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When we extract coverage spans from MIR, we try to "un-expand" them back to spans that are inside the function's body span. In cases where that doesn't succeed, the current code just swaps in the entire body span instead. But that tends to result in coverage spans that are completely unrelated to the control flow of the affected code, so it's better to just discard those spans.
39 lines
1.6 KiB
Plaintext
39 lines
1.6 KiB
Plaintext
LL| |#![feature(core_intrinsics)]
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LL| |#![feature(coverage_attribute)]
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LL| |// compile-flags: --edition=2021
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LL| |
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LL| |// <https://github.com/rust-lang/rust/issues/116171>
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LL| |// If we instrument a function for coverage, but all of its counter-increment
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LL| |// statements are removed by MIR optimizations, LLVM will think it isn't
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LL| |// instrumented and it will disappear from coverage maps and coverage reports.
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LL| |// Most MIR opts won't cause this because they tend not to remove statements
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LL| |// from bb0, but `UnreachablePropagation` can do so if it sees that bb0 ends
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LL| |// with `TerminatorKind::Unreachable`.
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LL| |
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LL| |use std::hint::{black_box, unreachable_unchecked};
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LL| |
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LL| 0|static UNREACHABLE_CLOSURE: fn() = || unsafe { unreachable_unchecked() };
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LL| |
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LL| 0|fn unreachable_function() {
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LL| 0| unsafe { unreachable_unchecked() }
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LL| |}
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LL| |
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LL| |// Use an intrinsic to more reliably trigger unreachable-propagation.
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LL| 0|fn unreachable_intrinsic() {
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LL| 0| unsafe { std::intrinsics::unreachable() }
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LL| |}
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LL| |
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LL| |#[coverage(off)]
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LL| |fn main() {
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LL| | if black_box(false) {
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LL| | UNREACHABLE_CLOSURE();
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LL| | }
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LL| | if black_box(false) {
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LL| | unreachable_function();
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LL| | }
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LL| | if black_box(false) {
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LL| | unreachable_intrinsic();
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LL| | }
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LL| |}
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