From 9f35056260dbb71c2da129213ddf90d9e9b4c36b Mon Sep 17 00:00:00 2001 From: Zalathar Date: Sun, 29 Oct 2023 22:33:29 +1100 Subject: [PATCH] coverage: Replace impossible `coverage::Error` with assertions Historically, these errors existed so that the coverage debug code could dump additional information before reporting a compiler bug. That debug code was removed by #115962, so we can now simplify these methods by making them panic when they detect a bug. --- .../src/coverage/counters.rs | 77 ++++++++----------- .../rustc_mir_transform/src/coverage/mod.rs | 17 +--- .../rustc_mir_transform/src/coverage/tests.rs | 4 +- 3 files changed, 32 insertions(+), 66 deletions(-) diff --git a/compiler/rustc_mir_transform/src/coverage/counters.rs b/compiler/rustc_mir_transform/src/coverage/counters.rs index 65696815bb1ed..230d369a9c172 100644 --- a/compiler/rustc_mir_transform/src/coverage/counters.rs +++ b/compiler/rustc_mir_transform/src/coverage/counters.rs @@ -1,5 +1,3 @@ -use super::Error; - use super::graph; use graph::{BasicCoverageBlock, BcbBranch, CoverageGraph, TraverseCoverageGraphWithLoops}; @@ -81,7 +79,7 @@ impl CoverageCounters { &mut self, basic_coverage_blocks: &CoverageGraph, bcb_has_coverage_spans: impl Fn(BasicCoverageBlock) -> bool, - ) -> Result<(), Error> { + ) { MakeBcbCounters::new(self, basic_coverage_blocks).make_bcb_counters(bcb_has_coverage_spans) } @@ -111,11 +109,7 @@ impl CoverageCounters { self.expressions.len() } - fn set_bcb_counter( - &mut self, - bcb: BasicCoverageBlock, - counter_kind: BcbCounter, - ) -> Result { + fn set_bcb_counter(&mut self, bcb: BasicCoverageBlock, counter_kind: BcbCounter) -> CovTerm { assert!( // If the BCB has an edge counter (to be injected into a new `BasicBlock`), it can also // have an expression (to be injected into an existing `BasicBlock` represented by this @@ -126,12 +120,12 @@ impl CoverageCounters { let term = counter_kind.as_term(); if let Some(replaced) = self.bcb_counters[bcb].replace(counter_kind) { - Error::from_string(format!( + bug!( "attempt to set a BasicCoverageBlock coverage counter more than once; \ {bcb:?} already had counter {replaced:?}", - )) + ); } else { - Ok(term) + term } } @@ -140,26 +134,26 @@ impl CoverageCounters { from_bcb: BasicCoverageBlock, to_bcb: BasicCoverageBlock, counter_kind: BcbCounter, - ) -> Result { + ) -> CovTerm { // If the BCB has an edge counter (to be injected into a new `BasicBlock`), it can also // have an expression (to be injected into an existing `BasicBlock` represented by this // `BasicCoverageBlock`). if let Some(c) = self.bcb_counter(to_bcb) && !c.is_expression() { - return Error::from_string(format!( + bug!( "attempt to add an incoming edge counter from {from_bcb:?} \ when the target BCB already has {c:?}" - )); + ); } self.bcb_has_incoming_edge_counters.insert(to_bcb); let term = counter_kind.as_term(); if let Some(replaced) = self.bcb_edge_counters.insert((from_bcb, to_bcb), counter_kind) { - Error::from_string(format!( + bug!( "attempt to set an edge counter more than once; from_bcb: \ {from_bcb:?} already had counter {replaced:?}", - )) + ); } else { - Ok(term) + term } } @@ -213,14 +207,7 @@ impl<'a> MakeBcbCounters<'a> { /// One way to predict which branch executes the least is by considering loops. A loop is exited /// at a branch, so the branch that jumps to a `BasicCoverageBlock` outside the loop is almost /// always executed less than the branch that does not exit the loop. - /// - /// Returns any non-code-span expressions created to represent intermediate values (such as to - /// add two counters so the result can be subtracted from another counter), or an Error with - /// message for subsequent debugging. - fn make_bcb_counters( - &mut self, - bcb_has_coverage_spans: impl Fn(BasicCoverageBlock) -> bool, - ) -> Result<(), Error> { + fn make_bcb_counters(&mut self, bcb_has_coverage_spans: impl Fn(BasicCoverageBlock) -> bool) { debug!