JIT: Support loading Swift self register from SwiftSelf struct

[amanasifkhalid]

Adds JIT support for loading the Swift self/context register value from the SwiftSelf struct argument passed to a Swift call. Also enables corresponding tests.

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Issue Details

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Adds JIT support for loading the Swift self/context register value from the SwiftSelf struct argument passed to a Swift call. Also enables corresponding tests.

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

[amanasifkhalid]

cc @jakobbotsch @kotlarmilos @jkoritzinsky. Here's a snippet of what the codegen looks like on x64, where the self register is r13:

       mov      r13, qword ptr [rbp-0x48]
       mov      rax, 0x7FF8FF2F59B8      ; function address
       mov      qword ptr [rbp-0x90], rax
       lea      rax, G_M44653_IG07
       mov      qword ptr [rbp-0x78], rax
       mov      rax, qword ptr [rbp-0x58]
       lea      rcx, bword ptr [rbp-0xA0]
       mov      qword ptr [rax+0x10], rcx
       mov      rax, qword ptr [rbp-0x58]
       mov      byte  ptr [rax+0x0C], 0
       call     [SelfContextTests:getMagicNumber(System.Runtime.InteropServices.Swift.SwiftSelf):long]

And on arm64, where the self register is x20:

            ldr     x20, [fp, #0x80]	// [V01 loc1]
            movz    x0, #0x4988
            movk    x0, #0x2103 LSL #16
            movk    x0, #0x7FF9 LSL #32
            str     x0, [fp, #0x30]	// [V05 PInvokeFrame+0x18]
            adr     x0, [G_M44653_IG09]
            str     x0, [fp, #0x48]	// [V05 PInvokeFrame+0x30]
            ldr     x0, [fp, #0x70]	// [V04 FramesRoot]
            add     x1, fp, #32	// [V05 PInvokeFrame+0x08]
            str     x1, [x0, #0x10]
            ldr     x0, [fp, #0x70]	// [V04 FramesRoot]
            strb    wzr, [x0, #0x0C]
            movz    x0, #0x49C8      // code for SelfContextTests:getMagicNumber(System.Runtime.InteropServices.Swift.SwiftSelf):long
            movk    x0, #0x2103 LSL #16
            movk    x0, #0x7FF9 LSL #32
            ldr     x0, [x0]
            blr     x0

[jakobbotsch]

Why is this necessary? That doesn't seem right.

[jakobbotsch]

Likely we should instead insert a new arg in the importer that represents "self" as a primitive instead of keeping this as a struct argument. It being a struct argument is just an artifact of the design and it wouldn't work to keep it as a struct on all ABIs.

[jakobbotsch]

Let's just keep it as is for now. I'm refactoring stuff for the struct work which should make this change simple to make.

[amanasifkhalid]

Likely we should instead insert a new arg in the importer that represents "self" as a primitive instead of keeping this as a struct argument.

Yeah, the fact that the argument was being kept as TYP_STRUCT was causing asserts in later phases.

Let's just keep it as is for now. I'm refactoring stuff for the struct work which should make this change simple to make.

Sure thing.

[jakobbotsch]

Why this change? (Seems fine, just curious)

[amanasifkhalid]

CallArg::m_wellKnownArg is 5 bits, and WellKnownArg::SwiftSelf has a value of 16 (also 5 bits). If m_wellKnownArg is signed, then we lose the most-significant bit, so comparisons like m_wellKnownArg == WellKnownArg::SwiftSelf fail.

[amanasifkhalid]

ryujit-bot doesn't seem to be running, so I'll point out here that this is a no-diff change.