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 <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Alexandre Torgue <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Athira Rajeev <[email protected]>
Cc: Caleb Biggers <[email protected]>
Cc: Eduard Zingerman <[email protected]>
Cc: Florian Fischer <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jing Zhang <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: John Garry <[email protected]>
Cc: Kajol Jain <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Leo Yan <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Maxime Coquelin <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Perry Taylor <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ravi Bangoria <[email protected]>
Cc: Sandipan Das <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Suzuki Poulouse <[email protected]>
Cc: Xing Zhengjun <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 7 insertions, 1 deletions

diff --git a/tools/perf/pmu-events/metric.py b/tools/perf/pmu-events/metric.py
index 77ea6ff98538..8ec0ba884673 100644
--- a/tools/perf/pmu-events/metric.py
+++ b/tools/perf/pmu-events/metric.py
@@ -44,6 +44,9 @@ class Expression:
   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,