Auto merge of #132762 - Zalathar:rollup-qfgz165, r=Zalathar

Rollup of 5 pull requests

Successful merges:

 - #132161 ([StableMIR] A few fixes to pretty printing)
 - #132389 (coverage: Simplify parts of coverage graph creation)
 - #132452 (coverage: Extract safe FFI wrapper functions to `llvm_cov`)
 - #132590 (Simplify FFI calls for `-Ztime-llvm-passes` and `-Zprint-codegen-stats`)
 - #132738 (Initialize channel `Block`s directly on the heap)

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

compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs

@@ -0,0 +1,100 @@
+//! Safe wrappers for coverage-specific FFI functions.
+
+use std::ffi::CString;
+
+use crate::common::AsCCharPtr;
+use crate::coverageinfo::ffi;
+use crate::llvm;
+
+pub(crate) fn covmap_var_name() -> CString {
+    CString::new(llvm::build_byte_buffer(|s| unsafe {
+        llvm::LLVMRustCoverageWriteCovmapVarNameToString(s);
+    }))
+    .expect("covmap variable name should not contain NUL")
+}
+
+pub(crate) fn covmap_section_name(llmod: &llvm::Module) -> CString {
+    CString::new(llvm::build_byte_buffer(|s| unsafe {
+        llvm::LLVMRustCoverageWriteCovmapSectionNameToString(llmod, s);
+    }))
+    .expect("covmap section name should not contain NUL")
+}
+
+pub(crate) fn covfun_section_name(llmod: &llvm::Module) -> CString {
+    CString::new(llvm::build_byte_buffer(|s| unsafe {
+        llvm::LLVMRustCoverageWriteCovfunSectionNameToString(llmod, s);
+    }))
+    .expect("covfun section name should not contain NUL")
+}
+
+pub(crate) fn create_pgo_func_name_var<'ll>(
+    llfn: &'ll llvm::Value,
+    mangled_fn_name: &str,
+) -> &'ll llvm::Value {
+    unsafe {
+        llvm::LLVMRustCoverageCreatePGOFuncNameVar(
+            llfn,
+            mangled_fn_name.as_c_char_ptr(),
+            mangled_fn_name.len(),
+        )
+    }
+}
+
+pub(crate) fn write_filenames_to_buffer<'a>(
+    filenames: impl IntoIterator<Item = &'a str>,
+) -> Vec<u8> {
+    let (pointers, lengths) = filenames
+        .into_iter()
+        .map(|s: &str| (s.as_c_char_ptr(), s.len()))
+        .unzip::<_, _, Vec<_>, Vec<_>>();
+
+    llvm::build_byte_buffer(|buffer| unsafe {
+        llvm::LLVMRustCoverageWriteFilenamesToBuffer(
+            pointers.as_ptr(),
+            pointers.len(),
+            lengths.as_ptr(),
+            lengths.len(),
+            buffer,
+        );
+    })
+}
+
+pub(crate) fn write_function_mappings_to_buffer(
+    virtual_file_mapping: &[u32],
+    expressions: &[ffi::CounterExpression],
+    code_regions: &[ffi::CodeRegion],
+    branch_regions: &[ffi::BranchRegion],
+    mcdc_branch_regions: &[ffi::MCDCBranchRegion],
+    mcdc_decision_regions: &[ffi::MCDCDecisionRegion],
+) -> Vec<u8> {
+    llvm::build_byte_buffer(|buffer| unsafe {
+        llvm::LLVMRustCoverageWriteFunctionMappingsToBuffer(
+            virtual_file_mapping.as_ptr(),
+            virtual_file_mapping.len(),
+            expressions.as_ptr(),
+            expressions.len(),
+            code_regions.as_ptr(),
+            code_regions.len(),
+            branch_regions.as_ptr(),
+            branch_regions.len(),
+            mcdc_branch_regions.as_ptr(),
+            mcdc_branch_regions.len(),
+            mcdc_decision_regions.as_ptr(),
+            mcdc_decision_regions.len(),
+            buffer,
+        )
+    })
+}
+
+/// Hashes some bytes into a 64-bit hash, via LLVM's `IndexedInstrProf::ComputeHash`,
+/// as required for parts of the LLVM coverage mapping format.
+pub(crate) fn hash_bytes(bytes: &[u8]) -> u64 {
+    unsafe { llvm::LLVMRustCoverageHashBytes(bytes.as_c_char_ptr(), bytes.len()) }
+}
+
+/// Returns LLVM's `coverage::CovMapVersion::CurrentVersion` (CoverageMapping.h)
+/// as a raw numeric value. For historical reasons, the numeric value is 1 less
+/// than the number in the version's name, so `Version7` is actually `6u32`.
+pub(crate) fn mapping_version() -> u32 {
+    unsafe { llvm::LLVMRustCoverageMappingVersion() }
+}

compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs

@@ -1,4 +1,5 @@
 use std::ffi::CString;
+use std::iter;
 
 use itertools::Itertools as _;
 use rustc_abi::Align;
@@ -17,9 +18,9 @@
 use tracing::debug;
 
 use crate::common::CodegenCx;
-use crate::coverageinfo::ffi;
 use crate::coverageinfo::map_data::{FunctionCoverage, FunctionCoverageCollector};
-use crate::{coverageinfo, llvm};
+use crate::coverageinfo::{ffi, llvm_cov};
+use crate::llvm;
 
 /// Generates and exports the coverage map, which is embedded in special
 /// linker sections in the final binary.
@@ -33,7 +34,7 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
     // agrees with our Rust-side code. Expected versions (encoded as n-1) are:
     // - `CovMapVersion::Version7` (6) used by LLVM 18-19
     let covmap_version = {
-        let llvm_covmap_version = coverageinfo::mapping_version();
+        let llvm_covmap_version = llvm_cov::mapping_version();
         let expected_versions = 6..=6;
         assert!(
             expected_versions.contains(&llvm_covmap_version),
@@ -78,7 +79,7 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
 
     let filenames_size = filenames_buffer.len();
     let filenames_val = cx.const_bytes(&filenames_buffer);
-    let filenames_ref = coverageinfo::hash_bytes(&filenames_buffer);
+    let filenames_ref = llvm_cov::hash_bytes(&filenames_buffer);
 
     // Generate the coverage map header, which contains the filenames used by
     // this CGU's coverage mappings, and store it in a well-known global.
@@ -187,13 +188,10 @@ fn make_filenames_buffer(&self, tcx: TyCtxt<'_>) -> Vec<u8> {
             .for_scope(tcx.sess, RemapPathScopeComponents::MACRO)
             .to_string_lossy();
 
-        llvm::build_byte_buffer(|buffer| {
+        // Insert the working dir at index 0, before the other filenames.
-            coverageinfo::write_filenames_section_to_buffer(
+        let filenames =
-                // Insert the working dir at index 0, before the other filenames.
+            iter::once(working_dir).chain(self.raw_file_table.iter().map(Symbol::as_str));
-                std::iter::once(working_dir).chain(self.raw_file_table.iter().map(Symbol::as_str)),
+        llvm_cov::write_filenames_to_buffer(filenames)
-                buffer,
-            );
-        })
     }
 }
 
@@ -296,17 +294,14 @@ fn encode_mappings_for_function(
     }
 
     // Encode the function's coverage mappings into a buffer.
-    llvm::build_byte_buffer(|buffer| {
+    llvm_cov::write_function_mappings_to_buffer(
-        coverageinfo::write_mapping_to_buffer(
+        &virtual_file_mapping.into_vec(),
-            virtual_file_mapping.into_vec(),
+        &expressions,
-            expressions,
+        &code_regions,
-            &code_regions,
+        &branch_regions,
-            &branch_regions,
+        &mcdc_branch_regions,
-            &mcdc_branch_regions,
+        &mcdc_decision_regions,
-            &mcdc_decision_regions,
+    )
-            buffer,
-        );
-    })
 }
 
