如何使用 GNU GAS 或 LLVM 组装 ARM SVE 指令并在 QEMU 上运行它? [英] How to assemble ARM SVE instructions with GNU GAS or LLVM and run it on QEMU?
问题描述
我想玩新的 ARM SVE 指令 使用开源工具.
I want to play with the new ARM SVE instructions using open source tools.
首先，我想在以下位置组装最小示例:https://developer.arm.com/docs/dui0965/latest/getting-started-with-the-sve-compiler/assemble-sve-code
As a start, I would like to assemble the minimal example present at: https://developer.arm.com/docs/dui0965/latest/getting-started-with-the-sve-compiler/assembling-sve-code
// example1.s
.global main
main:
mov x0, 0x90000000
mov x8, xzr
ptrue p0.s //SVE instruction
fcpy z0.s, p0/m, #5.00000000 //SVE instruction
orr w10, wzr, #0x400
loop:
st1w z0.s, p0, [x0, x8, lsl #2] //SVE instruction
incw x8 //SVE instruction
whilelt p0.s, x8, x10 //SVE instruction
b.any loop //SVE instruction
mov w0, wzr
ret
但是，当我在 Ubuntu 16.04 上尝试时:
However, when I try that on my Ubuntu 16.04:
sudo apt-get install binutils-aarch64-linux-gnu
aarch64-linux-gnu-as example1.S
它不识别任何 SVE 汇编指令，例如:
it does not recognize any of the SVE assembly instructions, e.g.:
example1.S:6: Error: unknown mnemonic `ptrue' -- `ptrue p0.s'
我认为这是因为我的 GNU AS 2.26.1 太旧，还没有 SVE 支持.
I think this is because my GNU AS 2.26.1 is too old and does not have SVE support yet.
我也可以使用 LLVM 或任何其他开源汇编程序.
I'm also fine using LLVM or any other open source assembler.
一旦我设法组装，我想在 QEMU 用户模式下运行它，因为 3.0.0 支持 SVE.
Once I manage to assemble, I then want to run it on QEMU user mode since 3.0.0 has SVE support.
推荐答案
带有断言的自动化示例
下面我描述了这个例子是如何实现的.
Below I described how that example was achieved.
组装
Ubuntu 18.04 中的 aarch64-linux-gnu-as 2.30 对于 SVE 来说已经足够新了，这可以从以下位置看出:https://sourceware.org/binutils/docs-2.30/as/AArch64-Extensions.html#AArch64-Extensions
The aarch64-linux-gnu-as 2.30 in Ubuntu 18.04 is already new enough for SVE as can be seen from: https://sourceware.org/binutils/docs-2.30/as/AArch64-Extensions.html#AArch64-Extensions
否则，在 Ubuntu 16.04 上从源代码编译 Binutils 很容易，只需这样做:
Otherwise, compiling Binutils from source is easy on Ubuntu 16.04, just do:
git clone git://sourceware.org/git/binutils-gdb.git
cd binutils-gdb
# master that I tested with.
git checkout 4de5434b694fc260d02610e8e7fec21b2923600a
./configure --target aarch64-elf --prefix "$(pwd)/ble"
make -j `nproc`
make install
我没有签出标签，因为最后一个标签是几个月前的，我不想在引入 SVE 时使用 grep 日志消息 ;-)
I didn't check out to a tag because the last tag is a few months old, and I don't feel like grepping log messages for when SVE was introduced ;-)
然后在 Ubuntu 16.04 上使用编译好的 as 并与打包好的 GCC 链接:
Then use the compiled as and link with the packaged GCC on Ubuntu 16.04:
./binutils-gdb/ble/bin/aarch64-elf-as -c -march=armv8.5-a+sve
-o example1.o example1.S
aarch64-linux-gnu-gcc -march=armv8.5-a -nostdlib -o example1 example1.o
在 Ubuntu 16.04 上，aarch64-linux-gnu-gcc 5.4 没有 -march=armv8.5-a，所以只需使用 -march=armv8-a 应该没问题.无论如何，Ubuntu 16.04 和 18.04 都没有 -march=armv8-a+sve 这将是它到来时的最佳选择.
On Ubuntu 16.04, aarch64-linux-gnu-gcc 5.4 does not have -march=armv8.5-a, so just use -march=armv8-a and it should be fine. In any case, neither Ubuntu 16.04 nor 18.04 has -march=armv8-a+sve which will be the best option when it arrives.
