JIT: Add basic support for Swift reverse pinvokes #100018

jakobbotsch · 2024-03-20T14:14:48Z

Adds very rudimentary support for Swift reverse pinvokes. Since Swift function pointers are based on SwiftSelf also adds basic support for the SwiftSelf parameter. Structs are not supported yet, and neither is SwiftError.

Adds 10 simple tests just so that we have something. I'm going to regenerate these (and probably increase the number to 100) once we have the struct support.

The SwiftSelf parameter is not enregisterable because it is passed in a register that genFnPrologCalleeRegArgs does not handle. I have other plans to rewrite this function in the future (#99286 (comment)), so I didn't want to bother spending time on it here (it is not a trivial extension given how it works).

jakobbotsch · 2024-03-20T14:24:52Z

src/coreclr/jit/scopeinfo.cpp

-
-                        regType = compiler->GetEightByteType(structDesc, nCnt);
-#ifdef DEBUG
-                        regType = compiler->mangleVarArgsType(regType);
-                        assert(genMapRegNumToRegArgNum((nCnt == 0 ? regNum : otherRegNum), regType) != (unsigned)-1);
-#endif // DEBUG


I have removed this assert in a couple of places because I don't think it is asserting anything meaningful. The existence and mapping of genMapRegNumToRegArgNum is really an internal detail of how genFnPrologCalleeRegArgs works, and I expect to be able to remove it once that function is rewritten.

jakobbotsch · 2024-03-20T16:36:59Z

cc @dotnet/jit-contrib PTAL @amanasifkhalid

FYI @kotlarmilos @matouskozak @jkurdek

src/tests/Interop/Swift/SwiftCallbackAbiStress/SwiftCallbackAbiStress.cs

kotlarmilos · 2024-03-20T16:57:50Z

src/tests/Interop/Swift/SwiftCallbackAbiStress/SwiftCallbackAbiStress.cs

+        }
+        catch (Exception ex)
+        {
+            *(ExceptionDispatchInfo*)self.Value = ExceptionDispatchInfo.Capture(ex);


How does this get returned to the C# side?

The pinvokes in C# land are passing pointers to the ExceptionDispatchInfo as "self", and then check whether the it was set by this code after the return.

kotlarmilos · 2024-03-20T17:00:02Z

src/coreclr/jit/lclvars.cpp

+    if ((strcmp(className, "SwiftSelf") == 0) && (strcmp(namespaceName, "System.Runtime.InteropServices.Swift") == 0))
+    {
+        LclVarDsc* varDsc = varDscInfo->varDsc;
+        varDsc->SetArgReg(REG_SWIFT_SELF);


Does this mean that the reg value is loaded into the SwiftSelf argument?

The JIT can directly reference and use IL locals in its internal IR, and each of the parameter locals are marked with information about how they're passed (in a register or on stack). That's what the code here is doing.

It's ultimately up to the register allocator to decide what register every local is allocated into. For parameter locals LSRA will prefer to keep it in the same register that it was passed in, but it might also be allocated to another register (in which case a move from the initial register is needed in the prolog) or to stack (in which case a store to the stack frame is needed).

The PR here doesn't allow enregistering SwiftSelf so we will always end up keeping it on the stack frame. That's because the case where there are conflicts in the move graph is not yet handled for this register (e.g. we can have cases where the SwiftSelf register x20 needs to go to x0 and x0 needs to go to x20). It needs a bit of work but I was expecting to work on the relevant logic due to another issue, so I will handle both of these when I do that work.

Ok, thanks for info.

amanasifkhalid

LGTM, just a few comments. Thanks!

amanasifkhalid · 2024-03-20T16:50:31Z

src/tests/Interop/Swift/SwiftCallbackAbiStress/SwiftCallbackAbiStress.cs

+        }
+        catch (Exception ex)
+        {
+            *(ExceptionDispatchInfo*)self.Value = ExceptionDispatchInfo.Capture(ex);


Once SwiftError works with reverse Pinvoke, I assume we're going to update this error handling to use the SwiftError arg instead, right?

Yeah, I think that would make sense.

Although handling it through SwiftError will require allocating a GCHandle, so the current approach will probably end up being simpler.

amanasifkhalid · 2024-03-20T16:51:20Z

src/tests/Interop/Swift/SwiftCallbackAbiStress/SwiftCallbackAbiStress.cs

@@ -0,0 +1,482 @@
+#pragma warning disable CS8500


Do we need the // Licensed to the .NET Foundation under one or more agreements. header comments at the top of these new files?

Good catch, I should add those.

I think some of the other interop tests like SwiftAbiStress are missing it too, but feel free to address that in a follow-up PR.

amanasifkhalid · 2024-03-20T17:01:45Z

src/coreclr/jit/compiler.h

@@ -3859,6 +3859,7 @@ class Compiler
    // mechanism passes the address of the return address to a runtime helper
    // where it is used to detect tail-call chains.
    unsigned lvaRetAddrVar;
+    unsigned lvaSwiftSelfArg;


Since all the places where we check lvaSwiftSelfArg are under #ifdef SWIFT_SUPPORT, should we ifdef this, and where we initialize it in Compiler::lvaInit?

