Fix rounding error in getLikelyClassesOrMethods

[EgorBo]

It seems that sometimes getLikelyClasses reports that fallback has e.g. 1% likelihood where in fact it's 0. It happens because of the rounding error accumulated in getLikelyClassesOrMethods. It prevents JIT from moving that fallback to a cold section.

[ghost]

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.

Issue Details

---

It seems that sometimes getLikelyClasses reports that fallback has e.g. 1% likelihood where in fact it's 0. It happens because of the rounding error accumulated in getLikelyClassesOrMethods. It prevents JIT from moving that fallback to a cold section.

publicstaticvoidMain(string[]args){for(inti=0;i<200;i++){Test(newMyClass1());Test(newMyClass1());Test(newMyClass1());Test(newMyClass2());Test(newMyClass3());Thread.Sleep(16);}}[MethodImpl(MethodImplOptions.NoInlining)]staticintTest(IValuevalue)=>value.GetValue();

- 1) 00007FFF3995A8C0 (MyClass1) [likelihood:50%]+ 1) 00007FFF3995A8C0 (MyClass1) [likelihood:51%]
2) 00007FFF3995AA88 (MyClass2) [likelihood:37%]
3) 00007FFF3995AC50 (MyClass3) [likelihood:12%]

Author:	EgorBo
Assignees:	EgorBo
Labels:	area-CodeGen-coreclr
Milestone:	-

[AndyAyersMS]

LGTM