Re: [PATCH v1 1/3] sparc64: NG4 memset/memcpy 32 bits overflow

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From: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Date: Tue, 28 Feb 2017 09:55:44 -0500

> @@ -252,19 +248,16 @@ FUNC_NAME:	/* %o0=dst, %o1=src, %o2=len */
>  #ifdef MEMCPY_DEBUG
>  	wr		%g0, 0x80, %asi
>  #endif
> -	srlx		%o2, 31, %g2
> -	cmp		%g2, 0
> -	tne		%XCC, 5
>  	PREAMBLE
>  	mov		%o0, %o3
>  	brz,pn		%o2, .Lexit


This limitation was placed here intentionally, because huge values
are %99 of the time bugs and unintentional.

You will see that every assembler optimized memcpy on sparc64 has
this bug trap, not just NG4.

This is a very useful way to find bugs and length {over,under}flows.
Please do not remove it.

If you have to do 4GB or larger copies, do it in pieces or similar.

Thank you.

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