ASM Support

Build scripts try to enable available CPU optimizations. The table below records ASM/SIMD status where scripts explicitly set ASM, SIMD, hardware-acceleration, NEON, SSE, WebAssembly SIMD, or related options. Web builds enable WebAssembly SIMD, while native assembly paths remain disabled.

Library	Android	iOS / iPadOS	macOS	tvOS	visionOS	Linux	Web
dav1d	all: No	all: No	all: No	all: No	all: No	arm64, x86-64: Yes	Wasm SIMD; asm: No12
ffmpeg	all except x86: Yes; x86: No1	all except x86-64, x86-64-mac-catalyst: Yes; x86-64, x86-64-mac-catalyst: No	arm64: Yes; x86-64: No	arm64, arm64-simulator: Yes; x86-64: No	all: Yes	arm64, x86-64: Yes	Wasm SIMD; simd128: Yes12
gmp	all: No	all: No	all: No	all: No	all: No	linux-gmp: Dep	Wasm SIMD; assembly: No12
gnutls	all except x86: Yes; x86: No	all: Yes	all: Yes	all: Yes	all: Yes	linux-gnutls: Dep	Wasm SIMD12
kvazaar	Not specified	all except x86-64, x86-64-mac-catalyst: Yes; x86-64, x86-64-mac-catalyst: No	arm64: Yes; x86-64: No	arm64, arm64-simulator: Yes; x86-64: No	all: Yes	Not specified	Wasm SIMD12
libaom	arm-v7a: Partial; others: Yes	arm slices: Yes; i386: Partial; x86-64, x86-64-mac-catalyst: No3	arm64: Yes; x86-64: No	arm64, arm64-simulator: Yes; x86-64: No	all: Yes	arm64, x86-64: Yes	Wasm SIMD; target: generic12
libass	arm-v7a, arm-v7a-neon, arm64-v8a, x86: No; x86-64: Yes4	arm slices: No; x86-64, x86-64-mac-catalyst: No; i386: Yes	all: No	all: No	all: No	linux-libass: Dep	Wasm SIMD; asm: No12
libjxl	all: Partial5	all: Partial5	all: Partial5	all: Partial5	all: Partial5	arm64, x86-64: Partial5	Wasm SIMD12
libjpeg-turbo	all: Yes	arm slices: Yes; i386, x86-64, x86-64-mac-catalyst: No; arm64e: Yes2	all: Yes	all: Yes	all: Yes	Not built	Wasm SIMD; turbo SIMD: No12
libpng	arm-v7a: Partial6; others: Yes	all: Yes	all: Yes	all: Yes	all: Yes	linux-zlib/system png deps: Dep	Wasm SIMD12
libtheora	all: Yes	Not specified	Not specified	Not specified	Not specified	linux-libtheora: Dep	Wasm SIMD; asm: No12
libvidstab	arm: SSE disabled; x86-family: Not specified	arm slices: SSE disabled; x86-family: Not specified	arm slices: SSE disabled; x86-family: Not specified	arm slices: SSE disabled; x86-family: Not specified	arm slices: SSE disabled	linux-libvidstab: Dep	Wasm SIMD; SSE: No12
libvpx	arm-v7a: Partial7; others: Yes	armv7, armv7s, i386: Yes; arm64-family: Partial8; x86-64-family: Partial	arm64: Partial8; x86-64: Partial	arm64, arm64-simulator: Partial8; x86-64: Partial	all: Partial8	linux-libvpx: Dep	Wasm SIMD; runtime CPU detect: No12
libwebp	arm-v7a: No; others: Yes	all except x86-64-mac-catalyst: Yes; x86-64-mac-catalyst: No	all: Yes	all: Yes	all: Yes	linux-libwebp: Dep	Wasm SIMD; WebP SIMD: No12
nettle	assembler: No; arch crypto flags: Partial	assembler: No; arch crypto flags: Partial	assembler: No; arch crypto flags: Partial	assembler: No; arch crypto flags: Partial	assembler: No; arch crypto flags: Partial	Not built	Wasm SIMD12
openh264	arm-v7a: No; others: Yes	all except x86-64: Yes; x86-64: No9	arm64: Yes; x86-64: No9	arm64, arm64-simulator: Yes; x86-64: No9	all: Yes	arm64, x86-64: Yes	Wasm SIMD; asm: No12
openssl	all: Yes	arch target selected; 64-bit NIST EC optimization depends on __uint128_t	arch target selected; 64-bit NIST EC optimization depends on __uint128_t	arch target selected; 64-bit NIST EC optimization depends on __uint128_t	arch target selected; 64-bit NIST EC optimization depends on __uint128_t	arm64, x86-64: Yes	Wasm SIMD; asm: No12
opus	all: Yes	all: Yes	all: Yes	all: Yes	all: Yes	linux-opus: Dep	Wasm SIMD; asm: No12
soxr	Not specified	arm64*: Partial; others: Not specified	arm64: Partial; x86-64: Not specified	arm64, arm64-simulator: Partial; x86-64: Not specified	all: Partial	linux-soxr: Dep	Wasm SIMD12
speex	x86, x86-64: Yes; arm: Not specified	x86-family: Yes; arm: Not specified	x86-64: Yes; arm64: Not specified	x86-64: Yes; arm: Not specified	arm: Not specified	linux-speex: Dep	Wasm SIMD12
vo-amrwbenc	arm-v7a-neon: Yes; others: Not specified	Not specified	Not specified	Not specified	Not specified	linux-vo-amrwbenc: Dep	Wasm SIMD12
vvenc	arm-v7a: No; arm-v7a-neon, arm64-v8a: Yes; x86: Not specified	Not specified	Not specified	Not specified	Not specified	arm64: Partial; x86-64: Not specified	Wasm SIMD; native SIMD: No12
x264	all except x86: Yes; x86: No10	arm slices: Yes; i386, x86-64-family: No	arm64: Yes; x86-64: No	arm64, arm64-simulator: Yes; x86-64: No	all: Yes	arm64: Not specified; x86-64: Yes	Wasm SIMD; asm: No12
x265	arm-v7a, arm-v7a-neon, x86: No; arm64-v8a, x86-64: Yes	armv7, armv7s, x86-64: Yes; arm64*, i386, x86-64-mac-catalyst: No	arm64: No; x86-64: Yes	arm64, arm64-simulator: No; x86-64: Yes	all: No	linux-x265: Dep	Wasm SIMD; assembly: No12
xvidcore	all except x86: Yes; x86: No11	arm slices: Yes; i386, x86-64-family: No	arm64: Yes; x86-64: No	arm64, arm64-simulator: Yes; x86-64: No	all: Yes	linux-xvidcore: Dep	Wasm SIMD; assembly: No12
zimg	Not specified	armv7, armv7s: No; others: Yes	all: Yes	all: Yes	all: Yes	Not specified	Wasm SIMD; zimg SIMD: No12

