According to the ESA/390 Principles of Operation (SA22-7201-08), relative
addressing instructions were introduced in 1996.
Relative-long instructions were added in 2000.
Under "Highlights of ESA/390", p. 1-3:
"The immediate-and-relative-instruction facility includes 13 new instructions,
most of which use a halfword-immediate value for either signed-binary
arithmetic operations or relative branching. The facility reduces the need for
general registers, and, in particular, it eliminates the need to use general
registers to address branch targets. As a result, the general registers and
access registers can be allocated more efficiently in programs that require
many registers. (September, 1996)"
Also under "Highlights...", p- 1-5:
"Certain new z/Architecture instructions are available on a model in the
ESA/390 architectural mode when z/Architecture is installed. These new
instructions are highlighted as follows:
...
– BRANCH RELATIVE AND SAVE LONG and BRANCH RELATIVE ON CONDITION LONG are like
the BRANCH RELATIVE AND SAVE and BRANCH RELATIVE ON CONDITION instructions
except that the new instructions use a 32-bit immediate field. This increases
the target range available through relative branching... (October, 2000)"
Under "Summary of changes in Fourth Edition":
The instructions of the immediate and relative-instruction facility are
added.
These are:
...
- BRANCH RELATIVE AND SAVE
- BRANCH RELATIVE ON CONDITION
- BRANCH RELATIVE ON COUNT
- BRANCH RELATIVE ON INDEX HIGH
- BRANCH RELATIVE ON INDEX LOW OR EQUAL
...
Also, under "Summary of changes in Eighth Edition":
The following new instructions that have been placed in both z/Architecture
and ESA/390 are added:
...
- BRANCH RELATIVE AND SAVE LONG
- BRANCH RELATIVE ON CONDITION LONG
...
- LOAD ADDRESS RELATIVE LONG
Looking at the dates, the first machine to support relative addressing (but not
relative-long) was (this is a guess) the IBM 9672 G3 (announced in 1996) or G4
(1997).
All z/Architecture machines, starting with the z900 (announced October 2000),
support relative addressing.