 /// Generates the contents of the covmap record for this CGU, which mostly
@@ -335,23 +330,11 @@ fn generate_covmap_record<'ll>(
     let covmap_data =
         cx.const_struct(&[cov_data_header_val, filenames_val], /*packed=*/ false);
 
-    let covmap_var_name = CString::new(llvm::build_byte_buffer(|s| unsafe {
+    let llglobal = llvm::add_global(cx.llmod, cx.val_ty(covmap_data), &llvm_cov::covmap_var_name());
-        llvm::LLVMRustCoverageWriteMappingVarNameToString(s);
-    }))
-    .unwrap();
-    debug!("covmap var name: {:?}", covmap_var_name);
-
-    let covmap_section_name = CString::new(llvm::build_byte_buffer(|s| unsafe {
-        llvm::LLVMRustCoverageWriteMapSectionNameToString(cx.llmod, s);
-    }))
-    .expect("covmap section name should not contain NUL");
-    debug!("covmap section name: {:?}", covmap_section_name);
-
-    let llglobal = llvm::add_global(cx.llmod, cx.val_ty(covmap_data), &covmap_var_name);
     llvm::set_initializer(llglobal, covmap_data);
     llvm::set_global_constant(llglobal, true);
     llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
-    llvm::set_section(llglobal, &covmap_section_name);
+    llvm::set_section(llglobal, &llvm_cov::covmap_section_name(cx.llmod));
     // LLVM's coverage mapping format specifies 8-byte alignment for items in this section.
     // <https://llvm.org/docs/CoverageMappingFormat.html>
     llvm::set_alignment(llglobal, Align::EIGHT);
@@ -373,7 +356,7 @@ fn generate_covfun_record(
     let coverage_mapping_size = coverage_mapping_buffer.len();
     let coverage_mapping_val = cx.const_bytes(&coverage_mapping_buffer);
 
-    let func_name_hash = coverageinfo::hash_bytes(mangled_function_name.as_bytes());
+    let func_name_hash = llvm_cov::hash_bytes(mangled_function_name.as_bytes());
     let func_name_hash_val = cx.const_u64(func_name_hash);
     let coverage_mapping_size_val = cx.const_u32(coverage_mapping_size as u32);
     let source_hash_val = cx.const_u64(source_hash);

compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs

@@ -1,24 +1,23 @@
 use std::cell::{OnceCell, RefCell};
 use std::ffi::{CStr, CString};
 
-use libc::c_uint;
 use rustc_abi::Size;
 use rustc_codegen_ssa::traits::{
     BuilderMethods, ConstCodegenMethods, CoverageInfoBuilderMethods, MiscCodegenMethods,
 };
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
-use rustc_llvm::RustString;
 use rustc_middle::mir::coverage::CoverageKind;
 use rustc_middle::ty::Instance;
 use rustc_middle::ty::layout::HasTyCtxt;
 use tracing::{debug, instrument};
 
 use crate::builder::Builder;
-use crate::common::{AsCCharPtr, CodegenCx};
+use crate::common::CodegenCx;
 use crate::coverageinfo::map_data::FunctionCoverageCollector;
 use crate::llvm;
 
 pub(crate) mod ffi;
+mod llvm_cov;
 pub(crate) mod map_data;
 mod mapgen;
 
@@ -80,12 +79,9 @@ pub(crate) fn coverageinfo_finalize(&self) {
     /// - `__LLVM_COV,__llvm_covfun` on macOS (includes `__LLVM_COV,` segment prefix)
     /// - `.lcovfun$M` on Windows (includes `$M` sorting suffix)
     fn covfun_section_name(&self) -> &CStr {
-        self.coverage_cx().covfun_section_name.get_or_init(|| {
+        self.coverage_cx()
-            CString::new(llvm::build_byte_buffer(|s| unsafe {
+            .covfun_section_name
-                llvm::LLVMRustCoverageWriteFuncSectionNameToString(self.llmod, s);
+            .get_or_init(|| llvm_cov::covfun_section_name(self.llmod))
-            }))
-            .expect("covfun section name should not contain NUL")
-        })
     }
 
     /// For LLVM codegen, returns a function-specific `Value` for a global
@@ -95,9 +91,11 @@ fn covfun_section_name(&self) -> &CStr {
     fn get_pgo_func_name_var(&self, instance: Instance<'tcx>) -> &'ll llvm::Value {
         debug!("getting pgo_func_name_var for instance={:?}", instance);
         let mut pgo_func_name_var_map = self.coverage_cx().pgo_func_name_var_map.borrow_mut();
-        pgo_func_name_var_map
+        pgo_func_name_var_map.entry(instance).or_insert_with(|| {
-            .entry(instance)
+            let llfn = self.get_fn(instance);
-            .or_insert_with(|| create_pgo_func_name_var(self, instance))
+            let mangled_fn_name: &str = self.tcx.symbol_name(instance).name;
+            llvm_cov::create_pgo_func_name_var(llfn, mangled_fn_name)
+        })
     }
 }
 
@@ -225,80 +223,3 @@ fn add_coverage(&mut self, instance: Instance<'tcx>, kind: &CoverageKind) {
         }
     }
 }
-
-/// Calls llvm::createPGOFuncNameVar() with the given function instance's
-/// mangled function name. The LLVM API returns an llvm::GlobalVariable
-/// containing the function name, with the specific variable name and linkage
-/// required by LLVM InstrProf source-based coverage instrumentation. Use
-/// `bx.get_pgo_func_name_var()` to ensure the variable is only created once per
-/// `Instance`.
-fn create_pgo_func_name_var<'ll, 'tcx>(
-    cx: &CodegenCx<'ll, 'tcx>,
-    instance: Instance<'tcx>,
-) -> &'ll llvm::Value {
-    let mangled_fn_name: &str = cx.tcx.symbol_name(instance).name;
-    let llfn = cx.get_fn(instance);
-    unsafe {
-        llvm::LLVMRustCoverageCreatePGOFuncNameVar(
-            llfn,
-            mangled_fn_name.as_c_char_ptr(),
-            mangled_fn_name.len(),
-        )
-    }
-}
-
-pub(crate) fn write_filenames_section_to_buffer<'a>(
-    filenames: impl IntoIterator<Item = &'a str>,
-    buffer: &RustString,
-) {
-    let (pointers, lengths) = filenames
-        .into_iter()
-        .map(|s: &str| (s.as_c_char_ptr(), s.len()))
-        .unzip::<_, _, Vec<_>, Vec<_>>();
-
-    unsafe {
-        llvm::LLVMRustCoverageWriteFilenamesSectionToBuffer(
-            pointers.as_ptr(),
-            pointers.len(),
-            lengths.as_ptr(),
-            lengths.len(),
-            buffer,
-        );
-    }
-}
-
-pub(crate) fn write_mapping_to_buffer(
-    virtual_file_mapping: Vec<u32>,
-    expressions: Vec<ffi::CounterExpression>,
-    code_regions: &[ffi::CodeRegion],
-    branch_regions: &[ffi::BranchRegion],
-    mcdc_branch_regions: &[ffi::MCDCBranchRegion],
-    mcdc_decision_regions: &[ffi::MCDCDecisionRegion],
-    buffer: &RustString,
-) {
-    unsafe {
-        llvm::LLVMRustCoverageWriteMappingToBuffer(
-            virtual_file_mapping.as_ptr(),
-            virtual_file_mapping.len() as c_uint,
-            expressions.as_ptr(),
-            expressions.len() as c_uint,
-            code_regions.as_ptr(),
-            code_regions.len() as c_uint,
-            branch_regions.as_ptr(),
-            branch_regions.len() as c_uint,
-            mcdc_branch_regions.as_ptr(),
-            mcdc_branch_regions.len() as c_uint,
-            mcdc_decision_regions.as_ptr(),
-            mcdc_decision_regions.len() as c_uint,
-            buffer,
-        );
-    }
-}
-
-pub(crate) fn hash_bytes(bytes: &[u8]) -> u64 {
-    unsafe { llvm::LLVMRustCoverageHashByteArray(bytes.as_c_char_ptr(), bytes.len()) }
-}
-
-pub(crate) fn mapping_version() -> u32 {
-    unsafe { llvm::LLVMRustCoverageMappingVersion() }
-}

