[debugger] Support step into a tail call

[thaystg]

I got this test case:
https://github.com/dotnet/runtime/blob/80d8c46f071d9e3d8ede2d98cb2c918d9b0d7d31/src/tests/JIT/Regression/JitBlue/Runtime_39581/Runtime_39581.il
Added a breakpoint on line 93 and tried to step into to Runtime_39581.Program::Callee and it behaves like a step over.
With this change the step into works correctly.

Fixes#110441

[mikem8361]

I'm not an expert on this code but it looks good to me.

[tommcdon]

Is this intentionally part of this PR?

[thaystg]

This was causing a boring assertion in the debug build, I can open a separate PR with this fix but it can be here together.

[tommcdon]

I don't have a strong preference. Would we want to include that changes as part of a backport to .NET servicing?

[thaystg]

Ah, okay, I will remove it, it will be better for backporting only the change.

[tommcdon]

Very minor nit: this looks like a copy of the code in IsTailCallThatReturns, can we consolidate this into a shared function?

runtime/src/coreclr/debug/ee/controller.cpp

Lines 5642 to 5651 in ecefb5e

	TraceDestination trace;
	if (!g_pEEInterface->TraceStub(ip, &trace) || !g_pEEInterface->FollowTrace(&trace))
	{
	returnfalse;
	}
	MethodDesc* pTargetMD =
	trace.GetTraceType() == TRACE_UNJITTED_METHOD
	? trace.GetMethodDesc()
	: g_pEEInterface->GetNativeCodeMethodDesc(trace.GetAddress());

[tommcdon]

This looks good to me! Left a couple comments for your review.

[tommcdon]

LGTM, thanks!!

[thaystg]

/backport to release/9.0-staging

[github-actions]

Started backporting to release/9.0-staging: https://github.com/dotnet/runtime/actions/runs/12181390920

[thaystg]

/backport to release/8.0-staging

[github-actions]

Started backporting to release/8.0-staging: https://github.com/dotnet/runtime/actions/runs/12181421329

[github-actions]

@thaystg backporting to release/8.0-staging failed, the patch most likely resulted in conflicts:

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch
Applying: Support step into a tail call
.git/rebase-apply/patch:54: trailing whitespace.
case DB_IPCE_SET_ENABLE_CUSTOM_NOTIFICATION_RESULT: warning: 1 line adds whitespace errors.
Using index info to reconstruct a base tree...
M	src/coreclr/debug/ee/controller.cpp
M	src/coreclr/debug/shared/dbgtransportsession.cpp
Falling back to patching base and 3-way merge...
Auto-merging src/coreclr/debug/shared/dbgtransportsession.cpp
CONFLICT (content): Merge conflict in src/coreclr/debug/shared/dbgtransportsession.cpp
Auto-merging src/coreclr/debug/ee/controller.cpp
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config advice.mergeConflict false"
Patch failed at 0001 Support step into a tail call
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!

[thaystg]

/backport to release/8.0-staging

[thaystg]

/backport to release/9.0-staging

[github-actions]

Started backporting to release/8.0-staging: https://github.com/dotnet/runtime/actions/runs/12182141863

[github-actions]

Started backporting to release/9.0-staging: https://github.com/dotnet/runtime/actions/runs/12182142995