USE - use trace in the trace package

Description:

This type of trace will display every instruction which uses one or more specified registers and/or memory locations, provided the instruction making the reference is in one of the specified tracing regions. The following message will be issued requesting the specifications:

enter regs and/or locs to trace:

Any combination of register designators, memory locations or memory location intervals may be given as a response. As with the tracing region specifications, a location or location interval may be suffixed with the letter "A" if it is given as absolute. In this case, the offset will not be added to it.

A    - the A-register
Q    - the Q-register
AQ   - the combined A and Q register
E    - the exponent register
EAQ  - the combined E, A and Q registers
Xn   - index register N (N between 0 and 7)
I    - the indicator registor

Suppose, for example, the user wished to trace (1) all uses of the combined AQ register, (2) references to relative locations 1472, (3) all uses of index registers 1 and 4, and (4) references to any location in the absolute interval from 0 through 143 (slave prefix area). The response would look like this:

enter regs and/or locs to trace: aq,1472,x1,x4,0:143a

Certain types of memory location references are not detected by the trace mechanism for both use and change tracing. One reason for this is that only the effective address of an instruction referencing memory is tested for the use/change conditions. This, of course, precludes the detection of implicit multiple word references, as would be the case with LREG, SREG and double precision instructions. Other undetected references include the following:

locations referenced by repeated instructions.
locations referenced by derail service functions.
uses of address registers or index registers to calculate an effective address; TRACE only makes note of register uses that actually involve changes (loading a value from memory into a register, or changing a value in memory).