如何在 ARMv8-a 上启用 Aarch32 指令集？

Question

Raspberry Pi 3 uses a Broadcom SoC with and ARMv8 A53 core. It also uses a 32-bit OS based on Debian Jessie. According to ARM's ARM NEON programming quick reference，第 3.2 节，指令集：

The ARMv8-A AArch32 instruction set consists of A32 (ARM instruction set, a 32-bit fixed length instruction set) and T32 (Thumb instruction set, a 16-bit fixed length instruction set; Thumb2 instruction set, 16 or 32-bit length instruction set). It is a superset of the ARMv7-A instruction set, so that it retains the backwards compatibility necessary to run existing software. There are some additions to A32 and T32 to maintain alignment with the A64 instruction set, including NEON division, and the Cryptographic Extension instructions. NEON double precision floating point (IEEE compliance) is also supported.

不久前我在 How to test Aarch32 execution environment on Aarch64? 的 GCC 邮件列表上问了一个类似的问题，但我不太明白答案：

Once you're compiling with an arm toolchain the CRC extension can be enabled through -march=armv8-a+crc or selecting an -mcpu option that enables it. To enable the Crypto extension you'll have to specify the right -mfpu option.

我的问题很简单...如何为 Raspberry Pi 3 启用 CRC 和加密扩展？

以下是一些无效的尝试。

尝试 (4) 类似于我们在 Aarch64 下的原生方式：gcc -march=armv8-a+crc+crypto -mtune=cortex-a53。尝试 (5) 实际上启用了 CRC，但我似乎无法启用任何其他功能，例如 PMULL、PMULL2、AES、SHA1 和 SHA2 .

gcc -D__ARM_FEATURE_CRYPTO -D__ARM_FEATURE_CRC -march=armv8-a+crc+crypto -mcpu=cortex-a53 -mfpu=neon test.cc -o test.exe
gcc -D__ARM_FEATURE_CRYPTO -D__ARM_FEATURE_CRC -march=armv8-a+crc -mcpu=cortex-a53 -mfpu=neon test.cc -o test.exe
gcc -D__ARM_FEATURE_CRYPTO -D__ARM_FEATURE_CRC -march=armv8-a -mcpu=cortex-a53 -mfpu=neon test.cc -o test.exe
gcc -march=armv8-a+crc+crypto -mcpu=cortex-a53 -mfpu=neon test.cc -o test.exe
gcc -march=armv8-a+crc -mcpu=cortex-a53 -mfpu=neon test.cc -o test.exe
gcc -march=armv8-a -mcpu=cortex-a53 -mfpu=neon test.cc -o test.exe

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/arm-linux-gnueabihf/4.9/lto-wrapper
Target: arm-linux-gnueabihf
Configured with: ../src/configure -v --with-pkgversion='Raspbian 4.9.2-10' --with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs --enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.9 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.9 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-libitm --disable-libquadmath --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-armhf/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-armhf --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-armhf --with-arch-directory=arm --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-sjlj-exceptions --with-arch=armv6 --with-fpu=vfp --with-float=hard --enable-checking=release --build=arm-linux-gnueabihf --host=arm-linux-gnueabihf --target=arm-linux-gnueabihf
Thread model: posix
gcc version 4.9.2 (Raspbian 4.9.2-10)

Answer 1

很简单，"the right -mfpu option" 应该是 -mfpu=crypto-neon-fp-armv8。

如何在 ARMv8-a 上启用 Aarch32 指令集？

How to enable Aarch32 instruction set on ARMv8-a?

assembly

gcc

arm

intrinsics