DXMT: keep indexed draw base vertex signed

[moreaki]

Summary

Keep indexed draw base vertex values signed across the DXMT/winemetal command boundary.

BaseVertexLocation is signed in D3D11, and Metal's indexed draw baseVertex argument is signed as well. This patch changes the stored command fields from uint32_t to int32_t so negative base vertex values are not reinterpreted as very large unsigned offsets.

Validation

• git diff --check
• Cherry-picked on top of DXMT: add LLVM build compatibility fixes #748 and built with kmk VBoxDxMt on macOS/Arm using LLVM 15.0.7.

Closes #754.

Signed-off-by: Roberto Nibali rnibali@gmail.com

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[moreaki]

DXMT v0.80 audit update:

This is already addressed in DXMT v0.80: the corresponding D3D11 indexed draw command state uses a signed int32_t base-vertex field. Updating the vendored DXMT tree to v0.80 would include the equivalent fix.

So this PR is best understood as a narrow backport for VirtualBox's currently vendored DXMT snapshot.