Yeah, I'll do that.

amanasifkhalid · 2024-03-20T17:06:39Z

src/coreclr/jit/compiler.h

@@ -3982,6 +3983,8 @@ class Compiler
                       CORINFO_ARG_LIST_HANDLE varList,
                       CORINFO_SIG_INFO*       varSig);

+    bool lvaInitSpecialSwiftParam(InitVarDscInfo* varDscInfo, CorInfoType type, CORINFO_CLASS_HANDLE typeHnd);


Based on the naming of this method, I guess we'll be using this to do the SwiftError* type lookup too...

Yeah, I was thinking that same logic could live here.

amanasifkhalid · 2024-03-20T17:07:13Z

src/coreclr/jit/codegencommon.cpp

@@ -6131,6 +6143,14 @@ void CodeGen::genFnProlog()
        intRegState.rsCalleeRegArgMaskLiveIn &= ~RBM_SECRET_STUB_PARAM;
    }

+#ifdef SWIFT_SUPPORT
+    if ((compiler->lvaSwiftSelfArg != BAD_VAR_NUM) && ((intRegState.rsCalleeRegArgMaskLiveIn & RBM_SWIFT_SELF) != 0))


Are there situations where lvaSwiftSelfArg is valid, but the reg mask doesn't include the Swift self reg? If not, maybe we should assert that the reg mask includes it if lvaSwiftSelfArg is set.

Yes, if lvaSwiftSelfArg is dead on entry then it shouldn't be in the live-in set.

amanasifkhalid · 2024-03-20T17:24:23Z

It might be a good idea to run jitstressregs (or a similar pipeline) on this PR

jakobbotsch · 2024-03-20T17:53:11Z

/azp run runtime-coreclr jitstress, runtime-coreclr jitstressregs, runtime-coreclr jitstress2-jitstressregs

azure-pipelines · 2024-03-20T17:53:35Z

Azure Pipelines successfully started running 3 pipeline(s).

amanasifkhalid · 2024-03-20T20:08:32Z

Looks like jitstressregs is failing with the assert genRegMask(argDsc->GetArgReg()) & (RBM_ARG_REGS) in lsrabuild.cpp (log)

jakobbotsch · 2024-03-21T11:37:28Z

Looks like jitstressregs is failing with the assert genRegMask(argDsc->GetArgReg()) & (RBM_ARG_REGS) in lsrabuild.cpp (log)

Pushed some commits to fix this and address the rest of the feedback.

jakobbotsch · 2024-03-21T12:37:56Z

/azp run runtime-coreclr jitstress, runtime-coreclr jitstressregs, runtime-coreclr jitstress2-jitstressregs

azure-pipelines · 2024-03-21T12:38:13Z

Azure Pipelines successfully started running 3 pipeline(s).

jakobbotsch · 2024-03-21T17:10:52Z

Failures are #100035, #99810, #100047

jakobbotsch added 11 commits March 19, 2024 13:11

Add test

9a9a052

Support SwiftSelf

bfd4e28

Backend handling

53d00a6

Fix arm64 build

ea5c172

Add missing handling of DNER reason

4fd5964

Fix assert

ea32187

Fix build

e01d190

Remove some unnecessarily aggressive asserts

40d998a

Expand assert

4c64049

Reduce tests

7d43f3c

Disable tests on Mono

49826a8

dotnet-issue-labeler bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label Mar 20, 2024

dotnet-policy-service bot assigned jakobbotsch Mar 20, 2024

Regenerate tests

d65c4c3

jakobbotsch commented Mar 20, 2024

View reviewed changes

jakobbotsch marked this pull request as ready for review March 20, 2024 16:36

jakobbotsch requested a review from amanasifkhalid March 20, 2024 16:37

kotlarmilos reviewed Mar 20, 2024

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amanasifkhalid approved these changes Mar 20, 2024

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build-analysis bot mentioned this pull request Mar 20, 2024

Tracking issue for CI build timeouts #76454

Closed

jakobbotsch added 3 commits March 21, 2024 12:19

Factor int parameter register validation

3e76803

Add missing license headers

21d1c52

More feedback

b4b73d7

Run jit-format

cb44f0b

This was referenced Mar 21, 2024

Assert failure(PID 13812 [0x000035f4], Thread: 14128 [0x3730]): promoted_bytes (heap_number) == promoted #100035

Closed

"error: out of range pc-relative fixup value" on linux-armel checked CoreCLR_NonPortable #100047

Closed

jakobbotsch merged commit de774ff into dotnet:main Mar 21, 2024
159 of 170 checks passed

jakobbotsch deleted the swift-reverse-pinvoke branch March 21, 2024 17:12

jkoritzinsky mentioned this pull request Mar 21, 2024

Runtime support for Swift Interop in .NET 9 #93631

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JIT: Add basic support for Swift reverse pinvokes #100018

JIT: Add basic support for Swift reverse pinvokes #100018

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