All,
This instruction might just help me with a software product issue on VSEn.
Can someone post an example the correct setup for R2 (the EAX) in a TAP
test, as used on z/OS?
Tony Thigpen
John Dravnieks wrote on 1/14/25 2:38 AM:
Hello
I have come across some usage of the Test Access instruction (TAR) in a problem
state program - given that TAR is documented in Chapter 10 of Pop (usually the
supervisor state instructions generally only of use to the operating system) I
am concerned that TAR is being used incorrectly
The code correctly loads an access register into AR7 and then has this:
TAR R7,R0 Valid access register?
JP AOK Yes
The second operand R0 refers to general register 0, which has a positive value
of 32768 or less - so bits 32-47 of gpr0 will be zero so the effective EAX used
by TAR will be zero.
My question is is this a valid way to test the validity of an access register?
And should it also be checking for a condition code of 1 as well ?
Kind regards
John Dravnieks, 21CS Software
(posted here at suggestion of Binyamin Dissen)
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