Date:   Fri, 28 Oct 2022 10:57:02 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        John Garry <john.garry@...wei.com>,
        Sumanth Korikkar <sumanthk@...ux.ibm.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2] perf jevents: Parse metrics during conversion

On Wed, Oct 12, 2022 at 9:42 AM Ian Rogers <irogers@...gle.com> wrote:
>
> Currently the 'MetricExpr' json value is passed from the json
> file to the pmu-events.c. This change introduces an expression
> tree that is parsed into. The parsing is done largely by using
> operator overloading and python's 'eval' function. Two advantages
> in doing this are:
>
> 1) Broken metrics fail at compile time rather than relying on
>    `perf test` to detect. `perf test` remains relevant for checking
>    event encoding and actual metric use.
>
> 2) The conversion to a string from the tree can minimize the
>    metric's string size, for example, preferring 1e6 over 1000000
>    and removing unnecessary whitespace. On x86 this reduces the
>    string size by 2,823bytes (0.06%).
>
> In future changes it would be possible to programmatically
> generate the json expressions (a single line of text and so a
> pain to write manually) for an architecture using the expression
> tree. This could avoid copy-pasting metrics for all architecture
> variants.
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>

Ping, PTAL.

Thanks,
Ian

> v2. Improvements to type information.
> ---
>  tools/perf/pmu-events/Build          |   2 +-
>  tools/perf/pmu-events/jevents.py     |  11 +-
>  tools/perf/pmu-events/metric.py      | 466 +++++++++++++++++++++++++++
>  tools/perf/pmu-events/metric_test.py | 143 ++++++++
>  4 files changed, 618 insertions(+), 4 deletions(-)
>  create mode 100644 tools/perf/pmu-events/metric.py
>  create mode 100644 tools/perf/pmu-events/metric_test.py
>
> diff --git a/tools/perf/pmu-events/Build b/tools/perf/pmu-events/Build
> index 04ef95174660..15b9e8fdbffa 100644
> --- a/tools/perf/pmu-events/Build
> +++ b/tools/perf/pmu-events/Build
> @@ -21,7 +21,7 @@ $(OUTPUT)pmu-events/pmu-events.c: pmu-events/empty-pmu-events.c
>         $(call rule_mkdir)
>         $(Q)$(call echo-cmd,gen)cp $< $@
>  else
> -$(OUTPUT)pmu-events/pmu-events.c: $(JSON) $(JSON_TEST) $(JEVENTS_PY)
> +$(OUTPUT)pmu-events/pmu-events.c: $(JSON) $(JSON_TEST) $(JEVENTS_PY) pmu-events/metric.py
>         $(call rule_mkdir)
>         $(Q)$(call echo-cmd,gen)$(PYTHON) $(JEVENTS_PY) $(JEVENTS_ARCH) pmu-events/arch $@
>  endif
> diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py
> index 0daa3e007528..81bcbd15c962 100755
> --- a/tools/perf/pmu-events/jevents.py
> +++ b/tools/perf/pmu-events/jevents.py
> @@ -4,6 +4,7 @@
>  import argparse
>  import csv
>  import json
> +import metric
>  import os
>  import sys
>  from typing import (Callable, Dict, Optional, Sequence, Set, Tuple)
> @@ -268,9 +269,9 @@ class JsonEvent:
>      self.metric_name = jd.get('MetricName')
>      self.metric_group = jd.get('MetricGroup')
>      self.metric_constraint = jd.get('MetricConstraint')
> -    self.metric_expr = jd.get('MetricExpr')
> -    if self.metric_expr:
> -      self.metric_expr = self.metric_expr.replace('\\', '\\\\')
> +    self.metric_expr = None
> +    if 'MetricExpr' in jd:
> +       self.metric_expr = metric.ParsePerfJson(jd.get('MetricExpr'))
>      arch_std = jd.get('ArchStdEvent')
>      if precise and self.desc and '(Precise Event)' not in self.desc:
>        extra_desc += ' (Must be precise)' if precise == '2' else (' (Precise '
> @@ -322,6 +323,10 @@ class JsonEvent:
>      s = ''
>      for attr in _json_event_attributes:
>        x = getattr(self, attr)
> +      if x and attr == 'metric_expr':
> +        # Convert parsed metric expressions into a string. Slashes
> +        # must be doubled in the file.
