From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Thu, 10 Mar 2005 11:34:44 -0700
From: "Ronald G. Minnich" <rminnich@lanl.gov>
To: 9fans@cse.psu.edu
Message-ID: <Pine.LNX.4.58.0503101129220.12217@enigma.lanl.gov>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Subject: [9fans] got it
Topicbox-Message-UUID: 223d1d64-ead0-11e9-9d60-3106f5b1d025


an optimization is dumping onto another, it seems.

on arm.

ulong *x, y[64];

	x = y;
	*x++ = 1;
	*x++ = 2;

assembly gives:

	MOVW	$y-260(SP),R3
	MOVW	$1, R2
	MOVW.P	R2, $4(R3)

so the 260 puts you two words before the first element of Y, I'm guessing
(otherwise it would be y-252, right? 63*4). Then it does a pre-increment
and offset by 4, which puts you right at the first element of y.

Which all fails badly if you're setting x to a constant, as in constant
page table value in memory for startup.

That's my reading anyway.

I'm still unsure, all I know is the .s code looks wrong to me for the l.s
changes I'm making. (I'm too lazy to write assembly, I try to have C
compilers do it for me. Usually works. Maybe not this time.)

ron