From mboxrd@z Thu Jan  1 00:00:00 1970
From: erik quanstrom <quanstro@quanstro.net>
Date: Wed, 21 Aug 2013 14:36:40 -0400
To: 9fans@9fans.net
Message-ID: <2332222c9f75f30c6395f16787280535@brasstown.quanstro.net>
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Subject: [9fans] more on why vc can't produce amd64 executables
Topicbox-Message-UUID: 73825fce-ead8-11e9-9d60-3106f5b1d025

vc vlongs are broken for cast

for example, _v2uc produces the code:

acid; asm(_v2uc)
_v2uc 0x00005360	MOVW	rv+8(FP),R1
_v2uc+0x4 0x00005364	JMP	(R31)
_v2uc+0x8 0x00005368	AND	$0xff,R1

i think this should be
	MOVW	rv+12(FP),R1
	JMP	(R31)
	AND	$0xff,R1

since the high 32-bits of the vlong should be first, since
this is a BE machine.  perhaps there's supposed to be a
special calling convention for vlongs?

here's an example of the issue:

void
main(void)
{
	uvlong x;

	x = 0x012345678abcdefull;
	print("(uchar)x	%.2ux\n", (uchar)x);
	exits("");
}

mikro; v.x
x = 0012345678abcdef
(uchar)x	ef

marshalling a 64-bit pointer in this way will lay down the
bytes with the hi and lo reversed.

- erik