> +        x = x.ToPerfJson().replace('\\', '\\\\')
>        s += f'{x}\\000' if x else '\\000'
>      return s
>
> diff --git a/tools/perf/pmu-events/metric.py b/tools/perf/pmu-events/metric.py
> new file mode 100644
> index 000000000000..542d13300e80
> --- /dev/null
> +++ b/tools/perf/pmu-events/metric.py
> @@ -0,0 +1,466 @@
> +# SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
> +"""Parse or generate representations of perf metrics."""
> +import ast
> +import decimal
> +import re
> +import json
> +from typing import (Optional, Set, Union)
> +
> +class Expression:
> +  """Abstract base class of elements in a metric expression."""
> +
> +  def ToPerfJson(self) -> str:
> +    """Returns a perf json file encoded representation."""
> +    raise NotImplementedError()
> +
> +  def ToPython(self) -> str:
> +    """Returns a python expr parseable representation."""
> +    raise NotImplementedError()
> +
> +  def Simplify(self):
> +    """Returns a simplified version of self."""
> +    raise NotImplementedError()
> +
> +  def Equals(self, other) -> bool:
> +    """Returns true when two expressions are the same."""
> +    raise NotImplementedError()
> +
> +  def __str__(self) -> str:
> +    return self.ToPerfJson()
> +
> +  def __or__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('|', self, other)
> +
> +  def __ror__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('|', other, self)
> +
> +  def __xor__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('^', self, other)
> +
> +  def __and__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('&', self, other)
> +
> +  def __lt__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('<', self, other)
> +
> +  def __gt__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('>', self, other)
> +
> +  def __add__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('+', self, other)
> +
> +  def __radd__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('+', other, self)
> +
> +  def __sub__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('-', self, other)
> +
> +  def __rsub__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('-', other, self)
> +
> +  def __mul__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('*', self, other)
> +
> +  def __rmul__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('*', other, self)
> +
> +  def __truediv__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('/', self, other)
> +
> +  def __rtruediv__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('/', other, self)
> +
> +  def __mod__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> +    return Operator('%', self, other)
> +
> +
> +def _Constify(val: Union[bool, int, float, Expression]) -> Expression:
> +  """Used to ensure that the nodes in the expression tree are all Expression."""
> +  if isinstance(val, bool):
> +    return Constant(1 if val else 0)
> +  if isinstance(val, int) or isinstance(val, float):
> +    return Constant(val)
> +  return val
> +
> +
> +# Simple lookup for operator precedence, used to avoid unnecessary
> +# brackets. Precedence matches that of python and the simple expression parser.
> +_PRECEDENCE = {
> +    '|': 0,
> +    '^': 1,
> +    '&': 2,
> +    '<': 3,
> +    '>': 3,
> +    '+': 4,
> +    '-': 4,
> +    '*': 5,
> +    '/': 5,
> +    '%': 5,
> +}
> +
> +
> +class Operator(Expression):
> +  """Represents a binary operator in the parse tree."""
> +
> +  def __init__(self, operator: str, lhs: Union[int, float, Expression],
> +               rhs: Union[int, float, Expression]):
> +    self.operator = operator
> +    self.lhs = _Constify(lhs)
> +    self.rhs = _Constify(rhs)
> +
> +  def Bracket(self,
> +              other: Expression,
> +              other_str: str,
> +              rhs: bool = False) -> str:
> +    """Returns whether to bracket ``other``
> +
> +    ``other`` is the lhs or rhs, ``other_str`` is ``other`` in the
> +    appropriate string from. If ``other`` is an operator then a
> +    bracket is necessary when this/self operator has higher
> +    precedence. Consider: '(a + b) * c', ``other_str`` will be 'a +
> +    b'. A bracket is necessary as without the bracket 'a + b * c' will
> +    evaluate 'b * c' first. However, '(a * b) + c' doesn't need a
> +    bracket as 'a * b' will always be evaluated first. For 'a / (b *
> +    c)' (ie the same precedence level operations) then we add the
> +    bracket to best match the original input, but not for '(a / b) *
> +    c' where the bracket is unnecessary.
