英文:
Go isn't linking my assembly: undefined external function
问题
我正在尝试编写一些SIMD代码，主要是为了学习目的。我知道Go可以链接汇编代码，但我无法使其正常工作。
这是我能做的最简单的示例（逐元素向量乘法）：
vec_amd64.s（注意：实际文件在RET下面有一个空白行，否则会导致错误）
// func mul(v1, v2 Vec4) Vec4
TEXT .mul(SB),4,$0-48
MOVUPS v1+0(FP), X0
MOVUPS v2+16(FP), X1
MULPS X1, X0
// 也尝试过 ret+32，因为我在某些地方看到过这样的写法
MOVUPS X0, toReturn+32(FP)
RET
vec.go
package simd
type Vec4 [4]float32
func (v1 Vec4) Mul(v2 Vec4) Vec4 {
return Vec4{v1[0] * v2[0], v1[1] * v2[1], v1[2] * v2[2], v1[3] * v2[3]}
}
func mul(v1, v2 Vec4) Vec4
simd_test.go
package simd
import (
"testing"
)
func TestMul(t *testing.T) {
v1 := Vec4{1, 2, 3, 4}
v2 := Vec4{5, 6, 7, 8}
res := v1.Mul(v2)
res2 := mul(v1, v2)
// 在编译成功之前，这里只是一个占位符
if res != res2 {
t.Fatalf("Expected %v; got %v", res, res2)
}
}
当我尝试运行go test时，我得到以下错误：
# testmain
simd.TestMul: 调用外部函数 simd.mul
simd.TestMul: 未定义: simd.mul
go env命令报告我的GOHOSTARCH为amd64，我的Go版本为1.3。为了确认不是架构引起的问题，我找到了另一个使用汇编的包，并删除了除_amd64.s文件以外的所有汇编文件，测试运行正常。
我还尝试将其更改为导出标识符，以防止出现奇怪的问题，但没有成功。我认为我几乎按照math/big等包中的模板进行了操作，所以希望我漏掉的是一些简单明显的东西。
我知道Go至少尝试使用汇编，因为如果我在.s文件中引入语法错误，构建工具会报错。
编辑：
明确一下，go build可以编译通过，但go test会导致出现错误。
英文:
I'm trying to write some SIMD mostly for learning purposes. I know Go can link assembly, but I can't get it to work correctly.
Here's the most minimal example I can make (element-wise vector multiplication):
vec_amd64.s (note: the actual file has a whitespace line under RET since it causes errors otherwise)
// func mul(v1, v2 Vec4) Vec4
TEXT .mul(SB),4,$0-48
MOVUPS v1+0(FP), X0
MOVUPS v2+16(FP), X1
MULPS X1, X0
// also tried ret+32 since I've seen some places do that
MOVUPS X0, toReturn+32(FP)
RET
vec.go
package simd
type Vec4 [4]float32
func (v1 Vec4) Mul(v2 Vec4) Vec4 {
return Vec4{v1[0] * v2[0], v1[1] * v2[1], v1[2] * v2[2], v1[3] * v2[3]}
}
func mul(v1, v2 Vec4) Vec4
simd_test.go
package simd
import (
"testing"
)
func TestMul(t *testing.T) {
v1 := Vec4{1, 2, 3, 4}
v2 := Vec4{5, 6, 7, 8}
res := v1.Mul(v2)
res2 := mul(v1, v2)
// Placeholder until I get it to compile
if res != res2 {
t.Fatalf("Expected %v; got %v", res, res2)
}
}
When I try to run go test I get the error:
# testmain
simd.TestMul: call to external function simd.mul
simd.TestMul: undefined: simd.mul
The go env command reports my GOHOSTARCH to be amd64 and my Go version to be 1.3. To confirm it wasn't the architecture causing the problem, I found another package that uses assembly and deleted all the assembly files except the _amd64.s one and its tests ran fine.
I also tried changing it to an exported identifier in case that was causing weirdness, but no dice. I think I pretty closely followed the template in packages like math/big, so hopefully it's something simple and obvious that I'm missing.
I know that Go is at least trying to use the assembly because if I introduce a syntax error to the .s file the build tool will complain about it.
Edit:
To be clear, go build will compile cleanly, but go test causes the error to appear.
答案1
得分: 96
你正在使用错误的点符号。将
TEXT .mul(SB),4,$0-48
改为
TEXT ·mul(SB),4,$0-48
一切都会正常工作。
英文:
You are using the wrong dot. instead of
TEXT .mul(SB),4,$0-48
write
TEXT ·mul(SB),4,$0-48
and everything works just fine.
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