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Fix interpreter passing managed "this" in presence of return buffer - #117661
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The CallStubGenerator is using the native x64 Windows calling convention for the case when both "this" and "return buffer" arguments are passed to native callees. However, the CLR ABI diverges from this convention. While the native one passes the return buffer first and the this pointer second, the CLR ABI always passes the "this" pointer first. This fixes a number of failures on the runtime startup path when running interpreted.
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Tagging subscribers to this area: @BrzVlad, @janvorli, @kg |
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Pull Request Overview
This PR updates the CallStubGenerator to use the CLR ABI ordering for the this pointer when a return buffer is present, ensuring this is always passed in the first argument register rather than following the native Windows x64 convention.
- Removes the special-case Windows/AMD64 branch that swapped the registers when a return buffer was present.
- Always sets
m_r1to 0 for thethispointer under the CLR ABI. - Updates the comment to clarify the CLR ABI behavior.
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kg
approved these changes
Jul 15, 2025
This was referenced Jul 15, 2025
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janvorli
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Jul 16, 2025
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/ba-g the Android build timeouts are a known issue |
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The CallStubGenerator is using the native x64 Windows calling convention for the case when both "this" and "return buffer" arguments are passed to native callees. However, the CLR ABI diverges from this convention. While the native one passes the return buffer first and the this pointer second, the CLR ABI always passes the "this" pointer first.
This fixes a number of failures on the runtime startup path when running interpreted.