JIT: Expand delegate calls early

[jakobbotsch]

We currently expand delegate calls in lowering. There are potential CSE opportunities of the target instance and target address if we expand it in morph, similar to what we do for vtable calls.

@AndyAyersMS had a prototype for dotnet/coreclr here: https://github.com/AndyAyersMS/coreclr/tree/InlineDelegateInvoke

category:cq
theme:delegates
skill-level:expert
cost:medium
impact:medium

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Issue Details

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We currently expand delegate calls in lowering. There are potential CSE opportunities of the target instance and target address if we expand it in morph, similar to what we do for vtable calls.

@AndyAyersMS had a prototype for dotnet/coreclr here: https://github.com/AndyAyersMS/coreclr/tree/InlineDelegateInvoke

Author:	jakobbotsch
Assignees:	jakobbotsch
Labels:	area-CodeGen-coreclr, untriaged
Milestone:	-

[jakobbotsch]

#75841 tried this but doing this early hits some issues due to the JIT sometimes not being smart about the order args are passed in. Will move this to future.

[AndyAyersMS]

@amanasifkhalid FYI

A nice goal here would be for a locally allocated non-escaping delegate to get stack allocated, physically promoted, and then evaporate. Transforming the call to a direct call for bonus points.

EG

class X
{
    public static int Main()
    {
        int y = 1;
        int[] a = new int[100];
        var f = (int x) => x + y;    // does not escape
        int sum = 0;

        foreach (int i in a)
        {
            sum += f(a[i]);
        }
        Console.WriteLine(sum);
        return sum;
    }
}