cmd/asm: wrong implement vmov/vld on arm64

[mengzhuo]

What version of Go are you using (go version)?

go 1.10

Does this issue reproduce with the latest release?

yes

What did you do?

Try to compile this code

#include "textflag.h"

TEXT ·asm(SB),NOSPLIT,$0-0
    VMOV        R1, V30.S[1]
    VMOV        R1, V30.S[0]
    VLD1.P    8(R0), V2.D[1]
    VLD1      (R0), V2.B[14]

What did you expect to see?

All instructions compiled.

According to "as" these instructions should be (little endian

   1 0000 3E1C0C4E      mov    v30.s[1], w1
   2 0004 3E1C044E      mov    v30.s[0], w1
   3 0008 0284DF0D      ld1 {v2.d}[0], [x0], #8
   4 000c 0218404D      ld1 {v2.b}[14], [x0]

What did you see instead?

  t_arm64.s:4           0xe6d40                 4e041c3e                VMOV R1, V30.S[0]
  t_arm64.s:5           0xe6d44                 4e041c3e                VMOV R1, V30.S[0]

and

asm: illegal combination: 00008 (/root/go/src/t/t_arm64.s:6)    VLD1.P  8(R0), V2.D[1] PSOREG_8 NONE ELEM, 3 7
asm: illegal combination: 00012 (/root/go/src/t/t_arm64.s:7)    VLD1    (R0), V2.B[14] ZOREG NONE ELEM, 3 7

System details

go version go1.10 linux/arm64
GOARCH="arm64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOEXE=""
GOHOSTARCH="arm64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/root/go"
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_arm64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build937154189=/tmp/go-build -gno-record-gcc-switches"
GOROOT/bin/go version: go version go1.10 linux/arm64
GOROOT/bin/go tool compile -V: compile version go1.10
uname -sr: Linux 4.4.49-s5p6818
Distributor ID: Ubuntu
Description:    Ubuntu 16.04.4 LTS
Release:        16.04
Codename:       xenial
/lib/aarch64-linux-gnu/libc.so.6: GNU C Library (Ubuntu GLIBC 2.23-0ubuntu10) stable release version 2.23, by Roland McGrath et al.
gdb --version: GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1

[mengzhuo]

/cc @cherrymui @randall77

[cherrymui]

We don't support VLD1 load to a single element yet, only a list of arrangements (multiple structures) at the moment. Feel free to add the support :)

It seems the bug is that VMOV R1, V30.S[1] is assembled as VMOV R1, V30.S[0]?

cc @williamweixiao

[mengzhuo]

@cherrymui Well, that's beyond my skillsets.

This CL do has "vld into vector lane"
https://go-review.googlesource.com/c/go/+/77810
However it seems be forgotten.
Maybe we should split it into two CLs?

[cherrymui]

Yeah, splitting that CL to two CLs would be helpful. We can get the toolchain part in first.

[williamweixiao]

It's a known bug to us. I'll let fangming split the CL to fix the toolchain part firstly.
Thanks for raising it!

[gopherbot]

Change https://golang.org/cl/101095 mentions this issue: cmd/asm: add essential instructions for AES-GCM on ARM64

[gopherbot]

Change https://golang.org/cl/101297 mentions this issue: cmd/asm: fix bug about VMOV instruction (move register to vector element) on ARM64

[mengzhuo]

Thanks for fixing VMOV bug.

However
https://go-review.googlesource.com/c/go/+/101095 not closed yet.

reopen this maybe?

[cherrymui]

Ok, reopened.