Messages in this thread | | | Date | Thu, 5 Sep 2019 09:50:32 +0800 | From | Leo Yan <> | Subject | Re: [PATCH v1 1/3] perf cs-etm: Refactor instruction size handling |
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Hi Mathieu,
On Wed, Sep 04, 2019 at 11:06:10AM -0600, Mathieu Poirier wrote: > On Wed, 4 Sep 2019 at 03:19, Leo Yan <leo.yan@linaro.org> wrote: > > > > Hi Mathieu, > > > > On Tue, Sep 03, 2019 at 04:22:15PM -0600, Mathieu Poirier wrote: > > > On Fri, Aug 30, 2019 at 02:24:19PM +0800, Leo Yan wrote: > > > > There has several code pieces need to know the instruction size, but > > > > now every place calculates the instruction size separately. > > > > > > > > This patch refactors to create a new function cs_etm__instr_size() as > > > > a central place to analyze the instruction length based on ISA type > > > > and instruction value. > > > > > > > > Signed-off-by: Leo Yan <leo.yan@linaro.org> > > > > --- > > > > tools/perf/util/cs-etm.c | 44 +++++++++++++++++++++++++++------------- > > > > 1 file changed, 30 insertions(+), 14 deletions(-) > > > > > > > > diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c > > > > index b3a5daaf1a8f..882a0718033d 100644 > > > > --- a/tools/perf/util/cs-etm.c > > > > +++ b/tools/perf/util/cs-etm.c > > > > @@ -914,6 +914,26 @@ static inline int cs_etm__t32_instr_size(struct cs_etm_queue *etmq, > > > > return ((instrBytes[1] & 0xF8) >= 0xE8) ? 4 : 2; > > > > } > > > > > > > > +static inline int cs_etm__instr_size(struct cs_etm_queue *etmq, > > > > + u8 trace_chan_id, > > > > + enum cs_etm_isa isa, > > > > + u64 addr) > > > > +{ > > > > + int insn_len; > > > > + > > > > + /* > > > > + * T32 instruction size might be 32-bit or 16-bit, decide by calling > > > > + * cs_etm__t32_instr_size(). > > > > + */ > > > > + if (isa == CS_ETM_ISA_T32) > > > > + insn_len = cs_etm__t32_instr_size(etmq, trace_chan_id, addr); > > > > + /* Otherwise, A64 and A32 instruction size are always 32-bit. */ > > > > + else > > > > + insn_len = 4; > > > > + > > > > + return insn_len; > > > > +} > > > > + > > > > static inline u64 cs_etm__first_executed_instr(struct cs_etm_packet *packet) > > > > { > > > > /* Returns 0 for the CS_ETM_DISCONTINUITY packet */ > > > > @@ -938,19 +958,23 @@ static inline u64 cs_etm__instr_addr(struct cs_etm_queue *etmq, > > > > const struct cs_etm_packet *packet, > > > > u64 offset) > > > > { > > > > + int insn_len; > > > > + > > > > if (packet->isa == CS_ETM_ISA_T32) { > > > > u64 addr = packet->start_addr; > > > > > > > > while (offset > 0) { > > > > - addr += cs_etm__t32_instr_size(etmq, > > > > - trace_chan_id, addr); > > > > + addr += cs_etm__instr_size(etmq, trace_chan_id, > > > > + packet->isa, addr); > > > > offset--; > > > > } > > > > return addr; > > > > } > > > > > > > > - /* Assume a 4 byte instruction size (A32/A64) */ > > > > - return packet->start_addr + offset * 4; > > > > + /* Return instruction size for A32/A64 */ > > > > + insn_len = cs_etm__instr_size(etmq, trace_chan_id, > > > > + packet->isa, packet->start_addr); > > > > + return packet->start_addr + offset * insn_len; > > > > > > This patch will work but from where I stand it makes things difficult to > > > understand more than anything else. It is also adding coupling between function > > > cs_etm__instr_addr() and cs_etm__instr_size(), meaning the code needs to be > > > carefully inspected in order to make changes to either one. > > > > My purpose is to use a same place to calculate the instruction > > size, rather than to spread the duplicate codes in several different > > functions. > > > > > Last but not least function cs_etm__instr_size() isn't used in the upcoming > > > patches. I really don't see what is gained here. > > > > Sorry that I forgot to commit my final change into patch 02. > > > > I planed to use cs_etm__instr_size() in patch 02; patch 02 has > > function cs_etm__add_stack_event(), which also needs to get the > > instruction size when it sends stack event. > > > > After apply patch 02, tools/perf/util/cs-etm.c will have below three > > functions to caculate instruction size; this is the main reason I want > > to refactor the code for instruction size. > > > > cs_etm__instr_addr() > > cs_etm__copy_insn() > > cs_etm__add_stack_event() > > > > If this lets code more difficult to understand, will drop it. > > > > I agree with the consolidation but for that to work function > cs_etm__instr_addr() needs to be refactored. Since > cs_etm__instr_size() is already taking care of checking the ISA type > the while() loop in cs_etm__instr_addr() can be done regardless of the > operation mode. That way cs_etm__instr_size() can be changed at will > without breaking anything. > > The downside is that we are doing a few more iterations... Which isn't > that big a deal considering we are in user space. We can think about > some optimisation if it is ever proven to be a bottleneck. > > Let me know if you see a problem with that approach.
Yes, your approach is neat; I will try it in next patch version.
Thanks a lot for suggestion!
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