[PATCH v4 3/3] riscv: Add and use alignment-ignorant memcpy

[Richard Henderson]

On 7/6/23 20:29, Evan Green wrote:
> +	/* Copy the last few individual bytes */
> +	add a3, a1, a2
> +5:
> +	lb a4, 0(a1)
> +	addi a1, a1, 1
> +	sb a4, 0(t6)
> +	addi t6, t6, 1
> +	bltu a1, a3, 5b
> +6:
> +	ret

The only time you should be copying individual bytes is when the copy is smaller than 
SZREG.  Otherwise the tail can be handled like

	add	srcend, a1, a2
	add	dstend, a0, a2
	REG_L	tmp, -SZREG(srcend)
	REG_S	tmp, -SZREG(dstend)

There are other tricks that can be used to reduce the number of branches -- please examine 
the x86 code.  See e.g. the copy_0_15 block in sysdeps/x86_64/multiarch/memmove-ssse3.S.


r~