Re: [PATCHv2] gdb/x86: handle stap probe arguments in xmm registers

[Tom Tromey <tom@tromey.com>]

>>>>> "Andrew" == Andrew Burgess via Gdb-patches <gdb-patches@sourceware.org> writes:

Andrew> Notice that for both of these probes, the first argument is a uint64_t
Andrew> stored in the xmm1 register.

I wonder how much the ideas in here overlap with Zoran's still-pending
patches to rework the DWARF expression evaluator.  IIUC his work
involved some of this same sort of extraction.  However, since yours is
via the stap probe stuff, there probably isn't much opportunity for code
reuse.

Andrew> architectures this method would fist possibly adjust the register

fist->first

Andrew> Finally, as this patch adds a new operation type, then I need to
Andrew> consider how to generate an agent expression for the new operation
Andrew> type.

Andrew> I have kicked the can down the road a bit on this.

This seems completely fine to me.

Andrew> This is because GDB doesn't currently support placing non-scalar types
Andrew> on the agent expression evaluation stack.  Solving this is clearly
Andrew> related to the original problem, but feels a bit like a second
Andrew> problem.  I'd like to get feedback on whether my approach to solving
Andrew> the original problem is acceptable or not before I start looking at
Andrew> how to handle xmm registers within agent expressions.

Note that there are many things that can't be represented in agent
expressions.  I recall filing a bug report about this -- there are some
DWARF expressions that can't be translated, and IIRC, floating point
isn't handled at all.  So, I wouldn't worry too much about this.  My
sense is that tracepoints aren't used a whole lot.

Anyway your patch looked reasonable to me.

Tom