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coverage: Remove all unstable support for MC/DC instrumentation

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Zalathar
2025-08-06 22:02:01 +10:00
parent dc0bae1db7
commit 81ed042c8c
47 changed files with 29 additions and 3045 deletions
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44
compiler/rustc_codegen_llvm/src/builder.rs
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@@ -1886,48 +1886,4 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
) {
self.call_intrinsic("llvm.instrprof.increment", &[], &[fn_name, hash, num_counters, index]);
}
/// Emits a call to `llvm.instrprof.mcdc.parameters`.
///
/// This doesn't produce any code directly, but is used as input by
/// the LLVM pass that handles coverage instrumentation.
///
/// (See clang's [`CodeGenPGO::emitMCDCParameters`] for comparison.)
///
/// [`CodeGenPGO::emitMCDCParameters`]:
/// https://github.com/rust-lang/llvm-project/blob/5399a24/clang/lib/CodeGen/CodeGenPGO.cpp#L1124
#[instrument(level = "debug", skip(self))]
pub(crate) fn mcdc_parameters(
&mut self,
fn_name: &'ll Value,
hash: &'ll Value,
bitmap_bits: &'ll Value,
) {
self.call_intrinsic("llvm.instrprof.mcdc.parameters", &[], &[fn_name, hash, bitmap_bits]);
}
#[instrument(level = "debug", skip(self))]
pub(crate) fn mcdc_tvbitmap_update(
&mut self,
fn_name: &'ll Value,
hash: &'ll Value,
bitmap_index: &'ll Value,
mcdc_temp: &'ll Value,
) {
let args = &[fn_name, hash, bitmap_index, mcdc_temp];
self.call_intrinsic("llvm.instrprof.mcdc.tvbitmap.update", &[], args);
}
#[instrument(level = "debug", skip(self))]
pub(crate) fn mcdc_condbitmap_reset(&mut self, mcdc_temp: &'ll Value) {
self.store(self.const_i32(0), mcdc_temp, self.tcx.data_layout.i32_align.abi);
}
#[instrument(level = "debug", skip(self))]
pub(crate) fn mcdc_condbitmap_update(&mut self, cond_index: &'ll Value, mcdc_temp: &'ll Value) {
let align = self.tcx.data_layout.i32_align.abi;
let current_tv_index = self.load(self.cx.type_i32(), mcdc_temp, align);
let new_tv_index = self.add(current_tv_index, cond_index);
self.store(new_tv_index, mcdc_temp, align);
}
}

76
compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs
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@@ -73,48 +73,6 @@ pub(crate) struct CounterExpression {
pub(crate) rhs: Counter,
}
pub(crate) mod mcdc {
use rustc_middle::mir::coverage::{ConditionId, ConditionInfo, DecisionInfo};
/// Must match the layout of `LLVMRustMCDCDecisionParameters`.
#[repr(C)]
#[derive(Clone, Copy, Debug, Default)]
pub(crate) struct DecisionParameters {
bitmap_idx: u32,
num_conditions: u16,
}
type LLVMConditionId = i16;
/// Must match the layout of `LLVMRustMCDCBranchParameters`.
#[repr(C)]
#[derive(Clone, Copy, Debug, Default)]
pub(crate) struct BranchParameters {
condition_id: LLVMConditionId,
condition_ids: [LLVMConditionId; 2],
}
impl From<ConditionInfo> for BranchParameters {
fn from(value: ConditionInfo) -> Self {
let to_llvm_cond_id = |cond_id: Option<ConditionId>| {
cond_id.and_then(|id| LLVMConditionId::try_from(id.as_usize()).ok()).unwrap_or(-1)
};
let ConditionInfo { condition_id, true_next_id, false_next_id } = value;
Self {
condition_id: to_llvm_cond_id(Some(condition_id)),
condition_ids: [to_llvm_cond_id(false_next_id), to_llvm_cond_id(true_next_id)],
}
}
}
impl From<DecisionInfo> for DecisionParameters {
fn from(info: DecisionInfo) -> Self {
let DecisionInfo { bitmap_idx, num_conditions } = info;
Self { bitmap_idx, num_conditions }
}
}
}
/// A span of source code coordinates to be embedded in coverage metadata.
///
/// Must match the layout of `LLVMRustCoverageSpan`.
@@ -148,26 +106,14 @@ pub(crate) struct Regions {
pub(crate) code_regions: Vec<CodeRegion>,
pub(crate) expansion_regions: Vec<ExpansionRegion>,
pub(crate) branch_regions: Vec<BranchRegion>,
pub(crate) mcdc_branch_regions: Vec<MCDCBranchRegion>,
pub(crate) mcdc_decision_regions: Vec<MCDCDecisionRegion>,
}
impl Regions {
/// Returns true if none of this structure's tables contain any regions.
pub(crate) fn has_no_regions(&self) -> bool {
let Self {
code_regions,
expansion_regions,
branch_regions,
mcdc_branch_regions,
mcdc_decision_regions,
} = self;
let Self { code_regions, expansion_regions, branch_regions } = self;
code_regions.is_empty()
&& expansion_regions.is_empty()
&& branch_regions.is_empty()
&& mcdc_branch_regions.is_empty()
&& mcdc_decision_regions.is_empty()
code_regions.is_empty() && expansion_regions.is_empty() && branch_regions.is_empty()
}
}
@@ -195,21 +141,3 @@ pub(crate) struct BranchRegion {
pub(crate) true_counter: Counter,
pub(crate) false_counter: Counter,
}
/// Must match the layout of `LLVMRustCoverageMCDCBranchRegion`.
#[derive(Clone, Debug)]
#[repr(C)]
pub(crate) struct MCDCBranchRegion {
pub(crate) cov_span: CoverageSpan,
pub(crate) true_counter: Counter,
pub(crate) false_counter: Counter,
pub(crate) mcdc_branch_params: mcdc::BranchParameters,
}
/// Must match the layout of `LLVMRustCoverageMCDCDecisionRegion`.
#[derive(Clone, Debug)]
#[repr(C)]
pub(crate) struct MCDCDecisionRegion {
pub(crate) cov_span: CoverageSpan,
pub(crate) mcdc_decision_params: mcdc::DecisionParameters,
}

