How to Use SIMD Instructions in Go Assembly

You use SIMD instructions in Go assembly by writing them directly in .s files using the architecture-specific mnemonics (like VADDPS for x86 or VADD for Loong64) and referencing vector registers (like XMM0 or V0). The Go compiler handles the mapping of these instructions to the internal SSA representation and ABI, so you simply define a function with the TEXT directive and emit the instructions.

TEXT ·simdAdd<>(SB), NOSPLIT, $0-32
	MOVL $16, AX
	VMOVDQU 0(SP), X0
	VMOVDQU 16(SP), X1
	VADDPS X0, X1, X0
	VMOVDQU X0, 32(SP)
	RET

This example adds two 128-bit vectors on x86-64. For Loong64, you would use V0 registers and instructions like VADD.W as defined in cmd/asm/internal/arch/loong64.go.

SIMD (Single Instruction, Multiple Data) lets your computer process many numbers at once instead of one by one. In Go, you write these special fast instructions in a separate assembly file, similar to writing a recipe for the CPU to follow directly. It's like using a conveyor belt to paint 100 cars simultaneously instead of painting them one at a time.