FxHashMap::default();

compiler/rustc_codegen_llvm/src/type_of.rs

@@ -1,5 +1,4 @@
 use crate::common::*;
-use crate::context::TypeLowering;
 use crate::type_::Type;
 use rustc_codegen_ssa::traits::*;
 use rustc_middle::bug;
@@ -10,15 +9,13 @@ use rustc_target::abi::HasDataLayout;
 use rustc_target::abi::{Abi, Align, FieldsShape};
 use rustc_target::abi::{Int, Pointer, F128, F16, F32, F64};
 use rustc_target::abi::{Scalar, Size, Variants};
-use smallvec::{smallvec, SmallVec};
 
 use std::fmt::Write;
 
 fn uncached_llvm_type<'a, 'tcx>(
     cx: &CodegenCx<'a, 'tcx>,
     layout: TyAndLayout<'tcx>,
     defer: &mut Option<(&'a Type, TyAndLayout<'tcx>)>,
-    field_remapping: &mut Option<SmallVec<[u32; 4]>>,
 ) -> &'a Type {
     match layout.abi {
         Abi::Scalar(_) => bug!("handled elsewhere"),
@@ -71,8 +68,7 @@ fn uncached_llvm_type<'a, 'tcx>(
         FieldsShape::Array { count, .. } => cx.type_array(layout.field(cx, 0).llvm_type(cx), count),
         FieldsShape::Arbitrary { .. } => match name {
             None => {
-                let (llfields, packed, new_field_remapping) = struct_llfields(cx, layout);
-                *field_remapping = new_field_remapping;
+                let (llfields, packed) = struct_llfields(cx, layout);
                 cx.type_struct(&llfields, packed)
             }
             Some(ref name) => {
@@ -87,15 +83,14 @@ fn uncached_llvm_type<'a, 'tcx>(
 fn struct_llfields<'a, 'tcx>(
     cx: &CodegenCx<'a, 'tcx>,
     layout: TyAndLayout<'tcx>,
-) -> (Vec<&'a Type>, bool, Option<SmallVec<[u32; 4]>>) {
+) -> (Vec<&'a Type>, bool) {
     debug!("struct_llfields: {:#?}", layout);
     let field_count = layout.fields.count();
 
     let mut packed = false;
     let mut offset = Size::ZERO;
     let mut prev_effective_align = layout.align.abi;
     let mut result: Vec<_> = Vec::with_capacity(1 + field_count * 2);
-    let mut field_remapping = smallvec![0; field_count];
     for i in layout.fields.index_by_increasing_offset() {
         let target_offset = layout.fields.offset(i as usize);
         let field = layout.field(cx, i);
@@ -120,12 +115,10 @@ fn struct_llfields<'a, 'tcx>(
             result.push(cx.type_padding_filler(padding, padding_align));
             debug!("    padding before: {:?}", padding);
         }
-        field_remapping[i] = result.len() as u32;
         result.push(field.llvm_type(cx));
         offset = target_offset + field.size;
         prev_effective_align = effective_field_align;
     }
-    let padding_used = result.len() > field_count;
     if layout.is_sized() && field_count > 0 {
         if offset > layout.size {
             bug!("layout: {:#?} stride: {:?} offset: {:?}", layout, layout.size, offset);
@@ -143,8 +136,7 @@ fn struct_llfields<'a, 'tcx>(
     } else {
         debug!("struct_llfields: offset: {:?} stride: {:?}", offset, layout.size);
     }
-    let field_remapping = padding_used.then_some(field_remapping);
-    (result, packed, field_remapping)
+    (result, packed)
 }
 
 impl<'a, 'tcx> CodegenCx<'a, 'tcx> {
@@ -224,7 +216,7 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
             _ => None,
         };
         if let Some(llty) = cx.type_lowering.borrow().get(&(self.ty, variant_index)) {
-            return llty.lltype;
+            return llty;
         }
 
         debug!("llvm_type({:#?})", self);
@@ -236,30 +228,22 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
         let normal_ty = cx.tcx.erase_regions(self.ty);
 
         let mut defer = None;
-        let mut field_remapping = None;
         let llty = if self.ty != normal_ty {
             let mut layout = cx.layout_of(normal_ty);
             if let Some(v) = variant_index {
                 layout = layout.for_variant(cx, v);
             }
             layout.llvm_type(cx)
         } else {
-            uncached_llvm_type(cx, *self, &mut defer, &mut field_remapping)
+            uncached_llvm_type(cx, *self, &mut defer)
         };
         debug!("--> mapped {:#?} to llty={:?}", self, llty);
 
-        cx.type_lowering
-            .borrow_mut()
-            .insert((self.ty, variant_index), TypeLowering { lltype: llty, field_remapping });
+        cx.type_lowering.borrow_mut().insert((self.ty, variant_index), llty);
 
         if let Some((llty, layout)) = defer {
-            let (llfields, packed, new_field_remapping) = struct_llfields(cx, layout);
+            let (llfields, packed) = struct_llfields(cx, layout);
             cx.set_struct_body(llty, &llfields, packed);
-            cx.type_lowering
-                .borrow_mut()
-                .get_mut(&(self.ty, variant_index))
-                .unwrap()
-                .field_remapping = new_field_remapping;
         }
         llty
     }

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 {

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,