perf jevents: Add rand support to metrics

rand (reverse and) is useful in the parsing of metric
thresholds. Update the documentation on operator precedence to clarify
the simple expression parser and python differences wrt binary/logical
operators.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Caleb Biggers <caleb.biggers@intel.com>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Florian Fischer <florian.fischer@muhq.space>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jing Zhang <renyu.zj@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Perry Taylor <perry.taylor@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-stm32@st-md-mailman.stormreply.com
Link: https://lore.kernel.org/r/20230219092848.639226-33-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/pmu-events/metric.py

@@ -44,6 +44,9 @@ def __xor__(self, other: Union[int, float, 'Expression']) -> 'Operator':
   def __and__(self, other: Union[int, float, 'Expression']) -> 'Operator':
     return Operator('&', self, other)
 
+  def __rand__(self, other: Union[int, float, 'Expression']) -> 'Operator':
+    return Operator('&', other, self)
+
   def __lt__(self, other: Union[int, float, 'Expression']) -> 'Operator':
     return Operator('<', self, other)
 
@@ -88,7 +91,10 @@ def _Constify(val: Union[bool, int, float, Expression]) -> Expression:
 
 
 # Simple lookup for operator precedence, used to avoid unnecessary
-# brackets. Precedence matches that of python and the simple expression parser.
+# brackets. Precedence matches that of the simple expression parser
+# but differs from python where comparisons are lower precedence than
+# the bitwise &, ^, | but not the logical versions that the expression
+# parser doesn't have.
 _PRECEDENCE = {
     '|': 0,
     '^': 1,