Correctly restore floating point context on x86 interop step-in scenarios

[tommcdon]

Fixes #117389
The X86 CONTEXT_FULL thread context flag does not include CONTEXT_FLOATING_POINT, while it is included on x64, arm32, arm64, as well as all other architectures defined in src\coreclr\debug\inc\dbgtargetcontext.h. Interop debugging uses a thread context save/restore mechanism, but was only saving CONTEXT_FULL, causing the i387 float registers to become corrupted on x86. This change sets the CONTEXT_FLOATING_POINTthread context flag so that we correct save and restore floating point numbers on x86.

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[Copilot]

Pull Request Overview

This PR ensures that the floating-point registers are correctly saved and restored on x86 interop step-in scenarios by including the CONTEXT_FLOATING_POINT flag wherever the thread context is captured.

• Add DT_CONTEXT_FLOATING_POINT to context flags in rsthread.cpp
• Include DT_CONTEXT_FLOATING_POINT in temp context in process.cpp
• Update DAC interop context capture in dacdbiimpl.cpp to include floating-point flags

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/coreclr/debug/di/rsthread.cpp	Include DT_CONTEXT_FLOATING_POINT when setting up thread contexts
src/coreclr/debug/di/process.cpp	Add DT_CONTEXT_FLOATING_POINT to temporary context for restore
src/coreclr/debug/daccess/dacdbiimpl.cpp	Pass CONTEXT_FLOATING_POINT (and extended registers) to DAC call

Comments suppressed due to low confidence (2)

src/coreclr/debug/di/rsthread.cpp:3709

• [nitpick] Consider adding a brief comment explaining why CONTEXT_FLOATING_POINT is now required on x86 to clarify the rationale for future maintainers.

    context.ContextFlags = DT_CONTEXT_FULL | DT_CONTEXT_FLOATING_POINT | DT_CONTEXT_EXTENDED_REGISTERS;

src/coreclr/debug/di/process.cpp:13284

• Add a unit or integration test that verifies floating-point register preservation on x86 interop step-in scenarios to guard against regressions.

            tempContext.ContextFlags = DT_CONTEXT_FULL | DT_CONTEXT_FLOATING_POINT | DT_CONTEXT_EXTENDED_REGISTERS;

[noahfalk]

👍

[tommcdon]

/ba-g failures are unrelated