Generic assembly function

[Clément Jean]

Hi,

I'm currently learning how to write Go assembly on arm64 and I made the following functions:

TEXT ·AddVector16(SB),NOSPLIT,$0-48

MOVD a+0(FP), R0

MOVD a+8(FP), R1

MOVD a+16(FP), R2

MOVD a+24(FP), R3

VMOV R0, V0.D[0]

VMOV R1, V0.D[1]

VMOV R2, V1.D[0]

VMOV R3, V1.D[1]

VADD V1.B16, V0.B16, V0.B16

VMOV V0.D[0], R0

VMOV V0.D[1], R1

MOVD R0, ret+32(FP)

MOVD R1, ret+40(FP)

RET

TEXT ·AddVector32(SB),NOSPLIT,$0-96

MOVD a+0(FP), R0

MOVD a+8(FP), R1

MOVD a+16(FP), R2

MOVD a+24(FP), R3

MOVD a+32(FP), R4

MOVD a+40(FP), R5

MOVD a+48(FP), R6

MOVD a+56(FP), R7

VMOV R0, V0.D[0]

VMOV R1, V0.D[1]

VMOV R2, V1.D[0]

VMOV R3, V1.D[1]

VMOV R4, V2.D[0]

VMOV R5, V2.D[1]

VMOV R6, V3.D[0]

VMOV R7, V3.D[1]

VADD V2.B16, V0.B16, V0.B16

VADD V3.B16, V1.B16, V1.B16

VMOV V0.D[0], R0

VMOV V0.D[1], R1

VMOV V1.D[0], R2

VMOV V1.D[1], R3

MOVD R0, ret+64(FP)

MOVD R1, ret+72(FP)

MOVD R2, ret+80(FP)

MOVD R3, ret+88(FP)

RET

While these work, I'm forced to add the 16 and 32 suffixes. Is there any way to have only one function name and link the assembly to something like:

type Uint8x16 [16]uint8

type Uint8x32 [32]uint8

//go:noescape

func AddVector[T Uint8x16 | Uint8x32](a, b T) T

If there is let me know, otherwise is there some other alternatives?

Btw any feedback on the assembly is welcome, I'm new to it.

[David Finkel]

Unfortunately, I think a suffix is the best you can do without jumping through some serious (and ugly) hoops.

The generics implementation opted for a "stenciling" approach, (and doesn't support specializations) so although the symbols do encode the GC shape a bit.

Here's the design doc for GC Shape Stenciling

https://go.googlesource.com/proposal/+/refs/heads/master/design/generics-implementation-gcshape.md  

 

Btw any feedback on the assembly is welcome, I'm new to it.

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[Clément Jean]

That's what I thought. When I checked the assembly of a generic function I could see the go.shape part and that's what made me think about specialisation.

However, after trying to write that myself it just didn't compile.

I guess, I'll have to do lot of copy pasting ^^

[Clément Jean]

Btw, the assembly code was quite terrible... Here is a new version of it for people interested (feedback still welcomed):

TEXT ·AddVector16(SB),NOSPLIT,$0-48

MOVD $a+0(FP), R0

VLD1.P 32(R0), [V0.D2, V1.D2]

VADD V1.B16, V0.B16, V0.B16

MOVD $ret+32(FP), R0

VST1.P [V0.D2], (R0)

RET

TEXT ·AddVector32(SB),NOSPLIT,$0-96

MOVD $a+0(FP), R0

VLD1.P 64(R0), [V0.D2, V1.D2, V2.D2, V3.D2]

VADD V2.B16, V0.B16, V0.B16

VADD V3.B16, V1.B16, V1.B16

MOVD $ret+64(FP), R0

VST1.P [V0.D2, V1.D2], (R0)

RET