("make_bcb_counters(): adding a counter or expression to each BasicCoverageBlock"); // Walk the `CoverageGraph`. For each `BasicCoverageBlock` node with an associated @@ -237,10 +224,10 @@ impl<'a> MakeBcbCounters<'a> { while let Some(bcb) = traversal.next() { if bcb_has_coverage_spans(bcb) { debug!("{:?} has at least one coverage span. Get or make its counter", bcb); - let branching_counter_operand = self.get_or_make_counter_operand(bcb)?; + let branching_counter_operand = self.get_or_make_counter_operand(bcb); if self.bcb_needs_branch_counters(bcb) { - self.make_branch_counters(&traversal, bcb, branching_counter_operand)?; + self.make_branch_counters(&traversal, bcb, branching_counter_operand); } } else { debug!( @@ -251,14 +238,11 @@ impl<'a> MakeBcbCounters<'a> { } } - if traversal.is_complete() { - Ok(()) - } else { - Error::from_string(format!( - "`TraverseCoverageGraphWithLoops` missed some `BasicCoverageBlock`s: {:?}", - traversal.unvisited(), - )) - } + assert!( + traversal.is_complete(), + "`TraverseCoverageGraphWithLoops` missed some `BasicCoverageBlock`s: {:?}", + traversal.unvisited(), + ); } fn make_branch_counters( @@ -266,7 +250,7 @@ impl<'a> MakeBcbCounters<'a> { traversal: &TraverseCoverageGraphWithLoops<'_>, branching_bcb: BasicCoverageBlock, branching_counter_operand: CovTerm, - ) -> Result<(), Error> { + ) { let branches = self.bcb_branches(branching_bcb); debug!( "{:?} has some branch(es) without counters:\n {}", @@ -299,10 +283,10 @@ impl<'a> MakeBcbCounters<'a> { counter", branch, branching_bcb ); - self.get_or_make_counter_operand(branch.target_bcb)? + self.get_or_make_counter_operand(branch.target_bcb) } else { debug!(" {:?} has multiple incoming edges, so adding an edge counter", branch); - self.get_or_make_edge_counter_operand(branching_bcb, branch.target_bcb)? + self.get_or_make_edge_counter_operand(branching_bcb, branch.target_bcb) }; if let Some(sumup_counter_operand) = some_sumup_counter_operand.replace(branch_counter_operand) @@ -337,19 +321,18 @@ impl<'a> MakeBcbCounters<'a> { debug!("{:?} gets an expression: {:?}", expression_branch, expression); let bcb = expression_branch.target_bcb; if expression_branch.is_only_path_to_target() { - self.coverage_counters.set_bcb_counter(bcb, expression)?; + self.coverage_counters.set_bcb_counter(bcb, expression); } else { - self.coverage_counters.set_bcb_edge_counter(branching_bcb, bcb, expression)?; + self.coverage_counters.set_bcb_edge_counter(branching_bcb, bcb, expression); } - Ok(()) } #[instrument(level = "debug", skip(self))] - fn get_or_make_counter_operand(&mut self, bcb: BasicCoverageBlock) -> Result { + fn get_or_make_counter_operand(&mut self, bcb: BasicCoverageBlock) -> CovTerm { // If the BCB already has a counter, return it. if let Some(counter_kind) = &self.coverage_counters.bcb_counters[bcb] { debug!("{bcb:?} already has a counter: {counter_kind:?