HLASM Language Reference

USING Instruction
Range of a Dependent USING Instruction
The range of a dependent USING instruction (called the dependent USING range)
is either the range as specified by the range end, or the range of the corresponding
USING minus the offset of address within that range, whichever is the lesser. If the
corresponding labeled or ordinary USING assigns more than one base register, the
maximum dependent USING range is the composite USING range of the labeled or
ordinary USING.
If the dependent USING instruction specifies a supporting base address that is
within the range of more than one ordinary USING, the assembler determines
which base register to use during base-displacement resolution as follows:
The assembler computes displacements from the ordinary USING base
address that gives the smallest displacement, and uses the corresponding base
register.
If more than one ordinary USING gives the smallest displacement, the
assembler uses the higher-numbered register for assembling addresses within
the coinciding USING ranges.
Domain of a Dependent USING Instruction
The domain of a dependent USING instruction (called the dependent USING
domain) begins where the dependent USING appears in the source module and
continues until the end of the source module, except when:
You end the domain of the corresponding ordinary USING by specifying the
base register or registers from the ordinary USING instruction in a subsequent
DROP instruction.
You end the domain of the corresponding ordinary USING by specifying the
same base register or registers from the ordinary USING instruction in a
subsequent ordinary USING instruction.
You end the domain of a labeled dependent USING by specifying the label of
the labeled dependent USING in the operand of a subsequent DROP
instruction.
You end the domain of a labeled dependent USING by specifying the label of
the labeled dependent USING in the operand of a subsequent labeled USING
instruction.
When a labeled dependent USING domain is dropped, none of any subordinate
USING domains are dropped. In the following example the labeled dependent
USING BLBL1 is not dropped, even though it appears to be dependent on the
USING ALBL2 that is being dropped:
228 HLASM V1R5 Language Reference