Issue 020202.1: DW_LNS_set_isa Incomplete
PROBLEM DESCRIPTION NEEDED
Al Dunsmuir posted several questions and proposed changes
on 2 Jan 2002 regarding the interpretation and use of the
line number ISA state register and the DW_LNS_set_isa. After
discussion and clarification, the resulting proposal boiled
down to changing the default initial value of the ISA state
register to 0 (from architecturally defined default) and
adding some clarifying wording.
PROPOSAL
In Section 6.2.2, table of state registers, add the following
to the description of the ISA register:
"The value 0 indicates that the instruction set is not
significant or not yet set. On an architecture that
supports just one instruction set, it follows that that
instruction set is the one to assume."
In the following list of initial states, change the description
of isa to read:
isa 0
and delete the following italic commentary.
RECOMMENDATION
Adopt the proposal.
===============================================================
5/17/2005 Accepted with modifications:
Modify 6.2.2 to read:
isa An unsigned integer whose value encodes the applicable instruction
set architecture for the current instruction.
*The encoding of instruction sets should be shared by all
users of a given architecture. It is recommended that this encoding
be defined by the ABI authoring committee for each architecture.*
At the beginning of each sequence within a line number program, the state of
the registers is:
. . .
isa 0
*The value 0 specifies that the instruction set is the architecturally
determined default instruction set. This may be fixed by the ABI, or it may
be specified by other means, for example, the object file description.*