12
compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
View File

@@ -63,13 +63,7 @@ pub(crate) fn write_function_mappings_to_buffer(
expressions: &[ffi::CounterExpression],
regions: &ffi::Regions,
) -> Vec<u8> {
let ffi::Regions {
code_regions,
expansion_regions,
branch_regions,
mcdc_branch_regions,
mcdc_decision_regions,
} = regions;
let ffi::Regions { code_regions, expansion_regions, branch_regions } = regions;
// SAFETY:
// - All types are FFI-compatible and have matching representations in Rust/C++.
@@ -87,10 +81,6 @@ pub(crate) fn write_function_mappings_to_buffer(
expansion_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,
)
})

16
compiler/rustc_codegen_llvm/src/coverageinfo/mapgen/covfun.rs
View File

@@ -140,8 +140,6 @@ fn fill_region_tables<'tcx>(
code_regions,
expansion_regions: _, // FIXME(Zalathar): Fill out support for expansion regions
branch_regions,
mcdc_branch_regions,
mcdc_decision_regions,
} = &mut covfun.regions;
// For each counter/region pair in this function+file, convert it to a
@@ -161,20 +159,6 @@ fn fill_region_tables<'tcx>(
false_counter: counter_for_bcb(false_bcb),
});
}
MappingKind::MCDCBranch { true_bcb, false_bcb, mcdc_params } => {
mcdc_branch_regions.push(ffi::MCDCBranchRegion {
cov_span,
true_counter: counter_for_bcb(true_bcb),
false_counter: counter_for_bcb(false_bcb),
mcdc_branch_params: ffi::mcdc::BranchParameters::from(mcdc_params),
});
}
MappingKind::MCDCDecision(mcdc_decision_params) => {
mcdc_decision_regions.push(ffi::MCDCDecisionRegion {
cov_span,
mcdc_decision_params: ffi::mcdc::DecisionParameters::from(mcdc_decision_params),
});
}
}
}
}