compiler/rustc_codegen_llvm/src/lib.rs

@@ -22,7 +22,6 @@
 
 use std::any::Any;
 use std::ffi::CStr;
-use std::io::Write;
 use std::mem::ManuallyDrop;
 
 use back::owned_target_machine::OwnedTargetMachine;
@@ -165,30 +164,12 @@ impl WriteBackendMethods for LlvmCodegenBackend {
     type ThinData = back::lto::ThinData;
     type ThinBuffer = back::lto::ThinBuffer;
     fn print_pass_timings(&self) {
-        unsafe {
+        let timings = llvm::build_string(|s| unsafe { llvm::LLVMRustPrintPassTimings(s) }).unwrap();
-            let mut size = 0;
+        print!("{timings}");
-            let cstr = llvm::LLVMRustPrintPassTimings(&raw mut size);
-            if cstr.is_null() {
-                println!("failed to get pass timings");
-            } else {
-                let timings = std::slice::from_raw_parts(cstr as *const u8, size);
-                std::io::stdout().write_all(timings).unwrap();
-                libc::free(cstr as *mut _);
-            }
-        }
     }
     fn print_statistics(&self) {
-        unsafe {
+        let stats = llvm::build_string(|s| unsafe { llvm::LLVMRustPrintStatistics(s) }).unwrap();
-            let mut size = 0;
+        print!("{stats}");
-            let cstr = llvm::LLVMRustPrintStatistics(&raw mut size);
-            if cstr.is_null() {
-                println!("failed to get pass stats");
-            } else {
-                let stats = std::slice::from_raw_parts(cstr as *const u8, size);
-                std::io::stdout().write_all(stats).unwrap();
-                libc::free(cstr as *mut _);
-            }
-        }
     }
     fn run_link(
         cgcx: &CodegenContext<Self>,

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1765,11 +1765,13 @@ pub fn LLVMRustBuildAtomicStore<'a>(
     /// Returns a string describing the last error caused by an LLVMRust* call.
     pub fn LLVMRustGetLastError() -> *const c_char;
 
-    /// Print the pass timings since static dtors aren't picking them up.
+    /// Prints the timing information collected by `-Ztime-llvm-passes`.
-    pub fn LLVMRustPrintPassTimings(size: *const size_t) -> *const c_char;
+    #[expect(improper_ctypes)]
+    pub(crate) fn LLVMRustPrintPassTimings(OutStr: &RustString);
 
-    /// Print the statistics since static dtors aren't picking them up.
+    /// Prints the statistics collected by `-Zprint-codegen-stats`.
-    pub fn LLVMRustPrintStatistics(size: *const size_t) -> *const c_char;
+    #[expect(improper_ctypes)]
+    pub(crate) fn LLVMRustPrintStatistics(OutStr: &RustString);
 
     /// Prepares inline assembly.
     pub fn LLVMRustInlineAsm(
@@ -1790,7 +1792,7 @@ pub fn LLVMRustInlineAsmVerify(
     ) -> bool;
 
     #[allow(improper_ctypes)]
-    pub(crate) fn LLVMRustCoverageWriteFilenamesSectionToBuffer(
+    pub(crate) fn LLVMRustCoverageWriteFilenamesToBuffer(
         Filenames: *const *const c_char,
         FilenamesLen: size_t,
         Lengths: *const size_t,
@@ -1799,19 +1801,19 @@ pub(crate) fn LLVMRustCoverageWriteFilenamesSectionToBuffer(
     );
 
     #[allow(improper_ctypes)]
-    pub(crate) fn LLVMRustCoverageWriteMappingToBuffer(
+    pub(crate) fn LLVMRustCoverageWriteFunctionMappingsToBuffer(
         VirtualFileMappingIDs: *const c_uint,
-        NumVirtualFileMappingIDs: c_uint,
+        NumVirtualFileMappingIDs: size_t,
         Expressions: *const crate::coverageinfo::ffi::CounterExpression,
-        NumExpressions: c_uint,
+        NumExpressions: size_t,
         CodeRegions: *const crate::coverageinfo::ffi::CodeRegion,
-        NumCodeRegions: c_uint,
+        NumCodeRegions: size_t,
         BranchRegions: *const crate::coverageinfo::ffi::BranchRegion,
-        NumBranchRegions: c_uint,
+        NumBranchRegions: size_t,
         MCDCBranchRegions: *const crate::coverageinfo::ffi::MCDCBranchRegion,
-        NumMCDCBranchRegions: c_uint,
+        NumMCDCBranchRegions: size_t,
         MCDCDecisionRegions: *const crate::coverageinfo::ffi::MCDCDecisionRegion,
-        NumMCDCDecisionRegions: c_uint,
+        NumMCDCDecisionRegions: size_t,
         BufferOut: &RustString,
     );
 
@@ -1820,16 +1822,16 @@ pub(crate) fn LLVMRustCoverageCreatePGOFuncNameVar(
         FuncName: *const c_char,
         FuncNameLen: size_t,
     ) -> &Value;
-    pub(crate) fn LLVMRustCoverageHashByteArray(Bytes: *const c_char, NumBytes: size_t) -> u64;
+    pub(crate) fn LLVMRustCoverageHashBytes(Bytes: *const c_char, NumBytes: size_t) -> u64;
 
     #[allow(improper_ctypes)]
-    pub(crate) fn LLVMRustCoverageWriteMapSectionNameToString(M: &Module, Str: &RustString);
+    pub(crate) fn LLVMRustCoverageWriteCovmapSectionNameToString(M: &Module, OutStr: &RustString);
 
     #[allow(improper_ctypes)]
-    pub(crate) fn LLVMRustCoverageWriteFuncSectionNameToString(M: &Module, Str: &RustString);
+    pub(crate) fn LLVMRustCoverageWriteCovfunSectionNameToString(M: &Module, OutStr: &RustString);
 
     #[allow(improper_ctypes)]
-    pub(crate) fn LLVMRustCoverageWriteMappingVarNameToString(Str: &RustString);
+    pub(crate) fn LLVMRustCoverageWriteCovmapVarNameToString(OutStr: &RustString);
 
     pub(crate) fn LLVMRustCoverageMappingVersion() -> u32;
     pub fn LLVMRustDebugMetadataVersion() -> u32;

compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp

@@ -123,13 +123,13 @@ fromRust(LLVMRustCounterExprKind Kind) {
   report_fatal_error("Bad LLVMRustCounterExprKind!");
 }
 
-extern "C" void LLVMRustCoverageWriteFilenamesSectionToBuffer(
+extern "C" void LLVMRustCoverageWriteFilenamesToBuffer(
     const char *const Filenames[], size_t FilenamesLen, // String start pointers
     const size_t *const Lengths, size_t LengthsLen,     // Corresponding lengths
     RustStringRef BufferOut) {
   if (FilenamesLen != LengthsLen) {
     report_fatal_error(
-        "Mismatched lengths in LLVMRustCoverageWriteFilenamesSectionToBuffer");
+        "Mismatched lengths in LLVMRustCoverageWriteFilenamesToBuffer");
   }
 
   SmallVector<std::string, 32> FilenameRefs;
@@ -143,16 +143,15 @@ extern "C" void LLVMRustCoverageWriteFilenamesSectionToBuffer(
   FilenamesWriter.write(OS);
 }
 
-extern "C" void LLVMRustCoverageWriteMappingToBuffer(
+extern "C" void LLVMRustCoverageWriteFunctionMappingsToBuffer(
-    const unsigned *VirtualFileMappingIDs, unsigned NumVirtualFileMappingIDs,
+    const unsigned *VirtualFileMappingIDs, size_t NumVirtualFileMappingIDs,
-    const LLVMRustCounterExpression *RustExpressions, unsigned NumExpressions,
+    const LLVMRustCounterExpression *RustExpressions, size_t NumExpressions,
-    const LLVMRustCoverageCodeRegion *CodeRegions, unsigned NumCodeRegions,
+    const LLVMRustCoverageCodeRegion *CodeRegions, size_t NumCodeRegions,
-    const LLVMRustCoverageBranchRegion *BranchRegions,
+    const LLVMRustCoverageBranchRegion *BranchRegions, size_t NumBranchRegions,
-    unsigned NumBranchRegions,
     const LLVMRustCoverageMCDCBranchRegion *MCDCBranchRegions,
-    unsigned NumMCDCBranchRegions,
+    size_t NumMCDCBranchRegions,
     const LLVMRustCoverageMCDCDecisionRegion *MCDCDecisionRegions,
-    unsigned NumMCDCDecisionRegions, RustStringRef BufferOut) {
+    size_t NumMCDCDecisionRegions, RustStringRef BufferOut) {
   // Convert from FFI representation to LLVM representation.
 
