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intrinsics: unify rint, roundeven, nearbyint in a single round_ties_even intrinsic #136543

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merged 3 commits into from
Feb 24, 2025
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intrinsics: unify rint, roundeven, nearbyint in a single round_ties_even intrinsic #136543

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04e7a10
intrinsics: unify rint, roundeven, nearbyint in a single round_ties_e…
RalfJung Feb 4, 2025
d1b34ac
make the new intrinsics safe
RalfJung Feb 22, 2025
b9d0555
add stdarch compatibility hack
RalfJung Feb 23, 2025
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16 changes: 7 additions & 9 deletions compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -340,14 +340,10 @@ fn codegen_float_intrinsic_call<'tcx>(
sym::ceilf64 => ("ceil", 1, fx.tcx.types.f64, types::F64),
sym::truncf32 => ("truncf", 1, fx.tcx.types.f32, types::F32),
sym::truncf64 => ("trunc", 1, fx.tcx.types.f64, types::F64),
sym::rintf32 => ("rintf", 1, fx.tcx.types.f32, types::F32),
sym::rintf64 => ("rint", 1, fx.tcx.types.f64, types::F64),
sym::round_ties_even_f32 => ("rintf", 1, fx.tcx.types.f32, types::F32),
sym::round_ties_even_f64 => ("rint", 1, fx.tcx.types.f64, types::F64),
sym::roundf32 => ("roundf", 1, fx.tcx.types.f32, types::F32),
sym::roundf64 => ("round", 1, fx.tcx.types.f64, types::F64),
sym::roundevenf32 => ("roundevenf", 1, fx.tcx.types.f32, types::F32),
sym::roundevenf64 => ("roundeven", 1, fx.tcx.types.f64, types::F64),
sym::nearbyintf32 => ("nearbyintf", 1, fx.tcx.types.f32, types::F32),
sym::nearbyintf64 => ("nearbyint", 1, fx.tcx.types.f64, types::F64),
sym::sinf32 => ("sinf", 1, fx.tcx.types.f32, types::F32),
sym::sinf64 => ("sin", 1, fx.tcx.types.f64, types::F64),
sym::cosf32 => ("cosf", 1, fx.tcx.types.f32, types::F32),
Expand Down Expand Up @@ -399,16 +395,18 @@ fn codegen_float_intrinsic_call<'tcx>(
| sym::ceilf64
| sym::truncf32
| sym::truncf64
| sym::nearbyintf32
| sym::nearbyintf64
| sym::round_ties_even_f32
| sym::round_ties_even_f64
| sym::sqrtf32
| sym::sqrtf64 => {
let val = match intrinsic {
sym::fabsf32 | sym::fabsf64 => fx.bcx.ins().fabs(args[0]),
sym::floorf32 | sym::floorf64 => fx.bcx.ins().floor(args[0]),
sym::ceilf32 | sym::ceilf64 => fx.bcx.ins().ceil(args[0]),
sym::truncf32 | sym::truncf64 => fx.bcx.ins().trunc(args[0]),
sym::nearbyintf32 | sym::nearbyintf64 => fx.bcx.ins().nearest(args[0]),
sym::round_ties_even_f32 | sym::round_ties_even_f64 => {
fx.bcx.ins().nearest(args[0])
}
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@RalfJung RalfJung Feb 4, 2025 •
edited
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This means the cranelift backend will actually change behavior with this PR -- the round_ties_even functions will lower to the "nearest" instruction rather than to rint libcalls. @bjorn3 is that okay?

I am also surprised to not see a case for round here (rounding half-way cases away from zero); is that the one rounding mode cranelit does not support natively?

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@tgross35 tgross35 Feb 5, 2025 •
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If this ever lowers to nearbyint then we do not currently provide that in libm so there may be linking problems on targets without a system libm. I don't expect this to be a problem for cranelift though.

sym::sqrtf32 | sym::sqrtf64 => fx.bcx.ins().sqrt(args[0]),
_ => unreachable!(),
};
Expand Down
9 changes: 3 additions & 6 deletions compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
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Expand Up @@ -84,14 +84,11 @@ fn get_simple_intrinsic<'gcc, 'tcx>(
sym::ceilf64 => "ceil",
sym::truncf32 => "truncf",
sym::truncf64 => "trunc",
sym::rintf32 => "rintf",
sym::rintf64 => "rint",
sym::nearbyintf32 => "nearbyintf",
sym::nearbyintf64 => "nearbyint",
// We match the LLVM backend and lower this to `rint`.
sym::round_ties_even_f32 => "rintf",
sym::round_ties_even_f64 => "rint",
sym::roundf32 => "roundf",
sym::roundf64 => "round",
sym::roundevenf32 => "roundevenf",
sym::roundevenf64 => "roundeven",
sym::abort => "abort",
_ => return None,
};
Expand Down
22 changes: 8 additions & 14 deletions compiler/rustc_codegen_llvm/src/intrinsic.rs
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Expand Up @@ -126,15 +126,14 @@ fn get_simple_intrinsic<'ll>(
sym::truncf64 => "llvm.trunc.f64",
sym::truncf128 => "llvm.trunc.f128",

sym::rintf16 => "llvm.rint.f16",
sym::rintf32 => "llvm.rint.f32",
sym::rintf64 => "llvm.rint.f64",
sym::rintf128 => "llvm.rint.f128",

