perf arm-spe: Support previous branch target (PBT) address

perf arm-spe: Support previous branch target (PBT) address

When FEAT_SPE_PBT is implemented, the previous branch target address
(named as PBT) before the sampled operation, will be recorded.

This commit first introduces a 'prev_br_tgt' field in the record for
saving the PBT address in the decoder.

If the current operation is a branch instruction, by combining with PBT,
it can create a chain with two consecutive branches.  As the branch
stack stores branches in descending order, meaning a newer branch is
stored in a lower entry in the stack.  Arm SPE stores the latest branch
in the first entry of branch stack, and the previous branch coming from
PBT is stored into the second entry.

Otherwise, if current operation is not a branch, the last branch will be
saved for PBT only.  PBT lacks associated information such as branch
source address, branch type, and events.  The branch entry fills zeros
for the corresponding fields and only set its target address.

After:

  perf script -f --itrace=bl -F flags,addr,brstack
  jcc                   ffff800080187914 0xffff8000801878fc/0xffff800080187914/P/-/-/1/COND/-  0x0/0xffff8000801878f8/-/-/-/0//-
  jcc                   ffff8000802d12d8 0xffff8000802d12f8/0xffff8000802d12d8/P/-/-/1/COND/-  0x0/0xffff8000802d12ec/-/-/-/0//-
  jcc                   ffff8000813fe200 0xffff8000813fe20c/0xffff8000813fe200/P/-/-/1/COND/-  0x0/0xffff8000813fe200/-/-/-/0//-
  jcc                   ffff8000813fe200 0xffff8000813fe20c/0xffff8000813fe200/P/-/-/1/COND/-  0x0/0xffff8000813fe200/-/-/-/0//-
  jmp                   ffff800081410980 0xffff800081419108/0xffff800081410980/P/-/-/1//-  0x0/0xffff800081419104/-/-/-/0//-
  return                ffff80008036e064 0xffff80008141ba84/0xffff80008036e064/P/-/-/1/RET/-  0x0/0xffff80008141ba60/-/-/-/0//-
  jcc                   ffff8000803d54f0 0xffff8000803d54e8/0xffff8000803d54f0/P/-/-/1/COND/-  0x0/0xffff8000803d54e0/-/-/-/0//-
  jmp                   ffff80008015e468 0xffff8000803d46dc/0xffff80008015e468/P/-/-/1//-  0x0/0xffff8000803d46c8/-/-/-/0//-
  jmp                   ffff8000806e2d50 0xffff80008040f710/0xffff8000806e2d50/P/-/-/1//-  0x0/0xffff80008040f6e8/-/-/-/0//-
  jcc                   ffff800080721704 0xffff8000807216b4/0xffff800080721704/P/-/-/1/COND/-  0x0/0xffff8000807216ac/-/-/-/0//-

Reviewed-by: Ian Rogers <irogers@google.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
Link: https://lore.kernel.org/r/20250304111240.3378214-13-leo.yan@arm.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>