We have recently shipped the PTFs for APAR PH42816, the last of
three USING/DROP enhancements which were designed (with help
from John Ehrman) and prototyped around 2013 (and discussed on
this list at the end of 2014) but set aside because of other
priorities.
This enhancement adds two new optional limit suboperands to the
first operand of the USING instruction:
USING (base,end,lower,upper),...
The lower and upper limits restrict the addressability range
regardless of whether 12-bit or 20-bit addressing is being used.
These can also be used in dependent USING statements to allow
non-contiguous addressing ranges to be based on the same set
of base registers.
See https://www.ibm.com/support/pages/apar/PH42816 for details.
The other two enhancements were 20-bit resolution of dependent
USING (PH42050) and DROP by address (PH42188). These were
followed up by a bug fix (PH42918) because we failed to detect
that the existing routine for 20-bit address resolution could
in obscure cases return a pointer to the wrong USING statement.
Before PH42050, this existing bug could cause incorrect RENT
checks, but otherwise had no impact. However, after PH42050
existing programs could assemble incorrectly (with or without
error messages) so we have marked APAR PH42918 as a PE fix
against PH42050.
Jonathan Scott, HLASM
IBM Hursley, UK