sym::nearbyintf16 => "llvm.nearbyint.f16",
sym::nearbyintf32 => "llvm.nearbyint.f32",
sym::nearbyintf64 => "llvm.nearbyint.f64",
sym::nearbyintf128 => "llvm.nearbyint.f128",
// We could use any of `rint`, `nearbyint`, or `roundeven`
// for this -- they are all identical in semantics when
// assuming the default FP environment.
// `rint` is what we used for $forever.
sym::round_ties_even_f16 => "llvm.rint.f16",
sym::round_ties_even_f32 => "llvm.rint.f32",
sym::round_ties_even_f64 => "llvm.rint.f64",
sym::round_ties_even_f128 => "llvm.rint.f128",

sym::roundf16 => "llvm.round.f16",
sym::roundf32 => "llvm.round.f32",
Expand All @@ -143,11 +142,6 @@ fn get_simple_intrinsic<'ll>(

sym::ptr_mask => "llvm.ptrmask",

sym::roundevenf16 => "llvm.roundeven.f16",
sym::roundevenf32 => "llvm.roundeven.f32",
sym::roundevenf64 => "llvm.roundeven.f64",
sym::roundevenf128 => "llvm.roundeven.f128",

_ => return None,
};
Some(cx.get_intrinsic(llvm_name))
Expand Down
22 changes: 8 additions & 14 deletions compiler/rustc_hir_analysis/src/check/intrinsic.rs
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Expand Up @@ -137,6 +137,10 @@ pub fn intrinsic_operation_unsafety(tcx: TyCtxt<'_>, intrinsic_id: LocalDefId) -
| sym::fmul_algebraic
| sym::fdiv_algebraic
| sym::frem_algebraic
| sym::round_ties_even_f16
| sym::round_ties_even_f32
| sym::round_ties_even_f64
| sym::round_ties_even_f128
| sym::const_eval_select => hir::Safety::Safe,
_ => hir::Safety::Unsafe,
};
Expand Down Expand Up @@ -398,26 +402,16 @@ pub fn check_intrinsic_type(
sym::truncf64 => (0, 0, vec![tcx.types.f64], tcx.types.f64),
sym::truncf128 => (0, 0, vec![tcx.types.f128], tcx.types.f128),

sym::rintf16 => (0, 0, vec![tcx.types.f16], tcx.types.f16),
sym::rintf32 => (0, 0, vec![tcx.types.f32], tcx.types.f32),
sym::rintf64 => (0, 0, vec![tcx.types.f64], tcx.types.f64),
sym::rintf128 => (0, 0, vec![tcx.types.f128], tcx.types.f128),

sym::nearbyintf16 => (0, 0, vec![tcx.types.f16], tcx.types.f16),
sym::nearbyintf32 => (0, 0, vec![tcx.types.f32], tcx.types.f32),
sym::nearbyintf64 => (0, 0, vec![tcx.types.f64], tcx.types.f64),
sym::nearbyintf128 => (0, 0, vec![tcx.types.f128], tcx.types.f128),
sym::round_ties_even_f16 => (0, 0, vec![tcx.types.f16], tcx.types.f16),
sym::round_ties_even_f32 => (0, 0, vec![tcx.types.f32], tcx.types.f32),
sym::round_ties_even_f64 => (0, 0, vec![tcx.types.f64], tcx.types.f64),
sym::round_ties_even_f128 => (0, 0, vec![tcx.types.f128], tcx.types.f128),

sym::roundf16 => (0, 0, vec![tcx.types.f16], tcx.types.f16),
sym::roundf32 => (0, 0, vec![tcx.types.f32], tcx.types.f32),
sym::roundf64 => (0, 0, vec![tcx.types.f64], tcx.types.f64),
sym::roundf128 => (0, 0, vec![tcx.types.f128], tcx.types.f128),

sym::roundevenf16 => (0, 0, vec![tcx.types.f16], tcx.types.f16),
sym::roundevenf32 => (0, 0, vec![tcx.types.f32], tcx.types.f32),
sym::roundevenf64 => (0, 0, vec![tcx.types.f64], tcx.types.f64),
sym::roundevenf128 => (0, 0, vec![tcx.types.f128], tcx.types.f128),

sym::volatile_load | sym::unaligned_volatile_load => {
(1, 0, vec![Ty::new_imm_ptr(tcx, param(0))], param(0))
}
Expand Down
16 changes: 4 additions & 12 deletions compiler/rustc_span/src/symbol.rs
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Expand Up @@ -1337,10 +1337,6 @@ symbols! {
native_link_modifiers_whole_archive,
natvis_file,
ne,
nearbyintf128,
nearbyintf16,
nearbyintf32,
nearbyintf64,
needs_allocator,
needs_drop,
needs_panic_runtime,
Expand Down Expand Up @@ -1655,20 +1651,16 @@ symbols! {
return_position_impl_trait_in_trait,
return_type_notation,
rhs,
rintf128,
rintf16,
rintf32,
rintf64,
riscv_target_feature,
rlib,
ropi,
ropi_rwpi: "ropi-rwpi",
rotate_left,
rotate_right,
roundevenf128,
roundevenf16,
roundevenf32,
roundevenf64,
round_ties_even_f128,
round_ties_even_f16,
round_ties_even_f32,
round_ties_even_f64,
roundf128,
roundf16,
roundf32,
Expand Down
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