public Expression <TraceLogFilterPredicate> CreatePredicateExpr(TraceLogFilter filter)
{
var enabled = filter.Conditions.Where(x => x.IsEnabled).ToList();
var includedConds = enabled.Where(x => x.Action == FilterConditionAction.Include);
var excludedConds = enabled.Where(x => x.Action == FilterConditionAction.Exclude);
var includeExpr = ExpressionEx.OrElse(includedConds.Select(CreateComparisonExpr), true);
var excludeExpr = ExpressionEx.OrElse(excludedConds.Select(CreateComparisonExpr), false);
var filterExpr = Expression.AndAlso(includeExpr, Expression.Not(excludeExpr));
return(CreateLambda(filterExpr));
}
public TraceLogFilterPredicate CreatePredicate(TraceLogFilter filter)
{
// Lambdas compiled with LambdaExpression.Compile perform costly
// security checks (SecurityTransparent, APTCA, class access checks
// like SecurityCritical or SecuritySafeCritical, and LinkDemands),
// see clr!JIT_MethodAccessCheck in vm/jithelpers.cpp.
// The only way to avoid these seems to be to use a proper (dynamic)
// assembly. We use a GC-collectable transient assembly to host the
// delegate.
var predicate = CreatePredicateExpr(filter).CompileToTransientAssembly();
// Force JIT-compiling the delegate, executing the pre-stub.
// Otherwise calling the delegate involves calls to:
// clr!PrecodeFixupThunk
// clr!ThePreStub
// clr!PreStubWorker
// ...
// This must be done twice, no idea exactly why.
Warmup(predicate);
Warmup(predicate);
return(predicate);
}
