Implement fjcvtzs under the name __jcvt like the C intrinsic#1938
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folkertdev merged 1 commit intorust-lang:masterfrom Oct 10, 2025
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Implement fjcvtzs under the name __jcvt like the C intrinsic#1938folkertdev merged 1 commit intorust-lang:masterfrom
folkertdev merged 1 commit intorust-lang:masterfrom
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you also need to enable your new feature here for the automated testing to work |
This instruction is only available when the jsconv target_feature is available, so on ARMv8.3 or higher. It is used e.g. by Ruffle[0] to speed up its conversion from f64 to i32, or by any JS engine probably. I’ve picked the stdarch_aarch64_jscvt feature because it’s the name of the FEAT_JSCVT, but hesitated with naming it stdarch_aarch64_jsconv (the name of the target_feature) or stdarch_aarch64_jcvt (the name of the C intrinsic) or stdarch_aarch64_fjcvtzs (the name of the instruction), this choice is purely arbitrary and I guess it could be argued one way or another. I wouldn’t expect it to stay unstable for too long, so ultimately this shouldn’t matter much. This feature is now tracked in this issue[1]. [0] ruffle-rs/ruffle#21780 [1] rust-lang/rust#147555
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Oops, thanks for the hint. |
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In ruffle-rs#21780, an optimisation has been added to use the fjcvtzs ARMv8.3 instruction when available, to convert a f64 into an i32. This made me wonder why core::arch::aarch64 didn’t have an intrinsic for this instruction, so I implemented it in stdarch[1], which got pulled in Rust yesterday[2] (see the tracking issue[3]). This PR makes use of this new intrinsic to remove the unsafe asm!() block, and simplify the code. [1] rust-lang/stdarch#1938 [2] rust-lang/rust#148402 [3] rust-lang/rust#147555
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In ruffle-rs#21780, an optimisation has been added to use the fjcvtzs ARMv8.3 instruction when available, to convert a f64 into an i32. This made me wonder why core::arch::aarch64 didn’t have an intrinsic for this instruction, so I implemented it in stdarch[1], which got pulled in Rust yesterday[2] (see the tracking issue[3]). This PR makes use of this new intrinsic to remove the unsafe asm!() block, and simplify the code. [1] rust-lang/stdarch#1938 [2] rust-lang/rust#148402 [3] rust-lang/rust#147555
linkmauve
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In ruffle-rs#21780, an optimisation has been added to use the fjcvtzs ARMv8.3 instruction when available, to convert a f64 into an i32. This made me wonder why core::arch::aarch64 didn’t have an intrinsic for this instruction, so I implemented it in stdarch[1], which got pulled in Rust yesterday[2] (see the tracking issue[3]). This PR makes use of this new intrinsic to remove the unsafe asm!() block, and simplify the code. [1] rust-lang/stdarch#1938 [2] rust-lang/rust#148402 [3] rust-lang/rust#147555
linkmauve
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Jan 13, 2026
In ruffle-rs#21780, an optimisation has been added to use the fjcvtzs ARMv8.3 instruction when available, to convert a f64 into an i32. This made me wonder why core::arch::aarch64 didn’t have an intrinsic for this instruction, so I implemented it in stdarch[1], which got pulled in Rust yesterday[2] (see the tracking issue[3]). This PR makes use of this new intrinsic to remove the unsafe asm!() block, and simplify the code. [1] rust-lang/stdarch#1938 [2] rust-lang/rust#148402 [3] rust-lang/rust#147555
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This instruction is only available when the
jsconvtarget_feature is available, so on ARMv8.3 or higher.It is used e.g. by Ruffle to speed up its conversion from
f64toi32, or by any JS engine probably.I got redirected to this repository from rust-lang/rust#147517