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niks_jude
Warnings : 1
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Joined: 01 Dec 2006
Posts: 144
Location: Mumbai
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Can anybody explain the result of this instruction -
NI NOSEP+1,X'0F'
Where NOSEP is a label
NOSEP B SKIP1
LA R8,2
ALIGN1 CLI HALIGN,X'FF'
BER R7 |
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enrico-sorichetti
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Joined: 14 Mar 2007
Posts: 10873
Location: italy
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it turns a branch into a noop
the branch instruction should be x'47xrbddd'
| Code: |
47 - opcode
x - condition code
r - index register
b - base register
ddd - offset |
doing a x'0f' ni on the second byte will turn the x to a 0
usually is a trick ( now frowned upon ) to take a branch the first time and the fall thru the other times |
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niks_jude
Warnings : 1
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Joined: 01 Dec 2006
Posts: 144
Location: Mumbai
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| That helps.Thanks. |
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niks_jude
Warnings : 1
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Joined: 01 Dec 2006
Posts: 144
Location: Mumbai
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Oh I got a little confused, please help-
B EXITLP1
EXITLP2 NI MATCH00X+1,0 (this will branch or not and to which subroutine)
BR R7 |
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enrico-sorichetti
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Joined: 14 Mar 2007
Posts: 10873
Location: italy
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MATCH00X is the branch instruction being modified
if You do not post it we cannot tell
please use the code tag, it will make coding more readable |
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niks_jude
Warnings : 1
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Joined: 01 Dec 2006
Posts: 144
Location: Mumbai
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These are the two labels/subroutines -
| Code: |
MATCH00X B PWRRETN
PWRRETN L R7,SV7A
BR R7 RETURN |
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enrico-sorichetti
Superior Member
Joined: 14 Mar 2007
Posts: 10873
Location: italy
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the logic is the same as before,
the first time the branch will be taken, the second time not...
if You have problems understanding the program flow
it would be wiser to ask Your peers ( application developers ) about it or try to get the original program specificatons |
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Bill O'Boyle
CICS Moderator
Joined: 14 Jan 2008
Posts: 2501
Location: Atlanta, Georgia, USA
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This could open a can of worms if this code is in CICS.
In my previous life, I had to maintain code that altered instructions, without using an EX, such as inserting a length into a subsequent MVC via an STC *+5.
Don't do this....
Regards,
Bill |
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