Reduce time taken to test StackGuard and move to innerloop.

We have a test that verifies that Expression compilation is protected
against stack overflow in the case of compiling deep expression trees,
but forcing a case that would cause such a problem by necessity
requires a large tree that takes a long time to compiile, so the test
is outerloop only.

Forcing the compilation to happen on the smallest possible stack
reduces the size of tree that would risk a stack overflow, and so can
test the same functionality in less than a second.

Do this, and move the test to innerloop.

src/System.Linq.Expressions/tests/CompilerTests.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Runtime.CompilerServices;
+using System.Threading;
 using Xunit;
 
 namespace System.Linq.Expressions.Tests
@@ -11,17 +12,21 @@ public static class CompilerTests
  {
  [Theory]
  [ClassData(typeof(CompilationTypes))]
- [OuterLoop("Takes over a minute to complete")]
  public static void CompileDeepTree_NoStackOverflow(bool useInterpreter)
  {
- var e = (Expression)Expression.Constant(0);
+ Expression e = Expression.Constant(0);
 
- int n = 10000;
+ int n = 100;
 
- for (var i = 0; i < n; i++)
+ for (int i = 0; i < n; i++)
  e = Expression.Add(e, Expression.Constant(1));
 
- Func<int> f = Expression.Lambda<Func<int>>(e).Compile(useInterpreter);
+ Func<int> f = null;
+ // Request a stack size of 1 to get the minimum size allowed.
+ // This reduces the size of tree needed to risk a stack overflow.
+ Thread t = new Thread(() => f = Expression.Lambda<Func<int>>(e).Compile(useInterpreter), 1);
+ t.Start();
+ t.Join();
 
  Assert.Equal(n, f());
  }