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use cranelift's fma for fmuladdf #1676

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use cranelift's fma for fmuladdf #1676

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e96f332
use f16 fallback for sin and cos
folkertdev Jul 16, 2026
d6c5fbc
use cranelift's fma to lower fmuladd
folkertdev Jul 16, 2026
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19 changes: 11 additions & 8 deletions src/intrinsics/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -297,6 +297,14 @@ pub(crate) fn codegen_intrinsic_call<'tcx>(
target.expect("target for simd intrinsic"),
source_info.span,
);
} else if intrinsic.as_str().starts_with("fmuladdf") {
let [x, y, z] = args else { unreachable!() };

let x = codegen_operand(fx, &x.node).load_scalar(fx);
let y = codegen_operand(fx, &y.node).load_scalar(fx);
let z = codegen_operand(fx, &z.node).load_scalar(fx);

fx.bcx.ins().fma(x, y, z);
} else if codegen_float_intrinsic_call(fx, intrinsic, args, destination) {
let ret_block = fx.get_block(target.expect("target for float intrinsic"));
fx.bcx.ins().jump(ret_block, &[]);
Expand Down Expand Up @@ -367,12 +375,6 @@ fn codegen_float_intrinsic_call<'tcx>(
sym::fmaf64 => ("fma", 3, fx.tcx.types.f64, types::F64),
sym::fmaf128 => ("fmaf128", 3, fx.tcx.types.f128, types::F128),

@folkertdev folkertdev Jul 16, 2026 •
edited by rustbot
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so why don't we also want this for the 4 intrinsics here? It looks to me like fmuladd is not really hooked up to anything at all in core, it just exists as an intrinsic?

View changes since the review


// FIXME: calling `fma` from libc without FMA target feature uses expensive sofware emulation
sym::fmuladdf16 => ("fmaf16", 3, fx.tcx.types.f16, types::F16), // FIXME: use cranelift intrinsic analogous to llvm.fmuladd.f16
sym::fmuladdf32 => ("fmaf", 3, fx.tcx.types.f32, types::F32), // FIXME: use cranelift intrinsic analogous to llvm.fmuladd.f32
sym::fmuladdf64 => ("fma", 3, fx.tcx.types.f64, types::F64), // FIXME: use cranelift intrinsic analogous to llvm.fmuladd.f64
sym::fmuladdf128 => ("fmaf128", 3, fx.tcx.types.f128, types::F128), // FIXME: use cranelift intrinsic analogous to llvm.fmuladd.f128

sym::copysignf16 => ("copysignf16", 2, fx.tcx.types.f16, types::F16),
sym::copysignf32 => ("copysignf", 2, fx.tcx.types.f32, types::F32),
sym::copysignf64 => ("copysign", 2, fx.tcx.types.f64, types::F64),
Expand Down Expand Up @@ -403,15 +405,16 @@ fn codegen_float_intrinsic_call<'tcx>(
sym::roundf64 => ("round", 1, fx.tcx.types.f64, types::F64),
sym::roundf128 => ("roundf128", 1, fx.tcx.types.f128, types::F128),

sym::sinf16 => ("sinf16", 1, fx.tcx.types.f16, types::F16),
sym::sinf16 => return false, // has a fallback via f32
sym::sinf32 => ("sinf", 1, fx.tcx.types.f32, types::F32),
sym::sinf64 => ("sin", 1, fx.tcx.types.f64, types::F64),
sym::sinf128 => ("sinf128", 1, fx.tcx.types.f128, types::F128),

sym::cosf16 => ("cosf16", 1, fx.tcx.types.f16, types::F16),
sym::cosf16 => return false, // has a fallback via f32
sym::cosf32 => ("cosf", 1, fx.tcx.types.f32, types::F32),
sym::cosf64 => ("cos", 1, fx.tcx.types.f64, types::F64),
sym::cosf128 => ("cosf128", 1, fx.tcx.types.f128, types::F128),

_ => return false,
};

Expand Down
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