> +    """
> +    if isinstance(other, Operator):
> +      if _PRECEDENCE.get(self.operator, -1) > _PRECEDENCE.get(
> +          other.operator, -1):
> +        return f'({other_str})'
> +      if rhs and _PRECEDENCE.get(self.operator, -1) == _PRECEDENCE.get(
> +          other.operator, -1):
> +        return f'({other_str})'
> +    return other_str
> +
> +  def ToPerfJson(self):
> +    return f'{self.Bracket(self.lhs, self.lhs.ToPerfJson())} {self.operator} ' \
> +      f'{self.Bracket(self.rhs, self.rhs.ToPerfJson(), True)}'
> +
> +  def ToPython(self):
> +    return f'{self.Bracket(self.lhs, self.lhs.ToPython())} {self.operator} ' \
> +      f'{self.Bracket(self.rhs, self.rhs.ToPython(), True)}'
> +
> +  def Simplify(self) -> Expression:
> +    lhs = self.lhs.Simplify()
> +    rhs = self.rhs.Simplify()
> +    if isinstance(lhs, Constant) and isinstance(rhs, Constant):
> +      return Constant(eval(lhs + self.operator + rhs))
> +
> +    if isinstance(self.lhs, Constant):
> +      if (self.operator == '+' or self.operator == '|') and lhs.value == '0':
> +        return rhs
> +
> +      if self.operator == '*' and lhs.value == '0':
> +        return Constant(0)
> +
> +      if self.operator == '*' and lhs.value == '1':
> +        return rhs
> +
> +    if isinstance(rhs, Constant):
> +      if (self.operator == '+' or self.operator == '|') and rhs.value == '0':
> +        return lhs
> +
> +      if self.operator == '*' and rhs.value == '0':
> +        return Constant(0)
> +
> +      if self.operator == '*' and self.rhs.value == '1':
> +        return lhs
> +
> +    return Operator(self.operator, lhs, rhs)
> +
> +  def Equals(self, other: Expression) -> bool:
> +    if isinstance(other, Operator):
> +      return self.operator == other.operator and self.lhs.Equals(
> +          other.lhs) and self.rhs.Equals(other.rhs)
> +    return False
> +
> +class Select(Expression):
> +  """Represents a select ternary in the parse tree."""
> +
> +  def __init__(self, true_val: Union[int, float, Expression],
> +               cond: Union[int, float, Expression],
> +               false_val: Union[int, float, Expression]):
> +    self.true_val = _Constify(true_val)
> +    self.cond = _Constify(cond)
> +    self.false_val = _Constify(false_val)
> +
> +  def ToPerfJson(self):
> +    true_str = self.true_val.ToPerfJson()
> +    cond_str = self.cond.ToPerfJson()
> +    false_str = self.false_val.ToPerfJson()
> +    return f'({true_str} if {cond_str} else {false_str})'
> +
> +  def ToPython(self):
> +    return f'Select({self.true_val.ToPython()}, {self.cond.ToPython()}, ' \
> +      f'{self.false_val.ToPython()})'
> +
> +  def Simplify(self) -> Expression:
> +    cond = self.cond.Simplify()
> +    true_val = self.true_val.Simplify()
> +    false_val = self.false_val.Simplify()
> +    if isinstance(cond, Constant):
> +      return false_val if cond.value == '0' else true_val
> +
> +    if true_val.Equals(false_val):
> +      return true_val
> +
> +    return Select(true_val, cond, false_val)
> +
> +  def Equals(self, other: Expression) -> bool:
> +    if isinstance(other, Select):
> +      return self.cond.Equals(other.cond) and self.false_val.Equals(
> +          other.false_val) and self.true_val.Equals(other.true_val)
> +    return False
> +
> +class Function(Expression):
> +  """A function in an expression like min, max, d_ratio."""
> +
> +  def __init__(self,
> +               fn: str,
> +               lhs: Union[int, float, Expression],
> +               rhs: Optional[Union[int, float, Expression]] = None):
> +    self.fn = fn
> +    self.lhs = _Constify(lhs)
> +    self.rhs = _Constify(rhs)
> +
> +  def ToPerfJson(self):
> +    if self.rhs:
> +      return f'{self.fn}({self.lhs.ToPerfJson()}, {self.rhs.ToPerfJson()})'
> +    else:
> +      return f'{self.fn}({self.lhs.ToPerfJson()})'
> +
> +  def ToPython(self):
> +    if self.rhs:
> +      return f'{self.fn}({self.lhs.ToPython()}, {self.rhs.ToPython()})'
> +    else:
> +      return f'{self.fn}({self.lhs.ToPython()})'
> +
> +  def Simplify(self) -> Expression:
> +    lhs = self.lhs.Simplify()
> +    rhs = self.rhs.Simplify()
> +    if isinstance(lhs, Constant) and isinstance(rhs, Constant):
> +      if self.fn == 'd_ratio':
> +        if rhs.value == '0':
> +          return Constant(0)
> +        Constant(eval(f'{lhs} / {rhs}'))
> +      return Constant(eval(f'{self.fn}({lhs}, {rhs})'))
> +
> +    return Function(self.fn, lhs, rhs)
> +
> +  def Equals(self, other: Expression) -> bool:
> +    if isinstance(other, Function):
> +      return self.fn == other.fn and self.lhs.Equals(
> +          other.lhs) and self.rhs.Equals(other.rhs)
> +    return False
> +
> +
> +class Event(Expression):
> +  """An event in an expression."""