   // Expressions:
@@ -219,34 +218,37 @@ LLVMRustCoverageCreatePGOFuncNameVar(LLVMValueRef F, const char *FuncName,
   return wrap(createPGOFuncNameVar(*cast<Function>(unwrap(F)), FuncNameRef));
 }
 
-extern "C" uint64_t LLVMRustCoverageHashByteArray(const char *Bytes,
+extern "C" uint64_t LLVMRustCoverageHashBytes(const char *Bytes,
-                                                  size_t NumBytes) {
+                                              size_t NumBytes) {
-  auto StrRef = StringRef(Bytes, NumBytes);
+  return IndexedInstrProf::ComputeHash(StringRef(Bytes, NumBytes));
-  return IndexedInstrProf::ComputeHash(StrRef);
 }
 
-static void WriteSectionNameToString(LLVMModuleRef M, InstrProfSectKind SK,
+// Private helper function for getting the covmap and covfun section names.
-                                     RustStringRef Str) {
+static void writeInstrProfSectionNameToString(LLVMModuleRef M,
+                                              InstrProfSectKind SectKind,
+                                              RustStringRef OutStr) {
   auto TargetTriple = Triple(unwrap(M)->getTargetTriple());
-  auto name = getInstrProfSectionName(SK, TargetTriple.getObjectFormat());
+  auto name = getInstrProfSectionName(SectKind, TargetTriple.getObjectFormat());
-  auto OS = RawRustStringOstream(Str);
+  auto OS = RawRustStringOstream(OutStr);
   OS << name;
 }
 
-extern "C" void LLVMRustCoverageWriteMapSectionNameToString(LLVMModuleRef M,
+extern "C" void
-                                                            RustStringRef Str) {
+LLVMRustCoverageWriteCovmapSectionNameToString(LLVMModuleRef M,
-  WriteSectionNameToString(M, IPSK_covmap, Str);
+                                               RustStringRef OutStr) {
+  writeInstrProfSectionNameToString(M, IPSK_covmap, OutStr);
 }
 
 extern "C" void
-LLVMRustCoverageWriteFuncSectionNameToString(LLVMModuleRef M,
+LLVMRustCoverageWriteCovfunSectionNameToString(LLVMModuleRef M,
-                                             RustStringRef Str) {
+                                               RustStringRef OutStr) {
-  WriteSectionNameToString(M, IPSK_covfun, Str);
+  writeInstrProfSectionNameToString(M, IPSK_covfun, OutStr);
 }
 
-extern "C" void LLVMRustCoverageWriteMappingVarNameToString(RustStringRef Str) {
+extern "C" void
+LLVMRustCoverageWriteCovmapVarNameToString(RustStringRef OutStr) {
   auto name = getCoverageMappingVarName();
-  auto OS = RawRustStringOstream(Str);
+  auto OS = RawRustStringOstream(OutStr);
   OS << name;
 }
 

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -140,26 +140,14 @@ extern "C" void LLVMRustSetNormalizedTarget(LLVMModuleRef M,
   unwrap(M)->setTargetTriple(Triple::normalize(Triple));
 }
 
-extern "C" const char *LLVMRustPrintPassTimings(size_t *Len) {
+extern "C" void LLVMRustPrintPassTimings(RustStringRef OutBuf) {
-  std::string buf;
+  auto OS = RawRustStringOstream(OutBuf);
-  auto SS = raw_string_ostream(buf);
+  TimerGroup::printAll(OS);
-  TimerGroup::printAll(SS);
-  SS.flush();
-  *Len = buf.length();
-  char *CStr = (char *)malloc(*Len);
-  memcpy(CStr, buf.c_str(), *Len);
-  return CStr;
 }
 
-extern "C" const char *LLVMRustPrintStatistics(size_t *Len) {
+extern "C" void LLVMRustPrintStatistics(RustStringRef OutBuf) {
-  std::string buf;
+  auto OS = RawRustStringOstream(OutBuf);
-  auto SS = raw_string_ostream(buf);
+  llvm::PrintStatistics(OS);
-  llvm::PrintStatistics(SS);
-  SS.flush();
-  *Len = buf.length();
-  char *CStr = (char *)malloc(*Len);
-  memcpy(CStr, buf.c_str(), *Len);
-  return CStr;
 }
 
 extern "C" LLVMValueRef LLVMRustGetNamedValue(LLVMModuleRef M, const char *Name,

compiler/rustc_mir_transform/src/coverage/graph.rs

@@ -1,7 +1,7 @@
 use std::cmp::Ordering;
 use std::collections::VecDeque;
-use std::iter;
 use std::ops::{Index, IndexMut};
+use std::{iter, mem, slice};
 
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxHashSet;
@@ -127,10 +127,10 @@ fn compute_basic_coverage_blocks(
         let mut bcbs = IndexVec::<BasicCoverageBlock, _>::with_capacity(num_basic_blocks);
         let mut bb_to_bcb = IndexVec::from_elem_n(None, num_basic_blocks);
 
-        let mut add_basic_coverage_block = |basic_blocks: &mut Vec<BasicBlock>| {
+        let mut flush_chain_into_new_bcb = |current_chain: &mut Vec<BasicBlock>| {
             // Take the accumulated list of blocks, leaving the vector empty
             // to be used by subsequent BCBs.
-            let basic_blocks = std::mem::take(basic_blocks);
+            let basic_blocks = mem::take(current_chain);
 
             let bcb = bcbs.next_index();
             for &bb in basic_blocks.iter() {
@@ -141,48 +141,41 @@ fn compute_basic_coverage_blocks(
                 bcb_filtered_successors(mir_body[bb].terminator()).is_out_summable()
             });
             let bcb_data = BasicCoverageBlockData { basic_blocks, is_out_summable };
-            debug!("adding bcb{}: {:?}", bcb.index(), bcb_data);
+            debug!("adding {bcb:?}: {bcb_data:?}");
             bcbs.push(bcb_data);
         };
 
-        // Walk the MIR CFG using a Preorder traversal, which starts from `START_BLOCK` and follows
+        // Traverse the MIR control-flow graph, accumulating chains of blocks
-        // each block terminator's `successors()`. Coverage spans must map to actual source code,
+        // that can be combined into a single node in the coverage graph.
-        // so compiler generated blocks and paths can be ignored. To that end, the CFG traversal
+        // A depth-first search ensures that if two nodes can be chained
-        // intentionally omits unwind paths.
+        // together, they will be adjacent in the traversal order.
-        // FIXME(#78544): MIR InstrumentCoverage: Improve coverage of `#[should_panic]` tests and
-        // `catch_unwind()` handlers.
 