}"); - return Ok(counter_kind.as_term()); + return counter_kind.as_term(); } // A BCB with only one incoming edge gets a simple `Counter` (via `make_counter()`). @@ -378,10 +361,10 @@ impl<'a> MakeBcbCounters<'a> { let mut predecessors = self.bcb_predecessors(bcb).to_owned().into_iter(); let first_edge_counter_operand = - self.get_or_make_edge_counter_operand(predecessors.next().unwrap(), bcb)?; + self.get_or_make_edge_counter_operand(predecessors.next().unwrap(), bcb); let mut some_sumup_edge_counter_operand = None; for predecessor in predecessors { - let edge_counter_operand = self.get_or_make_edge_counter_operand(predecessor, bcb)?; + let edge_counter_operand = self.get_or_make_edge_counter_operand(predecessor, bcb); if let Some(sumup_edge_counter_operand) = some_sumup_edge_counter_operand.replace(edge_counter_operand) { @@ -411,7 +394,7 @@ impl<'a> MakeBcbCounters<'a> { &mut self, from_bcb: BasicCoverageBlock, to_bcb: BasicCoverageBlock, - ) -> Result { + ) -> CovTerm { // If the source BCB has only one successor (assumed to be the given target), an edge // counter is unnecessary. Just get or make a counter for the source BCB. let successors = self.bcb_successors(from_bcb).iter(); @@ -424,7 +407,7 @@ impl<'a> MakeBcbCounters<'a> { self.coverage_counters.bcb_edge_counters.get(&(from_bcb, to_bcb)) { debug!("Edge {from_bcb:?}->{to_bcb:?} already has a counter: {counter_kind:?}"); - return Ok(counter_kind.as_term()); + return counter_kind.as_term(); } // Make a new counter to count this edge. diff --git a/compiler/rustc_mir_transform/src/coverage/mod.rs b/compiler/rustc_mir_transform/src/coverage/mod.rs index c9b36ba25ac32..052535350bdda 100644 --- a/compiler/rustc_mir_transform/src/coverage/mod.rs +++ b/compiler/rustc_mir_transform/src/coverage/mod.rs @@ -26,18 +26,6 @@ use rustc_span::def_id::DefId; use rustc_span::source_map::SourceMap; use rustc_span::{ExpnKind, SourceFile, Span, Symbol}; -/// A simple error message wrapper for `coverage::Error`s. -#[derive(Debug)] -struct Error { - message: String, -} - -impl Error { - pub fn from_string(message: String) -> Result { - Err(Self { message }) - } -} - /// Inserts `StatementKind::Coverage` statements that either instrument the binary with injected /// counters, via intrinsic `llvm.instrprof.increment`, and/or inject metadata used during codegen /// to construct the coverage map. @@ -167,10 +155,7 @@ impl<'a, 'tcx> Instrumentor<'a, 'tcx> { // `BasicCoverageBlock`s not already associated with a coverage span. let bcb_has_coverage_spans = |bcb| coverage_spans.bcb_has_coverage_spans(bcb); self.coverage_counters - .make_bcb_counters(&mut self.basic_coverage_blocks, bcb_has_coverage_spans) - .unwrap_or_else(|e| { - bug!("Error processing: {:?}: {:?}", self.mir_body.source.def_id(), e.message) - }); + .make_bcb_counters(&mut self.basic_coverage_blocks, bcb_has_coverage_spans); let mappings = self.create_mappings_and_inject_coverage_statements(&coverage_spans); diff --git a/compiler/rustc_mir_transform/src/coverage/tests.rs b/compiler/rustc_mir_transform/src/coverage/tests.rs index 795cbce963d11..0ba61b478ccb0 100644 --- a/compiler/rustc_mir_transform/src/coverage/tests.rs +++ b/compiler/rustc_mir_transform/src/coverage/tests.rs @@ -653,9 +653,7 @@ fn test_make_bcb_counters() { // BCB counter construction that those BCBs have spans. let bcb_has_coverage_spans = |bcb: BasicCoverageBlock| (1..=2).contains(&bcb.as_usize()); let mut coverage_counters = counters::CoverageCounters::new(&basic_coverage_blocks); - coverage_counters - .make_bcb_counters(&mut basic_coverage_blocks, bcb_has_coverage_spans) - .expect("should be Ok"); + coverage_counters.make_bcb_counters(&mut basic_coverage_blocks, bcb_has_coverage_spans); assert_eq!(coverage_counters.num_expressions(), 0); let_bcb!(1);