> +
> +  def __init__(self, name: str, legacy_name: str = ''):
> +    self.name = name
> +    self.legacy_name = legacy_name
> +
> +  def ToPerfJson(self):
> +    result = re.sub('/', '@', self.name)
> +    return result
> +
> +  def ToPython(self):
> +    return f'Event(r"{self.name}")'
> +
> +  def Simplify(self) -> Expression:
> +    return self
> +
> +  def Equals(self, other: Expression) -> bool:
> +    return isinstance(other, Event) and self.name == other.name
> +
> +class Constant(Expression):
> +  """A constant within the expression tree."""
> +
> +  def __init__(self, value: Union[float, str]):
> +    ctx = decimal.Context()
> +    ctx.prec = 20
> +    dec = ctx.create_decimal(repr(value) if isinstance(value, float) else value)
> +    self.value = dec.normalize().to_eng_string()
> +    self.value = self.value.replace('+', '')
> +    self.value = self.value.replace('E', 'e')
> +
> +  def ToPerfJson(self):
> +    return self.value
> +
> +  def ToPython(self):
> +    return f'Constant({self.value})'
> +
> +  def Simplify(self) -> Expression:
> +    return self
> +
> +  def Equals(self, other: Expression) -> bool:
> +    return isinstance(other, Constant) and self.value == other.value
> +
> +class Literal(Expression):
> +  """A runtime literal within the expression tree."""
> +
> +  def __init__(self, value: str):
> +    self.value = value
> +
> +  def ToPerfJson(self):
> +    return self.value
> +
> +  def ToPython(self):
> +    return f'Literal({self.value})'
> +
> +  def Simplify(self) -> Expression:
> +    return self
> +
> +  def Equals(self, other: Expression) -> bool:
> +    return isinstance(other, Literal) and self.value == other.value
> +
> +
> +def min(lhs: Union[int, float, Expression], rhs: Union[int, float,
> +                                                       Expression]) -> Function:
> +  return Function('min', lhs, rhs)
> +
> +
> +def max(lhs: Union[int, float, Expression], rhs: Union[int, float,
> +                                                       Expression]) -> Function:
> +  return Function('max', lhs, rhs)
> +
> +
> +def d_ratio(lhs: Union[int, float, Expression],
> +            rhs: Union[int, float, Expression]) -> Function:
> +  return Function('d_ratio', lhs, rhs)
> +
> +
> +def source_count(event: Event) -> Function:
> +  return Function('source_count', event)
> +
> +class Metric:
> +  """An individual metric that will specifiable on the perf command line."""
> +  groups: Set[str]
> +  expr: Expression
> +  scale_unit: str
> +  constraint: bool
> +
> +  def __init__(self,
> +               name: str,
> +               description: str,
> +               expr: Expression,
> +               scale_unit: str,
> +               constraint: bool = False):
> +    self.name = name
> +    self.description = description
> +    self.expr = expr.Simplify()
> +    # Workraound valid_only_metric hiding certain metrics based on unit.
> +    scale_unit = scale_unit.replace('/sec', ' per sec')
> +    if scale_unit[0].isdigit():
> +      self.scale_unit = scale_unit
> +    else:
> +      self.scale_unit = f'1{scale_unit}'
> +    self.constraint = constraint
> +    self.groups = set()
> +
> +  def __lt__(self, other):
> +    """Sort order."""
> +    return self.name < other.name
> +
> +  def AddToMetricGroup(self, group):
> +    """Callback used when being added to a MetricGroup."""
> +    self.groups.add(group.name)
> +
> +  def Flatten(self) -> set:
> +    """Return a leaf metric."""
> +    return set([self])
> +
> +  def ToPerfJson(self):
> +    result = {
> +        'MetricName': self.name,
> +        'MetricGroup': ';'.join(sorted(self.groups)),
> +        'BriefDescription': self.description,
> +        'MetricExpr': self.expr.ToPerfJson(),
> +        'ScaleUnit': self.scale_unit
> +    }
> +    if self.constraint:
> +      result['MetricConstraint'] = 'NO_NMI_WATCHDOG'
> +
> +    return result
> +
> +
> +class _MetricJsonEncoder(json.JSONEncoder):
> +  """Special handling for Metric objects."""