         // Accumulates a chain of blocks that will be combined into one BCB.
-        let mut basic_blocks = Vec::new();
+        let mut current_chain = vec![];
 
-        let filtered_successors = |bb| bcb_filtered_successors(mir_body[bb].terminator());
+        let subgraph = CoverageRelevantSubgraph::new(&mir_body.basic_blocks);
-        for bb in short_circuit_preorder(mir_body, filtered_successors)
+        for bb in graph::depth_first_search(subgraph, mir::START_BLOCK)
             .filter(|&bb| mir_body[bb].terminator().kind != TerminatorKind::Unreachable)
         {
-            // If the previous block can't be chained into `bb`, flush the accumulated
+            if let Some(&prev) = current_chain.last() {
-            // blocks into a new BCB, then start building the next chain.
+                // Adding a block to a non-empty chain is allowed if the
-            if let Some(&prev) = basic_blocks.last()
+                // previous block permits chaining, and the current block has
-                && (!filtered_successors(prev).is_chainable() || {
+                // `prev` as its sole predecessor.
-                    // If `bb` has multiple predecessor blocks, or `prev` isn't
+                let can_chain = subgraph.coverage_successors(prev).is_out_chainable()
-                    // one of its predecessors, we can't chain and must flush.
+                    && mir_body.basic_blocks.predecessors()[bb].as_slice() == &[prev];
-                    let predecessors = &mir_body.basic_blocks.predecessors()[bb];
+                if !can_chain {
-                    predecessors.len() > 1 || !predecessors.contains(&prev)
+                    // The current block can't be added to the existing chain, so
-                })
+                    // flush that chain into a new BCB, and start a new chain.
-            {
+                    flush_chain_into_new_bcb(&mut current_chain);
-                debug!(
+                }
-                    terminator_kind = ?mir_body[prev].terminator().kind,
-                    predecessors = ?&mir_body.basic_blocks.predecessors()[bb],
-                    "can't chain from {prev:?} to {bb:?}"
-                );
-                add_basic_coverage_block(&mut basic_blocks);
             }
 
-            basic_blocks.push(bb);
+            current_chain.push(bb);
         }
 
-        if !basic_blocks.is_empty() {
+        if !current_chain.is_empty() {
             debug!("flushing accumulated blocks into one last BCB");
-            add_basic_coverage_block(&mut basic_blocks);
+            flush_chain_into_new_bcb(&mut current_chain);
         }
 
         (bcbs, bb_to_bcb)
@@ -389,34 +382,28 @@ pub(crate) fn last_bb(&self) -> BasicBlock {
 /// indicates whether that block can potentially be combined into the same BCB
 /// as its sole successor.
 #[derive(Clone, Copy, Debug)]
-enum CoverageSuccessors<'a> {
+struct CoverageSuccessors<'a> {
-    /// The terminator has exactly one straight-line successor, so its block can
+    /// Coverage-relevant successors of the corresponding terminator.
-    /// potentially be combined into the same BCB as that successor.
+    /// There might be 0, 1, or multiple targets.
-    Chainable(BasicBlock),
+    targets: &'a [BasicBlock],
-    /// The block cannot be combined into the same BCB as its successor(s).
+    /// `Yield` terminators are not chainable, because their sole out-edge is
-    NotChainable(&'a [BasicBlock]),
+    /// only followed if/when the generator is resumed after the yield.
-    /// Yield terminators are not chainable, and their execution count can also
+    is_yield: bool,
-    /// differ from the execution count of their out-edge.
-    Yield(BasicBlock),
 }
 
 impl CoverageSuccessors<'_> {
-    fn is_chainable(&self) -> bool {
+    /// If `false`, this terminator cannot be chained into another block when
-        match self {
+    /// building the coverage graph.
-            Self::Chainable(_) => true,
+    fn is_out_chainable(&self) -> bool {
-            Self::NotChainable(_) => false,
+        // If a terminator is out-summable and has exactly one out-edge, then
-            Self::Yield(_) => false,
+        // it is eligible to be chained into its successor block.
-        }
+        self.is_out_summable() && self.targets.len() == 1
     }
 
     /// Returns true if the terminator itself is assumed to have the same
     /// execution count as the sum of its out-edges (assuming no panics).
     fn is_out_summable(&self) -> bool {
-        match self {
+        !self.is_yield && !self.targets.is_empty()
-            Self::Chainable(_) => true,
-            Self::NotChainable(_) => true,
-            Self::Yield(_) => false,
-        }
     }
 }
 
@@ -425,12 +412,7 @@ impl IntoIterator for CoverageSuccessors<'_> {
     type IntoIter = impl DoubleEndedIterator<Item = Self::Item>;
 
     fn into_iter(self) -> Self::IntoIter {
-        match self {
+        self.targets.iter().copied()
-            Self::Chainable(bb) | Self::Yield(bb) => {
-                Some(bb).into_iter().chain((&[]).iter().copied())
-            }
-            Self::NotChainable(bbs) => None.into_iter().chain(bbs.iter().copied()),
-        }
     }
 }
 
@@ -440,14 +422,17 @@ fn into_iter(self) -> Self::IntoIter {
 // `catch_unwind()` handlers.
 fn bcb_filtered_successors<'a, 'tcx>(terminator: &'a Terminator<'tcx>) -> CoverageSuccessors<'a> {
     use TerminatorKind::*;
-    match terminator.kind {
+    let mut is_yield = false;
+    let targets = match &terminator.kind {
         // A switch terminator can have many coverage-relevant successors.
-        // (If there is exactly one successor, we still treat it as not chainable.)
+        SwitchInt { targets, .. } => targets.all_targets(),
-        SwitchInt { ref targets, .. } => CoverageSuccessors::NotChainable(targets.all_targets()),
 
         // A yield terminator has exactly 1 successor, but should not be chained,
         // because its resume edge has a different execution count.
-        Yield { resume, .. } => CoverageSuccessors::Yield(resume),
+        Yield { resume, .. } => {
+            is_yield = true;
+            slice::from_ref(resume)
+        }
 
         // These terminators have exactly one coverage-relevant successor,
         // and can be chained into it.
@@ -455,24 +440,15 @@ fn bcb_filtered_successors<'a, 'tcx>(terminator: &'a Terminator<'tcx>) -> Covera
         | Drop { target, .. }
         | FalseEdge { real_target: target, .. }
         | FalseUnwind { real_target: target, .. }
-        | Goto { target } => CoverageSuccessors::Chainable(target),
+        | Goto { target } => slice::from_ref(target),
 
         // A call terminator can normally be chained, except when it has no
         // successor because it is known to diverge.
-        Call { target: maybe_target, .. } => match maybe_target {
+        Call { target: maybe_target, .. } => maybe_target.as_slice(),
-            Some(target) => CoverageSuccessors::Chainable(target),
-            None => CoverageSuccessors::NotChainable(&[]),
-        },
 
         // An inline asm terminator can normally be chained, except when it
         // diverges or uses asm goto.
-        InlineAsm { ref targets, .. } => {
+        InlineAsm { targets, .. } => &targets,
-            if let [target] = targets[..] {
-                CoverageSuccessors::Chainable(target)
-            } else {
-                CoverageSuccessors::NotChainable(targets)
-            }
-        }
 
         // These terminators have no coverage-relevant successors.
         CoroutineDrop
@@ -480,8 +456,10 @@ fn bcb_filtered_successors<'a, 'tcx>(terminator: &'a Terminator<'tcx>) -> Covera
         | TailCall { .. }
         | Unreachable
         | UnwindResume
-        | UnwindTerminate(_) => CoverageSuccessors::NotChainable(&[]),
+        | UnwindTerminate(_) => &[],
-    }
+    };
+
+    CoverageSuccessors { targets, is_yield }
 }
 
 /// Maintains separate worklists for each loop in the BasicCoverageBlock CFG, plus one for the
@@ -616,28 +594,31 @@ pub(crate) fn unvisited(&self) -> Vec<BasicCoverageBlock> {
     }
 }
 