或者，您也可以将以下内容添加到 .S 源代码的开头，而不是传递 -march=armv8.5-a+sve:
Alternatively, instead of passing -march=armv8.5-a+sve, you can also add the following to the start of the .S source code:
.arch armv8.5-a+sve
在 Ubuntu 19.04 Binutils 2.32 上，我也学习并测试了:
On Ubuntu 19.04 Binutils 2.32, I also learnt about and tested:
aarch64-linux-gnu-as -march=all
这也适用于 SVE，我想我将来会使用更多，因为它似乎只是一次性启用所有功能，而不仅仅是 SVE！
which also works for SVE, I think I'll be using more of that in the future, as it seems to just enable all features in one go, not just SVE!
QEMU 模拟
在 QEMU 上逐步调试的过程在以下位置进行了说明:如何在 QEMU 上的 GDB 中单步进行 ARM 汇编?
The procedure to step debug it on QEMU is explained at: How to single step ARM assembly in GDB on QEMU?
首先，我将示例制作成一个最小的自包含 Linux 可执行文件:
First I made the example into a minimal self contained Linux executable:
.data
x: .double 1.5, 2.5, 3.5, 4.5
y: .double 5.0, 6.0, 7.0, 8.0
y_expect: .double 8.0, 11.0, 14.0, 17.0
a: .double 2.0
n: .word 4
.text
.global _start
_start:
ldr x0, =x
ldr x1, =y
ldr x2, =a
ldr x3, =n
bl daxpy
/* exit */
mov x0, #0
mov x8, #93
svc #0
/* Multiply by a scalar and add.
*
* Operation:
*
* Y += a * X
*
* C signature:
*
* void daxpy(double *x, double *y, double *a, int *n)
*
* The name "daxpy" comes from LAPACK:
* http://www.netlib.org/lapack/explore-html/de/da4/group__double__blas__level1_ga8f99d6a644d3396aa32db472e0cfc91c.html
*
* Adapted from: https://alastairreid.github.io/papers/sve-ieee-micro-2017.pdf
*/
daxpy:
ldrsw x3, [x3]
mov x4, #0
whilelt p0.d, x4, x3
ld1rd z0.d, p0/z, [x2]
.loop:
ld1d z1.d, p0/z, [x0, x4, lsl #3]
ld1d z2.d, p0/z, [x1, x4, lsl #3]
fmla z2.d, p0/m, z1.d, z0.d
st1d z2.d, p0, [x1, x4, lsl #3]
incd x4
whilelt p0.d, x4, x3
b.first .loop
ret
你可以运行它:
qemu-aarch64 -L /usr/aarch64-linux-gnu -E LD_BIND_NOW=1 ./example1
然后它很好地退出.
接下来，我们可以进行单步调试以确认总和确实已完成:
Next, we can step debug to confirm that the sum was actually made:
qemu-aarch64 -g 1234 -L /usr/aarch64-linux-gnu -E LD_BIND_NOW=1 ./example1
和:
./binutils-gdb/ble/bin/aarch64-elf-gdb -ex 'file example1'
-ex 'target remote localhost:1234' -ex 'set sysroot /usr/aarch64-linux-gnu'
现在，直接在 bl daxpy 之后，运行:
Now, step up to right after bl daxpy, and run:
>>> p (double[4])y_expect
$1 = {[0] = 8, [1] = 11, [2] = 14, [3] = 17}
>>> p (double[4])y
$2 = {[0] = 8, [1] = 11, [2] = 14, [3] = 17}
这确认总和实际上已按预期完成.
which confirms that the sum was actually done as expected.
观察 SVE 寄存器似乎没有实现，因为我在下面找不到任何东西:https://github.com/qemu/qemu/tree/v3.0.0/gdb-xml 但是通过复制其他FP寄存器来实现应该不会太难吧?提问于:http://lists.nongnu.org/archive/html/qemu-discuss/2018-10/msg00020.html
Observing SVE registers seems unimplemented as I can't find anything under: https://github.com/qemu/qemu/tree/v3.0.0/gdb-xml but it should not be too hard to implement by copying other FP registers? Asked at: http://lists.nongnu.org/archive/html/qemu-discuss/2018-10/msg00020.html
您目前已经可以通过以下方式部分间接地观察它:
You can currently already observe it partially and indirectly by doing:
i r d0 d1 d2
因为 SVE 寄存器 zX 的第一个条目与旧的 vX FP 寄存器共享，但我们根本看不到 p.
because the first entry of SVE register zX is shared with the older vX FP registers, but we can't see p at all.
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