86
compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
View File

@@ -1,11 +1,10 @@
use std::cell::{OnceCell, RefCell};
use std::ffi::{CStr, CString};
use rustc_abi::Size;
use rustc_codegen_ssa::traits::{
BuilderMethods, ConstCodegenMethods, CoverageInfoBuilderMethods, MiscCodegenMethods,
ConstCodegenMethods, CoverageInfoBuilderMethods, MiscCodegenMethods,
};
use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
use rustc_data_structures::fx::FxIndexMap;
use rustc_middle::mir::coverage::CoverageKind;
use rustc_middle::ty::Instance;
use tracing::{debug, instrument};
@@ -28,34 +27,13 @@ pub(crate) struct CguCoverageContext<'ll, 'tcx> {
/// symbol name, and `llvm-cov` will exit fatally if it can't resolve that
/// hash back to an entry in the binary's `__llvm_prf_names` linker section.
pub(crate) pgo_func_name_var_map: RefCell<FxIndexMap<Instance<'tcx>, &'ll llvm::Value>>,
pub(crate) mcdc_condition_bitmap_map: RefCell<FxHashMap<Instance<'tcx>, Vec<&'ll llvm::Value>>>,
covfun_section_name: OnceCell<CString>,
}
impl<'ll, 'tcx> CguCoverageContext<'ll, 'tcx> {
pub(crate) fn new() -> Self {
Self {
pgo_func_name_var_map: Default::default(),
mcdc_condition_bitmap_map: Default::default(),
covfun_section_name: Default::default(),
}
}
/// LLVM use a temp value to record evaluated mcdc test vector of each decision, which is
/// called condition bitmap. In order to handle nested decisions, several condition bitmaps can
/// be allocated for a function body. These values are named `mcdc.addr.{i}` and are a 32-bit
/// integers. They respectively hold the condition bitmaps for decisions with a depth of `i`.
fn try_get_mcdc_condition_bitmap(
&self,
instance: &Instance<'tcx>,
decision_depth: u16,
) -> Option<&'ll llvm::Value> {
self.mcdc_condition_bitmap_map
.borrow()
.get(instance)
.and_then(|bitmap_map| bitmap_map.get(decision_depth as usize))
.copied() // Dereference Option<&&Value> to Option<&Value>
Self { pgo_func_name_var_map: Default::default(), covfun_section_name: Default::default() }
}
/// Returns the list of instances considered "used" in this CGU, as
@@ -105,38 +83,6 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
}
impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
fn init_coverage(&mut self, instance: Instance<'tcx>) {
let Some(function_coverage_info) =
self.tcx.instance_mir(instance.def).function_coverage_info.as_deref()
else {
return;
};
// If there are no MC/DC bitmaps to set up, return immediately.
if function_coverage_info.mcdc_bitmap_bits == 0 {
return;
}
let fn_name = self.ensure_pgo_func_name_var(instance);
let hash = self.const_u64(function_coverage_info.function_source_hash);
let bitmap_bits = self.const_u32(function_coverage_info.mcdc_bitmap_bits as u32);
self.mcdc_parameters(fn_name, hash, bitmap_bits);
// Create pointers named `mcdc.addr.{i}` to stack-allocated condition bitmaps.
let mut cond_bitmaps = vec![];
for i in 0..function_coverage_info.mcdc_num_condition_bitmaps {
// MC/DC intrinsics will perform loads/stores that use the ABI default
// alignment for i32, so our variable declaration should match.
let align = self.tcx.data_layout.i32_align.abi;
let cond_bitmap = self.alloca(Size::from_bytes(4), align);
llvm::set_value_name(cond_bitmap, format!("mcdc.addr.{i}").as_bytes());
self.store(self.const_i32(0), cond_bitmap, align);
cond_bitmaps.push(cond_bitmap);
}
self.coverage_cx().mcdc_condition_bitmap_map.borrow_mut().insert(instance, cond_bitmaps);
}
#[instrument(level = "debug", skip(self))]
fn add_coverage(&mut self, instance: Instance<'tcx>, kind: &CoverageKind) {
// Our caller should have already taken care of inlining subtleties,
@@ -153,7 +99,7 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
// When that happens, we currently just discard those statements, so
// the corresponding code will be undercounted.
// FIXME(Zalathar): Find a better solution for mixed-coverage builds.
let Some(coverage_cx) = &bx.cx.coverage_cx else { return };
let Some(_coverage_cx) = &bx.cx.coverage_cx else { return };
let Some(function_coverage_info) =
bx.tcx.instance_mir(instance.def).function_coverage_info.as_deref()
@@ -185,30 +131,6 @@ impl<'tcx> CoverageInfoBuilderMethods<'tcx> for Builder<'_, '_, 'tcx> {
}
// If a BCB doesn't have an associated physical counter, there's nothing to codegen.
CoverageKind::VirtualCounter { .. } => {}
CoverageKind::CondBitmapUpdate { index, decision_depth } => {
let cond_bitmap = coverage_cx
.try_get_mcdc_condition_bitmap(&instance, decision_depth)
.expect("mcdc cond bitmap should have been allocated for updating");
let cond_index = bx.const_i32(index as i32);
bx.mcdc_condbitmap_update(cond_index, cond_bitmap);
}
CoverageKind::TestVectorBitmapUpdate { bitmap_idx, decision_depth } => {
let cond_bitmap =
coverage_cx.try_get_mcdc_condition_bitmap(&instance, decision_depth).expect(
"mcdc cond bitmap should have been allocated for merging \
into the global bitmap",
);
assert!(
bitmap_idx as usize <= function_coverage_info.mcdc_bitmap_bits,
"bitmap index of the decision out of range"
);
let fn_name = bx.ensure_pgo_func_name_var(instance);
let hash = bx.const_u64(function_coverage_info.function_source_hash);
let bitmap_index = bx.const_u32(bitmap_idx);
bx.mcdc_tvbitmap_update(fn_name, hash, bitmap_index, cond_bitmap);
bx.mcdc_condbitmap_reset(cond_bitmap);
}
}
}
}

4
compiler/rustc_codegen_llvm/src/llvm/ffi.rs
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@@ -2056,10 +2056,6 @@ unsafe extern "C" {
NumExpansionRegions: size_t,
BranchRegions: *const crate::coverageinfo::ffi::BranchRegion,
NumBranchRegions: size_t,
MCDCBranchRegions: *const crate::coverageinfo::ffi::MCDCBranchRegion,
NumMCDCBranchRegions: size_t,
MCDCDecisionRegions: *const crate::coverageinfo::ffi::MCDCDecisionRegion,
NumMCDCDecisionRegions: size_t,
BufferOut: &RustString,
);