-fn short_circuit_preorder<'a, 'tcx, F, Iter>(
+/// Wrapper around a [`mir::BasicBlocks`] graph that restricts each node's
-    body: &'a mir::Body<'tcx>,
+/// successors to only the ones considered "relevant" when building a coverage
-    filtered_successors: F,
+/// graph.
-) -> impl Iterator<Item = BasicBlock> + Captures<'a> + Captures<'tcx>
+#[derive(Clone, Copy)]
-where
+struct CoverageRelevantSubgraph<'a, 'tcx> {
-    F: Fn(BasicBlock) -> Iter,
+    basic_blocks: &'a mir::BasicBlocks<'tcx>,
-    Iter: IntoIterator<Item = BasicBlock>,
+}
-{
+impl<'a, 'tcx> CoverageRelevantSubgraph<'a, 'tcx> {
-    let mut visited = BitSet::new_empty(body.basic_blocks.len());
+    fn new(basic_blocks: &'a mir::BasicBlocks<'tcx>) -> Self {
-    let mut worklist = vec![mir::START_BLOCK];
+        Self { basic_blocks }
-
+    }
-    std::iter::from_fn(move || {
+
-        while let Some(bb) = worklist.pop() {
+    fn coverage_successors(&self, bb: BasicBlock) -> CoverageSuccessors<'_> {
-            if !visited.insert(bb) {
+        bcb_filtered_successors(self.basic_blocks[bb].terminator())
-                continue;
+    }
-            }
+}
-
+impl<'a, 'tcx> graph::DirectedGraph for CoverageRelevantSubgraph<'a, 'tcx> {
-            worklist.extend(filtered_successors(bb));
+    type Node = BasicBlock;
-
+
-            return Some(bb);
+    fn num_nodes(&self) -> usize {
-        }
+        self.basic_blocks.num_nodes()
-
+    }
-        None
+}
-    })
+impl<'a, 'tcx> graph::Successors for CoverageRelevantSubgraph<'a, 'tcx> {
+    fn successors(&self, bb: Self::Node) -> impl Iterator<Item = Self::Node> {
+        self.coverage_successors(bb).into_iter()
+    }
 }

compiler/stable_mir/src/mir/pretty.rs

@@ -1,13 +1,14 @@
+//! Implement methods to pretty print stable MIR body.
 use std::fmt::Debug;
 use std::io::Write;
 use std::{fmt, io, iter};
 
 use fmt::{Display, Formatter};
 
-use super::{AssertMessage, BinOp, BorrowKind, FakeBorrowKind, TerminatorKind};
+use super::{AggregateKind, AssertMessage, BinOp, BorrowKind, FakeBorrowKind, TerminatorKind};
 use crate::mir::{Operand, Place, Rvalue, StatementKind, UnwindAction, VarDebugInfoContents};
-use crate::ty::{IndexedVal, MirConst, Ty, TyConst};
+use crate::ty::{AdtKind, IndexedVal, MirConst, Ty, TyConst};
-use crate::{Body, Mutability, with};
+use crate::{Body, CrateDef, Mutability, with};
 
 impl Display for Ty {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
@@ -23,10 +24,11 @@ fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
 
 pub(crate) fn function_body<W: Write>(writer: &mut W, body: &Body, name: &str) -> io::Result<()> {
     write!(writer, "fn {name}(")?;
-    body.arg_locals()
+    let mut sep = "";
-        .iter()
+    for (index, local) in body.arg_locals().iter().enumerate() {
-        .enumerate()
+        write!(writer, "{}_{}: {}", sep, index + 1, local.ty)?;
-        .try_for_each(|(index, local)| write!(writer, "_{}: {}", index + 1, local.ty))?;
+        sep = ", ";
+    }
     write!(writer, ")")?;
 
     let return_local = body.ret_local();
@@ -73,39 +75,40 @@ pub(crate) fn function_body<W: Write>(writer: &mut W, body: &Body, name: &str) -
 }
 
 fn pretty_statement<W: Write>(writer: &mut W, statement: &StatementKind) -> io::Result<()> {
+    const INDENT: &str = "        ";
     match statement {
         StatementKind::Assign(place, rval) => {
-            write!(writer, "        {place:?} = ")?;
+            write!(writer, "{INDENT}{place:?} = ")?;
             pretty_rvalue(writer, rval)?;
             writeln!(writer, ";")
         }
         // FIXME: Add rest of the statements
         StatementKind::FakeRead(cause, place) => {
-            writeln!(writer, "FakeRead({cause:?}, {place:?});")
+            writeln!(writer, "{INDENT}FakeRead({cause:?}, {place:?});")
         }
         StatementKind::SetDiscriminant { place, variant_index } => {
-            writeln!(writer, "discriminant({place:?} = {};", variant_index.to_index())
+            writeln!(writer, "{INDENT}discriminant({place:?} = {};", variant_index.to_index())
         }
         StatementKind::Deinit(place) => writeln!(writer, "Deinit({place:?};"),
         StatementKind::StorageLive(local) => {
-            writeln!(writer, "StorageLive(_{local});")
+            writeln!(writer, "{INDENT}StorageLive(_{local});")
         }
         StatementKind::StorageDead(local) => {
-            writeln!(writer, "StorageDead(_{local});")
+            writeln!(writer, "{INDENT}StorageDead(_{local});")
         }
         StatementKind::Retag(kind, place) => writeln!(writer, "Retag({kind:?}, {place:?});"),
         StatementKind::PlaceMention(place) => {
-            writeln!(writer, "PlaceMention({place:?};")
+            writeln!(writer, "{INDENT}PlaceMention({place:?};")
         }
         StatementKind::ConstEvalCounter => {
-            writeln!(writer, "ConstEvalCounter;")
+            writeln!(writer, "{INDENT}ConstEvalCounter;")
         }
-        StatementKind::Nop => writeln!(writer, "nop;"),
+        StatementKind::Nop => writeln!(writer, "{INDENT}nop;"),
         StatementKind::AscribeUserType { .. }
         | StatementKind::Coverage(_)
         | StatementKind::Intrinsic(_) => {
             // FIX-ME: Make them pretty.
-            writeln!(writer, "{statement:?};")
+            writeln!(writer, "{INDENT}{statement:?};")
         }
     }
 }
@@ -322,15 +325,11 @@ fn pretty_ty_const(ct: &TyConst) -> String {
 fn pretty_rvalue<W: Write>(writer: &mut W, rval: &Rvalue) -> io::Result<()> {
     match rval {
         Rvalue::AddressOf(mutability, place) => {
-            write!(writer, "&raw {}(*{:?})", pretty_mut(*mutability), place)
+            write!(writer, "&raw {} {:?}", pretty_mut(*mutability), place)
         }
         Rvalue::Aggregate(aggregate_kind, operands) => {
             // FIXME: Add pretty_aggregate function that returns a pretty string
-            write!(writer, "{aggregate_kind:?} (")?;
+            pretty_aggregate(writer, aggregate_kind, operands)
-            let mut op_iter = operands.iter();
-            op_iter.next().map_or(Ok(()), |op| write!(writer, "{}", pretty_operand(op)))?;
-            op_iter.try_for_each(|op| write!(writer, ", {}", pretty_operand(op)))?;
-            write!(writer, ")")
         }
         Rvalue::BinaryOp(bin, op1, op2) => {
             write!(writer, "{:?}({}, {})", bin, pretty_operand(op1), pretty_operand(op2))
@@ -360,22 +359,74 @@ fn pretty_rvalue<W: Write>(writer: &mut W, rval: &Rvalue) -> io::Result<()> {
             write!(writer, "{kind}{place:?}")
         }
         Rvalue::Repeat(op, cnst) => {
-            write!(writer, "{} \" \" {}", pretty_operand(op), pretty_ty_const(cnst))
+            write!(writer, "[{}; {}]", pretty_operand(op), pretty_ty_const(cnst))
         }
         Rvalue::ShallowInitBox(_, _) => Ok(()),
         Rvalue::ThreadLocalRef(item) => {
             write!(writer, "thread_local_ref{item:?}")
         }
         Rvalue::NullaryOp(nul, ty) => {
-            write!(writer, "{nul:?} {ty} \" \"")
+            write!(writer, "{nul:?}::<{ty}>() \" \"")
         }
         Rvalue::UnaryOp(un, op) => {
-            write!(writer, "{} \" \" {:?}", pretty_operand(op), un)
+            write!(writer, "{:?}({})", un, pretty_operand(op))
         }
         Rvalue::Use(op) => write!(writer, "{}", pretty_operand(op)),
     }
 }
 