Legend:

Value	Meaning
Yes	ASM/SIMD is explicitly enabled by the script, or the script preserves an ASM-enabled build path.
No	ASM/SIMD is explicitly disabled by the script.
Partial	Some ASM/SIMD families are enabled while others are explicitly disabled.
Wasm SIMD	WebAssembly SIMD is enabled through Emscripten flags for the Web build. This is the Web SIMD support indicator.
Dep	Linux system dependency; ASM status is not known from these scripts.
Not specified	The script does not explicitly set ASM/SIMD-related options.
Not built	No build script exists for that platform in this project.

Notes

1. Android ffmpeg disables asm on x86 because the script references FFmpeg ticket 4928.
2. jpeg leaves the CMake architecture list empty for arm64e because libjpeg-turbo matches it as arm64, but arm64e is not a supported SIMD CPU type.
3. Apple libaom patches aom_ports to disable asm on x86-64-family slices.
4. Android libass disables asm on x86 because enabling it causes text relocations in libavfilter.so.
5. libjxl disables AVX512, AVX512_SPR, AVX512_ZEN4, sizeless vectors, and forced NEON in scripts.
6. Android libpng does not enable hardware optimizations on arm-v7a because that makes the build try ARM-NEON instructions and breaks compilation.
7. Android libvpx disables NEON on arm-v7a because runtime CPU detection enables NEON for armv7 CPU.
8. Apple libvpx enables NEON on arm64-family slices but disables --enable-neon-asm because that option is ARMv7-style 32-bit only; arm64e also disables NEON dotprod due ptrauth issues.
9. Apple openh264 script says ASM is enabled for all iOS architectures except x86-64.
10. Android x264 disables asm on x86 because enabling it causes text relocations in libavfilter.so.
11. Android xvidcore disables assembly on x86 because enabling it causes text relocations in libavcodec.so.
12. Web builds target wasm32-unknown-emscripten and compile with -msimd128; --enable-relaxed-simd additionally adds -mrelaxed-simd. FFmpeg is configured with --enable-simd128 while native asm, inline asm and x86 asm are disabled. Row text such as asm: No, assembly: No, SSE: No, or native SIMD: No means that library's native CPU-specific path is disabled even though WebAssembly SIMD flags are enabled.