> +
> +  def default(self, obj):
> +    if isinstance(obj, Metric):
> +      return obj.ToPerfJson()
> +    return json.JSONEncoder.default(self, obj)
> +
> +
> +class MetricGroup:
> +  """A group of metrics.
> +
> +  Metric groups may be specificd on the perf command line, but within
> +  the json they aren't encoded. Metrics may be in multiple groups
> +  which can facilitate arrangements similar to trees.
> +  """
> +
> +  def __init__(self, name: str, metric_list: list[Union[Metric,
> +                                                        'MetricGroup']]):
> +    self.name = name
> +    self.metric_list = metric_list
> +    for metric in metric_list:
> +      metric.AddToMetricGroup(self)
> +
> +  def AddToMetricGroup(self, group):
> +    """Callback used when a MetricGroup is added into another."""
> +    for metric in self.metric_list:
> +      metric.AddToMetricGroup(group)
> +
> +  def Flatten(self) -> set:
> +    """Returns a set of all leaf metrics."""
> +    result = set()
> +    for x in self.metric_list:
> +      result = result.union(x.Flatten())
> +
> +    return result
> +
> +  def ToPerfJson(self) -> str:
> +    return json.dumps(sorted(self.Flatten()), indent=2, cls=_MetricJsonEncoder)
> +
> +  def __str__(self) -> str:
> +    return self.ToPerfJson()
> +
> +
> +class _RewriteIfExpToSelect(ast.NodeTransformer):
> +
> +  def visit_IfExp(self, node):
> +    call = ast.Call(
> +        func=ast.Name(id='Select', ctx=ast.Load()),
> +        args=[node.body, node.test, node.orelse],
> +        keywords=[])
> +    ast.copy_location(call, node.test)
> +    return call
> +
> +
> +def ParsePerfJson(orig: str) -> Expression:
> +  """A simple json metric expression decoder.
> +
> +  Converts a json encoded metric expression by way of python's ast and
> +  eval routine. First tokens are mapped to Event calls, then
> +  accidentally converted keywords or literals are mapped to their
> +  appropriate calls. Python's ast is used to match if-else that can't
> +  be handled via operator overloading. Finally the ast is evaluated.
> +  """
> +  py = orig.strip()
> +  py = re.sub(r'([a-zA-Z][^-+/\* \\\(\),]*(?:\\.[^-+/\* \\\(\),]*)*)',
> +              r'Event(r"\1")', py)
> +  py = re.sub(r'#Event\(r"([^"]*)"\)', r'Literal("#\1")', py)
> +  py = re.sub(r'([0-9]+)Event\(r"(e[0-9]+)"\)', r'\1\2', py)
> +  keywords = ['if', 'else', 'min', 'max', 'd_ratio', 'source_count']
> +  for kw in keywords:
> +    py = re.sub(f'Event\(r"{kw}"\)', kw, py)
> +
> +  parsed = ast.parse(py, mode='eval')
> +  _RewriteIfExpToSelect().visit(parsed)
> +  parsed = ast.fix_missing_locations(parsed)
> +  return _Constify(eval(compile(parsed, orig, 'eval')))
> diff --git a/tools/perf/pmu-events/metric_test.py b/tools/perf/pmu-events/metric_test.py
> new file mode 100644
> index 000000000000..3909ca773ca1
> --- /dev/null
> +++ b/tools/perf/pmu-events/metric_test.py
> @@ -0,0 +1,143 @@
> +# SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
> +import unittest
> +from metric import Constant, Event, ParsePerfJson
> +
> +
> +class TestMetricExpressions(unittest.TestCase):
> +
> +  def test_Operators(self):
> +    a = Event('a')
> +    b = Event('b')
> +    self.assertEqual((a | b).ToPerfJson(), 'a | b')
> +    self.assertEqual((a ^ b).ToPerfJson(), 'a ^ b')
> +    self.assertEqual((a & b).ToPerfJson(), 'a & b')
> +    self.assertEqual((a < b).ToPerfJson(), 'a < b')
> +    self.assertEqual((a > b).ToPerfJson(), 'a > b')
> +    self.assertEqual((a + b).ToPerfJson(), 'a + b')
> +    self.assertEqual((a - b).ToPerfJson(), 'a - b')
> +    self.assertEqual((a * b).ToPerfJson(), 'a * b')
> +    self.assertEqual((a / b).ToPerfJson(), 'a / b')
> +    self.assertEqual((a % b).ToPerfJson(), 'a % b')
> +
> +  def test_Brackets(self):
> +    a = Event('a')
> +    b = Event('b')
> +    c = Event('c')
> +    self.assertEqual((a * b + c).ToPerfJson(), 'a * b + c')
> +    self.assertEqual((a + b * c).ToPerfJson(), 'a + b * c')
> +    self.assertEqual(((a + a) + a).ToPerfJson(), 'a + a + a')
> +    self.assertEqual(((a + b) * c).ToPerfJson(), '(a + b) * c')
> +    self.assertEqual((a + (b * c)).ToPerfJson(), 'a + b * c')
> +    self.assertEqual(((a / b) * c).ToPerfJson(), 'a / b * c')
> +    self.assertEqual((a / (b * c)).ToPerfJson(), 'a / (b * c)')
> +
> +  def test_ParsePerfJson(self):
> +    # Based on an example of a real metric.
