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Merged
merged 2 commits into from
Sep 22, 2025
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Mark float intrinsics with no preconditions as safe #146683

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clarfonthey Sep 17, 2025
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Mark float intrinsics with no preconditions as safe
clarfonthey Sep 17, 2025
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184 changes: 126 additions & 58 deletions compiler/rustc_hir_analysis/src/check/intrinsic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -64,83 +64,151 @@ fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: LocalDefId) -> hi
// it's usually worth updating that intrinsic's documentation
// to note that it's safe to call, since
// safe extern fns are otherwise unprecedented.
sym::abort

// tidy-alphabetical-start
| sym::abort
| sym::add_with_overflow
| sym::aggregate_raw_ptr
| sym::align_of
| sym::assert_inhabited
| sym::assert_zero_valid
| sym::assert_mem_uninitialized_valid
| sym::assert_zero_valid
| sym::autodiff
| sym::bitreverse
| sym::black_box
| sym::box_new
| sym::breakpoint
| sym::size_of
| sym::align_of
| sym::needs_drop
| sym::bswap
| sym::caller_location
| sym::add_with_overflow
| sym::sub_with_overflow
| sym::mul_with_overflow
| sym::carrying_mul_add
| sym::wrapping_add
| sym::wrapping_sub
| sym::wrapping_mul
| sym::saturating_add
| sym::saturating_sub
| sym::rotate_left
| sym::rotate_right
| sym::ctpop
| sym::ceilf16
| sym::ceilf32
| sym::ceilf64
| sym::ceilf128
| sym::cold_path
| sym::const_eval_select
| sym::contract_check_ensures
| sym::contract_check_requires
| sym::contract_checks
| sym::cosf16
| sym::cosf32
| sym::cosf64
| sym::cosf128
| sym::ctlz
| sym::ctpop
| sym::cttz
| sym::bswap
| sym::bitreverse
| sym::three_way_compare
| sym::discriminant_value
| sym::type_id
| sym::type_id_eq
| sym::select_unpredictable
| sym::cold_path
| sym::ptr_guaranteed_cmp
| sym::minnumf16
| sym::minnumf32
| sym::minnumf64
| sym::minnumf128
| sym::minimumf16
| sym::minimumf32
| sym::minimumf64
| sym::minimumf128
| sym::maxnumf16
| sym::maxnumf32
| sym::maxnumf64
| sym::maxnumf128
| sym::exp2f16
| sym::exp2f32
| sym::exp2f64
| sym::exp2f128
| sym::expf16
| sym::expf32
| sym::expf64
| sym::expf128
| sym::fadd_algebraic
| sym::fdiv_algebraic
| sym::floorf16
| sym::floorf32
| sym::floorf64
| sym::floorf128
| sym::fmaf16
| sym::fmaf32
| sym::fmaf64
| sym::fmaf128
| sym::fmul_algebraic
| sym::fmuladdf16
| sym::fmuladdf32
| sym::fmuladdf64
| sym::fmuladdf128
| sym::forget
| sym::frem_algebraic
| sym::fsub_algebraic
| sym::is_val_statically_known
| sym::log2f16
| sym::log2f32
| sym::log2f64
| sym::log2f128
| sym::log10f16
| sym::log10f32
| sym::log10f64
| sym::log10f128
| sym::logf16
| sym::logf32
| sym::logf64
| sym::logf128
| sym::maximumf16
| sym::maximumf32
| sym::maximumf64
| sym::maximumf128
| sym::rustc_peek
| sym::type_name
| sym::forget
| sym::black_box
| sym::variant_count
| sym::is_val_statically_known
| sym::maxnumf16
| sym::maxnumf32
| sym::maxnumf64
| sym::maxnumf128
| sym::minimumf16
| sym::minimumf32
| sym::minimumf64
| sym::minimumf128
| sym::minnumf16
| sym::minnumf32
| sym::minnumf64
| sym::minnumf128
| sym::mul_with_overflow
| sym::needs_drop
| sym::powf16
| sym::powf32
| sym::powf64
| sym::powf128
| sym::powif16
| sym::powif32
| sym::powif64
| sym::powif128
| sym::prefetch_read_data
| sym::prefetch_read_instruction
| sym::prefetch_write_data
| sym::prefetch_write_instruction
| sym::ptr_guaranteed_cmp
| sym::ptr_mask
| sym::aggregate_raw_ptr
| sym::ptr_metadata
| sym::ub_checks
| sym::contract_checks
| sym::contract_check_requires
| sym::contract_check_ensures
| sym::fadd_algebraic
| sym::fsub_algebraic
| sym::fmul_algebraic
| sym::fdiv_algebraic
| sym::frem_algebraic
| sym::rotate_left
| sym::rotate_right
| sym::round_ties_even_f16
| sym::round_ties_even_f32
| sym::round_ties_even_f64
| sym::round_ties_even_f128
| sym::autodiff
| sym::prefetch_read_data
| sym::prefetch_write_data
| sym::prefetch_read_instruction
| sym::prefetch_write_instruction
| sym::const_eval_select => hir::Safety::Safe,
| sym::roundf16
| sym::roundf32
| sym::roundf64
| sym::roundf128
| sym::rustc_peek
| sym::saturating_add
| sym::saturating_sub
| sym::select_unpredictable
| sym::sinf16
| sym::sinf32
| sym::sinf64
| sym::sinf128
| sym::size_of
| sym::sqrtf16
| sym::sqrtf32
| sym::sqrtf64
| sym::sqrtf128
| sym::sub_with_overflow
| sym::three_way_compare
| sym::truncf16
| sym::truncf32
| sym::truncf64
| sym::truncf128
| sym::type_id
| sym::type_id_eq
| sym::type_name
| sym::ub_checks
| sym::variant_count
| sym::wrapping_add
| sym::wrapping_mul
| sym::wrapping_sub
// tidy-alphabetical-end
=> hir::Safety::Safe,
_ => hir::Safety::Unsafe,
};

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2 changes: 1 addition & 1 deletion library/compiler-builtins/libm/src/math/support/float_traits.rs
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Expand Up @@ -289,7 +289,7 @@ macro_rules! float_impl {
cfg_if! {
// fma is not yet available in `core`
if #[cfg(intrinsics_enabled)] {
unsafe{ core::intrinsics::$fma_intrinsic(self, y, z) }
core::intrinsics::$fma_intrinsic(self, y, z)
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@clarfonthey clarfonthey Sep 17, 2025 •
edited
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I don't think it's possible to make this change separately, unfortunately. The best we could do is allow the lint for an unnecessary unsafe block, but that also would presumably require modifying the code within this crate, so, 🤷🏻

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Yeah there's no problem with this bit 👍

} else {
super::super::$fma_fn(self, y, z)
}
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