+fn pretty_aggregate<W: Write>(
+    writer: &mut W,
+    aggregate_kind: &AggregateKind,
+    operands: &Vec<Operand>,
+) -> io::Result<()> {
+    let suffix = match aggregate_kind {
+        AggregateKind::Array(_) => {
+            write!(writer, "[")?;
+            "]"
+        }
+        AggregateKind::Tuple => {
+            write!(writer, "(")?;
+            ")"
+        }
+        AggregateKind::Adt(def, var, _, _, _) => {
+            if def.kind() == AdtKind::Enum {
+                write!(writer, "{}::{}", def.name(), def.variant(*var).unwrap().name())?;
+            } else {
+                write!(writer, "{}", def.variant(*var).unwrap().name())?;
+            }
+            if operands.is_empty() {
+                return Ok(());
+            }
+            // FIXME: Change this once we have CtorKind in StableMIR.
+            write!(writer, "(")?;
+            ")"
+        }
+        AggregateKind::Closure(def, _) => {
+            write!(writer, "{{closure@{}}}(", def.span().diagnostic())?;
+            ")"
+        }
+        AggregateKind::Coroutine(def, _, _) => {
+            write!(writer, "{{coroutine@{}}}(", def.span().diagnostic())?;
+            ")"
+        }
+        AggregateKind::RawPtr(ty, mutability) => {
+            write!(
+                writer,
+                "*{} {ty} from (",
+                if *mutability == Mutability::Mut { "mut" } else { "const" }
+            )?;
+            ")"
+        }
+    };
+    let mut separator = "";
+    for op in operands {
+        write!(writer, "{}{}", separator, pretty_operand(op))?;
+        separator = ", ";
+    }
+    write!(writer, "{suffix}")
+}
+
 fn pretty_mut(mutability: Mutability) -> &'static str {
     match mutability {
         Mutability::Not => " ",

compiler/stable_mir/src/ty.rs

@@ -271,6 +271,14 @@ pub fn get_filename(&self) -> Filename {
     pub fn get_lines(&self) -> LineInfo {
         with(|c| c.get_lines(self))
     }
+
+    /// Return the span location to be printed in diagnostic messages.
+    ///
+    /// This may leak local file paths and should not be used to build artifacts that may be
+    /// distributed.
+    pub fn diagnostic(&self) -> String {
+        with(|c| c.span_to_string(*self))
+    }
 }
 
 #[derive(Clone, Copy, Debug, Serialize)]

library/std/src/sync/mpmc/list.rs

@@ -63,14 +63,14 @@ struct Block<T> {
 
 impl<T> Block<T> {
     /// Creates an empty block.
-    fn new() -> Block<T> {
+    fn new() -> Box<Block<T>> {
         // SAFETY: This is safe because:
         //  [1] `Block::next` (AtomicPtr) may be safely zero initialized.
         //  [2] `Block::slots` (Array) may be safely zero initialized because of [3, 4].
         //  [3] `Slot::msg` (UnsafeCell) may be safely zero initialized because it
         //       holds a MaybeUninit.
         //  [4] `Slot::state` (AtomicUsize) may be safely zero initialized.
-        unsafe { MaybeUninit::zeroed().assume_init() }
+        unsafe { Box::new_zeroed().assume_init() }
     }
 
     /// Waits until the next pointer is set.
@@ -199,13 +199,13 @@ fn start_send(&self, token: &mut Token) -> bool {
             // If we're going to have to install the next block, allocate it in advance in order to
             // make the wait for other threads as short as possible.
             if offset + 1 == BLOCK_CAP && next_block.is_none() {
-                next_block = Some(Box::new(Block::<T>::new()));
+                next_block = Some(Block::<T>::new());
             }
 
             // If this is the first message to be sent into the channel, we need to allocate the
             // first block and install it.
             if block.is_null() {
-                let new = Box::into_raw(Box::new(Block::<T>::new()));
+                let new = Box::into_raw(Block::<T>::new());
 
                 if self
                     .tail

tests/ui/stable-mir-print/operands.rs

@@ -0,0 +1,48 @@
+//@ compile-flags: -Z unpretty=stable-mir --crate-type lib -C panic=abort
+//@ check-pass
+//@ only-x86_64
+//@ needs-unwind unwind edges are different with panic=abort
+//! Check how stable mir pretty printer prints different operands and abort strategy.
+
+pub fn operands(val: u8) {
+    let array = [val; 10];
+    let first = array[0];
+    let last = array[10 - 1];
+    assert_eq!(first, last);
+
+    let reference = &first;
+    let dereferenced = *reference;
+    assert_eq!(dereferenced, first);
+
+    let tuple = (first, last);
+    let (first_again, _) = tuple;
+    let first_again_again = tuple.0;
+    assert_eq!(first_again, first_again_again);
+
+    let length = array.len();
+    let size_of = std::mem::size_of_val(&length);
+    assert_eq!(length, size_of);
+}
+
+pub struct Dummy {
+    c: char,
+    i: i32,
+}
+
+pub enum Ctors {
+    Unit,
+    StructLike { d: Dummy },
+    TupLike(bool),
+}
+
+pub fn more_operands() -> [Ctors; 3] {
+    let dummy = Dummy { c: 'a', i: i32::MIN };
+    let unit = Ctors::Unit;
+    let struct_like = Ctors::StructLike { d: dummy };
+    let tup_like = Ctors::TupLike(false);
+    [unit, struct_like, tup_like]
+}
+
+pub fn closures(x: bool, z: bool) -> impl FnOnce(bool) -> bool {
+    move |y: bool| (x ^ y) || z
+}

