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Re: [PATCH 1/2] [GDBserver] Fix compiling conditional expressions accessing registers
- From: "Ulrich Weigand" <uweigand at de dot ibm dot com>
- To: qiyaoltc at gmail dot com (Yao Qi)
- Cc: pierre dot langlois at arm dot com (Pierre Langlois), gdb-patches at sourceware dot org, cole945 at gmail dot com
- Date: Wed, 16 Sep 2015 13:50:13 +0200 (CEST)
- Subject: Re: [PATCH 1/2] [GDBserver] Fix compiling conditional expressions accessing registers
- Authentication-results: sourceware.org; auth=none
Yao Qi wrote:
> Pierre Langlois <email@example.com> writes:
> > This patch fixes this issue by replacing `gdb_agent_get_raw_reg' with a
> > `gdb_agent_get_reg' function which takes the tracepoint context object
> > as argument instead of a raw buffer. Additionally, this patch makes
> > this function architecture independent by initializing the context's
> > regcache early and making `gdb_agent_get_reg' use `collect_register'.
> > As a result, the fast tracepoint context object does not need to
> > contain the raw register buffer.
> The fix looks reasonable to me as it makes no sense to keep two copies
> of registers. I go through this patch, and it looks good to me.
It seems to me this was intended as performance optimization to avoid
having to do the full regcache setup every time a tracepoint is hit,
in case we're not actually tracing registers ...
Not sure whether this is a real performance concern for actual use
cases though. I don't have any actual measurements ...
> This patch invalidates Wei-cheng's patch here
> <https://sourceware.org/ml/gdb-patches/2015-06/msg00587.html> which is
> already approved but not committed.
> If Ulirch/Wei-cheng have no objections, this patch can go in.
Except for the performance question above, I have no objections.
Dr. Ulrich Weigand
GNU/Linux compilers and toolchain