> +    before = '(a + b + c + d) / (2 * e)'
> +    after = before
> +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> +
> +    # Parsing should handle events with '-' in their name. Note, in
> +    # the json file the '\' are doubled to '\\'.
> +    before = r'topdown\-fe\-bound / topdown\-slots - 1'
> +    after = before
> +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> +
> +    # Parsing should handle escaped modifiers. Note, in the json file
> +    # the '\' are doubled to '\\'.
> +    before = 'arb@...nt\=0x81\,umask\=0x1@ + arb@...nt\=0x84\,umask\=0x1@'
> +    after = before
> +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> +
> +    # Parsing should handle exponents in numbers.
> +    before = r'a + 1e12 + b'
> +    after = before
> +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> +
> +  def test_IfElseTests(self):
> +    # if-else needs rewriting to Select and back.
> +    before = r'Event1 if #smt_on else Event2'
> +    after = f'({before})'
> +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> +
> +    before = r'Event1 if 0 else Event2'
> +    after = f'({before})'
> +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> +
> +    before = r'Event1 if 1 else Event2'
> +    after = f'({before})'
> +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> +
> +    # Ensure the select is evaluate last.
> +    before = r'Event1 + 1 if Event2 < 2 else Event3 + 3'
> +    after = (r'Select(Event(r"Event1") + Constant(1), Event(r"Event2") < '
> +             r'Constant(2), Event(r"Event3") + Constant(3))')
> +    self.assertEqual(ParsePerfJson(before).ToPython(), after)
> +
> +    before = r'Event1 > 1 if Event2 < 2 else Event3 > 3'
> +    after = (r'Select(Event(r"Event1") > Constant(1), Event(r"Event2") < '
> +             r'Constant(2), Event(r"Event3") > Constant(3))')
> +    self.assertEqual(ParsePerfJson(before).ToPython(), after)
> +
> +    before = r'min(a + b if c > 1 else c + d, e + f)'
> +    after = r'min((a + b if c > 1 else c + d), e + f)'
> +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> +
> +  def test_ToPython(self):
> +    # Based on an example of a real metric.
> +    before = '(a + b + c + d) / (2 * e)'
> +    py = ParsePerfJson(before).ToPython()
> +    after = eval(py).ToPerfJson()
> +    self.assertEqual(before, after)
> +
> +  def test_Simplify(self):
> +    before = '1 + 2 + 3'
> +    after = '6'
> +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> +
> +    before = 'a + 0'
> +    after = 'a'
> +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> +
> +    before = '0 + a'
> +    after = 'a'
> +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> +
> +    before = 'a | 0'
> +    after = 'a'
> +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> +
> +    before = '0 | a'
> +    after = 'a'
> +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> +
> +    before = 'a * 0'
> +    after = '0'
> +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> +
> +    before = '0 * a'
> +    after = '0'
> +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> +
> +    before = 'a * 1'
> +    after = 'a'
> +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> +
> +    before = '1 * a'
> +    after = 'a'
> +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> +
> +    before = 'a if 0 else b'
> +    after = 'b'
> +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> +
> +    before = 'a if 1 else b'
> +    after = 'a'
> +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> +
> +    before = 'a if b else a'
> +    after = 'a'
> +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> +
> +if __name__ == '__main__':
> +  unittest.main()
> --
> 2.38.0.rc1.362.ged0d419d3c-goog
>

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