tests/ui/stable-mir-print/operands.stdout

@@ -0,0 +1,263 @@
+// WARNING: This is highly experimental output it's intended for stable-mir developers only.
+// If you find a bug or want to improve the output open a issue at https://github.com/rust-lang/project-stable-mir.
+fn operands(_1: u8) -> () {
+    let mut _0: ();
+    let  _2: [u8; 10];
+    let  _3: u8;
+    let  _4: usize;
+    let mut _5: usize;
+    let mut _6: bool;
+    let  _7: u8;
+    let  _8: usize;
+    let mut _9: (usize, bool);
+    let mut _10: usize;
+    let mut _11: bool;
+    let mut _12: (&u8, &u8);
+    let mut _13: &u8;
+    let mut _14: &u8;
+    let  _15: &u8;
+    let  _16: &u8;
+    let mut _17: bool;
+    let mut _18: u8;
+    let mut _19: u8;
+    let  _20: core::panicking::AssertKind;
+    let  _21: !;
+    let mut _22: Option<Arguments<'_>>;
+    let  _23: &u8;
+    let  _24: u8;
+    let mut _25: (&u8, &u8);
+    let mut _26: &u8;
+    let mut _27: &u8;
+    let  _28: &u8;
+    let  _29: &u8;
+    let mut _30: bool;
+    let mut _31: u8;
+    let mut _32: u8;
+    let  _33: core::panicking::AssertKind;
+    let  _34: !;
+    let mut _35: Option<Arguments<'_>>;
+    let  _36: (u8, u8);
+    let  _37: u8;
+    let  _38: u8;
+    let mut _39: (&u8, &u8);
+    let mut _40: &u8;
+    let mut _41: &u8;
+    let  _42: &u8;
+    let  _43: &u8;
+    let mut _44: bool;
+    let mut _45: u8;
+    let mut _46: u8;
+    let  _47: core::panicking::AssertKind;
+    let  _48: !;
+    let mut _49: Option<Arguments<'_>>;
+    let  _50: usize;
+    let mut _51: &[u8];
+    let mut _52: &[u8; 10];
+    let  _53: usize;
+    let  _54: &usize;
+    let mut _55: (&usize, &usize);
+    let mut _56: &usize;
+    let mut _57: &usize;
+    let  _58: &usize;
+    let  _59: &usize;
+    let mut _60: bool;
+    let mut _61: usize;
+    let mut _62: usize;
+    let  _63: core::panicking::AssertKind;
+    let  _64: !;
+    let mut _65: Option<Arguments<'_>>;
+    debug val => _1;
+    debug array => _2;
+    debug first => _3;
+    debug last => _7;
+    debug left_val => _15;
+    debug right_val => _16;
+    debug kind => _20;
+    debug reference => _23;
+    debug dereferenced => _24;
+    debug left_val => _28;
+    debug right_val => _29;
+    debug kind => _33;
+    debug tuple => _36;
+    debug first_again => _37;
+    debug first_again_again => _38;
+    debug left_val => _42;
+    debug right_val => _43;
+    debug kind => _47;
+    debug length => _50;
+    debug size_of => _53;
+    debug left_val => _58;
+    debug right_val => _59;
+    debug kind => _63;
+    bb0: {
+        _2 = [_1; 10];
+        _4 = 0_usize;
+        _5 = 10_usize;
+        _6 = Lt(_4, _5);
+        assert(move _6, "index out of bounds: the length is {} but the index is {}", move _5, _4) -> [success: bb1, unwind unreachable];
+    }
+    bb1: {
+        _3 = _2[_4];
+        _9 = CheckedSub(10_usize, 1_usize);
+        assert(!move (_9.1: bool), "attempt to compute `{} - {}`, which would overflow", 10_usize, 1_usize) -> [success: bb2, unwind unreachable];
+    }
+    bb2: {
+        _8 = move (_9.0: usize);
+        _10 = 10_usize;
+        _11 = Lt(_8, _10);
+        assert(move _11, "index out of bounds: the length is {} but the index is {}", move _10, _8) -> [success: bb3, unwind unreachable];
+    }
+    bb3: {
+        _7 = _2[_8];
+        _13 = &_3;
+        _14 = &_7;
+        _12 = (move _13, move _14);
+        _15 = (_12.0: &u8);
+        _16 = (_12.1: &u8);
+        _18 = (*_15);
+        _19 = (*_16);
+        _17 = Eq(move _18, move _19);
+        switchInt(move _17) -> [0: bb5, otherwise: bb4];
+    }
+    bb4: {
+        _23 = &_3;
+        _24 = (*_23);
+        _26 = &_24;
+        _27 = &_3;
+        _25 = (move _26, move _27);
+        _28 = (_25.0: &u8);
+        _29 = (_25.1: &u8);
+        _31 = (*_28);
+        _32 = (*_29);
+        _30 = Eq(move _31, move _32);
+        switchInt(move _30) -> [0: bb7, otherwise: bb6];
+    }
+    bb5: {
+        _20 = core::panicking::AssertKind::Eq;
+        _22 = std::option::Option::None;
+        _21 = core::panicking::assert_failed::<u8, u8>(move _20, _15, _16, move _22) -> unwind unreachable;
+    }
+    bb6: {
+        _36 = (_3, _7);
+        _37 = (_36.0: u8);
+        _38 = (_36.0: u8);
+        _40 = &_37;
+        _41 = &_38;
+        _39 = (move _40, move _41);
+        _42 = (_39.0: &u8);
+        _43 = (_39.1: &u8);
+        _45 = (*_42);
+        _46 = (*_43);
+        _44 = Eq(move _45, move _46);
+        switchInt(move _44) -> [0: bb9, otherwise: bb8];
+    }
+    bb7: {
+        _33 = core::panicking::AssertKind::Eq;
+        _35 = std::option::Option::None;
+        _34 = core::panicking::assert_failed::<u8, u8>(move _33, _28, _29, move _35) -> unwind unreachable;
+    }
+    bb8: {
+        _52 = &_2;
+        _51 = move _52 as &[u8];
+        _50 = PtrMetadata(move _51);
+        _54 = &_50;
+        _53 = std::mem::size_of_val::<usize>(_54) -> [return: bb10, unwind unreachable];
+    }
+    bb9: {
+        _47 = core::panicking::AssertKind::Eq;
+        _49 = std::option::Option::None;
+        _48 = core::panicking::assert_failed::<u8, u8>(move _47, _42, _43, move _49) -> unwind unreachable;
+    }
+    bb10: {
+        _56 = &_50;
+        _57 = &_53;
+        _55 = (move _56, move _57);
+        _58 = (_55.0: &usize);
+        _59 = (_55.1: &usize);
+        _61 = (*_58);
+        _62 = (*_59);
+        _60 = Eq(move _61, move _62);
+        switchInt(move _60) -> [0: bb12, otherwise: bb11];
+    }
+    bb11: {
+        return;
+    }
+    bb12: {
+        _63 = core::panicking::AssertKind::Eq;
+        _65 = std::option::Option::None;
+        _64 = core::panicking::assert_failed::<usize, usize>(move _63, _58, _59, move _65) -> unwind unreachable;
+    }
+}
+fn operands::{constant#0}() -> usize {
+    let mut _0: usize;
+    bb0: {
+        _0 = 10_usize;
+        return;
+    }
+}
+fn more_operands() -> [Ctors; 3] {
+    let mut _0: [Ctors; 3];
+    let  _1: Dummy;
+    let  _2: Ctors;
+    let  _3: Ctors;
+    let  _4: Ctors;
+    debug dummy => _1;
+    debug unit => _2;
+    debug struct_like => _3;
+    debug tup_like => _4;
+    bb0: {
+        _1 = Dummy('a', core::num::<impl i32>::MIN);
+        _2 = Ctors::Unit;
+        _3 = Ctors::StructLike(move _1);
+        _4 = Ctors::TupLike(false);
+        _0 = [move _2, move _3, move _4];
+        return;
+    }
+}
+fn more_operands::{constant#0}() -> usize {
+    let mut _0: usize;
+    bb0: {
+        _0 = 3_usize;
+        return;
+    }
+}
+fn closures(_1: bool, _2: bool) -> {closure@$DIR/operands.rs:47:5: 47:19} {
+    let mut _0: {closure@$DIR/operands.rs:47:5: 47:19};
+    debug x => _1;
+    debug z => _2;
+    bb0: {
+        _0 = {closure@$DIR/operands.rs:47:5: 47:19}(_1, _2);
+        return;
+    }
+}
+fn closures::{closure#0}(_1: {closure@$DIR/operands.rs:47:5: 47:19}, _2: bool) -> bool {
+    let mut _0: bool;
+    let mut _3: bool;
+    let mut _4: bool;
+    debug y => _2;
+    debug x => (_1.0: bool);
+    debug z => (_1.1: bool);
+    bb0: {
+        _4 = (_1.0: bool);
+        _3 = BitXor(move _4, _2);
+        switchInt(move _3) -> [0: bb2, otherwise: bb1];
+    }
+    bb1: {
+        _0 = true;
+        goto -> bb3;
+    }
+    bb2: {
+        _0 = (_1.1: bool);
+        goto -> bb3;
+    }
+    bb3: {
+        return;
+    }
+}
+fn Ctors::TupLike(_1: bool) -> Ctors {
+    let mut _0: Ctors;
+    bb0: {
+        _0 = Ctors::TupLike(move _1);
+        return;
+    }
+}

tests/ui/std/channel-stack-overflow-issue-102246.rs

@@ -0,0 +1,29 @@
+//@ run-pass
+//@ needs-threads
+//@ compile-flags: -Copt-level=0
+
+// The channel's `Block::new` was causing a stack overflow because it held 32 item slots, which is
+// 1MiB for this test's `BigStruct` -- instantiated on the stack before moving to `Box::new`.
+//
+// That block is now initialized directly on the heap.
+//
+// Ref: https://github.com/rust-lang/rust/issues/102246
+
+use std::sync::mpsc::channel;
+use std::thread;
+
+const N: usize = 32_768;
+struct BigStruct {
+    _data: [u8; N],
+}
+
+fn main() {
+    let (sender, receiver) = channel::<BigStruct>();
+
+    let thread1 = thread::spawn(move || {
+        sender.send(BigStruct { _data: [0u8; N] }).unwrap();
+    });
+
+    thread1.join().unwrap();
+    for _data in receiver.try_iter() {}
+}